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Lithological discrimination and mineralogical mapping using ASTER remote sensing data in the east-central Jebilet region, Morocco

El Khounaijri Hayat, Algouti Ahmed, Algouti Abdellah, Essemani Mohamed, Hadach Fatiha, Baid Soukaina, Ezzahzi Salma, Kabili Salma, Agli Saloua, Jdaba Naji

Geologos

2025

Vol. 31, No. 2

167--177

This study evaluates the effectiveness of ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) satellite data for lithological discrimination and mineralogical mapping in the east-central Jebilet region, Morocco. ASTER data offer considerable potential for detecting spectral signatures of mineral zones and determining their composition. The main objective is to apply image processing techniques, such as band ratios (BR), principal component analysis (PCA) and minimum noise fraction (MNF), in order to identify and map characteristic minerals in the region. The application of various band ratios effectively mapped the distribution of key minerals and alteration zones in the study area. The band ratio (band7/band5) was used to identify kaolinite, while the ratio (band4+band6)/band5 highlighted the presence of a mineral group constisting of alunite, kaolinite and pyrophyllite. The ratio (band7+band9)/ band8 revealed a set of a carbonate mineral, chlorite and epidote, whereas endoskarns composed of epidote, chlorite and amphibole were mapped using the ratio (band6+band9)/(band7+band8). The ratio (band5+band7)/band6 characterised phyllic alteration by detecting phyllosilicate minerals such as sericite, muscovite or illite. Phengite was mapped using the band5/band6 ratio. The distribution of these minerals was closely linked to the lithological variability of previously mapped geological units, highlighting the relevance and effectiveness of band ratios for geological mapping using remote sensing. The PCA and MNF components with the highest eigenvalues significantly improved lithological discrimination by reducing noise and refining the delineation of mineral zones. The results obtained have enabled the creation of a detailed map of mineral distribution, highlighting the alteration zones and lithological formations in the eastern Jebilet region of Morocco.time-consuming, yet inexpensive method that can be applied to other areas, especially those that are difficult to reach.

Structural and mineralogical mapping using multispectral satellite data (Aster, Landsat 8 OLI, and Sentinel 2B) combined with field work in the Western High Atlas, Morocco

Elbakhouch Nouhaila, Ibouh Hassan, Touil Ahmed, Chafiki Driss

Geologos

2024

Vol. 30, No. 2

119--136

The Tighardine area in the Western High Atlas Massif is composed of rocks ranging in age from Neoproterozoic to Cenozoic. The area is intensely deformed with a multidirectional diversity of faults and also hosts a polymetallic ore deposit (Tighardine mine) and prospects of significant economic value, some of which are related to fault structures. In order to identify favourable areas of mineral deposition, structural and mineralogical mapping using satellite images was conducted in this region. For this purpose, various remote sensing approaches were employed on images from Landsat 8 OLI, Sentinel 2 and ASTER sensors. The process started with lineament extraction methods so as to identify faults manually from satellite images. Principal component analysis (PCA) and the optimal indexing factor (OIF) were used to achieve good discrimination of lithological units. Additionally, several band ratios were applied to ASTER, Landsat 8 OLI and Sentinel 2, in order to derive multiple maps corresponding to hydrothermal alteration zones. Analysis of the results from the obtained maps and their overlay with field data has allowed us to: (i) identify three main structural orientations. The most frequent and longest is the NE–SW direction, which coincides with the principal mineralised horizon of the Tighardine deposit. Results suggest an extension of this horizon towards the south-west at the Ait Zitoune and towards the west in the Ait Hsayn region. Two new fault set has been identified by remote sensing: NW-SE fracture, generally of Mesozoic-Cenozoic age, and an E-W fractures trend, particularly developed in the Neoproterozoic basement and considered of Ediacaran age; (ii) highlighting two potential mineralisation zones: in the Ediacaran basement, revealing alterations of silica, dolomite, clay minerals, iron oxide and alunite-kaolinite-pyrophyllite, hosting the main mineralisation axis (Tighardine mine); in the northern part corresponding to the overthrust zones of Cambrian onto Cenozoic formations.