南岭地区油山岩体和坪田岩体形成年龄及其地质意义  

Geochronology of Youshan and Pingtian Granites in Nanling Range and Its Geological Implication

作　　者：孙立强[1,2] 凌洪飞[1,2] 沈渭洲[1,2] 黄国龙 谭正中 

机构地区：[1]内生金属矿床成矿机制研究国家重点实验室 [2]南京大学地球科学与工程学院,南京210093 [3]核工业290研究所,韶关512026

出　　处：《高校地质学报》2010年第2期186-197,共12页Geological Journal of China Universities

基　　金：核工业地质局十一五基础科研项目;内生金属矿床成矿机制研究国家重点实验室研究项目(2008-I-04);教育部科学研究重大项目(306007)资助

摘　　要：南岭地区的油山岩体和坪田岩体位于诸广山复式岩体东侧,以前的研究认为它们都属于燕山期花岗岩。对油山岩体和坪田岩体进行的LA-ICP-MS锆石U-Pb年代学研究结果表明,油山岩体的成岩年龄为(213.4±3.0)Ma,坪田岩体(西北部)的成岩年龄为(238.8±2.2)Ma,因此油山岩体应属于印支期岩体,而坪田岩体可能是一个印支-燕山早期复式岩体,而非前人所划定的燕山期岩体。此外,两个岩体内含有太古代和541Ma～1642Ma的继承锆石,暗示物源区曾存在太古代和元古代地壳,经历过多期次的岩浆作用。部分油山岩体锆石在CL图像上表现出具有暗色边部的特征,这些暗色边可能与后期热液作用影响有关,其时代为燕山期,表明油山岩体在燕山期受到了流体作用的影响,坪田岩体锆石也存在较窄的暗色边,也是受后期热液作用影响所造成。In previous studies,the Youshan granite and Pingtian granite located to the east of the Zhuguangshan composite granite body in Nanling Range were considered being formed in the Yanshanian period.In this study,we present LA-ICP-MS U-Pb zircon dating results which shows that the ages of the Youshan granite and the northwestern part of the Pingtian granite are（213.4±3.0）Ma and（238.8±2.2）Ma,respectively.These results indicate that the Youshan granite was formed by the Indosinian magmatism and the Pingtian granite is probably a composite granite batholith formed in the Indosinian and Yanshanian periods.In addition,it is revealed that both granites contain zircons having inherited cores with ages of Archean and 541 Ma^1 642 Ma,implying existence of Archean crust as well as Proterozoic crust containing rocks formed by several periods of magmatism in the source.Some of the zircons from the Youshan granite display dark rims（in CL images）with Yanshanian ages,which suggests that the granite was probably affected by hydrothermal fluids during the Yanshanian period.Narrow dark rims of zircons are also observed in the Pingtian granite,suggesting effect of hydrothermal fluids.

关 键 词：LA-ICP-MS锆石U-PB年龄 油山和坪田岩体 南岭 印支期 

分 类 号：P597[天文地球—地球化学] P588[天文地球—地质学]