24/03/2026
Conference paper: Geochemical analyses of Triassic rocks in the Upper Rhine Graben: A first lithium study in sedimentary rocks of Soultz-sous-Forêts wells
Abstract
The Upper Rhine Graben (URG) is a promising area for geothermal lithium (Li) extraction. Li concentrations in deep geothermal brine exceed 150 mg/L and are combined with significant flowrates suitable for geothermal power and heat production. However, there is still a lack of knowledge in the mechanisms leading to the brine enrichment in Li. Based on a total of 34 core samples collected from both the Triassic limestone and the sandstone from the Soultz-sous-Forêts wells (GPK-1 and EPS-1), this study aims to characterise the Li content of the samples according to depth and the lithostratigraphy. Also, this study aims to correlate the Li content with the eventual mineralogical changes underwent by the rock induced by fluid-rock interactions (precipitation and/or dissolution) in the case of diagenesis or hydrothermal circulations channelised by natural fractures.
Additionally, a comparison of Li content between Variscan and Triassic rocks allows to make the hypothesis that the water-rock interactions in both lithologies allow to put Li in solution, released from phyllosilicates. The Li in solution in the brine could then be trapped preferentially in permeable zones in all lithologies but reaching significant higher values in the deep-seated granite. Also, as in the Muschelkalk and the Buntsandstein the Li concentration varies only between 1 and 90 ppm, compared to up to 1938 ppm in the granite, which could eventually suggest that the brine could contain more Li in solution in the Triassic formations. These results refine the story behind high Li concentration in the URG brine and eventually underlines specific reservoir zones where Li concentration could be enriched in the brine.
Discover the paper on the website of the European Geothermal Congress 2025: link
Authors: Carole Glaas, David Fries, Gabrielle Rumbach, Albert Genter