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现代地质 ›› 2023, Vol. 37 ›› Issue (02): 404-418.DOI: 10.19657/j.geoscience.1000-8527.2022.092

• 岩石学 • 上一篇    下一篇

蒙古—鄂霍次克洋早侏罗世构造演化:来自大兴安岭北段新立屯地区花岗岩的证据

张国宾1(), 孔金贵1, 吴子杰2, 冯玥1, 何云龙1, 陈兴凯1   

  1. 1.辽宁工程技术大学矿业学院,辽宁 阜新 123000
    2.辽宁省地质勘查院有限责任公司,辽宁 大连 116000
  • 收稿日期:2022-02-12 修回日期:2022-08-23 出版日期:2023-04-10 发布日期:2023-05-23
  • 作者简介:张国宾,男,副教授,硕士生导师,1983年出生,矿产普查与勘探专业,主要从事矿床学与矿产勘查方向的科研与教学。Email: zhangguobin85@163.com
  • 基金资助:
    中国地质调查局项目(1212011120342);辽宁省科技厅面上基金项目(20170540428);辽宁省科技厅面上基金项目(201601370);辽宁省教育厅面上基金项目(LJ2019JL027)

Geochronology and Petrogeochemical Characteristics of I-type Granites in Xinlitun Area, Northern Greater Hinggan Mountains and Their Geological Significance

ZHANG Guobin1(), KONG Jingui1, WU Zijie2, FENG Yue1, HE Yunlong1, CHEN Xingkai1   

  1. 1. School of Mines, Liaoning Technical University, Fuxin,Liaoning 123000, China
    2. Liaoning Province Geological Exploration Institute Co., Ltd., Dalian, Liaoning 116000, China
  • Received:2022-02-12 Revised:2022-08-23 Online:2023-04-10 Published:2023-05-23

摘要:

大兴安岭地区显生宙花岗岩极其发育,本文选择大兴安岭北段新立屯地区花岗岩进行了系统的锆石U-Pb同位素年代学和地球化学研究,对比了大兴安岭北段晚中生代花岗岩的地球化学特征,旨在查明其成岩时代和岩石成因,并探讨其构造意义。锆石LA-ICP-MS U-Pb同位素定年结果显示,中细粒二长花岗岩和中细粒花岗闪长岩的成岩年龄分别为(187.2±2.3) Ma和(192.4±1.6) Ma,成岩时代为早侏罗世。岩石地球化学结果显示,新立屯地区早侏罗世花岗岩具有富硅、高碱、富钾、贫镁、低磷、低钛和较低的TFeO/MgO比值等特征,富集轻稀土元素、亏损重稀土元素,富集Rb、Ba、Th、K等大离子亲石元素,亏损Ta、Nb、P、Ti元素,负铕异常不明显,P2O5和Al2O3含量随SiO2的增加而降低,显示出中等分异I型花岗岩的特征。岩石学及地球化学特征表明,其岩浆来源于壳幔混合源区。结合区域构造演化及构造判别,认为研究区早侏罗花岗岩形成于同碰撞火山弧花岗岩构造背景,与蒙古—鄂霍次克洋向南的俯冲作用密切相关。

关键词: 大兴安岭北段, I型花岗岩, 早侏罗世, 锆石U-Pb年龄, 岩石地球化学, 蒙古—鄂霍次克洋

Abstract:

There are voluminous Phanerozoic granites in the Greater Hinggan Mountains. In this paper, zircon U-Pb geochronology and geochemistry of the Xinlitun granites in the northern Greater Hinggan Mountains have been studied. We compared the geochemical characteristics of these Late Mesozoic granites, and discussed their formation age, genesis and geological significance. Zircon LA-ICP-MS U-Pb dating indicates that the medium-fine-grained monzogranite and medium-fine-grained granodiorite were both formed in the Early Jurassic, at (187.2±2.3) Ma and (192.4±1.6) Ma, respectively. Whole-rock geochemical results show that these granites are Si-rich, high in alkalis (K-rich), and contain low Mg, P, Ti, and TFeO/MgO. The rocks are enriched in light rare earth elements and large ion lithophile elements (e.g., Rb, Ba, Th, K), but depleted in heavy rare earth elements and high-field strength elements (e.g., Ta, Nb, P, Ti). No distinct negative Eu anomalies have been identified. The contents of P2O5 and Al2O3 decrease with increasing SiO2. Collectively, we suggested that these granites are moderately differentiated I-type. The petrological and geochemical features indicate that their primary magmas were originated from a mixed crust-mantle source. Considering the regional tectonic background, we suggested that these Early Jurassic granites were formed in a syn-collision volcanic arc setting, closely related to the southward subduction of Mongolia-Okhotsk Ocean.

Key words: northern Greater Hinggan Mountains, I-type granite, Early Jurassic, zircon U-Pb age, petrogeochemistry, Mongolia-Okhotsk Ocean

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