Preserved hydrothermal metal zoning in a deformed Besshi-type VMS system: Mineralogical and predictive evidence from the Hawiah deposit, Arabian Shield

Abstract Ancient volcanogenic massive sulfide (VMS) deposits commonly undergo deformation, metamorphism and fluid-assisted recrystallization that obscure primary hydrothermal architecture and complicate exploration. We separate preserved metal zonation from deformation-related redistribution in fresh massive sulfide at the Hawiah Besshi-type VMS deposit, Arabian Shield, by integrating ore microscopy, electron-microprobe analysis (EPMA), whole-rock geochemistry, block-model grades, and Random Forest regression. Relict framboidal pyrite (Py1) records an early texture, whereas recrystallized pyrite (Py2) and fracture-controlled Cu-Zn ± Pb sulfides document post-ore modification. Interstitial and fracture-hosted chalcopyrite indicates local Cu redistribution, yet a deposit-scale gradient persists: Cu and Co decrease northward, whereas Zn, Cd, Pb and As increase. Sphalerite Fe contents (9.8–14.3 mol% FeS) give apparent Fe-Zn temperatures of ~ 311–355°C, reflecting re-equilibration of recrystallized ore, not depositional conditions. Random Forest models trained on southern-zone data reproduce Zn in the northern and central zones (R² = 0.902 and 0.697), reflecting persistent Zn-Cd covariance, although high values are underpredicted. EPMA shows near-detection-limit Au in pyrite and pyrrhotite, and the company’s SEM studies report native gold, electrum, and sylvanite (< 5-~20 µm), some within or associated with pyrite. Deformation can thus modify Cu distribution without erasing hydrothermal zoning in deformed VMS deposits, a framework seems applicable to deformed VMS systems globally.