中条山篦子沟铜矿辉钼矿铼-锇同位素年龄及其地质意义

篦子沟铜矿位于山西中条山胡-篦型铜矿田,矿体与地层产状一致,呈层状、似层状分布于中条群篦子沟组和余元下组中,经历了多期次多阶段成矿作用。为限定篦子沟铜矿后期热液脉状矿化的形成时代,对篦子沟铜矿区方解石-石英脉中与黄铜矿共生的辉钼矿样品进行了Re-Os同位素测定。结果表明,6件辉钼矿样品Re-Os同位素模式年龄为(1 539±26)~(1 616±26)Ma,加权平均年龄为(1 577±31)Ma(MSWD=5.5),等时线年龄为(1 522±180)Ma(MSWD=9.6),表明热液脉状矿化形成于中元古代长城纪晚期。据此篦子沟铜矿的热液脉状矿化可分为3个成矿期次,分别为古元古代晚期发生的微细脉浸染状矿化期、脉状矿化期和中元古代早期热液脉状辉钼矿矿化期。此次事件可能为中元古代伸展-裂解事件岩浆侵位产生的热液对原来的篦子沟铜矿进行再次的矿化、富集。结合已有资料,证明篦子沟以及中条山地区在中元古代早期存在热液矿化事件。

Re-Os Isotopic Dating of Molybdenite from Bizigou Cu Deposit in Zhongtiao Mountain and Its Implication

The Bizigou Cu deposit is located in the field of "Hu-Bi" type Cu ore district in Zhongtiao mountain in the southern edge of the North China craton,and it was formed through multiple mineralization events.The orebodies are consistent with the attitude of stratum,and are bedded in the Bizigou Formation and Yuyuanxia Formation.Molybdenite and chalcopyrite occur disseminated in the molybdenite-bearing calcite-quartz veins.Re-Os molybdenite model ages fall in the range from (1 539± 26) to (1 616±26) Ma with an isochron age of (1 522±180) Ma (MSWD=9.6) and a weighted mean model age of (1 577±31) Ma (MSWD=5.5),suggesting its hydrothermal vein mineralization formation in the Mesoproterozoic.In the hydrothermal mineralization of the Bizigou deposit,three mineralization events were identified:Paleoproterozoic disseminated mineralization,Paleoproterozoic vein-type mineralization,and Mesoproterozoic vein-type mineralization.This study indicates the existence of a Mesoproterozoic hydrothermal Cu mineralization event in the Bizigou and Zhongtiao Mountain region combining with the existing data.