dolomitized

Dolomitized describes rocks that have undergone dolomitization, a diagenetic process in which calcium carbonate minerals in limestone or other carbonate rocks are replaced by the mineral dolomite, CaMg(CO3)2, or recrystallized to form dolostone. The resulting rock may preserve much of the original texture, but its mineralogy is dominated by dolomite.

The dolomitization process typically involves magnesium-rich fluids percolating through sedimentary layers and replacing calcite with dolomite. These fluids can originate from seawater, evaporitic brines, or other diagenetic sources, and may act during early burial or later tectonic events. Conditions favoring dolomitization include limited calcium activity, elevated magnesium availability, and appropriate fluid-rock interaction timescales. The replacement can occur incrementally, producing replacement dolomite, or as cement, where dolomite crystallizes within pore spaces.

Textures observed in dolomitized rocks include replacement dolomite that preserves much of the original rock fabric,, as well as saddle dolomite crystals in more permeable zones. Isotope compositions and fluid inclusions often record the diagenetic fluids' characteristics. Dolomitization can modify porosity and permeability, sometimes enhancing reservoir quality, but in other cases reducing it through cementation or compaction.

Geologically, dolomitization is widespread in ancient carbonate platforms and can complicate stratigraphic interpretation and diagenetic histories. It is a key process in understanding carbonate reservoir evolution, groundwater flow in carbonates, and the interpretation of paleoenvironments in the rock record.