An update on lithium mica thermodynamics and its geothermometrical application

The extraction of lithium from geothermal brines is one of the most promising fields for mining this important element, which plays and will play an increasingly important role in the transition to green energy. Despite this, a thermodynamic database of lithium minerals -which would be useful in geochemical modeling of Li cycling-is still far from complete. In this short communication, the thermodynamic (in particular molar heat equation) and solubility data of a lithium mica mineral with a generic formula KLi0.5Al1.5Si4O10(OH)2 are revised. Furthermore, the solubility data as log(K) are inserted in commonly available thermodynamic databases and applied to the geothermometrical study of the lithium-rich geothermal waters of the Upper Rhine Graben. The general agreement between the temperatures obtained from the equilibrium reaction involving lithium mica and the values already published or from a multicomponent geothermometrical approach confirms the usefulness and importance of lithium mica in the study of lithium-rich geothermal brines.