Jurassic-Cretaceous granitoids and related tectono-metallogenesis in the Zapug-Duobuza arc, western Tibet

The Zapug-Duobuza magmatic arc (ZDMA), located along the southern edge of the south Qiangtang terrane in western Tibet, extends east-west for similar to 400 km. Small scattered granite and porphyry intrusions crop out in the ZDMA, but a large amount of granite may be buried by Late Cretaceous to Paleogene thrusting. Two stages of magmatism have been identified, at 170-150 Ma and 130-110 Ma. The widely distributed Middle-Late Jurassic granite intrusions in the ZDMA exhibit Sr-Nd isotopic characteristics similar to those of ore-bearing porphyries in the Duolong giant Cu-Au deposit, and their epsilon Hf(t) values mostly overlap those of other porphyry Cu-Mo deposits in the ZDMA and the Gangdese zone. The Sr-Nd-Hf isotopic geochemistry suggests variable contributions of mantle and Qiangtang crustal sources, and indicates the presence of two new ore districts with potentials for Cu-Au, Fe, and Pb-Zn ores, located in the Jiacuo-Liqunshan and Larelaxin-Caima areas. Except for the Duolong ore-forming porphyries, which show significant contributions of mantle components intruded into an accretionary melange setting, the Early Cretaceous granites in other areas of the belt are of mostly crustal origin, from sources in Qiangtang felsic basement and Permo-Carboniferous strata, indicating the weak ore-forming potential of skarn-type Fe and Pb-Zn deposits. The ephemeral but deep Bangong Co-Nujiang ocean in the Early Jurassic evolved into a shallow compressional marine basin in the Middle-Late Jurassic, possibly transitioning to northward flat subduction of oceanic crust at this time. The subducted slab broke off in the Early Cretaceous, initiating a peak in arc magmatism and metallogenesis at 125-110 Ma. (C) 2016 Elsevier B.V. All rights reserved.