The Origin of Massive Dolomite

Most dolomite forms as a calcium-rich and/or poorly ordered metastable phase when seawater is actively circulated through carbonate sediments. Modification of seawater by evaporation, mixing with meteoric water, and/or sulfate reduction promotes dolomitization, but is not necessary. The extensive circulation which is necessary for massive dolomitization can be caused by density or elevation head, or by convection induced by geothermal heat. Progressive stabilization of metastable dolomite (replacement by more stable phases), especially at slightly elevated temperatures in the subsurface, results in crystal enlargement and chemical modification which masks original properties.