滇西西盟地区前泥盆纪变质岩系的变形构造格架

滇西西盟一带是保山—掸邦地块在我国境内的一个基底岩系出露地区。该地区的前泥盆纪变质岩系可划分成两个构造层，下部为元古代构造层，由变质深度达角闪岩相的怕可杂岩系组成，发育３期南北向的变形构造；上部为早古生代构造层，由低绿片岩相变质的王雅组、允沟组组成，发育两期呈南北向的变形构造。变形构造表明，西盟变质岩系的主期构造格架以怕可—老街子背形叠瓦垛为主导构造要素，由背驮式扩展的向东逆冲的盲逆冲断裂系组成，王雅—允沟反冲叠瓦扇是盲逆冲断裂系的盖层响应变形系统，并以向西逆冲的推覆构造为特征

THE STRUCTURAL FRAMEWORK OF PRE DEVONIAN METAMORPHIC ROCKS IN XIMENG COUNTY, WESTERN YUNNAN

The Ximeng area, western Yunnan, is the only area where the basement of the Baoshan Shan State massif is exposed in China. The pre Devonian metamorphic rocks in this area are divided into the Proterozoic structural layer and the overlying Paleozoic structural layer. The former, comprising the Pake Complex experiencing amphibolite facies metamorphism, is characteristized by three phases of N S trending deformation structures; the latter, consisting of the Wangya Formation and Yungou Formation, is characterized by two phases of N S trending deformation structures and low greenschist facies metamorphism. Detailed structural studies demonstrate that the Laojiezi Pake blind thrust antiformal imbricate structure and the Wangya Yungou backthrusting imbricate system dominate the structural framework of the pre Devonian metamorphic rocks in the Ximeng area. The former is the predominant structure and comprised of eastward overridding thrusts propagating in a piggy back sequence; the latter, which is characterized by the development of the westward thrusting faults and westward verging folds and foliation, is a coeval cover deformation system responsive to the former.