Mapeo de redes de fracturas mediante imágenes Landsat-8 OLI en la zona minera de Jbel Tijekht en el Anti-Atlas oriental de Marruecos

Jbel Tijekht is one of the most important geological structures of the Ougnat-Ouzina ridge in the Eastern Anti-Atlas. This crescent-shaped massif was affected by a network fractures that is visible at different scales. It is particularly rich in numerous mineralized veins of barite, and is associated with other minerals (e.g. pyrite, chalcopyrite, sphalerite and galena). In order to study fracture systems in the mining zone of Jbel Tijekht, we opted for a combination of remote sensing and field investigation that became an important tool for fracture mapping and mineral exploration. This work presents a methodological approach to detect structural lineaments. For this purpose, various techniques were applied to the Landsat 8 image to improve the visibility of linear structures. After the radiometric and atmospheric corrections, the colors composites and directional filters applied to the Principal component (PC1) allow for the establishment of a lineaments map of Jbel Tijekht. The validation and the correction of lineaments are based on preexisting documents combined with field observations. Statistical analysis of the lineament map allows for identification of at least three directional fracture systems with average NS, NE-SW, and ENE-WSW orientations. NS and NE-SW systems show a high density in the largest part of the study area. These results clearly overlap different tectonic structures and existing veins. It allowed for the establishment of a geological link between lithology, fractures systems and mineralization. The fracture density can be attributed to the last variscan brittle phases, reflecting the rheology of rock units; the high fracture density is observed in competent rocks such as the Tabanit sandstones. These zones constitute a favorable area for mineralization deposits.El Jbel Tijekht es una de las estructuras geológicas más importantes de la cordillera de Ougnat-Ouzina en el Anti-Atlas Oriental. Este macizo en forma de media luna fue afectado por una red de fracturas que es visible a diferentes escalas. Es particularmente rico en vetas mineralizadas de barita y está asociado con otros minerales (por ejemplo, pirita, calcopirita, esfalerita y galena). Para estudiar los sistemas de fracturas en la zona minera de Jbel Tijekht, optamos por una combinación de teledetección e investigación de campo que se convirtió en una importante herramienta para la cartografía de las fracturas y la exploración de minerales. Este trabajo presenta un enfoque metodológico para detectar los lineamientos estructurales. Para ello, se aplicaron diversas técnicas a la imagen del Landsat 8 para mejorar la visibilidad de las estructuras lineales. Tras correcciones radiométricas y atmosféricas, los colores compuestos y los filtros direccionales aplicados al componente principal (PC1) se pudo establecer un mapa de lineamientos para Jbel Tijekht. La validación y corrección de estos lineamientos se basan en documentos preexistentes combinados con observaciones de campo. El análisis estadístico del mapa de lineamientos permite la identificación de al menos tres sistemas de fractura direccional con orientaciones promedio NS, NE-SW y ENE-WSW. Los sistemas NS y NE-SW muestran una alta densidad en la mayor parte del área de estudio. Estos resultados claramente se superponen a diferentes estructuras tectónicas y a las vetas existentes. Esto permitió establecer un vínculo geológico entre la litología, los sistemas de fracturas y la mineralización. La densidad de fracturas puede atribuirse a las últimas fases de fragilidad del orógeno varisco, lo que refleja la reología de las unidades de roca; la alta densidad de fractura se observa en las rocas competentes como las areniscas de Tabanit. Estas zonas constituyen un área favorable para los depósitos de mineralización

Contribución de las imágenes Landsat 8 OLI al mapeo de lineamientos y series litológicas: implicaciones para la exploración de mineralizaciones de Pb-Zn en el macizo de Boudahar, Alto Atlas oriental, Marruecos

