Energetics of calcium-rich dolomite
- Princeton Univ., NJ (United States)
- State Univ. of New York, Stony Brook, NY (United States)
The enthalpy of formation of sedimentary Ca-rich dolomite has been determined by oxide melt calorimetry. The results show that Ca-rich dolomite is energetically different from well-ordered stoichiometric dolomite. The enthalpy of formation from calcite and magnesite becomes strongly more endothermic with increasing excess Ca content. This supports the idea that the substitution of Ca in the Mg layer of dolomite is energetically unfavorable. Ca-rich dolomite is unstable relative to well-ordered stoichiometric dolomite and calcite. The enthalpy behavior for excess Ca substitution in dolomite is different from that of Mg substitution in calcite; the enthalpy change is much larger in magnitude in dolomite and is more strongly dependent on composition. Differences in cation order as well as the presence of a modulated structure and low-symmetry domains in Ca-rich dolomite cannot be discerned from the enthalpy data. The findings confirm that the growth and occurrence of Ca-rich dolomite in sedimentary environments must be attributed to kinetic factors rather than to equilibrium. 47 refs., 2 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG02-85ER13437
- OSTI ID:
- 379166
- Journal Information:
- Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 5 Vol. 59; ISSN GCACAK; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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