limestonedolomite

Limestonedolomite is a carbonate sedimentary rock that contains substantial amounts of both calcite (CaCO3) and dolomite (CaMg(CO3)2). In practice the term describes rocks in which dolomite is present alongside limestone components, often as a product of diagenetic dolomitization of limestone. Rocks labeled limestonedolomite can range from calcite-dominated limestone with some dolomite to dolostones with notable, but not exclusive, calcite fillings.

Mineralogy and textures commonly show intergrown dolomite and calcite crystals, with dolomite commonly forming rhombohedral or polycrystalline aggregates. The rock may preserve fossil fragments within a dolomitic matrix, and textures can include nodular, bedded, or fine-grained mudstone varieties. Porosity and permeability are variable and largely depend on the extent and pattern of dolomitization and cementation.

Formation and diagenesis are central to limestonedolomite. Many such rocks form through dolomitization, where magnesium-rich fluids pass through limestone during burial or in sabkha-like environments, replacing calcite with dolomite. This process can occur during early diagenesis or later, creating distinct diagenetic fronts, variably affecting porosity and rock strength.

Occurrence and distribution are widespread in ancient and modern carbonate successions. Limestonedolomite is found in sedimentary basins worldwide, especially where conditions favored dolomitizing fluids, such as shallow marine platforms, evaporitic settings, and high-temperature burial environments.

Economic and practical aspects include use as building stone, aggregate, and cement constituent, with dolomitized portions potentially influencing reservoir quality in hydrocarbon systems. Identification typically relies on field description and petrographic analysis, with acid tests showing variable effervescence and microscopic examination revealing mixed calcite-dolomite textures.