Study on zircon LA-ICP-MS U-Pb age of skarn Cu mineralization related intrusion in the southern margin of the Gangdese ore belt, Tibet and its geological implication
西藏冈底斯矿带南缘矽卡岩型铜矿床含矿岩体锆石U-Pb年龄及意义

A lot of porphyry Cu-Mo deposits and Cu-Pb-Zn polymetal ore deposits have been found in the southern Gangdese, which form a porphyry copper ore belt and polymetal ore belt in the southern Gangdese, respectively. Former work suggests that the deposits found in the southern Gangdese were formed in post collision environment with isotope age less than 30Ma. Here we report a relatively older zircon LA-ICP-MS U-Pb age for the Sangbujiala intrusion genetically associated with skarn Cu (Au) mineralization in the southern margin of the Gangdese terrain. The Sangbulajia intrusion has zircon LA-ICP-MS U-Pb age of 92.1±0.6Ma with MSWD=1.0. The Ce4+/Ce3+ ratios of the zircon grains vary from 90 to 562, with an average value of 287, which is similar to those of porphyries associated with Cu-Mo mineralization in the Yulong ore belt, suggesting that the intrusive melt is characterized by relatively high oxygen fugacity. The collision of India with Asia occurred during 65~45Ma. Our new zircon age of the Sangbujiala intrusion genetically associated with Cu (Au) mineralization suggests that the southern Gangdese has undergone mineralization events not only associated with postcollision environment but also with subduction of the Neotethyan ocean crust. The new zircon age for the Sangbujiala intrusion reveals that the southern Gangdese could be next exploring target for mineralization related to oceanic crust subduction.