Diffusion Data for Clinopyroxenes from Homogenization and Self-Diffusion Experiment

Authors

John B. Brady, Smith CollegeFollow
Robert H. McCallister, Purdue University

Document Type

Article

Publication Date

1983

Publication Title

American Mineralogist

Abstract

Kinetic experiments involving the homogenization of fine-scale, coherent (001) pigeonite lamellae in a sub-calcic diopside have been used to constrain Ca-Mg interdiffusion coefficients for clinopyroxenes. At 1150°-1250°C and 25 kbar, "average" Ca-Mg effective binary interdiffusion coefficients are described by

Ď = (3.89 x l0^-7) exp(-360.87 kJ/RT) (m²/sec)

(Ď : (3.89 x l0^-3) exp(-86.25 kcal/RT) (cm²/sec))

with an uncertainty of a factor of 2. Because of the large thermodynamic effect on diffusion near a solvus, actual interdiffusion coefficients should vary by an order of magnitude or more with composition for the conditions of these experiments.Attempts to obtain Ca and Fe self-diffusion coefficients in natural diopsides at 1 atm using ⁴⁵Ca and ⁵⁷Fe tracers and thin-fiIm, autoradiographic techniques were unsuccessful.These negative results place upper bounds on the Ca and Fe self-diffision coefficients in diopside that are consistent with the results of the homogenization experiments.

Volume

68

Issue

(1-2)

First Page

95

Last Page

105

Rights

Copyright © 1983 by the Mineralogical Society of America

Comments

Archived as published, with permission.

Recommended Citation

Brady, John B. and McCallister, Robert H., "Diffusion Data for Clinopyroxenes from Homogenization and Self-Diffusion Experiment" (1983). Geosciences: Faculty Publications, Smith College, Northampton, MA.
https://scholarworks.smith.edu/geo_facpubs/211