Diffusion in single crystals of melilite: 2. Cations
- Univ. of Tokyo Yayoi (Japan)
- Gakushiun Univ. Mejiro, Tokyo (Japan)
Diffusion coefficients of divalent cations, Ni, Co, Fe, Mn, Ca, Sr, and Ba, in synthetic akermanite were determined by tracer-diffusion experiments. Diffusion coefficients of cation paris, Al + Al-Mg + Si, Al + Al-Co + Si, and Mg-Co in melilite solid-solution systems, were determined by coupled annealing of synthetic melilites of endmember compositions. Cobalt tracer diffuses slower along the c-crystallographic axis than along the a-axis by a factor of about three, possibly due to the anisotropic sheet-like arrangement of oxygen ions parallel to the (001) plane which is perpendicular to the c-axis in the crystal structure of melilite. In the coupled diffusion experiments, the cation pairs interdiffuse complementary, as expected for conservation of material and ionic charge balance in the substitution. The observed trend in the inter-diffusion coefficient vs. melting temperature relations is similar to those observed for alloys and consistent with an empirical rule for self-diffusion coefficient-melting temperature relation. In the diffusion coefficient vs. ionic radius diagram for divalent cation diffusion in akermanite, smooth curves were observed as in the case of olivine systems. However, the shapes of the curves were significantly different from those observed in olivine systems. The observed trend of diffusion coefficients with ionic radius can be explained on the basis of crystal structure-controlled diffusion in akermanite.
- OSTI ID:
- 5979030
- Journal Information:
- Geochimica et Cosmochimica Acta; (United States), Vol. 55:3; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
OLIVINE
CRYSTAL STRUCTURE
ANNEALING
BARIUM IONS
CALCIUM COMPOUNDS
CALCIUM IONS
CHEMICAL COMPOSITION
CHONDRITES
COBALT IONS
DIFFUSION
ELECTRON-ION COUPLING
GEOCHEMISTRY
IRON IONS
MANGANESE IONS
MOLECULAR STRUCTURE
NICKEL IONS
PERMEABILITY
RECRYSTALLIZATION
SOLID SOLUTIONS
STRONTIUM IONS
STRUCTURAL CHEMICAL ANALYSIS
ALKALINE EARTH METAL COMPOUNDS
CHARGED PARTICLES
CHEMISTRY
COUPLING
DISPERSIONS
HEAT TREATMENTS
IONS
METEORITES
MINERALS
MIXTURES
SILICATE MINERALS
SOLUTIONS
STONE METEORITES
580000* - Geosciences