Multicomponent diffusion and convection in molten MgO-Al{sub 2}O{sub 3}-SiO{sub 2}

Journal Article · Mon Jun 01 04:00:00 EDT 1998 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(98)00123-9· OSTI ID:651178

Richter, F M ^[1]; Liang, Y ^[1]; Minarik, W G ^[2]

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1. Univ. of Chicago, IL (United States). Dept. of Geophysical Sciences
2. Lawrence Livermore National Lab., CA (United States). Inst. for Geophysics and Planetary Physics

Multicomponent diffusion and convection in molten MgO-Al{sub 2}O{sub 3}-SiO{sub 2} at 1,550 C and 0.5 GPa were examined experimentally in diffusion couples formed around 22.5 (wt%) MgO, 17.5% Al{sub 2}O{sub 3}, and 60% SiO{sub 2}. The diffusion matrix obtained from a simultaneous least squares inversion of convectively stable intersecting chemical diffusion profiles has large off-diagonal terms indicating, for example, very strong coupling of the flux of SiO{sub 2} with gradients in MgO. In contrast to an earlier report on multicomponent diffusion involving the same compositions studied here, the authors found no features along the stable diffusion profiles that could not be explained in terms of a 2 x 2 diffusion matrix. X-ray concentration maps of the sectioned diffusion charges showed that double-diffusive convection had occurred in a number of experiments along the direction of constant SiO{sub 2}, even though the more dense melt had been placed below the less dense composition. The occurrence of such double-diffusive fingering instabilities is shown to be consistent with the predictions of linear stability theory.

• Sponsoring Organization: USDOE, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
• DOE Contract Number: FG02-94ER14478; W-7405-ENG-48
• OSTI ID: 651178
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 11 Vol. 62; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ALUMINIUM OXIDES
CONVECTION
DIFFUSION
MAGNESIUM OXIDES
MOLTEN SALTS
SILICON OXIDES