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400 results on '"Zong, Keqing"'

101. Tanz zircon megacrysts: a new zircon reference material for the microbeam determination of U–Pb ages and Zr–O isotopes

Author

Hu, Zhaochu, primary, Li, Xian-Hua, additional, Luo, Tao, additional, Zhang, Wen, additional, Crowley, James, additional, Li, Qiuli, additional, Ling, Xiaoxiao, additional, Yang, Chuan, additional, Li, Yang, additional, Feng, Lanping, additional, Xia, Xiaoping, additional, Zhang, Shao-Bing, additional, Wang, Zaicong, additional, Guo, Jinliang, additional, Xu, Lei, additional, Lin, Jie, additional, Liu, Xiaoming, additional, Bao, Zhian, additional, Liu, Yongsheng, additional, Zong, Keqing, additional, Chen, Wei, additional, and Hu, Shenghong, additional

Published
2021
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118. High-precision Determination of Gold Mass Fractions in Geological Reference Materials by Internal Standardisation

Author

Cheng, Huai, Wang, Zaicong, Chen, Kang, Zong, Keqing, Zou, Zongqi, He, Tao, Hu, Zhaochu, Fischer-Goedde, Mario, Liu, Yanhong, Cheng, Huai, Wang, Zaicong, Chen, Kang, Zong, Keqing, Zou, Zongqi, He, Tao, Hu, Zhaochu, Fischer-Goedde, Mario, and Liu, Yanhong

Abstract

Determination of gold abundances in natural rock is critical for applications, but very challenging. Here, we report a method for determining gold with a very low mass fraction (> 0.01 ng g(-1)) in rocks. The method involves Carius tube digestion with reverse aqua regia, chromatographic separation to remove most of the sample matrix and measurement by high-sensitivity ICP-MS. The mono-isotopic element gold was quantified by external calibration using an internal standardisation of gold to platinum that was precisely determined by isotope dilution. The method is robust and the obtained results are indistinguishable (< 5-10%, 2s) from those independently obtained by a standard addition technique on the same solution. The results from reference materials TDB-1 and GPt-2 are consistent with the certified values and those determined by HF-aqua regia digestion, confirming the validity of the method. TDB-1 (n = 20), GPt-2 (n = 6), BHVO-2 (n = 9) and other mafic RMs are homogenous for gold (10-20%, 2s) at the 2 g test portion level; however, sample heterogeneity affects some RMs. Gold and platinum-group elements also display different extents of sample heterogeneity for different RMs. Given the homogeneity observed for TDB-1, GPt-2 and BHOV-2, they are recommended as well-suited RMs for inter-laboratory comparison studies of gold.

Published
2019

119. Remnants of middle Triassic oceanic lithosphere in the western Indus–Tsangpo suture zone, southwestern Tibet.

Author

Liu, Qiang, Liu, Feng, Li, Hualiang, and Zong, Keqing

Subjects
LITHOSPHERE, RARE earth metals, GONDWANA (Continent), MID-ocean ridges
Abstract

Discontinuous ophiolites within the Indus–Tsangpo suture zone (ITSZ) in southern Tibet represent remnants of Neo‐Tethyan oceanic lithosphere, which are considered to have formed during the late Jurassic to early Cretaceous. We report field observations, petrological and geochronological data for some mafic intrusions in a tectonic mélange in the southern ophiolitic belt of the western ITSZ. Zircon from a gabbro yields an age of 243 ± 1 Ma with εHf(t) values of +7.9 to +13.2. Rare earth element (REE) pattern of this rock resembles that of normal mid‐ocean ridge basalt. We suggest that such gabbro and surrounding mafic–ultramafic rocks represent the remnants of middle Triassic oceanic lithosphere in the ITSZ. Our findings indicate that the Neo‐Tethys Ocean between India and the Lhasa terrane existed from at least the middle Triassic, contrasting with the commonly held view that the Neo‐Tethys Ocean opened along the northern edge of Gondwana during the late Triassic–early Jurassic. [ABSTRACT FROM AUTHOR]

Published
2021
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137. Accurate determination of sulfur isotopes (δ33S and δ34S) in sulfides and elemental sulfur by femtosecond laser ablation MC-ICP-MS with non-matrix matched calibration.

