北秦岭东段官坡地区花岗伟晶岩锆石U-Pb年代学、岩石成因及其构造背景
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1.南阳理工学院;2.中国地质调查局发展研究中心;3.长安大学西部矿产资源与地质工程教育部重点实验室;4.河南省地质矿产勘查开发局第二地质矿产调查院;5.河南省地质研究院

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本文为国家自然科学基金项目(42172236、41872233、41872235)、中国地质调查局项目(DD20190570,DD20230053,DD20230355)、自然资源部成矿作用与资源评价重点实验室开放基金项目(ZS006)、河南省战略性金属矿产成矿规律与找矿预测研究项目(2023-903-XM006)和南阳理工学院交叉科学研究项目资助的成果.


Zircon U-Pb geochronology, petrogenesis and tectonic setting of granitic pegmatite in Guanpo area, the eastern part of the North Qinling Orogenic Belt
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1.Nanyang Institute of Technology;2.Development and Research Centre;3.Key Laboratory of Western China’s Mineral Resources and Geological Engineering, Ministry of Education;4.Key Laboratory of Western China’s Mineral Resources and Geological Engineering,Ministry of Education,Xi’an;5.NO.2 Institute of Geological and Mineral Resources Survey of Henan;6.Henan Academy of Geology

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    摘要:

    北秦岭构造带花岗伟晶岩是我国重要的伟晶岩矿区,花岗伟晶岩的形成时间和岩石成因存在一定争议。本文通过对北秦岭东段官坡地区峡河村花岗伟晶岩和上河村花岗伟晶岩开展岩石学、锆石U-Pb年代学、锆石Hf同位素地球化学及全岩主微量元素地球化学研究,限定北秦岭东段花岗伟晶岩的形成时代,揭示花岗伟晶岩的岩浆来源和岩石成因。LA-ICP-MS锆石U-Pb同位素定年结果显示峡河村花岗伟晶岩和上河村花岗伟晶岩的结晶年龄分别为360~361 Ma和334.8 Ma。峡河村花岗伟晶岩和上河村花岗伟晶岩含有石榴石、白云母和电气石,富集SiO2、Na2O和K2O,CaO、FeOt和MgO含量较低,主体呈过铝质。峡河村花岗伟晶岩和上河村花岗伟晶岩轻重稀土元素分异不明显,具较明显的Eu正异常;微量元素富集Rb、Th、Ba、Cs等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE),具有低的Nb/Ta和Zr/Hf比值,指示岩浆经历了高度结晶分异作用。峡河村花岗伟晶岩具有较低的εHf(t)值,为-11.7~-6.2;上河村花岗伟晶岩εHf(t)值明显高于峡河村花岗伟晶岩,为-4.9~1.1。以上结果显示,峡河村花岗伟晶岩为古老地壳部分熔融产物,上河村花岗伟晶岩为新生地壳部分熔融的岩浆在上侵过程中同化混染围岩的结果。北秦岭东段花岗伟晶岩初步可分为北部稀有金属花岗伟晶岩和南部铀花岗伟晶岩。

    Abstract:

    The granitic pegmatites of the North Qinling tectonic belt are important pegmatite areas in China. There are controversial about the formation age and petrogenesis of the granite pegmatite. This paper presents LA-ICP-MS zircon U-Pb age, Hf isotopic and geochemical data of the Xiahecun granitic pegmatites and the Shanghecun granitic pegmatites in the Guanpo area to determine the formation age, the magma source, the petrogenesis and tectonic setting. LA-ICP-MS zircon U-Pb dating suggests that the Xiahecun granitic pegmatites and the Shanghecun granitic pegmatites crystallized 360~361 Ma and 334.8 Ma, respectively. The Xiahecun granitic pegmatites and the Shanghecun granitic pegmatites contain garnet, muscovite and tourmaline, with high contents of SiO2, Na2O and K2O, and low contents of CaO, FeOt and MgO, and are mainly peraluminous. The Xiahecun granitic pegmatites and the Shanghecun granitic pegmatites show little fractionation between LREE and HREE, and have obvious positive Eu anomalies. The magma is enriched in large ion lithophile elements (LILE) such as Rb, Th, Ba and Cs, and depleted in high field strength elements (HFSE) such as Nb, Ta and Ti, with low Nb/Ta and Zr/Hf ratios, indicating a high degree of crystallization differentiation. The Xiahecun granitic pegmatite has low εHf values ranging from -11.7 to-6.2. Shanghecun granitic pegmatite εHf values rangs from -4.9 to 1.1, higher than that of Xiahecun granitic pegmatite. Based on this, the Xiahecun granitic pegmatite is the result of partial melting of the ancient crust, while the Shanghecun granitic pegmatite is the result of partial melting of the juvenile lower crust, and then magma assimilates and contaminate the wall rocks. The granitic pegmatite in the eastern part of North Qinling can be divided into northern rare metal granitic pegmatite and southern uranium granitic pegmatite.

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  • 收稿日期:2023-05-12
  • 最后修改日期:2023-10-07
  • 录用日期:2023-11-02
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