扬子板块西缘黑么花岗质岩体的成因与构造意义:来自锆石U-Pb年代学和岩石地球化学的约束  

Petrogenesis and Tectonic Significances of the Heimo Granitic Pluton in the Western Margin of Yangtze Plate:Constraints from SIMS Zircon U-Pb Geochronology and Petrogeochemistry

作　　者：张玉顺 吴玉[2] 潘家永[1] 王凤岗[2] 姚建 韩文文 钟福军 ZHANG Yu-shun;WU Yu;PAN Jia-yong;WANG Feng-gang;YAO Jian;HAN Wen-wen;ZHONG Fu-jun(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;Beijing Research Institute of Uranium Geology,CNNC,Beijing 100029,China;No.280 Institute of Nuclear Industry,Guanghan Sichuan 618300,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,南昌330013 [2]核工业北京地质研究院,北京100029 [3]核工业二八○研究所,四川广汉618300

出　　处：《矿物岩石地球化学通报》2020年第5期983-998,共16页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金资助项目(41802218,41772066);中国核工业地质局铀矿地质科研项目(201807-3,201922-2);东华理工大学核资源与环境国家重点实验室项目(Z1906,NRE1905)。

摘　　要：黑么岩体是在扬子板块西缘的攀枝花地区发现的新元古代花岗岩体,它主要由肉红色和灰白色似斑状花岗岩组成。为探讨扬子板块西缘构造环境和动力学背景,对其开展了锆石U-Pb年代学和岩石地球化学研究。锆石U-Pb定年结果表明,肉红色和灰白色似斑状花岗岩分别形成于(822.21±22)Ma(MSWD=3.5)和(822.1±4.4)Ma(MSWD=0.83),属新元古代。二者均具有弱过铝质-过铝质高钾钙碱性花岗岩的特征,属铝质A型花岗岩。地球化学分析表明,岩浆源自高温低压下英云闪长质-花岗闪长质地壳物质的部分熔融,并有少量幔源物质或新生地壳物质的混入。在构造环境判别图解中,所有样品均落在A2型花岗岩和板块碰撞/陆缘弧的区域内。结合区域地质资料和前人研究成果,推测黑么岩体可能形成于活动大陆边缘由俯冲体制引起的弧后伸展环境。The Neoproterozoic Heimo granitic pluton,mainly composed of pink porphyritic granite and gray porphyritic granite,is located in the Panzhihua area in the western margin of Yangtze Plate.In order to discuss the tectonic setting and geodynamic background of the western Yangtze plate during the Neoproterozoic period,the zircon U-Pb chronological and whole-rock geochemical studied of the Heimo granitic pluton have been carried out in this paper.SIMS zircon U-Pb dating results show that the pink and gray porphyritic granites were emplaced in Proterozoic with zircon U-Pb ages of(822.21±22)Ma(MSWD=3.5)and(822.1±4.4)Ma(MSWD=0.83),respectively.Both pink and gray porphyritic granites are characterized with metaluminous to strongly peraluminous high-K calc-alkaline granites,and belong to the aluminum A-type granite.Geochemical results indicate that the Heimo granitic pluton was derived from the partial melting of tonalitic or granodioritic materials of the crust under high temperature and low pressure condition with the input of minor mantle-and/or juvenile crust-derived materials.Result of all samples of the Heimo granitic pluton are respectively plotted into fields of the A2-type granite and the collisional and/or continental arc settings in tectonic discrimination diagrams.Combining with data of regional geology and previous studies for the western Yangtze plate,we have proposed that the Heimo granitic pluton was most likely formed in a back-arc extensional environment resulted from the subduction system in the active continental margin during the Neoproterozoic.

关 键 词：A型花岗岩 弧后伸展环境 黑么岩体 新元古代 扬子板块西缘 

分 类 号：P588.121[天文地球—岩石学]