羌塘中部高压变质带的退变质作用及其构造侵位  

Retrograde metamorphism and tectonic emplacement of high pressure metamorphic belt in central Qiangtang Tibet

作　　者：董永胜 李才 施建荣 王生云 

机构地区：[1]Jilin Univ, Coll Earth Sci, Changchun 130061, Peoples R China

出　　处：《岩石学报》2009年第9期2303-2309,共7页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40872146和40672147);中国地质调查局(1212010811048和121201081801)项目资助

摘　　要：羌塘中部的高压变质带主要由榴辉岩、石榴石白云母片岩和蓝片岩等组成,它们在遭受高压变质作用之后折返,构造侵位于晚古生代展金组地层中,二者以韧性变形带为接触边界。本文以高压变质带中的榴辉岩和韧性变形带为研究对象,讨论了高压变质带折返过程中的退变质作用特征及折返时代。研究表明,榴辉岩在高峰期变质作用之后的折返过程中经历了由榴辉岩相→蓝片岩相→绿帘角闪岩相的退变质作用演化过程;在高压变质带构造侵位过程形成的韧性变形带中,白云母石英片岩的白云母^(40)Ar-^(39)Ar坪年龄为219±2Ma。高压变质带在219Ma左右构造侵位于展金组地层中,并于214Ma之前最终抬升出露地表。The high pressure metamorphic belt, located in central Qiangtang Tibet, is mainly composed of eclogite, garnet-phengite schist and blueschist. They underwent the exhumation after high pressure metamorphism and tectonically emplaced into the Late Paleozoic epimetamorphic rocks. The high pressure metamorphic belt contacts with epitmetamorphic rocks by a ductile deformed zone. In this paper, based on studies of both the eclogite and the ductile deformed zone, exhumation age and retrograde metamorphic characteristics are discussed. It is proved that the eclogite underwent retrograde metamorphic evolution after peak metamorphisin, from eclogite facies, blueschist facies to epidote-amphibolite facies. (40)Ar-(39) Ar dating of muscovite from muscovite-quartz schist, in the ductile deformed zone, obtains the plateau age of 219 +/- 2Ma, which represents the emplacing age of the high pressure metamorpbic belt into the strata of Zhanjin Formation. Moreover, they were uplifted toward surface before 214Ma ago.

关 键 词：羌塘中部 高压变质带 退变质作用 构造侵位 central high pressure 韧性变形带 榴辉岩相 白云母 折返过程 蓝片岩相 Late Paleozoic 高压变质作用 plateau age 作用特征 云母片岩 演化过程 研究对象 晚古生代 角闪岩相 

分 类 号：P58[天文地球—岩石学]