地学前缘 ›› 2011, Vol. 18 ›› Issue (3): 66-78.

• 论文 • 上一篇    下一篇

拉萨地体内松多榴辉岩的同碰撞折返：来自构造变形和40Ar-39Ar年代学的证据

李化启，许志琴，杨经绥，唐哲民，杨梅   

  1. 1. 中国地质科学院 地质研究所， 北京 100037
    2. 中国科学院 研究生院， 北京 100049
  • 收稿日期:2011-01-10 修回日期:2011-02-28 出版日期:2011-05-22 发布日期:2011-05-20
  • 作者简介:李化启(1979—)，男，博士后，构造地质学专业，主要从事青藏高原高压超高压变质带的构造动力学研究。Email：muzi_7540@163.com

Syncollisional exhumation of Sumdo eclogite in the Lhasa Terrane, Tibet: Evidences from structural deformation and 40Ar39Ar geochronology.

  1. 1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China
    2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2011-01-10 Revised:2011-02-28 Online:2011-05-22 Published:2011-05-20
  • Supported by:

    中国地质调查局地质调查项目（1212010818035）；中国地质科学院地质研究所基本科研业务费项目（J0918）；国家自然科学基金创新研究群体项目（40921001）

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摘要：

松多地区的区域构造变形与糜棱质白云母石英片岩和绿片岩的白云母单矿物40Ar39Ar年代学测试表明拉萨地体内的松多地区于220~240 Ma经历过印支期碰撞造山事件。这次造山事件为晚二叠世松多榴辉岩带代表的古特提斯洋盆消失闭合之后北拉萨地体与南冈瓦那大陆碰撞的结果。该区榴辉岩与退变榴辉岩白云母和角闪石的40Ar39Ar测年结果也为220~240 Ma，且退变榴辉岩经历了与围岩一致的同构造变形，说明榴辉岩折返退变的时代和碰撞造山的时代一致。即碰撞造山的强挤压及挤压转换作用应是本区榴辉岩折返出露的主要机制。拉萨地体内印支晚期（210~190 Ma）大规模花岗岩带的发育从另一个侧面说明松多榴辉岩的折返与造山后伸展和区域内大规模花岗岩浆活动等后期热事件没关系，应为同碰撞折返机制。研究结果为高压变质岩石的同碰撞折返研究提供了一个具体实例和翔实的地质资料。

关键词: 拉萨地体, 榴辉岩, 同碰撞折返, 构造变形, 40Ar39Ar年代学

Abstract:

The structural deformation and muscovite and amphibole 40Ar39Ar dating of muscovite quartz schist, eclogite and retrograde eclogite indicate that an Indosinian orogenesis occurred in 220240 Ma in the Lhasa Terrane, which caused the closure of PaleoTethys ocean basin and the collision between the northern Lhasa Terrane and southern Gondwana. The accordance of muscovite and amphibole 40Ar39Ar dating among eclogite, retrograde eclogite and muscovite quartz schist shows that the eclogite exhumation and Indosinian collisional orogenesis occurred simultaneously, which suggests that the regional ductile extrusion should be the main mechanism for the exhumation of Sumdo eclogite. The existence of large scale granite belt of late Indochina EPoch in the Lhasa Terrane, with the high precision single zircon UPb ages of 210190 Ma, confirms the syncollisional exhumation of eclogite from the another side, indicating that the eclogite exhumation had no relation to the postorogenic extension and granite activities.

Key words:  Lhasa Terrane, eclogite, syncollisional exhumation, structural deformation, 40Ar39Ar chronology

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