库鲁克塔格早寒武世泥质岩的地球化学特征及其地质意义

Geochemical characteristics and geological significance of Early Cambrian argillaceous rocks in Kuruk Tag, Xinjiang

通过对且干布拉克地区西山布拉克组泥质岩岩石学、地球化学特征的研究,探讨其物源特征、风化作用以及沉积盆地的构造环境。且干布拉克大坂剖面泥质岩Al_2O_3/TiO_2、Th/Sc、(Gd/Yb)_N、(Eu/Eu*)_N、ICV、CIA均值分别为24、0.9、1.1、0.6、1.2、70,莫合尔山剖面泥质岩Al_2O_3/TiO_2、Th/Sc、(Gd/Yb)_N、(Eu/Eu*)_N、ICV、CIA均值分别为10.5、0.2、3.5、1.01、2.8、75。这些特征表明,研究区泥质岩为第一次沉积的沉积物,源区母岩主要以岩浆岩为主。且干布拉克大坂剖面泥质岩的源区母岩主要以南部的花岗岩等长英质岩浆岩为主,沉积于陆内较稳定的构造环境;莫合尔山剖面泥质岩的源区母岩主要以北部玄武岩等中基性岩浆岩为主,沉积于陆内火山岩隆起的构造环境。在诺丁尼亚超大陆裂解的大构造背景下,早寒武世早期莫合尔山的裂解作用比且干布拉克大坂更为强烈。CIA值表明且干布拉克地区泥质岩物源区母岩经历了中等程度的化学风化作用,沉积物沉积时气候较温暖、湿润,早寒武世早期位于30°S左右的低纬度地区。且干布拉克大坂剖面的含钒炭质硅质页岩、莫合尔山剖面的铁质磷质岩的元素地球化学特征暗示了磷、钒等成矿元素与可能来自于震旦纪和寒武纪的中基性火山岩。

Systematic analysis of petrology and geochemistry of Xishanbulake Formation argillaceous rocks in Tseganbrark wasmade in this study. The purpose of this paper is to discuss sediment provenance, weathering and tectonic setting of sedimentationbasin. The ratios of Al2O3/TiO2, Th/Sc, (Gd/Yb)N,(Eu/Eu*)N, ICV, CIA of argillaceous rocks in Qieganbulakedaban are 24, 0.9, 1.1,0.6, 1.2, 70 respectively, while these ratios in Moheershan are 10.5, 0.2, 3.5, 1.01, 2.8, 75 respectively. These characteristics indicatethat all of argillaceous rocks tended to occur in first- cycle deposit. The source rock of argillaceous rocks in Qieganbulakedabanwere granitoids formed in a stable intracontinental environment, whereas the source rock of them in Moheershan were basicintermediatemagmatic rocks formed in a volcanic uplift environment. Under the tectonic setting of Rodinia Supercontinentcracking, the cracking of Moheershan was stronger than Qieganbulakedaban. The CIA in the study area demonstrates that the sourceregion of argillaceous rocks suffered from medium degree chemical weathering which reflects a warm and moist climate located in30°S. The CIA characteristics of vanadium-bearing carbonaceous shales and phosphorite suggest that the sources of vanadium andphosphorus were connected with basic-intermediate magmatism in Sinian and Cambrian.