地学前缘 ›› 2019, Vol. 26 ›› Issue (2): 157-168.DOI: 10.13745/j.esf.sf.2019.3.9

• 陆缘构造–岩浆与成矿作用 • 上一篇    下一篇

西藏拉萨地块西部赛利普地区捷嘎组火山岩的年代学、地球化学及地质意义

韦天伟，康志强，杨锋，冉孟兰，李强，韦乃韶，刘迪， 曹延，陈欢，李岱鲜   

  1. 1. 桂林理工大学 地球科学学院, 广西 桂林 541004
    2. 广西有色金属隐伏矿床勘查及材料开发协同创新中心, 广西 桂林 541004
  • 收稿日期:2018-12-22 修回日期:2019-02-23 出版日期:2019-03-30 发布日期:2019-03-30
  • 通信作者: 康志强(1979—)，男，教授，博士生导师，主要从事岩石、矿床地球化学研究。
  • 作者简介:韦天伟(1992—)，男，硕士研究生，矿物学、岩石学、矿床学专业。E-mail:1393688163@qq.com
  • 基金资助:
    国家重点研发计划项目(2016YFC0600407)；国家自然科学基金项目(41863005，41463001)；广西自然科学基金项目(2016GXNSFAA380012)

Geochronology, geochemistry and geological significance of volcanic rocks in the Jiega Formation, western Lhasa block, Sailipu, Tibet

WEI Tianwei，KANG Zhiqiang，YANG Feng，RAN Menglan，LI Qiang， WEI Naishao，LIU Di，CAO Yan，CHEN Huan，LI Daixian   

  1. 1. College of Earth Sciences, Guilin University of Technology, Guilin 541004, China
    2. Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi, Guilin 541004, China
  • Received:2018-12-22 Revised:2019-02-23 Online:2019-03-30 Published:2019-03-30
  • Supported by:
     

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摘要： 拉萨地体广泛分布有中生代的火山岩，了解它们的成因机制和构造背景对认识青藏高原新生代以前的演化历史意义重大。该文首次对出露于中拉萨地块西部赛利普地区捷嘎组火山岩进行了系统的锆石年代学、主量和微量元素地球化学研究。结果显示，捷嘎组火山岩主体为玄武岩、玄武安山岩及安山岩，属中钾钙碱性系列，精确的LA-ICP-MS锆石U-Pb定年获得了(108.5±1.0) Ma的年龄值。捷嘎组火山岩整体上富集Rb、Th、U等大离子亲石元素，亏损Nb、Ta、Ti等高场强元素，具有典型的岛弧火山岩特征。稀土元素配分模式主要表现为轻稀土元素富集右倾型，少数具有较平坦的配分模式，Eu显示弱的负异常，表明岩浆的分异程度较低。经讨论，认为捷嘎组火山岩很可能是在新特提斯班公湖—怒江洋盆南向俯冲消减的构造背景下，由于俯冲板片发生回转导致软流圈上涌从而诱发被交代的岩石圈地幔部分熔融而形成。

 

关键词: 岛弧火山岩, 锆石LA-ICP-MS U-Pb定年, 捷嘎组, 赛利普, 拉萨地块, 西藏

Abstract: Mesozoic magmatic rocks are widely distributed in the Lhasa terrane, and the understanding of their petrogenesis and geodynamic setting may yield important information on the pre-Cenozoic geohistory of the Tibetan Plateau. In this paper, we carried out studies for the first time on the system zircon geochronology and major and trace elemental geochemistry of the Jiega Formation in the Sailipu area in western Lhasa block. The results show that the Jiega Formation has mainly andesite, basalt-andesite and basalt belonging to medium potassium calc alkaline series and is aged at 108.5±1.0 Ma by accurate LA-ICP-MS U-Pb dating. It is enriched in LILE Rb, Th, U and depleted in HFSE Nb, Ta, Ti, typical of island arc volcano rock. The REE patterns revealed enrichment of LREE with some flatness and weak negative Eu anomaly, indicating some low level magmatic differentiation. We conclude that the Jiega Formation volcano rocks were probably formed by partial melting of the metasomatic lithospheric mantle induced by upwelling of asthenosphere from the rotation of subducted slabs under the tectonic setting of the Bangong LakeNu River southward subduction of the Neo-Tethys.

Key words: island arc volcanic rocks, zircon LA-ICP-MS U-Pb dating, Jiega Formation, Sailipu, Lhasa block, Tibet

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