Sodium-potassium interdiffusion in potassium-rich alkali feldspar I
- Author(s)
- Elena Petrishcheva, Rainer Abart, Anne-Kathrin Schäffer, Gerlinde Habler, Dieter Rhede
- Abstract
Anisotropic diffusion is described by a tensor of diffusivities, D
αβ, which may be composition dependent leading to nonlinear anisotropic diffusion. In this work the practical problem of reconstructing such a tensor for Na-K interdiffusion in potassium-rich alkali feldspar in the composition range 0.85 ≤ X
Or ≤ 1.00 is addressed. Gem quality sanidine with an initial composition of X
Or = 0.85 was exchanged with KCl salt melt at 850°C and ≈1 bar. The diffusivity tensor D
αβ(X
Or) and its composition dependence was reconstructed from composition profiles produced by cation exchange in six different crystallographic directions using a generalization of the Boltzmann approach. Na-K interdiffusion in potassium-rich alkali feldspar is considerably anisotropic and composition dependent. The principal axes of the diffusivity tensor representing the directions of highest and lowest diffusivity lie in the a-c plane with highest diffusivity parallel to the [101] direction, lowest diffusivity perpendicular to the (101) plane, and the direction with intermediate diffusivity parallel to the crystallographic b-axis. All diffusivities D
αβ(X
Or) increase as X
Or tends to unity. Our main result is given in the form of numerical values for all components of the D
αβ(X
Or) tensor for 0.85 ≤ X
Or ≤ 1.
- Organisation(s)
- Department of Lithospheric Research
- External organisation(s)
- Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum
- Journal
- American Journal of Science: an international earth science journal
- Volume
- 314
- Pages
- 1284-1299
- No. of pages
- 16
- ISSN
- 0002-9599
- DOI
- https://doi.org/10.2475/09.2014.02
- Publication date
- 11-2014
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105116 Mineralogy, 105120 Petrology
- Keywords
- ASJC Scopus subject areas
- General Earth and Planetary Sciences
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/03136636-4dc1-44f9-b00f-82f7a73ba761