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现代地质 ›› 2021, Vol. 35 ›› Issue (04): 940-954.DOI: 10.19657/j.geoscience.1000-8527.2020.107

• 岩石学 • 上一篇    下一篇

南阿尔金晚泥盆世构造体制转换:来自索尔库里二长花岗岩年代学和地球化学的制约

袁亚平1(), 刘向东2(), 张振凯2, 曾忠诚2, 何元方2   

  1. 1.陕西省水工环地质调查中心,陕西 西安 710068
    2.陕西省矿产地质调查中心,陕西 西安 710068
  • 收稿日期:2020-04-16 修回日期:2020-12-01 出版日期:2021-08-10 发布日期:2021-09-08
  • 通讯作者: 刘向东
  • 作者简介:刘向东,男,高级工程师,1985年出生,地质工程专业,主要从事区域地质调查及矿产勘查工作。Email: 283859688@qq.com
    袁亚平,女,硕士研究生,1983年出生,地质工程专业,主要从事区域地质调查工作。Email: 282573863@qq.com
  • 基金资助:
    中国地质调查局地质调查项目“新疆阿尔金山阿克达坂南1:5万四幅区域地质调查”(12120113044600);“新疆阿尔金地区1:5万J45E010020等六幅区域地质矿产调查”(12120114081901)

Late Devonian Tectonic Transition in South Altyn Tagh: Constraints from Geochronology and Geochemistry of the Suoerkuli Monzogranite

YUAN Yaping1(), LIU Xiangdong2(), ZHANG Zhenkai2, ZENG Zhongcheng2, HE Yuanfang2   

  1. 1. Shaanxi Hydrogeology Engineering Geology and Environment Geology Survey Center, Xi’an,Shaanxi 710068, China
    2. Shaanxi Mineral Resources and Geological Survey Center, Xi’an,Shaanxi 710068, China
  • Received:2020-04-16 Revised:2020-12-01 Online:2021-08-10 Published:2021-09-08
  • Contact: LIU Xiangdong

摘要:

对阿尔金索尔库里地区二长花岗岩进行了LA-ICP-MS锆石U-Pb定年及全岩主量、微量和稀土元素测试,结果表明二长花岗岩结晶年龄为(377.5±1.6) Ma和(377.4±2.1) Ma;具有高硅(SiO2=72.55%~76.41%)和高碱(K2O+Na2O=7.32%~8.59%)、正常的铝含量(A/CNK=0.92~1.08)、高TFeO/MgO比值(2.57~6.47)的特征,为高钾钙碱性系列;富集轻稀土元素,具有明显Eu负异常;微量元素富集Rb、Th、Y、Zr和Hf等元素,亏损Ba、Sr、P和Ti等元素。上述特征表明索尔库里二长花岗岩为A型花岗岩,是幔源物质底侵作用引发的长英质地壳(变杂砂岩)部分熔融形成的母岩浆经过分离结晶而形成的,且具有A1型花岗岩特征。结合区域地质资料及同期岩浆岩活动历史,认为索尔库里地区二长花岗岩形成于板内伸展构造环境,为晚泥盆世南阿尔金构造带由后造山环境向板内构造体制转换的产物。

关键词: 锆石U-Pb年代学, A型花岗岩, 板内伸展环境, 阿尔金

Abstract:

Whole-rock major, rare earth and trace element compositions, as well as LA-ICP-MS zircon U-Pb ages of monzogranites from Suoerkuli in the Altyn Orogen are newly presented. LA-ICP-MS zircon U-Pb dating indicates that the monzogranites were formed at (377.5±1.6) Ma and (377.4±2.1) Ma. Geochemically, the rocks are characterized by relatively high Si (72.55%-76.41%) and total alkaline (K2O+Na2O=7.32%-8.59%), normal aluminum saturation index (A/CNK=0.92-1.08), and high TFeO/MgO (2.57-6.47), suggesting that the rocks are high-K calc-alkaline. These rocks have relatively high LREEs and remarkable negative Eu anomalies. Furthermore, they are enriched in elements of Rb, Th, Y, Zr, Hf and depleted in Ba, Sr, P, Ti. According to the geochemical characteristics, it is suggested that the monzogranites are classified as A1-type. The monzogranites were likely generated by the fractionation of the parental magma, which was produced by the partial melting of felsic crustal rocks led by mantle-derived material underplating. Based on the regional geological investigations and spatial-temporal distribution of the igneous rocks, we considered that the monzogranite was emplaced in an intraplate extensional environment, and generated in the transition from post-orogenic to intraplate tectonic regime in the Late Devonian.

Key words: zircon U-Pb geochronology, A-type granite, intraplate extension, Altyn Tagh

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