Geothermal energy potential of a promissory area in the Central and Eastern Zones of Sonora, Mexico: A preliminary geochemical study

Abstract

Geothermal energy is an important renewable energy resource in Mexico, and the evaluation of the energy potential of promising geothermal systems has been defined as an important task for defining the future energy portfolio of the country. For achieving such general goal, a preliminary geochemical study for the evaluation of promissory geothermal zones located in the Central and Eastern of Sonora was carried out. Evidence of previous geological and geochemical exploration studies on the Northwestern zone of Mexico have delimitated some promissory low-to-medium temperature geothermal areas, and suggest that these systems are related to the pull-apart basin dynamics of the Gulf of California hydrothermal systems. The present study was specifically focused to characterize the origin of thermal fluids sampled in the Central and Eastern zone of Sonora, to identify water-rock interaction processes, and to develop a preliminary geochemical model. A field survey was carried out for collecting representative geothermal fluid samples. Chemical analysis of major and minor components in these samples indicated the presence of calcium bicarbonate waters in the Central zone, whereas sulphate-sodium waters were typified for the eastern part. Deep equilibrium temperatures were calculated using new and improved solute geothermometers, and the estimated mean temperature was 150°C. A preliminary geochemical modeling of water-rock interaction processes was also performed using the chemical composition of thermal springs at the expected temperature. Mineral assemblages involving minerals such as muscovite, clinochlore, laumontite, prehnite, kaolinite, and albite were found to be in equilibrium with the geothermal fluids. A deep fluid circulation with the presence of a hydrothermal system characterized by low-to-medium temperatures (T<200°C) seems to dominate in this geothermal system. However, a more detailed study requires to be conducted in the future for a better understanding and characterization of these geothermal resources.