Abstract:

 The Machangqing porphyry CuMoAu deposit is one of the typical deposits associated with the alkalinerich porphyry in the JinshajiangAilaoshan tectonic belt of the Himalayan epoch. Alkalite intrusive rock is a superimposed intrusive complex formed by multiperiodic and multistage magmatic activities. The time limit of magmatic activity is 6429 Ma. In situ zircon LAICPMS UPb ages and molybdenite ReOs ages indicate that the age of orebearing granite prophyry is 3793±082 Ma, whereas the mineralization age is 3472±05 Ma, which shows that the mineralization mainly related to the later magmatic activity. The closeness among zircon UPb, molybdenite ReOs, and KAr ages in the Machangqing porphyry indicates that the oreforming system cooled from about 800 ℃(zircon crystallization temperature) through 500 ℃(closure temperature for ReOs in molybdenite) to below 300 ℃(closure temperature for Ar in biotite) in a very short period. The duration of the Machangqing giant oreforming system is less than 2 Ma. The porphyry copper and molybdenum deposit of JinshajiangAilaoshan mineralization belt was the product of the synmineralization, and the mineralization time limit focused on 4035 Ma.

Key words: Western Yunnan, Machangqing CuMoAu deposits, Cenozoic porphyry rich in alkali, age of magmatic intrusion, age of mineralization