calcitecemented

Calcitecemented refers to sedimentary rocks in which the pore spaces or grain contacts have been cemented by calcite, a calcium carbonate mineral. This type of cement commonly forms during diagenesis when calcium-rich fluids transport carbonate ions and precipitate calcite within pore spaces, binding grains together and reducing porosity.

Formation typically occurs in burial and diagenetic environments. Calcite cement can precipitate from marine pore waters or meteoric waters that infiltrate sediment, with factors such as CO2 partial pressure, temperature, fluid chemistry, and saturation state controlling crystal size and texture. The resulting cement can appear as fine-grained micrite or as coarser sparry calcite, sometimes forming later overgrowths that fill remaining voids.

Effects on rock properties are most notable in porosity and permeability. Calcite cement reduces connected pore space, often lowering reservoir quality in sandstones and impacting fluid flow in hydrocarbon, groundwater, and aquifer systems. In some cases, cementation preserves the sedimentary fabric and enhances strength but at the expense of porosity. Later diagenetic processes, such as dissolution or dolomitization, can modify or partially reverse cemented textures.

Identification typically relies on thin-section petrography, where calcite cement appears as crystalline bands or pore-filling material, and on stable isotope and fluid inclusion analyses to interpret diagenetic conditions. Calcite cement is common in sandstone and in lithified carbonate-rock systems where diagenetic cementation is a dominant diagenetic phase.

See also: cementation, diagenesis, sandstone, limestone, calcite, porosity.