Trace hydrogen zoning in diopside
- Author(s)
- Michael Andrut, Franz Brandstätter, Anton Beran
- Abstract
The trace hydrogen content of a colourless to light-green zoned diopside single-crystal from Zillertal was investigated by IR microspectroscopy. The light-green part of the crystal reveals pleochroic OH absorption bands centred at 3645, 3463, and 3358 cm-1 which are attributed to structural OH defects. The OH absorptions of the colourless crystal part are characterised by weak bands at 3645 and 3662 cm-1 and by a strong band at 3676 cm-1. The bands at 3662 and 3676 cm-1 are attributed to the presence of amphibole lamellae. The analytical water content due to the structural OH defect concentration of the light-green crystal part amounts to 0.0016 wt.%, that of the colourless part is lowered by a factor of about 50. According to optical absorption spectra, the light-green colour of the crystal is essentially caused by an Fe2+ -Fe3+ charge transfer. The relatively high concentration of OH defects in the light-green crystal part associated with higher Al contents relative to the colourless part suggests that OH is incorporated as "hydrodiopside" component, CaMg(SiAlO5OH). It is concluded that increasing water activity during the crystallisation process causes the formation of amphibole lamellae under consumption of nearly all of the water available in the fluid phase. It is further concluded that the observed hydrogen content of diopside represents a primary incorporation and not the result of late hydrothermal alteration processes.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- Naturhistorisches Museum Wien (NHM), Universität Wien
- Journal
- Mineralogy and Petrology
- Volume
- 78
- Pages
- 231-241
- No. of pages
- 11
- ISSN
- 0930-0708
- DOI
- https://doi.org/10.1007/s00710-002-0226-z
- Publication date
- 2003
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1051 Geology, Mineralogy
- Portal url
- https://ucris.univie.ac.at/portal/en/publications/trace-hydrogen-zoning-in-diopside(6ff0c215-ede4-4458-a084-fcd61ba4c151).html