Abstract: Metasilicic acid mineral water is a major functional drinking water resource with substantial health benefits. This study unveils the spatial distribution patterns and formation mechanisms of metasilicic acid groundwater hosted within granite, slate, and unconsolidated sedimentary aquifers in Pingjiang, Hunan Province, using hydrogeochemical and multi-isotope tracing methods. Results show that 43 % of granite fissure water, slate fissure water, and Quaternary pore water in the study area contain metasilicic acid contents that satisfy the standard of metasilicic acid mineral water. Among them, granite fissure water contains the highest metasilicic acid content, demonstrating its potential as a candidate for exploiting metasilicic acid mineral water. The metasilicic acid groundwater primarily receives recharge from atmospheric precipitation and belongs to the low-TDS (Total Dissolved Solids) HCO₃-Ca(Mg) type. The metasilicic acid mainly originates from the hydrolysis of silicate minerals (e.g., plagioclase) within a carbonate medium. Soil CO₂ and intense cation exchange serve as the primary drivers of dissolution. This study provides theoretical references for the exploration, development, and utilization of metasilicate acid mineral water resources within the same type of water-bearing rock group.