Wonchi volcano (Ethiopia) is the second locality for wilkinsonite, the new mineral related to aenigmatite via the coupled substitution 2Fe3+ = TiFe2+. Wilkinsonite occurs as relics surrounded by rims of riebeckite and biotite in a syenitic ejectum which also contains microphenocrysts of aenigmatite. The two minerals do not represent an equilibrium pair. They both formed in the magma chamber under plutonic to hypabyssal conditions, but during two following stages of crystallisation separated by a major drop in f(o2) conditions.
PHASE-RELATIONS OF AENIGMATITE MINERALS IN A SYENITIC EJECTUM, WONCHI VOLCANO, ETHIOPIA / Gaeta, Mario; A., Mottana. - In: MINERALOGICAL MAGAZINE. - ISSN 0026-461X. - 55:(1991), pp. 529-534. [10.1180/minmag.1991.055.381.05]
PHASE-RELATIONS OF AENIGMATITE MINERALS IN A SYENITIC EJECTUM, WONCHI VOLCANO, ETHIOPIA
GAETA, Mario;
1991
Abstract
Wonchi volcano (Ethiopia) is the second locality for wilkinsonite, the new mineral related to aenigmatite via the coupled substitution 2Fe3+ = TiFe2+. Wilkinsonite occurs as relics surrounded by rims of riebeckite and biotite in a syenitic ejectum which also contains microphenocrysts of aenigmatite. The two minerals do not represent an equilibrium pair. They both formed in the magma chamber under plutonic to hypabyssal conditions, but during two following stages of crystallisation separated by a major drop in f(o2) conditions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
