Re-Os Geochronology of the Liuchapo Formation across the Ediacaran-Cambrian Boundary of the Yangtze Block(South China)

作     者：Yong Fu Fuliang Wang Chuan Guo Chao Li Peng Xia Yong Fu;Fuliang Wang;Chuan Guo;Chao Li;Peng Xia

作者机构：College of Resource and Environmental EngineeringGuizhou UniversityGuiyang 550025China Key Laboratory of Karst Georesources and EnvironmentMinistry of EducationGuizhou UniversityGuiyang 550025China Guizhou Geological Environment Monitoring InstituteGuizhou 550081China National Research Center for GeoanalysisChinese Academy of Geological SciencesBeijing 100037China 

出 版 物：《Journal of Earth Science》 (地球科学学刊（英文版）)

年 卷 期：2022年第33卷第1期

页      面：25-35页

核心收录：

学科分类：070902[理学-地球化学] 0709[理学-地质学] 07[理学] 0708[理学-地球物理学] 

基　　金：jointly supported by the National Natural Science Foundation of China(Nos.41763006,42063009,U1812402) the Talent Base Project of Guizhou Province(No.RCJD2018-21)。 

主　　题：geochemistry Ediacaran-Cambrian initial^(187)Os/^(188)Os Liuchapo Formation Re-Os isotope Yangtze Block 

摘      要：The Ediacaran-Cambrian(E-C) succession in South China records remarkable oceanic,biological and geochemical variations,but it was not well defined geochronologically,which hinders the interpretation of the spatio-temporal seawater chemical architecture during the time E-C interval.This study presents two Re-Os isochron ages of 520.2±6.1 and 561.7±8.5 Ma for the barite-rich black shales from the top Liuchapo and Doushantuo formations respectively in Tianzhu County,Guizhou Province.In combination with existing age data,the two new Re-Os isochron ages suggest that the Liuchapo Formation was deposited between 550 and 520 Ma.Moreover,like the polymetallic Ni-MoPGE layers of shelf margin(or platform) facies and V-rich horizons of transitional(or shelf slope) to deep-water facies,the barite deposits were likely formed due to differential mineralization.The timing offset likely resulted from differential elemental concentration related to certain local factors(i.e.,hydrothermal fluids,seawater redox and biological activity).The isochron-derived initial ^(187)Os/^(188)Os ratios of the top Liuchapo Formation(0.902 ± 0.048) and the Doushantuo Formation(0.740 ± 0.042) fall within the range of continental weathering flux(1.54) and oceanic crust(0.126),implying the involvement of marine hydrothermal fluids.Moreover,their difference of initial ^(187)Os/^(188)Os ratios may reflect variations of continental weathering intensity and uplift magnitude.