Geological survey shows that the Mid-western segment of the Bangong Co-Nujiang River metallogenic belt is a concentration area enriched in magnetite.During the process of the 1:50,000 geological survey in Tibet,we found a ore enriched in magnetite occurring in the quartz diorite in Zhalongqiongwa,which is 20km far away to the NWW from Rutog.Magnetite-riched ore in the Zhalongqiongwa is controlled by NNE-striking normal faults.The ore bodies shape present vein with 3-6m length and and 0.5-3m width.The average grade is as the following:Fe,60 %.Ore veins are minly distributed in the second-order faults on the side of the major faults,which are all covered by the quaternary rock.Several granitic veins are developed in the second-order fault fracture zone,and present individually or associated with ore veins.Therefore,the formation time of granitic veins represents the mineralization time.Through the LAICPMS zircon U-Pb geochronological study,two weighted mean 206Pb/238U age of 85.60±0.48Ma(MSWD=1.3)and 85.57±0.72Ma(MSWD=1.6)for the zircons in quartz diorite and a granitic vein are obtained respectively.During this period,as an important symbol of the extensional movement,the diabase dikes (86.1±1.5 Ma,MSWD=3.0) crops out in both sides of the Bangong Co-Nujiang River suture zone.Therefore,the extensional event at 85.57Ma is responsible for the oreforming and ore-controlling fissures.