Tetrahedral substitutions in tourmaline
- Author(s)
- Andreas Ertl, Darell J. Henry, Ekkehart Tillmanns
- Abstract
The Si4+ cation, typically the overwhelming occupant of the tetrahedral site of the tourmaline structure, can be partially replaced by Al3+, B3+, and Be2+. Tetrahedrally coordinated Al (up to ~0.9 [4]Al atom per formula unit, apfu) has been found in different Mg- and/or Fe2+-rich tourmalines from high-temperature aluminous lithologies as well as in Li-rich pegmatites. It is relatively common for Li- and [4]Al-bearing tourmalines to also contain some [4]B. While the highest boron content (~0.8 [4]B apfu) in a natural tourmaline was found in an Al-rich tourmaline (olenite) from the Eastern Alps, Austria, much higher contents of up to ~2.8 apfu have been reported for synthetic Al-rich tourmalines. Natural tourmalines with a higher total Al content (> 7.2 Al apfu) can also contain significant [4]B. The highest verified beryllium content in a tourmaline is still below 100 ppm, but current data show that in pegmatitic tourmaline crystals the Be content is positively correlated with the overall Al content. Therefore Li-rich tourmalines can contain higher Be contents in pegmatites that originated from differentiated granitic magma, than in pegmatites that have evolved as granitic pegmatitic melts from the surrounding country-rocks during decompression.
- Organisation(s)
- Department of Mineralogy and Crystallography
- External organisation(s)
- Louisiana State University, Naturhistorisches Museum Wien (NHM)
- Journal
- European Journal of Mineralogy: an international journal of mineralogy, geochemistry and related sciences
- Volume
- 30
- Pages
- 465-470
- No. of pages
- 6
- ISSN
- 0935-1221
- DOI
- https://doi.org/10.1127/ejm/2018/0030-2732
- Publication date
- 04-2018
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105116 Mineralogy, 105113 Crystallography, 105120 Petrology
- Keywords
- ASJC Scopus subject areas
- Geochemistry and Petrology
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/172f8e59-7194-45a8-b52c-9dc1fc54bccf