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现代地质 ›› 2023, Vol. 37 ›› Issue (06): 1597-1608.DOI: 10.19657/j.geoscience.1000-8527.2023.050

• 岩石学与岩石地球化学 • 上一篇    下一篇

小兴安岭翠峦地区早侏罗世A型花岗岩成因与动力学背景

杨元江1(), 邓昌州2, 李成禄1, 杨文鹏1, 符安宗1, 郑博1, 袁茂文3, 张立东1   

  1. 1.黑龙江省自然资源调查院,黑龙江 哈尔滨 150036
    2.中国科学院地球化学研究所,贵州 贵阳 550081
    3.中国地质大学(北京)地球科学与资源学院,北京 100083
  • 收稿日期:2022-09-14 修回日期:2023-04-17 出版日期:2023-12-10 发布日期:2024-01-24
  • 作者简介:杨元江,男,高级工程师,1982年出生,地质学专业,主要从事地质矿产勘查及研究工作。Email:geolj@qq.com
  • 基金资助:
    黑龙江省地质矿产局科研项目(HKY202301);黑龙江省国土资源公益项目(GY-2018003)

Genesis and Tectonic Significance of Early Jurassic Cuiluan A-type Granite in the Lesser Hinggan Mountains

YANG Yuanjiang1(), DENG Changzhou2, LI Chenglu1, YANG Wenpeng1, FU Anzong1, ZHENG Bo1, YUAN Maowen3, ZHANG Lidong1   

  1. 1. Heilongjiang Institute of Natural Resources Survey, Harbin, Heilongjiang 150036, China
    2. Institute of Geochemistry Chinese Academy of Sciences, Guiyang, Guizhou 550081, China
    3. School of Earth and Resources, China University of Geoscience (Beijing), Beijing 100083, China
  • Received:2022-09-14 Revised:2023-04-17 Online:2023-12-10 Published:2024-01-24

摘要:

小兴安岭伊春翠峦地区地处洋陆转换关键位置,受古亚洲洋和太平洋构造域的双重影响,是研究区域构造演化的重要部位。该区域中生代花岗岩形成构造环境与动力学机制长期存在分歧,一定程度上制约了区域构造演化历史的反演,也影响区域找矿工作的部署。本文对伊春翠峦地区碱长花岗岩进行全岩元素组成以及锆石U-Pb年代学与Hf同位素组成分析,阐释岩石成因和源区属性,并探讨成岩构造环境。结果显示,岩浆锆石206Pb/238U加权平均年龄为(189.1 ± 1.6) Ma (MSWD=2.1,n=20),指示岩体侵位于早侏罗世。岩石富Si、K和Na元素,贫Ca、Mg元素;富集Th、Zr、Hf、Ce和Y元素,亏损Ba、Sr、Eu和Ti元素;锆石饱和温度高(804~ 810 ℃),显示岩石属于A型花岗岩。岩石稀土元素总量高(∑REE=192.60×10-6~232.80×10-6),Nb、Ta和Ti等元素亏损,Th元素富集,指示其具壳源特征。锆石的εHf(t)=1.46~2.27,对应的地壳模式年龄$T_{\mathrm{DM}}{ }^{\mathrm{C}}$=1133~1088 Ma,表明岩浆源区物质主要为中元古代新生下地壳。综合分析认为,伊春地区早侏罗世岩浆活动与太平洋板块俯冲及伸展作用密切相关。本研究成果为深入理解小兴安岭地区早侏罗世构造演化提供了新的年代学与岩石学约束。

关键词: 小兴安岭, A型花岗岩, Hf同位素, 岩石地球化学, 构造意义

Abstract:

The Cuiluan area (Yichun) in the Lesser Hinggan Mountains is located at a critical location for land-sea transition, and is also affected by both the Paleo-Asian Ocean and Pacific tectonic domains.Hence, it has become an important part of the study of regional tectonic evolution.There are different viewpoints on the tectonic setting and geodynamic mechanism for the regional Mesozoic granite emplacement.This constrains the reconstruction of regional tectonic evolution, and hinder the advance of regional prospecting.Basing on the study in geochronology, lithogeochemistry and Hf isotope of the Early Jurassic Cuiluan alkali feldspar granite, we discussed the granitic genesis and its geological significance, which provides a new chronological constraint for better understanding the Early Jurassic regional tectonic evolution.Zircon U-Pb dating results show that the intrusive age of alkali feldspar granite is (189.1± 1.6) Ma (Early Jurassic).The granitic rock is rich in Si, K, and Na and poor in Ca and Mg.It is enriched in Th, Zr, Hf, Ce and Y, but depleted in Ba, Sr, Eu, Nb, Ta and Ti.The zircon saturation temperature is high (804-810 ℃).The total REE content is high (ΣREE=192.60×10-6-232.80×10-6).These characteristics show that the granite is A-type, with crustal source affinity. The zircon εHf(t) ranges from +1.46 to + 2.27, with the corresponding crustal model age $T_{\mathrm{DM}}{ }^{\mathrm{C}}$=1133-1088 Ma, indicating that the magma source consists mainly of the juvenile Mesoproterozoic crustal material.On the basis of previous works, we consider that the Early Jurassic magmatic activity at Yichun was closely related to the Paleo-Pacific subduction and attendant tectonic extension of the supra-subduction plate.

Key words: Lesser Hinggan Mountains, A-type granite, Hf isotope, lithogeochemistry, tectonic significance

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