喜马拉雅碰撞造山过程:变质地质学视角  

The Himalayan collisional orogeny:a metamorphic perspective

作　　者：王佳敏[1] 吴福元[1] 张进江[2] Gautam KHANAL 杨雷 WANG Jiamin;WU Fuyuan;ZHANG Jinjiang;Gautam KHANAL;YANG Lei(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,ChineseAcademyofSciences,Beijing100029,China;School of Earth and Space Sciences,PekingUniversity,Beijing 100871,China;Department of Mines and Geology of Nepal,Kathmandu 44600,Nepal;College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]北京大学地球与空间科学学院,北京100871 [3]尼泊尔地质矿产部,尼泊尔加德满都44600 [4]成都理工大学地球科学学院,四川成都610059

出　　处：《地质学报》2022年第9期3128-3157,共30页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41972065,41888101);第二次青藏高原综合科学考察研究项目(编号2019QZKK0703);中国科学院青年创新促进会项目(编号2022065)联合资助的成果。

摘　　要：本文从变质地质学视角出发,介绍了喜马拉雅造山带的研究意义、地质概况和近年来作者在喜马拉雅碰撞造山过程研究中的进展。喜马拉雅造山带是威尔逊旋回中陆陆碰撞造山带的典型代表,从中揭示的大陆碰撞造山过程、规律及效应,可为探索地球从古至今的碰撞造山带演化研究所借鉴。其中,大陆碰撞造山机制的研究是其核心内容。大陆碰撞造山机制存在临界楔和隧道流两种端元模型之争,其分别对造山带核部高级变质岩折返的P-T-t轨迹和时空演化序列进行了不同的预测。上述争议可通过研究喜马拉雅核部高级变质岩(高喜马拉雅)的P-T-t轨迹和折返过程来限定,据此可将喜马拉雅碰撞造山过程划分为三个演化阶段。阶段一:60~40 Ma,软碰撞期,造山带地壳加厚至约40 km并发生小规模部分熔融,这些早期地壳加厚记录大多已被剥蚀,零星保存于前陆飞来峰和北喜马拉雅片麻岩穹隆中;喜马拉雅山从海平面以下抬升至>1000 m。阶段二:40~16 Ma,硬碰撞期,造山带地壳加厚至60~70 km,发生大规模高级变质和深熔作用,高喜马拉雅内部的三个次级岩片沿着“原喜马拉雅逆冲断层”、“高喜马拉雅逆冲断层”、“主中央逆冲断层”顺序式向南挤出,形成了现今喜马拉雅造山带的核部主体,地壳堆叠使喜马拉雅山快速隆升至≥5000 m。阶段三:16~0 Ma,晚碰撞期,造山带山根榴辉岩化发生局部拆沉,但大陆汇聚仍在持续、造山带尚未发生垮塌,小喜马拉雅折返、前陆盆地形成,喜马拉雅山达到和维持现今平均高度~6000 m。因此,喜马拉雅生长过程的一级次序是顺序式向南扩展的,受控于临界楔模型,而隧道流只起次级作用。山根深部热流过程对造山带的地壳结构和地表高程有巨大的改造作用。未来对喜马拉雅造山带的变质地质学研究可能存在以下几个关键科学问题:(1)喜马拉雅极端变质�From a metamorphic perspective, this paper introduces the research significance, a geological overview of the Himalaya, and the authors’ research progress on the Himalayan collisional orogenic process in recent years. The Himalayan orogenic belt is a prototype of the continental collisional orogen in the Wilson cycle. The continental collisional process, rules and effects revealed from the Himalaya can be used as a reference for exploring the evolution of collision orogenic belts on Earth from ancient times to the present. Among them, the research on the orogenic mechanism of continental collision is its primary content. Specifically, the controversy of continental collision orogeny mechanisms lies in two endmember mechanisms: Critical Wedge and Channel Flow, which respectively predicted different P-T-t paths and exhumation spatio-temporal sequences of high-grade metamorphic rocks in the orogenic core. The above disputes can be constrained by studying the P-T-t paths and exhumation processes of the Himalayan Metamorphic Core(Greater Himalayan Crystalline complex). Consequently, the Himalayan collisional orogeny can be divided into three evolutionary stages. Stage one: 60~40 Ma, “soft” collision period;the crust was thickened to ~40 km and small-scale partial melting occurred;most of these early crustal thickening records have been denuded and are sporadically preserved in the foreland klippes and the northern Himalayan gneiss domes;the Himalaya has risen from below sea level to >1000 meters. Stage two: 40~16 Ma, “hard” collision period;the crust was thickened to 60~70 km, and abundant high-grade metamorphism and anatexis occurred;The three sub-slabs in the Greater Himalayan Crystalline complex were extruded southward sequentially along the "Eo-Himalayan Thrust", "High Himalayan Thrust" and "Main Central Thrust", forming the core of the Himalayan orogenic belt;the duplex caused uplift of the Himalaya to ≥5000 meters. Stage three: 16~0 Ma, Late collision period;the orogenic root underwent localized foun

关 键 词：喜马拉雅 大陆碰撞造山 地壳加厚 山脉隆升 临界楔和隧道流 P-T-T轨迹 

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