ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Articles  (5)
  • Maps
  • 2020-2024  (5)
  • 2015-2019
  • 1945-1949
  • 2024  (5)
Collection
Source
Keywords
Publisher
Language
Years
  • 2020-2024  (5)
  • 2015-2019
  • 1945-1949
Year
  • 1
    facet.materialart.
    Unknown
    Potassium isotopes as a tracer of hydrothermal alteration in ore systems (2024)
    In:  Geochimica et Cosmochimica Acta
    Details
    Publication Date: 2024-04-22
    Description: Hydrothermal alteration is crucial in the formation of many ore deposits, with potassium (K) mobilization and cycling being prevalent. Potassic metasomatism of wall rocks generally forms K-bearing minerals, such as hydrothermal feldspar and mica. However, determining the source and redistribution of K (and other elements transported by the same fluid) in hydrothermal systems is challenging. K isotopes offer a potential solution to this problem. This study presents new K isotope data from two K-rich alteration assemblages — K-feldspar and sericite-quartz-pyrite — in the Jiaodong gold province of China. The data covers a compositional range from unaltered granites to syn-magmatic potassic alteration (formation of K-feldspar) and post-magmatic syn-mineralization phyllic alteration (formation of sericite). Potassic alteration in granite correlates with significant K addition, whereas phyllic alteration of earlier phases of magmatic and hydrothermal K-feldspar resulted in K loss. K-feldspar altered granites display similar δ41K values (–0.55 to –0.42 ‰ for whole-rocks and –0.56 to –0.48 ‰ for K-feldspar separates) as unaltered granite (–0.52 to –0.47 ‰). The narrow δ41K range suggests that magmatic fluid exsolution and magmatic-hydrothermal alteration have a minor effect on δ41K of the altered rock. Phyllic alteration of K-feldspar altered precursor rock leads to K loss and elevated δ41K values ranging from –0.36 to –0.19 ‰ for whole-rocks and –0.34 to –0.17 ‰ for sericite mineral separates. As sericite preferentially incorporates 41K, sericite will have higher δ41K values than the precursor K-feldspar, whereas the fluids will have lower δ41K values. Our study demonstrates that hydrothermal alteration may affect the K isotope composition of altered rocks in several ways, contingent on the nature of the involved phases, making K isotopes a promising tool for studying hydrothermal alteration and associated mineralization.
    Language: English
    Type: info:eu-repo/semantics/article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 2
    facet.materialart.
    Unknown
    Acoustic Emission Evolution and Hydraulic Fracture Morphology of Changning Shale Stressed to Failure at Different Injection Rates in the Laboratory (2024)
    In:  Rock Mechanics and Rock Engineering
    Details
    Publication Date: 2024-02-26
    Description: Hydraulic fracturing has been widely used to enhance reservoir permeability during the extraction of shale gas. As one of the external input parameters, injection rate has a significant impact on formation breakdown pressure and the complexity of hydraulic fractures. To gain deeper insights into the effect of injection rate on breakdown pressure and fracture morphology, we conducted five hydraulic fracturing experiments on Changning shale in the laboratory. We used five different injection rates between 3 and 30 mL/min to fracture cylindrical core samples with 50 mm in diameter and 100 mm in length. We monitored acoustic emissions and surface displacements during the tests, and analyzed the fracture pattern post mortem by using a fluorescent tracer. We find a semi-logarithmic relationship between the breakdown pressure and the injection rates. Second, we find that it is the injection rate that dictates sample deformation and crack formation during breakdown rather than the fluid volume injected during the whole process. The analysis of amplitudes and frequency of acoustic signals indicates that hydraulic fracturing of Changning shale is overall dominated by tensile fractures (〉 60%). However, at low injection rates, shear events are facilitated before rock breakdown. On the other hand, high injection rates result in reducing fracture tortuosity and surface roughness due to limited fluid infiltration in the relatively short injection window. We close this study with a conceptual model to explain the difference between fluid infiltration (low injection rates) and the loading rate effect (high injection rate) in low-permeability shale rocks. The findings obtained in this study can help to adjust injection rates in the field to economically and safely produce gas from shale.
    Language: English
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 3
    facet.materialart.
