Permian system in Tazhong area may be divided into three lithology groups: lower clastic group, volcanics group and upper clastic group based on the data of core, drilling, logging and so on.

A set of intermediate basic volcanics, pyroclastic rock and top part of clastic rock is found in north of Balikun coal mine.

Volcanics mainly growth gas pocket, primary rift and secondary rift, The secondary porosity of clastic rocks is much more developed.