Mesozoic uplift exhumation history of East Kunlun

Abstract

位于中央造山带西段的东昆仑造山带因多期次造山和复杂演化历史而备受关注，约束其中生代隆升剥露历史，对于理解青藏高原大规模隆升在东昆仑地区的扩展及影响颇具意义。东昆仑造山带内中生代侏罗系-白垩系地层缺失严重，体现中生代以来强烈的隆升剥露过程，也是该区热演化的研究难点。本文通过对东昆仑造山带样品的磷灰石、锆石裂变径迹分析和热演化史研究，并结合东昆仑及周缘地区现有低温热年代学研究，识别出东昆仑造山带所经历的五次隆升冷却事件，即201~193Ma（早侏罗世）、172~152Ma（中-晚侏罗世）、120~98Ma（早白垩世末-早白垩世初）、98~20Ma（晚白垩世-中新世）及20~0Ma（中新世至今）。所获5个年龄组响应东昆仑地区所经历的构造热事件，其中201~193Ma年龄组响应南部羌塘地块与昆仑地块的碰撞事件；172~152Ma年龄组为中-晚侏罗世古特提斯洋闭合后，造山后伸展的构造事件的记录；120~98Ma热事件吻合拉萨地块和羌塘地块碰撞事件；98~20Ma年龄组为东昆仑地区长期缓慢剥蚀去顶过程的印证；20~0Ma的快速隆升剥露事件则为东昆仑周缘断裂系活化相伴，多期隆升剥蚀事件均得到地层不整合及沉积记录等研究成果的证实。区内剥蚀起始时间从由南到北逐渐变老，体现东昆仑地区隆升剥蚀的不均一性。;As the western part of the Central Orogenic Belt, the East Kunlun Orogenic Belt draws great attention in the geological community because of its multi-phase orogenesis and complex evolutionary history. Constraining its Mesozoic uplift denudation history has important implications for understanding the expansion and impact of large-scale uplift of the Tibetan Plateau in the East Kunlun region. The absence of the Mesozoic Jurassic-Cretaceous stratigraphy in the East Kunlun Orogenic Belt reflects the intensive uplift and denudation process since the Mesozoic, which is also a difficult research problem in the thermal evolution of the area. In this paper, through the analysis of apatite, zircon fission tracks and thermal evolutionary history of samples within the East Kunlun, we identify five uplift cooling events, i.e. 201~193Ma (Early Jurassic), 172~152Ma (Middle-Late Jurassic), 120~98Ma (Late Early Cretaceous-Early Cretaceous), 98~20Ma (Late Cretaceous-Miocene), and 20~0Ma (Miocene to present). The five age groups obtained respond to the tectonothermal events experienced in the East Kunlun region. The 201~193Ma age group responds to the collision between the Qiangtang Block and the Kunlun Block in the south; the 172~152Ma age group is the record of the tectonic event of post-formation extension after the closure of the Middle-Late Jurassic Paleo-Tethys Ocean; the 120~98Ma thermal event coincides with the collision between the Lhasa Block and the Qiangtang Block; the 98~20Ma age group is the record of the long-term slow denudation process. The rapid uplift and denudation events from 20 to 0Ma are due to the activation of the fault system. The onset of denudation in the area is gradually older from south to north, reflecting the heterogeneity of uplift denudation in the East Kunlun region.