Distribution and Genesis of Potassium-Bearing Minerals in Lop Nor Playa, Xinjiang, China

Abstract

Lop Nor Playa is the main salt-forming area in the Tarim Basin, which is rich in brine resources. There is a large amount of potassium fertilizer produced from potassium-rich brine in Lop Nor annually, which meets about half of the demands of China’s agricultural potash, along with that produced in the Qaidam Basin. In order to investigate the distribution characteristics of potassium-bearing minerals and the origin of potassium-bearing salts in Lop Nor Playa, mineralogy and hydrogeochemistry studies were carried out. The results showed that there are a large number of polyhalite layers distributed in the Luobei Depression and Xinqing Platform. Brines with high content of K+ and Mg2+ have reactions with calcium sulfate minerals, generating secondary polyhalite layers. Carnallite layers are mainly distributed in subbasins along fault zones in all three mining areas with small size. Ca-Cl-type waters rise to the surface along fault zones and mix with ground water as soon as they appear on the ground, forming the deposits of carnallite and bischofite after evaporation. During the generation of potassic salts, fault zones, on the one hand, control the margin of mining areas and the distribution of polyhalite layers. On the other hand, they act as the migration and reaction space for salt spring water, providing large amounts of ore-forming elements such as Ca2+, K+, and Mg2+. This study provides a theoretical basis for the exploration of potassium-rich brine in the Lop Nor Basin.