ALBERT

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Progress in Oceanography, Volume 170〈/p〉 〈p〉Author(s): Alba María Martínez–Pérez, Teresa S. Catalá, Mar Nieto–Cid, Jaime Otero, Marta Álvarez, Mikhail Emelianov, Isabel Reche, Xosé Antón Álvarez–Salgado, Javier Arístegui〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fluorescent dissolved organic matter (FDOM) in the Mediterranean Sea was analysed by excitation–emission matrix (EEM) spectroscopy and parallel factor (PARAFAC) analysis during the cruise HOTMIX 2014. A 4–component model, including 3 humic–like and 1 protein–like compounds, was obtained. To decipher the environmental factors that dictate the distributions of these components, we run generalized additive models (GAMs) in the epipelagic layer and an optimum multiparametric (OMP) water masses analysis in the meso– and bathypelagic layers. In the epipelagic layer, apparent oxygen utilization (AOU) and temperature presented the most significant effects on the variability of the marine humic-like peak M fluorescence, suggesting that its distribution was controlled by the net community respiration of organic matter and photobleaching. On the contrary, the variability of the soil humic-like peak E and the protein–like peak T fluorescence was explained mainly by the prokaryotic heterotrophic abundance, which decreased eastwards. In the meso– and bathypelagic layers, water mass mixing and basin–scale mineralization processes explained 〉72% and 63% of the humic–like and protein–like fluorescence variability, respectively. When analysing the two basins separately, the OMP model offered a better explanation of the distribution of fluorescence in the eastern Mediterranean Sea, as expected from the reduced biological activity in this ultra–oligotrophic basin. Furthermore, while western Mediterranean deep waters display the usual trend in the global ocean (increase of humic–like fluorescence and decrease of protein–like fluorescence with higher AOU values), the eastern Mediterranean deep waters presented an opposite trend. Different initial fluorescence intensities of the water masses that mix in the eastern basin, with Adriatic and Aegean origins, seem to be behind this contrasting pattern. The analysis of the transect–scale mineralization processes corroborate this hypothesis, suggesting a production of humic–like and a consumption of protein–like fluorescence in parallel with water mass ageing. Remarkably, the transect–scale variability of the chromophoric dissolved organic matter (CDOM) absorbing at the excitation wavelength of the humic–like peak M indicates an unexpected loss with increasing AOU, which suggests that the consumption of the non–fluorescent fraction of CDOM absorbing at that wavelength exceeded the production of the fluorescent fraction observed here.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Comptes Rendus Geoscience, Volume 350, Issue 7〈/p〉 〈p〉Author(s): Ilias Fountoulakis, Christos S. Zerefos, Alkiviadis F. Bais, John Kapsomenakis, Maria-Elissavet Koukouli, Nozomu Ohkawara, Vitali Fioletov, Hugo De Backer, Kaisa Lakkala, Tomi Karppinen, Ann R. Webb〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spectral UV records of solar irradiance at stations over Europe, Canada, and Japan were used to study long-term trends at 307.5 nm for a 25-year period, from 1992 to 2016. Ground-based measurements of total ozone, as well as satellite measurements of the Aerosol Index, the Total Cloud Cover and the surface reflectivity were also used in order to attribute the estimated changes of the UV to the corresponding changes of these factors. The present study shows that over the Northern Hemisphere, the long-term changes in UV-B radiation reaching the Earth's surface vary significantly over different locations, and that the main drivers of these variations are changes in aerosols and total ozone. At high latitudes, part of the observed changes may also be attributed to changes in the surface reflectivity. Over Japan, the UV-B irradiance at 307.5 nm has increased significantly by ∼3%/decade during the past 25 years, possibly due to the corresponding significant decrease of its absorption by aerosols. It was found that the greatest part of this increase took place before the mid-2000s. The only European station, over which UV radiation increases significantly, is that of Thessaloniki, Greece. Analysis of the clear-sky irradiance for the particular station shows increasing irradiance at 307.5 nm by ∼3.5%/decade during the entire period of study, with an increasing rate of change during the last decade, possibly again due to the decreasing absorption by aerosols.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Solid Earth Sciences, Volume 3, Issue 4〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 173〈/p〉 〈p〉Author(s): Yixiang Zhang, Jianming He, Xiao Li, Chong Lin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hydraulic fracturing using freshwater as fracturing fluid is regularly employed in commercial shale gas or oil production. Many problems are brought by the fracturing fluid of water, such as water shortages, swelling of clay mineral, and the pollution of flow-back water. Replacement of water by supercritical CO〈sub〉2〈/sub〉 (SC〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉CO〈sub〉2〈/sub〉) in the hydraulic fracturing treatment of shale reservoir has meaningful potential for the improvement of gas production. Hydraulic fracturing experiments, under different injection rate and stress state, were carried out for studying the SC-CO〈sub〉2〈/sub〉 fracturing of shale considering anisotropy effects. Anisotropy of shale has a significant impact on the mechanical behavior and fracture propagation of shale in the experiment. There shows a downward tendency for breakdown pressure with the increase of bedding plane angle in general. Higher injection rate can lead to the higher breakdown pressure, while higher deviator stress can lead to the lower breakdown pressure instead. In addition, three patterns of fracture propagation can be observed in the experiment, relative to the bedding structures of shale specimen, including propagating along, propagating across and arresting. The maximum values of fracture width during experiment in shale with different bedding plane angle ranges from 0.29 mm to 1.05 mm, while the final fracture width after the fracturing experiment is kept within the range of 0.01 mm–0.04 mm under the injection rate of 0.3 ml/s.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Petroleum Science and Engineering, Volume 173〈/p〉 〈p〉Author(s): Xueying Wang, Hongjian Ni, Ruihe Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Toolface control is an important issue when drilling directional wells with steerable motors. In this paper, a new experimental apparatus has been built to study the toolface behavior while slide drilling. In experiments, weight on bit and toolface orientation during the simulated slide drilling are recorded and analyzed. Experimental results indicate that axial stick-slip motion of the drillstring that occurs in the presence of large friction causes toolface disorientation. In addition, the phenomenon of toolface hysteresis in horizontal wells is identified. The asymmetric loading and unloading rates of weight on bit result in toolface hysteresis, and toolface hysteresis worsens toolface disorientation. A new method of correcting toolface by quickly eliminating toolface hysteresis is proposed. Four torque-related parameters are used in the method, and each has a specific implication. The proposed method has been examined using the experimental apparatus and has been proven to work. The experimental results and related analysis in this paper can help to further improve the efficiency of toolface control during slide drilling.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 3 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 International Journal of Sediment Research〈/p〉 〈p〉Author(s): Pil Jae Kim, Jong Hyeon Lee, In Ae Huh, DongSoo Kong〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Sediment quality has been evaluated in a variety of ways since the early 1990s in studies from Europe. In South Korea, most studies have used an indicator value for benthic macroinvertebrates based on water quality, not sediment quality. To date, few studies have examined the biological integrity of benthic macroinvertebrate communities in South Korea. In the current study, the tolerance valency and value in samples and the indicator weight values were measured for 43 benthic macroinvertebrate taxa from 73 sampling units in South Korea from 2014 to 2016. Total organic carbon, the amount of heavy metals, and total ammonia nitrogen were analyzed. The average grade for each pollutant was used as the sediment quality index. A benthic macroinvertebrates sediment index was developed for bioassessment of freshwater sediment. The benthic macroinvertebrates sediment index, which is based on the relative frequency of occurrence of macroinvertebrates, was highly correlated with pollution levels in the sediment. This index can be used in the field to assess the contamination of freshwater sediment. As the sample size was small in the current study and there were taxonomic limitations of Chironomidae larvae, further research is needed to improve the reliability of the benthic macroinvertebrates sediment index.〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 143〈/p〉 〈p〉Author(s): Yi Ren, Fang Cheng, Xiaoying Zhou, Kai Chang, Guanghui Zhou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Two-dimensional (2D) polyaniline with C〈sub〉3〈/sub〉N stoichiometry, is a newly fabricated layered material that has been expected to possess fascinating electronic, thermal, mechanical and chemical properties. The nature of its counterpart nanoribbons offering even more tunability in properties because of the unique quantum confinement and edge effect, however, has not been revealed yet. Here we systemically study the mechanical, electronic and magnetic properties for various nanoribbons cutting from a monolayer C〈sub〉3〈/sub〉N sheet along the typical crystallographic orientations. By the first-principles calculations we find that C〈sub〉3〈/sub〉N nanoribbons exhibit sensitive responses to the externally applied electric field and strain. Specifically, the spin-selective half-metallicity depends on the external electric field or strain, as well as the ribbon width. For the asymmetric zigzag-edged ribbon, the spin-polarization rate approaches −100% at electric field strength −0.2 V/Å. Interestingly, an applied strain can transform a symmetric zigzag-carbon-edge ribbon from a magnetic semiconductor to a half-metal. And the half-metal property remains unchanged when the strain increases from 8 to 15%, while the spin-up subband gap further increases to 0.46 eV. These numerical results may be useful to engineer and design magnetic-field-free spintronic devices based on the 2D C〈sub〉3〈/sub〉N.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318309333-fx1.jpg" width="256" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 142〈/p〉 〈p〉Author(s): Sivabrata Sahu, Mihir Ranjan Sahoo, Anoop Kumar Kushwaha, G.C. Rout, S.K. Nayak〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have investigated here, the electronic and magnetic properties of graphene–nickel system by tight-binding mean-field approach. Strong hybridization between the 2p〈sub〉z〈/sub〉 orbital of graphene and 3d〈sub〉z2〈/sub〉 orbital of nickel occurs when monolayer graphene is placed over a single layer of ferromagnetically ordered Ni (111) metal due to the excellent lattice matching between the two layers. This hybridization greatly affects the electronic and magnetic properties of the bilayer system, resulting in a significantly reduced local magnetic moment of the nickel layer and an enhanced induced spin polarization on the graphene layer. The calculated Hamiltonian revealed critical information regarding the first-, second-and third-nearest-neighbour hopping integrals of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈mi〉π〈/mi〉〈mo〉−〈/mo〉〈/mrow〉〈/math〉 electrons of graphene besides the Coulomb correlation of electrons in nickel (111). The Hubbard type Coulomb interactions present in nickel lattices were treated within the mean-field approximation. Zubarev's technique was employed to calculate electronic Green's functions and subsequent investigation of the temperature dependent ferromagnetic magnetization of nickel (111)was carried out through self-consistent calculation. Further calculations regarding the induced magnetization in the graphene, total magnetization in bilayer layer system, electronic band dispersion, spin resolved density of states (DOS) and spin polarization efficiency have been carried out. The results were corroborated by experimental observations.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318309977-egi10LZ69G4T53.jpg" width="283" alt="Image" title="Image"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 143〈/p〉 〈p〉Author(s): Lihua Lin, Hongzhe Pan, Yanhuan Chen, Xiaoying Song, Jun Xu, Huibiao Liu, Shaolong Tang, Youwei Du, Nujiang Tang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pristine graphdiyne (pGDY) with high quality was prepared by annealing as-prepared GDY in hydrogen, and its stacking style, bandgap and magnetism were studied. The results show that pGDY is ABC-stacked, has a direct bandgap of ca. 0.64 eV, and shows spin-half paramagnetism at 2 K which may result from the residual hydroxyl groups on the chains of GDY sheet. The hybrid functional calculations show that ABC-stacked GDY is a semiconductor with a direct bandgap of 0.73 eV and is intrinsically nonmagnetic.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318309126-fx1.jpg" width="350" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 143〈/p〉 〈p〉Author(s): A. Yadav, M. Yadav, S. Gupta, Y. Popat, A. Gangan, B. Chakraborty, L.M. Ramaniah, R. Fernandes, A. Miotello, M.R. Press, N. Patel〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Reduced graphene oxide (rGO)〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉TiO〈sub〉2〈/sub〉 composites are prepared using photo-reduction method by varying GO to TiO〈sub〉2〈/sub〉 weight ratio from low (rGOT-0.001, 0.01, & 0.1) to high (rGOT-1, 3 & 10) range and its effect on morphological, optical and mechanism of fast charge dynamics at the interface are investigated. Experimental analysis confirm that reduction process improves as TiO〈sub〉2〈/sub〉 amount increases in rGO-TiO〈sub〉2〈/sub〉 but leads to aggregation of TiO〈sub〉2〈/sub〉 nanoparticles. rGOT-3 composite displayed the highest photocatalytic activity for degradation of phenols compared to TiO〈sub〉2〈/sub〉, GO and other composites. This was achieved due to uniform dispersion of TiO〈sub〉2〈/sub〉 nanoparticles over rGO surface, which enables distinct formation of Ti〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉C bond between each TiO〈sub〉2〈/sub〉 nanoparticle and rGO surface, and results in slight red shift in the band edge. This Ti〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉C bond facilitates fast electron transfer from TiO〈sub〉2〈/sub〉 to rGO and reduces recombination rate as revealed by photoluminescence and time resolved photoluminescence spectroscopy. The experimental findings were further investigated using density functional theory simulations. Band structure calculation confirms high mobility states induced within the band gap due to formation of Ti〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉O〈img src="https://sdfestaticassets-eu-west-1.sciencedirectassets.com/shared-assets/16/entities/sbnd"〉C bond in rGO-TiO〈sub〉2〈/sub〉 model which assists in fast electron transfer from TiO〈sub〉2〈/sub〉 to rGO during the photocatalytic process and hence reduces recombination rate.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318310091-fx1.jpg" width="477" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 143〈/p〉 〈p〉Author(s): Rebecca F. Albers, Rafael A. Bini, João B. Souza, Derik T. Machado, Laudemir C. Varanda〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉There is great interest in new materials that synergistically combine properties of reduced graphene oxide (rGO) with nanoparticles (NP) generating rGO-nanoparticles hybrid materials (NPHM). Based on the modified polyol process (MPP), we developed a new and versatile method to synthesize rGO and rGO-NPHM in one-pot route. rGO sheets with small defects number were reduced from graphene oxide by the MPP, and experimental parameters were varied to evaluate the method robustness, and adjusted to prepare rGO-NPHM, for instance, rGO/Au, rGO/Ag, rGO/CdSe, rGO/FePt and rGO/Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉 inferring the versatility of our methodology. NPHM were evaluated by X-ray diffraction, transmission electron microscopy, vibrating sample magnetometry, and Raman, UV–Vis, and FTIR spectroscopies. All synthesized NPHM shown size-controlled monodisperse-like NP homogeneously distributed onto the rGO sheets, except for the Ag-NP where a bimodal size distribution was observed. Plasmon (rGO/Au and rGO/Ag) and typical absorption and emission (rGO/CdSe) by UV–Vis, whereas paramagnetic-like (rGO/FePt) and superparamagnetic (rGO/Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉) behavior was observed by the magnetic NPHM. The MPP is already efficient for NP preparation and here, we showed that its might successful for rGO and rGO-NPHM synthesis in a simple and versatile one-pot route, which can be scaled up to allow mass production and easily tuned for other NP kinds.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318310066-fx1.jpg" width="404" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 142〈/p〉 〈p〉Author(s): Yaochen Song, Jiaxuan Liao, Cheng Chen, Jian Yang, Jinchen Chen, Feng Gong, Sizhe Wang, Ziqiang Xu, Mengqiang Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Self-assembled nano-honeycomb WS〈sub〉2〈/sub〉 modified by graphene doping were prepared by improved one step hydrothermal method. In this hybrid structure, graphene plays a key role of transferring the morphology from the nanowire microporous spheres to graphene-supported nano-honeycomb plane structure, which has the larger the specific surface area and higher conductivity. This anode delivers the superb electrochemical performances of lithium/sodium ion batteries with high specific charge capacity (953.1/522.3 mAh·g〈sup〉−1〈/sup〉 at 0.1 A·g〈sup〉−1〈/sup〉), long cycling life (more than 350/200 cycles at 1 A·g〈sup〉−1〈/sup〉), and high charge/discharge rates (up to 10/5 A·g〈sup〉−1〈/sup〉). This nano-honeycomb structure WS〈sub〉2〈/sub〉 composite anode with facile hydrothermal process, as well as superb electrochemical performances, makes it attractive for the potential applications in lithium/sodium ion batteries.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318307103-fx1.jpg" width="299" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 143〈/p〉 〈p〉Author(s): Ll.M. Evans, L. Margetts, P.D. Lee, C.A.M. Butler, E. Surrey〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Functional materials' properties are influenced by microstructures which can be changed during manufacturing. A technique is presented which digitises graphite foam via X-ray tomography and converts it into image-based models to determine properties in silico. By simulating a laser flash analysis its effective thermal conductivity is predicted. Results show ∼1% error in the direction the foam was ‘grown’ during manufacturing but is significantly less accurate in plane due to effective thermal conductivity resulting from both the foam's microstructure and graphite's crystalline structure. An empirical relationship is found linking these by using a law of mixtures. A case study is presented demonstrating the technique's use to simulate a heat exchanger component containing graphite foam with micro-scale accuracy using literature material properties for solid graphite. Compared against conventional finite element modelling there is no requirement to firstly experimentally measure the foam's effective bulk properties. Additionally, improved local accuracy is achieved due to exact location of contact between the foam and other parts of the component. This capability will be of interest in design and manufacture of components using graphite materials. The software used was developed by the authors and is open source for others to undertake similar studies.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318309461-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 143〈/p〉 〈p〉Author(s): Ke Chu, Jing Wang, Ya-ping Liu, Yuan-bo Li, Cheng-chang Jia, Hu Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In-situ formation of appropriate interfacial carbides by matrix-alloying with carbide-forming elements offers an efficient approach to improve the interfacial bonding of graphene/CuX composites. However, the carbide formation commonly occurs at graphene edge/matrix interface, which is not enough to achieve the sufficient interfacial bonding because the vast majority of graphene/matrix interface is basal-plane/matrix interface rather than edge/matrix interface. To alleviate this limitation, we reported a new design of 〈em〉creating defects on graphene basal-plane〈/em〉 (CDGB) to optimize the interface and mechanical properties of graphene/CuCr composites. Plasma treatment was employed to create the structural defects (∼7 nm nanopores) on graphene basal-plane. When incorporating the plasma-treated graphene into the CuCr matrix, the Cr〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 carbides were found to be in-situ formed at both basal-plane/matrix and edge/matrix interfaces. Ex-situ and in-situ tensile tests both demonstrated that the plasma-treated graphene led to the composite that showed a larger strength enhancement and a higher load transfer capability than untreated counterpart, which was ascribed to the largely improved interfacial bonding contributed by the Cr〈sub〉7〈/sub〉C〈sub〉3〈/sub〉 formed at basal-plane/matrix interface. This study suggests that the CDBG via plasma treatment affords a feasible solution for the interface optimization of graphene/CuX composites with enhanced mechanical properties.