Le geothermalisme de la region de Guelma
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The geothermal resources of Algeria are numerous. The latter are in the form of thermal springs that are widespread throughout the northern Algerian territory. They are distributed from East to West, but they are of highest concentration in the East, this area characterized by remarkable geothermal gradient which reaches 50°C/Km. The chemical analysis of the thermal waters and their geological contexts, the use of different statistical methods to evaluate the origin of the dissolved constituents of the thermal waters were realized as well as the estimation of the temperature of the reservoir of the associated geothermal fields of the region study (Guelma, Algeria). Major and heavy metal elements from 13 hydrothermal source samples were analysed using various techniques. The waters of the hydrothermal vents in the Guelma basin vary between 20 and 94°C. The analysis of the hierarchical classification in Q mode suggests three groups and which are confirmed by the ACP and FCM. Water sources have been classified as low, moderate and high salinity waters. The mineral saturation indices (IS) calculated from the major ions indicate that the source waters are supersaturated with most of the carbonate minerals, and that all source water samples are undersaturated with evaporitic minerals. The waters of the thermal springs have a meteoric origin and all the samples are immature with a strong mixture between the warm waters and the shallow waters where the temperatures of the reservoirs to which the thermal waters relate. They vary between 104 and 195°C. The deep circulation of meteoric waters in the study area is fed by the high geothermal gradient around 4.5°C per 100 m and reaches a high temperature before rising to the surface. The reservoir estimated depths ranged from 3000 to 4200 m.