Landsat 8 ile Hidrotermal Alterasyon Haritası: Ruanda'nın Gatumba Pegmatit Kuşağı'ndan Bir Vaka Çalışması (Case Study) Mapping Hydrothermal Alteration with Landsat 8: A Case Study from Rwanda's Gatumba Pegmatite Belt Moses Twizeyimana Exploration Geologist | GIS, Remote Sensing, and ESG analysis for mineral exploration amp; environmental compliance November 1, 2026 Summary I screened the Ngororero–Gatumba district using three Landsat 8 spectral ratios, retaining pixels that exceeded the anomaly threshold for all three. The result is a first-pass screening layer for prioritising field investigation. It is not independent confirmation of alteration, and it is not a lithium prospectivity map. The distinction matters. Two of the ratios share the same spectral band, the thresholds are statistical rather than geological, and the spectral responses are not mineral-specific. This article presents the geological context, processing approach and results. Part 2 examines the methodolo...