东昆仑德龙花岗岩成因及对古特提斯洋演化的制约  

Genesis of Delong Granite in East Kunlun Orogen and Its Implication on the Evolution of Paleo-Tethys Ocean

作　　者：陈加杰 冷成彪 付乐兵[3] 赵旭 邢浩 Chen Jiajie;Leng Chengbiao;Fu Lebing;Zhao Xu;Xing Hao(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,China;Faculty of Earth Resources,China University of Geosciences,Wuhan 430074,China;Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,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,江西南昌330013 [2]东华理工大学地球科学学院,江西南昌330013 [3]中国地质大学资源学院,湖北武汉430074 [4]中国科学院广州地球化学研究所,广东广州510640

出　　处：《地球科学》2024年第2期560-576,共17页Earth Science

基　　金：东华理工大学博士科研启动基金项目(No.DHBK2018009)。

摘　　要：东昆仑造山带为古特提斯域重要组成部分,该区古特提斯洋的闭合时间和古特提斯演化相关岩浆岩广泛存在的NdHf解耦原因仍然不清.选取该造山带德龙花岗岩开展锆石年代学和全岩元素-同位素地球化学研究.结果表明德龙花岗岩侵位于中三叠世;岩体属准铝质-弱过铝质高硅I型花岗岩,岩石总体Sr/Y和La/Yb比值较低,与正常岛弧岩浆岩类似;岩体具有富集的Sr-Nd和富集至亏损的锆石Hf同位素特征.综合岩相学、同位素-元素特征表明德龙花岗岩来源于新老地壳混合熔融或者富集地幔和板片(玄武质洋壳和沉积物的混合物)等混合源区来源岩石的重熔作用,这些混合过程导致德龙及同时代中酸性岩浆岩出现Nd-Hf解耦.综合区域地质地球化学特征表明古特提斯洋在240 Ma左右闭合.The East Kunlun Orogen is an important part of the Paleo-Tethys domain.The closure time of the Paleo-Tethys Ocean and the reason for decoupling Nd-Hf isotopes of Permian-Triassic magmatic rocks are still controversial.Zircon chronology and whole rock elemental and isotopic analyses have been carried out on the Delong granite in the East Kunlun Orogen.The results show that the Delong granite was emplaced in the Middle Triassic and belong to metaluminous to weakly peraluminous high silica I-type granite,with low Sr/Y and La/Yb ratios,similar to normal island arc magmatic rocks.Isotopic data show enriched Sr-Nd and enriched to depleted zircon Hf isotopic signatures for the Delong granite.These data,together with petrography,indicate that the Delong granite comes from the mixed melting of new and old crust or the remelting of rocks from mixed source areas such as enriched mantle and oceanic plate(mixture of basalt crust and sediments).These special sources contribute to widespread decoupling of ε_(Nd)(t)and ε_(Hf)(t)of the Delong granite and even regional contemporaneous intermediate-acid magmatic rocks.Based on the above conclusions and the geological and geochemical characteristics of the rocks regionally,it is inferred that the Paleo-Tethys Ocean was closed at about 240 Ma.

关 键 词：花岗岩 地壳重熔 Nd-Hf解耦 古特提斯洋 洋陆转换 东昆仑造山带 地球化学 

分 类 号：P581[天文地球—岩石学]