Interdisciplinary Approach and Geodynamic Implications of the Goutitir Geothermal System (Eastern Meseta, Morocco)

Abstract

Morocco has an important geothermal potential materialized by its several thermal springs which constitute an essential surface geothermal indicator. These springs are dispersed throughout the country and present in every major structural domain. However, a significant amount is concentrated in the northern and northeastern areas. Associated with the great hydrothermal system of eastern Morocco, the thermal spring of Goutitir emerges in the Meso-Cenozoic sedimentary formations located east of the Guercif Basin, composed of a mixture of clays, carbonates, and marls, covered in unconformity by Quaternary tabular molasses. The upflow of the thermal water is dependent of Alpine faults systems with N30 and N100 directions, which are probable reactivated Hercynian structures that facilitate its circulation to the surface. The Goutitir spring has been studied by an interdisciplinary approach to identify the origin of the thermal water, the rock–water interactions, and the reservoir temperatures, contributing to the establishment of the conceptual model of the associated hydrothermal system. This thermal water is of chloride-sodium type with a hyperthermal character (43–47 °C). The isotopic composition (δ18O = −8.7 to −8.35‰; δ2H = −58.6 to −54.3‰) indicates a meteoric origin and a recharging zone located at around 2000 m of altitude. The chemical composition allows to classify the water as chloride-sodium hydrochemical facies, stabilized at ~100 °C in crystalline basement rocks, which, according to seismic data, are located at ~3 km depth. The concentrations, patterns, and correlations of trace elements point out water–rock interaction processes between the deep water and basic magmatic rocks. The integration of the chemical and isotopic data and the surface geological context shows that the Goutitir water flows within a hydrothermal zone were basic to ultrabasic lamprophyres rich in gabbroic xenoliths outcrop, witnessing the existence, at depth, of basic plutons. Moreover, near the source, these veins are strongly altered and hydrothermalized, showing late recrystallization of centimetric-sized biotites. The chloride-sodium composition of this water may also be a testimony to the presence and reaction with the overlying Triassic saline and gypsiferous and Meso-Cenozoic mainly carbonated formations.