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318310145-fx1.jpg" width="477" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 142〈/p〉 〈p〉Author(s): Dalsu Choi, Hyun-Sig Kil, Sungho Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recently restricted greenhouse gas emission regulations for commercial vehicles have initiated a significant interest of an automotive industry in carbon fibers (CFs), which are excellent lightweight structural materials. However, the high production cost of CFs has limited their use in a selected number of applications including military, aircraft, and aerospace industries. Therefore, to satisfy a huge demand from the automotive industry and to translate an exotic technology into commercial applications, tremendous research efforts have focused on developing low-cost CFs. As the precursor cost takes more than 50% of an entire cost for CFs production, adopting low-cost precursors for CFs have been utilized as one of the main strategies. In this article, we review series of previous achievements which incorporated low-cost precursors into CFs fabrication including novel acrylic polymers, polyethylene (PE), lignin, and pitch. Furthermore, looking toward the future, prospective processing technologies which might be beneficial for reducing manufacturing cost of CFs are also reviewed.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318309436-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 17 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon〈/p〉 〈p〉Author(s): Paolo Restuccia, M.C. Righi〈/p〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences, Volume 169〈/p〉 〈p〉Author(s): Liming Wen, José Badal, Jiafu Hu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉P receiver functions (PRFs) and the 〈em〉H-k〈/em〉 stacking technique are tools often used to constrain the thickness of the crust and the ratio between the velocities of P and S waves. Both the crustal depth and the Poisson's ratio are very important parameters to study the tectonic evolution of the lithosphere, but they can be significantly affected by the presence of crustal anisotropy. In order to address this problem, we have extended the isotropic stacking approach to include six converted P-to-S phases that are generated in the anisotropic case, instead of only three phases considered in the isotropic case, and we have examined the feasibility of the stacking technique using synthetic and real data. Based on PRFs acquired by 108 permanent broadband seismic stations deployed in the southeastern margin of Tibet including the Sichuan and Yunnan areas, we have applied the anisotropic 〈em〉H-k〈/em〉 stacking scheme to investigate the crustal thickness and Poisson’s ratio. The results reveal that the crustal thickness varies from ∼60 km in the Songpan-Ganzi fold system and the northern part of the Sichuan-Yunnan diamond-shaped block, near the Eastern Himalayan Syntaxis, to ∼33 km in southern Yunnan, and that the Poisson’s ratio varies mostly from 0.24 to 0.32. The highest values of 0.28–0.30 are found along the axis formed by the Longmenshan fault, the Lijiang-Jinhe fault and the Xiaojiang fault, and are attributed to the accumulation of lower crustal flow in front of the Sichuan Basin. The highest value of ∼0.32 is observed at the Tengchong volcano area to the north of the Indochina block, and is attributed to the upwelling of hot mantle associated to the eastward subduction of the Indian plate, rather than to the expansion of east Tibet. Comparing with the results provided by the isotropic stacking scheme, it is appreciated that the crustal depth determined by the anisotropic stacking method well adjusts the observed pattern of gravity anomaly. We conclude that the results obtained by anisotropic stacking yield a much better constraint on the estimation of the crustal depth and Poisson's ratio when compared to those achieved by isotropic stacking.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302979-fx1.jpg" width="333" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Lithos, Volumes 324–325〈/p〉 〈p〉Author(s): R. Johannes Giebel, Michael A.W. Marks, Christoph D.K. Gauert, Gregor Markl〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉A detailed electron microprobe study has been carried out on the compositional variations of mica and apatite from carbonatites, phoscorites and associated pyroxenites (and fenites) of the Loolekop deposit, Palabora Carbonatite Complex (South Africa). Mica in pyroxenites and fenites is Mg-rich biotite, whilst micas in carbonatites and phoscorites are compositionally diverse including phlogopite, Ba-rich phlogopite (up to 30% kinoshitalite component), 〈sup〉IV〈/sup〉Al-rich phlogopite (up to 30% eastonite component) and tetraferriphlogopite. The various types of phlogopites are interpreted as orthomagmatic phases, whereas tetraferriphlogopite precipitation was a late-magmatic to hydrothermal process that additionally introduced REE into the system. Orthomagmatic apatite is generally REE- and Sr-poor fluorapatite and does not show large compositional differences between rock types. Apatite associated with the late-stage tetraferriphlogopite mineralization reaches higher levels of REE (up to 4.9 wt%), Si (up to 1.5 wt% SiO〈sub〉2〈/sub〉), Sr (up to 2.6 wt% SrO) and Na (up to 1.0 wt% Na〈sub〉2〈/sub〉O).〈/p〉 〈p〉The compositional variation of micas and apatites, which is affiliated with distinct rock types, reflects the multi-stage evolution of the Loolekop deposit and provides detailed insight into the relationships of the carbonatite-phoscorite assemblage. The obtained data support the separation of phoscorite and carbonatite by immiscibility from a common parental magma, which may happen due to a decrease of temperature and/or pressure during the ascent of the magma. This results in a density contrast between the carbonatitic and phoscoritic components that will lead to descending phoscorite accumulations at the outer zones of the magma channel and a jet-like ascent (further promoted by its extremely low viscosity) of the carbonatite magma. The genetic model deduced here explains the peculiar association of carbonatites, phoscorites and silicate rocks in many alkaline complexes worldwide.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Carbon, Volume 142〈/p〉 〈p〉Author(s): Baoyin Jin, Ding-Bang Xiong, Zhanqiu Tan, Genlian Fan, Qiang Guo, Yishi Su, Zhiqiang Li, Di Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Corrosion protection of metals is of great importance due to their widespread use. Graphene (Gr) has shown promising corrosion resistance as a coating for metals, however, its excellent strengthening effect that has been widely shown is suppressed in such coating applications. Here, inspired by positive anti-corrosion role of graphene coating for metal macro-foils, graphene encapsulated Cu (Cu@Gr) micro-/nano-flakes are designed and fabricated, and then used as building blocks for assembling bulk Gr/Cu composites. Thanks to its protective role and strengthening effect of uniformly dispersed graphene in Cu matrix, as compared to bare copper, corrosion rate of the as-fabricated bulk Gr/Cu composites is reduced by 50% in NaCl solution and its yield strength is increased by ∼180% (2.5 vol% Gr) simultaneously, without deterioration on electrical conductivity. The anti-corrosion mechanisms are understood by studying etching behavior of the Cu@Gr flakes in FeCl〈sub〉3〈/sub〉 solution, and surface morphology evolution in the samples subjected to salt spray corrosion, and electrochemical corrosion tests. Graphene's anti-corrosion effect is also reflected by an anisotropic corrosion behavior of the Gr/Cu composite because of a “brick-and-mortar” microstructure. The results presented here shed light on expanding metal matrix composite's applications to a wider range and more complex situation by incorporating graphene.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0008622318310078-fx1.jpg" width="239" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Biology and Biochemistry, Volume 128〈/p〉 〈p〉Author(s): J.M. Kranabetter〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Forest floor carbon (C) sequestration has been negatively correlated with manganese (Mn) availability, possibly due to reduced efficacy of Mn-peridoxase enzymes produced by Agaricomycete fungi. I examined a soil C and Mn dataset from a podzolization gradient, along with fungal sporocarp Mn concentrations, to potentially corroborate this finding. An inverse power relationship between soil C and soil Mn content across temperate rainforests was confirmed, which provides further evidence of a Mn bottleneck in C turnover. Average Mn concentrations of saprotrophic sporocarps were greater than those of ectomycorrhizal fungi, and displayed a similar inverse correlation with increasing soil C. The absence or limited effectiveness of select saprotrophic fungi across Mn-depleted forest soils may be one mechanism behind impeded turnover of recalcitrant organic matter.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Biology and Biochemistry, Volume 128〈/p〉 〈p〉Author(s): Charles R. Warren〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Phospholipids are isolated from crude lipid extracts by silica solid phase extraction (SPE), but for soils we don't know if phospholipids are the only fatty acid-based lipids present in the polar lipid fraction. Lipids extracted from three soils were fractionated with a silica SPE protocol commonly used for soils, with “neutrals” eluted by chloroform, “glycolipids” eluted by acetone, and “phospholipids” eluted by methanol. Fatty acid-based lipids were identified and quantified by liquid chromatography-mass spectrometry. Phospholipids were recovered in the methanol fraction, but this fraction also included betaine lipids. In two soils the methanol fraction was 3–6% betaine lipid while in one soil betaine lipids accounted for 48% of lipids in the methanol fraction. Clearly the fraction obtained by eluting lipids from silica with methanol is not purely phospholipid but can contain significant amounts of other polar lipids.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 31 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil Dynamics and Earthquake Engineering〈/p〉 〈p〉Author(s): Vladimir A. Osinov, Stylianos Chrisopoulos, Theodoros Triantafyllidis〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper presents a numerical analysis of the dynamic deformation of the tunnel lining and the soil caused by a blast-induced pressure pulse of a moderate amplitude (several megapascals) inside the tunnel. The tunnel lining is circular and consists of individual concrete linearly elastic tubbings. The tunnel is located at a depth of 15 m in fully saturated granular soil. Effective-stress changes are described by a hypoplasticity model. The possibility of pore water cavitation at zero absolute pore pressure is taken into account. The problem is solved in a two-dimensional plane-strain formulation with the finite-element program Abaqus/Standard. Emphasis is placed on fine spatial discretization in order to obtain accurate solutions. Stresses and deformations in the lining and in the soil are analysed in detail. The solutions reveal an important role of the strong nonlinearity in the soil behaviour due to the pore water cavitation.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 514〈/p〉 〈p〉Author(s): Mahasin Ali Khan, Meghma Bera, Robert A. Spicer, Teresa E.V. Spicer, Subir Bera〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fossil leaf floras, from the latest Miocene-Pliocene Siwalik Group exposed in Bhutan, sub-Himalaya, are subjected to a CLAMP (Climate Leaf Analysis Multivariate Program) analysis using a high-resolution gridded climate calibration. The CLAMP analysis of 27 different morphotypes of fossil leaves indicates a mean annual temperature (MAT) of 24.1 °C ± 2.8 °C; a cold month mean temperature (CMMT) of 18.9 °C ± 4 °C and a warm month mean temperature (WMMT) of 27.8 °C ± 3.3 °C. The analysis also suggests a weak monsoonal climate (the monsoon index, MSI 46.7; present MSI 52) with growing season precipitation (GSP) of 1819 ± 916 mm (present GSP 2490 mm). Here we also compare palaeoclimate estimates of the latest Miocene-Pliocene Siwalik Group flora from Bhutan (c. 6 to 3.8 Ma) with those of previously investigated Siwalik Group floras from the Miocene-Pleistocene of Arunachal, India and Miocene Siwalik floras of Darjeeling, India which characterise the monsoon signature at the time of deposition. Since all the Siwalik floras of the eastern Himalaya (Darjeeling and Arunachal Pradesh) spanning the mid-Miocene to Pleistocene yield almost the same values we suggest that overall the eastern Himalayan Siwalik climate appears to have been remarkably uniform over the past 15 million years. The MAT result of the Bhutan Siwalik flora differs by just 0.6 °C from Arunachal and 1.2 °C from Darjeeling Siwalik floras. For all Siwalik fossil assemblages, WMMTs, CMMTs and LGSs (length of the growing season) are similar and consistent (WMMTs around 28 °C, CMMTs around 18 °C and LGSs around 12 months). Similarly, the mean annual relative humidity (RH) and specific humidity (SH) appear to have been uniformly around 80% and 14 g/kg respectively throughout the Neogene of the eastern Himalayan Siwaliks. Changes in the monsoon index suggest that in both Bhutan and Arunachal sub-Himalaya, there has been little change in the intensity of the monsoon since mid-Miocene time, while further west in the Darjeeling area precipitation seasonality has increased since the mid-Miocene.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0031018218303523-ga1.jpg" width="327" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Organic Geochemistry, Volume 125〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research, Volume 320〈/p〉 〈p〉Author(s): Hui C.G. Zhang, Jia-Hui Liu, Yi-Chao Chen, Qian W.L. Zhang, Van Tho Pham, Tao Peng, Zhen M.G. Li, Chun-Ming Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Mafic and felsic granulite from the Miyun metamorphic complex, northeast Beijing, North China Craton, occur as either interlayers or lenses within the Late Archean TTG gneiss. In the mafic granulite, the metamorphic peak assemblages (M1) are represented by porphyroblast minerals plus matrix minerals (orthopyroxene + clinopyroxene + plagioclase + quartz ± K-feldspar ± hornblende ± biotite) as well as accessory minerals of zircon + apatite + ilmenite ± magnetite, the post-peak assemblages (M2) are characterized by “red-eye socket” symplectites (garnet + clinopyroxene + plagioclase + quartz) rimming the orthopyroxene or clinopyroxene porphyroblast as well as accessory minerals of rutile, and the final retrograde assemblages (M3) are marked by the hornblende-biotite intergrowth. As for the felsic granulite, the peak assemblages (M1) are represented by the porphyroblast and matrix minerals (garnet + orthopyroxene + biotite + plagioclase + quartz ± K-feldspar) as well as accessory minerals in the matrix (zircon + monazite + apatite + pyrite), the post-peak assemblages (M2) are characterized by “red-eye socket” symplectites (garnet + plagioclase + quartz) rimming the orthopyroxene porphyroblast, and the final retrograde assemblages (M3) are marked by the biotite-calcite intergrowth. Geothermobarometric computation suggests that the M1, M2 and M3 assemblages of the mafic granulite were formed under 〈em〉P-T〈/em〉 conditions of ∼800 to 860 °C/∼6 to 10 kbar, ∼620 to 700 °C/11 to 12 kbar and ∼590 to 660 °C/4 to 6 kbar〈em〉,〈/em〉 respectively, suggesting that these granulites record anticlockwise 〈em〉P-T〈/em〉 paths including final nearly isothermal decompression (ITD) segments, indicative of orogenic process. For the felsic granulite, metamorphic 〈em〉P-T〈/em〉 conditions of the M1 and M3 assemblages were estimated to be ∼680 to 750 °C/6–8 kbar and ∼670 to 680 °C/5 kbar〈em〉,〈/em〉 respectively, also including ITD process. The widely penetrative gneissosity of the granulite and these 〈em〉P-T〈/em〉 paths, suggest a collisional event of cold nappes overthrusting on hot ones or hot nappes being buried/subducted into cold ones and finally experienced fast tectonic exhumation. High-precision SIMS and LA-ICP-MS U-Pb dating of metamorphic zircon of the granulite suggest that the metamorphism occurred at ∼2.5 Ga. These data confirm that the Miyun metamorphic complex experienced a Neoarchean collisional event within the Eastern Block of the North China Craton.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 337〈/p〉 〈p〉Author(s): R. Calvelo Pereira, M. Camps Arbestain, F.M. Kelliher, B.K.G. Theng, S.R. McNally, F. Macías, F. Guitián〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We have investigated the effect of supercritical drying (SD) on the porosity and the BET-N〈sub〉2〈/sub〉 specific surface area (SSA) of five allophane-rich and three non-allophanic topsoils. The contribution of organic matter (OM) and short-range ordered (SRO) constituents to the nanoscale porosity (〈100 nm size) and SSA was also evaluated following chemical treatments to oxidise OM and then remove the SRO phase. The average pore volume and SSA of the soils, measured after SD, are greater than the values obtained after air drying. For soils that are rich in SRO constituents, oxidation of OM leads to an increase in SSA. This observation is attributed to the unblocking of pore necks previously covered by OM, while the subsequent removal of SRO constituents causes a sharp decrease in SSA. The SRO constituents containing oxalate-extractable Al, are the major contributors to the SSA of the inorganic fraction. Besides confirming that SD can help preserve the nanoscale porosity of allophane-rich soils, the results highlight the contribution of SRO constituents to the SSA of soils and their ability to accumulate OM.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Geochemistry, Volume 99〈/p〉 〈p〉Author(s): M. Lanzoni, W.G. Darling, W.M. Edmunds〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Like many dryland regions around the world, the Butana Region of Sudan is almost entirely dependent on groundwater, and its main source of recharge comes from the highly variable 150–200 mm/yr rain that arrives mostly during a three-month rainy season. These rains cause ephemeral wadis to flow and flood, and provide a critical component of shallow aquifer replenishment.〈/p〉 〈p〉This study uses water table fluctuations along a 20 km wadi reach and chemical and stable isotopic tracers in 27 shallow (〈40 m) and 6 deep (70–170 m) wells to show differences between mean recharge in the alluvial aquifer, estimated as 38–105 mm/yr, and the basal Nubian sandstone aquifer unit at 13–36 mm/yr. This study suggests while groundwater from the Nubian sandstone is predominantly palaeowater of −8 to −6‰ δ〈sup〉18〈/sup〉O formed during a wetter, early-Holocene climate, modern recharge does reach the Nubian sandstone aquifer unit in areas 〈0.3 km from the wadi. An upstream dam may also focus this wadi-directed recharge.〈/p〉 〈p〉In the 1980s, conjunctive use of major and trace geochemistry, isotope, and physical hydrology in the study of wadi recharge was only beginning to gain traction as a sub-discipline, and the study of Edmunds et al. (1987) in the Abu Delaig area paved the way for hydrogeochemical studies in unmonitored dryland catchments around the world. Thirty years on from that study, the local population has grown tenfold, water extraction has increased to accommodate mining, and an upstream dam has been built. This study, conducted in a 400 km〈sup〉2〈/sup〉 subset of the original Lower Atbara Basin study, answers a previously unanswered question about wadi recharge to the deeper, Nubian sandstone aquifer unit and offers a unique three-decade perspective on groundwater development in a rural, arid environment expanding beyond its margin of groundwater sustainability.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Soil and Tillage Research, Volume 186〈/p〉 〈p〉Author(s): Márcio R. Nunes, Eloy A. Pauletto, José E. Denardin, Luis E.A. S. Suzuki, Harold M. van Es〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tillage and no-tillage result in different soil mechanical responses which in turn may affect crop growth. Better understanding of soil compressive behavior, therefore, is relevant for the assessment of tillage practices in agricultural systems. We studied the change in soil compressive properties and their relationship with soil physical attributes and plant growth through a chisel tillage chronosequence in a Nitisol where soil was untilled after chiseling for 24 months, 18 months, 12 months, 6 months, and zero months, and was under continuous (12-year) NT. The effects were measured for three soil depth layers: 0 to 7-cm, 7 to 17-cm and 20 to 30-cm. Mechanical chiseling was found to reduce both the degree of compactness and the pre-compression pressure compared to continuous NT, but made the soil more susceptible to new compaction. The effects of chisel tillage generally persisted for a period of 12–24 months. The degree of compactness and soil pre-compression pressure were found to be strongly correlated, and were strongly correlated with other soil physical attributes (soil penetration resistance, soil macroporosity, and soil aggregate stability). They were negatively correlated with root length, root density, and root volume, as well as stalk diameter, linking soil structure indicators to plant growth. Our results also showed that soil compressive parameter values can be estimated based on other soil physical properties that influence plant growth. These findings have potential for studies of crop response to soil structure and soil compaction and could be used to aid in choosing optimal soil management practices, in order to reduce the risk of soil compaction, linking soil compressive behavior and soil physical conditions to plant growth.〈/p〉〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology, Volume 568〈/p〉 〈p〉Author(s): E.A. Zakharova, I.N. Krylenko, A.V. Kouraev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Due to the rapid decline of 〈em〉in situ〈/em〉 observations on river discharge in Arctic regions, evaluation of the continental freshwater input to the Arctic Ocean has become problematic and necessitates the development of alternative approaches based on remote sensing. Radar altimetric satellites have demonstrated high potential for estimation of river water discharge. Compared to polar orbiting altimeters, non-polar orbit satellites have an advantage in temporal sampling. Their greatest drawback, however, is spatial coverage: observations do not cover the low reaches of most parts of Arctic rivers. In this study of the Lena River, we demonstrate a way to overcome this limitation by using a combination of 〈em〉in situ〈/em〉 observations from tributaries and satellite observations in the middle river reaches. The water discharge as well as monthly and annual water flow were evaluated using three virtual stations. Direct combination of the water level from these virtual stations was not possible because of the difference in seasonal amplitude. However, the combination of altimetric discharge from the three independently processed tracks significantly improves the flow retrievals. The accuracy of the monthly water flow estimates at the river outlet is 23%. It increases with the integration time giving 7% for annual flow.