松潘-甘孜造山带鲜水河断裂与雅拉雪山片麻岩穹窿的关系  

The Relationship between the Xianshuihe Fault Zone and Yala Snow Mountain Gneiss Dome in the Songpan-Ganzi Orogenic Belt

作　　者：吴婵[1] 许志琴[1] A.A.G.WEBB 董汉文[1] 曹汇[1] 程展展 

机构地区：[1]中国地质调查局大陆动力学研究中心中国地质科学院地质研究所,北京100037 [2]School of Earth and Environment,Maths/Earth and Environment Building,The University of Leeds [3]中国石油集团东方地球物理公司华北物探处,河北任丘062252

出　　处：《地质学报》2016年第11期2982-2998,共17页Acta Geologica Sinica

基　　金：中国地质调查局地质调查项目(编号12120115026801);大陆构造与动力学实验室自主基金(编号Z1301-a19)联合资助的成果

摘　　要：片麻岩穹窿是岩浆作用、变质作用和变形作用的共同结果，是造山带的重要构造元素。本次在松潘一甘孜地体内鲜水河大型左旋走滑断裂带北东侧雅拉雪山发现一个片麻岩穹窿，核部为弱面理化花岗岩，边部为面理化花岗岩，紧邻断裂带的花岗岩发生糜棱岩化。锆石LA—ICP—MSUPb测年结果表明，雅拉雪山片麻岩穹窿核部弱面理化花岗岩和边部面理化花岗岩的锆石U—Pb年龄分别为14．51±O．82Ma，14．39±0．23Ma，14．25±0．34Ma和18．2±1．3Ma，因此，该片麻岩穹窿形成于18～14Ma。鲜水河剪切带中的糜棱岩以及花岗岩脉的锆石U—Pb年龄分别为14．57±0．34Ma和16．73±0．97Ma，代表断裂剪切作用时代。该片麻岩穹窿的形成时代与鲜水河断裂带的活动时代基本一致，它是鲜水河断裂带在左行剪切作用过程中岩体部分熔融，并在转化挤压作用下隆升形成的。它的形成代表了鲜水河断裂深部的剪切作用时代，深部的剪切熔融促使了断裂带向南东方向扩展，促进了川滇地块的旋转运动，调节了青藏高原物质的东移，进一步促使了青藏高原东缘上地壳加厚和山脉隆升以及河流下切作用，使片麻岩穹窿分别在12～5．5Ma和4．4～3．1Ma期间，发生快速冷却，冷却速率分别为～61℃／Ma和～146℃／Ma。Gneiss dome is an important structure resulting from magmatism, metamorphism and deforming during orogeny. A gneiss dome is first reported closely along the northern part of the Xianshuihe sinistral strike-slip fault zone in the Songpan-Ganzi block. It is composed of undeformed granite in the core and foliated granite in the edge, whose lithology close to the fault has been mylonitized. LA-ICP-MS U-Pb dating shows that the undeformed granite formed at 14.51-0.82 Ma and the ages of foliated granites are 14.39-0, 23 Ma, 4. 254-0.34 Ma and 18.24-1.3 Ma,which indicates the gneiss dome formed at 18-14 Ma. The U-Pb age of mylonite and granite vein in the Xianshuihe shear zone are estimated 14.57 - 0.34 Ma and 16. 734-0.97 Ma, respectively. These ages show a close relationship between the formation of the gneiss dome and the shearing of the Xianshuihe fault zone that the former results from partial melting and bulging of the upper crustal rocks under the shearing of the latter. And in return, the melting promoted the southeastward spreading of the Xianshuihe fault zone, resulting in the formation of the Red River fault along its southeastern part at 11 - 10 Ma. Meanwhile, they accelerated the clockwise rotation of the Chuandian block, coordinated the eastward motion of the materials in the eastern Tibet and boosted the thickening of the upper crust and subsequent mountain building and river incision. These resulted in rapid cooling of the gneiss dome with a rate of -61℃/Ma and -146℃/Ma at 12-5.5 Ma and 4. 4-3.1 Ma, respectively.

关 键 词：U—Pb年代学 片麻岩穹窿 鲜水河断裂 松潘一甘孜造山带 

分 类 号：P542[天文地球—构造地质学]