World Geothermal Congress 2020+1
March - October, 2021

Geochemical Characteristics of Thermal Fluids from Northwest Algeria

Mohamed BELHAI, Yasuhiro FUJIMITSU, Rosa Maria BARRAGAN-REYES, Tatsuto IWANAGA, Mamiko MAENO, Brahim AYAD, Fatima Zohra BOUCHAREB-HAOUCHINE, Jun NISHIJIMA, Djelloul BELHAI, Abdelhamid HAOUCHINE

[Sunny Hill Energy, Algeria]

The geothermal manifestations of thermal springs, travertine deposition and hydrothermal alteration zones in the Northwestern part of Algeria were formed during the Mio-Plio-Quaternary volcanic activities. The geothermal reservoirs are hosted in the fractured Jurassic dolomite and limestone formations, named the “Tlemcenian dolomites formations”. The chemistry of twenty-one hot spring water samples highlights the heterogeneity of water mineralization processes in NW Algeria. Three major types of water were identified: Na-Cl, Ca-SO4 and Na-HCO3 (Cl). The first two water types contain high salinity and higher contents of F, B, Li, Br and Cs, and are derived from evaporites rich in halite and gypsum minerals, linked to the Triassic extrusion and Messinian saline formation of the Atlasic land and the Tellian sector, respectively. While the third type is mainly associated with the carbonate forma tions of the Tellian sector. The stable isotopes (δ18 O and δ2H) results and the gas mixing models (N2-He*1000-Ar*100 with O2-CO2-He*1000) reveal the meteoric origin of the thermal waters. According to the Na-K-Mg Ternary plot, the thermal waters are immature. The deep geothermal reservoir temperatures are presumed to be circa 140°C based on K/Na Giggenbach geothermometer model. The geochemical conceptual model indicates the meteoric origin of thermal springs which were heated as result of deep infiltration and conductive heat flow (120 mW/m2) in the region brought about by tectonic activity. The deep geothermal fluids are mixed with cooler waters rich in Mg and leach Mg from the surrounding rocks during their rise to the surface.

        Topic: Geochemistry Paper Number: 14122

         Session 8P: Poster 2 [Tuesday 11th May 2021, 11:00 pm] (UTC-8)
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