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The Zn isotope composition of sedimentary archives reveals key biosphere-lithosphere interactions throughout geologic history. A recent Zn isotope study of Ediacaran cap carbonates from South Australia revealed that the local isotopic profile reflects global changes in oceanic chemistry. To examine this critical assumption, this study investigates a high-resolution zinc isotope profile of Marinoan post-glacial cap carbonates from the Yangtze Platform, South China. Stratigraphic variations in Zn isotope data from this study are similar to previously reported sections in South Australia and South China. The remarkable isotopic similarity between the two sections that were deposited on distant, geographically separated continental blocks demonstrates that the Zn isotopic variations reflect changing global signatures of the early Ediacaran ocean. This study highlights the value of Zn isotopes in sediments as a global proxy for paleoceanographic studies.

We interpret the systematic stratigraphic changes in the Zn isotope composition of the studied post-glacial Marinoan carbonates as a global oceanic trend controlled mainly by varying inputs and outputs of Zn to the ocean. Decreasing delta Zn-66 values in the lowermost part of the section are attributed to the global precipitation of carbonate enriched in the heavier Zn isotope. A positive shift in the middle part of the section is explained by the non-quantitative removal of isotopically lighter Zn by sulfide minerals. Lower delta Zn-66 values in the uppermost part likely reflect the changing contributions of continental weathering and sulfide precipitation. Our data suggest that non-quantitative removal of Zn by sulfides is a previously unrecognized sink for zinc in the oceans.