Hydrogeochemical investigations of thermal waters in the northeastern part of Morocco

Northeastern Morocco is characterised by a large number of surface geothermal manifestations. Thermal waters are hosted within sedimentary rocks, and in particular the Liassic dolomitic limestones act as a reservoir. The presence of geothermal waters is closely related to important fault systems. Meteoric water infiltrates along those fractures and faults, gets heated, and then returns to the surface through hydrothermal conduits. Most of the thermal waters are of Na-Cl and Ca-Mg-HCO3 types. In this paper different geochemical approaches were applied to infer the reservoir temperature. Na-K-Mg-1/2 ternary diagram points to temperatures ranging from 100 to 180 A degrees C. Cation geothermometers suggest an average reservoir temperature of about 100 A degrees C. Mineral solution equilibria analysis yields temperatures ranging from 50 to 185 A degrees C. The silica enthalpy mixture model gives an average value (about 110 A degrees C) higher than that inferred from cation geothermometers.