四川会理拉拉铜矿辉长岩群地球化学与Sm-Nd同位素定年  

Geochemistry and Sm-Nd Dating of the Gabbro in the Lala Copper Ore District,Sichuan Province,China

作　　者：周家云[1,2] 郑荣才[2] 朱志敏[1,2] 陈家彪[1] 沈冰[1] 李潇雨[1] 罗丽萍[1] 

机构地区：[1]中国地质科学院矿产综合利用研究所,成都610041 [2]成都理工大学油气藏地质及开发工程国家重点实验室,成都610059

出　　处：《矿物岩石地球化学通报》2009年第2期111-122,共12页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：科技部国际科技合作项目(2005DFA20063)

摘　　要：四川会理拉拉铜矿床辉长岩群与矿床在时空分布上紧密相关,表明辉长岩群岩石成因与构造背景对重新认识矿床成因有重要意义。本文分析了辉长岩群的主量元素、微量元素、稀土元素和Sm-Nd同位素,探讨了辉长岩的成因。结果表明,拉拉地区辉长岩群形成于850 Ma板内裂谷环境,为碱性玄武岩,具有较平坦的REE分布型式和“驼峰”状微量元素原始地幔标准化分配型式,较低的原始地幔标准化Th/Nb值,以及较高的εNd（t）值（0.8~4.1）,HFSE比值成分点均落入洋岛玄武岩（OIB）范围,与本区同期地幔柱成因的大陆玄武岩特征相似,说明辉长岩的形成可能是扬子地台西缘Rodinia超大陆裂解的岩浆事件,与矿床之间很可能有紧密的热动力学联系。The spatial and temporal distributions of copper deposit and gabbros in the Lala copper deposit area （Hui- li, Sichuan） are closely related indicates the petrogenesis and tectonic setting of the gabbros are of great significance in understanding the genesis of the deposit. This study analyzed the contents of major elements, trace elements and rare earth elements as well as Sm-Nd isotopic constitute of the gabbros and investigated the genesis of the gabbros. The results showed that the gabbros is alkaline basalt and was formed in the Rift Valley about 850Ma ago, the gabbros has a relatively flat REE distribution pattern, a ＂hump＂ shape primitive mantle-normalized pattern of trace elements, a low primitive mantle-normalized ratio of Th/Nb and a high εNd（t） ratio （0.8--4. 1）, in terms of discriminating evaluation system of the high field strength elements （HFSE）, the values of all gabbros samples fall into the range of oceanic island basalt （OIB）, and are similar with those of continental basalt, which were formed by mantle plume of the same period. It may suggest that the gabbros were formed by Neoproterozoic magmatic event in the western margin of the Yangtze craton, and that there may have closely thermodynamical connections between the gabbros and the deposit.

关 键 词：拉拉铜矿 辉长岩 岩石成因 地球化学 SM-ND同位素 

分 类 号：P597.3[天文地球—地球化学]