Gypsum deposits are mainly sedimentary deposits, with reserves accounting for more than 90% of the country, and epigenetic and hydrothermal metasomatic gypsum deposits are not very important. Gypsum deposits are produced in all geological ages, and the most important ones are the Early Cretaceous and Tertiary sedimentary gypsum deposits.
Mainly the product of chemical deposition, often forming huge ore layers or lenses, occurring in limestone, red shale and sandstone, marl and claystone series, often symbiotic with anhydrite and halite. Anhydrite layer In the near-surface part, due to the decrease of external pressure, it is transformed into gypsum by the action of surface water: CaSO4+2H2O——CaSO4·2H2O; at the same time, the volume increases by about 30%, causing the destruction of the gypsum layer.