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology, Volume 568〈/p〉 〈p〉Author(s): Weihua Wu, Mingzhao Sun, Xiang Ji, Shuyi Qu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To determine the influence of the Mesozoic Yanshanian orogeny in East Asia on contemporaneous Sr isotopic evolution of seawater, we systematically investigated the weathering profile, riverbed sediment and stream water in mono-lithological small granitic watersheds of the Jiuhua Mountains, Anhui, eastern China. Analysis based on 190 samples from 1 to 2 samplings per month during an entire hydrological year, spanning July 2014 to June 2015, shows that the intra-annual change of Sr concentration is 10–70%, but 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios only exhibit a slight change (0.709148–0.710427). This result indicates that using single sampling data to evaluate the influence of chemical weathering on the 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratio evolution of seawater may cause some deviations. The 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratio in the small granitic watersheds of the Jiuhua Mountains is 0.709148–0.710427 with an average of 0.710021, which is significantly higher than the lowest value (0.7068, ∼160 Ma) of seawater in the Phanerozoic. During and after this period, the East Asian continent experienced a strong tectonic event — Yanshanian orogeny and formed widespread Jurassic–Cretaceous igneous rocks, such as the Jiuhua Mountains granite in the Yangtze Block. The Yanshanian granites in several main tectonic units in China exhibit high radiogenic Sr characteristics. Combined with the evidence of enhanced chemical weathering during Late Jurassic-Early Cretaceous, the notable increase of the seawater 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratio after 160 Ma may be related to the Yanshanian orogeny in East Asia.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0022169418308412-ga1.jpg" width="245" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine Micropaleontology, Volume 145〈/p〉 〈p〉Author(s): Sandy M.S. McLachlan, Vera Pospelova, Richard J. Hebda〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thirty mudstone samples from coastal exposures of the Northumberland Formation on Hornby Island, British Columbia, Canada, yielded diverse dinoflagellate cyst and terrestrial sporomorph assemblages. A late Campanian age for the formation has been well defined through magnetostratigraphy, macrofossil biostratigraphy, and geochemical studies of the Hornby Island section. Dinoflagellate cyst taxa corresponding to 61 genera are exceptionally well preserved and include specimens referable to at least 68 formally established species. The earliest occurrences of 〈em〉Canninginopsis maastrichtiensis〈/em〉, 〈em〉Druggidium〈/em〉 cf. 〈em〉discretum〈/em〉, 〈em〉Phanerodinium belgicum〈/em〉, 〈em〉Renidinium〈/em〉 cf. 〈em〉vitilaire〈/em〉, 〈em〉Senegalinium simplex〈/em〉, 〈em〉Spiniferella cornuta〈/em〉, and 〈em〉Xenicodinium delicatum sensu〈/em〉 Slimani et al. are reported along with the most recent occurrence of 〈em〉Senoniasphaera protrusa〈/em〉, extending their stratigraphic ranges into the upper Campanian. The palynomorph assemblages support a late Campanian age. Two dinoflagellate cyst ecozones are recognized (ecozone 1 and ecozone 2). Assemblages suggest sediment deposition in an inner shelf environment with moderate to high nutrient input and primary productivity.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Crystal Growth, Volume 507〈/p〉 〈p〉Author(s): Suresh Sundaram, Xin Li, Saiful Alam, Taha Ayari, Yacine Halfaya, Gilles Patriarche, Paul L. Voss, Jean Paul Salvestrini, Abdallah Ougazzaden〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We report wafer-scale growth and mechanical exfoliation of 20 periodAl〈sub〉0.58〈/sub〉Ga〈sub〉0.42〈/sub〉N/Al〈sub〉0.37〈/sub〉Ga〈sub〉0.63〈/sub〉N multiple quantum wells (MQWs) on h-BN buffered templates and compare them to control samples of the same structure on AlN templates. X-ray diffraction measurements of the MQW structure on h-BN clearly featured satellite peaks up to third order in the 2θ−ω scans indicating good MQW periodicity. Detailed transmission electron microscope (TEM) analysis show good heterointerface quality in the structure and large V-pits on the surface. Depth resolved cathodoluminescence of the MQWs on h-BN revealed a UV emission peak at 299 nm and a sharp shoulder at 292 nm. We also report lift-off and transfer of the MQW on the h-BN structure and have investigated post-transfer optical emission, which demonstrates good preservation of optical emission characteristics. Together these results show the suitability of h-BN buffers for the realization of free-standing or flexible optical devices emitting in the deep UV region.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Crystal Growth, Volume 507〈/p〉 〈p〉Author(s): Peter T. Dickens, Drew T. Haven, Stephan Friedrich, Kelvin G. Lynn〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Co-doping with divalent elements is known to improve the light yield and decay times of some cerium-activated scintillators, despite the stabilization of tetravalent Ce〈sup〉4+〈/sup〉, previously believed to be non-luminescent, from the Ce〈sup〉3+〈/sup〉 state. Ce〈sup〉4+〈/sup〉 stabilization is a charge compensation mechanism which results from divalent ion substitution of a 3 + site. To elucidate the underlying mechanisms, which remain poorly understood, we have grown three Ce,Ca:YAG crystals with different amounts of calcium co-dopants by the Czochralski method and characterized their scintillation and defect properties. Calcium co-doping reduces the decay times and stabilizes the formation of Ce〈sup〉4+〈/sup〉 as expected. Interestingly, X-ray fluorescence analysis reveals a decreased concentration of cerium within the YAG crystal for the sample doped with high levels of Ca, which could contribute to the observation that scintillator properties are improved only for low levels of Ca co-doping. Additionally, positron annihilation spectroscopy reveals an increase in the concentration of vacancies with increasing Ca concentration, while thermoluminescence is observed to show no detectable signal. Furthermore, room temperature photoluminescence of the Ce 4f to 5d〈sup〉1〈/sup〉 transition demonstrates decreased emission with increasing Ca co-doping. These data suggest that Ca co-doping decreases the decay time by creating defects with non-radiative decay pathways.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Estuarine, Coastal and Shelf Science, Volume 217〈/p〉 〈p〉Author(s): Chao Chen, Jiaoqi Fu, Shuai Zhang, Xin Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As a dynamic belt between land and oceans, coastline provides rich information on land-ocean interactions. Sensitive to climate and anthropogenic influences, the changing coastline affects intertidal mudflat resources and the coastal environment. In this study, the greenness and wetness components of the tasseled cap transformation (TCT) were used to extract coastline information. Due to the high total suspended sediment content that leads to the failure of traditional method, sea-waterbody information extraction was initially carried out by TCT. After considering the characteristics of coastline in remote sensing images and coastline morphology in the natural world, the coastline with shorter length was eliminated and the intermittent coastline was connected based on the coordinate geometry description (such as length, distance, and direction). Finally, the results of the coastline information extraction were superimposed on the original images to evaluate accuracy. The experimental results indicated that the proposed method was more effective in clearly delineating the land-ocean boundary. The producer's accuracy and user's accuracy were 0.95 and 0.91, respectively, and the length extraction error was −2.16%. Therefore, the proposed method was more successful for coastline information extraction in the area with high sediment concentration.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Continental Shelf Research, Volume 171〈/p〉 〈p〉Author(s): Bo Yang, Xuelu Gao, Qianguo Xing〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The geochemistry of sedimentary organic matter (SOM) in coastal areas is complex due to its multiple sources and intricate hydrological features. In this study, the biogenic element concentrations and stable carbon (δ〈sup〉13〈/sup〉C) and nitrogen (δ〈sup〉15〈/sup〉N) isotopic compositions in the coastal surface sediments of northern Shandong Peninsula, along with some parameters related to water quality, were analyzed to investigate the temporal-spatial variations in SOM and the processes that control its distribution. The results revealed that marine autogenous organic matter is a major contributor to SOM, accounting for 75.4 ± 3.3%, 60.8 ± 6.6% and 67.4 ± 10.3% in August and November 2015 and March 2016, respectively. In summer, TOC and TN concentrations were significantly higher than those in autumn and spring. The relatively high abundances of SOM were found in the offshore areas in summer and spring, which was contrary to those in autumn. Riverine discharge, nutrients, primary productivity and dissolved oxygen (DO) dynamics could all influence the composition and contents of SOM in different seasons. In summer, high primary productivity and hypoxia condition led to high SOM values. In comparison, SOM contents were relatively low due to sufficient DO in bottom water in autumn and spring. Dissolved nutrients in seawater could affect the accumulation of autogenous organic matter by impacting upon primary production. In summer, nitrate in surface water had the most obvious effects on autogenous organic carbon (AOC) and may be the principal factor of limiting the growth of phytoplankton. In autumn, nitrate as well as dissolved silicate had more effects on AOC storage. However, phosphate had the most obvious influence on AOC storage in spring.〈/p〉〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Gondwana Research, Volume 66〈/p〉 〈p〉Author(s): F. Hodel, R.I.F. Trindade, M. Macouin, V.T. Meira, E.L. Dantas, M.A.P. Paixão, M. Rospabé, M.P. Castro, G.N. Queiroga, A.R. Alkmim, C.C. Lana〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Araguaia Belt encloses a poorly constrained Pan-African (Brasiliano Cycle) continental suture marked by a series of (~750 Ma) ophiolitic units which, when properly characterized, could provide important informations on its geological history, closely linked with the Rodinia demise and further western Gondwana amalgamation. We present new bulk-rock and mineral major and trace element compositions for these ultramafic and mafic units. They mainly consist in fully serpentinized harzburgite, scarce dunite lenses and chromite pods, tectonically overlain by basaltic pillow lavas. Low Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/SiO〈sub〉2〈/sub〉 ratios (0.01 to 0.06), rather high MgO concentrations (42.28 to 45.29 wt%) and spinels' Cr# and Mg# ratios comprised between 0.36 and 0.51 and 0.59 and 0.72, respectively, indicate a depleted oceanic-like protolith. MORB-peridotite interactions are evidenced both by pyroxenite, olivine gabbro and diabase occurrences in the serpentinites and by high TiO〈sub〉2〈/sub〉 (up to 0.42 wt%) contents in spinels from some Serra do Quatipuru serpentinites. These observations support that the Araguaia Belt ophiolitic bodies are the remnants of the upper mantle section of a MOR or subcontinental lithosphere. The serpentinites whole-rock REE content can be modeled as resulting from a dry partial melting involving 14 to 24% of melt extraction, coupled with refertilization by fertile melts, generated deeper in the mantle. Such an oceanic-like setting is also supported by the N-MORB signature of Serra do Tapa and Morro do Agostinho pillow lavas basalts. All together, these results tend to infirm the supra-subduction zone (SSZ) setting previously proposed for these ophiolitic units. Important LILE, B and Li enrichments in the serpentinites likely result from a metasomatic event involving sediments-derived fluids that occurred during the obduction of the units on the Amazonian Craton. Our results combined with (1) the apparent scarcity of igneous crustal rocks, (2) the proximal nature of the metasedimentary rocks hosting the ophiolitic units, and (3) the occurrences of Amazonian Craton fragments eastward of the ophiolitic bodies, allow us to propose that the Araguaia Belt comprises a fossil ocean-continent transition (OCT) accreted on the eastern border of the Amazonian Craton.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1342937X18302545-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 2 May 2017〈/p〉 〈p〉〈b〉Source:〈/b〉 Tectonophysics〈/p〉 〈p〉Author(s): T. Rolf, F.A. Capitanio, P.J. Tackley〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Earth's continents drift in response to the force balance between mantle flow and plate tectonics and actively change the plate-mantle coupling. Thus, the patterns of continental drift provide relevant information on the coupled evolution of surface tectonics, mantle structure and dynamics. Here, we investigate rheological controls on such evolutions and use surface tectonic patterns to derive inferences on mantle viscosity structure on Earth. We employ global spherical models of mantle convection featuring self-consistently generated plate tectonics, which are used to compute time-evolving continental configurations for different mantle and lithosphere structures. Our results highlight the importance of the wavelength of mantle flow for continental configuration evolution. Too strong short-wavelength components complicate the aggregation of large continental clusters, while too stable very long wavelength flow tends to enforce compact supercontinent clustering without reasonable dispersal frequencies. Earth-like continental drift with episodic collisions and dispersals thus requires a viscosity structure that supports long-wavelength flow, but also allows for shorter-wavelength contributions. Such a criterion alone is a rather permissive constraint on internal structure, but it can be improved by considering continental-oceanic plate speed ratios and the toroidal-poloidal partitioning of plate motions. The best approximation of Earth's recent tectonic evolution is then achieved with an intermediate lithospheric yield stress and a viscosity structure in which oceanic plates are ∼ 10〈sup〉3〈/sup〉 × more viscous than the characteristic upper mantle, which itself is ∼ 100–200 × less viscous than the lowermost mantle. Such a structure causes continents to move on average ∼ (2.2 ± 1.0) × slower than oceanic plates, consistent with estimates from present-day and from plate reconstructions. This does not require a low viscosity asthenosphere globally extending below continental roots. However, this plate speed ratio may undergo strong fluctuations on timescales of several 100 Myr that may be linked to periods of enhanced continental collisions and are not yet captured by current tectonic reconstructions.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 International Journal of Rock Mechanics and Mining Sciences, Volume 112〈/p〉 〈p〉Author(s): Zhaohui Wang, Jiachen Wang, Shengli Yang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Longwall top-coal caving (LTCC) is widely employed in the underground mining of thick coal seams. The technique divides a thick coal seam into a lower and an upper section. The bottom coal is sheared by a cutting head and transported by a conveyor in front of the support while the top coal fails and caves under mining pressure, transported by a conveyor at the rear of the support. In an LTCC panel, accurate assessment of top-coal cavability is critical to the design of mining parameters required to achieve continuous caving of top coal. In the present paper, an integrated detection system in which fracture development and ultrasonic wave velocity are used to characterize top-coal cavability is introduced. The cavability is predicted conveniently due to ease of access of the ultrasonic wave velocity in the top coal. Accordingly, an ultrasonic model is established and coupled to the mechanical model previously proposed by the authors to simulate the evolution of the wave velocity in stressed coal. The mechanical-ultrasonic coupling model is validated by comparison against experimental data and further extended to evaluate top-coal cavability in Dongzhouyao mine with a finite difference type code. The predictions, including the excavation-damaged zone, roof weighting interval, stress distribution, stress rotation and ultrasonic wave velocity evolution, are consistent with the field measurements. With the proposed model, the influence provided by hydraulic fracturing on top-coal cavability is investigated by conducting the finite difference type modeling.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 International Journal of Rock Mechanics and Mining Sciences, Volume 112〈/p〉 〈p〉Author(s): Kun Fang, Mamadou Fall〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Understanding the shear behaviour of the interface between rock and cemented paste backfill (CPB) is critical for the cost-effective geotechnical design of underground CPB structures. Curing temperature is one of the key factors that can affect the shear behaviour and resistance of the CPB-rock interface. However, no studies have been performed to investigate its effects on the shear behaviour of the interface between rock and tailings backfill that is undergoing cementation. The main objective of this study is to therefore experimentally study the effects of three different curing temperatures (2 °C, 20 °C, and 35 °C) on the shear behaviour and strength of the CPB-rock interface. The obtained results show that higher curing temperatures (up to 35 °C in this study) can increase the rate of cement hydration and self-desiccation, thus increasing the peak shear stress at the interface between early age CPB and rock. However, the sample cured for a longer time of 28 days at a higher temperature of 35 °C has a lower shear strength than that cured at a lower temperature of 20 °C. This lower shear strength is due to the crossover effect, which is the phenomenon of temperature inversion in the strength of cementitious materials. The findings presented in this paper will contribute to a better assessment of the stability of backfill structures and a better design for them.〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 31 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Physics and Chemistry of the Earth, Parts A/B/C〈/p〉 〈p〉Author(s): Doan Quang Tri, Nguyen Thi Mai Linh, Tran Hong Thai, Jaya Kandasamy〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A few 1D and 2D models are used to simulate and calculate the water level and water quality regarding four state variable (DO, NH〈sub〉4〈/sub〉, NO〈sub〉3〈/sub〉, and BOD) observations in the main rivers and coastal estuaries on the Ca Mau peninsula. This study calibrates and validates 1D and 2D models during the dry and flood seasons for 2014 and 2015, as well as assesses water quality in coastal estuaries during the dry and flood season of 2016 by using a 2D model. The calibration and validation results of the hydrodynamic 1D and 2D models show that there is a high degree of conformity regarding the phase and amplitude of water level at observing stations with mean absolute error (MAE) ranges from 0.05 m to 0.37 m. The RMSE–observation standard deviation ratio (RSR) vary from 0.12 to 0.64, and the percent bias (PBIAS) is from −8.9% to 3.2%. Calibration and validation of water quality parameter (DO, NH〈sub〉4〈/sub〉, NO〈sub〉3〈/sub〉, and BOD〈sub〉5〈/sub〉 concentration) results have a high correlation coefficient during both the dry and flood season of 2014 and 2015. The standards, originating from the National Technical Regulation on Surface Water quality and on Coastal Water Quality, are used to evaluate pollutant concentrations in estuaries in the study area during the dry and flood seasons of 2016. The water quality parameters contain DO (4.6 mg/l–7.9 mg/l) and BOD (4.6 mg/l–10.7 mg/l) concentrations over the National Technical Regulation on Surface and Coastal Water Quality and the A1 limit with DO (〉4 mg/l) and BOD〈sub〉5〈/sub〉 (4 mg/l) on surface water quality for domestic water use in the dry and flood seasons. The calculated results will help managers make better plans for aquaculture and aquatic conservation zones in coastal estuaries in the future.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1474706518301396-fx1.jpg" width="298" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: Available online 1 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Polar Science〈/p〉 〈p〉Author(s): Shunsuke Tei, Shin Nagai, Atsuko Sugimoto〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tree-ring width indices (RWI) are widely used as long-term indicators of past forest ecosystem response to climate change. Due to their larger spatial scales, gridded climate data have been preferred over station data. However, it is not clear how climate dataset type affects correlations between climate variables (e.g., temperature and precipitation) and RWI. To answer this question, RWI was compared to both gridded and station climate datasets over the Siberian forests. Correlation patterns between RWI and seasonal climate variables were mostly similar regardless of dataset. However, some dependence on climate dataset was observed for summer temperatures and previous autumn-winter precipitation. The extent of dataset impacts depends on the similarity of climate variables between datasets, which was related to the distance between the nearest climate station to each RWI site/climate grid point. On the other hand, dataset effects primarily impact statistical significance, and opposite correlations between RWI and climate variables have not been observed for different climate datasets. Therefore, the impacts of climate dataset type on RWI to estimate the forest ecosystem response to climate change are not major, emphasizing the relevance of previous RWI studies that used gridded climate datasets.