Zircon U-Pb and molybdenite Re-Os dating of the Langlike copper deposit in North Qilian Mountain and its geological implications

Abstract: Located in the Lenglongling volcanic belt of North Qilian Mountain, the Langlike copper deposit is a medium-sized deposit with mineralization mainly occurring in quartz dioritic porphyrite. Based on an analysis of the mineralization features of the deposit, the authors used the zircon LA-ICP-MS U-Pb and molybdenite ICP-MS Re-Os highly precise dating techniques to study the ore-bearing quartz dioritic porphyrite and five samples of molybdenum collected from the deposit. Zircon U-Pb dating yielded an age of (461.5±7.3) Ma for quartz dioritic porphyrite. The Re-Os model ages of the molybdenite samples vary from (467.1±6.3) Ma to (471.3±6.7) Ma and the Re-Os isochron age is (470.5±3.4) Ma. The similar zircon U-Pb and molybdenite Re-Os isotopic ages suggest that the Langlike copper deposit formed in middle Ordovician and it had a close temporal relationship with the quartz dioritic porphyrite. Combined with the tectonic evolution of the North Qilian, the authors hold that the deposit was produced in an island arc tectonic setting triggered by slab subduction and was similar to the porphyry deposit. These characteristics are of important significance for investigating the genetic type of the Langlike copper deposit and for further prospecting work.