广西苍梧县社洞钨钼矿床花岗岩类锆石LA-ICP-MS和辉钼矿Re-Os年龄及其地质意义

Zircon LA-ICP-MS U-Pb ages of granitoid rocks and molybdenite Re-Os age of Shedong W-Mo deposit in Cangwu County of Guangxi and its geological significance

广西苍梧县社洞矿床是大瑶山隆起南侧正在勘查的一个与花岗岩类有关的斑岩-矽卡岩-石英脉型钨钼矿床,目前估算的资源量已达中型,并具有大型矿床的潜力。文章对矿区内的花岗岩类分别进行了单颗粒锆石LA-ICP-MS测年和辉钼矿Re-Os测年,获得社山复式岩体花岗斑岩的等时线年龄为(91.05±0.31)Ma,花岗闪长岩为(435.8±1.3)Ma,平头背矿段花岗闪长斑岩脉为(432.0±1.7)Ma,与花岗闪长斑岩脉有关的石英脉型辉钼矿的等时线年龄为(437.8±3.4)Ma。由此推断,其钨钼矿形成于早志留世(即加里东期),与花岗闪长(斑)岩密切相关。这些高精度测年数据的获得,为讨论华南加里东运动的时限和岩浆作用提供了新证据,并反映出加里东期可能存在一定强度的W-Mo-Cu-(Au)成矿作用,对大瑶山地区的找矿工作具有重要意义。

Located in southern margin of Dayaoshan uplift, the Shedong tungsten and molybdenum deposit in Cangwu County of Guangxi is a porphyry-skarn-quartz vein type ore deposit related to granitoids. Zircon LA-ICP-MS U- Pb dating of granitoids yielded the isochron age of granite porphyry [ （91.05 ±0.31 ） Ma） and that of granodiorite [ （435.8 ± 1.3） Ma] in Sheshan multiple stock as well as the isochron age of granodiorite-porphyry [ （432.0 ＋ 1.7） Ma] in Pingtoubei ore blocks. Re-Os isochron age of molybdenite hosted in quartz veins related to gran- odiorite-porphyry veins is （437.8± 3.4） Ma. These high precision dating data suggest that tungsten and molyb- denum mineralization was formed in Early Silurian, related closely to granodiorite （-porphyry）. This new evidence provides constrains on the time of the Caledonian orogeny and magmatic activity in muthern China, and indicates the probable existence of an intense W-Mo-Cu-（Au） mineralization during Caledonian period in Dayaoshan uplift.