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geomorphology, Volume 327〈/p〉 〈p〉Author(s): Fei Yan, Qiuwen Zhang, Song Ye, Bo Ren〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Landslides, which could cause huge losses of lives or property damages, result from several different environmental factors whose influences on landslides are very complex. Therefore, it is essential to understand the relationships between these environmental factors and landslides. Thus, the integration of the analytical hierarchy process (AHP) with the normalized frequency ratio (NFR) is evaluated for landslide susceptibility analyses. However, in addition to these complex relationships, the randomness and fuzziness always affect landslide susceptibility mapping. This study introduces the cloud model (CM) to improve the integrated AHP-NFR method, and proposes a novel hybrid AHP-NFR-CM method for landslide susceptibility analyses, which can better address issues of the randomness and fuzziness. Firstly, ten environmental parameters are selected as landslide impact factors, and their values for all the landslides identified in the study area are obtained through the remote sensing (RS) and geographical information system (GIS) technologies. The AHP method is used to obtain the weight of each landslide impact factor, and the NFR method is used to obtain the weight of each subclass in each landslide impact factor, which can reflect the relationship between the landslide impact factor and landslide occurrence. After applying an appropriate compositional operation between the weights of the landslide impact factors and the weights of the subclasses of the impact factors, a landslide susceptibility index (LSI) for each grid divided via the attribution-based spatial information multi-grid method (ASIMG) can be computed. To solve the inevitable issues of randomness and fuzziness in landslide susceptibility analyses, a cloud model that uses three numerical features (expectation, entropy and hyper-entropy) to represent the intension of the concept, is adopted to improve the methods of AHP and NFR. The relative importance of two landslide impact factors is scaled with the cloud model rather than the Saaty criteria. Pair-wise comparison matrixes of landslide impact factors given by each expert are described by the normal cloud model, and the floating cloud model is used to aggregate all experts' judgments. The weight of each landslide impact factor is also expressed with the cloud model rather than a certain value. In improving the NFR, the weight of each subclass of each landslide impact factor is expressed with the cloud model rather than a certain value. In the improvement of the landslide susceptibility results, the domain of landslide risk assessment results is also displayed with the cloud model instead of a series of definite intervals. As the study area examined is large, several grids would need to be divided, meaning that it would take a considerable amount time to subject the entire study area to landslide susceptibility mapping. Thus, we propose a new attribute-based spatial information multi-grid (ASIMG) division method and introduce grid-computing technology to improve the calculation efficiency during the process. Finally, the proposed hybrid AHP-NFR-CM-ASIMG approach is validated and applied in the study area. It's concluded that the new integration of AHP and NFR methods with the cloud model can consider both randomness and fuzziness and therefore can increase the robustness of landslide susceptibility analyses, while the ASIMG technology can enhance the calculation efficiency in regional landslide susceptibility mapping.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology, Volume 568〈/p〉 〈p〉Author(s): Shanshan Deng, Junqiang Xia, Meirong Zhou, Fenfen Lin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recent significant channel evolution in the Jingjiang Reach has raised much attention, particularly the remarkable bank erosion. A coupled model for simulating bed deformation and bank erosion has been proposed in this study, which focuses on the erosion of the bank with a composite structure in the Lower Jingjiang Reach. In order to cover three contributing processes that may interact with each other, the proposed model integrates a one-dimensional morphodynamic module with a two-dimensional module of ground water flow and a bank erosion module for the cantilever failure of a composite riverbank. Model performance was evaluated through a detailed simulation of channel evolution along a 150.8-km subreach in the Jingjiang Reach over the 2005 hydrological year. Satisfying results were obtained from the simulation, showing relatively close agreement between the calculations and measurements in terms of hydrological data at the outlet section, bank erosion sites, longitudinal channel profile and typical cross-sectional profiles. In addition, investigations into temporal changes in bank soil properties and critical overhanging width at cantilever failure demonstrate that there was a seasonal variation in the volumetric water content of bank soil, which increased during the rising and flood periods and then decreased during the recession period, showing an impact on the occurrence timing of cantilever failures. The tensile strength and critical overhanging width had an inverse relationship with the water content, whereas the critical width sharply increased and then decreased during high flows affected by a rapid change in river stage. The temporal distribution of cantilever failure events indicates that cantilever failure primarily occurred in the flood and recession periods. The effects of bed roughness, water content variation and secondary flow on bank erosion were also discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Structural Geology, Volume 118〈/p〉 〈p〉Author(s): Allan D. Hollinsworth, Daniel Koehn, Tim J. Dempster, Kevin Aanyu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present petrographic and structural analyses of a basement-hosted border fault in the East African Rift. Understanding the mechanical evolution and fluid-rock interaction of rift-flank faults is integral to developing models of fluid flow in the crust, where hydraulic connections may occur between basement faults and basin sediments. The Bwamba Fault forms the flank of the Rwenzori Mountains Horst in western Uganda, and has locally reactivated older mylonitic fabrics in the basement gneisses. The fault core features discrete mineralised and veined units. Shear fabrics and fault scarp striations indicate predominately normal kinematics, with minor strike-slip faulting and fabrics. Transient brittle failure was accompanied by two phases of fluid ingress, associated with veining and mineralisation. The first was localised and strongly influenced by host lithology. The second involved widespread Fe-oxide and jarosite mineralisation. The latter signals the onset of a hydraulic connection between Fe- and S-rich sedimentary rocks in the adjacent Semliki Rift Basin and the Bwamba Fault, involving co-seismic and or post-seismic fluid injection into the fault at ca. 150–200 °C, and 2.5–3 km depth. Such evolving permeability connections between basin sediments and basement faults are important for local hydrocarbon and geothermal systems, and may be typical of active rifts.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Atmospheric Environment, Volume 198〈/p〉 〈p〉Author(s): Min Duan, Andi Li, Yanhong Wu, Zuoping Zhao, Changhui Peng, Thomas H. DeLuca, Shouqin Sun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Alpine and subalpine ecosystems on Qinghai-Tibetan Plateau are rich in soil organic carbon and are among the most sensitive regions to climate change, while little is known about the dynamics of soil carbon dioxide (CO〈sub〉2〈/sub〉) in alpine/subalpine ecosystems except for the grassland on the plateau. In this study, the monthly and inter-annual variations in soil CO〈sub〉2〈/sub〉 emission from a subalpine coniferous forest and a subalpine shrubland ecosystem on the eastern edge of the Qinghai-Tibetan Plateau were investigated from 2012 to 2015 using the opaque steady-state chamber method. Soil CO〈sub〉2〈/sub〉 flux rate during the growing season ranged from 153.3 to 683.6 mg m〈sup〉−2〈/sup〉 h〈sup〉−1〈/sup〉 in the coniferous forest, being twice of that (76.6–347.3 mg m〈sup〉−2〈/sup〉 h〈sup〉−1〈/sup〉) in the shrubland, due to the elevation-induced differences in soil temperature and water content and the vegetation-induced differences in soil carbon and nitrogen pools. Both ecosystems showed large monthly variations in soil CO〈sub〉2〈/sub〉 flux rate, while relative to the coniferous forest, the shrubland had a less inter-annual variation in soil CO〈sub〉2〈/sub〉 emission. The two ecosystems had the same temperature sensitivity of soil CO〈sub〉2〈/sub〉 emission, which suggests that they will respond similarly to global warming concerning soil CO〈sub〉2〈/sub〉 flux rate. The results highlight the importance of soil CO〈sub〉2〈/sub〉 emission in subalpine forest and shrubland ecosystems, which can be helpful to reduce the uncertainty of regional estimates of carbon budget in subalpine regions under global warming.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology, Volume 568〈/p〉 〈p〉Author(s): M. Esteves, C. Legout, O. Navratil, O. Evrard〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉In mountainous catchments, soil erosion and sediment transport are highly variable throughout time and their quantification remains a major challenge for the scientific community. Understanding the temporal patterns and the main controls of sediment yields in these environments requires a long term monitoring of rainfall, runoff and sediment flux. This paper analyses this type of data collected during 7 years (2007–2014), at the outlet of the Galabre River, a 20 km〈sup〉2〈/sup〉 watershed, in south eastern France, representative of meso-scale Mediterranean mountainous catchments.〈/p〉 〈p〉This study is based on a hybrid approach using continuous turbidity records and automated total suspended solid sampling to quantify the instantaneous suspended sediment concentrations (SSC), sediment fluxes, event loads and yields. The total suspended sediment yield was 4661 Mg km〈sup〉−2〈/sup〉 and was observed during flood events. The two crucial periods for suspended sediment transport at the outlet were June and November/December (63% of the total). The analysis of suspended sediment transport dynamics observed during 236 flood events highlighted their intermittency and did not show any clear relationship between rainfall, discharge and SSC. The most efficient floods were characterised by counter-clockwise hysteresis relationships between SSC and discharges. The floods with complex hysteresis were the more productive in the long term, during this measuring period exceeding a decade. Nevertheless, the current research outlines the need to obtain medium-term (five years) continuous time series to assess the range of variations of suspended sediment fluxes and to outline clearly the seasonality of suspended sediment yields. Results suggest the occurrence of a temporal dis-connectivity in meso-scale catchments over short time-scales between the meteorological forcing and the sediment yields estimated at the outlet. These findings have important methodological impacts for modelling and operational implications for watershed management.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Earth and Planetary Science Letters, Volume 506〈/p〉 〈p〉Author(s): Jennifer Woods, Tom Winder, Robert S. White, Bryndís Brandsdóttir〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Understanding dikes is vital as they serve both as bodies that build the crust and as conduits that feed eruptions, and must be monitored to evaluate volcanic hazard. During the 2014–15 Bárðarbunga rifting event, Iceland, intense seismicity accompanied the intrusion of a ∼50 km lateral dike which culminated in a 6 month long eruption. We here present relocations of earthquakes induced by the lateral dike intrusion, using cross-correlated, sub-sample relative travel times. The ∼100 m spatial resolution achieved reveals the complexity of the dike propagation pathway and dynamics (jerky, segmented), and allows us to address the precise relationship between the dike and seismicity, with direct implications for hazard monitoring. The spatio-temporal characteristics of the induced seismicity can be directly linked in the first instance to propagation of the tip and opening of the dike, and following this – 〈em〉after dike opening〈/em〉 – indicate a relationship with magma pressure changes (i.e. dike inflation/deflation), followed by a general ‘post-opening’ decay. Seismicity occurs only at the base of the dike, where dike-imposed stresses – combined with the background tectonic stress (from regional extension over 〉200 yr since last rifting) – are sufficient to induce failure of pre-existing weaknesses in the crust, while the greatest opening is at shallower depths. Emplacement oblique to the spreading ridge resulted in left-lateral shear motion along the distal dike section (studied here), and a prevalence of left-lateral shear failure. Fault plane strikes are predominately independent of the orientation of lineations delineated by the hypocenters, indicating that they are controlled by the underlying host rock fabric. This high-resolution study provides unprecedented opportunity for comparison with both geodetic and field (frozen dike) observations, and development and consolidation of analytical and analogue models, with implications for rifting processes and real-time monitoring of magma intrusion.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈/p〉〈/div〉 〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0012821X18306289-gr001.jpg" width="408" alt="Graphical abstract for this article" title=""〉〈/figure〉

Description: 〈p〉Publication date: 15 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Sedimentary Geology, Volume 378〈/p〉 〈p〉Author(s): Catherine Chagué, Peter Bobrowsky〈/p〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of African Earth Sciences, Volume 150〈/p〉 〈p〉Author(s): Minoru Kusakabe, Rosine E. Tiodjio, Bruce Christenson, Kazuto Saiki, Takeshi Ohba, Muga Yaguchi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Lake Nyos is a meromictic lake with strong stratification separated into 4 distinct layers; shallow, intermediate, transitional, and bottom layers. This article discusses enrichment of Fe〈sup〉2+〈/sup〉 in the bottom water in January 2003 when the effect of artificial degassing that started in January 2001 on the chemical structure of the lake was still minimal. In the bottom layer (205.5–209.5 m), Fe〈sup〉2+〈/sup〉 and HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 are the major dissolved species and their concentrations increase sharply toward the bottom. Enrichment of Fe〈sup〉2+〈/sup〉 and HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 is most likely caused by anaerobic microbial reduction of Fe(OH)〈sub〉3〈/sub〉 precipitates at the water-sediment interface. The Fe(OH)〈sub〉3〈/sub〉 precipitates sank to the bottom after atmospheric oxidation of Fe〈sup〉2+〈/sup〉 dispersed by the degassing pipe. Lateritic hematite may also participate in the reduction reaction. Production of Fe〈sup〉2+〈/sup〉 and HCO〈sub〉3〈/sub〉〈sup〉−〈/sup〉 significantly increases the alkalinity and electric conductivity of the bottom-most water and is responsible for a small rise of pH between 205 m and 209.5 m, the bottom. The other dissolved species, e.g., Na〈sup〉+〈/sup〉, K〈sup〉+〈/sup〉, Ca〈sup〉2+〈/sup〉, Mg〈sup〉2+〈/sup〉, SiO〈sub〉2(aq)〈/sub〉 etc., result from the CO〈sub〉2〈/sub〉-water-basalt interaction at low temperatures (25°∼30 °C) in the sub-lacustrine fluid reservoir that is believed to exist in the diatreme beneath the lake bottom, and they seep into the bottom layer.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computers & Geosciences, Volume 122〈/p〉 〈p〉Author(s): Hassan Talebi, Ute Mueller, Raimon Tolosana-Delgado〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ore deposits usually consist of ore materials with different discrete (e.g. rock and alteration types) and continuous (e.g. geochemical and mineral composition) features. Financial feasibility studies are highly dependent on the modelling of these features and their associated joint uncertainties. Few geostatistical techniques have been developed for the joint modelling of high-dimensional mixed data (continuous and categorical) or constrained data, such as compositional data. The compositional nature of the mineral and geochemical data induces several challenges for multivariate geostatistical techniques, because such data carry relative information and are known for spurious statistical and spatial correlation effects. This paper investigates the application of the direct sampling algorithm for joint modelling of compositional and categorical data. In some mining projects the amount of available data may be enormous in some parts of the deposit and if the density of measurements is sufficient, multivariate geospatial patterns can be derived from that data and be simulated (without model inference) at other undersampled areas of the deposit with similar characteristics. In this context, the direct sampling multiple-point simulation method can be implemented for this reconstruction process. The compositional nature of the data is addressed via implementing an isometric log-ratio transformation. The approach is illustrated through two case studies, one synthetic and one real. The accuracy of the results is checked against a set of validation data, revealing the potential of the proposed methodology for joint modelling of compositional and categorical information. The direct sampling technique can be considered as a smart move to assess the future risk and uncertainty of a resource by making use of all the information hidden within the early data.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 337〈/p〉 〈p〉Author(s): Hongfei Liu, Yang Wu, Zemin Ai, Jiaoyang Zhang, Chao Zhang, Sha Xue, Guobin Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉DOM is the most bioavailable organic pool in the soil. The restoration of vegetation on abandoned cropland has a major impact on the concentration and composition of the DOM and thus affects the biodegradability of the soil DOM. Understanding the response of the microbial degradation of the DOM to temperature is important to maintain soil bioavailable organic matter in the field. We conducted a laboratory DOM solution incubation experiment to examine the temporal dynamics of DOM concentrations at temperatures of 4 °C (low), 20 °C (medium), and 35 °C (high) for four types of land uses: sloped cropland, grassland, shrub land, and woodland. Ultraviolet–visible and fluorescence spectroscopy were used to determine the structural complexity of the DOM. The conversion of the sloped cropland to shrub land and woodland significantly increased contents of DOC, DON, and recalcitrant substances in DOM soilution, such as humic-like material and fulvic acid, and stabilised the DOC pool, and reduced the decomposition of the DOC at 20 °C and 35 °C. The conversion of the sloped cropland to woodland dramatically reduced TDN decomposition. The DON loss after 60-day incubation significantly correlated with the initial content of tryptophan-like material. The biodegradability of the DON was higher and more sensitive to temperature than that of the DOC. Rising temperature initially promotes the decomposition of tryptophan-like material, and later promotes the degradation of more recalcitrant substances, such as humic-like material and fulvic acid, which enhanced the decomposition of the DOC and DON. The results suggest that the conversion of sloped cropland to shrubland and woodland not only promoted the accumulation of DOC, TDN, and recalcitrant substances in DOM solution, and decreased their biodegradability but also decreased the temperature sensitivity of the decomposition of the DOC and DON. Therefore, shrubland and woodland were the optimal choices for revegetation in the Loess Plateau of China.