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现代地质 ›› 2022, Vol. 36 ›› Issue (01): 244-258.DOI: 10.19657/j.geoscience.1000-8527.2020.047

• 岩石学 • 上一篇    下一篇

北祁连东段柏木峡—门岗峡地区蛇绿岩的识别及其区域构造意义

刘建栋1,2(), 李五福1,2(), 王国良1,2, 董进生1,2, 曹锦山1,2, 李红刚1,2, 赵忠国1,2   

  1. 1. 青海省地质调查院,青海 西宁 810012
    2. 青藏高原北部地质过程与矿产资源重点实验室, 青海 西宁 810012
  • 收稿日期:2018-12-19 修回日期:2020-04-16 出版日期:2022-02-10 发布日期:2022-03-08
  • 通讯作者: 李五福
  • 作者简介:李五福,男,硕士,高级工程师,1982年出生,构造地质学专业,从事区域地质调查研究工作。Email: 15422504@qq.com
    刘建栋,男,工程师,1989年出生,地质学专业,从事区域地质调查研究工作。Email: qhddljd0303@163.com
  • 基金资助:
    中国地质调查局“青海区域地质调查片区总结与服务产品开发(青海省新一轮地质志修编)”项目(12120114079701);“青海1:5万玉龙滩地区四幅区调”项目(1212011121192);“青海省德令哈市哈拉湖西地区四幅1:5万区域地质矿产调查”项目(1212011221151)

Identification of Ophiolites in the Baimuxia-Mengangxia Area in the Eastern Part of the North Qilian Mountains and Their Regional Tectonic Significance

LIU Jiandong1,2(), LI Wufu1,2(), WANG Guoliang1,2, DONG Jinshen1,2, CAO Jinshan1,2, LI Honggang1,2, ZHAO Zhongguo1,2   

  1. 1. Qinghai Geological Survey Institute, Xining, Qinghai 810012, China
    2. The Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources Laboratory, Xining, Qinghai 810012, China
  • Received:2018-12-19 Revised:2020-04-16 Online:2022-02-10 Published:2022-03-08
  • Contact: LI Wufu

摘要:

为加强对北祁连早古生代多岛弧盆系蛇绿混杂岩的调查,选取柏木峡—门岗峡蛇绿岩开展岩相学、年代学和地球化学研究。柏木峡—门岗峡蛇绿岩位于青海省海东市互助县,构造上处于北祁连造山带中东段。由橄榄岩、辉长岩和基性火山岩组成较为完整的蛇绿岩单元。对辉长岩进行单颗粒锆石LA-ICP-MS U-Pb同位素测年,获得206Pb/238U加权平均年龄为(525.2±1.1) Ma(MSWD=0.06),代表了蛇绿岩的形成年龄,相当于早寒武世。岩石地球化学研究表明,该蛇绿岩中的基性火山岩属于拉斑系列,具有洋岛玄武岩的地球化学特征;玄武岩Th/Yb-Nb/Yb和TiO2/Yb-Nb/Yb等构造环境判别图显示,该套蛇绿岩的形成环境与俯冲作用无关。结合详细的野外调查和区域对比,认为该蛇绿岩代表早古生代北祁连洋壳,与玉石沟—川刺沟等蛇绿岩共同构成了达坂山—玉石沟蛇绿岩带。

关键词: 北祁连造山带, 柏木峡—门岗峡蛇绿岩, LA-ICP-MS锆石U-Pb测年, 洋岛玄武岩

Abstract:

In order to strengthen the investigation of Early Paleozoic Archipelagic arc-basin-system ophiolitic mélange in North Qilian,the Baimuxia-Mengangxia ophiolite is selected for petrographic, chronological and geochemistry study.Baimuxia-Mengangxia ophiolite is located in Huzhu County, Haidong City, Qinghai Province,tectonically located in the middle-eastern section of the North Qilian orogenic belt.The ophiolite is mainly composed of peridotite,gabbro and basic volcanic rocks,making up a relatively complete ophiolite unit.Single zircon LA-ICP-MS U-Pb isotope dating of gabbro was carried out, and the weighted average age of 206Pb/238U was (525.2 ± 1.1) Ma (MSWD=0.06).It represents the age of ophiolite formation, corresponding to the Early Cambrian.Petrogeochemical studies show that: The basic volcanic rocks in the ophiolite belong to tholeiite series, showing the geochemical characteristics of oceanic island basalts; in basalts Th/Yb-Nb/Yb and TiO2/Yb-Nb/Yb tectonic discrimination diagrams, it shows that the formation environment of the ophiolite is not related to subduction.Through detailed field investigation and regional comparison, it is considered that the ophiolite represents the northern Qilian oceanic crust of the Early Paleozoic, and together with the ophiolites such as Yushigou-Chuancigou, it constitutes the Dabanshan-Yushigou ophiolite belt.

Key words: North Qilian orogenic belt, Baimuxia-Mengangxia ophiolite, LA-ICP-MS zircon U-Pb dating, OIB

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