Аңдатпа
Multispectral satellite imagery is a very useful technique to identify altered wall rocks around orogenic gold systems. In this study in the Akzhal–Vasilyevskoye district, Kazakhstan, we show that a geology-based ASTER band-ratio workflow is a useful technique to trace metasomatic footprints of mineralization. In the West Kalba camp, beresite and listvenite both produce usable ASTER SWIR signals, while pyrite and arsenopyrite are largely featureless at multispectral resolution. Five ratios on AST_07XT surface-reflectance data, screened with upper-tail anomaly masks, have enabled identification of sericitic cores, chloritic and carbonate halos, ferric caps, and zones containing mixtures of ferrous phyllosilicates. We show that district-scale Al–OH sericitic anomalies occur within Mg–OH and carbonate shells. At Vasilyevskoye the pattern is due to beresite nuclei within listvenite rims, while at Tokum the sericitic centres remain compact within wider Mg–OH and carbonate halos. Mean polygon spectra differ between the two footprints across Bands B4–B6 and across the SWIR tail (B7–B9). SEM–EDS at Vasilyevskoye links the mapped anomalies to chlorite, sericite, and carbonate gangue assemblages with sulfide-bearing volumes. The data also allow identification of subordinate REE, phosphate, and Ti enrichment within carbonaceous and polymineralic host lithologies.