| 青藏高原羌塘中部高压变质带的研究进展及存在问题 |
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| 引用本文： | 张修政,董永胜,王强,但卫.青藏高原羌塘中部高压变质带的研究进展及存在问题[J].地质通报,2018,37(8):1406-1416. |
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| 作者姓名： | 张修政 董永胜 王强 但卫 |
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| 作者单位： | 中国科学院广州地球化学研究所/同位素地球化学国家重点实验室;吉林大学地球科学学院;中国科学院青藏高原地球科学卓越创新中心;中国科学院大学 |
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| 基金项目： | 国家重点研发计划《燕山期重大地质事件的深部过程与资源效应》（编号：2016YFC0600407）、国家自然科学基金项目《羌塘香桃湖地区与早古生代高压变质岩石共生的多期深熔作用》（批准号：41502054） |
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| 摘 要： | 羌塘中部高压变质带是目前青藏高原内部延伸规模最大的高压变质带,是理解特提斯演化的关键地质记录。高压变质带主要沿龙木措-双湖-澜沧江缝合带一线出露,主要由榴辉岩、蓝片岩、石榴子石多硅白云母片岩及少量高压麻粒岩组成。其中,榴辉岩主要出露于戈木、果干加年山、冈玛错、巴青及滇西的勐库地区,主要呈透镜状产于石榴子石多硅白云母片岩中。除巴青地区的榴辉岩外,其余地区榴辉岩的峰期变质温度较低且含有硬柱石及其假象,峰期变质条件位于硬柱石榴辉岩相稳定区域,是洋壳冷俯冲的产物。虽然对于戈木地区榴辉岩锆石成因仍有争议,但已有资料显示,羌塘中部高压变质带主体变质时代集中在晚三叠世,其相关高压变质岩石的折返可能与洋盆的闭合及随后的陆-陆碰撞相关。近期研究表明,羌塘中部可能存在二叠纪低温高压变质岩,折返于大洋俯冲阶段,可能与洋岛或海山的俯冲及引发的俯冲侵蚀作用相关。此外,羌塘香桃湖地区出露早古生代的基性高压麻粒岩,是冈瓦纳大陆北缘陆块拼贴的记录。因此,对羌塘中部高压变质带进行进一步系统的研究工作,对于深入理解冈瓦纳北缘构造演化及古特提斯的俯冲与闭合过程具有重要的意义。
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| 关 键 词： | 青藏高原 羌塘地块 榴辉岩 蓝片岩 古特提斯洋 |
| 收稿时间： | 2018/1/10 0:00:00 |
| 修稿时间： | 2018/3/28 0:00:00 |
High pressure metamorphic belt in central Qiangtang, Tibetan Plateau: Progress and unsolved problems |
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| ZHANG Xiuzheng,DONG Yongsheng,WANG Qiang and DAN Wei.High pressure metamorphic belt in central Qiangtang, Tibetan Plateau: Progress and unsolved problems[J].Geologcal Bulletin OF China,2018,37(8):1406-1416. |
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| Authors: | ZHANG Xiuzheng DONG Yongsheng WANG Qiang and DAN Wei |
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| Institution: | State Key Laboratory of Isotope Geochemistry/Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China,College of Earth Science, Jilin University, Changchun 130061, Jilin, China,State Key Laboratory of Isotope Geochemistry/Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China;CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China and State Key Laboratory of Isotope Geochemistry/Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China;CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China |
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| Abstract: | A 500km-long high-pressure metamorphic belt has been documented in the central Qiangtang Block of northern Tibet, which is thought to have constituted the crucial geological archives of subduction and exhumation of Paleo-Tethys oceanic lithosphere. The high-pressure metamorphic rocks are mostly exposed along the Longmu Co-Shuanghu suture zone, and are composed of eclogites, blueschists, garnet-phengite-schists (Grt-Phn schists), and minor high-pressure mafic granulites. The eclogites in central Qiangtang are reported from Gemu, Guoganjianian Mt., Gangma Co, Baqing, and Mengku area, and occur mainly as blocks or small lenses in Grt-Phn schists. Apart from newly discovered Baqing eclogites, most eclogites from central Qiangtang Block are characterized by low peak temperatures and presence of lawsonite or pseudomorphs of epidote + paragonite, and their peak P-T results lie mainly in the lawsonite-eclogite field. The ages of most eclogites and blueschists from central Qiangtang block have been constrained as Late Triassic which are regarded as the results of closure of the Paleo-Tethys Ocean and following continental collision. Furthermore, the Permian high-pressure metamorphic rocks were also identified and their P-T-t paths revealed a complete evolutional history for the subduction erosion in response to the subduction of seamounts (or oceanic islands). Moreover, the discovery of Silurian high-pressure granulites in the central Qiangtang block indicates the existence of a previous collisional event on the northern margin of the Indo-Australian Gondwana. Hence, further comprehensive studies of the high-pressure metamorphic belt in central Qiangtang will provide valuable insights into the tectonic evolution of the north margin of Gondwana during the early Paleozoic and the opening and closure of the Paleo-Tethys Ocean. |
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| Keywords: | Tibetan Platean Qiangtang block eclogite blueschist Paleo-Tethys Ocean |
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