    Unknown
    Status and temporal change in the distribution of seagrass beds andcoral reefs in the waters of Phu Quoc islands, Kien Giang province (2024)
    Details
    Publication Date: 2024-02-17
    Description: To assess the status and changes in the distribution of seagrass beds and coral reefs in Phu Quoc from 2005 to 2018, we utilized high-resolution multi-spectrum satellite images, aerial photographs, and Google maps. We collected data from three time periods: 2005 (using ASTER with 15 m resolution), 2010 (using SPOT5 with 10 m resolution), and 2018 (using SENTINEL-2 with 10 m resolution). We also conducted an accuracy assessment of 78 key sites in March-April 2019, representing corals (25 sites), seagrasses (28 sites), rocks (8 sites), and sand (12 sites) through SCUBA diving. The results showed that in 2018, the waters of Phu Quoc contained 513 ha of coral reefs and 10,035 ha of seagrass beds, with 290 ha of coral reefs and 9,185 ha of seagrass beds located within the Phu Quoc marine protected area. While the area of coral reefs remained stable between 2005 and 2018, the seagrass beds experienced a significant decline of 652 ha (6.1%), with most losses occurring at Bai Vong (501 ha; 4.69%), Ong Doi cape - Dam Ngoai island (55 ha; 0.52%), Mot Island and Vinh Dam (42 ha; 0.4% each), and Da Chong cape (12 ha; 0.12%). This decline is largely due to recent infrastructure development for community and tourism purposes, which has caused the degradation of seagrass beds.
    Description: Published
    Description: Refereed
    Keywords: MPA ; Seagrass beds ; Coral reef
    Repository Name: AquaDocs
    Type: Journal Contribution
    Format: 57-71
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 4
    facet.materialart.
    Unknown
    The MOSAiC Distributed Network: Observing the coupled Arctic system with multidisciplinary, coordinated platforms (2024)
    University of California Press
    In:  EPIC3Elem Sci Anth, University of California Press, 12(1), ISSN: 2325-1026
    Details
    Publication Date: 2024-05-13
    Description: 〈jats:p〉Central Arctic properties and processes are important to the regional and global coupled climate system. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) Distributed Network (DN) of autonomous ice-tethered systems aimed to bridge gaps in our understanding of temporal and spatial scales, in particular with respect to the resolution of Earth system models. By characterizing variability around local measurements made at a Central Observatory, the DN covers both the coupled system interactions involving the ocean-ice-atmosphere interfaces as well as three-dimensional processes in the ocean, sea ice, and atmosphere. The more than 200 autonomous instruments (“buoys”) were of varying complexity and set up at different sites mostly within 50 km of the Central Observatory. During an exemplary midwinter month, the DN observations captured the spatial variability of atmospheric processes on sub-monthly time scales, but less so for monthly means. They show significant variability in snow depth and ice thickness, and provide a temporally and spatially resolved characterization of ice motion and deformation, showing coherency at the DN scale but less at smaller spatial scales. Ocean data show the background gradient across the DN as well as spatially dependent time variability due to local mixed layer sub-mesoscale and mesoscale processes, influenced by a variable ice cover. The second case (May–June 2020) illustrates the utility of the DN during the absence of manually obtained data by providing continuity of physical and biological observations during this key transitional period. We show examples of synergies between the extensive MOSAiC remote sensing observations and numerical modeling, such as estimating the skill of ice drift forecasts and evaluating coupled system modeling. The MOSAiC DN has been proven to enable analysis of local to mesoscale processes in the coupled atmosphere-ice-ocean system and has the potential to improve model parameterizations of important, unresolved processes in the future.〈/jats:p〉
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 5
    facet.materialart.
    Unknown
    Revision of Troporhogas Cameron (Hymenoptera, Braconidae, Rogadinae) with six new species from India and Thailand (2024)
    In:  ZooKeys vol. 1206, pp. 99-136
    Details
    Publication Date: 2024-07-11
    Description: The genus Troporhogas Cameron, 1905 from the Indo-Malayan region is reviewed. Six new species, Troporhogas alboniger Quicke, Loncle & Butcher, sp. nov., T. benjamini Quicke, Loncle & Butcher, sp. nov., T. hugoolseni Quicke, Loncle & Butcher, sp. nov., T. rafaelnadali Quicke, Loncle & Butcher, sp. nov., and T. rogerfedereri Quicke, Loncle & Butcher, sp. nov. from Thailand, and T. anamikae Ranjith, sp. nov. from India are described and illustrated photographically, bringing the total number of species of the genus known from the Indo-Malayan Region to 19. Troporhogas is recorded for the first time from India. A key is included to differentiate Troporhogas species. A four-gene ML tree based on COI, Cytb, 16S and 28S is reconstructed, representing the six new species. Troporhogas contrastus Long, 2014, originally described from Vietnam, is recorded from Thailand for the first time. The holotypes of the type species, Troporhogas tricolor Cameron, 1905 and that of its junior synonym Iporhogas are illustrated, and photographs are presented of all the species known only from China and Sri Lanka. Sexual colour dimorphism of males of several species is described for the first time. Drawings summarising the different patterns of black marks on the metasoma that aid species recognition are presented.
    Keywords: Checklist ; Iporhogas ; ML phylogeny ; new species ; Rogadinae ; Southeast ; Asia ; Troporhogas
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...