河北省青龙满族自治县四拨子—六拨子钼铜矿床的辉钼矿Re-Os年龄及意义

Re-Os ages of molybdenite from the Sibozi-Liubozi molybdenum-copper deposit in Qinglong County of Hebei Province and Its Implications for Metallogeny

河北省青龙满族自治县四拨子—六拨子钼铜矿位于燕辽成矿带东部,是近年来发现的中型钼铜矿床。辉钼矿呈细脉状、网脉状、浸染状赋存于长城系石英砂岩及白云岩中的矽卡岩带,钼矿化与硅化关系密切。矿体呈似层状、脉状和透镜状。对矿石中辉钼矿Re-Os同位素年代学进行了研究,7件样品的Re-Os同位素模式年龄为(191.6±2.7)Ma～(196.0±2.9)Ma,加权平均值为(194±1)Ma,2件样品的模式年龄值为(121.1±1.8)Ma～(125.9±1.9)Ma。四拨子—六拨子矿区的主成矿时代为早侏罗世早期(196～192 Ma),钼成矿作用与老商家花岗斑岩和五拨子花岗斑岩(196～190 Ma)的侵入活动有关。矿区存在的早白垩世末(121～126 Ma)钼成矿作用为目前燕辽地区最晚的。辉钼矿样品的Re含量变化于6.475～6.923μg/g和38.74～71.358μg/g,指示钼铜成矿物质有壳幔混源的特征。

Located in eastern Yanliao metallogenic belt,the Siboozi-Liubozi molybdenum-copper deposit in Qinglong County is a newly-discovered medium-size molybdenum-copper deposit.Molybdenite occurs as veinlets,stockworks and disseminations in the skarn hosted in quartz sandstone and dolomite of Changcheng System.Molybdenum mineralization is closely related to silicification.Ore bodies occur in stratoid,veined and lenticular forms.Precise Re-Os dating of molybdenite from the molybdenite-quartz vein in ore was studied in this paper.The results show that the Re-Os model ages of seven samples range from（191.6±2.7） Ma to（196.0±2.9） Ma,with the weighted mean age of（194±1） Ma,and the Re-Os model ages of two samples range from（121.1±1.8） Ma to（125.9±1.9） Ma,suggesting that the main metallogenic epoch of the Sibozi-Liubozi molybdenum-copper deposit was formed in the earliest Jurassic period（196～192 Ma） and that molybdenum mineralization was probably related to granite-porphyry（196～190 Ma） intrusive activities of Laoshangjia and Wubozi.Molybdenum metallogenesis of Lower Cretaceous（121～126Ma）in the ore district is the latest data reported in Yanliao area.The rhenium values of molybdenite samples are in the range of 6.475～6.923μg/g and 38.74～71.358μg/g,implying that Mo and Cu were derived not only from the crust but also from the mantle-crust mixed source.