Potassium and sodium self-diffusion in alkali feldspar

✍ Scribed by T. -H. Lin; R. A. Yund

• Publisher: Springer
• Year: 1972
• Tongue: English
• Weight: 562 KB
• Volume: 34
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00373289

✦ Synopsis

The rate of potassium self-diffusion in pure mierocline was measured between 600 ~ and 800 ~ C using K *~ as a tracer. Transport of K 4~ by processes other than volume diffusion was insignificant or minimal. Isotropic diffusion coefficients were calculated assuming spheriea[ grains. The data are well fit by the Arrhenius relation and yield a pre-exponential factor (Do) of 133.8 em2/sec and an activation energy (Q) of 70 keal/mole. Similar experiments on the self-diffusion of Na 22 in a pure low-albite (exchanged microeline) yield D o of 2.31 x 10 -e cm2/see and Q of approximately 19 kcal/mole for the temperature interval from 200 ~ to 600 ~ C. The large difference in these activation energies suggests that the atomic mechanisms for sodium and potassium diffusion are different.