The study of the Lower Permian rocks from Pingdingshan

Guishan in Chaoxian of the north Anhui Province within the Lower Yangze area shows that siliceous rocks associated with carbonate rocks in Qixia stage were formed by the precipition

replacement and filling of SiO

2

from both deposition and formation water during the diagenetic evolution of carbonate rocks.The occurrence and fabric characteristics of siliceous rocks formed in different peroid are various.Siliceous rocks associated with mudstones and shales in the Cufeng Formation were originated from organisms

directly forming by the accumulation of the remains of siliceous organisms

radiolarians and siliceous sponges in sea water.The contents of siliceous organisms in sea water and the properties of sea water were decisive factors for the formation of these siliceous rocks.