Author

Fu, Jiali, Hu, Zhaochu, Li, Jianwei, Yang, Lu, Zhang, Wen, Liu, Yongsheng, Li, Qiuli, Zong, Keqing, and Hu, Shenghong

Subjects
FEMTOSECOND lasers, SULFUR isotopes, DOSE fractionation, EXCIMER lasers, PYRITES, SINGLE crystals
Abstract

The isotopic composition of sulfur is a vital tracer used in the Earth and planetary sciences. In this study, the laser- and ICP-induced isotopic fractionation in S-rich minerals (sulfides and elemental S) with different matrices was investigated by using 257 nm femtosecond (fs) and 193 nm ArF excimer nanosecond (ns) laser ablation systems coupled to a Neptune Plus MC-ICP-MS. Compared to ns-LA-MC-ICP-MS, higher sensitivity (1.4–2.4 times) under similar instrumental conditions and better precision (∼1.6-fold) under the same signal intensity condition were achieved by fs-LA-MC-ICP-MS. In addition, a fs-laser provides less fluence and matrix dependent S isotopic fractionation, and more stable transient isotopic ratios compared to a ns-laser. Better results acquired by fs-LA-MC-ICP-MS were attributed to the smaller size of particles and less thermal effect produced by using the fs-laser, which were evidenced by the morphologies of the ablation craters and ejected aerosol particles of P-S-1 (the pressed powder pellet of IAEA-S-1) and PPP-1 (a pyrite single crystal from the Sukhoi Log deposit). The ICP-induced isotopic fractionation (matrix effect) was still found in fs-LA-MC-ICP-MS under the maximum sensitivity conditions. However, a significant reduction of the matrix effect was obtained under robust plasma conditions at a lower makeup gas flow rate (0.52–0.54 l min−1) relative to the maximum sensitivity condition (0.6 l min−1) for S isotope analysis. This could be ascribed to the particles that not only pass into the higher temperature ICP for a longer residence time at a lower makeup gas flow rate that resulted in more efficient vaporization of the particles, but also experience a more robust plasma induced by adding 4–6 ml min−1 N2 into the plasma. Furthermore, under the robust conditions, the results of six reference materials with different matrices obtained by fs-LA-MC-ICP-MS with non-matrix matched calibration with a spot size of 20–44 μm showed excellent agreement with the reference values (the accuracy of 0.01–0.15‰ for δ34S and 0.11–0.45‰ for δ33S and the precision of 0.16–0.40‰ (2 s) for δ34S and 0.35–0.78‰ (2 s) for δ33S) and the mass-dependent fractionation line, validating the applicability of the proposed approach for providing high-quality in situ isotope data (δ33S and δ34S) of sulfides and elemental sulfur at high spatial resolution using non-matrix matched analysis. [ABSTRACT FROM AUTHOR]

Published
2017
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145. Plate Tectonics: The Stabilizer of Earth's Habitability.

Author

Wang, Zhensheng, Zhang, Junfeng, Zong, Keqing, Kusky, Timothy M., and Wang, Yanxin

Subjects
*PLATE tectonics, *EARTH (Planet), *LONG-Term Evolution (Telecommunications), *REYNOLDS number, *RECYCLING & the environment
Abstract

Earth is the only planet known to be habitable, and is also unique with its liquid water, and the operation of plate tectonics. The geological record shows that the habitability of our planet can rapidly recover from major disasters or catastrophes, even those that cause mass extinctions. We suggest that plate tectonics, which acts as a link between the shallow and deep, is pivotal for the formation, evolution, and long-term stability of the hydrosphere, atmosphere, lithosphere, and thus life. Plate tectonics links the surface environment with the deep interior of high viscosity, low Reynolds number, low entropy, and low chaos, able to produce a strong healing effect to neutralize catastrophic events. It can transfer the bio-essential elements from the deep interior to the near-surface environment and can recycle toxic elements to the deep. This unique planetary energy and material transfer process of Earth is a continuous, slow-release, and bidirectional cycle, where a change in the surface is slowly buffered by a reaction from the deep, shaping a long-term and stable habitable environment. Therefore, it is considered that plate tectonics is the basic condition for the long-term stable evolution of the Earth's biosphere and the stabilizer of the Earth's habitability. [ABSTRACT FROM AUTHOR]

Published
2023
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150. Improved Inter-calibration of Faraday Cup and Ion Counting for In Situ Pb Isotope Measurements Using LA-MC-ICP-MS: Application to the Study of the Origin of the Fangshan Pluton, North China.

Author

Zhang, Wen, Hu, Zhaochu, Yang, Lu, Liu, Yongsheng, Zong, Keqing, Xu, Haijin, Chen, Haihong, Gao, Shan, and Xu, Lei

Subjects
CALIBRATION, FARADAY cup, LEAD isotopes, GEOLOGICAL time scales, GEOCHEMICAL cycles
Abstract

Copyright of Geostandards & Geoanalytical Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2015
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