西藏东部嘉玉桥变质杂岩中片理化岩组主期面理形成及构造意义

西藏东部嘉玉桥变质杂岩中片理化岩组剪切运动方向为ＳＥ１４０°—ＮＷ３２０°，应变测量求得富林参数Ｋ平均值为２１３，表明主期面理变形为单剪与收缩机制的复合产物。由石英位错密度估算其差应力值平均为１４９５ＭＰａ，白云母形成温度３８３℃。经４０Ａｒ ３９Ａｒ法年龄测定，获得主期变形时间为（１６４７±１３３）Ｍａ（白云母）～（１６６２７±０９９）Ｍａ（角闪石）。因此，嘉玉桥片理化岩组主期变形与区域上班公湖—怒江缝合带的形成演化有着密切的关系。

FORMATION AND TECTONIC SIGNIFICANCE OF THE MAIN PHASE FOLIATION OF THE JIAYUQIAO SCHISTOSE FORMATION COMPLEX IN EASTERN TIBET

The Jiayuqiao schistose formation complex in eastern Tibet consists dominantly of quartz schist, albite schist and muscovite schist and the shear planes strike 320° and the corresponding Flinn parameter K is 2.13 on the average, implying that the main phase deformation is a compound of simple shear and contraction. The differential stress value estimated by quartz dislocation density is 149.5 MPa and the formation temperature of muscovite is 383.27 ℃. The ages of the main phase deformation determined by the 40 Ar/ 39 Ar method are （164.7±1.33） Ma （muscovite） to （166.27±0.99） Ma （hornblende）. The above mentioned data indicate that the main phase deformation was synchronous with the exhumation of the Jiayuqiao metamorphic complex and took place essentially at the same time as the Early Middle Jurassic oceanic crust spreading of the Bangong Co Nujiang suture zone.