Volcanic-type beryllium (Be) mineralization along the southeast coast of China exhibits considerable metallogenic potential, yet the precipitation mechanisms of Be in volcanic-intrusive systems remain poorly constrained. Here, we present fluid inclusion and geochemical investigations of quartz and fluorite from Qingtian volcanic-intrusive Be deposit to constrain hydrothermal Be-mineralization processes. Be-bearing minerals include bertrandite, phenakite, and helvine and mainly occur as secondary phases within host-rock fractures and hydrothermal alteration zones in Shawan, Huangshanlong and Tuoliao ores, respectively. Petrographic observations reveal abundant primary two-phase (L + V) fluid inclusions in both quartz phenocrysts (Qz I) and late-stage quartz (Qz II), while triple-phase (S + L + V) inclusions containing solid phases (anhydrite, calcite, apatite) were found in fluorite. Fluid inclusion thermometry yields homogenization temperatures of 220–420 °C (Qz I), 220–360 °C (Qz II), and 160–300 °C (fluorite), with salinities of 0.1–5.4 wt% NaCl eqv., and phenakite crystallized at approximately 230 °C. These data indicate a moderate-low temperature and low-salinity hydrothermal system. LA-ICP-MS analytical results of individual fluid inclusions reveal different Be concentration during the hydrothermal alteration processes: none is detectable in fluid inclusions from Qz I, up to 169 ppm Be in Qz II (Huangshanlong ore), and as high as 1531 ppm Be in fluorite from Tuoliao ore, reflecting later hydrothermal Be mineralization and important role of F in hydrothermal Be concentration. Oxygen isotope compositions (δ 18 O = 0.7–11.2‰ for quartz, 5.0–6.4‰ for calcite) indicate mixing of magmatic and meteoric/groundwater component during cooling. The precipitation mechanism of Be in Qingtian Be deposit involves fluorination-driven Be solubility in late hydrothermal fluids, followed by Be mineralization during fluid mixing and cooling in the volcanic-intrusive hydrothermal system. This study reveals the enrichment, transport, and mineralization of Be in volcanic-intrusive system, and provides a critical framework for exploring similar deposits in southeastern China. • Homogenization temperatures and salinities of ore-forming fluids linked Be mineralization were revealed in the Qingtian Be ores • Chemical composition of individual fluid inclusions in quartz and fluorite indicated fluorine served as the crucial role during hydrothermal Be concentration • Trace element concentration ratios X/(Na+K) of fluid inclusions and δ 18 O values of quartz and calcite constraint on both fluid mixing and origin of Be • Reveal Be mineralization mechanism in the Qingtian volcanic-intrusive suite
Wang et al. (Fri,) studied this question.