内蒙古八大关斑岩型铜钼矿床成岩成矿年代学研究  

Study of rock_forming and ore_forming ages of Badaguan prophypy Cu_Mo deposit in Inner Mongolia

作　　者：康永建[1] 王亚君 黄光杰 佘宏全[1] 向安平[1] 田京[1,4] 郭志军[1] 董旭舟[4] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]内蒙古第六地质矿产勘查开发院,内蒙古海拉尔021008 [3]内蒙古地质勘查有限公司,内蒙古呼和浩特010020 [4]中国地质大学地球科学与资源学院,北京100083

出　　处：《矿床地质》2014年第4期795-806,共12页Mineral Deposits

基　　金：地质调查项目(编号:1212011120992);国家重点基础研究计划项目(编号:2013CB429803)联合资助

摘　　要：八大关斑岩铜钼矿床是中国内蒙大兴安岭地区典型的斑岩型铜钼矿床之一。对矿区Ⅱ号岩体不同位置的2件岩石样品采用高精度的LA_ICP_MS锆石U_Pb测年,获得的锆石U_Pb年龄分别为(230.6±2.8)Ma和(230.5±4.4)Ma,两者在误差范围内非常一致,由此确认花岗闪长斑岩体的形成年龄约为230 Ma;对矿区7件辉钼矿样品采用Re_Os同位素测年,获得的Re_Os等时线年龄为(228.7±3.1)Ma,指示了八大关铜钼矿床辉钼矿的沉淀时间约为228.7 Ma。结合矿区岩相学、矿物学特征,辉钼矿呈浸染状分布于花岗闪长斑岩体内,且辉钼矿与黄铜矿密切共生,以及上述2种精确方法获得的年龄在误差范围内的一致性,说明花岗闪长斑岩即为成矿岩体,成岩与成矿大致同时或成矿略晚于成岩,表明八大关铜钼矿床形成于中三叠世,属于印支期成矿。The Badaguan porphyry Cu-Mo deposit is one of the typical porphyry Cu-Mo deposits in the Da Hinggan Mountains. Systematic isotope dating was conducted to constrain the age of the deposit. LA-ICP-MS zircon U- Pb dating of two different rock samples yielded the ages of （230.6 ± 2.8） Ma and （230.5 ± 4.4） Ma respectively. The two ages are in agreement within the deviation, suggesting that the rock-forming age is about 230 Ma. Meanwhile, Re-Os isotopic age analysis of seven molybdenite yielded a weighted average model age of （228.7 ± 3.1） Ma, which implies that the precipitation age of the molybdenite is about 228.7 Ma. Mineralogical and petrological characteristics show that molybdenite occurs within the quartz diorite porphyrite in dissemination form and is closely associated with chalcopyrite. The dating results of the two precise methods are concordant within the error range, which suggests that the quartz diorite porphyrite might have been the metallogenic intrusive mass and the mineralization approximately occurred simultaneously with or slightly later than the rock-forming process. These data suggest that the Badaguan Cu-Mo deposit was formed in the Middle Triassic and be- longed to indo-Chinese mineralization.

关 键 词：地球化学 LA-ICP-MS锆石U-PB测年 成矿时代 斑岩铜-钼矿床 中三叠世 八大关 内蒙古 

分 类 号：P618.41[天文地球—矿床学] P618.65[天文地球—地质学]