| 内蒙古额仁陶勒盖地区侵入岩LA-ICP-MS锆石U-Pb年龄及地球化学特征 |
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| 引用本文： | 田 京,李进文 王润和 刘 文 向安平 康永建 郭志军 董旭舟.内蒙古额仁陶勒盖地区侵入岩LA-ICP-MS锆石U-Pb年龄及地球化学特征[J].中国地质,2014,41(4):1092-1107. |
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| 作者姓名： | 田 京 李进文 王润和 刘 文 向安平 康永建 郭志军 董旭舟 |
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| 作者单位： | 中国地质科学院矿产资源研究所;中国地质大学(北京)地球科学与资源学院;内蒙古地质矿产勘查院; |
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| 基金项目： | 科技部973项目(2013CB428805);中国地质调查局地质调查项目(1212011085260、科[2013]01-042-003)联合资助 |
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| 摘 要： | 额仁陶勒盖银矿床是中国内蒙古地区一个大型浅成低温热液型银矿床。通过对矿区石英斑岩、石英二长岩、黑云母正长花岗岩及细粒花岗岩等侵入岩进行了年代学及地球化学研究。LA-ICP-MS锆石U-Pb年龄结果表明,4件侵入岩样品的锆石U-Pb年龄分别为(285.4±1.9)Ma、(294.3+0.6)Ma、(287.0±1.2)Ma及(243.9±1.6)Ma,表明矿区主要侵入岩形成于2个时期,即海西晚期与印支期。前3者的年龄表明其均为海西晚期岩浆演化产物,其地球化学特征显示,亏损Ba、Nb、Sr、Zr、Ti等大离子不相容元素,显著富集K、亏损Ta,弱的负Eu异常,(Y+Nb)-Rb和Yb-Ta花岗岩构造环境判别图上均显示为弧花岗岩,且为过铝质S型花岗岩;结合区域构造演化认为其形成受古亚洲洋闭合的影响,形成于同碰撞构造环境。细粒花岗岩的锆石U-Pb年龄为(243.9±1.6)Ma,表明其为印支期岩浆演化的产物,其地球化学特征显示,同样亏损Ba、Nb、Sr、Zr、Ti等大离子不相容元素,显著富集K、亏损Ta,弱的负Eu异常,(Y+Nb)-Rb和Yb-Ta花岗岩构造环境判别图上显示为弧花岗岩,且为过铝质S型花岗岩;结合区域构造演化认为其形成受蒙古-鄂霍茨克洋陆内俯冲作用的影响,形成于火山弧构造环境。依据前人研究成果,矿区赋矿围岩为中侏罗统塔木兰沟组火山岩,其~(40)Ar-~(39)Ar等时线年龄为(162.6±0.7)Ma,说明本次所采集的侵入岩与矿床的形成均无成因联系。
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| 关 键 词： | 侵入岩 锆石U-Pb LA-ICP-MS 地球化学 构造背景 额仁陶勒盖地区 内蒙古 |
Zircon LA-ICP-MS U-Pb ages and geochemical?features of intrusions in Erentaolegai area of Inner Mongolia |
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| TIAN Jing,LI Jin-wen,WANG Run-he,LIU Wen,XIANG An-ping,KANG Yong-jian,GUO Zhi-jun,DONG Xu-zhou.Zircon LA-ICP-MS U-Pb ages and geochemical?features of intrusions in Erentaolegai area of Inner Mongolia[J].Chinese Geology,2014,41(4):1092-1107. |
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| Authors: | TIAN Jing LI Jin-wen WANG Run-he LIU Wen XIANG An-ping KANG Yong-jian GUO Zhi-jun DONG Xu-zhou |
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| Institution: | 1. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China; 2. School of Earth Science and Mineral Resources, China University of Geosciences, Beijing 100083, China; 3. Inner Mongolia Institute of Geology and Mineral Exploration, Hohhot 010011, Inner Mongolia, China |
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| Abstract: | Abstract: The Erentaolegai silver deposit is a large epithermal silver deposit in Inner Mongolia. In this paper, chronologic and geochemical research were carried out on such intrusions as quartz porphyry, quartz monzonite, biotite syenogranite and fine-grained granite in the ore district. The zircon LA-ICP-MS U-Pb dating?results show that the zircon U-Pb ages of the four intrusion samples are (285.4±1.9) Ma, (294.3±0.6) Ma, (287.0±1.2) Ma and (243.9±1.6) Ma respectively, which shows that the intrusions in the ore district were formed in the two periods of Late Hercynian and Indosinian. The age of the first three samples show that they were formed by magmatic evolution in the Late Hercynian period, and their geochemical features show the depletion of large ion incompatible elements such as Ba, Nb, Sr, Zr and Ti, the remarkable enrichment of K and the depletion of Ta, with weak negative Eu anomalies, and exhibit arc granite characteristics in (Y+Nb)-Rb and Yb-Ta?tectonic environment discrimination diagrams for granitic rock and peraluminous S type granite, which suggests that they were formed in a tectonic environment of syn-collison in combination with the regional tectonic evolution. The zircon U-Pb age of the fine-grained granite is ( 243.9±1.6 ) Ma, suggesting that it was formed by magmatic evolution in the Indosinian period; in addition, its geochemical features show the depletion of large ion incompatible elements such as Ba, Nb, Sr, Ti, Zr and Ti, the remarkable enrichment of K and the loss of Ta, with weak negative Eu anomalies, and has arc granite characteristics in (Y+Nb)-Rb and Yb-Ta?tectonic environment discrimination diagrams for granitic rock and peraluminous S type granite, which implies that it was formed in a tectonic environment of volcanic arc in conjunction with the regional tectonic evolution. According to previous studies, the wall rock of the ore district is Tamulangou volcanic rock formed in the Middle Jurassic, and its 40Ar-39Ar?isochron age is (162.6±0.7) Ma, which shows that there is no genetic relationship between the intrusion and the deposit. |
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| Keywords: | intrusion zircon U-Pb LA-ICP-MS geochemistry tectonic setting Erentaolegai ore district Inner Mongolia |
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