Lithostructural Mapping Using Landsat OLI images and Field Investigations in the Oumjrane–Boukerzia Mining District, Eastern Anti-Atlas, Morocco

Abstract

The application of remote sensing is considered to be highly efficient in the field of geology, particularly for mapping and discrimination between lithological units, as well as the identification of different surface minerals which enable the acquisition of all the optical and radar data needed to obtain more reliable and particular information, especially in inaccessible areas. Landsat 8 (Operational Land Imager) image bands, which include color compositions 7, 4, and 1, band ratios 7/5, 4/2, 3/1, and 6/3, 6/1, 5/2, Principal Component Analyses PC1, PC4, and PC3, and directional filtering at 0° (NS), 45° (NE–SW), and 90° (EW), were used to analyze the spectral characteristics of the lithological units of the study area and delineate the alteration zones which may contain significant concentrations of base metals. Combined with geological field observations, these data were integrated and analyzed in a geographic information system to establish a multi-criteria characterization of mineralized zones. Hence, the use of remote sensing contributed to the improvement and updating of available geological maps of the Oumjrane–Boukerzia area. Lineament extraction allowed for performed analyses of the structural elements that play a crucial role in the mineral distribution in the study area. Several of the targeted areas were examined in the field by selective sampling. Consequently, the results helped identify new mineralized zones with important mining potential which could be evaluated in the future through detailed geophysical and geochemical work.

Integrating Aster Images Processing and Fieldwork for Identification of Hydrothermal Alteration Zones at the Oumjrane-Boukerzia District, Moroccan Anti-Atlas

“…After downloading the images, the first step consists of the pre-processing of these images applying radiometric and atmospheric correction. Subsequently, a processing step, composed by several techniques, was applied to the spectral bands of the ASTER images such as the colored composition, the principal component analysis and the band ratio technique, in order to improve the visibility and the quality of images [2]. The validation of the results was carried out in two steps: the first is based on the spectral signature of the USGS (United States Geological Survey) library to separate between the minerals presented in the study area, the second step is based on direct field observations in order to determine the family of minerals abundant in the bedrock, which is served as the basic elements of the identified zones.…”

“…The use of remote sensing data, particularly ASTER data, has become more important, especially in the mapping of hydrothermal alteration zones [1]. This data provides more effective information that can help mining exploration geologists, due to the spatial, spectral and radiometric variability and resolution of this image [2]. While the identification of areas that have undergone hydrothermal alteration in the field of mining prospecting requires other important techniques, in this case the exploitation of ASTER data can provide cost-effective solutions for the search for new exploration areas mine before detailed and costly ground investigations [3].…”

“…Then, structural analysis has been made by [9] at the Eastern Anti-Atlas scale, and at the Maider Basin scale by [5] and [10] where they highlight a remarkable NE-trending Variscan shortening of late carboniferous-lower Permian age, which is responsible for the region structuring. The [2] and [11] have performed in this region lithological and fractures mapping based on Landsat 8 OLI image processing. On the scale of the Eastern Anti-Atlas, the Paleozoic terrains are home to several mineral zones, mainly in the form of veins [5] [12].…”

“…This makes the implement of remote sensing of extreme importance for alteration mineral zones. However, no remote sensing work on the delimitation of the alteration zones and identification of the main minerals associated with the copper deposit of Oumjrane-Boukerzia has been published, except the work of that concern the lithological and fractures mapping [2]. The present paper aims to process the spectral bands of ASTER imagery to map the areas of hydrothermal alteration at the Oumjrane-Boukerzia region.…”

“…It has a NE-SW management zone that is 40 km long and 10 km broad. This huge territory (400 km2 ) is situated at the western part of the Maider basin, in the southeast of Jbel Saghro. It is part of the Maider and Tafilalet vein field, and it is made up of Lower and Upper Paleozoic units.…”