Sodium-potassium interdiffusion in potassium-rich alkali feldspar I

Autor(en)

Elena Petrishcheva, Rainer Abart, Anne-Kathrin Schäffer, Gerlinde Habler, Dieter Rhede

Abstrakt

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(en)

Department für Lithosphärenforschung

Externe Organisation(en)

Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum

Journal

American Journal of Science: an international earth science journal

Band

314

Seiten

1284-1299

Anzahl der Seiten

16

ISSN

0002-9599

DOI

https://doi.org/10.2475/09.2014.02

Publikationsdatum

11-2014

Peer-reviewed

Ja

ÖFOS 2012

105116 Mineralogie, 105120 Petrologie

Schlagwörter

ASJC Scopus Sachgebiete

Allgemeine Erdkunde und Planetologie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/03136636-4dc1-44f9-b00f-82f7a73ba761