Element Geochemistry of sandstones in the Silurian of central Tarim basin and the significance in provenance discrimination
塔中地区志留系砂岩元素地球化学特征与物源判别意义

The geochemistry and provenance characteristics of sandstones in the Silurian of central Tarim basin have been studied by analyzing the selected major element and trace element compositions.Petrographic results suggests that the tectonic setting is active continental margin and passive continental margin,the provenance is recycling orogenic belt mainly.The sandstones mainly consist of quartz,K-feldspar,plagioclase,illite and chlorite etc.The chemical index of weathering(CIW)and the chemical index of alteration (CIA)parameters of the sandstones suggest the weathering of the clastic constituents is intense in the area.The intensity of weathering:Yimugantawu Formation>Tataertage Formation>Kepingtage Formation.The index of compositional variability(ICV) suggests some sandstones contain first cycle material.The A-CN-K diagram indicates that a high average plagioclase to K-feldspar ratio in the provenance,range from granodiorite to granite,the clastic constituents of sandstones underwent K-metasomatisim during weathering processes,illite replaced feldspar and thus perhaps the original kaolinite in the feldspar.The trace element and ratios,for example(La/Yb)_N,(La/Lu)_N et al.,suggest a mix of a granodiorite granite source for the sandstones in this area.