Geochemical Characteristics of Inclusions of Quartz in the Dehelongwa Copper-Gold Deposit, Tongren, Qinghai Province

Dehelongwa copper-gold deposit is a typical porphyry-type copper-gold deposit in the west Qinling mineralization belt, occurring mainly in fracture zone. Studies on quartz fluid inclusions show three main types of inclusions, namely H₂O-rich, CO₂-rich and saline daughter mineral inclusions. Microthermometry data suggests that prior to mineralization, the inclusion is powerful intrusion magmatic fluid, rich in Na⁺, K⁺ and so on. In the metallogenic period, the inclusion is NaCl-unsaturated magmatic fluid of high temperature and high salinity, with a boiling feature. After mineralizaion, the inclusion is a H₂O-NaCl-KCl system with moderate temperature, medium-low salinity and low density. The study shows that the ore-forming of copper and gold is mainly caused by the changes in temperature, salinity and pressure, the open formation, the increasing oxygen fugacity, and the declining fluid pH value.