Evaporitiska

Evaporitiska refers to rocks and sediments formed by the evaporation of water in enclosed or semi-enclosed basins, where rising salinity causes minerals to precipitate from brines. This process is most common in arid or semi-arid regions with limited inflow and high evaporation rates, such as salt lakes, saline playas, and coastal sabkhas.

The defining feature of evaporitic environments is the sequential precipitation of minerals as brines concentrate. In many marine-derived systems, gypsum and anhydrite precipitate before halite as salinity increases, and in the most concentrated brines, potassium salts (such as sylvite and carnallite) may form. Carbonate minerals can appear early in some settings, while borates and other specialty salts occur in specific chemical conditions. The result is typically layered sediment beds, sometimes separated into distinct minerogenic units.

Common evaporitic minerals include halite (rock salt), gypsum (calcium sulfate dihydrate), and anhydrite (calcium sulfate). Potash salts such as sylvite and carnallite, along with borates in certain basins, also occur. Evaporite deposits may be interbedded with clastic sediments and can be diagenetically altered, for example gypsum transforming to anhydrite under burial conditions.

Significance and occurrences: today, evaporites form in active salt flats, saline lakes, and coastal evaporite basins around the world, including the Atacama region, parts of the Sahara, and margins of the Dead Sea. Ancient evaporite sequences are important stratigraphic markers and provide essential mineral resources, especially for salt and fertilizer industries. Evaporitiska deposits also influence reservoir sealing in hydrocarbon basins due to their low permeability and later diagenetic history.