ALBERT

Description: In eastern Turkey, the ongoing convergence of the Arabian and African plates with Eurasia has resulted in the westward extrusion of the Anatolian Plate. To better understand the current state and the tectonic history of this region, we image crust and uppermost mantle structure with ambient noise tomography. Our study area extends from longitudes of 32° to 44°E. We use continuous data from two temporary seismic deployments, our 2006–2008 North Anatolian Fault Passive Seismic Experiment and the 1999–2001 Eastern Turkey Seismic Experiment, as well as from additional seismographs in the region. We compute daily cross-correlations of noise records between all station pairs and stack them over the entire time period for which they are available, as well as in seasonal subsets, to obtain interstation empirical Green's functions. After selecting interstation cross-correlations with high signal-to-noise ratios and measuring interstation phase velocities, we compute phase velocity maps at periods ranging from 8 to 40 s. At all periods, the phase velocity maps are similar for winter and summer subsets of the data, indicating that seasonal variations in noise sources do not bias our results. Across the study area, we invert the phase velocity estimates for shear velocity as a function of depth. The shear velocity model, which extends to 50 km depth, highlights tectonic features apparent at the surface: the Eastern Anatolian Plateau is a prominent low-velocity anomaly whereas the Kırşehir Massif has relatively fast velocities. There is a large velocity jump across the Inner Tauride Suture/Central Anataolian Fault Zone throughout the crust whereas the North Anatolian Fault does not have a consistent signature. In addition, in the southeastern part of our study area, we image a high velocity region below 20 km depth which may be the northern tip of the underthrusting Arabian Plate.

Description: Various styles of ore deposits may form from a single magmatic-hydrothermal system. Identification of a possible genetic link between different ore types in a region is not only of critical importance for a better understanding of the magmatic-hydrothermal processes, but can also help in successful mineral exploration. Both iron oxide-apatite (IOA) and iron skarn deposits are closely associated with intrusive rocks of intermediate to felsic in composition, but whether these two ore types can form from the same magmatic intrusion remains poorly understood. In this study, we present a comparative study between a newly identified subsurface IOA ore body located at the apex of a diorite porphyry and the iron skarn ore bodies located immediately above it in the Jinniu volcanic basin of the Daye district, Middle-Lower Yangtze River metallogenetic belt (MLYRMB), eastern China in order to highlight a genetic link between these two styles of mineralization. The IOA ores are dominated by Ti-rich magnetite with variable amounts of fluorapatite, diopside, and actinolite. This mineralogical assemblage is distinctly different from the iron skarn ores, which consist mainly of Ti-depleted magnetite and subordinate pre-ore garnet and diopside, and post-ore quartz, chlorite, calcite, and pyrite. In addition, magnetite from the IOA ores is characterized by well-developed ilmenite lamellae and has high concentrations of Ni, V, Co, and Ga, consistent with high temperature crystallization, whereas magnetite grains from the iron skarn ores usually exhibit oscillatory growth zones and contain much lower Ni, V, Co, and Ga, indicating their formation under relatively low temperatures. Titanite and fluorapatite from the IOA ores have U-Pb ages of 132.5 ± 2.4 Ma to 128.4 ± 3.0 Ma, which match a titanite U-Pb age for the associated iron skarn ores (132.3 ± 2.0 Ma), and are consistent with zircon U-Pb ages for the ore-hosting diorite porphyry (130.4 ± 0.7 Ma to 130.3 ± 0.5 Ma). This age consistency supports a possible genetic link among the diorite porphyry, IOA ores, and iron skarn ores. We propose that the IOA and skarn ores are the products of two consecutive mineralization stages of the same magmatic-hydrothermal system, involving a high-temperature, hypersaline fluid coexisting with the diorite porphyry magma during emplacement and a subsequent low temperature, diluted hydrothermal fluid. Other IOA and iron skarn deposits of similar ages (130 Ma) are found in a series of volcanic basins in the MLYRMB, which forms one of the world’s largest IOA metallogenic belts. The close association of the two ore styles identified at Daye provides a useful exploration guide for IOA and iron skarn deposits both on a local and regional scale.

