摘要:
提要：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40Ar-39Ar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。
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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