青藏高原东南缘次林错岩体晚白垩世—早新生代快速剥蚀  

Rapid exhumation of Cilincuo granite in the southeastern Tibetan Plateauduring Late Cretaceous-Early Cenozoic

作　　者：沈续文 沈晓明 刘静[1] 曾令森[3] 杨超群 葛玉魁 邢宇堃 曾宪阳 王子君[1] 李云帅[1] 李金阳 SHEN Xuwen;SHEN Xiaoming;LIU-ZENG Jing;ZENG Lingsen;YANG Chaoqun;GE Yukui;XING Yukun;ZENG Xianyang;WANG Zijun;LI Yunshuai;LI Jinyang(School of Earth System Science,Tianjin Universily,Tianjin 300072,China;National Instilute of Natural Hazards,Ministry of Emergency Management of China,Beijing 100085.China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Institute of Geology,China Earthquake Ad ministration,Beijjing 100029,China)

机构地区：[1]天津大学地球系统科学学院,天津300072 [2]应急管理部国家自然灾害防治研究院,北京100085 [3]中国地质科学院地质研究所,北京100037 [4]中国地震局地质研究所,北京100029

出　　处：《地质学报》2022年第10期3332-3344,共13页Acta Geologica Sinica

基　　金：国家自然科学基金重点项目“藏东南三江地区新生代构造与地貌协同演化”(编号42030305);国家自然科学基金项目(编号42011540385、U1839203)共同资助的成果;国家重点研发子课题(编号2021YFC3000604)。

摘　　要：青藏高原东南缘是研究构造、地貌演化和气候变化相互作用的理想场所,前人研究主要揭示了晚始新世—早中新世和晚中新世以来的快速剥蚀事件,缺乏晚白垩世—早新生代时期地貌演化过程的研究。次林错花岗岩已有的低温热年代学数据覆盖了整个新生代时期,为探索该区域新生代早期的剥露演化历史提供了重要资料。该岩体新生代早期冷却事件是岩浆冷却单一作用的结果,还是受快速剥蚀作用的影响,目前仍然存疑,需要定量研究。因此,本文结合已有的岩石地化和年代学数据,对次林错花岗岩开展了锆石饱和温度和一维岩浆冷却模拟研究。锆石饱和温度计算结果表明次林错花岗岩的岩浆结晶温度介于647~705℃之间,属低温花岗岩。一维岩浆冷却模拟结果显示岩体侵位时的最小围岩温度为160~120℃,对应深度约为3.7~5.0 km。结合锆石和磷灰石(U-Th)/He年代学数据,本文认为该岩体在晚白垩世—早新生代时期(67~40 Ma)经历了一期剥蚀量至少为2 km的快速剥蚀事件。已发表成果的综合分析表明,此次快速剥露事件可能是整个青藏高原地区广泛存在的构造剥蚀事件,新特提斯洋的俯冲闭合与印亚板块的初始碰撞可能是触发此次大规模区域剥蚀的主要原因。The southeastern Tibetan Plateau is an ideal place to study the interactions among tectonics,geomorphic evolution and climate.Previous studies have mainly revealed two rapid exhumation phases during late Eocene-early Miocene and late Miocene to present,but the evolution process during Late Cretaceous-Early Cenozoic remain unclear.The Cilincuo granite with entire Cenozoic thermochronology data provide important reference for exploring the exhumation evolution history during the early Cenozoic in SE Tibet.However,the cooling event of Cilincuo granite during Early Cenozoic,resulting from magma cooling or rapid exhumation,remains questionable,which needs studying quantitatively.In this study,we review published chronological data,and use zircon saturation thermometers and 1-D magma cooling modelling to constrain the crystallization temperature,minimum emplacement depth and minimum exhumation amount of the Cilincuo granite during the Late Cretaceous-Early Cenozoic.The results of zircon saturation temperatures for Cilincuo granite suggest that the magma crystallization temperature of Cilincuo granite is between 647℃and 705℃,belonging to low temperature granite.1-D magma cooling modelling results suggest that the minimum surrounding rock temperature is 160~120℃,and the corresponding depth is about 3.7~5.0 km.Combining zircon and apatite(U-Th)/He thermochronology data,we suggest that the intrusion experienced a rapid exhumation event of at least 2 km during the Late Cretaceous-Early Cenozoic(67~40 Ma).Our results combined with prevoious published results suggest that this rapid exhumation phase may be a widespread tectonic exhumation event in the Tibetan Plateau,which is probably triggered by the subduction and closure of the New Tethys ocean and the initial collision of the Indo-Asian plate.

关 键 词：青藏高原东南缘 次林错花岗岩 晚白垩世—早新生代 快速剥蚀 锆石饱和温度计 一维岩浆冷却模拟 低温热年代学 

分 类 号：P534.53[天文地球—古生物学与地层学] P534.6[天文地球—地质学] P542