Zircon U-Pb geochronology of ore-bearing porphyries in Baomai deposit, Yulong Copper Belt, Tibet

Baomai porphyry copper-molybdenite deposit is an important part of the northern Yulong copper belt, Tibet, with typical porphyry-type mineralization and alteration. The latest exploration shows that both Cu and Mo resources have reached the medium-sized deposit, but the research work is still very poor. Based on the basic geological characteristics, intrusion ages of biotite granite porphyry and biotit-monzogranite are 41.3 ± 0.2 Ma and 40.8 ± 0.2 Ma, respectively, according to the LA-ICP-MS zircon U-Pb geochronology method. These results are consistent with those of Yulong and Zhanaga deposits. All of them are the products of continent collision orogeny of India with Eurasia in Eocene. Geochronology evidences show that porphyries related to mineralization in the Yulong copper belt are mainly intruded at 37-42 Ma, and no obviously early (51 Ma), medium (41 Ma) and late (33 Ma) stages magmatic activities. From northwest to southeast, the ages of diagenesis and mineralization in Yulong copper belt do not change to be younger significantly.