赣中变质岩带变泥砂质岩石地球化学特征及其地质意义  

Geochemical characteristics of meta argillo arenaceous rocks from the metamorphic rock belt in central Jiangxi Province and its geological significance

作　　者：胡恭任[1] 刘丛强[1] 章邦桐[2] 唐红峰[1] 

机构地区：[1]中国科学院地球化学研究所 [2]南京大学内生金属矿床成矿机制研究国家重点实验室,江苏南京210093

出　　处：《地球化学》2004年第2期118-130,共13页Geochimica

基　　金：国家自然科学基金(40272038);科技部攀登计划预选项目(95-预-39);南京大学内生金属矿床成矿机制研究国家重点实验室开放基金;华侨大学博士科研起动资金资助

摘　　要：赣中变质岩带主要由变泥砂质岩石和少量斜长角闪岩组成。30个变泥砂质岩石样品分析表明,稀土元素分布模式显示明显富集轻稀土元素及Eu负异常犤∑REE=129～296μg/g,δEu=0.51～0.86,(La/Yb)N=3.95～12.9犦,其不相容元素比值高(Th/Sc=0.57～3.59、La/Sc=1.46～12.4、La/Yb=5.84～19.0、La/Sm=4.69～6.87、Th/U=3.40～6.42),大离子亲石元素富集,Zr、Hf、Sc、Ti、Y、HREE和Sr含量较低,其原岩应为一套砂泥质岩石,沉积于远离陆地的克拉通大陆架浅海环境;δBa=0.10～0.93,Nd同位素亏损地幔模式年龄tDM=1597～2525Ma,εNd(0)=-9.9～-15.8,其源区物质主体由古元古代富铝富钾的花岗质岩石和(或)碎屑沉积岩构成,经历了较强的化学风化作用。The metamorphic rock belt in central Jiangxi Province, located in the compound terrain among the Huaxia terrain, the Yangtze terrain and the Caledonian fold zone of South China, is composed dominantly of meta argillo arenaceous rocks and small amounts of amphibolites. They underwent amphibolite facies metamorphism. The meta argillo arenaceous rocks show large variations in major element compositions, but have similar REE patterns and trace element compositions, incompatible element and large ion lithophile element enrichments [high Th/Sc (0.57～3.59), La/Sc (1.46～12.4) and La/Yb (5.84～19.0)] and variable Th/U ratios, with ∑REE=129～296 μg/g, δEu=0.51～0.86, (La/Yb)N=3.95～12.9. The rocks have a large variation range of Nd isotopic mode age tDM from 1 597 to 2 525 Ma and low εNd(0) from -9.9 to -15.8. The metamorphic rocks belt in central Jiangxi Province was likely formed in a tectonic environment of the passive continental margin of the Huaxia massif. The source region, from which the argillo arenaceous rocks were derived, was composed dominantly of upper crustal sources (Al and K rich granitic or/and sedimentary rocks of Early Proterozoic) and experienced good sorting, slow deposition and more intense chemical weathering. According to the whole rock Sm Nd isochron ages [(1 113±49)～(1 199±26) Ma] of plagioclase amphibole (schist) and Nd isotopic mode age tDM (1 597～2 525 Ma) of meta argillo arenaceous rocks, the metamorphic rocks belt was formed in Midproterozoic between 1 100～1 600 Ma.

关 键 词：变泥砂质岩石 地球化学 ND同位素 变质岩带 江西 

分 类 号：P588.3[天文地球—岩石学] P594[天文地球—地质学]