中条山涑水杂岩中TTG片麻岩的锆石Hf同位素特征及其形成环境  

Zircon Hf isotopic features of TTG gneisses and formation environment of Precambrian Sushui complex in Zhongtiao mountains.

作　　者：郭丽爽[1] 刘树文[1] 刘玉琳[1] 田伟[1] 余盛强[1] 李秋根[1] 吕勇军[1] 

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室,北京100871

出　　处：《岩石学报》2008年第1期139-148,共10页Acta Petrologica Sinica

基　　金：国家自然科学基金重大国际合作项目(资助号:40412012035);国家自然科学基金面上项目(资助号:40472096);国家自然科学青年基金(资助号:40602022)联合资助

摘　　要：中条山前寒武纪涑水杂岩主要由西姚和寨子英云闪长质-奥长花岗质-花岗闪长质(TTG)片麻岩、横岭关和北峪钙碱性花岗质岩石组成。SHRIMP锆石U-Pb年代学研究表明,西姚石英闪长质片麻岩^(207)Pb/^(206)Pb加权平均年龄为2536±8Ma,是新太古代的产物;西姚和寨子TTG片麻岩及横岭关和北峪钙碱性花岗质岩石岩浆锆石Hf同位素组成ε_(Hf)(t)全为正值,且在t-ε_(Hf)(t)图解上,落在2.6～3.1Ga地壳演化线范围内。北峪钙碱性花岗质岩石中三个继承锆石核的^(207)Pb/^(206)Pb加权平均年龄为2633±84Ma,其锆石ε_(Hf)(t)值为-2.0～+5.6。前寒武纪涑水杂岩中花岗质岩石的SHRIMP锆石U-Pb年代学和锆石Hf同位素特征揭示它们最可能形成于新太古代到古元古代,岩浆主要来源于约2650Ma初生地壳的部分熔融,并有更古老的地壳物质的加入。The Precambrian Sushui Complex in Zhongtiao Mountain is composed principally of Xiyao and Zhaizi TTG gneisses, Henglingguan and Beiyu calc-alkaline granitoids. SHRIMP zircon U-Pb dating for Xiyao TTG gneiss yield the weighted mean 207Pb/206Pb age of 2536 ± 8Ma, revealing that it was formed in the Neoarchean. In-situ zircon Lu-Hf isotopic analyses of Xiyao and Zhaizi TTG gneisses and Henglingguan-Beiyu calc-alkaline granitoids show that the magmatic zircons have positive εHf（t） values, and these εHf（t） values are plotted within the revolution areas of the 2600 - 3100Ma old continental crust in the age vs. εHf（t） diagrams. The analytical spots of three inherited zircon cores from the Beiyu calc-alkaline granitoid yield a weighted mean 207Pb/206Pb age of 2633±84Ma,and the εH（t） values of these inherited cores of magmatic zircon gains are, -2.0 - ＋5.6. The characteristics of zircon SHRIMP U-Pb ages and Hf isotope compositions of these TTG gneisses and calc-alkaline granitoids from the Precambrian Sushui Complex indicate that they were possibly formed in the Neoarchean to Paleoproterozoic tectonic settings of Andes-type continent margin, and the magmas could be derived from the partial melting of juvenile crust materials from the depleted mantle and more older continental crust materials.

关 键 词：涑水杂岩 花岗质片麻岩 SHRIMP锆石年代学 锆石HF同位素 岩石成因 形成环境 

分 类 号：P597.3[天文地球—地球化学]