阿尔金南缘构造带西段新元古代—早古生代变质岩系的变质作用  

Metamorphism of the Neoproterozoic-Early Paleozoic Metamorphic Series in the Western Segment of the Southern Altyn Tagh Tectonic Belt

作　　者：覃小锋[1] 夏斌[1] 李江[2] 黎春泉[2] 陆济璞[2] 许华[2] 周府生[2] 胡贵昂[2] 李乾[2] 

机构地区：[1]中国科学院广州地球化学研究所,广州510640 [2]广西区域地质调查研究院,广西桂林541003

出　　处：《吉林大学学报（地球科学版）》2007年第5期856-867,共12页Journal of Jilin University：Earth Science Edition

基　　金：中国地质调查局区域地质调查项目(19991300008091)

摘　　要：阿尔金南缘构造带西段新元古代一早古生代变质岩系为一套绿片岩相一低角闪岩相的中浅变质岩系，并形成绢云母-白云母带、黑云母带和石榴石-角闪石带3个递增变质带。通过对石榴石-角闪石带变质作用P-T轨迹的深入研究表明，其经历了3个阶段变质作用：即经历了俯冲碰撞深埋到30～35km深度的中高压变质作用（M1），压力可达7．27×10^8～9．63×10^8Pa；随后经历了快速抬升所导致的近等温降压变质过程（M2），压力降至4．1×10^8～5．62×10^8Pa；晚期经历了降温降压退变质作用（M3）。整个过程为顺时针方向演化的P—T轨迹，其地质动力学过程属于较典型的板块俯冲碰撞→抬升模式，表明阿尔金南缘构造带的地质构造演化经历了俯冲碰撞及碰撞后的快速抬升过程。The Neoproterozoic--Early Paleozoic metamorphic series in the western segment of the southern Altyn Tagh tectonic belt is lithologically composed of the middle--shallow metamorphic series containing three metamorphic zones of progressive metamorphism from greenschist facies to low-amphibolite facies, namely, sericite-- muscovite zone, biotite zone and garnet-- hornblende zone. The detailed study of metamorphic p--T path from garnet--hornblende zone indicates three metamorphic evolutionary stages： the middle--high pressure metamorphism（M3 ） probably related to subduction and collision between ancient island arc and plate,at a depth of 30--35 km in response to crustal tectonic thickening at probable 7.27×10^8-9. 63 × 10^8pa. Subsequent isothermal decompression process（M2 ） took place at about 4.1 ×10^8 --5.62 × 10^8 Pa as a result of rapid exhumation and the late retrograde metamorphic evolutionary stage（M3 ） at decreased temperature and pressure. They make up a clockwise p--T evolutionary path and their geodynamic settings belong to those of plate collision and orogenic uplifting, indicating that the southern Altyn Tagh tectonic belt once experienced processes of subduction, collision and rapid uplifting.

关 键 词：新元古代-早古生代变质岩系 变质作用P—T轨迹 高压变质作用 阿尔金南缘构造带西段 

分 类 号：P588.3[天文地球—岩石学] P542.2[天文地球—地质学]