DUCTILE DECOLLEMENT SHEAR ZONE IN XISHAN OF BEIJING
北京西山的深部韧性滑脱剪切带

At the depth of the crust in Xishan, Beijing, exists a comparatively large ductile decollement shear zone extenting from east to west, distributed within the limits of more than 1 km above and below the main boundary plane that is represented by chloritoid-mica phyllites belonging to the Xia-maling Formation of the Sinian. Since in the shear zone are developed "a"-type folds, sheath folds and extensional lineations, indicating shear vector, and minerals here possess strong plastic flow and rotated strain, it is considered to be a planar middle-high pressure dynamic metamorphic belt. Limited strain analyses suggest that this is the result of simple shear mechanism. Recognition of the high strain zone can give some important informationconcerning intrastructure patterns and geodynamics of Xishan in the Sino-Korean Platform.