四川冕宁沙坝麻粒岩的岩石地球化学性质及形成时代  

Lithogeochemistry and Lithogenetic Epoch for Shaba Granulite in Mianning,Sichuan

作　　者：刘文中[1] 

机构地区：[1]安徽理工大学资源与环境工程系,安徽淮南232001

出　　处：《四川地质学报》2006年第4期193-198,共6页Acta Geologica Sichuan

基　　金：教育部科学技术研究重点项目(104089);安徽理工大学博士研究基金(2005YB51)资助

摘　　要：沙坝麻粒岩是扬子陆块西缘前寒武系变质杂岩的重要代表。麻粒岩具有Ba、Ce、LREE和Al的富集以及Nb、Ta、Zr、Hf、Ti和HREE亏损的岩石化学性质,结合对麻粒岩的Rb—Sr、Sm—Nd4、0Ar/39Ar和锆石U—Pb测年结果的分析和比较,表明沙坝麻粒岩的原岩形成于新元古代(780Ma)扬子陆块西缘活动大陆边缘的岛弧环境。根据对麻粒岩的变质演化历史和岩石地球化学特征分析,角闪岩相退变质的流体作用对麻粒岩的Rb—Sr、Sm—Nd和40Ar/39Ar同位素计时体系产生了严重干扰,这也是沙坝麻粒岩峰期变质和角闪岩相退变质时代难以确定的重要原因。Shaba granulite is an important component of the Precambrian metamorphic complex on the western margin of the Yangtze landmass. The granulite is characterized by enrichment in Ba, Ce, LREE and Al and depletion in Nb, Ta, Zr, Hf and HREE. Rb - St, Sm - Nd,^40Ar/^39Ar datings for the whole rock and U - Pb dating for zircon indicate that the protolith of the granulite was formed in active continental margin of the Yangtze landmass in Nco - Proterozoic era with an isotope age of 780 Ma. The metamorphic evolution and lithogeochemistry suggest that Rb- Sr, Sm- Nd and ^40Ar/^39Ar isotopic systems for the granulite were disturbed by amphibelite facies retrograte metamorphism which made determination of peak metamorphism and retrograte metamorphism difficult.

关 键 词：麻粒岩 岩石地球化学 新元古代 四川冕宁 

分 类 号：P588.346[天文地球—岩石学]