Description: Ambient noise tomography is applied to the significant data resources now available across Tibet and surrounding regions to produce Rayleigh wave phase speed maps at periods between 6 and 50 s. Data resources include the permanent Federation of Digital Seismographic Networks, five temporary U.S. Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL) experiments in and around Tibet, and Chinese provincial networks surrounding Tibet from 2003 to 2009, totaling ∼600 stations and ∼150,000 interstation paths. With such a heterogeneous data set, data quality control is of utmost importance. We apply conservative data quality control criteria to accept between ∼5000 and ∼45,000 measurements as a function of period, which produce a lateral resolution between 100 and 200 km across most of the Tibetan Plateau and adjacent regions to the east. Misfits to the accepted measurements among PASSCAL stations and among Chinese stations are similar, with a standard deviation of ∼1.7 s, which indicates that the final dispersion measurements from Chinese and PASSCAL stations are of similar quality. Phase velocities across the Tibetan Plateau are lower, on average, than those in the surrounding nonbasin regions. Phase velocities in northern Tibet are lower than those in southern Tibet, perhaps implying different spatial and temporal variations in the way the high elevations of the plateau are created and maintained. At short periods (〈20 s), very low phase velocities are imaged in the major basins, including the Tarim, Qaidam, Junggar, and Sichuan basins, and in the Ordos Block. At intermediate and long periods (〉20 s), very high velocities are imaged in the Tarim Basin, the Ordos Block, and the Sichuan Basin. These phase velocity dispersion maps provide information needed to construct a 3-D shear velocity model of the crust across the Tibetan Plateau and surrounding regions.

Description: Providing accurate measurement of the magnetic field intensity and its vector components is one of the primary objectives of the China Seismo‐Electromagnetic Satellite (CSES). The high precision magnetometer (HPM) payload assembled on CSES is designed to achieve this goal. In this study, the data format, naming convention, and content of the CSES HPM Level 2 scientific data products are introduced, as a reference for users who are interested in this data set. In particular, flags for potential magnetic field disturbances from the platform and payloads are discussed. Possible scientific applications are also outlined. A preliminary validation of the data is conducted through comparison with magnetic data from the ESA’s Swarm constellation, and the result demonstrates that the HPM data of CSES are of good quality. Taking the intense geomagnetic storm that occurred on August 25–26, 2018 as an example, the magnetic field variations and the expansion of the field‐aligned currents (FACs) during this storm are discussed. We finally show that the CSES HPM data can be used to derive a satellite‐derived index equivalent to the Dst index, which agrees well to the index during this event. Our analysis thus suggests a high scientific potential of the HPM data.

Description: Cassiterite, the economically most important tin mineral, typically has moderate U and variable common Pb contents, making it amenable for U-Pb dating. Cassiterite has extremely low Th/U ratios (Th/U 〈 0.01) and its 208Pb is dominantly common Pb. This is particularly helpful as there is significant interference of tungsten oxides on 202Hg and 204Pb. The feasibility of the 208Pb correction procedure is discussed in detail. The 208Pb corrected LA-SF-ICP-MS data are in good agreement with intercept ages in the Tera-Wasserburg diagram and 207Pb corrected ages. Twelve cassiterite samples were investigated using the ID-TIMS and LA-SF-ICP-MS methods. The ID-TIMS results of Pit-AB, Rond-A, RG-114, BB#7 and 19GX cassiterite are reported for the first time in this study. RG-114, BB#7 and 19GX cassiterite have very low common Pb contents and are recommended for use as primary reference materials for in situ cassiterite. Pit-AB, Rond-A and Yankee cassiterite contain a small amount of common Pb, produce reliable and consistent ages and are suitable as primary reference materials. The remaining five cassiterite samples (Kard, Zinnwald, Els, XBD-W and Y724) were only investigated using the LA-SF-ICP-MS method and produce ages consistent with published age data from the host rocks associated with the tin deposits and with published U-Pb ages of cassiterite from the same deposits. We present an ID-TIMS Usingle bondPb of 154.3 ± 0.7 Ma for the commonly used cassiterite reference material AY-4. This age differs from previously reported ID-TIMS ages. This age discrepancy is caused by different initial common Pb compositions rather than age heterogeneity.

Description: We present a new procedure for U–Pb dating of vesuvianite using laser ablation sector field inductively coupled plasma mass spectrometry (LA-SF-ICP-MS). Vesuvianite is a common mineral in skarn ore deposits and in metamorphic and metasomatic argillaceous carbonate rocks. The age of vesuvianite growth directly dates the formation of skarn mineralization, possibly also the metamorphism and metasomatism of argillaceous limestones. Vesuvianite U–Pb dating may provide age information for hydrothermal, metamorphic, and metasomatic processes that may be hard to get by zircon U–Pb dating. We analyzed eleven vesuvianite samples. Matrix effects were corrected by using Ti-bearing andradite (schorlomite) of known age as no well-characterized vesuvianite was available as a U–Pb reference material. The robustness of the analytical protocol was assessed by additional U–Pb dating of four vesuvianite samples by ID-TIMS. The U–Pb ages determined by ID-TIMS and LA-SF-ICP-MS agree well within uncertainties. An additional seven vesuvianite samples yielded in situ U–Pb ages that agree with previously published zircon, cassiterite, or wolframite U–Pb ages from the same area. Therefore, U–Pb dating of vesuvianite by LA-SF-ICP-MS represents a fast, relatively low-cost approach with high spatial resolution that may be particularly suited to date skarn mineralization.

