Diffusion-induced grain-boundary migration in calcite

Journal Article · Wed Jan 01 00:00:00 EST 1986 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1986)14<60:DGMIC>2.0.CO;2· OSTI ID:5587431

Evans, B; Hay, R S; Shimizu, N

Grain boundaries in synthetic calcite bicrystals and slabs of Yule marble exposed to SrCO/sub 3/ at temperatures between 650 and 800/sup 0/C undergo diffusion-induced grain-boundary migration (DIGM). As the boundary migrates through the crystal, it produces a (Ca, Sr)CO/sub 3/ solid solution. DIGM is known to occur in metals at temperatures as low as one-third the melting temperature, where lattice diffusion rates are insignificant compared to grain-boundary diffusion rates. The similarity between microstructures in calcite and metals systems is striking. In both systems, grain boundaries migrate to increase their total area and reduce their radius of curvature, migration occurs in the absence of significant stored internal strain energy, and boundary migration is accompanied by changes in the chemical composition of the solid. Although a widely accepted theory for DIGM is lacking, it is clear that the process involved the formation of a compositionally distinct phase, which grows by material transport along an advancing grain of interphase boundary. Grain-boundary migration during DIGM must be driven at least in part by the reduction of chemical free energy associated with the chemical composition change that takes place behind the advancing boundary. Although the reaction mechanisms by which multicomponent, multiphase systems in the earth reach equilibrium are likely to be numerous and diverse, it is possible that some mechanisms are analogous to the DIGM as observed in laboratory experiments on calcite bicrystals. 32 references, 4 figures, 1 table.

• Research Organization: Massachusetts Institute of Technology, Cambridge
• OSTI ID: 5587431
• Journal Information: Geology; (United States), Vol. 14:1
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CALCITE
GRAIN BOUNDARIES
MASS TRANSFER
MARBLE
BOUNDARY CONDITIONS
DIFFUSION
REACTION KINETICS
STRONTIUM CARBONATES
TEMPERATURE EFFECTS
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CRYSTAL STRUCTURE
KINETICS
METAMORPHIC ROCKS
MICROSTRUCTURE
MINERALS
OXYGEN COMPOUNDS
ROCKS
STRONTIUM COMPOUNDS
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