Geochemical behavior of Li in deep geothermal systems of the North German Basin and Upper Rhine Graben: Hydrothermal experiments under in-situ conditions

Li extraction as a byproduct in deep geothermal power plants is a promising option for the upcoming challenges in Li supply chains. In Germany, regions in the North German Basin and Upper Rhine Valley are suitable for these kind of operations as Li concentrations reach up to 375 mg/l in deep formation waters [1]. To provide further insights on the occurrence of Li in deep formation waters, its geochemical behavior and possible release reactions of Li from mineral dissolution or surface exchange in deep geothermal systems, experiments at in situ conditions (100 – 160 °C, 370 bar) with drill core material of reservoirs rock were conducted in Au capsule and flexible Dickson-type Au-Ti cells. In addition, rock samples were investigated by petrographic and geochemical analysis in order to identify the main Li-bearing mineral phases and their respective Li concentrations. Results of fs-LA-ICP-MS measurements identified chlorite and biotite to be the main Li-bearing minerals, but low Li concentrations were also found in multiple other mineral phases. Batch experiments revealed that a near-equilibrium concentrations for Li are attained rapidly in 3 to 6 days of experimental run time.

[1] Alms, K., Jagert, F., Blömer, J., & Gehrke, I. (2022). Co-production of geothermal energy and lithium from geothermal waters. In European Congress.