Description: Various ESA projects and several proposals to first Swarm DISC Call for Ideas (May 2016) suggested possible evolution for the current Swarm Level 2 FAC products, and the implementation of quality flags for the FAC products. The Field-Aligned Currents—Methodology Inter-Comparison Exercise (FAC-MICE) consisted in comparison of the various methods to determine the FAC from Swarm data, with a test dataset of 28 Swarm auroral crossings delivered to participants last June. Eight groups performed the FAC-MICE analysis. The results of this exercise, discussed in the dedicated ‘Swarm Ionospheric Currents Products workshop’ in ESTEC on September 2017, highlighted the strengths of the various methods/approaches. Following discussion with the participants to this workshop, we are now working to develop an open source platform for user-definable FAC calculation.

Description: We present an analytical protocol for in situ U–Pb isotope dating of wolframite series minerals [(Fe,Mn)WO4], the main ore mineral for tungsten, by LA-SF-ICP-MS. Precision and accuracy of the protocol was intensively assessed using our newly developed well-characterized U–Pb wolframite reference material. The tungsten oxide interference on Hg and Pb was investigated in detail. The matrix effect between ferberite and hübnerite during laser ablation was thoroughly examined for wolframite series minerals with a different Mn/(Mn + Fe) ratio. The closure temperature of wolframite, with respect to the U–Pb system, was evaluated. The application of eleven wolframite samples, with ages from ∼1780 Ma to ∼26 Ma, robustly demonstrated the feasibility of our approach. Most studied wolframite series minerals yielded U–Pb concordant or subconcordant ages. Samples with a relatively high U content and negligible common Pb content typically had a 206Pb/238U age precision of ca. 1%. The new in situ data agree well with published cassiterite or wolframite ages from the same locations. LA-SF-ICP-MS, with the advantages of high sensitivity, rapidity, and relatively low cost, as well as moderate spatial resolution (i.e., 32 or 44 μm) that is sufficiently high to avoid sulfide inclusions, is the method of choice for in situ wolframite U–Pb microanalysis.

Description: During the August 25, 2018 geomagnetic storm, the new borne CSES-01 satellite and the Swarm A satellite detected a really large equatorial plasma bubble (EPB) in the post-midnight sector over western Africa. We investigated the features of this deep ionospheric plasma depletion using data from the Langmuir probes on-board CSES-01 and Swarm A satellites, and data from the high-precision magnetometer and the electric field detector instruments on-board CSES-01. Using also plasma and magnetic field data from THEMIS-E satellite we found that, during the passage of the magnetic cloud that drove the geomagnetic storm, an impulsive variation lasting about ten minutes characterized the solar wind (SW) pressure. The analysis of the delay time, between the occurrence of such impulsive variation and the detection of the plasma bubble, suggests a possible link between the SW pressure impulsive variation as identified by THEMIS-E and the generation of the EPB as detected by CSES-01 and Swarm A. We put forward the hypothesis that the SW pressure impulsive variation might have triggered an eastward prompt penetrating electric field that propagated from high to equatorial latitudes, overlapping in the nightside region to the zonal westward electric field, causing either a reduction or an inversion, at the base of the EPB triggering.

Description: To expand the newly developed ARM glasses as reference materials for in situ microanalysis of isotope ratios and iron oxidation state by a variety of techniques such as SIMS, LA-MC-ICP-MS and EPMA, we report Li-B-Si-O-Mg-Sr-Nd-Hf-Pb isotope data and Fe2+/ΣFe ratios for these glasses. The data were mainly obtained by TIMS, MC-ICP-MS, IR-MS and wet-chemistry colorimetric techniques. The quality of these data was cross-checked by comparing different techniques or by comparing the results from different laboratories using the same technique. All three glasses appear to be homogeneous with respect to the investigated isotope ratios (except for B in ARM-3) and Fe2+/ΣFe ratios at the scale of sampling volume and level of the analytical precision of each technique. The homogeneity of Li-B-O-Nd-Pb isotope ratios at the microscale (30–120 μm) was estimated using LA-MC-ICP-MS and SIMS techniques. We also present new EPMA major element data obtained using three different instruments for the glasses. The determination of reference values for the major elements and their uncertainties at the 95% confidence level closely followed ISO guidelines and the Certification Protocol of the International Association of Geoanalysts. The ARM glasses may be particularly useful as reference materials for in situ isotope ratio analysis.