Chemical diffusion in melts on the CaMgSi sub 2 O sub 6 -CaAl sub 2 Si sub 2 O sub 8 join under high pressures

Journal Article · Mon Oct 01 04:00:00 EDT 1990 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(90)90006-7· OSTI ID:6162194

Kubicki, J D; Muncill, G E ^[1]; Lasaga, A C ^[2]

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1. Carnegie Institution of Washington, DC (USA)
2. Yale Univ., New Haven, CT (USA)

This study was designed to obtain data on the rates of chemical diffusion between melt couples of diopside to Di{sub 40}An{sub 60} composition and to determine changes in diffusion rates with temperature and pressure. Chemical diffusion in melts along the joint diopside-anorthite can be described as binary (i.e., compositions remain on the join in the diffusion zone) up to a difference of 20 wt% between melt couple compositions. For larger concentration differences, multicomponent diffusion matrices should be calculated. The diagonal elements of these matrices are similar to the effective binary diffusion coefficients determined from the binary diffusion equation, but the off-diagonal terms are of the same order of magnitude and cannot be neglected. Pressures up to 20 kbars do not change the diffusion coefficients significantly, although a diffusivity maximum may exist near 10 kbars. Activation energies for MgO and Al{sub 2}O{sub 3} diffusion are consistent with a mechanism of individual ionic species diffusing through the melt.

• OSTI ID: 6162194
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 54:10; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
580000* -- Geosciences
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ENERGY
FELDSPARS
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IGNEOUS ROCKS
KINETICS
MAGMA
MAGMATISM
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OXYGEN COMPOUNDS
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PETROGENESIS
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SILICATES
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THERMODYNAMIC MODEL
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VOLCANIC ROCKS