Abstract: Large scale planar geological mapping, profiling survey and microfabric analyses proved that lithophysa structure was developed in rhyolite in Yingcheng coal mine area, Jiutai City. According to the genesis, occurrence,macro shape and microscopical characteristics，lithophysa was divided into three types：the independent lithophysa in bentonite，surface mounted lithophysa on stratiform rhyolite and interior lithophysa in the massive rhyolite．The diameter range of independent lithophysa is from a few centimeters to tens centimeters. Independent lithophysa is grape-like. Independent lithophysa distributed within the bentonite which altered from perlite. The crystallization differentiation of spheres which were formed by magma quenching into water generated the independent lithophysa. The diameter range of surface mounted lithophysa is from a few millimeters to a few centimeters. Surface mounted lithophysa is grape-like too. The surface mounted lithophysa distributed around the outer layer of the independent lithophysa in plane. Genesis mechanism of surface mounted lithophysa is the same as independent lithophysa. The diameter range of interior lithophysa is from a few millimeters to a few centimeters. Multi-rings structure was developed in the interior lithophysa. The mineral crystallization fractionation of gas-enriched magma from surface to inner releasing gas generated the interior lithophysa. These three types of lithophysa distribute in upper subfacies of effusive facies. The forming condition is condensing shrinkage in fixed volume.

Key words: Songliao Basin, Yingcheng Formation, rhyolite, lithophysa