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0016706117316403-ga1.jpg" width="301" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research, Volume 320〈/p〉 〈p〉Author(s): Zhongwu Lan, Yuji Sano, Takuya Yahagi, Kentaro Tanaka, Kotaro Shirai, Dominic Papineau, Yusuke Sawaki, Takeshi Ohno, Mariko Abe, Hongwei Yang, Hai Liu, Tao Jiang, Teng Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High-resolution isotopic analyses were conducted on core samples from the Ediacaran Doushantuo Formation at the Wangjiapeng section, western Hubei Province in South China, whereby two laterally traceable, negative δ〈sup〉13〈/sup〉C〈sub〉carb〈/sub〉 excursions (EN1 and EN3) were recognized. The magnitude and duration of these excursions permit intra-basinal and inter-basinal correlation, which indicates that they probably represent a global change in seawater composition. The occurrence of decoupled δ〈sup〉13〈/sup〉C〈sub〉car〈/sub〉-δ〈sup〉13〈/sup〉C〈sub〉org〈/sub〉 with almost invariable δ〈sup〉13〈/sup〉C〈sub〉org〈/sub〉 values at Wangjiapeng, Zhongling, Yangjiaping sections is consistent with remineralization of a dissolved organic carbon (DOC) pool by means of sulfate reduction, as recorded in EN3. The synchronous presence of EN3, a shift to higher 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr and decrease of Mn and Fe contents and δ〈sup〉15〈/sup〉N values together points to a glacial influence whereby oxygenation and remineralization of reduced carbon produced 〈sup〉13〈/sup〉C-depleted DIC. Glaciations cause a drop in sea level, which itself leads to increased continental shelf area to be exposed to surface weathering, and ultimately to enhanced delivery of radiogenic 〈sup〉87〈/sup〉Sr. The increase of 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios, sulfate and phosphate are consequences of surface runoff into oceanic environments and such perturbations induce biogeochemical changes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 7 July 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Dexin Tian, Hao Yang, Wenchun Ge, Yanlong Zhang, Jingsheng Chen, Huijun Chen, Xiuyu Yun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Central Inner Mongolia is located in the southeastern segment of the Central Asian Orogenic Belt (CAOB), and controversy has long surrounded its late Paleozoic tectonic evolution. Here, we present an integrated study of zircon U-Pb ages, whole rock major and trace elements, and zircon Hf isotopes for five less studied alkali feldspar granitic plutons in the Dongwuqi area to the north of the Erenhot-Hegenshan-Heihe suture zone. Zircon U–Pb dating by laser ablation-inductively coupled plasma–mass spectrometry (LA–ICP–MS) indicates that these granitic plutons were emplaced in the Late Carboniferous (315–300 Ma). The Late Carboniferous alkali feldspar granites belong to high-K calc-alkaline series and are evolved I-type granites. They are high in SiO〈sub〉2〈/sub〉 (73.22–77.36%), and low in MgO (0.07–0.49%) with enrichments in light rare earth elements (LREEs), Zr, Hf, Rb, Th, and U, and depletions in Ba, Nb, Ta, Sr, and Eu. The Dongwuqi granitic rocks are characterized by high positive zircon ε〈sub〉Hf〈/sub〉(t) values (+7.6 to +15.1), and relatively young two-stage Hf model (〈em〉T〈/em〉〈sub〉DM2〈/sub〉) ages (364–835 Ma). These geochemical data, together the common miarolitic texture, indicate that they were derived from partial melting of juvenile arc-related mafic to intermediate rocks in the lower crust, and eventually emplaced in low-pressure conditions or at shallow crustal levels, with involvement of extensive fractional crystallization during magma evolution. Our new results, along with the published regional data, delineate a NE-trending Carboniferous continental arc belt (more than 1700 km) in the northern accretionary zone of the Erenhot-Hegenshan-Heihe suture. Accordingly, we invoke that the Dongwuqi Late Carboniferous high-K granites were emplaced in an active continental margin setting, which was probably related to the northwestward subduction of the Hegenshan oceanic plate beneath the Xing'an-Uliastai-Nuhetdavaa block.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302712-fx1.jpg" width="269" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Marine and Petroleum Geology, Volume 100〈/p〉 〈p〉Author(s): Hongwei Ping, Honghan Chen, Simon C. George, Chunquan Li, Shouzhi Hu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The fluorescence evolution of oils has been measured by simulation of petroleum generation and expulsion in a half-closed system using hydrous pyrolysis based on four oil-prone source rocks (Type I and II kerogens) from the Dongying Depression, Bohai Bay Basin, China. The results suggest that the fluorescence characteristics of expelled oil are independent of oil-prone kerogen types, but are strongly related to oil generation and expulsion processes which are controlled by thermal maturity of source rocks. The fluorescence spectral parameters (〈em〉λ〈/em〉〈sub〉max〈/sub〉, Q〈sub〉650/500〈/sub〉 and QF-535) of expelled oils show no obvious variation, or even show gradual redshifts when the highest 〈em〉λ〈/em〉〈sub〉max〈/sub〉 occurs at peak bitumen generation, depending on the expulsion process. A blueshift of fluorescence color occurs only during the main oil generation and expulsion stage, which immediately follows the peak bitumen generation stage. However, the expelled oil mainly exhibits green to yellow fluorescence colors (500 nm 〈 〈em〉λ〈/em〉〈sub〉max〈/sub〉 〈 590 nm), which suggests that it is impossible for blue fluorescent oil inclusions to be trapped from the oil directly generated in an open or half-closed source rock system for oil-prone source rocks based on the experimental results. This study demonstrates that the relationship between the fluorescence color of oil inclusions and thermal maturity for oil-prone source rocks is valid only when the source rocks reach the main oil generation and expulsion stage, where the source rocks should have consistent expulsion characteristics. Under this situation, the green fluorescent oil inclusions (500 nm 〈 〈em〉λ〈/em〉〈sub〉max〈/sub〉 〈 550 nm) generally have a higher thermal maturity than the oil inclusions with yellow fluorescence (580 nm 〈 〈em〉λ〈/em〉〈sub〉max〈/sub〉 〈 590 nm). Otherwise, the petroleum expulsion processes may complicate the relationship between the fluorescence color of oil inclusions and thermal maturity, and oil inclusions with yellow fluorescence do not necessarily have a low thermal maturity. Our experiments have established the first boundary conditions for the fluorescence behaviour of oil as a function of thermal maturity, acknowledging that compositional change of the oil is also occurring during migration, and hence before entrapment in reservoirs.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Mei-Fei Chu, Yu-Ming Lai, Qiuli Li, Wen-Shan Chen, Sheng-Rong Song, Hao-Yang Lee, Te-Hsien Lin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The initiation and duration of magmatism in the Tatun Volcano Group (TVG), likely resulting from extensional collapse of the northern Taiwan mountain belt, remains an important issue of debates in the Taiwan orogeny. Here we report a detailed study of U-Pb ages determined by SIMS and LA-ICPMS, together with Hf isotopic data, of zircon separates from a total of 22 extrusive rocks from the TVG lava flow and additional two andesites from Keelungyu (KLY), a volcanic islet off NE Taiwan. Magmatic zircons from the TVG are characterized by uniform and high Hf isotopic ratios, with ε〈sub〉Hf〈/sub〉(T) mostly from +20 to +10. Their overall 〈sup〉206〈/sup〉Pb/〈sup〉238〈/sup〉U ages suggest that the TVG magmatism was initiated ∼3 Ma but more active ≤0.8 Ma with a flare up ≤0.35 Ma. Magmatic zircons from the two KLY samples reveal identical 〈sup〉206〈/sup〉Pb/〈sup〉238〈/sup〉U ages (0.41 Ma), coupled with Hf isotopes [ε〈sub〉Hf〈/sub〉(T): +25 to +9] comparable to those of the TVG. Thus, KLY is proposed as part of the TVG. Consequently, we argue that the main body of the TVG formed ≤0.8 Ma by post-collisional volcanism, but the mechanism resulting in the magmatic episodes ≥1.0 Ma remains obscure due to the scarcity of rock exposures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research, Volume 318〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Applied Geophysics, Volume 159〈/p〉 〈p〉Author(s): Zhang Sheng, Meng Xiaohong, Zhang Minghua, Chen Zhaoxi, Xiu Chunxiao, Liu Yajie〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Gravity forward modeling of the geological model is a necessary part in the investigation of subsurface density structures, and is extremely valuable in developing and testing gravity data processing and inversion algorithms. In dealing with practical problems, the traditional block model based gravity forward procedure is time consuming, and cannot accurately forward the semi-infinite extended model. To deal with these problems, we proposed an improved residual node density model based gravity forward method. In this method, we firstly transform the density model into a residual node density model with a specific boundary condition; and then remove all the zero residual node density points; and then calculate the gravity anomaly with these non-zero residual node density points. We implement the proposed method in both 2D and 3D cases with Fortran language, and then applied it to Marmousi2 (2D) and SEG/EAGE salt model (3D) gravity forward modeling. The result demonstrates that this method is efficient and has advantage in forward semi-infinite extended model with absolute density by providing a specific boundary condition.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 2 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Xiao-Ju Yang, Qing Xu, Miao-Qin Lin, Jian-Guo Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉New fossil plants are reported from the lower part of the Linbuzong Formation at Qubsang, Doilungdeqen, Lhasa, Tibet. The assemblage comprises 〈em〉Neocalamites〈/em〉 sp., 〈em〉Ptilozamites tibetica〈/em〉 Yang, 〈em〉Ptilozamites〈/em〉 sp., ?〈em〉Ptilozamites〈/em〉 sp., 〈em〉Zamites〈/em〉 sp. 1, 〈em〉Zamites〈/em〉 sp. 2, ?〈em〉Zamites〈/em〉 (?〈em〉Otozamites〈/em〉) sp. 1, ?〈em〉Zamites〈/em〉 sp. 2., 〈em〉Ptilophyllum〈/em〉 sp. 1, 〈em〉Ptilophyllum〈/em〉 sp. 2, 〈em〉Ptilophyllum〈/em〉 sp. 3, 〈em〉Geinitzia〈/em〉 sp. and 〈em〉Elatocladus〈/em〉 (?〈em〉Torreyites〈/em〉) sp. Among these plants at least two of them, 〈em〉Ptilozamites tibetica〈/em〉 and 〈em〉Elatocladus〈/em〉 (?〈em〉Torreyites〈/em〉) sp. are firstly discovered in this area, and the others occured frequently in the Mesozoic flora in Tibet. Associated miospores suggests an Early Cretaceous age for the assemblage. The abundance of 〈em〉Ptilophyllum〈/em〉 and conifer 〈em〉Geinitzia〈/em〉 sp. and the absence of Ginkgoales might indicate a palaeoenvironment with both a low latitude and high temperatures, and a tropical arid to semi-arid climate predominating in this coastal area. The Qubsang assemblage, composed mainly of Bennettitales and Coniferopsida, does not resemble any contemporaneous ones known from Gondwanaland or Eurasia. Although the flora lacks characteristic Wealden ferns, such as 〈em〉Weichselia〈/em〉, the plant assemblage shows a general relation to Tethyan floras of the area and might roughly correspond in age to the Wealden floras of Western Europe.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 7 July 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Zhifeng Wan, Xianqing Wang, Yongfang Li, Xing Xu, Yuefeng Sun, Zhengxin Yin, Hongxiang Guan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Information about ocean evolution and material-energy exchange between the ocean and surrounding continents can be preserved in marine sediments. The Southwest Sub-basin, located among the Xisha Islands, the Zhongsha Islands, and the Nansha Islands, is an ideal tectonic unit to analyze the sedimentary environments of the South China Sea. In this paper, the distribution patterns of lipid biomarkers and their compound-specific stable carbon isotopes in surface sediments from the Southwest Sub-basin of the South China Sea were analyzed. Lipid biomarkers are composed of different proportions of aliphatic hydrocarbons, carboxylic acids, alcohols and series of sterols, indicating that the organic matter of the Southwest Sub-basin was derived from marine bacteria, algae and terrestrial higher plants. The average concentration of total organic carbon (TOC) in the study samples was 0.5 ± 0.16%. TOC, total 〈em〉n〈/em〉-alkanes, and total carboxylic acids (TFA) decreased gradually from the margins to the center of the sub-basin, whereas the content of total 〈em〉n-〈/em〉alkanols increased. The spatial distribution trends resulted from varying water depths and the contribution of terrestrial organic matter. The concentration of TFA and the TFA/TOC revealed that the accumulation of organic matter in this area was generally low. The strong correlation between TOC and TFA of surface sediments in the study area may be related to a balance between the ocean production and ocean deposition rates.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302748-fx1.jpg" width="294" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): He Wang, Yan Fang, Sha Li, Xudong Hou, Bo Wang, Haichun Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the Dazhuoma stratigraphic section near the Gangni Township, Amdo County, northern Tibet, China, the Paleocene-lower Eocene Niubao Formation yields plenty of well-preserved microfossils and insects. A restudy of 〈em〉Hylophalangopsis chinensis〈/em〉 Lin and Huang, 2006, an orthopteran insect from this formation, indicates that it should be attributed to Zeuneropterinae of Stenopelmatidae instead of Prophalangopsidae of Hagloidea in the original study. Some characters preserved in this species are herein considered transitional between Aboilinae (Prophalangopsidae) and Stenopelmatoidea, supporting the deduction that a close relationship exists between Stenopelmatoidea and Aboilinae. The close relationship of 〈em〉Hylophalangopsis〈/em〉 with the other zeuneropterines in Canada and Scotland indicates a middle-late Paleocene age for the lower Niubao Formation, supported by some previous studies, and further suggests a warm and humid climate in the Dazhuoma area in the middle-late Paleocene, supported by some important evidence.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302256-fx1.jpg" width="209" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 18 July 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Rukai Zhu, Caineng Zou, Zhiguo Mao, Haibo Yang, Xiao Hui, Songtao Wu, Jingwei Cui, Ling Su, Sen Li, Zhi Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Tight oil in China is mainly distributed in Mesozoic-Cenozoic continental petroliferous basins, either generally occurs in tight sandstone or tight carbonate reservoirs which are paragenetic to or in contact with lacustrine petroleum source rocks. By the end of 2016, the continental tight oil in China has established an annual production capacity of 1.55 million tons, and a cumulative oil production of 2.52 million tons. In 2016, the continental tight oil production in China was about 800,000 tons. By analyzing the characterization of the tight oil in Ordos Basin, Songliao Basin, Jungar Basin, the organic-rich shale in China were formed in multiple geological periods including the Permian, Triassic, Jurassic, Cretaceous, Neogene, and Paleogene, in freshwater, semi-saline to hyper-saline lacustrine depositional setting. They are generally tens of meters to several hundreds of meters thick, have total organic carbon (TOC) contents of 0.4–16%, and thermal maturity of 0.4–1.4%. Algal bloom as results of volcanism, low sedimentation rate, transgression, and stratification of water body are prominent factors controlling the formation of organic-rich shales. Tight oil reservoirs in China mainly include tight sandstone, tight carbonate rock, tight sedimentary tuff, etc., all of which are characterized by strong heterogeneity and poor petrophysical properties, with 〈em〉in situ〈/em〉 porosity and permeability generally no more 12% and 1 × 10〈sup〉−3〈/sup〉 μm〈sup〉2〈/sup〉 respectively. They are also characterized by tight pore-throat systems of nano- to micro-scales, with pore throat diameters in the range of 80–1800 nm, and complex pore structures. The producing reservoirs have pressure coefficients between 0.7 and 1.8, covering under-pressure to over-pressure. Crude oil properties vary greatly with densities ranging from 0.75 to 0.92 g/cm〈sup〉3〈/sup〉. It is believed that the abundance and effectiveness of hydrocarbon supply controls the formation of oil saturation, and tight oil “sweet spots” are generally in or near the areas with high hydrocarbon expulsion intensities. In addition, the quality of the source rock and the type of source reservoir control the distribution of the “sweet spots”, and storage space and movable fluid guarantee the formation of the “sweet spot” area of high oil saturation. “Sweet spots” are often developed in local mini-structural highs under a broad and gentle-sloped background. Continental tight oil in China has estimated geological resource of 14.66 × 10〈sup〉9〈/sup〉 tons with a technically recoverable resource of 1.45 × 10〈sup〉9〈/sup〉 tons. Tight oil is mainly distributed in Ordos Basin, Songliao Basin, Bohai Bay Basin, Junggar Basin, and Qaidam Basin, within the Mesozoic and Cenozoic formations. Overall China has a relatively large tight oil reserve and good exploration prospect.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 21 July 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Yang Yu, Min Sun, Chao Yuan, Guochun Zhao, Xiao-long Huang, Yamirka Rojas-Agramonte, Qiong Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Chinese Altai underwent intensive mafic and felsic magmatism in the middle Paleozoic, which was the most important magmatic event in the region. It is still unclear for the role of the event in formation of the crust that is thick (∼56 km) and has structure of three-layer stratification. In this study, the data for the middle Paleozoic mafic rocks and granites are comprehensively compiled and integrated with new geochronological, petrological, geochemical and Sr-Nd-Pb isotopic data for gabbroic rocks from Keketuohai area and tonalite and biotite granites from Habahe area. The middle Paleozoic mafic rocks exhibit two evolutionary trends, which can be defined as high-Al and low-Al types because of their evolution at different crustal levels but mainly at amphibole stability field. The middle Paleozoic I-type granites are mainly metaluminous to weakly peraluminous and were possibly generated by dehydration melting of those mafic rocks evidenced by similar Nd isotopic compositions (ε〈sub〉Nd〈/sub〉(t) = −2.7 to +3.8 for granites; ε〈sub〉Nd〈/sub〉(t) = −2.5 to +8.5 for the middle Paleozoic mafic rocks). The strongly peraluminous granites show large range in MgO (0.41–3.85 wt%), Cr (5.32–153 ppm) and Ni (3.69–104 ppm), suggesting that they might be produced by dehydration melting of a mixed source composed of materials from the Habahe Group and the middle Paleozoic igneous rocks. The middle Paleozoic I-type and strongly peraluminous granites mostly have high contents of Y and Yb and show low Sr/Y and La/Yb ratios, indicating insignificant residual garnet in the source. The Habahe tonalites (372 ± 3 Ma) are characterized by positive ε〈sub〉Nd〈/sub〉(t) values (+4.7–+4.8) and high (〈sup〉207〈/sup〉Pb/〈sup〉204〈/sup〉Pb)〈sub〉t〈/sub〉 and (〈sup〉208〈/sup〉Pb/〈sup〉204〈/sup〉Pb)〈sub〉t〈/sub〉 ratios, similar to those of the middle Paleozoic mafic rocks. These granites have low contents of MgO (0.50–0.88 wt%), flat rare earth elements (REE) patterns ([La/Yb]〈sub〉N〈/sub〉 = 1.1–1.6) and strongly positive Eu anomaly (1.6–2.5), indicating that they were possibly evolved from the high-Al mafic magma through fractionation of Mg-rich minerals. The Habahe biotite granites (359 ± 4 to 381 ± 4 Ma) are strongly peraluminous (A/CNK = 1.12–1.23), show concaved REE patterns ([Dy/Yb]〈sub〉N〈/sub〉 = 0.90–1.24), and have low (〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr)〈sub〉i〈/sub〉 ratios, positive ε〈sub〉Nd〈/sub〉(t) values (+1.9 to +5.5) and high (〈sup〉207〈/sup〉Pb/〈sup〉204〈/sup〉Pb)〈sub〉t〈/sub〉 and (〈sup〉208〈/sup〉Pb/〈sup〉204〈/sup〉Pb)〈sub〉t〈/sub〉 ratios. These geochemical features suggest that they were possibly derived from hydrous melting of the middle Paleozoic mafic rocks with residual amphibole at middle crustal level. The middle Paleozoic magmatism recorded the most important period for the crustal differentiation in the Chinese Altai. The evolution of mafic magma and formation of granites mainly occurred within amphibole stability field, illustrating a relatively shallow crustal differentiation process (〈30 km) although the crust may have been thickened.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302888-fx1.jpg" width="412" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 2 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Jia-Ping Liao, Bor-Ming Jahn, Igor Alexandrov, Sun-Lin Chung, Pan Zhao, Vitaly Ivin, Tadashi Usuki〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study presents new whole-rock geochemical and Sr-Nd isotopic data, together with zircon U-Pb ages and Hf isotope ratios, of granitic rocks and associated dikes from the Okhotsk and Aniva plutons in South Sakhalin. The two plutons emplaced in the Mid-Eocene show markedly contrasting geochemical characteristics. The Okhotsk granites (44–42 Ma) are mildly peraluminous (A/CNK = 1.02–1.08), ferroan and alkali-calcic, and have transitional I- and A-type granite features. This granite suite contains rare inherited zircons. The Aniva granites (40 Ma) are peraluminous (A/CNK = 1.08–1.21), magnesian and calc-alkaline, typical of S-type features. This suite, essentially biotite-cordierite bearing, has abundant inherited zircons dated from 48 to 2446 Ma. Whole-rock Sr-Nd and zircon Hf isotopic data indicate that the genesis of the two plutons involved partial melting of mixed sources with dominant juvenile crustal components (newly accreted accretionary complexes or newly underplated basaltic materials) and magma mixing between underplated mantle-derived magmas and crustal partial melts. The Okhotsk granites have εNd (T) values of +3.1 to +3.7, initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios of 0.7047–0.7048, and zircon εHf (T) values of +11 to +16. The Aniva granites have εNd (T) values of +0.5 to +0.9 and initial 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios of 0.7052 to 0.7055, and zircon εHf (T) values of +4 to +12. According to Sr-Nd and Nd-Hf isotopic mixing calculations, the proportion of the juvenile component (=mantle-derived materials) is estimated to be 〉70%, and that of the upper crust component is less than 30% in the sources of the Okhotsk and Aniva plutons. We further argue that, based on Nd and Hf isotopic constraints, the Okhotsk and Aniva granites are correlated to the Mid-Eocene granites in the western and eastern parts, respectively, of the Hidaka terrane in Hokkaido. From the Sikhote-Alin area to the Sakhalin and Hokkaido Islands, the increase in juvenile sources and the decrease in recycled crustal materials are exhibited in the Nd isotopic signatures of the granitoids from early Cretaceous to Miocene. The granitic magmatism in South Sakhalin and Hokkaido may be the most prominent example of juvenile crustal growth among these areas.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018301974-fx1.jpg" width="324" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences, Volume 169〈/p〉 〈p〉Author(s): Hakim Saibi, Saad Mogren, Manoj Mukhopadhyay, Elkhedr Ibrahim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Harrat Lunayyir (HL) 2007–2009 earthquake swarm has attracted much scientific interest mainly due to its occurrence within the Large Igneous Province (LIP) of Saudi Arabia. Qualitative interpretation of aeromagnetic anomalies is suggestive of linear dike-like anomalies, striking NW-SE, across the earthquake swarm zone (ESZ). Residual Bouguer anomaly data for HL range between −4.3 and 1.5 mgal and show a 20 km-wide gravity low flanked by lateral gravity highs. The axial-zone of low gravity corresponds to the ESZ cluster. Employing a three-dimensional (3D) inversion of the residual gravity field with a one-dimensional (1D) P-wave velocity model as a proxy for background density variations with depth, we imaged a mid-to-upper crustal low density zone (〉10 km depth). We interpret this zone as the source area of ascending magma that intruded into the upper crust underlying the HL during the 2009 seismic crisis. The inversion also highlights lower than average density rocks beneath the western parts of the HL whereas its eastern part is composed of rocks of higher density. The 3D magnetic inversions lead us to infer magmatic intrusion of lower magnetic susceptibility at this locality extending vertically from 1.57 km altitude (above sea level) to its bottom edge at 10.8 km depth (below sea level). Based on these results, the 2007–2009 ESZ is likely associated with rift-related extension associated with the Red Sea spreading, where a trans-crustal magmatic plumbing system extends to depths of about 10 km beneath the centre of HL.