REMOTE SENSING AND MINERAL PROSPECTIVITY ANALYSIS OF LI-BEARING PEGMATITES AT EWOYAA, SOUTHERN GHANA

As the global shift towards cleaner energy sources accelerates, the demand for lithium for rechargeable batteries—essential for electric vehicles, laptops, and mobile phones—continues to rise. The Ewoyaa lithium mine in Ghana, West Africa, with ore reserves of 25.6 million tons and a projected operational lifespan of 12.5 years, is set to begin production in the second quarter of 2025. This mining site lies within the Cape Coast Basin, a Proterozoic volcano-sedimentary basin, part of the Early Proterozoic Birimian Supergroup. The region features several granitoid intrusions, consisting of tonalite to peraluminous granite, intruding the metasediments. It also hosts subvertical pegmatite dikes with mineralized units ranging from 30 to 100 meters in thickness.

This study leverages remote sensing data from ASTER, Landsat OLI, Sentinel-2, and Worldview-3 to evaluate their effectiveness in mapping the mineralized pegmatites and associated hydrothermal alteration zones. Techniques employed include RGB combinations, band ratioing, Principal Component Analysis (PCA), and linear spectral unmixing. Additionally, airborne magnetic and radiometric datasets are analyzed using upward continuation, phase match filtering and derivative analyzes to interpret the geology and geological structural patterns contributing to the identification of potential mineralized zones.

The magnetic data shows a low magnetic response in the area of interest, which is likely due to hydrothermal alteration or non-magnetic pegmatites. In contrast, the radiometric K/Th ratio shows moderate to high values, suggesting potassic alteration, which is typically associated with pegmatite formation and lithium mineralization. These anomalies point to the presence of possible structural controls, which could guide future investigations for lithium-bearing pegmatites.