Integrating geochemical insights and remote sensing for enhanced identification of hydrothermal alterations in the Igoudrane region, Anti-Atlas, Morocco

Abstract

The Moroccan Anti-Atlas is distinguished for its significant mining potential. The Igoudrane region, which is the focus of this study, is located within the Imiter inlier, one of the notable inliers of the eastern Anti-Atlas. The current study aims to evaluate the mineralogical and geochemical composition of the rocks in the Igoudrane area using the ICP-MS with 4 acids, besides identifying the hydrothermal alteration indexes using major elements provided by the geochemical data, and remote sensing techniques. The study was accomplished using the thin sections for mineralogical description, as well as the ICP-MS with 4 acids, which provides data on major, trace, and rare earth elements. The alteration indexes employed were the Ishikawa alteration index (AI), the Chlorite Saturation Index (CSI), the Sericite Saturation Index (SSI) and the Alteration Intensity coefficient (AIC). These indexes were complemented by a chloritization and sericitization mapping using the SWIR-VNIR data of ASTER. We employed the band ratios of chlorite [(B6 + B9)/(B7 + B8)] and sericite [(B5 + B7)/B6], achieving an accuracy of 80.95% for sericite and approximately 85.71% for chlorite. The mineralogical and geochemical study revealed the presence of granodiorites, granites, monzonites, monzo-diorites, diorites, gabbro, and gabbro-diorites, andesites, rhyolites, and trachydacites. These rocks belong to a highly potassic calc-alkaline and peraluminous series, which are fairly typical of granitoids of mixed origin. The plutonic rocks of Igoudrane were formed across diverse geodynamic contexts, ranging from pre-plate to post-collisional settings, and the volcanic rocks were emplaced in geodynamic settings, which are island arcs or active continental margins. The quasi-positive correlation observed in the Al vs. CSI and SSI diagrams reveals that higher aluminum content is linked to increased chloritization and sericitization intensities. Furthermore, The AIC values of the Igoudrane rocks were ranging between 52.25% and 67.53%, indicating that they have undergone moderate to high chemical alteration. The remote sensing techniques employed improve the distribution of these alteration minerals.