鄂西北南化塘地区速冲推覆韧性剪切变形特征及位移量计算

THE CHARACTERISTICS OF THE THRUST NAPPE DUCTILE SHEAR ZONE IN NANHUATANG,NORTHWEST HUBEI

逆冲推覆韧性剪切变形是鄂西北南化塘地区的主期变形．分别由上震旦统碳酸盐岩褶皱层、耀岭河群强变形层及武当山群顶部糜棱岩组成。剪切带面理南倾，推覆方向自南西向北东．其内发育逆冲褶皱、剪切透镜体、Ａ型拉伸线理等宏观构造及σ型、Ｓ－Ｃ、斜长石骨牌式、帘石雪球、压力影等微观构造．耀岭河群顶底层位发育蓝闪片岩，顶部为基性蓝闪片岩，底部为长英质蓝闪片岩，特征矿物是有铝闪石。剪切位移量大于１６．８ｋｍ，压力为５×１０６～３．８×１０６Ｐａ．逆冲推覆韧性剪切变形同华北古板块与扬子古板块相互碰撞密切相关．

The deformation of the thrust nappe ductile shear zone is principal in Nanhuatang area. The zone consists of upper Sinian folded layers of carbonate rock, intensely deformed layer of Yaolinghe Group, and mylonite at the top of Wudangshan Group. The side of the zone tend to south, nappe direction is fron Southwestto Northeast. Characteristic macrostructure consists of thrust fold, shear lens and A-type extensional lineation, and the microstructure consists of σ-type. S-C、plagioclase dominoes、epidote snowball and pressure shadow structures. There are glaucophane-schist layers at the top and bottom of Yaolinghe Group, basic glaucophane-schist at the top and acidic glaucophane-schist at the bottom. Characteristic mineral is crossite. The displacement of the zone is more than 16. 80 km and the pressure is from 5×106 Pa to 3. 8×106 Pa. The deformation of the zone is closely related to bumping of Huabei Old Plate against Yangtze one.