Mapping of hydrothermal-metasomatic alterations for forecasting gold mineralization based on processing of the Landsat 8 remote sensing spacecraft dataset in the Ahaggar Shield (Southern Algeria)

Mapping of hydrothermal-metasomatic alterations in the Ahaggar, Southern Algeria, was first performed using the Landsat 8 satellite imagery. This area is promising for gold mineralization. The objective of the study was to identify similar patterns in the distribution of hydrothermal-metasomatic alterations to develop forecast and exploration criteria for the gold ore type of mineralization. Thus, it was established that the areas in the Ahaggar Shield promising for gold mineralization localized along and/or inside the transregional fault zone, which controls ore mineralization confined to the periphery of large morphostructures (400 to 800 km in diameter) of the 1st order. Such morphostructures should be complicated by ring, arc structures of the 2nd and higher ranks and faults of NNW and NNE strikes with a length of more than 100 km, or weakened zones along which intrusions of dikes of medium (gabbro-diorites, diorites) composition associated with gold ore mineralization are recorded. In addition, metasomatic halos of a significant area (more than 30 km2) with increased values of indices of oxides of di- (magnetite) and trivalent iron (hematite), and to a lesser extent oxides and hydroxides of iron (limonite) and hydroxyl- (Al-OH, Mg-OH), carbonate-containing minerals and oxides should be manifested in potentially ore-bearing volcanic structures.