Abstract:
Fluorite is an indispensable raw material in strategic emerging industries such as new energy and new materials. In recent years, significant breakthroughs have been achieved in fluorite exploration in the Altyn Tagh orogenic belt, with the discovery of world-class deposits such as Kaerqiaer, Piyazidaban, and Gajike. However, the nature of the ore-forming fluids and the genetic types of these deposits remain unclear. This study focuses on the Gajike fluorite deposit in the central and southern parts of the Altyn Tagh, conducting detailed geochemical research on trace elements in fluorite from different stages based on thorough geological characterization. The results indicate that fluorite from all stages is enriched in light rare earth elements, with rare earth element patterns showing a "right-leaning" type, and mineralization occurring during early hydrothermal activity. The Tb/La-Tb/Ca diagram suggests that fluorite is of hydrothermal origin, with hydrothermal fluids undergoing water-rock reaction with the surrounding rocks. The La/Ho-Y/Ho diagram reveals strong fractionation of Y and Ho, indicating that the fluorite exhibits homologous multi-stage characteristics, where early fluorite breccia underwent recrystallization while middle-stage fluorite cement precipitated during fluid migration. The δCe-δEu diagram shows strong negative Eu anomalies and positive Ce anomalies in fluorite, reflecting a medium-low temperature reduction environment with low oxygen fugacity and water-rock reaction effects. The high F content in the rock mass and the Ca-rich strata suggest that the F in fluorite originates from K-feldspar granite, while Ca comes from metamorphic strata and marble. Comprehensive analysis concludes that the Gajike fluorite deposit formed in a medium-low temperature reduction environment, and its genetic type is classified as a medium-low temperature hydrothermal deposit.