The Boudahar massif is located in the southern part of the eastern belt of the Moroccan High Atlas and it corresponds to a reef mass of about ten kilometers in length. Jbel Boudahar is a district of lead-zinc-barite mineralization, known by a strong artisanal exploitation of its ores. This district is characterized by its topography with a contrast of altitude and an arid environment, which makes the information acquired more valuable. The processing of Landsat 8 OLI data allowed us to extract a lithological and structural map, aiming to make correlations to understand the distribution of lead-zinc mineralization. To this end, several tests were carried out, including the composition of color, principal component analysis and band ratio transformation. The location of the main deposits at Jbel Boudhar coincides well with the lineament derived from band 1 of principal component analysis and with the dolomitic pliensbachian formations mapped by MNF and BR from Landsat Oli8. A remote sensing geological prospecting model has been established for the Jbel Boudhar lead-zinc deposits, providing a basis for future prospecting of new deposits in a similar context.El macizo de Boudahar se encuentra en la parte sur del cinturón oriental del Alto Atlas marroquí y corresponde a una masa arrecifal de unos diez kilómetros de longitud. Jbel Boudahar es un distrito de mineralización de plomo-zinc-barita, conocido por una fuerte explotación artesanal de sus minerales. Este distrito se caracteriza por su topografía con contrastes de altitud y ambiente árido, lo que hace más valiosa la información obtenida. El procesamiento de datos Landsat 8 OLI nos permitió extraer un mapa litológico y estructural, con el objetivo de realizar correlaciones para entender la distribución de la mineralización de plomo-zinc. Para ello se realizaron varias pruebas, entre ellas la composición de color, análisis de componentes principales y transformaciones de ratios de bandas La ubicación de los depósitos principales en Jbel Boudhar coincide bien con el lineamiento derivado de la banda 1 del análisis de componentes principales y con las formaciones dolomíticas pliensbachienses mapeadas por MNF y BR de Landsat OLI8. Así, se ha establecido un modelo de prospección geológica de detección remota para los depósitos de plomo y zinc de Jbel Boudhar, que proporciona una base para la prospección futura de nuevos depósitos en un contexto similar. The processing of Landsat 8 OLI data allowed us to extract lithological and structural data in the Boudahar region, and to make correlations to understand the repartition of lead-zinc mineralization. Several tests were performed, including Color Composite, main component analysis, and band rationing transformation. These results assign high precision to the mapping process using remote sensing, and provide a clear relationship regarding lineaments and lithology, which control the repartition of Boudahar massif mineralization’s

Integrated remote sensing data and field investigations for geological mapping and structural analysis. The case of SW Tichoukt ridge (Middle Atlas, Morocco)

International audienc

Lithostratigraphic, Paleoenvironmental Characterization and Correlations of the Albian–Turonian Deposits of the Errachidia–Boudnib–Erfoud Basin (Southeast Morocco)

Ten detailed sections have been logged and studied from the “Infra-Cenomanian’’ to the Cenomanian–Turonian deposits in the Errachidia–Boudnib–Erfoud Basin between Tazzouguerte and Anounizme(SE Morocco). They show variations in their lithology and microfacies that reflect changes in the depositional environment from the base to the top of the sedimentary record. Indeed, depositional setting grades from a fluvial environment marked by sandstone deposits of the Ifezouane Formation to an alluvial plain and coastal lagoon environment comprising an alternation of red clay, gypsum, and green marl beds of the Aoufous Formation and, finally, towards shallow to moderately deep marine environments with the deposition of the carbonates of the Akrabou Formation. Correlations between the studied sections show variations in the thickness of strata throughout the basin. The variations recorded in the so-called “Infra-Cenomanian” series may be related to the structuration of the basement. The Cenomanian–Turonian carbonate platform shows deeper marine and thicker sediments towards the east, while it thins towards the west until its disappearance in Anounizme. This reflects the global Cenomanian–Turonian transgression in the Errachidia–Boudnib–Erfoud Basin from the eastern Tethyan realm towards the west. The regional correlation of the Errachidia–Boudnib–Erfoud Basin with the Ouarzazate and Agadir basins shows an eastward thinning of the Cenomanian–Turonian marine deposits of Agadir. This suggests the presence of a paleorelief at the Anounizme locality. This could be the boundary between the Errachidia–Boudnib–Erfoud Basin, with Tethyan influence, to the east and those of Ouarzazate and Agadir, with Atlantic affinity, to the west

Lithostratigraphic, Paleoenvironmental Characterization and Correlations of the Albian–Turonian Deposits of the Errachidia–Boudnib–Erfoud Basin (Southeast Morocco)

Ten detailed sections have been logged and studied from the “Infra-Cenomanian’’ to the Cenomanian–Turonian deposits in the Errachidia–Boudnib–Erfoud Basin between Tazzouguerte and Anounizme(SE Morocco). They show variations in their lithology and microfacies that reflect changes in the depositional environment from the base to the top of the sedimentary record. Indeed, depositional setting grades from a fluvial environment marked by sandstone deposits of the Ifezouane Formation to an alluvial plain and coastal lagoon environment comprising an alternation of red clay, gypsum, and green marl beds of the Aoufous Formation and, finally, towards shallow to moderately deep marine environments with the deposition of the carbonates of the Akrabou Formation. Correlations between the studied sections show variations in the thickness of strata throughout the basin. The variations recorded in the so-called “Infra-Cenomanian” series may be related to the structuration of the basement. The Cenomanian–Turonian carbonate platform shows deeper marine and thicker sediments towards the east, while it thins towards the west until its disappearance in Anounizme. This reflects the global Cenomanian–Turonian transgression in the Errachidia–Boudnib–Erfoud Basin from the eastern Tethyan realm towards the west. The regional correlation of the Errachidia–Boudnib–Erfoud Basin with the Ouarzazate and Agadir basins shows an eastward thinning of the Cenomanian–Turonian marine deposits of Agadir. This suggests the presence of a paleorelief at the Anounizme locality. This could be the boundary between the Errachidia–Boudnib–Erfoud Basin, with Tethyan influence, to the east and those of Ouarzazate and Agadir, with Atlantic affinity, to the west