全文快速搜索:          
引用本文:王旭辉,郎兴海,邓煜霖,谢富伟,娄渝明,张赫,杨宗耀. 西藏拉萨地体南缘汤白地区始新世辉绿岩脉——新特提斯洋壳断离的证据[J]. 中国地质, 2019, 46(6): 1336-1355.
WANG Xuhui,LANG Xinghai,DENG Yulin,XIE Fuwei,LOU Yuming,ZHANG He,YANG Zongyao. Eocene diabase dikes in the Tangbai area, southern margin of Lhasa terrane, Tibet: Evidence for the slab breakoff of the Neo-Tethys Ocean[J]. Geology in China, 2019, 46(6): 1336-1355(in Chinese with English abstract).
【打印本页】   【HTML】   【下载PDF全文】   查看/发表评论  下载PDF阅读器  关闭
←前一篇|后一篇→ 过刊浏览    高级检索
本文已被:浏览 41次   下载 65 本文二维码信息
码上扫一扫!
分享到: 微信 更多
西藏拉萨地体南缘汤白地区始新世辉绿岩脉——新特提斯洋壳断离的证据
王旭辉1, 郎兴海1, 邓煜霖1, 谢富伟1, 娄渝明1, 张赫1, 杨宗耀2
1.成都理工大学地球科学学院, 自然资源部构造成矿成藏重点实验室, 四川 成都 610059;2.西南交通大学地球科学与环境工程学院, 四川 成都 611756
摘要:
拉萨地体南缘汤白地区广泛分布新生代的辉绿岩脉。为探讨该辉绿岩脉形成时代、岩石成因和地质意义,对其开展了详细的岩相学、地球化学、锆石U-Pb年代学及Hf同位素研究。LA-ICP-MS锆石U-Pb定年结果显示辉绿岩脉的结晶年龄为(54±1)Ma,表明其形成于早始新世。微量元素地球化学特征显示富集大离子亲石元素(LILEs:如Rb、Sr和Ba),亏损高场强元素(HFSEs:如Nb、Ta和Ti)。与典型的弧岩浆岩、区域上叶巴组和桑日岩群中的玄武岩相比具有较高的Nb、TiO2和Zr含量,在微量元素构造环境判别图解中显示出板内玄武岩地球化学属性。微量元素地球化学特征结合锆石Hf同位素表明岩浆源区除被俯冲板片释放的流体交代的岩石圈富集地幔外,还有软流圈亏损地幔物质加入。汤白辉绿岩脉侵入年龄与区域上林子宗群火山活动峰期接近(52 Ma)。同时结合岩石成因及构造背景,作者认为汤白辉绿岩脉是54~52 Ma新特提斯洋壳断离诱发岩浆作用的产物。根据最新大陆碰撞及板片断离的三维数值模型,暗示了印度板块与欧亚大陆碰撞的起始时间为65 Ma或者更早。
关键词:  拉萨地体  辉绿岩脉  构造背景  板片断离  印度-欧亚大陆碰撞  地质调查工程  西藏
DOI:10.12029/gc20190607
分类号:
基金项目:国家重点研发计划课题(2018YFC0604105),国家自然科学基金项目(41502079、41972084),中国地质调查局项目(DD20160346),西北大学大陆动力学国家重点实验室开放课题基金项目(18LCD04)及深地资源成矿作用与矿产预测重点实验室开放基金项目(ZS1911)联合资助。
Eocene diabase dikes in the Tangbai area, southern margin of Lhasa terrane, Tibet: Evidence for the slab breakoff of the Neo-Tethys Ocean
WANG Xuhui1, LANG Xinghai1, DENG Yulin1, XIE Fuwei1, LOU Yuming1, ZHANG He1, YANG Zongyao2
1.MNR Key Laboratory of Tectonic Controls on Mineralization and Hydrocarbon Accumulation, College of Earth Science, Chengdu University of Technology, Chengdu 610059, Sichuan, China;2.Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, Sichuan, China
Abstract:
Diabase dikes are extensively distributed in the Tangbai area on the southern margin of the Lhasa terrane. In order to discuss their formation age, genesis and tectonic implications, the authors investigated their petrography, geochemistry, zircon U-Pb geochronology and Hf isotope. Zircon U-Pb dating yielded an age of (54±1) Ma for the Tangbai diabase dikes, indicating that they were formed in the Early Eocene. The trace elements are characterized by enrichment of LILEs (such as Rb, Sr and Ba) and depletion of HFSEs (such as Nb, Ta and Ti). Compared with typical arc magmas, Sangri Group basalts and Yeba Formation basalts in this area, the Tangbai diabase dikes have higher values of Nb, TiO2 and Zr. Trace element tectonic discrimination diagrams show that Tangbai diabase dikes fall in intraplate basalts field, and show geochemical affinities with intraplate magmatism. The race element geochemical characteristics and zircon Hf isotopic data suggest that the diabase dikes were likely derived from enriched lithospheric mantle which had been metasomatized by slab-derived fluids during previous subductions, and mixed with upwelling ashospheric mantle. The intrusion age of Tangbai diabase dikes was close to the peak period (52 Ma) of Linzizong volcanic activity. Combined with their genesis and tectonic setting, the authors hold that the formation of the Tangbai diabase dikes was related to slab break-off of the northward subduction of the Neo-Tethyan slab ca. 54~52 Ma in age. In addition, according to the latest 3-D numerical models of continental collision and slab break-off, it is shown that the onset of India-Eurasia continental collision should have occurred at 65 Ma or earlier.
Key words:  Lhasa terrane  diabase dikes  tectonic setting  slab break-off  India-Eurasia continental collision  geological survey engineering  Tibet