Skarn W mineralization using magnetic susceptibility and garnet spectral characteristics in the Fujiashan W deposit, eastern China

Highlights • Magnetic susceptibility exhibits a systematic distal-to-proximal increase and correlates positively with WO3 grade, reflecting magnetite enrichment during skarn metasomatism. • Garnet thermal infrared spectral parameters (Pos11500, Pos11800, Pos12100, Pos12300) display consistent long-wave shifts in ore-bearing zones, closely linked to W enrichment. • Full width at half maximum of the Pos12300 absorption peak (<150 nm) effectively discriminates deep, high-temperature mineralized skarn from shallow, low-grade zones. • Integration of magnetic susceptibility and garnet spectral criteria defines a robust, non-destructive framework for vectoring concealed W mineralization in skarn systems. Skarn deposits typically exhibit distinct zonation of mineral assemblages, which serves as a vectoring tool for mineral exploration. Magnetic susceptibility and hyperspectral characteristics have been widely applied to delineate hydrothermal centers in porphyry Cu deposit, yet application to skarn systems remains comparatively underexplored. This study carried out magnetic susceptibility measurements along a representative profile of the Fujiashan W skarn deposit in the Edong ore district, coupled with thermal infrared spectral analyses of garnet. Magnetic susceptibility displays a positive correlation with proximity to mineralized skarn, indicating progressive enrichment of magnetite toward mineralized centers. Values exceeding 2 × 10 −3 SI are identified as potential vectors for tungsten mineral exploration in W skarn deposit. Garnet from skarn zones at varying distances from the intrusive contact at Fujiashan display progressive shifts in the wavelengths of thermal infrared absorption features, specifically at Pos11800, Pos12100, and Pos12300, toward shorter wavelengths. Based on observed correlations with W grade, diagnostic spectral thresholds indicative of W mineralization are defined as follows: Pos11500 > 11450 nm, Pos11800 > 11850 nm, Pos12100 > 12050 nm, and Pos12300 > 12200 nm. Furthermore, the spectral position of the Pos12300 feature in garnet is sensitive to temperature and the relative concentrations of Al 3+ and Fe 3+ . A full width at half maximum (FWHM) of less than 150 nm at Pos12300 is proposed as an indicator of proximity to the hydrothermal center. An integrated exploration model containing magnetic susceptibility with garnet spectral variations is established for the Fujiashan W skarn deposit. Combined magnetic susceptibility and spectral data significantly improve W targeting accuracy and establish a practical framework for exploration in analogous W skarn systems.