冈底斯弧的岩浆作用:从新特提斯俯冲到印度-亚洲碰撞  

The Gangdese arc magmatism:from Neo-Tethyan subduction to Indo-Asian collision

作　　者：张泽明[1] 丁慧霞[2] 董昕[1] 田作林[1] ZHANG Zeming;DING Huixia;DONG Xin;TIAN Zuolin(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地学前缘》2018年第6期78-91,共14页Earth Science Frontiers

基　　金：国家重点研发计划项目(2016YFC060310);国家自然科学基金项目(41472056,41602062);中国地质调查局项目(DD20160201)

摘　　要：位于青藏高原南部的冈底斯岩浆弧形成于中生代新特提斯大洋岩石圈的长期俯冲过程中,而且在印度与亚洲大陆碰撞过程中叠加了强烈的新生代岩浆作用,是世界上典型的复合型大陆岩浆弧,已经成为研究汇聚板块边缘岩浆作用和大陆地壳生长与再造的天然实验室。基于对现有研究成果的总结,我们将冈底斯岩浆弧的岩浆构造演化划分为5个阶段:第1阶段发生在晚白垩世之前,以新特提斯洋岩石圈长期正常俯冲和钙碱性弧岩浆岩的发育为特征;第2阶段发生在晚白垩世时期,以活动的新特提斯洋中脊发生俯冲和强烈的岩浆作用与显著的新生地壳生长为特征;第3阶段发生在晚白垩世晚期,以残余的新特提斯大洋岩石圈俯冲和正常弧型岩浆作用为特征;第4阶段发生在古新世至中始新世,以印度与亚洲大陆碰撞、俯冲的新特提斯洋岩石圈回转和断离,及其诱发的幔源岩浆作用、新生和古老地壳的强烈再造为特征;第5阶段为发生在晚渐新世到中中新世的后碰撞阶段,深俯冲印度岩石圈的回转和断离,或加厚岩石圈地幔的对流移去导致了加厚下地壳的部分熔融和埃达克质岩石的广泛发育,同时伴随幔源钾质超钾质岩浆作用。冈底斯弧岩浆作用与岩浆成分的系统时空变化很好地记录了从新特提斯洋俯冲到印度亚洲大陆碰撞的完整构造演化过程。The Gangdese magmatic arc,located in southern Tibet,was formed during the long-lasting subduction of the Neo-Tethyan oceanic lithosphere and subsequent collision between the Indian and Asian continents,typical of composite continental magmatic arc.Therefore,the arc is a natural laboratory for studying subduction-related magmatism and continental crust growth.Based on a synthesis of available research results,we propose that the Gangdese arc experienced five stages of tectonic-magmatic events during its formation and evolution.The first stage of magmatism occurred before the Late Cretaceous,characterized by normal subduction of the Neo-Tethyan oceanic lithosphere and formation of subductionrelated magmatic rocks.The second stage is related to subduction of an active Neo-Tethyan mid-oceanic ridge,featuring extensive Late Cretaceous magmatism and juvenile crustal growth.The third stage of the latest Late Cretaceous arc magmatism occurred during subduction of the residual Neo-Tethyan oceanic lithosphere.The fourth stage of Paleocene to middle Eocene magmatic flare-up resulted from slab roll-back and break-off of subducted Neo-Tethyan ocean during the Indo-Asian collision,marked by significant thickening and partial melting of juvenile and old crusts.And the fifth and latest post-collisional magmatism involved formation of thickened lower crust-derived adakitic rocks and mantle-derived potassic to ultrapotassic volcanic rocks during the late Oligocene to middle Miocene,induced probably by the roll-back and break-off of the deeply subducted Indian lower crust and mantle lithosphere or by convective removal of the thickened Gangdese arc mantle lithosphere.The systematic temporospatial variations of magmatic events and magmatic compositions of the Gangdese arc provide an excellent record of tectonic evolution from the Neo-Tethyan ocean subduction to India-Asia continental collision.

关 键 词：冈底斯弧岩浆作用 新特提斯洋俯冲 印度-亚洲大陆碰撞 青藏高原南部 

分 类 号：P588.115[天文地球—岩石学] P542.5[天文地球—地质学]