Nd isotopic variations of Chinese seawater during Neoproterozoic through Cambrian

Samples of sedimentary phosphatic rocks and manganese deposits were collected from the Neoproterozoic Sinian System and the Lower Cambrian Series in the Yangtze region, China. The results from SmNd isotopic determinations show a considerable change in Nd isotopic composition of the Chinese seawater during the Neoproterozoic Period, which was similar to that of the Panthalassa ocean, buth with smaller swing. The εNd(T) values of the Chinese seawater were about −4.5 in the Nantuo ice age (corresponding to the Varanger ice age), falling within the range of the Panthalassa ocean, then gradually decreased and separated from the Panthalassa ocean after the Nantuo ice age, and finally reached the lowest point (about −8.0) at the beginning of the Early Cambrian, obviously distinct from the Panthalassa ocean (−20 to −10). As one might infer, the Chinese seawater was not co-oceanic with the Panthalassa ocean in terms of Keto and Jacobsen (1988) and belonged to another major ocean as a result from reconstruction of the global palaeoceanographic pattern during the Sinian (Vendian) through the Cambrian.