大兴安岭北段库伦迪-那吉河铅锌银矿成矿流体特征与矿床成因

Ore-forming fluid characteristics and genesis of the Kulundi-Najihe lead-zinc-silver deposit in northern Da Hinggan Mountains

大兴安岭成矿带是中国五大重点有色金属成矿带之一，库伦迪-那吉河铅锌银矿床是其北段中部近年新发现的中-大型矿床之一，已控制的铅锌资源量达到中型规模，银资源量达到大型规模。矿区的流体包裹体和金属矿物S、Pb同位素研究表明，铅锌矿流体包裹体以气液包裹体为主，成矿温度为310～340℃，盐度小于6%，成矿流体密度为0.67～0.70g/cm3，推测成矿流体主要来自火山期后热液，后期有地表水的加入；成矿物质主要为深部来源（幔源），部分为中酸性岩浆期后流体萃取老地层中的成矿物质；根据Pb同位素单阶段演化曲线的模式年龄，推测为175Ma和138Ma两期成矿。综合分析认为，矿床成因类型为火山热液型。

The northern Da Hinggan Mountains area is one of the most important polymetallic metallogenic belts, where the Kulun-di-Najihe lead-zinc-silver deposit was discovered in recent years. Recent exploration shows medium to large scale reserves of lead and zinc resources and large scale silver resources. This paper mainly presents the researches on orebody characteristics and analytical results of fluid inclusions and stable isotopes in order to better understand the origin, metallogenic age and tectonic setting of the Ku-lundi-Najihe lead-zinc-silver deposit and further to make the exploration breakthrough of the lead-zinc-silver-polymetallic de-posits in north Da Hinggan Mountains. The analytical results show that fluid inclusions in the deposit mostly belong to typical gas-liq-uid inclusions, with the metallogenic temperature ranging from 310 to 340℃, the salinity of the ore-forming fluid lower than 6%, and the density being 0.67～0.70g/cm3, suggesting that the ore-forming fluid was probably derived mainly from the post-magmatic hydrothermal solution, with the addition of some surface water. Isotope analyses of S, Pb indicate that the ore-forming material was mostly derived from the depth with characteristics of mantle source, and the crust-mantle mixing post-magmatic hydrothermal fluid probably extracted ore-forming materials from old strata. The model age of Pb isotope single-stage evolution curve was used to con-strain the metallogenic age, and the results obtained show that this deposit was formed in two periods, i.e., about 175Ma and 138Ma re-spectively. It is held that the deposit belongs to a typical epithermal deposit related to post intermediate-acidic magmatism.