Abstract
The northeastern part of Algeria has numerous thermal karstic springs which present an economicalinterest for the national office of the Algerian tourism. This organization considers the setting-up ofinfrastructures dedicated to the thermal tourism. The springs are located in a region of a 535 000 kmCwhich extends from Bejaïa to El-Kala (Tunisian border). The geological context is marked by ageological structure inherited of the alpine tectonic episodes Priabonia n to Tortonian at the origin oflarge faults and thrust systems. An analysis of the hydrochemical char acteristics of these waters, hasbe realised, at the regional scale, mainly to determine the geotectonic factors being the cause of thechemical facies and rising, but also to identify one or several deep geothermal reservoirs. Twosampling campaigns were realized on 52 sites, one during low waters (September, 2014) and theother during high waters (May, 2015). The analysis concerned major and trace elements, and isotopes(O18, H2, H3, Sr87 Sr86). From binary diagrams and from ACP treatments, results allowed todiscriminate 4 geochemical groups of waters. (1) a HCO3-Ca type, slightly mineralized andcharacterizing hypothermal waters with fast circulations, (2) a HCO3-Na type, more mineralized andcharacterizing mesothermal waters with deeper circulations, marked by phenomena of base exchangebetween water and clay levels, (3) a Cl-Na type, characterizing hyperthermal waters with deepcirculations attested by chemical exchanges with sedimentary evaporite levels, finally (4) a SO4-Catype having acquired its mineralization in triassic formations. Furthermore, a high percentage (75%) ofhyper or mesothermal springs, with chloride or sulphate facies, are located along the large regionalfaults identified by geophysical investigation. These results will be clarified by the use of silicium andalkaline geothermometers and temperature estimation using saturation index.