中二叠统热水沉积新证据——以皖南“嵇亭岭砾岩”为例

通过对安徽泾县-宣州地区中二叠统"嵇亭岭砾岩"中硅质岩、含角砾硅质岩和硅质角砾岩的岩石学和沉积地球化学分析，认为"嵇亭岭砾岩"为非构造成因异常沉积岩；相当于栖霞组本部灰岩段中上部-顶部灰岩段，时代为中二叠世祥播阶；为热水沉积硅质岩，距离热液通道的远近决定了其产出形态，距离越近，角砾越发育；中二叠世深部岩浆房上涌造成强烈的拉张断陷，形成了穹状隆起和一系列地堑与地垒构造，存在部分上涌的岩浆沿着地堑与地垒的断裂上涌，漫溢至海底乃至地表，上涌的岩浆与海水混合，使海水中硅质含量大幅度升高，发生一系列与热液相关的硅化作用和碳酸盐中硅的置换作用。

New Evidence of Middle Permian Hydrothermal Cherts Deposition: A case study of Jitingling Breccia,south Anhui province

According to analysis, the petrological and lithogeochemical characteristics of siliceous, brecciated siliceous, and siliceous breccia from the Jitingling breccia in the middle Permian strata of the Jingxian-Xuanzhou area, Anhui Province indicate that the "Jitingling breccia" is mostly nontectonic in origin. It is equivalent to middle-upper and top parts of the Qixia limestones formation, whose age is Xiangbo Stage, Middle Permian. The Breccia contains hydrothermal sedimentation cherts, and the output shape is determined by the distance from the fluid conduit, i.e., the shorter distance determines the breccia development. Influenced by the strong extension tectonics in the Middle Permian, a deep magma chamber was upwelling and formed a quaquaversal structure rise and a series of grabens and horst structures. The upwelling magma is widely distributed; part of the magma upwelled along the faults in the graben and horst, overflowed to the bottom of the sea, even reaching the surface. When the upwelling magma mixed with seawater, the siliceous content in the seawater increased drastically, leading to the occurrence of a series of hydrothermal-related silicidation and substitution of silicon in carbonate.