Earth Science Frontiers ›› 2022, Vol. 29 ›› Issue (1): 160-175.DOI: 10.13745/j.esf.sf.2021.8.13

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Geochemical composition and paleoceanic environment of the Lower Cambrian black shale-hosted Qianjiaping vanadium deposit in the southern Qinling Region

XU Lingang1,2(), FU Xuerui1, YE Huishou3, ZHENG Wei3, CHEN Bo4, FANG Zhenglong4   

  1. 1. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
    2. Key Laboratory for Exploration Theory & Technology of Critical Mineral Resources, Ministry of Natural Resources, Beijing 100083, China
    3. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
    4. Shaanxi Huayuan Mining Co., Ltd., Shangluo 726000, China
  • Received:2021-04-25 Revised:2021-06-22 Online:2022-01-25 Published:2022-02-22

Abstract:

The Qianjiaping vanadium (V) deposit is a typical Lower Cambrian black shale-hosted V deposit in the Southern Qinling Region. Vanadium mineralization in the Qianjiaping deposit mainly occurs in multilayered cherts with carbonaceous shale in the 1st member of the Shuigoukou Formation. To better understand the origin of vanadium and redox environment in Early Cambrian seawater in South Qinling, we report in this study the bulk geochemical compositions of the V-rich carbonaceous shale from the 1st member and the overlying muddy limestone from the 2nd member of the Shuigoukou Formation. The Y/Ho ratio is higher in the multilayered chert-mudstone samples than in the muddy limestone samples, indicating a dominant authigenic origin for V in the 1st member, whereas in the 2nd member V may be mostly derived from detrital components. Discrimination plots, Eu/Eu*-V, Y/P2O5-Zr/Cr and Fe/Ti-Al/(Al+Fe+Mn), suggest V mineralization is mainly by precipitation from ambient seawater, while hydrothermal fluids plays a minor role. All samples showed negative Ce anomaly, ranging from 0.26-0.96. Together considering the comparatively high Mo/Sc, V/Sc, V/Cr and low Th/U ratios in the 1st member, we infer a redox stratified ocean during the early Early Cambrian in the Southern Qinling Region, which became entirely oxygenated during the late Early Cambrian.

Key words: Qianjiaping vanadium deposit, trace element, REE, ore genesis, redox environment, Southern Qinling Region

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