关键词: 冲击变质, 冲击变质效应, 冲击变质阶段, 岫岩陨石坑, 微生物硝化作用, 氨氧化古菌, 化能自养固碳, 深海生态系统

Abstract:  Recently, a scientific drilling of 307 meters deep was penetrated through the previously suspected impact crater located near Luoquanli village of Xiuyan county in Liaoning province. A series of impact metamorphic effects caused by shock wave were found, namely, the meltbearing polymictic breccia, the planar deformation features(PDFs) in quartz grains and impact glasses. From these evidences the Xiuyan impact crater was confirmed. This is a great advance in the study of impact metamorphism in China.
　For the identification of an impact crater besides the crater like topography and geomorphology, the discovery of impact metamorphic effects is more authoritative, i.e., shatter cones, high pressure polymorphs of minerals, the planar deformation features in quartz, feldspar and other minerals, the shockcaused isotropization and the forming of diaplectic glass.
　The transient high pressure caused by the shockwave is significantly different from those happened in normal geological processes. It is characterized by extremely high strain rate, rapid and high temperature quenching and 　high pressure postshock temperature  which caused various impact metamorphic effects defining different stages of shock metamorphism. These stages are approximate geobarometers and can be used to estimate the intensity of impact metamorphism.

Key words: impact metamorphism, impact metamorphic effect, stages of shock metamorphism, Xiuyan impact crater