甘肃北山红柳沟铜镍矿化基性-超基性岩体SHRIMP锆石U-Pb年龄及其地质意义

Zircon SHRIMP U-Pb dating of Hongliugou mafic-ultramafic complex in the Beishan area of Gansu Province and its geological significance

红柳沟铜镍矿化基性-超基性岩体位于塔里木板块北缘北山裂谷带,岩体两侧分别为大山头—岗流脑子、方山口—庙庙井—双鹰山2条区域性深大断裂带。岩体侵位于敦煌岩群,铜镍矿化通常赋存于杂岩体中二辉橄榄岩、橄榄二辉辉长岩、橄榄苏长辉长岩等基性程度较高的岩石内。通过SHRIMP锆石U-Pb定年,首次获得红柳沟矿化橄榄角闪辉长苏长岩锆石的U-Pb年龄为(396.7±3.8)Ma,表明该含矿杂岩体的侵位及矿化作用均发生于中泥盆世,结合区内已知黑山和怪石山等铜镍含矿岩体年龄,从而揭示出甘肃北山地区在中—晚泥盆世一直处于陆缘裂谷拉张环境。

The Hongliugou copper-nickel mineralized mafic-ultramafic rock is located in the Beishan rift belt on the northern margin of the Tarim plate. There are two regional deep fracture zones in the rock on both sides, i.e., Dashantou-Gangliunaozi and Fangshankou-Miaomiaojing-Shuangyingshan. Rock mass was emplaced in the the Dunhuang rock group, copper-nickel mineralization usually occurs in lherzolite, whereas olivine two-pyroxene monzonite and olivine norite-gabbro. SHRIMP U-Pb dating of zircon from the olivine hornblende gabbro norite yielded an age of（396.7±3.8） Ma, which suggests that both the intrusion of the ore-bearing complex and the mineralization occurred in middle Devonian. Combined with the age of Heishan and Guaishishan copper-nickel ore-bearing rock, it is revealed that Beishan area of Gansu was in a continental margin rift extensional environment in the middle-Late Devonian.