Theoretical mechanism of dolomitization--A hypothesis
- Univ. of Illinois, Urbana, IL (United States). Dept. of Geology
Based on the following reasoning, dolomite domain hypothesis is proposed to interpret the mechanism of dolomitization: to a first approximation, the crystal structure of dolomite can be derived from the substitution of Mg[sup +2] for Ca[sup +2] in alternate cation layers. But, because of the difference in radius between Ca[sup +2] and Mg[sup +2] ions, substitution will lead to a distortion of CO[sub 3][sup [minus]2] ions, with their C-O bonds bent towards Mg[sup +2]. The CO[minus]3[sup [minus]2] distortion leads to a volume decrease in Mg layers and a volume increase in Ca layers, which promotes the tendency for layer segregation of Ca and Mg during crystallization. In magnesium calcite, dolomite domains may be formed as a result of this cation segregation. The dolomite domains serve as nuclei during replacement. Dolomitization of magnesium calcite begins with dissolution and precipitation along the boundaries between dolomite and calcite domains, where strain exists as a result of differences in CO[sub 3][sup [minus]2] distortion. The process is basically one of partial dissolution and overgrowth which can preserve the original morphology. Because of the inclusions of precursor dolomite domains, equilibrium with the dolomitizing solution is not necessarily reached. This is significant for the interpretation of trace element and isotopic compositions of dolomites.
- OSTI ID:
- 5999994
- Report Number(s):
- CONF-921058--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 24:7; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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