Petrogenesis, radiogenic heat production, and geothermal potential of host rocks in the Al-Lith geothermal system, Western Saudi Arabia

Abstract

Geothermal energy is emerging as a sustainable and low-carbon energy source globally, gaining significant attention worldwide. In the Middle East, the exceptional situation of Saudi Arabia along the western coast of the Red Sea makes it a host to many geothermal resources; however, the geochemical characterization of the geothermal resource remains limited. This study investigates the geochemical and mineralogical characteristics of the Al-Lith geothermal system, combining geochemical evaluation with microscopic investigation. Whole-rock geochemistry focuses on major, trace, and rare earth elements, including radioactive elements like uranium, thorium, and potassium, to assess radiogenic heat production. Results reveal that the study area is dominated by granitic and low to medium-grade metamorphic rocks, with low to moderate mineral alteration linked to hydrothermal activity. Granitic rocks exhibit higher radiogenic heat production (average 0.71 μW/m3) than metamorphic rocks (average 0.68 μW/m3), primarily due to elevated uranium and thorium concentrations. Elemental enrichment and depletion trends suggest a volcanic arc granite origin, reflecting subduction-modified mantle and crustal sources. These felsic rocks enhance geothermal potential by providing thermal buffering and facilitating heat transfer. This study provides critical insights into the geochemical and radiogenic heat characteristics of host rocks in Al-Lith, offering a foundation for geothermal resource modeling and exploration.