Prospectivity Mapping for Epithermal Deposits of Western Milos Using a Fuzzy Multi Criteria Evaluation Approach Parameterized by Airborne Hyperspectral Remote Sensing Data

Abstract

A Mineral prospectivity mapping (MPM) approach using a GIS-based weighted linear combination implementation of a Multi-Criteria Evaluation approach utilising a fuzzy Analytical Hierarchy Process to elucidate expert knowledge has been implemented to analyse the spatial distribution of epithermal deposits on the Island of Milos, Greece and model their association with exploration evidence data with the aim of providing insights into the controls on ore deposition. An integrated field and Digital Airborne Imaging Spectrometer (DAIS) hyperspectral and thermal multispectral airborne remote sensing dataset supported by field mapping and laboratory analyses, has been utilised to resolve hydrothermal alteration and parameterise the MPM. This study has highlighted the intimate spatial relationship between topographic highs and locations with high grade silicified alteration at a number of locations. The ability of high spatial resolution multispectral Thermal InfraRed (TIR) remote sensing imagery, integrated with topographic data, to resolve these silicified topographic highs provides an additional tool in the exploration of epithermal deposits. The spatial relationships between silicified lithocaps, high-grade altered rocks, faulting and topographic highs were utilised in the development of the MPM model. A close association between the modelled results and the hydrothermal alteration mapped in the field supports the accuracy of this MPM approach.

Raman Spectroscopy Coupled with Reflectance Spectroscopy as a Tool for the Characterization of Key Hydrothermal Alteration Minerals in Epithermal Au–Ag Systems: Utility and Implications for Mineral Exploration

“…Mineralogical and geochemical characterization of phyllosilicates is crucial in hydrothermal ore deposits research and exploration, since they provide insight into the hydrothermal environment, ore-forming processes, and the timing of ore deposition within a multi-stage system. 11,73 Field-portable shortwave infrared spectroscopy is currently widely deployed in the mineral exploration industry to map hydrothermal alteration assemblages at the regional-to-deposit scale in a broad range of mineral deposits, including porphyry deposits, 74 epithermal deposits, 18,75 iron oxide copper-gold (IOCG) deposits, 76 skarn deposits, 77 . Also shown are the data for clinochlore from the Crestmore Quarry (RRUFF ID: R060725), clinochlore from the Callaghan Creek (RRUFF ID: R061080), and chamosite from Slesse Creek (RRUFF ID: R060188) from the RRUFF database.…”

“…Mineralogical and geochemical characterization of phyllosilicates is crucial in hydrothermal ore deposits research and exploration, since they provide insight into the hydrothermal environment, ore-forming processes, and the timing of ore deposition within a multi-stage system. 11,73 Field-portable shortwave infrared spectroscopy is currently widely deployed in the mineral exploration industry to map hydrothermal alteration assemblages at the regional-to-deposit scale in a broad range of mineral deposits, including porphyry deposits, 74 epithermal deposits, 18,75 iron oxide copper-gold (IOCG) deposits, 76 skarn deposits, 77 44 and volcanic-hosted massive sulfide deposits. 78�82 However, there are some important limitations to this technique: (i) the identification of a mineral phase depends on its ability to produce a measurable reflectance signal, (ii) sparse hydrothermal alteration can sometimes remain undetected or unquantified, (iii) minerals producing stronger reflectance signals, and the presence of multiple minerals with strong reflectance, can mask weaker signals from more diagnostic alteration phases, (iv) many specific absorption bands (e.g., OH band at �1400 nm, Al-OH band at �2200 nm) are common to a wide range of phyllosilicates, and (v) macroscale spectroscopy cannot discriminate minerals formed by successive hydrothermal events that affected an individual sample.…”