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302864-fx1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 11 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Yazhuo Niu, Chiyang Liu, G.R. Shi, Jincai Lu, Wei Xu, Jizhong Shi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Upper Paleozoic sedimentary sequence in the Beishan Region, northwest China, provides a complete record of the complex amalgamation and extension history of the Central Asian Orogenic Belt (CAOB) for this part of China. Integrating newly obtained stratigraphic, paleontological and radiometric data, this paper reviews the Upper Paleozoic stratigraphic sequences of the Beishan Region. The Upper Paleozoic strata here are divided into three megasequences (MS). They are, in ascending order: Devonian, Mississippian–Guadalupian and Lopingian megasequences (MS1, MS2, and MS3), separated by two major unconformities each indicative of a huge sedimentary hiatus. MS1 is made up of continental and epicontinental marine deposits in the pre-rift stage; MS2 of transgressive marine and volcanic strata in the syn-rift stage; and MS3 of continental sediments in the inversion stage. The major unconformity between MS1 and MS2 is interpreted to represent the regional uplift and erosion caused by the final amalgamation of CAOB in the Beishan Region. The syn-rift MS2 represented by transgressive marine and volcanic strata in the Beishan Region can be well-correlated with Pennsylvanian–Guadalupian megasequences in Inner Mongolia, where they rest on a major interregional unconformity. This correlation suggests the closure of the Paleo-Asian Ocean in Beishan and Inner Mongolia before the Carboniferous, followed by the development of a synchronous marine rift megasequence in the southern part of the CAOB.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302414-fx1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences, Volume 170〈/p〉 〈p〉Author(s): Khalil Sarkarinejad, Farzane Goftari〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Our understanding of the geological structures and kinematics of thick-skinned and thin-skinned tectonics during the evolution of an orogenic system is strongly related to field evidence of décollement-dominated tectonics or deformation involving the entire middle and lower continental crust. In this paper, we compare thin-skinned and thick-skinned deformation of the Zagros orogen from small to large-scales. In the foreland thin-skinned region sedimentary rocks with several décollement horizons have undergone in-sequence thrusting with dominant NW-striking, NE-dipping and SW-verging displacement. The gneissic basement of the foreland underwent Permo-Triassic rifting and the normal faults were reactivated as thrust or strike-slip faults during subduction-to-collision orogenic system. There is no field exposures of deformed basement windows in this external part of orogen. However, in the internal parts of the orogen, the newly recognized hinterland fold-and-thrust belt and slate belt, there are outcrops of gneissic basement slices, mylonitic shear zones, and granite-gneissic flow. The Tutak granite-gneiss dome is associated with sole thrusts. Therefore, it contains deformed margins of both continents. Thus in deformation in this part of the orogen was thick-skinned. Measurements of quartz c-axis opening angles of the exhumed mylonite nappes document high temperature (∼642°±43° and ∼424°±31 °C). Relationship between kinematic vorticity number (Wk = Wm = 0.76 ± 0.06) of the mylonite nappes which are related to the hinterland fold-and-thrust belt indicate 55 ± 7.8% simple shear and 45 ± 7.4% pure shear components for instantaneous 2D flow which indicate sub-simple shear deformation. On the more thickened side of the Zagros deformed basement-involved contains continuous to discontinuous shear-band boudins of eclogite and slices of blue schist. This provide kinematic indicators suggesting simultaneous dip-slip and strike-slip and shear zones accelerating inclined lateral exhumation of the high-pressure metamorphic rocks of oceanic and continental crustal origin. Both the thin and thick-skinned portions of the Zagros on three major cross sections indicate the intensity of deformation in the NW and SE parts of the belt that display the opposite senses of shear on the two sides. We infer that both senses of shear were developed coevally under a bulk sub-simple shear, regional-scale deformation along a curved inclined transpression. Study of crustal-scale cross sections of the Paleozoic and Mesozoic sequences shows that asymmetrical to symmetrical folding an d thrusting in the central part of the Zagros foreland fold-and-and-thrust belts in the Fars area are gentle in comparison with those in the SE and NW of the orogen. The highest intensity of deformation occurs in the rotated asymmetrical folding and thrusting near the Bandar Abbas Syntaxis.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018304449-ga1.jpg" width="331" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 18 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Quanshu Yan, Susanne Straub, Xuefa Shi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Post-spreading intraplate volcanism has widely affected the South China Sea (SCS) region including Indochina, the northern margin of the SCS, and the SCS basin itself. In the SCS basin, several off- and on-fossil spreading center seamounts formed between 3.8 and 7.9 Ma. Based on previously published geochemical and Sr-Nd-Pb isotopic data, the intraplate volcanism is widely related to the Hainan mantle plume, whose existence has been evidenced by recent geophysical studies. To test this petrogenetic model, new Hf isotope data have been obtained from volcanic rocks from a suite of compositionally representative seamounts in the SCS basin. Compared to published Nd isotope ratios (0.512675–0.512965, 5 εNd units), 〈sup〉176〈/sup〉Hf/〈sup〉177〈/sup〉Hf ratios span a much larger range (0.282876–0.283097, 8 εHf units), even within individual seamounts (e.g., Zhangzhong seamount). These features, combined with previous studies, clearly confirm mantle heterogeneity beneath the SCS region. Similar to the trends in Sr-Nd-Pb isotope space, Nd-Hf isotope ratio show a relatively narrow, elongate mixing trend between a depleted Indian MORB-type mantle endmember and an enriched EMII-type mantle end member. We propose that this narrow trend is inconsistent with the origin of the enriched end member from a heterogeneous sub-continental lithospheric mantle (SCLM) and instead suggests a plume-related origin. As a conceptual model for the post-spreading tectonic scenario of the Hainan plume affecting the SCS region, we propose that a plume ascends to the bottom of the lithosphere beneath Hainan and its northern Leizhou peninsula at the northern margin of SCS, from where it migrates along sloping rheologic boundary layers to lithospheric faults under an extensional setting towards the central SCS where the magmas erupt at the young spreading centers.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302499-fx1.jpg" width="456" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Miao Dong, Jian Zhang, Shi-Guo Wu, Bei-Yu Wang, Yi-Fei Ai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Throughout the Late Cretaceous and Cenozoic, the Nansha Block experienced stretching and extension and moved southwards away from the South China continent. As an exotic micro-continent, the Nansha Block has markedly different lithospheric rheological properties from its surrounding regions. The temperature represents one of the key parameters controlling the dynamics and rheological behaviors of the lithosphere and mantle. Therefore, we calculated the 3D temperature field of the crust and upper mantle beneath the Nansha Block using two methods, namely, solving the heat conduction equation and inverting the 〈em〉S〈/em〉-wave velocity structure. The results show that the ratio of the crustal heat flow to the seafloor heat flow is greater than 50% in the central Nansha Block. The crustal temperatures in the Nansha Block are low. The temperature at the Moho discontinuity is approximately equal to the Curie temperature (523 °C). The temperatures of the shallow mantle (50 km) beneath the Nansha Block (800 °C) are lower than those of the surrounding areas. However, the cool mantle below the Nansha Block gradually transitions into a warm mantle with increasing depth. At a depth of 150 km, the mantle temperatures beneath the Nansha Block (1600 °C) are higher than those of the surrounding areas. The bottom boundary of the “thermal” lithosphere beneath the Nansha Block is at approximately 100 km, which is deeper than that in the surrounding areas. This result is different from the bottom boundary of the “seismic” lithosphere at a depth of 80 km under the Nansha Block, which is similar to that in the surrounding areas. The low lithospheric temperatures beneath the Nansha Block imply that the lithosphere of the Nansha Block experienced a rapid cooling process.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302293-fx1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 4 June 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Jungang Peng, Jianguo Li, Sam M. Slater, Qianqi Zhang, Huaicheng Zhu, Vivi Vajda〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present vegetation reconstructions based on an almost complete succession through the Triassic of Tulong, Nyalam County, southern Xizang (Tibet), China. The Permian and earliest Triassic samples were barren of palynomorphs, however, in overlying strata we identified well-preserved and diverse miospore assemblages. Seven pollen and spore zones spanning the Olenekian to the Rhaetian were recognized. These palynological zones were amalgamated into three floral stages that comprise distinct vegetation types: (1) an early Olenekian lycophyte-dominated flora with common pteridosperms, indicative of a warm and dry climate; (2) a late Olenekian transitional flora composed of abundant conifers with low abundances of lycophytes, signifying a decrease in temperature and increase in humidity; (3) a Middle to Late Triassic mature conifer-dominated flora with diverse sphenophytes, ferns and cycadophytes, indicative of a stable, temperate and humid climate. The changes in vegetation and climate tentatively correlate with the rifting of northern Gondwana, suggesting that regional tectonics was a contributive driving factor to local floral community change.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S136791201830227X-fx1.jpg" width="191" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 10 July 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Xin Rao, Jingeng Sha, Bo Peng, Xiaolin Zhang, Huawei Cai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We employed a novel approach using the bipolar and tropical distributions of bivalves to track the northward drift of the Indian Plate. The Kimmeridgian–Tithonian 〈em〉Retroceramus〈/em〉, Tithonian 〈em〉Anopaea〈/em〉 and 〈em〉Buchia〈/em〉, and Aptian–Cenomanian 〈em〉Aucellina〈/em〉 were mainly restricted to areas poleward of 30°N and 30°S, but middle Oxfordian–latest Cretaceous rudist bivalves were mainly restricted to areas between the paleolatitudes 30°S and 30°N. The distributions of these paleolatitude indicators in late Mesozoic time record five major drifting phases of the northward translation of the Indian Plate. In the Late Jurassic–earliest Cretaceous, the Indian Plate was a part of Gondwana, and various bipolar bivalves were present. During the Aptian–Albian interval, the Indian Plate was separated from Gondwana, but most parts of this plate were still under cold water, likely south of 30°S, and even at higher latitudes, because bipolar bivalves still existed at the northern margin of this plate, in the Tethyan Himalaya. In the Cenomanian, the northern part of the Indian Plate translated north into a warm/subtropical environments, north of 30°S, but southern India was still in a cold region, south of 30°S, as evidenced by 〈em〉Aucellina〈/em〉, which had already disappeared from the northern part of the Indian Plate, but still survived in southern India. In the latest Campanian, at least the Tethyan Himalaya of the northern margin of the Indian Plate had drifted into the area north of 30°S, based on the appearance of 〈em〉Bournonia haydeni〈/em〉 then in Tibet. Rudists occupied both the northern (Tethyan Himalaya) and southern (southern India) parts of the India Plate by the Maastrichtian, which demonstrate that the Indian Plate completely entered the tropical area, and roughly coincided with the initial collision between the Indian and Eurasian continents around the Maastrichtian–Paleocene.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302761-fx1.jpg" width="143" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Crystal Growth, Volume 507〈/p〉 〈p〉Author(s): Mengxing Lin, Yuanyi Wu, Sohrab Rohani〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For pharmaceutical crystallization design and control, the kinetics of nucleation and growth of crystals are significant parameters, especially for the system exhibiting polymorphic transformation. In this study, imatinib mesylate, whose solubility, nucleation and growth kinetics are lacking in the literature, was thoroughly explored in the aspects of characterization, solubility and polymorphic transformation, and evaluation of nucleation and growth rate. Two forms of imatinib mesylate, α and β, were characterized by X-ray powder diffraction, scanning electron microscopy and differential scanning calorimetry. The solubility measurement of the two forms was performed with ultraviolet–visible spectroscopy in three solvents from 278.15 to 333.15 K at atmospheric pressure. The results indicated the β-form is more stable in methanol,1-propanol, and 2-propanol under the experimental condition. The solubility order is methanol 〉1-propanol 〉2-propanol. The solvent-mediated polymorphic transformation (SMPT) of imatinib mesylate from 〈em〉α〈/em〉-form to 〈em〉β〈/em〉-form was studied with the in-situ Raman spectroscopy and conductivity meter. It is found that the SMPT process of imatinib mesylate from 〈em〉α〈/em〉-form to 〈em〉β〈/em〉-form in methanol is controlled by nucleation and growth of 〈em〉β〈/em〉-form. Finally, the nucleation and grow rate of 〈em〉β〈/em〉-form of imatinib mesylate were estimated by minimizing the difference between the calculated and experimental solution concentration with MATLAB optimization function.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences, Volume 169〈/p〉 〈p〉Author(s): Xiaozhuang Cui, Jian Wang, Zhiming Sun, Wei Wang, Qi Deng, Guangming Ren, Shiyong Liao, Mingda Huang, Fenglin Chen, Fei Ren〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The early Paleoproterozoic is an essential period for understanding the early tectonic evolution of the Yangtze Block and its reconstruction in the Columbia supercontinent, whereas these issues are largely unknown due to the scarce preservation of early Paleoproterozoic geological records. This study presents rarely reported early Paleoproterozoic granitoids from the southwestern Yangtze Block, with integrated studies of zircon U-Pb ages, Lu-Hf isotopic compositions and whole-rock geochemistry. Magmatic zircon U-Pb dating for two monzogranite samples yields weighted mean 〈sup〉207〈/sup〉Pb/〈sup〉206〈/sup〉Pb ages of 2359 ± 16 Ma and 2363 ± 16 Ma, providing unambiguous evidence for the presence of early Paleoproterozoic magmatism in the Yangtze Block. All the samples have high A/CNK values of 1.30–1.61, typical of S-type granite. These rocks have low total REE contents of 72.5–139.0 ppm with marked enrichment in LREEs ((La/Yb)〈sub〉N〈/sub〉 = 10.73–23.83) and conspicuously negative Eu anomalies (Eu/Eu〈sup〉*〈/sup〉 = 0.46–0.55). The rocks exhibit uniform primitive mantle-normalized trace element patterns with enrichment in Rb, Th, U and Pb and depletion in Sr, Nb, Hf and Ti. These dated zircon grains have consistent negative 〈em〉ε〈/em〉〈sub〉Hf〈/sub〉(〈em〉t〈/em〉) values of −6.2 to −2.8 and 〈em〉T〈/em〉〈sub〉DM2〈/sub〉 ages of ca. 2.97–3.16 Ga, indicative of Mesoarchean crustal materials as their magma source. Considering the existence of the ca. 2.36 Ga regional high-grade tectono-metamorphic event, we propose that the ca. 2.36 Ga monzogranites were most likely generated in the early stage of post-collisional extension. Therefore, the southwestern Yangtze Block likely experienced a collision event during ca. 2.40–2.36 Ga, indicative of the involvement of the Yangtze Block in the ca. 2.5–2.3 Ga Arrowsmith orogeny of Laurentia. In addition, a series of accretionary events might also have occurred in the western Yangtze Block before the final assembly of the Columbia supercontinent, implying a tight spatial connection between the Yangtze Block and northwestern Laurentia within this global-scale supercontinent.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018304498-ga1.jpg" width="308" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 5 July 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences〈/p〉 〈p〉Author(s): Caineng Zou, Zhi Yang, Rukai Zhu, Songtao Wu, Jinhua Fu, Dewen Lei, Lianhua Hou, Senhu Lin, Songqi Pan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Crude oil in unconventional shale systems, present as tight oil and shale oil, accumulates inside an oil kitchen in formations with coexistent sources and reservoirs. Organic matter present in oil shale is not yet mature and requires heating to convert it into crude oil. Oil exploration in shale systems involves the exploration of shale oil retained in source rocks and tight oil rich zones located near source rocks. Tight oil is a type of realistic unconventional oil resources in China. The marked increase in potential shale oil reserves, and exploration of these reserves, will result in a shale oil revolution similar to that experienced for shale gas. Based on a systematic comparison of geologic features of shale systems in the US and China, the geologic significance of the sweet spots in shale systems is proposed. This zone contains an abundance of unconventional oil in shale systems that can be explored and developed under current economic and technical conditions. The sweet spot zone refers to the zone in the tight oil rich zone which has industrial value within the scope of matured high-quality source rocks on the plane. The sweet spot interval refers to the high-productivity interval of tight oil which has industrial value through artificial stimulation. The main aim of oil exploration in shale formations is to identify the sweet spots. The distribution of the economic sweet spots in shale systems is evaluated by overlapping the geologic, engineering and economic sweet spots. Resource assessment techniques, the identification of logging data properties, high-resolution 3D seismic surveys, horizontal well production from well pads, and artificial reservoir development of sweet spots in oil-bearing shale formations can assist efficient development of oil. Globally, shale formations contain a significant volume of oil reserves. Currently, stimulated reservoir volume (SRV) techniques in horizontal wells in marine shale gas formations in the United States have average peak-productivity cycles of 10–15 years. To achieve commecial oil production in lacustrine shale systems in China, it is important to utilize large formation thicknesses and the high abundance of organic matter. In addition, the development of practical and economic techniques will result in an increase of productivity of tight oil and shale oil by 30–50 million tons, as well as the economic development of oil in lacustrine shale systems in China.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉Tight oil and shale oil are the important unconventional resources in shale systems, in which the tight oil is the most realistic and profitable resources. Due to special geological environments, lacustrine tight oil is different from marine tight oil in North America. Sweet-spotting is critical to develop these abundant resources, in which three aspects including geology, engineering and economy have been taken into consideration. In this paper, we proposed the definition of sweet spot zone and sweet spot interval in shale system, and discuss the geological significance & related technologies. Tight oil and shale oil should be assessed as a whole system during the future geological evaluation and technology development. The productivity of tight oil and shale oil will be increased by 30–50 million tons, making the economic development of oil in continental shale systems in China.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018302670-fx1.jpg" width="136" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈span〉〈div〉Summary〈/div〉The strength of the lithosphere plays a key role in the formation and evolution of tectonic plate boundaries. Localized lithospheric deformation associated with plate tectonics requires a mechanism for weakening across the entire width of the lithosphere, including the strongest cold ductile region. We explore the microphysics of weakening of lithospheric materials, and in particular the coupled evolution of mineral grain size and intragranular defects and their control on lithospheric strength. We propose a model for the interaction between grain-boundaries and dislocation density to reduce the net free energy of grains during dynamic recrystallization (DRX). The driving forces for DRX arise from heterogeneity in dislocation density and grain boundary curvature. Our model shows that grain growth driven by variation in grain boundary curvature can be impeded by variation in dislocation density; this occurs because as the grains grow, to minimize their surface energy, their dislocation density and associated internal energy may increase and offset the driving forces for grain growth. The correlation between grain size and dislocation density can for example arise because the dislocation accumulation in smaller grains is suppressed due to the large stress that is needed to bend and elongate a short dislocation (as dictated by the small grain size), while the larger grains can have long dislocations and reach a steady state dislocation density dictated by the applied stress. In a lithospheric setting, slower grain growth means that it would require less mechanical work to establish weak localized shear zones through grain damage, and retard the healing of previously damaged zones. Furthermore, the competition of two different time-scales - that of grain growth and the dislocation kinetics - can lead to oscillating behavior over 1 to 10 years as the grain size and dislocation density advance towards their steady states. These oscillations are likely to have an effect on the rheology of lithospheric rocks, e.g. their strengthening and weakening through time, and have a potential application to geological processes such as postseismic creep in ductile shear zones.〈/span〉

