Thermal history of the giant Qulong Cu-Mo deposit, Gangdese metallogenic belt, Tibet: constraints on magmatic-hydrothermal evolution and exhumation

complete thermal history for the Qulong porphyry Cu-Mo deposit, Tibet is presented. Zircon U-Pb geochronology indicates that the mineralization at Qulong resulted from brecciation-veining events associated with the emplacement of a series of intermediate-felsic intrusions. Combined with previously published ages, our results reveal a whole intrusive history of the Qulong composite pluton. Causative porphyries were emplaced at similar to 16.0 Ma as revealed by Ar-40-Ar-39 dating of hydrothermal biotite (15.7 +/- 0.2 Ma) and sericite (15.7 +/- 02 Ma). Zircon and apatite (U-Th)/He (ZHe and AHe) dating of Qulong revealed that both followed similar, monotonic thermal trajectories from 900 degrees C (U-Pb ages: 17.5-15.9 Ma) to 200 degrees C (ZHe: 15.7-14.0 Ma), and that the causative porphyries experienced faster cooling at a maximum rate of greater than 200 degrees C/myr. The Qulong deposit was exhumed between 13.6 Ma and 12.4 Ma (AHe) at an estimated rate of 0.16-0.24 mm/y, which is consistent with previous estimates for other Gangdese Miocene porphyry deposits. Our AHe thermochronology results suggest that neither the Gangdese thrust system, nor the Yadong-Gulu graben affected or accelerated exhumation at the Qulong deposit