Genesis of Wushan Fluorite Deposit in Jinyun County, Zhejiang Province: Constraints from Fluorite Rare Earth Elements, Fluid Inclusions and Infrared Spectroscopy

The Wushan fluorite deposit is located at the northeast end of the Cathaysia Block, in the central part of the fluorite mining area in Zhejiang Province. The deposit is located in the contact zone between the Guantou Formation of the Cretaceous and the Yanshan granite. The distribution of the ore body is controlled by northwest trending faults, and banded fluorite is developed. Based on geological surveys, research was conducted on rare earth elements, fluid inclusions, and infrared spectra of fluorite with different colors. The research results indicate that the rare earth element content and mineralization temperature of fluorite with different colors shows regular changes. From green fluorite to purple fluorite and then to yellow fluorite, δEu increases, the ∑REE decreases, the LREE/HREE ratio increases and mineralization temperature decrease. Based on the geological characteristics of the deposit, this study suggests that the crystallization and mineralization process of the three colors of fluorite is a reducing environment with a large temperature range. The formation sequence of fluorite is that green fluorite is formed first, followed by purple fluorite, and yellow fluorite is formed latest. The Tb/Ca-Tb/La and La/Ho-Y/Ho diagrams and inclusion temperature measurements show that different colored fluorites in the area are formed from the same fluid source at different stages of the same mineralization period. The formation of banded fluorite is the result of periodic pulsation and upwelling of ore-forming hydrothermal fluids. Overall, the ore-forming fluid of the fluorite deposit in the study area belongs to medium low temperature, low salinity, and low-density F-containing hydrothermal fluids. In summary, the Wushan fluorite deposit belongs to the medium to low temperature hydrothermal fissure filling type fluorite deposit