Dolomitisaatio

Dolomitisaatio is a geological process whereby calcium carbonate (CaCO3) in limestone is replaced by dolomite [CaMg(CO3)2], a mineral composed of calcium magnesium carbonate. This transformation results in the formation of dolostone, also known as dolomite rock. The process typically occurs after the initial deposition of the limestone, often facilitated by magnesium-rich fluids circulating through the rock.

The exact mechanisms and environments for dolomitisaatio are still debated, but several theories exist. One prominent model suggests that magnesium-rich pore waters, often derived from evaporated seawater or brines, react with calcium carbonate. This reaction involves the dissolution of calcium carbonate and the precipitation of dolomite, a more stable mineral under certain conditions. Another theory proposes that dolomitisaatio can occur contemporaneously with deposition, particularly in specific marine environments with high magnesium-to-calcium ratios.

Dolomitisaatio can significantly alter the porosity and permeability of a rock. In some cases, it can increase porosity by creating vugs and intercrystalline pore spaces, making dolostones important reservoirs for oil and natural gas. In other instances, the precipitation of dolomite can reduce porosity by filling existing pore spaces. The process is widespread in geological history and is responsible for the formation of vast quantities of dolostone found in sedimentary basins worldwide. It is an important consideration in understanding the diagenetic history of carbonate rocks and their potential as resource reservoirs.