ZIRCON U-Pb AGES OF DONGAN GOLD DEPOSIT IN HEILONGJIANG PROVINCE: Geological Implication

The age of the rhyolite porphyry, which is closely related to mineralization in Dongan gold deposit, is tested with LA-ICPMS zircon dating method. The results show that, the U contents of the rhyolite porphyry range from 269.1×10^-6 to 956.0×10^-6, while the Th contents, from 202.2×10^-6 to 1276.8×10^-6, with Th/U ratio between 0.43 and 1.80. The age of rhyolite porphyry is (109.6±1.7) Ma, which is synchronous with other epithermal gold deposits in the area. It implies the large-scale lithospheric extension and thinning in the late period of Early Cretaceous.