拉萨-羌塘板块碰撞——来自西藏阿索晚白垩世红层的约束  

Lhasa-Qiangtang collision:Constraints from Late Cretaceous red beds in Asa,Tibet

作　　者：曾先进 王明[1,2] 范建军 罗安波[1] 曾孝文 李航 申迪[1] ZENG Xianjin;WANG Ming;FAN Jianjun;LUO Anbo;ZENG Xiaowen;LI Hang;SHEN Di(College of Earth Science,Jilin University,Changchun 130061,Jilin,China;Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Changchun 130061,Jilin,China)

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]东北亚矿产资源评价自然资源部重点实验室,吉林长春130061

出　　处：《地质通报》2021年第9期1428-1442,共15页Geological Bulletin of China

基　　金：国家自然科学基金青年科学基金项目《青藏高原羌唐南部埃迪卡拉纪地层研究》(批准号:41602230);中国博士后科学基金第九批特别资助项目《藏北羌塘南部晚古生代基性岩墙群的成因及构造意义研究》(编号:2016T90248);中国地质调查局项目《西藏尼玛县尼则等三幅区域地质调查(班公湖-怒江成矿带铜多金属矿资源基地调查)》(编号:DD20160026)。

摘　　要：晚白垩世拉萨板块与羌南-保山板块陆陆碰撞事件是青藏高原形成与演化研究的热点。西藏阿索地区的晚白垩世竟柱山组和马莫勒组是阿索地区该时期最具代表性的沉积记录。目前有关其形成时代及沉积环境的研究非常薄弱,限制了对于区域构造背景等方面的认识。对西藏阿索地区的晚白垩世竟柱山组的形成时代、沉积环境进行了研究。碎屑锆石LA-ICP-MS U-Pb定年结果表明,竟柱山组碎屑锆石样品中的最小单颗粒锆石年龄为89±5 Ma,阿索地区竟柱山组南部侵入的闪长岩岩脉获得了88 Ma的锆石U-Pb年龄,进一步表明竟柱山组的沉积时代应在90 Ma左右。结合该地区同时代马莫勒组的研究成果,认为竟柱山组沉积于冲积扇环境,而马莫勒组为辫状河-三角洲环境。在沉积物源方面,竟柱山组物源更偏向汇聚环境下的岛弧,而马莫勒组则具有更复杂的物源。竟柱山组和马莫勒组作为拉萨-羌塘板块碰撞造山作用在地表的沉积响应,共同记录了晚白垩世的地壳抬升过程。The continent-continent collision between Lhasa plate and Qiangtang-Baoshan plate has been a spotlight in the study of Tibetan Plateau’s formation and evolution.In Asa area,Late Cretaceous Jingzhushan Formation and Mamole Formation are the most representative deposits in that time.However,the limited research on their ages and sedimentary environment has limited the understanding of the regional tectonic background.This paper reports the studies on the age and sedimentary environment of the Late Cretaceous Jingzhushan Formation in Asa of Tibet.The detrital zircon LA-ICP-MS U-Pb dating results show that the smallest single grain zircon obtained from the Jingzhushan Formation yields age of 89±5 Ma.The diorite dyke intruding into the south part of Jingzhushan Formation gives a zircon U-Pb age of 88 Ma,which further indicates that the sedimentary age of the Jingzhushan Formation in this area should be around 90 Ma.Combined with the research results of the contemporary Mamole Formation in this area,it is suggested that the Jingzhushan Formation was deposited in the alluvial fan environment,while the Mamole Formation in the braided river-delta environment.In terms of sediment sources,the source of Jingzhushan Formation tends to be an island arc provenance under converging environment,while the Mamole Formation has a more complicated source.The Jingzhushan Formation and the Mamole Formation,as the sedimentary response of the Lhasa-Qiangtang plate collision orogeny on the surface,jointly record the crustal uplift process in the Late Cretaceous.

关 键 词：西藏 晚白垩世 碎屑锆石 竟柱山组 沉积环境 锆石U-PB定年 

分 类 号：P534.53[天文地球—古生物学与地层学] P541[天文地球—地质学]