Integrated Satellite and Drone-Based Remote Sensing for Mapping Porphyry and Epithermal Deposits in the Panagyurishte Ore District, Bulgaria

Rapid, scalable methodologies are critical for the early-stage exploration of porphyry Cu and epithermal Au systems in data-poor regions. This study presents a novel multi-sensor workflow that effectively bridges the scale gap between regional reconnaissance and prospect-scale targeting in Bulgaria's Panagyurishte ore district. The workflow integrates ASTER and WorldView-3 satellite data with drone-assisted VNIR, SWIR and TIR surveys, validated by field-based mineralogical and geochemical analysis. Applying Mineral Index and Target Detection with Spectral Angle Mapper techniques to ASTER imagery delineates regional-scale hydrothermal alteration patterns, including Mg/Fe oxide, Al-OH-bearing and propylitic assemblages. The higher spatial resolution and expanded SWIR coverage of WorldView-3 data enhance the discrimination of advanced argillic, phyllic and propylitic domains alongside their structural controls. Crucially, drone-based surveys deliver centimeter-scale resolution, permitting the detailed mapping of alteration zonation and fault architecture that satellite imagery cannot resolve. Validation via SWIR spectroscopy, portable X-ray fluorescence and X-ray diffraction confirms a strong correlation between remotely sensed spectral responses and ground-truth mineralogy. Case studies from the Tsar Asen porphyry Cu deposit and the Pesovets and Krasen epithermal systems illustrate the workflow's effectiveness for alteration mapping, geochemical vectoring and exploration targeting. The findings confirm that drone data are critical for resolving structural controls on high-sulphidation epithermal systems, a feature not discernible from satellite data alone. This combined satellite-drone-field approach offers a robust, transferable framework capable of bridging regional reconnaissance with deposit-scale investigation.