Abstract：Bioclastic limestones in Taiyuan formation of North China plate contains a large number of layered, lay-like, banded and clumped black siliceous rocks. Currently, there have great controversies on the genesis of them. In this paper, the siliceous rocks in Taiyuan formation in Jiaozuo area were selected as samples. By macroscopic observation and collecting siliceous rocks samples of different layers and forms, the mineral components in the siliceous rocks in the Taiyuan formation were analyzed. Thin rock sections, scanning electron microscopy, energy spectrum analysis, X diffraction analysis and differential thermal analysis were used for data analysis. The result showed that main minerals of the siliceous rocks of Taiyuan formation were opal with chalcedony, microcrystalline quartz and calcite. Meanwhile, a large number of pyrophyllite was found in the bottom layered siliceous rocks. Siliceous minerals in siliceous rocks were formed by the replacement of SiO2 to the calcite. The calcite was the remaining mineral of incompletely replacement of siliceous minerals. The pyrophillite was formed in the microfractures by the synthesis of active Si provided outside the system and active Al provided by hydrolysis of the magmatic rock fragments.

Keyword：siliceous rocks;mineralogical characteristics;genesis;Taiyuan formation;Jiaozuo area;