GRSG Conference 2022: Orbit to Outcrop

Title: ASTER spectral band ratios for mineral exploration: Implications for exploration targeting in south Saghro inlier (Eastern Anti-Atlas, Morocco)

Author: Mehdi Ousbih


Located in south Saghro inlier, the area covered by this study includes the 1:50 000 Imi n’Ouzrou and its adjacent Tachakoucht Sheets. Geologically, rocks are mostly magmatic and sedimentary, ranging from Neoproterozoic to Recent in age. More than one hundred twenty mineral occurrences have been recorded in the area, including Au, Ag, Cu, Pb, Mo, Zn, Hg, Mn, U, and Ba which seem to be dominantly structurally controlled and mostly associated with the circulation of hydrothermal fluids in Neoproterozoïc rocks. Since the area is still poorly explored, the great majority of these occurrences are of little economic significance but nevertheless, sizeable deposits of silver and asbestos have been exploited and other Mo, Cu, and Pb have also been produced on a small scale.

In this study, we focus on the effectiveness of ASTER spectral band ratios for identifying alteration zones hosting Au-Ag-Cu-Mo-Pb-Zn mineralization and assess implications for mineral exploration targeting in the north Siroua massif. For this, we have used ASTER data for mapping hydrothermal alteration minerals and to better discriminate geological and structural features associated with different minerals. The image transformation techniques like specialized band ratioing and Principal Component Analysis (PCA) were used to delineate lithological units and alteration minerals.

The supervised classification techniques, namely, Spectral Angle Mapper (SAM) and Spectral Information Divergence (SID) were applied to detect subtle differences between indicator alteration minerals associated with ground-truth minerals locations. The directional filtering technique is applied to help in tracing along the strike of the different linear structures. Results demonstrate that the integration of image transformation techniques and supervised classification of ASTER data with fieldwork and geochemical exploration studies has great efficiency in targeting new prospects of mineralization in the study area. The approach used in this research provides a fast, cost-efficient means to start comprehensive geological and geochemical exploration programs in the study area and elsewhere in similar regions.