Hydrogen and Oxygen Isotopes as Key Monitoring Indexes for Deep Confined Brine Mining: Insights from Mahai Salt Lake, Qaidam Basin

Salt lake brine-type potassium-lithium deposits play an important role as a strategic mineral resource that is in short supply in China and the rest of the world. In the case of long-term, high-intensity exploitation of brine resources, if large-scale active faults are encountered, these faults will form advantageous channels for brine migration. In some special cases, the surface fresh water leaks into these advantageous channels and will soon produce a large amount of fresh water in the brine mining well area, resulting in the destruction of the mining well and in the reduction in the potassium lithium grade of the brine. Based on the monitoring of the chemical components and hydrogen and oxygen isotopes of brine in mining wells, combined with the principle of stable isotope conservation, the influence of freshwater leakage accidents on brine extraction wells was quantitatively calculated. The amount of fresh water added to brine by accident is approximately 78%. This further indicates that it is necessary to strengthen long-term monitoring of the chemical components of confined brine to ensure sustainable and stable production.