赣中大王山石英脉型钨钼多金属矿床成岩成矿年代学及其地质意义

赣中大王山钨钼多金属矿床位于钦杭结合带西缘大王山—于山W-U-Sn-Au多金属成矿带,为典型的石英脉型矿床,其赋矿岩体具有多阶段特征。通过LA-ICPMS锆石U-Pb测年技术,得到晚阶段细粒花岗岩成岩年龄为145.1±0.89 Ma,与早阶段形成的中粗粒花岗岩形成时间接近(147.8±1.9 Ma);利用辉钼矿Re-Os同位素测年技术,得到成矿年龄为147.6±1.8 Ma,表明该矿床形成于晚侏罗世,与南岭地区及其周边的燕山期石英脉型钨钼多金属矿床的成岩、成矿时代一致。辉钼矿中Re的含量具有指示成矿物质来源的重要参考价值,大王山钨多金属矿床的辉钼矿中Re含量较低,为2 215×10^-9～10 183×10^-9,与以钨为主、共生或伴生钼的矿床特征相吻合,指示其成矿物质主要来自于壳源或壳幔混合源,即在160～110 Ma之间,古太平洋板块与欧亚板块之间的主应力作用方向发生转变,促使我国东部岩浆活动频繁,岩浆期后热液与围岩碱交代明显,大量成矿物质被萃取,并在成矿有利部位富集。

Petrogenic and metallogenic geochronology and its geological significance of the Dawangshan quartz vein type scheelite-molybdenite polymetallic deposit in central Jiangxi Province

The Dawangshan tungsten-molybdenum polymetallic deposit in Jiangxi province is a typical quartz vein type deposit, lies in the Dawangshan-Yudu Cu-Mo-Au-Ag-Pb-Zn ore belt. The ore-bearing rock mass is characterized by multiple stages. According to the LA-ICPMS zircon U-Pb dating technique, the diagenetic age of fine-grained granite in the late stage is 145.1±0.89 Ma, which is close to the formation time of medium-grained granite formed in the early stage (147.8±1.9 Ma). Using the Re-Os isotope dating technique of molybdenite, the metallogenic age was 147.6±1.8 Ma. Indicating that the deposit was formed in the late Jurassic, It is consistent with the diagenesis and mineralization age of Yanshanian quartz vein type tungsten molybdenum polymetallic deposit in Nanling area. Re content of molybdenite has important reference value to indicate the source of mineralization materials. The Dawangshan tungsten-molybdenum polymetallic deposit is related with Yanshanian granites, the Re contents of molybdenite samples is 2 215×10^-9 ~10 183×10 ^-9 , It is consistent with the characteristics of tungsten deposit associated molybdenum,which indicates that the ore-forming materials are likely to come from the crust or crust-mantle-derived ones. In combination with metallogenic geological background, the author infers that the Dawangshan deposit is associated with the subduction of the Paleo-Pacificocean plate beneath the Eurasian continent. It is proposed that the ore-forming materials were extracted by alkali metasomatism between the magma and the wall rock and then concentrated in the favourable areas.