晋陕交界涑水杂岩LA-ICP-MS锆石U-Pb年龄和Hf同位素组成及其地质意义  

LA-ICP-MS zircon U-Pb dating and Hf isotopic compositions of rocks from the Sushui complex in Shanxi-Shaanxi border area and their geological significance

作　　者：王建其[1] 刘祥[1] 第五春荣[1] 

机构地区：[1]大陆动力学国家重点实验室,西北大学地质学系,陕西西安710069

出　　处：《地质通报》2017年第2期392-401,共10页Geological Bulletin of China

基　　金：国家自然科学基金项目<国家创新研究群体:大陆构造与动力学>(批准号:41421002);<华北克拉通南缘早前寒武纪构造-热事件及其地质意义>(批准号:41672188);<华北克拉通南缘豫陕地区古元古代构造-热事件研究>(批准号:41272004)

摘　　要：涑水杂岩作为华北克拉通南部早前寒武纪变质基底杂岩的重要组成部分,以中条山地区出露最好且研究程度最高。在晋陕交界处的韩城和河津地区也有零星的古老变质基底杂岩出露,通常认为是中条山地区涑水杂岩的西延。用LA-ICP-MS锆石U-Pb方法测得研究区内的基底岩石角闪斜长片麻岩、透辉斜长片麻岩和二长花岗片麻岩原岩的形成年龄分别为2260±28Ma、2053±34Ma和2098±27Ma,表明晋陕交界处涑水杂岩的形成年龄明显小于中条山地区的涑水杂岩,其形成时代主要应为古元古代早期,而非太古宙。锆石Hf同位素显示,所分析的锆石多数具有低ε_(Hf)(t)值,最低可达-6,其二阶段模式年龄为2630~2933Ma,表明这些形成于古元古代的岩石为太古宙岩石再循环的产物,暗示在晋陕交界处可能存在太古宙的古老地壳物质,同时也支持华北克拉通南部太古宙地块划分的推论。The Sushui complex is one of the main component parts of basement rocks in southern North China Craton(NCC). It is typically exposed in Zhongtiaoshan area and has been studied in detail. The Early Precambrian metamorphic basement complex rocks sporadically exposed in Shanxi-Shaanxi border area are traditionally regarded as the western extension and equivalents of Sushui complex in Zhongtiao region. LA-ICP-MS zircon U-Pb dating reveals that the protolithic ages of amphibolite-plagioclase gneiss, diopside-plagioclase gneiss and two-feldspar granite gneiss are 2260±28Ma, 2053±34Ma and 2098±27Ma, respectively, significantly younger than the ages of rocks in Zhongtiaoshan area, suggesting that the Sushui complex was likely formed in Early Paleoproterozoic rather than in Archean. The majority of zircons of the samples have negative ε_(Hf)(t) values(the lowerest being-6) with two-stage crustal model ages of 2630~2933Ma, which suggests that these samples were derived from recycled Mesoarchean to Neoarchean crust,and continental crustal materials as old as 2630~2933Ma probably preexisted in the Shanxi-Shaanxi border area. These results provide further evidence for the inference that the southern NCC was likely a coherent ancient terrane at the end of the Neoarchean.

关 键 词：华北克拉通 涑水杂岩 基底岩石 LA-ICP-MS锆石U-PB年龄 HF同位素 

分 类 号：P597.3[天文地球—地球化学]