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

Abstract: 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.