dolomitizzata

Dolomitizzazione refers to the geological process by which limestone, primarily composed of the mineral calcite (calcium carbonate, CaCO₃), is transformed into dolostone (or dolomite), a rock containing at least 50% dolomite (calcium magnesium carbonate, CaMg(CO₃)₂). This alteration occurs through the substitution of magnesium ions (Mg²⁺) for calcium ions (Ca²⁺) in the calcite structure, a process known as magnesium metasomatism.

The exact mechanisms of dolomitization remain debated among geologists, but several theories have been proposed. One leading hypothesis involves the evaporation of seawater in restricted basins, where high concentrations of magnesium-rich brines facilitate the reaction. Another theory suggests that microbial activity, particularly sulfate-reducing bacteria, may play a role by altering the chemistry of pore fluids. Additionally, dolomitization can occur through the upward migration of magnesium-rich fluids from deeper sedimentary layers or hydrothermal systems.

Dolomitization often occurs in shallow marine environments, particularly in lagoons or tidal flats, where evaporation and restricted circulation enhance magnesium enrichment. The process typically requires specific conditions, such as elevated temperatures, low calcium-to-magnesium ratios, and sufficient pore space for fluid circulation. Unlike limestone, dolostone is more resistant to chemical weathering and dissolution, contributing to its preservation in the geological record.

Dolomitized rocks are significant in petroleum geology, as dolostone reservoirs often exhibit high porosity and permeability, making them valuable targets for hydrocarbon exploration. The process also affects the physical properties of sedimentary rocks, influencing their mechanical behavior and diagenetic evolution. Studying dolomitization provides insights into ancient paleoenvironments, fluid dynamics, and the long-term stability of carbonate platforms.