Evaluating multi-resolution remote sensing data - A knowledge-driven approach to geological remote sensing in a high-sulphidation epithermal system
Bruno Virgilio Portela is a PhD student in theDepartment of Applied Earth Sciences. (Co)Promotors are prof.dr. M. van der Meijde, dr. H.M.A. van der Werff and dr. C.A. Hecker from the faculty of Geo-Information Science and Earth Observation (ITC), University of Twente.
Geologists use remote sensing to characterise mineral systems using datasets with varying spatial and spectral resolutions and wavelength ranges. These choices control exploration cost, accuracy and the time required to define targets. Nevertheless, most comparisons are sensor-based, so the standalone value of a given resolution and the benefit or redundancy of combining resolutions remains unclear. This thesis adopts a resolution-first, knowledge-based characterisation of a high-sulphidation epithermal system using co-registered laboratory, airborne and spaceborne data across the VNIR, SWIR and LWIR wavelength ranges within a single geological setting. Separate SWIR and LWIR workflows generate directly comparable products (band ratios, spectral indices, and wavelength maps) that target physics-based parameters: absorption features and emissivity minima. Because these parameters are not scene-dependent, the products can be produced consistently across resolutions, enabling direct comparisons. The study evaluates four geological products derived from geological remote sensing, directly or indirectly: hydrothermal alteration mineralogy, rock-forming mineralogy, fluid composition, and fluid emplacement. Laboratory SWIR data resolve alteration mineral species, textural patterns and subtle wavelength shifts indicative of mineral intergrowth, providing a reference for validating coarser-scale interpretations. Laboratory LWIR data constrain quartz and other rock-forming minerals, separate minerals with overlapping spectral absorption features, and, where spectra allow, distinguish kaolin-group subtypes. Airborne hyperspectral SWIR maps deposit-scale alteration zoning from advanced argillic to sericitic domains, resolve alunite versus pyrophyllite distributions, and map white mica compositional trends used as pH proxies. Airborne hyperspectral LWIR maps quartz and other rock-forming minerals, separates alunite from pyrophyllite, and delineates kaolin-group distributions that trace neutralisation fronts, supporting reconstruction of fluid chemistry. Spaceborne hyperspectral SWIR reproduces the main airborne alteration patterns at 60 m pixels when targets approach or exceed the pixel size. At the same time, multispectral VNIR-SWIR-LWIR products provide cross-range continuity for regional-to-district screening and improved separation, where band placement mitigates overlap. For early-stage exploration, this thesis defines an evidence-based survey design that benchmarks the capabilities, limits, and synergies of spatial and spectral resolutions across wavelength ranges for characterising high-sulphidation epithermal systems.