Description: 〈p〉Publication date: Available online 31 October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Soils and Foundations〈/p〉 〈p〉Author(s): Jiangu Qian, Zibo Du, Xilin Lu, Xiaoqiang Gu, Maosong Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A series of cyclic torsional shear tests using hollow cylinder apparatus (HCA) were performed to investigate the effect of principal stress rotation (PSR) on the stress–strain behaviors of saturated soft clay. The traffic–load–induced shear stress path was used in the cyclic test and the investigation mainly concerned the influence of PSR on the shear stiffness and non-coaxiality. It indicated that the effects of PSR substantially depends on the magnitude of deviatoric stress (〈em〉q〈/em〉 = {[(〈em〉σ〈/em〉〈sub〉1〈/sub〉 − 〈em〉σ〈/em〉〈sub〉2〈/sub〉)〈sup〉2〈/sup〉 + (〈em〉σ〈/em〉〈sub〉2〈/sub〉 − 〈em〉σ〈/em〉〈sub〉3〈/sub〉)〈sup〉2〈/sup〉 + (〈em〉σ〈/em〉〈sub〉1〈/sub〉 − 〈em〉σ〈/em〉〈sub〉3〈/sub〉)〈sup〉2〈/sup〉]/2}〈sup〉1/2〈/sup〉) as well as the intermediate principal stress ratio (〈em〉b〈/em〉 = (〈em〉σ〈/em〉〈sub〉2〈/sub〉 − 〈em〉σ〈/em〉〈sub〉3〈/sub〉)/(〈em〉σ〈/em〉〈sub〉1〈/sub〉 − 〈em〉σ〈/em〉〈sub〉3〈/sub〉)). At low deviatoric stress, the trajectory envelope of deviatoric strain path translates with a nearly constant size, showing constant shear stiffness and strong non-coaxiality. However, at high deviatoric stress, the trajectory envelope of deviatoric strain rapidly expands towards instability, showing degenerating shear stiffness and weak non-coaxiality. Moreover, the excess pore water pressure increases and the shear stiffness decreases more rapidly as 〈em〉b〈/em〉 value increases. The results can provide an experimental basis for constitutive modelling of clays under traffic–induced loadings.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Atmospheric and Solar-Terrestrial Physics, Volume 182〈/p〉 〈p〉Author(s): K. Nithya, Ajil Kottayil, K. Mohanakumar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A Stratosphere-Troposphere (ST) wind profiler radar at 205 MHz is operational at Cochin (10.04 N; 76.44 E), India since January 2017 and is providing accurate three-dimensional wind profiles for an altitude range of 315 m to 20 km. In this paper, we present a method to estimate the tropopause altitude from signal to noise ratio (SNR) profiles obtained from the 205 MHz wind profiler radar. The gradient in SNR is used to estimate the cold point tropopause (CPT) height. The CPT height obtained from the ST radar is validated against co-located radiosonde tropopause height measurements and is found to be in very good agreement. The variability of CPT height during monsoon season was studied and the factors responsible for its variability were investigated. It is found that during monsoon season the Tropical Easterly Jet (TEJ) has an inverse relationship with the CPT height, i.e. CPT height increases as the strength of TEJ diminishes and vice versa. A comparison between TEJ core speed and ice cloud water path (ICWP) which represents the strength of deep convection, shows that ICWP decreases as the strength of TEJ increases. Thus, our analysis shows that TEJ affects the tropopause height through changing the concentration of ice clouds.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Earth and Planetary Science Letters, Volume 506〈/p〉 〈p〉Author(s): Rajeev Kumar Yadav, Vineet K. Gahalaut, Amit Kumar Bansal, S.P. Sati, Joshi Catherine, Param Gautam, Kireet Kumar, Naresh Rana〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉No great earthquake has occurred in the Garhwal–Kumaun region of NW Himalaya in the past 500 years or more. We report results of continuous GPS measurements from 28 sites from the region to suggest that the convergence rate in this part of the Himalaya is about 18 mm/yr which is leading to strain accumulation in the region. The Main Himalayan Thrust (MHT) in the frontal part of the Himalaya under the Outer and southern Lesser Himalaya is strongly coupled for a width of about 85 km. The midcrustal ramp where earthquakes of Himalayan seismic belt occur, exhibits low coupling. Strong coupling on the MHT beneath the Outer and Lesser Himalaya is homogeneous except in the very shallow updip part of the MHT. Subduction of sediments of the Indo-Gangetic plains or the Delhi Hardwar ridge does not seem to influence coupling. A high rate of strain accumulation, which has continued for more than 500 years on a strongly coupled MHT makes this one of the most earthquake-vulnerable segments of the Himalayan arc.〈/p〉〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈/p〉〈/div〉 〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0012821X18306198-gr001.jpg" width="458" alt="Graphical abstract for this article" title=""〉〈/figure〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Crystal Growth, Volume 507〈/p〉 〈p〉Author(s): Veronika D. Grigorieva, Vladimir N. Shlegel, Nina V. Ivannikova, Tatyana B. Bekker, Alexander P. Yelisseyev, Artem B. Kuznetsov〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For the first time Na〈sub〉2〈/sub〉Mo〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 crystals were grown by Czochralski technique in low-thermal-gradient conditions (LTG Cz), which allowed obtaining crystals of record size (100 (D) × 45 (L) mm〈sup〉3〈/sup〉) and optical quality. Influence of growth rate and seed direction on crystal morphology was studied, optimal growth conditions were determined. Three cleavage planes: (0 1 0), (0 0 1) and (0 2 1), were detected. Different characterizations of Na〈sub〉2〈/sub〉Mo〈sub〉2〈/sub〉O〈sub〉7〈/sub〉 crystal samples, such as: transparency, photoluminescence, thermostimulated luminescence and Raman spectra were studied.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 1 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Crystal Growth, Volume 507〈/p〉 〈p〉Author(s): X.F. Liu, G.G. Yan, Z.W. Shen, Z.X. Wen, J. Chen, Y.W. He, W.S. Zhao, L. Wang, M. Guan, F. Zhang, G.S. Sun, Y.P. Zeng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Although homoepitaxial growth of multiple 4H-SiC wafers in one run can be realized in commercial specialized chemical vapor deposition equipment, wafers must be loaded onto a rotatable large susceptor and overspread on it, which leads to the diameter of the susceptor increases as the number or the total area of the epitaxial wafer increases. in this work, we demonstrated a facile method for growth of multiple 4H-SiC wafers assembled in a simple holder via a home-made single-wafer conventional chemical vapor deposition equipment without a large susceptor. The structural properties of the obtained 4H-SiC films on each wafer were investigated by means of optical microscope, AFM, SEM and Raman. Results showed that high quality of homogeneous 4H-SiC film was epitaxially grown on the inner region of each wafer, while on the outer region, influenced by the mechanical parts of the simple holder, the quality was degraded. At last we draw a prospective on homoepitaxial growth of whole wafer through further reducing the adverse outer region via advanced holder and wafer assembly, which could greatly improve production efficiency and reduce energy consumption.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 International Journal of Rock Mechanics and Mining Sciences, Volume 112〈/p〉 〈p〉Author(s): Pei-Qi Ji, Xiao-Ping Zhang, Qi Zhang〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The existence of micro cracks inside rocks influences the rock strength and deformation significantly and controls the presence of crack closure stage under compression. However typical discrete element method (DEM) fails to model the gradual crack closure behavior of rock due to insufficient consideration for pre-existing micro-cracks. The stress-strain curves simulated in previous DEM are usually linear in initial stage until numerous cracks are induced under stress. Thus a new method implemented in Discrete Element Method is proposed to model the crack closure behavior of rocks under uniaxial compression. The pre-existing micro-cracks inside the rock sample are created and opened by introducing two notional contact surfaces and giving a negative reference gap. These opened cracks are gradually closed under stress as the adjacent discs sustain sufficient relative movement (re-contact). Thus the gradual crack closure behavior of rock under compression is reproduced. The crack distribution respect to the crack orientation is described with the crack tensor analysis to consider the effect of crack density and anisotropy. Three factors including crack intensity, crack orientation and crack gap are discussed with parametric study to study their influence on the crack closure behavior. The effects of pre-existing cracks on the properties of rocks (such as rock strength, Young's modulus, crack closure stress levels) are also analyzed, and are in well agreement with observations by experiment. A little modification is made to previous calibration process to consider the crack closure stage of rock. Finally two types of rocks including limestone and granite are calibrated and compared to the experiment results. The simulated stress-strain curves match the curves of experiment, especially the initial crack closure segment perfectly, which validates the proposed method.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geomorphology, Volume 327〈/p〉 〈p〉Author(s): Chenge An, Gary Parker, Marwan A. Hassan, Xudong Fu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Massive bed degradation (20 m in 7 years) has been observed in the Shi‑ting River, Sichuan Province, China, since the 2008 Wenchuan Ms. 8.0 earthquake. The reason for the massive bed degradation has not been well understood. A hypothesis has been proposed that relates bed degradation to the augmentation of sand supply after the earthquake. The effect of sand on gravel mobility (〈em〉magic sand〈/em〉 effect) has long been observed in laboratory experiments. In this paper, we study whether the augmentation of sand supply and its 〈em〉magic sand〈/em〉 effect can lead to the observed massive degradation at decadal scales. A one-dimensional river morphodynamic model is implemented to study the problem in general at field scale and in context of the gravel-bed Shi‑ting River. Sediment transport is calculated with the Wilcock and Crowe (2003) relation, in which the 〈em〉magic sand〈/em〉 effect is explicitly embedded in terms of a function relating reference Shields number to the surface sand fraction. We find that the augmentation of gravel supply leads to bed aggradation, whereas the augmentation of sand supply can indeed lead to bed degradation and surface fining. The magnitude and timescale of bed degradation are not sensitive to the sand supply rate but are sensitive to the flood intermittency factor〈sub〉,〈/sub〉 i.e., the fraction of time the river is in flood. However, an unrealistic flood intermittency factor (≥0.3) would be required in order to match the observed timescale of bed degradation, thus indicating that the 〈em〉magic sand〈/em〉 effect might not be the governing reason for massive bed degradation in the Shi‑ting River, and by implication in gravel-bed rivers in general. Our simulation results also indicate that despite the fact that 〈em〉magic sand〈/em〉 effects are not explicitly included in most sediment transport relations, they are at least partly built in via the hiding function that is contained in most sediment transport relations for gravel-sand mixtures. While here we use the Shi‑ting River as an example, our results have applicability to gravel-bed rivers subjected to augmentation in sand supply in general.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 15 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geomorphology, Volume 327〈/p〉 〈p〉Author(s): Hakan Tanyas, Mauro Rossi, Massimiliano Alvioli, Cees J. van Westen, Ivan Marchesini〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Rapid assessment of spatial distribution of earthquake-induced landslides could provide valuable information in the emergency response phase. Previous studies proposed global analyses with the aim of predicting earthquake-induced landslide distributions in near real-time. However, in all those studies, mapping units are constituted by pixels, which do not reflect homogeneously distributed physical property for a given terrain unit and whose size do not match the resolution of existing thematic data at global scale. Moreover, none of the existing analyses considers sampling balance between different inventories or categorizing the inventories to construct a training set with higher statistical representativeness. We develop an improved global statistical method to address these drawbacks. We use slope units, which are terrain partitions attributed to similar hydrological and geomorphological conditions and to processes that shape natural landscapes. A set of 25 earthquake-induced landslide-events are selected and categorized based on the similarity between causal factors to determine the most relevant training set to make a prediction for a given landslide-event. As a result, we develop a specific model for each category. We sample an equal number of landslide points from each inventory to overcome the dominance of some inventories with large landslide population. We use seven independent thematic variables for both categorizing the inventories and modeling, based on logistic regression. The results show that categorizing landslide-events introduces a remarkable improvement in the modeling performance of many events. The categorization of existing inventories can be applied within any statistical, global approach to earthquake-induced landslide events. The proposed categorization approach and the classification performance can be further improved with the acquisition of new inventory maps.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of South American Earth Sciences, Volume 88〈/p〉 〈p〉Author(s): Erick Juárez-Arriaga, Harald Böhnel, Gerardo Carrasco-Núñez, Ahmed Nasser Mahgoub〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Los Humeros caldera in eastern Mexico has been formed since about 164 ka, with important effusive activity during the upper Holocene, which covered more than 100 km〈sup〉2〈/sup〉 with lava. Two lava flows were 〈sup〉14〈/sup〉C dated at 2692-1950 cal BCE and 1117-930 cal BCE, but the detailed succession of eruptions is yet unknown even though the interest for volcanic risk assessment. All Holocene lava flows were studied paleomagnetically in 22 sites to determine which of them have been contemporaneous and to apply the paleomagnetic dating method. For most sites well defined mean directions could be defined, resulting in an overall paleodirection of D = 7.7° E, I = 16.9°, α〈sub〉95〈/sub〉 = 6.7°. This direction is discordant compared to the geocentric axial dipole field and indicates that secular variation has not averaged out. Paleointensities were obtained using the Thellier IZZI protocol, with only a small success rate of 27% due to thermally induced alterations, the presence of multidomain magnetic minerals, or unstable paleomagnetic directions as indicated by the checks during the experiments. Accepted paleointensities of 37 samples varied between 21 and 63 μT, with site mean paleointensity of 27–54 μT. The F-test was applied to mean directions of sites potentially belonging to the same lava flow, and if these were indistinguishable they were combined in flow mean paleomagnetic directions. Otherwise, these sites were assumed to represent independent eruptions. This way, thirteen independent flow mean directions were obtained and used for paleomagnetic dating by means of the SHA.DIF.14k reference model and the archaeo_dating software. The dating often provided several possible age ranges, and erosion state, soil cover, lava flow contacts, and the available 〈sup〉14〈/sup〉C ages were used all together for selecting the most probable age range. Two well defined eruptive periods bracketed between 2500 and 1900 BCE, and 1300-600 BCE were defined, suggesting that all studied lava flows were emplaced during two main eruptive phases, which may indeed have been much shorter than 600 years. Paleomagnetic data support those eruptive periods and time among the different lava flow units can be inferred from those data. Early settlers occupied this region since about 2000 BCE and thus were certainly affected by these voluminous eruptions. At least another 12 nearby Holocene monogenetic volcanoes are known in the surrounding area, and all together these eruptions indicate that this is a highly active volcanic region, which might be affected by eruptions in the near future.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 30 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology, Volume 501〈/p〉 〈p〉Author(s): 〈/p〉

Description: 〈p〉Publication date: Available online 18 August 2017〈/p〉 〈p〉〈b〉Source:〈/b〉 Chemical Geology〈/p〉 〈p〉Author(s): C.C. Bicalho, C. Batiot-Guilhe, J.D. Taupin, N. Patris, S. Van Exter, H. Jourde〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Geochemical and isotopic tracers (δ〈sup〉18〈/sup〉O, δ〈sup〉2〈/sup〉H, 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr and δ〈sup〉13〈/sup〉C〈sub〉TDIC〈/sub〉) were used to constrain origins and chemical evolution of groundwater in a Mediterranean karst system. The Lez spring is the main perennial outlet of this karst system and supplies the metropolitan area of Montpellier (southern France) with drinking water. Groundwater samples were collected at the Lez spring and surrounding springs and wells under different hydrodynamic conditions during two hydrological years, from June 2008 until May 2010. The results show that multiple hydrological compartments interact through an important network of fractures and faults. They notably reveal connections between the main Jurassic limestone aquifer and the overlying Cretaceous (Valanginian) compartment, and between the surface and deep levels of the karst system. Isotopic tracers provided information about atmospheric recharge origins, lithological signatures and chemical evolution of waters. Long residence-time groundwaters, issued from deep layers have a Triassic hydrochemical fingerprinting, being enriched in δ〈sup〉13〈/sup〉C〈sub〉TDIC〈/sub〉 and characterized by high concentrations in Cl〈sup〉−〈/sup〉 as well as high Sr/Ca, Mg/Ca and 〈sup〉87〈/sup〉Sr/〈sup〉86〈/sup〉Sr ratios. Evidences suggest that these waters mix with waters from the lower layers of the main Jurassic aquifer constitute an intermediate storage compartment prone to rise through piston-flow mechanism. A two-end member hydrograph separation based on EC-TDS was used to determine the proportion of the deep compartment's contribution to the Lez spring outflow. On average over the study period, the main aquifer compartment and the deep aquifer compartment are estimated to contribute 92.6% and 7.4% of groundwater flow at the Lez spring, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Physics of the Earth and Planetary Interiors, Volume 286〈/p〉 〈p〉Author(s): Oleg L. Kuskov, Ekaterina V. Kronrod, Victor A. Kronrod〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The main purpose of the present study is to evaluate the lunar bulk composition (BSM) and the composition of a three-layer mantle based on a joint inversion of lunar mass and moment of inertia, and the mantle seismic velocity profiles in combination with Gibbs free energy minimization. As an integral characteristic of the thermal state, the mean volume temperature 〈em〉T〈sub〉mean〈/sub〉〈/em〉 of the lunar mantle controlling the mineral composition of the Moon was chosen. In terms of 〈em〉T〈sub〉mean〈/sub〉〈/em〉, all thermal models can be conditionally divided into “cold” ones with 〈em〉T〈sub〉mean〈/sub〉〈/em〉 ∼ 690–860 °C and “hot” ones with 〈em〉T〈sub〉mean〈/sub〉〈/em〉 ∼ 925–1075 °C. We find that irrespective of the thermal state, BSM is characterized by practically constant values of bulk FeO ∼ 12–13 wt% and Mg# 80–81.5, which indicates a significant difference in the composition of the silicate Earth (BSE) and its satellite. The FeO content of 11–14 wt% and Mg# 80–83 are approximately identical in the upper and lower mantle. The bulk SiO〈sub〉2〈/sub〉 abundance depends little on the thermal state and ranges from 45 to 52 wt%, with probable concentrations of SiO〈sub〉2〈/sub〉 being 50–55% in the upper mantle and 45–50 wt% in the lower mantle; orthopyroxene, and not olivine, is the predominant mineral of the upper mantle. On the contrary, the lunar abundance of alumina, depending on the thermal state, falls into two different groups. Cold models of BSM with a content of 3–4.6 wt% Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 are comparable to those of BSE, whereas for hot models the bulk-alumina content can be in the range of 1.2–1.7 × BSE. The results indicate a tendency for a gradual increase in the alumina content with depth: from 1 to 2% in the upper mantle to 4–7 wt% Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 in the lower mantle with an increasing amount of garnet. The composition of the middle mantle remains controversial, since it may partially overlap with the compositions of the overlying and underlying shells. Our simulation results show that a chemically stratified lunar interior is consistent with the observations and has similar concentrations of FeO and MgO but different concentrations of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 and SiO〈sub〉2〈/sub〉 in different zones of the mantle. However, the question of the similarity and/or difference in the composition of the silicate Earth and its satellite with respect to the abundance of refractory elements, which is of fundamental importance for lunar geochemistry, remains unresolved and requires further research.