Hydrothermal alteration mapping using Landsat-8 OLI: Igoudrane region, Imiter inlier, Jbel Saghro, Anti-Atlas, Morocco

Abstract

The Anti Atlas is the largest structural domain in southern Morocco, and the Igoudrane pluton outcrops at the base of the same-named high volcanic massif, to the east of the Imiter mine. The research region is close to the Imiter mine, a huge underground and open-pit mine located in the northern section of Jbel Saghro's Precambrian basement. It is distinguished by a hydrothermal Ag-Hg deposit linked to an eastwest fault and the deposition of Late Neoproterozoic (550  3Ma) rhyolitic rocks. By using the Landsat-8 OLI sensor, this study intends to map the hydrothermal alteration in the Igoudrane region, Imiter inlier, Jbel Saghro, eastern Anti-Atlas, Morocco. It comprises nine spectral bands (bands 1–7) plus a panchromatic band (15 m) with a spatial resolution of 30 m. Furthermore, Landsat-8 OLI band ratios highlighted areas with ferrous iron using [(B7/B5) + (B3/B4)] BR, the simple ratio MIR-Red Eisenhydroxid index with B7/B4, ferric oxides (B6/B5), the simple ratio red/blue iron oxide B4/B2, and alteration/laterite (B6/B7). In addition, the band ratios applied were classified and revealed the presence of ferrous iron, hydroxides, ferric oxides, iron oxide, and alteration/laterite. As the results show, we notice particularly the presence of ferric oxides within granitoids (granites, tonalites, diorites, monzonites). Overall, the approaches used produced excellent results for mapping alteration zones in similar dry regions.