Hydrogen diffusion in natural and synthetic orthopyroxene |
| |
| Authors: | R Stalder H Skogby |
| |
| Institution: | 1.Naturhistoriska riksmuseet, Sektionen f?r mineralogi, Box 50007, 10405 Stockholm, Sweden e-mail: rstalde@gwdg.de Tel.: +49-551-393886 Fax: +49-551-393863,SE |
| |
| Abstract: | Hydrogen diffusion coefficients in natural orthopyroxenes and synthetic enstatite were determined by dehydration and hydration
experiments at 700 and 900 °C. In natural Opx (approximately En90Fs10) small but significant differences in diffusivities along the three crystallographic axes were observed, 001] being the
fastest direction, followed by 100] and 010]. Hydrogen diffusion in pure enstatite proved to be about 2 orders of magnitude
slower and isotropic. The activation energy for hydrogen diffusion in pure enstatite was determined to be −295 (±55) kJmol−1, and −213 (±47) kJmol−1 for orthopyroxene from Kilbourne Hole. Long-term hydration experiments did not lead to saturation in hydrogen. Instead, after
an initial increase in hydrogen concentration, a slow but continuing decrease could be observed in all cases. It is suggested
that the investigated samples lose their ability to store hydrogen even when heated in a hydrogen atmosphere. This loss in
storage ability can itself be described by a diffusion equation, its diffusion coefficients being more than 1 order of magnitude
slower than the diffusion of hydrogen.
Received: 22 February 2002 / Accepted: 18 October 2002 |
| |
| Keywords: | Enstatite Hydrogen diffusion Infrared spectroscopy |
| 本文献已被 SpringerLink 等数据库收录！ |
|
