吉林敦化大石河钼矿床成因与辉钼矿Re-Os 同位素测年

大石河钼矿床是近年来在小兴安岭-张广才岭钼成矿带南缘新发现的一个大型钼矿床。深部矿体产于似斑状花岗闪长岩体顶部，呈细脉浸染型; 近地表矿体主要呈含辉钼矿石英脉，赋存于浅变质岩中。钼矿化受隐爆角砾岩筒及构造裂隙控制，矿化与蚀变具有明显的分带性，属斑岩型钼矿床。对采自矿区浅部矿体中的5 件辉钼矿样品进行了Re-Os 同位素测年，获得模式年龄( 182. 1 ± 2. 7) ～ ( 191. 9 ± 2. 6) Ma，加权平均年龄( 186. 7 ± 5. 0) Ma，MSWD 值为11. 8，表明大石河钼矿形成于燕山早期。结合近年来小兴安岭-张广才岭钼成矿带上所获得的成岩成矿年龄数据，认为160 ～ 190 Ma 是该钼成矿带的钼矿成矿作用的集中期。辉钼矿样品中Re 含量为3. 549 ～ 4. 362 μg·g － 1，指示成矿物质为壳源。综合分析认为，大石河钼矿床为该区燕山早期大规模成矿事件的产物，形成于古亚洲构造域和环太平洋构造域叠加和转换期的构造环境。

Ore genesis and molybdenite Re-Os dating of Dashihe molybdenum deposit in Dunhua, Jilin

Dashihe deposit is one of the large-size molybdenum deposits recently discovered in the southern margin of Xiaoxinganling——Zhangguangcailing molybdenum metallogenic belt.Deep ore bodies in this deposit are located in the top of porphyaceous granodiorite,veinlet-disseminated in shape.The near-surface ore bodies mainly occurred in the low-grade metamorphic rocks as molybdenite-bearing quartz veins.Molybdenum mineralization was controlled by the explosive breccia pipe and the fissures,and the mineralization and alteration are obvious in zonaition,belonging to porphyry molybdenum deposit.Re-Os dating of five molybdenite samples collected from the shallow ore bodies showed that the model ages as 182.1± 2.7 Ma~191.9±2.6 Ma,with the weighted mean age of 186.7±5.0 Ma,and MSWD=11.8,which indicates the deposit formed in Early Yanshanian.Combined with other obtained lithogenic and metallogenic ages from the Xiaoxinganling——Zhangguangcailing molybdenum metallogenic belt,it can be inferred that 160~190 Ma is a concentrated period for large-scale molybdenum mineralization of this belt.The content of Re in the molybdenite is 3.549~4.362 μg·g-1,indicating ore-forming materials derived from crustal sources.Comprehensive analysis showed that the Dashihe deposit might be resulted by the large-scale mineralization events of the Early Yanshanian in the area,and formed in the tectonic environment during the superposition and transformation of Paleo-Asian and Circum-Pacific tectonic domains.