Geochemical and Hf–Nd isotope data of Nanhua rift sedimentary and volcaniclastic rocks indicate a Neoproterozoic continental flood basalt provenance

Abstract

Geochemical and Hf–Nd isotope studies of Neoproterozoic sedimentary and volcaniclastic rocks in the Nanhua Rift Basin, South China, demonstrate that their source provenances contained large proportions of mafic rocks and various amounts of granites. A significant proportion of the studied Neoproterozoic rift sedimentary and volcaniclastic rocks have initial εNd(t) values higher than those of Neoproterozoic granites, but fall within the range of ca. 825–750Ma basaltic rocks. Their initial εNd(t) values correlate with ratios of La/Sc, La/Cr, La/V, La/Co and La/Ni. The Nd isotope and trace element data, in combination with existing in-situ U–Pb and hafnium–oxygen isotope data from the detrital zircon grains indicate a dominant ca. 825–800Ma mafic provenance. Furthermore, the studied samples formed a linear array and plot within the field defined by the remanent of ca. 825–810Ma continental flood basalts in the Hf–Nd isotopic space. Thus, the inferred large proportions of mafic rocks in the source provenance of the Neoproterozoic rift sedimentary and volcaniclastic rocks likely signify an eroded continental flood basalt province, similar to that reported for the Neoproterozoic sedimentary rocks in Australia. This work thus provides further evidence for the possible once existence of a common large igneous province between South China and eastern Australia as adjacent parts of the supercontinent Rodinia.