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

Abstract 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 spatio-temporal seawater chemical architecture during time E-C interval. This study presents two Re-Os isochron ages 520.2 ± 6.1 561.7 8.5 Ma for barite-rich black shales from top Liuchapo Doushantuo formations respectively Tianzhu County, Guizhou Province. In combination with existing age data, new suggest that Formation deposited between 550 520 Ma. Moreover, like polymetallic Ni-Mo-PGE layers shelf margin (or platform) facies V-rich horizons transitional slope) to deep-water facies, barite deposits were likely formed due differential mineralization. timing offset resulted elemental concentration related certain local factors (i.e., hydrothermal fluids, redox activity). isochron-derived initial 187 Os /188 ratios (0.902 0.048) (0.740 0.042) fall within range continental weathering flux (1.54) oceanic crust (0.126), implying involvement marine fluids. their difference may reflect variations intensity uplift magnitude.