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Precambrian Research, Volume 320〈/p〉 〈p〉Author(s): Zheng Gong, David A.D. Evans, Sten-Åke Elming, Ulf Söderlund, Johanna M. Salminen〈/p〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computers & Geosciences, Volume 122〈/p〉 〈p〉Author(s): Seth Goodman, Ariel BenYishay, Zhonghui Lv, Daniel Runfola〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Interdisciplinary use of geospatial data requires the integration of data from a breadth of sources, and frequently involves the harmonization of different methods of sampling, measurement, and technical data types. These integrative efforts are often inhibited by fundamental geocomputational challenges, including a lack of memory efficient or parallel processing approaches to traditional methods such as zonal statistics. GeoQuery (〈a href="http://geoquery.org/" target="_blank"〉geoquery.org〈/a〉) is a dynamic web application which utilizes a High Performance Computing cluster and novel parallel geospatial data processing methods to overcome these challenges. Through an online interface, GeoQuery users can request geospatial data - which spans categories including geophysical, environmental and social measurements - to be aggregated to user-selected units of analysis (e.g., subnational administrative boundaries). Once a request has been processed, users are provided with permanent links to access their customized data and documentation. Datasets made available through GeoQuery are reviewed, prepared, and provisioned by geospatial data specialists, with processing routines tailored for each dataset. The code used and steps taken while preparing datasets and processing user requests are publicly available, ensuring transparency and replicability of all data and processes. By mediating the complexities of working with geospatial data, GeoQuery reduces the barriers to entry and the related costs of incorporating geospatial data into research across disciplines. This paper presents the technology and methods used by GeoQuery to process and manage geospatial data and user requests.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Computers & Geosciences, Volume 123〈/p〉 〈p〉Author(s): Pouyan Pirnia, François Duhaime, Yannic Ethier, Jean-Sébastien Dubé〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The thermal, mechanical and hydrodynamic behaviour of porous media in geoscience applications is usually modelled through the finite-element (FEM) or finite-difference methods. These continuum models tend to perform poorly when modelling phenomena that are essentially dependent on behaviour at the particle scale or phenomena that are not accurately described by partial differential equations (PDE), such as internal erosion and filtration. The discrete nature of granular materials can be modelled through the discrete-element method (DEM). However, in some instances, DEM models would benefit from an interface with continuum models to solve coupled PDEs or to model phenomena that occur at a different scale. This paper introduces ICY, an interface between COMSOL Multiphysics, a commercial finite-element engine, and YADE, an open-source discrete-element code. The interface is centred on a JAVA class. It was verified using the simple example of a sphere falling in water according to Stokes’ law. For this example, the drag force was calculated in COMSOL and body forces (gravity, buoyancy and drag) on the sphere were summed in YADE. The paper also presents an application example for the interface based on the modelling of internal erosion tests.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0098300417313213-fx1.jpg" width="334" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉

Description: 〈p〉Publication date: 1 March 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Geoderma, Volume 337〈/p〉 〈p〉Author(s): Yang Ou, Alain N. Rousseau, Lixia Wang, Baixing Yan, Thiago Gumiere, Hui Zhu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In China, most riparian wetlands have undergone degradation and shrinkage, due to severe droughts or low hydrological connectivity. There are considerable studies focusing on the impact of water level on wetland vegetation; however, changes in the soil components, such as the microbial community, of wetlands following flooding remains unclear. Here, we verified the effects of an extreme flooding event on the soil physicochemical conditions, enzyme activities and soil microbial composition. Overall, we observed that the flooding event impacted the soil properties and modified the enzyme activities. Also, the flooding affected more the biomass than the composition of the soil microbial community. We observed that after the flooding event, manganese (Mn) replaced total nitrogen (TN) as one of the major governing factors of soil enzyme activities. Soil organic carbon (SOC), and pH were also correlated with soil enzyme activities before and after the flooding event. Soil conductivity (EC), C/N ratio, and iron (Fe) contents had a large influence on microbial communities. Nevertheless, the soil C/N ratio was the dominant governing factor of the microbial structure. Therefore, edaphic factors were remarkably related to microbial organisms as flooding was deemed a key driving factor to the linkage between them. The antecedent long-term drought provoked by human disturbance, and subsequent flooding (i.e., re-inundating) may thus damage the soil dynamics of riparian wetlands, and hence, altering the carbon storage capacity. The results of this study suggest that rehabilitating hydrological connectivity and promoting primary succession of vegetation could become effective practices for improving the soil ecosystem of riparian wetlands.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Sea Research, Volume 142〈/p〉 〈p〉Author(s): Catharina J.M. Philippart, Theo Gerkema, Henk W. van der Veer〈/p〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Dynamics of Atmospheres and Oceans, Volume 84〈/p〉 〈p〉Author(s): A. Lugo-Fernández〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The Loop Current (LC) intrusion into the Gulf of Mexico is analyzed using steady, 2-D nonlinear shallow water equations expressed in Cartesian and natural coordinates. The model suggests that the LC moves with constant relative vorticity along isopleths of the Bernoulli function B such that its surface area (A) has a steady dA/dt and frontal velocity. The intrusion is envisioned as an initial transport imbalance that creates volume storage within the Gulf. Because of the advection of relative vorticity, the intruding inflow splits into a northward flow on the west and a southward flow on the east. The storage creates a sea level difference across the LC that induces a northward force due to Coriolis. This force reinforces the northward flow but opposes the southward flow, helping store water inside the Gulf. This sea level difference is in addition to the one in the B field. The storage implies loss of kinetic energy, which creates a speed shear across the LC and gives rise to the small speed of the LC front. The relative vorticity equation in natural coordinates reveals three aspects of the LC: (1) a velocity difference across the LC, (2) a parabolic shape of the sea surface; and (3) a negative curvature of the LC meaning the velocity changes direction anticyclonically along the B-contours.〈/p〉〈/div〉

Description: 〈p〉Publication date: 15 November 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Volcanology and Geothermal Research, Volume 367〈/p〉 〈p〉Author(s): Millaray Curilem, Rodrigo Fernandes de Mello, Fernando Huenupan, Cesar San Martin, Luis Franco, Erasmo Hernández, Ricardo Araújo Rios〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The surveillance of active volcanoes around the world has become a critical security issue for many countries, requiring a continuous monitoring of seismic signals. By analyzing such signals, we intend to understand volcanic activities (e.g. explosions, eruptions and depressurization) and take decisions to reduce the effects and damages to the economy and society of nearby regions. Active volcanoes constantly produce signals, which may then be characterized as data streams, making impractical the presence of specialists to monitor and label every activity. To overcome this drawback, we present a new and straightforward approach to discriminate volcano seismic signals using spectrogram cross-correlations (SPCC) in conjunction with the K-Nearest Neighbors algorithm, a supervised machine learning strategy. Experiments were performed on signals collected from the Llaima volcano (Chile), and results confirmed the ability of our approach to discriminate events with a sensitivity over 95〈em〉%〈/em〉 for three out of the five classes considered.〈/p〉〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Atmospheric and Solar-Terrestrial Physics, Volume 181, Part B〈/p〉 〈p〉Author(s): Oksana Mandrikova, Yury Polozov, Nadezhda Fetisova, Timur Zalyaev〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, according to the ground observation data, we study the dynamics of the ionospheric parameters during periods of strong and moderate magnetic storm of 2015–2017. The study was carried out using new methods of modeling and data analysis proposed by the authors. Multicomponent model of ionospheric parameters presented in this work allows describing changes of the ionospheric parameters, both in the conditions of the calm ionosphere and in perturbed periods. During the study, we allocated ionospheric disturbances preceding and accompanying the periods of magnetic storms in analyzing regions. The analysis showed a high incidence of the effect of an increase in the electron concentration of the ionosphere preceding the onset of magnetic storms. Comparing the results of the study with cosmic ray data, we also noticed the correlation of effects in the ionosphere with the anomalous changes in the dynamics of cosmic rays.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 International Journal of Rock Mechanics and Mining Sciences, Volume 112〈/p〉 〈p〉Author(s): Jiateng Guo, Lixin Wu, Minmin Zhang, Shanjun Liu, Xiaoyu Sun〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We propose a new automatic methodology for identifying discontinuity traces directly from 3D point clouds of natural rocky slopes. The potential feature points of the discontinuity traces were detected based on a 1D truncated Fourier series. To extract trace points from the potential feature points, a curvature-weighted Laplacian-like smoothing technique was used to thin these points. Finally, the trace lines were constructed through a feature-parameter-weighted line growing algorithm. The effectiveness of the method was tested with four data sets. Additionally, the results of two of the data sets were compared with the results of CloudCompare and an existing method. Finally, the area density was calculated based on the extracted trace lines. The results show that the proposed discontinuity trace extraction method is fast, effective and automatic and has the potential for use as a supplement to traditional direct measurements of discontinuity traces, thereby providing important supplemental data for fracture related research.〈/p〉〈/div〉

Description: 〈p〉Publication date: October 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Hydrology: Regional Studies, Volume 19〈/p〉 〈p〉Author(s): José Bandeira Brasil, Eunice Maia de Andrade, Helba Araújo de Queiroz Palácio, Pedro Henrique Augusto Medeiros, Julio Cesar Neves dos Santos〈/p〉 〈h5〉Abstract〈/h5〉 〈div〉 〈h6〉Study region〈/h6〉 〈p〉Iguatu Experimental Basin, located in the semi-arid region of northeastern Brazil.〈/p〉 〈/div〉 〈div〉 〈h6〉Study focus〈/h6〉 〈p〉The aim of this study was to investigate the influence of rainfall characteristics on throughfall, stemflow and interception loss in a deciduous forest of a tropical semi-arid region, from a data series of eight consecutive years. The data were collected from 2010 to 2017, comprising a total of 225 events.〈/p〉 〈/div〉 〈div〉 〈h6〉New hydrological insights for the region〈/h6〉 〈p〉Among the variables used to characterize rainfall, the maximum 30-min intensity (〈em〉I30〈/em〉) best explained the interception losses, which is also well correlated to rainfall depth and event average intensity. The predominant events (67% of the total) are characterised by low rainfall depth, low 〈em〉I30〈/em〉 and higher interception loss (18% of the gross rainfall). In addition, there is a threshold between rainfall characteristics and the interception process: for rainfall and 〈em〉I30〈/em〉 lower than 20 mm and 15 mm/h respectively, and rainfall duration lower than 100 min, interception losses are usually higher than 30%, reaching up to 74%. For the remaining events, interception losses are mostly within the range of 10–20% of rainfall. The data and information on the interception process, presented in this study, helps the comprehension of the overall water balance in dry environments and improve the capacity for parameterization of hydrological models, contributing to a more efficient water and environmental management.〈/p〉 〈/div〉

Description: 〈p〉Publication date: February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of Asian Earth Sciences, Volume 170〈/p〉 〈p〉Author(s): Bülent Oruç, Oya Pamukçu, Tuba Sayın〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the flexural isostatic deformation of the crustal structure and an average effective elastic thickness (EET) of the lithosphere in the central Anatolian plateau has been estimated. We have used the Vening-Meinesz model to calculate the isostatic Moho depths or crustal thicknesses due to topographic loads. The maximum Moho deepening is under the Alpine Orogenic belt throughout the southern part of Anatolian plate, whereas the Moho depths are relatively shallow in the northwestern and central parts of the region. An average EET of central Anatolia’s lithosphere is calculated by multispectral coherence between EGM08 Bouguer anomalies and ETOPO1 topographic data sets. Application of spectral coherence estimation provides an average EET value of 21.3 km and hence points out that the lithosphere is deflected. In addition, density contrasts of the horizontally and vertically extended in the uppermost crust were estimated using compact gravity inversion. We interpret the uppermost crustal blocks in terms of density contrasts may contribute to the total crustal load in addition to topographic loading.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1367912018304541-ga1.jpg" width="382" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Lithos, Volumes 324–325〈/p〉 〈p〉Author(s): Dominique Tanner, Iain McDonald, R.E. Jock Harmer, Duncan D. Muir, Hannah S.R. Hughes〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Low-gradeplatinum-group element mineralisation in the Volspruit Sulphide Zone is sulphide-poor (〈5 vol. %), distributed over a ~60 m-thick horizon in the lowermost cumulates of the northern limb of the Bushveld Complex. Unlike any other platinum-group element (PGE) deposit of the Bushveld Complex, the Volspruit Sulphide Zone is hosted exclusively within harzburgitic and dunitic cumulates in the Lower Zone of the Rustenburg Layered Suite.〈/p〉 〈p〉Here, we present a petrological investigation on the distribution of PGEs and chalcophile metals in mineralised pyroxenite cumulates from the Volspruit Sulphide Zone, to determine the origin of the PGE mineralisation in ultramafic cumulates and evaluate whether Volspruit-style mineralisation could occur in the stratigraphically lowest, ultramafic portions of other layered intrusions.〈/p〉 〈p〉Electron microscopy of pyroxenite cumulates revealed (1) chromite inclusions containing dolomite, albite, monazite, Pb-chlorides, base metal sulphides and Pt-As minerals, (2) the presence of exotic microxenocrysts (〈300 μm diameter) in the pyroxenite matrix such as grains of CaCO〈sub〉3〈/sub〉, U-Th-oxide and Mn-ilmenite, and (3) base metal sulphide assemblages enclosing grains of primary galena, sphalerite and Pb-chlorides.〈/p〉 〈p〉Systematic mapping of high-density mineral assemblages in pyroxenite cumulates across the Volspruit Sulphide Zone identified 196 precious metal mineral grains (Pt-, Pd-, Rh-, Au- or Ag-minerals), 98 Pb-sulphide grains (± Se, Cl), 27 Pb-chloride grains (± K, Se, Te, S), as well as 1 grain of Pb-telluride, 1 monazite grain and 1 grain of U–Pb-Th oxide. Trace element analyses of base metal sulphides reveal the highest S/Se values in pyrrhotite and chalcopyrite yet recorded in the Bushveld Complex. While some base metal sulphides are enriched in PGEs, the overall low-grade of the deposit and inferred fertile ultramafic magma(s) require relatively low R-factors (mass of silicate to sulphide melt) compared to other sulphide-poor PGE deposits, with a calculated R factor of ~500–3000.〈/p〉 〈p〉We consider that the presence of exotic inclusions in chromite, exotic microxenocrysts, and Pb/Zn/Cl grains enclosed within primary base metal sulphide assemblages provide strong evidence for crustal contamination in the Volspruit Sulphide Zone. The Malmani dolomite and the Black Reef quartzite within the lower Chuniespoort Group (2.2–2.4 Ga) are the most likely source of xenocrysts, assimilated in a staging chamber beneath the main Grasvally chamber, in which the Volspruit Sulphide Zone developed. It is possible that the Malmani dolomite contained an enrichment of Pb, Zn, Cl, and S minerals prior to assimilation. The assimilation of dolomite and limestone would locally increase the fO〈sub〉2〈/sub〉 of the magma, triggering chromite crystallisation. The sudden removal of Fe from the melt, coupled with the addition of external sulfur triggered saturation of an immiscible sulphide melt in the ultramafic Volspruit magma. Chromite and base metal sulphides were subsequently emplaced into the main Grasvally magma chamber as a crystal-bearing slurry. Therefore, we consider it is possible for PGE mineralisation to occur in the ultramafic portion of any layered intrusion intruding in the vicinity of carbonate units. Even if this style of mineralisation in the lowermost portions of layered intrusions is sub-economic, it may reduce the grade or opportunity for PGE mineralisation higher up in the local magmatic stratigraphy, or in later magma emplacement events sourced from the same reservoir.〈/p〉 〈p〉The technique of specifically searching for microxenocrysts could be applied beyond layered intrusion research, to identify the range of crustal contaminants in other magmatic systems where macro-scale xenoliths are neither sampled nor preserved.〈/p〉 〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0024493718303979-ga1.jpg" width="500" alt="Unlabelled Image" title="Unlabelled Image"〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 20 December 2018〈/p〉 〈p〉〈b〉Source:〈/b〉 Engineering Geology, Volume 247〈/p〉 〈p〉Author(s): Surya S.C. Congress, Anand J. Puppala, Cody L. Lundberg〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Infrastructure forms the backbone of a nation's economy, and there is a growing demand for a technology that offers quick, safe, and reliable infrastructure performance monitoring data, which would lead to proactive maintenance or repairs of the infrastructure to ensure its quality performance as per the original design. The increase in the applications of unmanned aerial vehicles (UAVs) or drones for such monitoring purposes have been propelled by advancements in aerial vehicle platforms and image-analyses software. Evaluating UAVs for high-quality infrastructure-distress data monitoring has been a major focus for this research. Photogrammetry is the science of measuring distances from two or multiple images of an object and close range photogrammetry (CRP) can be accomplished by using an optical camera mounted on a UAV platform and taking the images of the infrastructure object. This technology, hereafter termed as UAV-CRP technology, utilizes UAVs coupled with high quality camera lens and a global navigation satellite system (GNSS) device to collect high quality data with fewer ground control points (GCPs). The various pieces of equipment need to have their aerial technology compatibility tested in different environmental conditions and evaluate the imagery that is used for image analyses and interpretations. A comprehensive set of calibration checks were executed using the total system comprising of UAV and accessories to evaluate the imagery quality level of transportation and geotechnical infrastructure data. All the checks performed ensured that the data obtained from the UAV-CRP technology meets the quality requirements for infrastructure data. A case study of pavement infrastructure data was provided to validate the high accuracy UAV-CRP data obtained following the guidelines developed in this paper.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Journal of South American Earth Sciences, Volume 89〈/p〉 〈p〉Author(s): Edwin-Alberto Cadena, Ismael Casado-Ferrer〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Prior to the development of the modern Amazonian drainage network during the Late Miocene-Early Pliocene, large areas of western Amazonia may have been occupied by an extensive lacustrine and wetland environment known as the Pebas and Acre systems. These depositional systems are thought to have formed in response to foreland subsidence east of the uplifting Andes. Based on the occurrence at a present-day elevation of 1600 m of fossil pearly freshwater mussels of the genus 〈em〉Anodontites〈/em〉 (indet. species) in intermontane Chota Basin of northern Ecuador (the westernmost South American fossil record for this genus), we discuss their potential implications for understanding of westernmost limit of the Miocene wetland ecosystem and consequently a later timing for the regional uplift of the Eastern Cordillera.〈/p〉〈/div〉 〈/div〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S0895981118302906-fx1.jpg" width="500" alt="Image 1" title="Image 1"〉〈/figure〉〈/p〉〈/div〉