Integrated hyperspectral-multispectral mapping of shear-associated hydrothermal alteration and gold mineralization validated by geochemical and isotopic data, southern Arabian Shield.

内容摘要

Shear-zone-hosted gold systems are widespread in the southern Arabian Shield, yet the geometric and genetic links between deformation architecture, hydrothermal alteration, and ore-forming fluids remain insufficiently constrained at the scale of individual structural corridors. This study integrates PRISMA, ASTER, and Sentinel-2 remote sensing data with structural analysis, petrography, whole-rock geochemistry, fire assay, and C-O stable isotope data to develop a deformation-controlled mineralization model for the Wadi Al Awja district, Asir terrane. Selective PCA and MNF transformations of PRISMA data delineate narrow and laterally continuous carbonate-silicification alteration belts aligned with N-S to NNE-SSW high-strain zones, providing markedly improved resolution over multispectral datasets. The mapped alteration belts spatially coincide with fold-closure domains and a central shear corridor defined by dense foliation trajectories and reactivated ductile-brittle structures. Fire assay data demonstrate that gold enrichment (locally reaching several ppm Au) is confined to ductilely deformed quartz-carbonate and carbonate-silicified zones within these high-strain domains, whereas weakly altered and late stage brittle silicified rocks are consistently barren. Petrographic observations of ribbon quartz, boudinaged quartz-carbonate veins, and mylonitic fabrics corroborate syn-deformational fluid flow and structurally focused permeability enhancement, emphasizing the primacy of progressive deformation in localizing mineralization. Carbonate δ13C values (- 6.7‰ to + 4.2‰ VPDB) are compatible with CO2-rich fluids of dominantly metamorphic affinity at estimated temperatures of ~ 250-300 °C, consistent with the quartz-carbonate-chlorite ± sulfide assemblage. The wide δ18O range (- 18.6‰ to + 2.1‰ VPDB) records variable fluid-rock interaction and progressive isotopic re-equilibration during episodic fluid infiltration along long-lived Neoproterozoic shear zones. The integrated structural, spectral, geochemical, and isotopic constraints support an epigenetic, shear-zone-hosted gold model in which brittle-ductile reactivation generated transient permeability, focused CO2-rich fluids, and incremental gold deposition. The integrated structural, spectral, geochemical, and isotopic constraints support an epigenetic, shear-zone-hosted gold model in which brittle-ductile reactivation generated transient permeability, focused CO2-rich fluids, and incremental gold deposition. The results demonstrate that carbonate-silicification alteration is a reliable exploration proxy particularly when confined to high-strain structural corridors.