贵州遵义沙坝沟地区茅口组硅质岩-粘土岩沉积建造成因研究

Study on the Genesis of Sedimentary Formation of Silicalite-Claystone of Maokou Group in the Shabagou Area of Zunyi,Guizhou Province

贵州遵义地区中二叠统茅口组中上部发育特殊的硅质岩-粘土岩沉积建造,其对区域沉积作用、构造及古地理演化具有重要的指示意义。本文以遵义沙坝沟地区中二叠统茅口组中上部沉积建造为研究对象,通过野外剖面观察、岩石学、矿物学及地球化学手段分析硅质岩、粘土岩的物源及成因。硅质岩-粘土岩沉积建造见厚层-块状构造、角砾状构造、条带状构造及气孔状构造。结合微量元素及稀土元素特征,认为该硅质岩-粘土岩沉积建造形成于大陆边缘的氧化环境中,硅质岩具有典型的热水沉积成因,粘土岩为热水物质与陆源物质混合成因,与中二叠世茅口中晚期地幔柱活动具有显著的成因联系。

A special sedimentary formation of silicalite-claystone occurs in the middle-upper part of the Maokou group of the Middle Permian in Zunyi county,Guizhou has important indicative significance for regional sedimentation,tectonics and paleogeographic evolution.This paper studies the sedimentary formation of the middle-upper part of the Maokou group in the Middle Permian in Shabagou area,Zunyi county.The material source and genesis of silicalite and claystone are analyzed by field profile observation,and petrology and mineralogy and geochemical means.The silicalite-claystone sedimentary formation is characterized by thick layer-block,brecciated,banded or vesicular structures.Combined with the characteristics of the trace elements and rare earth elements,it is believed that the silicalite-claystone sedimentary formation is formed in an oxidation environment on the continental margin.The silicalites are typical of genesis of hydrothermal sediment,and the claystones are a mixture of hydrothermal components and terrigenous components,which is significantly related to the mantle plume activity in the mid-late Maokou period of the Middle Permian.