Spatial Distribution, Dynamic Changes and Controlling Factors of Solid Potash Minerals in Qarhan Salt Lake, Qinghai: Responses to Mining-Induced Conditions

Abstract Potassium is crucial for agriculture and industry, with Qarhan Salt Lake being China’s largest potash production base, relying on solid potash liquefaction mining since 2006. This study investigated solid potash minerals in Qarhan using XRD, SEM, and PHREEQC, focusing on their types, spatial-temporal changes, and controlling factors, to provide insights for sustainable mining. Results show three potash minerals: polyhalite, carnallite, and sylvite, with higher contents in central-northern Bieletan, northern Dabson, and northern Qarhan sections. Polyhalite dominates below 4 m, sylvite in 0–4 m, and carnallite is rare. From 2007 to 2022, polyhalite decreased slightly (8.8% to 7.4%), carnallite dropped significantly (2.8% to < 1%), and sylvite remained stable, driven by mining and brine composition changes. Key controlling factors include brine differentiation, mixing effects, and mineral transformation. Future mining should prioritize high-content areas and optimize polyhalite liquefaction.