Kinetics of dolomitization
Dolomitization of CaCO/sub 3/ in the laboratory at greater than or equal to 175/sup 0/C demonstrates that the transformation has two distinct stages: an induction stage during which no detectable products form and a nucleation-growth stage during which dolomite forms at the expense of the reactant CaCO/sub 3/. Experiments at 218/sup 0/C demonstrate that as the Mg/Ca ratio of the solution increases, the length of the induction stage decreases. Addition of CO/sub 2/ to the solution decreases the induction stage and also changes the overall transformation mechanism. Previously published data show that the induction stage is affected by the temperature of the reaction and the surface area and mineralogy of the reactant. The induction stage is often the slowest part of the overall transformation. Characteristics of natural dolomites that are consistent with the experimental results include the following: (1) Dolomite selectively replaces fine crystalline CaCO/sub 3/; (2) most carbonate rocks are 100% dolomite or 100% calcite; (3) limestone-dolomite contacts are usually sharp and involve a decrease in the number of dolomite rhombs, but the size of the rhombs remains constant; (4) dolomite in completely dolomitized rocks is more stoichiometric than dolomite in partially dolomitized rocks; (5) aragonite is selectively dolomitized in modern sabkha sediments; and (6) modern dolomite is most abundant in areas of elevated Mg/Ca ratio or HCO/sub 3//sup -/.
- Research Organization:
- Michigan State Univ., East Lansing (USA)
- OSTI ID:
- 5286806
- Journal Information:
- Geology; (United States), Journal Name: Geology; (United States) Vol. 15:12; ISSN GLGYB
- Country of Publication:
- United States
- Language:
- English
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58 GEOSCIENCES
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
BENCH-SCALE EXPERIMENTS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DOLOMITE
GEOLOGIC DEPOSITS
KINETICS
LIMESTONE
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERALIZATION
MINERALS
OXYGEN COMPOUNDS
REACTION KINETICS
ROCKS
SEDIMENTARY ROCKS
SYNTHESIS