| 湘西南兰蓉岩体锆石SHRIMP U-Pb年龄、地球化学特征及构造背景 |
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| 引用本文： | 柏道远,陈必河,钟响,熊雄,贾朋远.湘西南兰蓉岩体锆石SHRIMP U-Pb年龄、地球化学特征及构造背景[J].火山地质与矿产,2014(2):95-105. |
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| 作者姓名： | 柏道远 陈必河 钟响 熊雄 贾朋远 |
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| 作者单位： | 湖南省地质调查院,长沙410016 |
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| 基金项目： | 中国地质调查局地质调查项目“湖南1∶25万武冈市和永州市幅区调修测”（项目编号：1212011120793）、中上扬子重点地区（雪峰山）构造演化及其与油气关系研究（1212011220750-02）和“中国地质构造区划综合研究与区域地质志修编”（项目编号：1212010811032）联合资助. |
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| 摘 要： | 湘西南兰蓉岩体为一加里东期小侵入体,由黑云母二长花岗岩和二云母二长花岗岩组成.（443.5±8.1）Ma的锆石SHRIMP U Pb年龄表明花岗岩形成于早志留世早期.主量元素组成表明岩体总体属钙碱性高钾钙碱性系列强过铝质花岗岩类.该侵入体Ba、（Ta＋Nb）、Sr、P、Ti强烈亏损,Rb、（Th＋U＋K）、（La＋Ce）、Nd、（Zr＋Hf＋Sm）、（Y＋Yb＋Lu）等相对富集;稀土元素含量较高、轻稀土富集明显、Eu显著亏损;Isr值为0.71299,εSr（t）值为120,εNd （t）值为 8.11和-8.89,t2DM为1.82和1.84Ga.C/MF-A/MF图解显示其源岩为泥质岩和砂屑岩.上述地球化学特征表明兰蓉岩体为陆壳碎屑岩石部分熔融形成的S型花岗岩.基于岩石成因、构造环境判别以及区域构造演化过程,推断兰蓉岩体的具体形成机制为：奥陶纪末志留纪初的北流运动（板内造山运动）导致地壳增厚、升温,尔后在挤压减弱、应力松弛的后碰撞减压构造环境下,中、上地壳酸性岩石发生部分熔融并向上侵位而形成兰蓉岩体.
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| 关 键 词： | 锆石SHRIMP U-Pb年龄 地球化学特征 S型花岗岩 北流运动 后碰撞构造环境 兰蓉岩体 湘西南 |
SHRIMP U-Pb zircon dating,geochemical features and tectonic setting of the Lanrong pluton in southwestern Hunan Province |
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| BAI Dao-yuan,CHEN N-he,ZHONG Xiang,XIONG Xiong,JIA Peng-yuan.SHRIMP U-Pb zircon dating,geochemical features and tectonic setting of the Lanrong pluton in southwestern Hunan Province[J].Volcanology & Mineral Resources,2014(2):95-105. |
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| Authors: | BAI Dao-yuan CHEN N-he ZHONG Xiang XIONG Xiong JIA Peng-yuan |
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| Institution: | (Hunan Institute of Geology Survey, Changsha 410016, China) |
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| Abstract: | Located in southwestern Hunan Province, Lanrong pluton is a small Caledonian intrusive body, which is composed of biotite monzogranites and two-mica monzogranites. The U-Pb zircon dating for a biotite monzogranite sample yields the weighted average age of （443. 5±8. 1）Ma, which indicates that the Lanrong pluton was formed in early episode of Early Silurian. The major element compositions of granites indicate that the Lanrong granitic rocks belong to calc-alkaline and high-K calc-alkaline series strongly peraluminous granitoids. Ba, （Ta＋Nb）, Sr, P and Ti of the Lanrong granites are pronounced depleted, while Rb, （Th＋U＋K）, （La＋Ce）, Nd, （Zr＋Hf＋Sm） and （Y＋Yb＋Lu） are comparatively enriched. The rocks have high∑REE contents, enriched LREE values, obviously depletedδEu values, Isr value of 0. 71299, εSr（t ） value of 120, εNd（t ） values of -8. 11 and -8.89, t2DM ages of 1. 82 Ga and 1.84 Ga. The C/MF-A/MF diagram indicates that the source rock of the Lanrong granites was originated from pelites and psammites. All above geochemical characteristics indicate that the granites are S-type gra-nitiod and were generated by the partial melting of clastic rocks of the continental crust. Basing on petro-genesis, tectonic setting discrimination and regional tectonic evolution, the formation mechanism of the Lanrong granites is inferred as follows. The Beiliu Movement（ intracontinental orogenesis during late epi-sode of Ordovician to early stage of Silurian） caused crustal thickening and heating, then the weakening of compression and relaxation of stress in post-collisional tectonic setting caused the partial melting of acidic rocks of the middle-upper crust, and upward magmatic emplacement forming the Lanrong pluton. |
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| Keywords: | SHRIMP U-Pb zircon dating geochemical features S-type granitiod Beiliu Movement post-collisional tectonic setting Lanrong pluton southwestern Hunan Province |
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