Mapping CAMP formations of the northern flank of Tindouf Basin by integrating remotely sensed data, geochemistry and field observations

Abstract The Central Atlantic Magmatic Province (CAMP) is a major Large Igneous Province. Its formation coincides with the breakup of Pangea and the first opening stages of the central Atlantic Ocean. The CAMP consists of mafic rocks, often in the form of sills, dikes, and lava flows, which are spread across four continents (Africa, North America, South America, and Europe). The Algerian CAMP appears in the southwestern Paleozoic Bechar, Tindouf, Hank, and Taoudeni basins, where the magma is intruded within the Paleozoic sedimentary series in the form of giant sills and km-long dikes. The CAMP formations in western Africa are classically subdivided into four stratigraphic units (lower, intermediate, upper, and recurrent); however, only the upper and recurrent units were recognized by previous work in the Tindouf Basin. These two units are geochemically and petrographically well studied, but their spatial distribution and emplacement mode are still unknown. This study maps CAMP units within the northern flank of the Tindouf Basin by integrating geochemical and remote sensing data. As a first step, basic remote sensing techniques such as color composites and ratioing were applied to Landsat 8 images to locate the different CAMP outcrops in the study area. Then, a field expedition was performed to validate preliminary results and collect samples for geochemical and petrographic analysis. The field and laboratory observations show the existence of three different doleritic units: upper, recurrent, and plug-like intrusion units. This last unit contains a high concentration of sulfides (pyrite, chalcopyrite, and sphalerite) that could be of economic interest. The analysis of the combined geochemical results and reflectance values shows a strong concordance between the mineralogical composition and the spectral response of samples. The reflectance variation of CAMP units is widely controlled by iron, magnesium, and calcium oxides. Thus, advanced image processing techniques were applied on Landsat 8 and Sentinel 2A images. Furthermore, the analysis of the spatial distribution of these units, linked to the formation type (sill, dike, or intrusion) and the stratigraphic level (Devonian or Carboniferous), may provide insight to understand the emplacement mechanism and ore potential.