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现代地质 ›› 2022, Vol. 36 ›› Issue (03): 812-823.DOI: 10.19657/j.geoscience.1000-8527.2022.024

• 岩石学 • 上一篇    下一篇

准噶尔盆地西北缘中拐凸起石炭纪安山岩年代学、地球化学特征及其构造意义

邵龙飞1(), 于福生1(), 王丹丹2, 李超3   

  1. 1.中国石油大学(北京) 地球科学学院,北京 102249
    2.河北省地质矿产勘查局第五地质大队 海洋地质调查所,河北 唐山 063000
    3.中国石油集团 东方地球物理勘探公司乌鲁木齐分院,新疆 乌鲁木齐 830016
  • 收稿日期:2021-10-17 修回日期:2022-05-02 出版日期:2022-06-10 发布日期:2022-07-19
  • 通讯作者: 于福生
  • 作者简介:于福生,男,教授,博士生导师,1969年出生,矿产普查与勘探专业,主要从事构造地质学、盆地构造解析与三维模拟、构造物理模拟、数值模拟研究。Email: fushengyu@cup.edu.cn
    邵龙飞,男,硕士研究生,1996年出生,地质学专业,主要从事构造地质学研究。Email: 569504887@qq.com

Geochronology, Geochemistry,and Tectonic Significance of Carboniferous Andesite in the Zhongguai Uplift, Northwestern Margin of the Junggar Basin

SHAO Longfei1(), YU Fusheng1(), WANG Dandan2, LI Chao3   

  1. 1. School of Earth Sciences, China University of Petroleum, Beijing 102249, China
    2. Marine Geological Survey Institute of the Fifth Geological Brigade of Hebei Bureau of Geology and Mineral Resources, Tangshan, Hebei 063000, China
    3. Urumqi Branch of CNPC Oriental Geophysical Exploration company, Urumqi, Xinjiang 830016, China
  • Received:2021-10-17 Revised:2022-05-02 Online:2022-06-10 Published:2022-07-19
  • Contact: YU Fusheng

摘要:

为加深对中亚造山带西段石炭纪构造背景的认识,对准噶尔盆地西北缘中拐凸起金龙10井区石炭纪安山岩岩心样品开展岩相学、年代学和地球化学研究。安山岩的LA-ICP-MS锆石U-Pb定年结果显示,其结晶年龄为(322.4±1.1) Ma,属中石炭世。地球化学分析结果表明,研究区安山岩属于低钾-中钾钙碱性岩石系列,其稀土元素配分曲线均略向右倾,具微弱的Eu负异常;微量元素原始地幔标准化蛛网图显示整体相对富集Pb和大离子亲石元素Rb、Ba等,亏损高场强元素Nb、Ta、Zr等,具有消减带弧火山岩的特征。安山岩的Th/La、Th/Ce和Lu/Yb值均低于大陆地壳的平均值,而接近幔源岩浆的比值。研究区安山岩属于正常的岛弧火山岩,源于富水地幔楔,是由俯冲板片脱水产生的流体交代地幔楔发生部分熔融所形成的。结合区域地质背景并对比相近时期岩浆岩,综合认为研究区安山岩形成于大陆弧环境,为西准噶尔残余洋盆俯冲消减作用的产物,且残余洋盆在(322.4±1.1) Ma时还未完全关闭。

关键词: 准噶尔盆地西北缘, 中拐凸起, 石炭纪, 安山岩, 年代学, 地球化学

Abstract:

To deepen our understanding in the Carboniferous tectonic background in the western Central Asian Orogenic Belt, drill-core samples of andesite in Jinlong 10 well area of Zhongguai uplift (northwestern margin of Junggar basin) were studied via petrography, chronology and geochemistry. The results show that our andesite samples are low-K to medium-K calc-alkaline, with slightly right-inclining REE diagram and weakly negative Eu anomaly. In the primitive mantle-normalized spider diagram, the rocks have Pb and LILE (Rb, Ba) enrichments and HFSE (Nb, Ta, Zr) depletions, resembling those of typical subduction-related arc volcanic rocks. The Th/La, Th/Ce and Lu/Yb ratios of andesite are below those of the average continental crust, but similar to those of typical mantle-derived magmas. The andesite samples belong to the normal island arc volcanic rocks, which are derived from the water-rich mantle wedge and by partial melting of the fluid-metasomatized mantle wedge (produced by subducting-slab dehydration). LA-ICP-MS zircon U-Pb dating of the andesite yielded Middle Carboniferous age of (322.4±1.1) Ma. Combined with regional geological background and compared with coeval magmatism, we considered that the andesite in the Zhongguai uplift was formed in a continental arc setting, and was the subduction product of residual oceanic basin in West Junggar, which was not completely closed at (322.4±1.1) Ma.

Key words: northwestern margin of Junggar Basin, Zhongguai uplift, Carboniferous, andesite, chronology, geochemistry

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