Gaerqiong deposit is a new found copper—gold (iron) deposit in Western Bangong Lake(Bangong Co)—Nujiang River metallogenic belt, which is hosted in the skarn belt in the contact zone of porphyry and carbonatite and in the fault fracture zone. It is located in the Coqen—Xainza magmatic arc in the south edge of Bangong Lake—Nujiang River suture zone. Based on the previous research, this paper is to solve the puzzle that porphyry emplacing is older 22Ma or more than ore forming, and to redefine the ore forming time range of the deposit by chronology research. A detailed survey of the deposit characteristics was carried out, and quartz diorite is determined as the ore forming porphyry. The LA ICP MS U Pb dating and cathodeluminescence was carried out for the zircon grains from quartz diorite. The cathodeluminescence images show that zircon grains have clear magmatic zonation, with the ratio of long axis to short axis range from 1.5 to 4:1. The analytical results indicate that the weight average 206Pb/238U age of 15 points on the grains is 87.1±0.4Ma（MSWD= 0.88）, which represents the porphyry’s forming age. As the Re Os isochron age of molybdenite from ore is 86.87±0.50 Ma in the deposit, it is concluded that it took 1Ma for fluid evolving and orebody forming after the crystallization of porphyry. We inferred that the deposit was formed during the arc—landmass collision between Gangdise—Nyainqentangglha plate and Southern Qiangtang—Sanjiang composite plate after the Bangong Lake—Nujiang Thetis Ocean closed.