Rb-Sr ISOCHRON AGE OF FLUID INCLUSIONS IN THE QUARTZ OF XUJIACUN GOLD DEPOSIT, HEILONGJIANG PROVINCE

The Xujiacun gold deposit is located in the southwest of Jiamusi block, with the orebody occurred in the Late Permian monzogranite. The metallogenic age is obtained and the ore-forming fluid source and its genetic relation with the host granite are discussed through the determination of Rb-Sr isotope age and H and O isotopes of fluid inclusions in the quartz of gold veins. The results show that the Rb-Sr isochron age is 229±8.6 Ma, slightly later or close to the formation time of ore-bearing rock mass (254.2±0.95 Ma, 230.44±0.54 Ma). The H and O isotopic characteristics of quartz indicate that the ore-forming fluid was the hydrothermal solution differentiated from the Late Permian granitic magma, with a small amount of atmospheric precipitation added later, suggesting that there is a close genetic relation between the ore-bearing quartz vein and the host granite. From the above, it is believed that the diagenesis and mineralization may occur in the same geological event, both related to the subduction of Paleo-Asian Ocean Plate into the Jiamusi-Mongolia block.