Mineralization process of the Fengyan Zn-Pb skarn deposit in the Fujian Province, southeastern China: Insights from LA-ICP-MS analysis of fluid inclusion

The Zn-Pb skarn deposits are globally important sources of Zn and Pb resources. Numerous such deposits are developed in the central Fujian Region, southeastern China. To investigate the detailed ore-forming processes of these deposits, this study chooses the Fengyan Zn-Pb skarn deposit as a case study in the region. Leveraging the novel application of individual fluid inclusion LA-ICP-MS analysis to Zn-Pb skarns, this work constrains fluid source, evolution, and metal precipitation mechanisms by integrating data from petrography, microthermometry, and Raman spectroscopy. Analyses were performed on garnet, quartz, sphalerite, and calcite from various mineralization stages. The results show that the ore-forming fluids at Fengyan originated from a reduced, single-phase supercritical fluid that exsolved directly from magma. This fluid underwent a coherent evolution without significant phase separation across four mineralization stages, from a high-temperature, metal-rich prograde skarn stage, through a cooling retrograde skarn stage and a metal-precipitating quartz-sulfide stage, to a final low-temperature, element-depleted quartz-calcite stage, which defines a clear path of continuous cooling and compositional depletion. The large-scale Zn-Pb precipitation was driven collectively by the mixing of this fluid with meteoric water, cooling, and water–rock reaction, with no fluid boiling/immiscibility involved. Additionally, analyses of pre-ore fluids reveal low Cu and W concentrations, indicating limited economic potential for these metals at Fengyan. This research can provide robust evidence for understanding the mineralization processes of Zn-Pb deposits in the central Fujian Region and offers theoretical guidance for advancing mineral exploration.