Enrichment mechanism of Li, B and K in the geothermal water and associated deposits from the Kawu area of the Tibetan plateau: Constraints from geochemical experimental data

In the Tibetan Plateau, most geothermal springs show an unusual enrichment of boron and lithium and other typical resources dissolved in hot water or geothermal deposits. The evolution of the geothermal water and the distribution of elements during the phase separation of residual liquid and associated deposits remain unclear. Through a chemical analysis of the deposits and geothermal water in the Kawu area during primary discharge and later evaporation, the elemental distribution and enrichment processes between the two phases of deposits and the mother water are discussed. Basic results show that the elements Li, B and K are preferentially enriched in the geothermal water rather than distributed into the geothermal deposits of travertine during the primary phase separation of geothermal water discharge. The elements B and K, as a whole, are enriched in the late residual mother water in the later stages during evapoconcentration. However, Li shows a distinctly depleted trend in the residual mother water at the stage when the lithium carbonate precipitates in the deposits. The most important finding of the evapoconcentration experiment is that the zabuyelite, an unusual lithium carbonate mineral, is firstly detected in the mineral association of geothermal deposits. It is only precipitated within a very small interval during an intermediate stage with a very high concentration of Li while there are very low concentrations of Ca and Mg and an unusually high Li/Mg ratio in the mother geothermal water. The zabuyelite is a trademark mineral in the salt lake deposits in the Tibetan Plateau. This is the first time it has been found in the mineral association of deposits of evapoconcentrated geothermal water. This indicates that geothermal water discharge may be the main source for Li, B and K accumulation in the salt lakes. In addition, the typical elements of Li, B and K are extremely enriched during the late stage of the residual mother water or precipitate as zabuyelite or sylvite within a very concentrative stage. They are also very promising mineral resources for development and utilization.