Abstract:

The Tongkuangli molybdenum polymetallic deposit in Qingyang area, Anhui Province is a skarn type Mo polymetallic deposit newly discovered in the Middle-Lower Yangtze River metallogenic belt in recent years. In this paper, the geological characteristics and fluid inclusion characteristics of the deposit are studied in detail, and the origin and evolution of fluids are discussed. Based on the cross-cutting relationship and mineral metasomatism, the mineralization process of the Tongkuangli deposit can be divided into five stages: early skarn, late skarn, quartz molybdenite, quartz polymetallic sulfide and carbonate stages. Microscopic observations show that the types of fluid inclusions in the Tongkuangli deposit are mainly liquid-rich, vapor-rich and daughter-bearing three-phase inclusions. Microthermometric results show that the early ore-forming fluids were high temperature, and medium to high salinity fluids, while the late ore-forming fluids were low temperature and low salinity fluids. This feature, combined with the existing hydrogen and oxygen isotope data, indicates that the early hydrothermal fluids in the Tongkuangli deposit were magmatic water, and that the magmatic water mixed with circulating meteoric water during the late stages. The coexistence of liquid-rich, three-phase and vapor-rich inclusions within quartz of the quartz molybdenite stage, and their similar homogenization temperatures with completely different homogenization way, indicating that fluid boiling may be the main mechanism of molybdenum precipitation in the Tongkuangli deposit.

Key words: skarn molybdenum polymetallic deposit, deposit geology, fluid inclusion, microthermometry, Tongkuangli in Qingyang area, Anhui