Abstract

Valyashko has shown that reaction between calcium bicarbonate and sulfate in solution at one atmosphere will produce, primarily, gypsum and a magnesium carbonate complex. A secondary reaction is: 2Ca(HCO 3 ) 2 +MgSO 4 -->CaMg(CO 3 ) 2 CaSO 4 +2H 2 O2CO 2 At pressures on the CO 2 higher than one atmosphere, this reaction could account for extensive dolomite formation. Kramer considers the solubility products of calcite and dolomite relative to: 1) [CO 3 ] and salinity, and 2) pH and salinity, and indicates that an environment with a pH buffer could maintain the pH and salinity required for dolomitization. Observations by Wells in lagoons around the Qatar Peninsula in the Persian Gulf indicate that the development of gypsum and dolomite increases landward as a result of precipitation in tidal pools. Salinity in the dolomite-gypsum sediment is about 275%. Chilingar and Bissel suggest that in the past dolomitization occurred at CO 2 pressures higher than the present, and that at normal CO 2 pressure and higher temperatures, primary and diagenetic dolomite may form in a saline environment. Such an environment was observed in western Utah where a salt pan crust provides a greenhouse effect for underlying dolomite-rich mud.

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