Beitrag
Tuhualite in a peralkaline rhyolitic ignimbrite from Pantelleria, Italy
Bagiński, Bogusław; Macdonald, Ray; White, John C.; Jeżak, Lidia
European Journal of Mineralogy Volume 30 Number 2 (2018), p. 367 - 373
31 Literaturangaben
veröffentlicht: Aug 20, 2018
Online veröffentlicht: Jan 10, 2018
Manuskript akzeptiert: Nov 22, 2017
Manuskript-Revision erhalten: Nov 22, 2017
Manuskript erhalten: Aug 3, 2017
Abstract
An occurrence of the rare mineral tuhualite (NaFe3+Fe2+Si6O15) is reported in a peralkaline rhyolitic ignimbrite from the island of Pantelleria, Italy. The mineral formed during devitrification of glassy fiamme and varies in form from anhedral plates to perfectly euhedral in open vesicles. There is significant replacement of Fe2+ by Mn (≤0.37 atoms per formula unit (apfu)) and Zn (≤0.11 apfu), and of Na by K (≤0.13 apfu). The tuhualite possibly formed at temperatures <580 °C at fO2>FMQ in the presence of a hydrous fluid.
Schlagworte
tuhualite: peralkaline ignimbrite • Pantelleria • compositional variation • conditions of formation