| 冈底斯东段加查县丝波绒曲早侏罗- 始新世复式岩体成因及其对构造演化的启示 |
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| 引用本文： | 李艳芳,邱检生,王睿强,徐航,洪宇飞.冈底斯东段加查县丝波绒曲早侏罗- 始新世复式岩体成因及其对构造演化的启示[J].地质学报,2019,93(12):3020-3046. |
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| 作者姓名： | 李艳芳 邱检生 王睿强 徐航 洪宇飞 |
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| 作者单位： | 南京大学地球科学与工程学院, 内生金属矿床成矿机制研究国家重点实验室，南京，210023,南京大学地球科学与工程学院, 内生金属矿床成矿机制研究国家重点实验室，南京，210023,南京大学地球科学与工程学院, 内生金属矿床成矿机制研究国家重点实验室，南京，210023,南京大学地球科学与工程学院, 内生金属矿床成矿机制研究国家重点实验室，南京，210023,南京大学地球科学与工程学院, 内生金属矿床成矿机制研究国家重点实验室，南京，210023 |
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| 基金项目： | 本文为国家自然科学基金项目（编号41572041）资助成果。 |
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| 摘 要： | 本文选取冈底斯带东段加查县东北部丝波绒曲复式岩体为对象,对其进行了岩相学、地质年代学、岩石地球化学以及Sr-Nd-Hf同位素组成的综合研究,据此探讨了该复式岩体的成因及其对构造演化的启示。研究结果表明,该复式岩体由早侏罗世辉长岩-花岗岩杂岩(188～185Ma)和始新世花岗质岩石(～47Ma)构成,两期花岗质岩石中普遍发育塑变形态的镁铁质包体。早侏罗世杂岩由角闪辉长岩和英云闪长岩组成,角闪辉长岩中的主要铁镁矿物为角闪石,它们为一套钙碱性弧岩浆岩组合,具有亏损的Sr-Nd-Hf同位素组成。始新世花岗质岩石主要为二长花岗岩-花岗闪长岩,它们较早侏罗世英云闪长岩更为富碱,属钙碱性-高钾钙碱性I型花岗岩,其同位素组成也较早侏罗世英云闪长岩富集。综合分析表明,该区早侏罗世复合辉长岩-花岗岩的形成受控于新特提斯洋板片北向俯冲的构造背景,角闪辉长岩起源于受俯冲板片脱水交代的上覆地幔楔的部分熔融,共生的英云闪长岩则为同期幔源岩浆底侵诱发初生地壳部分熔融产生的长英质岩浆与幔源岩浆不同程度混合的产物。始新世花岗岩的形成受控于新特提斯洋板片断离的构造背景,是由具"弧"型地球化学特征的初生地壳再造的产物,并有少量印度陆壳富集组分参与成岩。
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| 关 键 词： | 复式岩体 早侏罗世- 始新世 岩石成因 构造意义 加查丝波绒曲 |
| 收稿时间： | 2019/9/10 0:00:00 |
| 修稿时间： | 2019/10/7 0:00:00 |
Petrogenesis of the Early Jurassic- Eocene composite pluton in Siborongqu,Gyaca County, eastern segment of the Gangdese belt, and its tectonic implications |
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| LI Yanfang,QIU Jiansheng,WANG Ruiqiang,XU Hang and HONG Yufei.Petrogenesis of the Early Jurassic- Eocene composite pluton in Siborongqu,Gyaca County, eastern segment of the Gangdese belt, and its tectonic implications[J].Acta Geologica Sinica,2019,93(12):3020-3046. |
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| Authors: | LI Yanfang QIU Jiansheng WANG Ruiqiang XU Hang and HONG Yufei |
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| Institution: | State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023,State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023,State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023,State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023 and State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing, 210023 |
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| Abstract: | In this paper, we report petrography, geochronology, lithogeochemistry and Sr- Nd- Hf isotopic data for the Early Jurassic- Eocene composite pluton in Siborongqu, Gyaca County, the eastern segment of the Gangdese belt, aiming to understand the petrogenesis and its tectonic implications. The investigation results indicate that the Siborongqu composite pluton is composed of Early Jurassic gabbro- granite complex (188~185Ma) and Eocene granitoids (~47Ma). Mafic microgranular enclaves (MMEs) with various plastic shapes are generally dispersed in both stages of granitoids. The Early Jurassic complex consists predominantly of hornblende gabbros and tonalites, with mafic minerals in the gabbroic rocks are mainly of amphiboles. They can geochemically be grouped into a set of calc- alkaline magmatic rocks with arc signatures, and show depleted Sr- Nd- Hf isotopic compositions. The Eocene granitoids constitute dominantly of monzogranites and granodiorites. They are more alkaline and show somewhat enriched Sr- Nd- Hf isotopic compositions with respect to the Early Jurassic tonalites, and can be grouped into calc- alkaline or high- K calc- alkaline I- type granites. Combined with our data and previous studies, we concluded that the Early Jurassic gabbroic rocks were generated by partial melting of the overlying depleted mantle wedge which was metasomatized by aqueous fluids released from the subducted slab. The coexisting tonalites were produced by mixing of felsic magmas derived from partial melting of juvenile lower crust and mafic magmas related to the gabbroic rocks. The Eocene granitoids were derived from partial melting of juvenile lower crust triggered by underplating of a contemporaneous mafic magma, and with somewhat involvement of enriched components from the subducted Indian continental crust. From the perspective of tectonic evolution, the petrogenesis of Early Jurassic complex is controlled by the northward subduction of the Neo- Tethyan oceanic slab, while the Eocene granitoids correspond to the upwelling of asthenosphere after break- off of the Neo- Tethyan oceanic slab. |
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| Keywords: | composite pluton Early Jurassic- Eocene petrogenesis tectonic significances Siborongqu Gyaca County |
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