Hydrothermal alteration and structural lineaments of the Cambrian Jbel Boho volcanic system (Bou Azzer inlier, Morocco) revealed by remote sensing: Implications for an atypical porphyry-style Cu system

This study examines hydrothermal alteration and related structural lineaments in the Jbel Boho volcanic complex, located in the southern part of the Bou Azzer inlier, central Anti-Atlas (Morocco). Emplaced during the Early Cambrian, this complex represents an alkaline magmatic system associated with an intracontinental extensional setting. ASTER satellite imagery was processed using Band Ratios, Selective Principal Component Analysis, Spectral Information Divergence, and Linear Spectral Unmixing. This approach successfully identified four hydrothermal alteration types: potassic, phyllic, argillic, and propylitic. Additionally, structural lineaments were extracted by applying directional convolution filters (0°, 45°, 90°, and 135°) to the first principal component (PC1) of the ASTER data, to map the structural framework of the system. Field validation, petrography, mineralogy, and comparison with existing geological maps yielded an overall classification accuracy of 80.6% and a Kappa coefficient of 0.7, demonstrating a high level of reliability for the remote sensing approach in this arid area. Argillic alteration is the most widespread, affecting the entire volcanic sequence. Phyllic and potassic alterations, on the other hand, are concentrated mainly within the kilometer-scale Cambrian syenitic intrusion located in the southern part of the volcanic edifice, which is interpreted as a probable heat source for hydrothermal fluids. Propylitic alteration predominantly occurs at the periphery of the volcano and adjacent carbonate formations. Based on fracturing-mineralization relationships, copper mineralization within the Jbel Boho complex is interpreted to be structurally controlled. It is hosted by carbonate-quartz-barite veins associated with microsyenite and trachybasalt dykes, as well as by trachytic lava flows. The development of a dense fracture network, related to regional extensional tectonics and the emplacement of the syenite intrusion, likely facilitated the circulation of hydrothermal fluids and the emplacement of late-stage dykes. Altogether, these features suggest that the Jbel Boho complex may represent an atypical porphyry-style copper system, although additional geochemical investigations are required to better constrain its metallogenic significance.