Objective The fluorite deposit exists in the clastic rocks of the Lower Cambrian Qiongzhusi Formation in the Anzhaiping area of Leibo County, southwest Sichuan Province. The mineralization of fluorite is controlled by the Ebian−Jinyang Fault, which is in the near north−south trend, and occurs in the structural fissure in the form of veins. The fluorite mineralization process in this area lacks effective constraints, hindering the understanding of its genetic mechanism and exploration progress.

Methods This study investigates the fluid properties, mineralization process, and genetic model of the fluorite deposit through rare earth element (REE) geochemistry and fluid inclusion analysis of fluorite separates from typical ores.

Results The fluorite exhibits generally low total REE concentrations, with REE patterns showing slight right inclination, middle REE enrichment, and convex shapes. Strong positive Eu anomalies (mean δEu=1.77) and weak negative Ce anomalies (mean δCe=0.83) are common. Combined with Tb/Ca–Tb/La and Y/Ho–La/Ho diagrams, the results indicate a hydrothermal origin for the fluorite mineralization, classifying the deposit as a brine−type formed in a high−oxygen fugacity open system. Fluid inclusions are predominantly liquid−rich two−phase types, with homogenization temperatures ranging from 81°C to 209°C and salinities from 2.1% to 21.4% NaCleqv, suggesting a medium–low temperature, low−salinity NaCl–H₂O fluid system. Water–rock interaction between the ore−forming fluids and wall rocks primarily facilitated the enrichment of F and Ca, while fluorite precipitation was mainly triggered by fluid mixing between deep brine and meteoric water, accompanied by fluid cooling.

Conclusions Basin−derived hot brines and meteoric water leached ore−forming elements such as Ca and F from the strata, enriching them in the hydrothermal fluid. Driven by tectonic forces and formation pressure gradients, the fluid migrated upward along the fault zone into favorable hosting fractures. Confined by fine−grained clastic rocks acting as a seal, changes in physicochemical conditions led to the precipitation and enrichment of fluorite, forming vein−type deposits classified as medium–low temperature hydrothermal fissure−filling fluorite ores. This study provides a theoretical basis for future resource potential assessment and scientific exploration of fluorite deposits in southwestern Sichuan.