Geochemistry, inclusions, isotope geochemistry, and isotope chronology of the Baihua’ao fluorite deposit in central Hunan Province: constraints on the timing and process of mineralization

• Mineralization time and Tectonic setting. • The fluid characteristics of fluorite deposits. • The source of materials for the fluorite deposit. • The mineralization model of fluorite deposits. The Baihua’ao fluorite deposit is a typical fluorite deposit closely related to granite in central Hunan Province. In order to clarify its mineralization age and process, this paper conducted research on whole rock geochemistry, fluid inclusions, H-O isotopes, and Sm-Nd, Rb-Sr, and U-Pb isotope geochronology. The zircon U-Pb isotope geochronology and SiO 2 -K 2 O, A/CNK-A/NK, (K 2 O + Na 2 O)/CaO-10000 × Ga/Al, TFeO/MgO-10000 × Ga/Al, Y-Nb-Ce, and Y-Nb-3 Ga diagrams of granite indicate that the granite is a high-potassium peraluminous A-type granite, formed at 213.6 Ma (Late Triassic), and belongs to the post-orogenic tectonic setting related to the Indosinian movement. The fluid inclusions and H-O isotopes of fluorite indicate that the ore-forming fluid is mainly atmospheric precipitation. The Rb-Sr and Sm-Nd isotope geochronology and rare earth element studies of fluorite show that the mineralization age of fluorite is 145.7–147.6 Ma, with green and purple fluorite formed during the early mineralization period and white fluorite formed during the late mineralization period. The Sm/Nd ratio and (La + Y)-(Y/La) diagram of fluorite indicate that the ore-forming material is closely related to the surrounding rock. The Tb/Ca-Tb/La diagram and inclusion characteristics of fluorite indicate that water–rock interaction is the main mineralization mechanism, followed by a decrease in fluid temperature.