藏东巴青县北部酉西岩组构造片理形成及构造意义  

Forming and tectonic significance of the Youxi tectono-schistose formation, north Baqen county,eastern Tibet

作　　者：王根厚[1] 贾建称[1] 万永平[1] 张维杰[1] 周志广[1] 李秋实[1] 杨国东[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地学前缘》2006年第4期180-187,共8页Earth Science Frontiers

基　　金：国家自然科学基金资助项目(49802019);中国地质调查局资助项目"1:25万仓来拉幅区域地质调查"(200313000001)

摘　　要：西藏巴青县以北酉西岩组主要由石英构造片岩、钠长石英构造片岩、白云母石英构造片岩组成，构造片理为近水平韧性剪切作用产物。宏观上构造片理构成了宽缓的背形、向形褶皱构造，构造片理上广布-期透入性拉伸线理，将构造片理展平，分布在透入性片理上的线理具明显优选方位，方向为280～100°。根据微观构造分析，韧性剪切指向为自西向东运动，构造片岩内发育多硅白云母。多硅白云母电子探针分析结果认为其形成环境为低温高压蓝片岩相，变质温度确定为320-500℃、压力0．6～1．1GPa。多硅白云母^40Ar／^39Ar测年结果为（230±1）Ma，为中三叠世末期。酉西岩组构造片理（韧性剪切作用）与查吾拉-吉塘印支期构造岩浆带形成密切相关。Youxi schistose formation outcrops north to the Baqen county, Tibet, is composed of quartz schist, albite-quartz schist, and muscovite-quartz schist with penetrative schistosity and mineral lineation. The schistosity in the formation exhibits structural styles of open antiform and synform, and the mineral lineation shows preferred orientation at 100-280° ,Micro-fabric analysis for the ductile shear deformation indicates the eastward kinematics. Electron Microprobe analyses of the metamorphic mineral assemblage identified a composition of phengite, which was further determined to be formed at a temperature of 320-500 ℃ and a high-pressure of 0. 6-1.1 GPa. The temperature-pressure condition represents a grade of blueschist metamorphism. The phengires was dated at （230± 1） Ma by the 40 Ar/39 Ar method. We concluded that the forming of the Youxi schistose formation was closely affiliated with the Chawula-Jitang Indosinian tectono-magmatic event within eastern Tibet.

关 键 词：藏东巴青县 酉西岩组 韧性剪切 构造片理 多硅白云母 

分 类 号：P313[天文地球—固体地球物理学]