| 内蒙古正蓝旗钱家营子黑云母二长花岗岩锆石U-Pb年代学、Hf同位素特征及其地质意义 |
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| 引用本文：李亚东,江小均,柳永清,李超,孙会一,芦磊.2021.内蒙古正蓝旗钱家营子黑云母二长花岗岩锆石U-Pb年代学、Hf同位素特征及其地质意义[J].地球学报,42(1):85-97. |
| DOI：10.3975/cagsb.2020.090602 |
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| 基金项目:中国地质调查局项目(编号: 1212010610421) |
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| 中文摘要:钱家营子岩体位于赤峰—围场—白云鄂博断裂以北白乃庙岛弧带上, 为兴蒙造山带南缘构造-岩浆岩带的重要组成部分, 其时代及成因对理解中亚造山带构造格局及地质演化过程具有重要意义。本文在1:25万区域地质调查基础上, 对钱家营子黑云母二长花岗岩体进行岩相学、锆石SHRIMP U-Pb年代学、Hf同位素组成特征开展综合研究。结果表明, 岩体的锆石206Pb/238U加权平均年龄为(247.2±4.7) Ma, 指示其形成于早三叠世末期。176Hf/177Hf值为0.282 298~0.282 371, 对应的εHf(t)值为–8.7 ~ –11.4, 其两阶段模式年龄变化在1.60 Ga到1.74 Ga之间, 表明钱家营子黑云母二长花岗岩母岩浆可能来源于古元古代华北板块加厚下地壳的部分熔融。综合岩体地球化学特征及区域相关研究, 认为内蒙古正蓝旗钱家营子地区在早三叠世处于兴蒙造山带和华北板块后造山(碰撞)的伸展环境。 |
| 中文关键词:内蒙古 钱家营子 锆石SHRIMP U-Pb定年 Hf同位素 |
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| Geochronology and Hf Isotopic Composition of the Biotite Monzogranite from the Qianjiayingzi Area in Zhenglan Banner of Inner Mongolia and Its Geological Implications |
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| Abstract:The Qianjiayingzi pluton is located in the Bainaimiao island arc belt to the north of Chifeng–Weichang–Baiyunebo fault. It is the most important part of the tectonic-magmatic belt on the southern margin of Xingmeng orogenic belt. Its formation age and genesis are of great significance for evaluating the tectonic setting and geological evolution in this orogenic belt. Based on 1:250000 regional geological survey, the authors investigated petrography and zircon U-Pb-Hf isotopic composition of Qianjiayingzi biotite monzogranite. The results show that the weighted average age of zircon 206Pb/238U is (247.2±4.7) Ma, indicating that the biotite monzogranite was formed in the late Early Triassic. The 176Hf/177Hf values of samples are 0.282 298~0.282 371, corresponding to the εHf(t) values of –8.7 ~ –11.4, and the tDM2 values of Hf isotopes are 1.64~1.74 Ga, suggesting that the parent magma of Qianjiayingzi biotite monzogranite may have been derived from the partial melting of the Paleoproterozoic old lower crust. Based on the geochronology and Hf isotopic characteristics of biotite monzogranite, it is considered that Qianjiayingzi area of Zhenglan Banner in Inner Mongolia was in an extensional environment of post collision between Xingmeng orogenic belt and North China plate in Early Triassic. |
| keywords:Inner Mongolia Qianjiayingzi zircon SHRIMP U-Pb dating Hf isotope |
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