Semi-automatic detection of doleritic pipes in the Tindouf basin by Sentinel 2 satellite imagery. ; Détection semi-automatique des cheminées doléritiques du bassin de Tindouf par imagerie satellite Sentinel 2.

International audience ; Doleritic pipes are known in the Tindouf Basin in Algeria since the works of Jaqcuemont (1952) and Gevin (1960), and are assumed to belong to the Central Atlantic Magmatic Province (CAMP). The Tindouf Basin is characterized by an abundance of magmatic formations belonging to the CAMP (Chabou, 2008; Bersi, 2016) which outcrop mainly as sills and dykes. These magmatic formations represented mainly by dolerites, were emplaced at the Triassic-Jurassic boundary (201 Ma) (Chabou, 2008). The sills inject the devono-carboniferous formations and their total thickness can reach a hundred meters (Chabou,2008; Bersi, 2016). Doleritic chimneys outcrop in both flanks of the basin as sub-circular massifs that intersect the Paleozoic formations. On the northern flank, these manifestations are observed in the heart of the Zemoul, Oum El Ksi, Igma, Smeïra and Tinfouchy anticlines, whereas in the southern flank, the chimneys are located in the clay-limestone formations of the Viséen. On the other hand, they are very rich in sulphides and may represent the equivalent of PGE (platinum group elements) rich LIP'S differentiated rocks such as that of the Siberian magmatic province (Norils'k). The present work focuses on the mapping of these magmatic structures using remote sensing. In geological mapping, the treatments usually performed on satellite images give good results using PCA and band ratios (Bersi, 2016; Hachemaoui et al., 2018). However, these treatments seem to be ineffective in discriminating chimneys from the rest of the dolerite formations. In order to characterize doleritic chimneys by remote sensing, we used a semi-automatic detection technique with the Target Detection Wizard tool under ENVI software. This technique allows us to detect targets by correlating all image spectra with spectra obtained in the laboratory. To address the problem of the effects of patina and other disturbances (related to weathering) on the spectral responses of rocks, we opted for the creation of a spectral library ...