LA-ICP-MS zircon U-Pb dating of Narigongma biotite granite porphyry in northern Sanjiang region and its geological significance

Narigongma biotite granite porphyry in northern Sanjiang region is an important porphyry type copper-molybdenum mineralization belt in Qinghai Province,and the Narigongma copper-molybdenum deposit is an intrusion-related porphyry type ore deposit recently discovered in northern Sanjiang region.The authors obtained the zircon U-Pb age of 41.53±0.24Ma for Narigongma biotite granite porphyry,which should belong to early Himalayan period.The main metallogenic age is between 40.86 and 40.8 Ma.In multi-phase hydrothermal superimposition and mineralization,the hydrothermal solution of the Narigongma porphyry copper-molybdenum deposit must have been derived from biotite granitite porphyry of 41.53±0.24 Ma and plagioclase granite porphyry of 41.0±0.18Ma.In virtue of existence of many intermediate-acid intrusive rocks,the age determination of these intrusive is not only of theoretical importance but also of practical significance in search for porphyry type copper-molybdenum deposits of the same epoch.