Diffusion of Ca, Sr, Ba, and Co in a basalt melt: Implications for the geochemistry of the mantle
Article first published online: 20 SEP 2012
Copyright 1977 by the American Geophysical Union.
Journal of Geophysical Research
Solid Earth and Planets
Volume 82, Issue 33, pages 5432–5440, 10 November 1977
How to Cite
1977), Diffusion of Ca, Sr, Ba, and Co in a basalt melt: Implications for the geochemistry of the mantle, J. Geophys. Res., 82(33), 5432–5440, doi:10.1029/JB082i033p05432., and (
- Issue published online: 20 SEP 2012
- Article first published online: 20 SEP 2012
- Manuscript Accepted: 28 JUN 1977
- Manuscript Received: 22 FEB 1977
Tracer diffusion coefficients of Ca, Sr, Ba, and Co in molten olivine tholeiite basalt have, been determined between 1260° and 1440°C at 1 atm. The diffusion coefficients range from 10−7 to 10−6 cm2 s−1, and the activation energies range from 39 to 44 kcal mol−1. The diffusion coefficients decrease with increasing ionic radius, but the observed relationship does not conform to the Stokes-Einstein relation. The results of our experiments suggest that the characteristic diffusion distances, estimated by the expression (Dt)1/2, exceed 1 km only for very long times of 109 years or more. Consequently, chemical diffusion does not contribute significantly to large-scale differentiation and mixing processes in a partially molten mantle. A layer of 1-km half width that has been depleted in incompatible trace elements (e.g., by extraction of melt) can be replenished by diffusion from the adjacent material to one-half its original concentration in 3×108 years (or 0.9 in 8×109 years). Diffusive transport is efficient in small-scale processes (<1 km). Diffusion in a partially molten asthenosphere greatly increases the rate of local equilibration, and it contributes significantly to small-scale mixing and contamination processes in magma chambers and conduits.