Energetics of calcium-rich dolomite

L. Chai, A. Navrotsky, R. J. Reeder

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

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.

Original languageEnglish (US)
Pages (from-to)939-944
Number of pages6
JournalGeochimica et Cosmochimica Acta
Volume59
Issue number5
DOIs
StatePublished - Mar 1995
Externally publishedYes

ASJC Scopus subject areas

  • Geochemistry and Petrology

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