Tectonic lineament mapping and identification of copper alteration minerals using PRISMA and Sentinel-2A satellite imagery in Alma inlier and Fouanou syncline (western Anti-Atlas, Morocco)

Abstract

The western Anti-Atlas of Morocco hosts complex copper deposits with debated origins and multiple proposed geodynamic models. This study, applied for the first time to the Alma inlier and the Fouanou syncline, integrates PRecursore IperSpettrale della Missione Applicativa (PRISMA) imagery with Sentinel-2A multispectral data to accurately identify copper-related alteration minerals and map structural lineaments with high spatial and spectral precision. A series of image processing techniques were applied to the PRISMA dataset, including Minimum Noise Fraction (MNF), Pixel Purity Index (PPI), n-Dimensional Visualizer, and Spectral Angle Mapper (SAM), to isolate and identify minerals associated with alteration. In parallel, structural lineaments were extracted from Sentinel-2A imagery using Principal Component Analysis (PCA) and directional filters, enabling the precise mapping of tectonic features. Field validation was carried out through three geological cross-sections within the study area, where alteration zones were verified using a handheld spectrometer. The spectral signatures obtained from PRISMA were then compared and validated against field measurements and the USGS spectral library to ensure mineralogical accuracy. The main alteration minerals identified include malachite, azurite, hematite, and goethite, indicative of oxidation and supergene enrichment. Structural analyses revealed NE-SW to ENE-WSW oriented lineaments, consistent with Pan-African tectonic structures. The spatial correlation between alteration halos and major fault zones suggests that hydrothermal fluid circulation played a significant role in ore deposition, especially along the contact between the Precambrian basement and the overlying Paleozoic cover. These observations demonstrate PRISMA's value for cost-effective copper exploration in remote and geologically complex areas. This integrative methodology provides not only a viable exploration strategy but also offers new insights into the metallogenic evolution of the western Anti-Atlas and contributes to the ongoing debate on its tectono-magmatic history, with implications for similar metallogenic provinces across the world.