Hydrochemistry and gas geochemistry of the northeastern Algerian geothermal waters

作者：Belhai M^*; Fujimitsu Y; Nishijima J; Bersi M

来源：Arabian Journal of Geosciences, 2017, 10(1): 8.

DOI：10.1007/s12517-016-2790-2

• Northeastern Algeria
• Geothermal waters
• Gas chemistry
• Geothermometry
• Conceptual model

This study focuses on the water and gas chemistry of the northeastern Algerian thermal waters. The helium gas was used to detect the origin of the geothermal fluid. In the Guelma Basin, the heat flow map shows an anomaly of 120 +/- 20 mW/m(2) linked to the highly conductive Triassic extrusion. The chemical database reveals the existence of three water types, Ca-SO4/Na-Cl, which are related to evaporites and rich in halite and gypsum minerals. The third type is Ca (Na)-HCO3, which mostly characterizes the carbonated Tellian sector. The origin of thermal waters using a gas-mixing model indicates a meteoric origin, except for the El Biban hot spring (W10), which shows a He/Ar ratio of 0.213, thus suggesting the presence of batholith. The helium distribution map indicates a lower He-3/He-4 ratio between 0 Ra and 0.04 Ra in the W10 andW15 samples, which is compatible with the crustal ratio. Reservoir temperatures estimated by silica geothermometers give temperatures less than 133 degrees C. The geothermal conceptual model suggests that a geothermal system was developed by the deep penetration of infiltrated cold waters to a depth of 2.5 km and then heated by a conductive heat source (batholith for El Biban case). The thermal waters rise up to the surface through the deep-seated fractures. During their ascension, they are mixed with shallow cold groundwater, which increase the Mg content and cause the immature classification of the water samples.

• 出版日期2017-1