Geochemistry of sandstones from the Neoproterozoic Shijia Formation, northern Anhui Province, China: Implications for provenance, weathering and tectonic setting

Abstract

The Neoproterozoic Shijia Formation sandstones in northern Anhui Province, China were analyzed for major oxides and trace elements to infer their provenance, intensity of paleo-weathering of the source rocks and their depositional tectonic setting. Discrimination diagrams based on geochemistry and some ratios of elements indicate that felsic rocks constitute their source rocks, probably a quartzose recycled orogen provenance. The values of Chemical Index of Alteration (CIA=53) are low, which was considered to be affected by K-metasomatism, whereas the high CIW (82, Chemical Index of Weathering) values indicate moderate to intensive weathering of the source material. Tectonic discrimination method based on geochemical data of sandstones, as well as the low ICV (0.94, Index of Compositional Variation) values reveal that they were deposited in a passive continental margin or intra-plate basin. Research progress (including geochronological and geochemical study, etc.) and the study therein, imply that the tectonic background of the southeast margin of North China Craton (NCC) before and after 0.85Ga were active and passive, respectively.