Abstract:

 The geochemical characteristics of clastic sedimentary rocks in sedimentary basin are mainly controlled by the origins of the rocks. In this paper, we report on the whole-rock major and trace element compositions of clastic sedimentary rocks in North Qiangtang Basin. The results show that the index of compositional variability and the chemical index of alteration for different samples are similar, revealing a relatively fresh, weakly matured origin with weak-medium chemical weathering. The rocks are characterized by high SiO₂ contents, and relatively high TFe₂O₃+MgO contents, but K₂O/Na₂O ratios vary largely for different samples. The rocks have the similar trace and REE patterns with the post-Archean Australia shales and upper continental crust, characterized by enrichment in LREE, evident Eu depletions, and weak Ce depletions.Furthermore, the ratios of Th/U, La/Sc, Th/Sc, Ba/Sr of Kanglu Formation and the binary diagrams TiO₂ vs.Ni, La/Th vs.Hf, Co/Th vs.La/Sc and Th/Sc vs.La/Sc denote that the origin of the sediments is characterized by superficial and felsic.The tectonic setting discrimination diagrams, such as of SiO₂ vs.K₂O/Na₂O, La vs.Th, La/Y vs.Sc/Cr and La vs.Th vs.Sc, Th vs.Sc vsZr/10, Th vs.Co vs.Zr/10, and the ratios of Th/U, Rb/Sr suggest that the source material of Kanglu Formation in North Qiangtang mainly belongs to continental arc setting, and partially belongs to passive continental margin and oceanic island arc setting.

Key words: clastic sedimentary rock, North Qiangtang Basin, Kanglu Formation, geochemistry, provenance, tectonic background