贵州晚二叠世硅质岩类型及其沉积地球化学环境

Types of Siliceous Rocks and Their Sedimentary Geochemical Environment of Late Permian in Guizhou

本文根据岩性岩相、生物组合以及地球化学等特征,将贵州晚二叠世硅质岩划分为四种类型:灰岩中的结核状、条带状硅质岩;台盆或广海沉积的层状含放射虫、硅质海绵骨针硅质岩;局限潮下带中的层状海绵骨针硅质岩;台沟内的厚层状硅质岩。利用微量元素、总稀土和氧同位素等推算出灰岩中结核状、条带状硅质岩是后生交代形成;而台盆、广海沉积和局限潮下带的层状硅质岩是同生或准同生期形成;台沟中厚层状硅质岩则是热液成岩硅质岩。

Guizhou Late Permian siliceous rocks can be divided into four types according to lithologic and lithofacies features, biologic assemblages and geochemical characters. The four types are nodular or stripped siliceous rocks in limestone, layered siliceous rocks hearing radiolarian and siliceous sponge spurs in platform basins or deep basins, layered sponge spur siliceous rocks in restricted subtidal facies zones and thick layered siliceous rocks in platform ditches. Using trace element, 2REE and oxygen isotopic composition, the writers calculate that the nodular or stripped siliceous rocks in limestone were formed by rock-forming replacement in diagensis phase, the layered siliceous rocks in platform basins or deep basins and restricted subtidal facies zones were the product formed in sedimentary phase or sub-synsedimentary phase, but the thick layered siliceous rocks in platform ditches might be the product due to hydrothermal processes.