The south Gangdese region is the site of subduction of the Neo-Tethys and subsequent continental collision. Compared with widespread Cretaceous and Cenozoic magmatism, Early–Middle Jurassic magmatic rocks and related...The south Gangdese region is the site of subduction of the Neo-Tethys and subsequent continental collision. Compared with widespread Cretaceous and Cenozoic magmatism, Early–Middle Jurassic magmatic rocks and related deposits are rarely reported. Our work identified a >200 km long felsic rock belt associated with Cu mineralization in the south Gangdese region. We report here zircon U–Pb ages, zircon Ce^(4+)/Ce^(3+)values, and mineral assemblages of two Cu mineralized intrusions within the belt. A hornblende granite and a diorite porphyry were emplaced at 177.3 Ma and 166.3 Ma, respectively.Geological occurrence and magmatic hematite–magnetite–chalcopyrite intergrowths suggest that Cu mineralization formed coeval with Jurassic intrusions. Mineralized intrusions have high zircon Ce^(4+)/Ce^(3+)and EuN/Eu?N ratios, and hematite–magnetite intergrowths, suggesting their parent magmas were highly oxidized. Hornblende is common and primary fluid inclusions are found in titanite and apatite,indicating their parent magmas were water-saturated and exsolved volatile phases at early stage of magmatic evolution. Those magma characters contribute to the formation of porphyry Cu deposits. Given that majority subduction-related porphyry Cu systems have been eroded following uplift and denudation, the well-preserved Early–Middle Jurassic Cu mineralized igneous rocks in south Gangdese are favorable prospecting targets for subduction-related porphyry Cu deposits.展开更多
基金supported by Strategic Priority Research Program of Chinese Academy of Sciences(XDB03010302)the DREAM project of MOST,China(2016YFC0600407)a contribution No.IS-2396 from GIGCAS
文摘The south Gangdese region is the site of subduction of the Neo-Tethys and subsequent continental collision. Compared with widespread Cretaceous and Cenozoic magmatism, Early–Middle Jurassic magmatic rocks and related deposits are rarely reported. Our work identified a >200 km long felsic rock belt associated with Cu mineralization in the south Gangdese region. We report here zircon U–Pb ages, zircon Ce^(4+)/Ce^(3+)values, and mineral assemblages of two Cu mineralized intrusions within the belt. A hornblende granite and a diorite porphyry were emplaced at 177.3 Ma and 166.3 Ma, respectively.Geological occurrence and magmatic hematite–magnetite–chalcopyrite intergrowths suggest that Cu mineralization formed coeval with Jurassic intrusions. Mineralized intrusions have high zircon Ce^(4+)/Ce^(3+)and EuN/Eu?N ratios, and hematite–magnetite intergrowths, suggesting their parent magmas were highly oxidized. Hornblende is common and primary fluid inclusions are found in titanite and apatite,indicating their parent magmas were water-saturated and exsolved volatile phases at early stage of magmatic evolution. Those magma characters contribute to the formation of porphyry Cu deposits. Given that majority subduction-related porphyry Cu systems have been eroded following uplift and denudation, the well-preserved Early–Middle Jurassic Cu mineralized igneous rocks in south Gangdese are favorable prospecting targets for subduction-related porphyry Cu deposits.
