Tetrahedral substitutions in tourmaline: a review

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Marco E. Ciriotti
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Tetrahedral substitutions in tourmaline: a review

Messaggio da Marco E. Ciriotti » lun 26 feb, 2018 11:29

Prossima pubblicazione.

Referenza:
▪ Ertl, A., Henry, D.J., Tillmanns, E. (2018): Tetrahedral substitutions in tourmaline: a review. European Journal of Mineralogy[/i], 30, (in press).
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 24281
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Re: Tetrahedral substitutions in tourmaline: a review

Messaggio da Marco E. Ciriotti » sab 09 giu, 2018 15:56

Referenza:
▪ Ertl, A., Henry, D.J., Tillmanns, E. (2018): Tetrahedral substitutions in tourmaline: a review. European Journal of Mineralogy, 30, (in press).

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.
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