Hyperspectral Drill Core Spectroscopy for Alteration Zoning in Orogenic Gold Deposits: Insights from the Liba Deposit, West Qinling, China

Orogenic gold deposits host a substantial proportion of global gold resources, yet their internal alteration architecture and mineral assemblage variability are commonly reconstructed from random samples, limiting our ability to resolve along-profile zonation and its linkage to gold enrichment. Here we evaluate hyperspectral drill-core spectroscopy, integrated with surface spectroscopy and petrographic validation, as a rapid and spatially continuous approach to delineate alteration zoning in the Liba orogenic gold deposit (West Qinling Orogen, China). We acquired hyperspectral spectra (0.35–2.50 μm) from 255 evenly spaced surface points across two orebodies and from nine representative drill cores scanned at 1 m intervals, and organized the spectral dataset according to Au-grade domains (0.5 g/t). Spectra were quality controlled and interpreted using ENVI-based spectral library matching and The Spectral Geologist (TSG) processing workflows. Petrographic observations from 76 polished thin sections provide independent mineralogical constraints. The hyperspectral results resolve a systematic alteration progression from barren chlorite-dominated assemblages (Au-grade < 0.05 g/t) (locally with minor carbonate) through a weakly mineralized transition (Au-grade 0.05–0.5 g/t) characterized by diminishing chlorite and emergent kaolinite–carbonate with intensified sericitization, to an ore-grade (Au-grade > 0.5 g/t) assemblage dominated by kaolinite–sericite–carbonate–pyrite where biotite persists in distal and proximal zones but was progressively replaced by chlorite during subsequent hydrothermal stages; its modal abundance exhibits a clear inverse correlation with mineralization intensity. These results demonstrate that hyperspectral core scanning, coupled with targeted validation, can rapidly reconstruct a three-dimensional alteration architecture and provide practical mineralogical vectors for exploration targeting and process-oriented studies in orogenic gold systems.