江西南城震旦系周潭群变质岩地球化学特征

GEOCHEMICAL CHARACTERISTICS OF METAMORPHIC ROCKS OF ZHOUTAN GROUP IN NANCHENG AREA,JIANGXI PROVINCE

周潭群变质岩其主要岩石类型的ＳｉＯ２含量为５８％～７３％，Ｋ２Ｏ＋Ｎａ２Ｏ大多为４％～６％。稀土配分型式均为右倾负斜率轻稀土富集型，全部样品出现负Ｅｕ异常。岩石中Ｓｎ、Ｓｂ、Ｓ、Ｃｏ、Ｎｉ、Ｈｇ、Ｍｏ含量低于克拉克值，而Ｌｉ、Ｒｂ、Ｃｓ等碱性元素含量偏高，特别是微量元素组合Ａｎ、Ａｇ、Ａｓ、Ｐｈ、Ｚｎ含量明显高于克拉克值。周潭群变质岩形成年龄为６７２±７２Ｍａ，相当于震旦系底部层位，变质相应属低角门岩相，其原岩体系应为一套复理石或类复理石泥砂岩建造。

he metamorphic rocks of Zhoutan Group belong to low-middle level metamorphic Gradethe contents of SiO2 of most samples are 58%-73%,K2O+Na2O4%-6%.The Distributiobn pattrerns of Ree indicate that LREE are rich in the rocks, and the contents of Eu in most samples have a deficit,The contents of trace elements sunch as Sn,Sb,S,Co,Ni,Hg,Mo are lower than that of the cruist,but Li,Rb,Cs and especially the group of Au,Ag,As,Pb,Zn are much higher than that of the crust The primary rock of metamor Formation The analysis results of Rb and Sr isotopes indicate that the methamorphic rocks Of Zhoutan Group formed for about 672±72 Ma which was near to the lower part of the Sinian period,Finally,the authors consider that the metamorphic rocks of Zhoutan Group Belong to low amphibolite facies.