今天是2019年02月21日

茫崖二长花岗岩锆石U-Pb 年代学、Lu-Hf 同位素特征及岩石成因

DOI:10.3799/dqkx.2018.326

作者:徐 楠,吴才来,雷 敏,张 昕,陈红杰,郭文峰,郑 坤,高 栋,刘俊壮

联系地址:大陆构造与动力学国家重点实验室,中国地质科学院地质研究所,北京100037

摘要:阿克腾龙山二长花岗岩位于南阿尔金茫崖地区北侧,讨论其成因类型、成岩年代以及构造环境,进而探讨南阿尔金造山带早古生代岩浆活动及壳幔相互关系.利用岩石地球化学、LA-ICP-MS锆石U-Pb年代学和Lu-Hf同位素分析研究了岩体的成因类型、成岩时代、物质来源和成岩环境.研究表明,该岩体属于弱过铝质、高钾钙碱性I型花岗岩.富集轻稀土元素,而相对亏损重稀土元素;岩浆演化过程中可能发生了以角闪石、磷灰石和金红石为主的分离结晶.岩体的成岩年龄为435~449 Ma.锆石的εHf(t)正、负值各半,说明岩体可能来源于古老地壳和新生地壳的混合物质,可能是新生地壳部分熔融并混合部分古老地壳物质形成,或者是新生地壳和古老地壳的混合物质部分熔融,经历分离结晶而成.成岩环境可能是俯冲洋壳板片断离后,由碰撞挤压转向伸展抬升的构造环境.

关键字:南阿尔金南缘;二长花岗岩;LA-ICP-MS;I型花岗岩;分离结晶;岩石学.

Petrogenesis, Zircon U-Pb Chronology, and Lu-Hf Isotopic Characteristics ofMonzonitic Granite from Mangya Area

Author:Xu Nan, Wu Cailai, Lei Min, Zhang Xin, ChenHongjie, GuoWenfeng, Zheng Kun, Gao Dong, Liu Junzhuan

Author Address:State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China

Abstract:Aketenglongshan monzonitic granite is located in the south margin of South Altun. Here we present whole-rock geochemistry, zircon U-Pb geochronology and Hf isotope analysis to study the petrogenesis and magmatic evolution of the granite, which belong to high-K calc-alkalin, weakly peraluminous series and I-type granite. The geochemical characteristics showing strongly fractionation of the REEs, and enrichment in LREE, while depletion in HREE. We infer that amphibole, apatite and rutile fractionation occurred during the magmatic evolution. The zircon U-Pb age of the granite is 435~449 Ma, representing the crystallization age of the granite. The half negative and half positive value of zircon εHf(t) indicates that the origin of the monzonitic granite is mixture of juvenile and ancient crust materials, and the granites were derived from the partially melted juvenile crust, and mixed with ancient crust materials during the upwelling, or derived from the partially melted mixture of juvenile and ancient crust materials, in extensional environment transformed from compressional environment after the break off of the subducted oceanic crust.

Keyword:south margin of South Altun; monzonitic granite; LA-ICP-MS; I-type granite; fractionation; petrology.

 

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作者简介:徐楠(1984-),男,博士后,主要从事花岗岩与成矿方面的研究工作.ORCID:0000-0002-2665-856X .E-mail:397545121@qq.com .

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