Matrix glass and melt inclusions in phenocrysts from pantellerite lavas of the Boseti volcanic complex, Ethiopia, record extreme fractionation of peralkaline silicic magma, with Al 2O 3 contents as low as 2.3 wt.%, FeO* contents up to 17 wt.% and SiO 2 contents ~65 wt.%. The new data, and published data for natural and experimental glasses, suggest that the effective minimum composition for peralkaline silicic magmas has ~5 wt.% Al 2O 3, 13 wt.% FeO* and 66 ± 2 wt.% SiO 2. The dominant fractionating assemblage is alkali feldspar + fayalite + hedenbergite + oxides ± quartz. Feldspar - melt relationships indicate that the feldspar is close to the minimum on the albite-orthoclase solid solution loop through the entire crystallization history. There is petrographic, mineralogical and geochemical evidence that magma mixing may have been a common process in the Boseti rhyolites. © 2011 The Author(s).
Evidence for extreme fractionation of peralkaline silicic magmas, the Boseti volcanic complex, Main Ethiopian Rift / Ray, Macdonald; Bogusław, Baginski; Fiorenzo, Ronga; Piotr, Dzierzanowski; Lustrino, Michele; Andrea, Marzoli; Leone, Melluso. - In: MINERALOGY AND PETROLOGY. - ISSN 0930-0708. - STAMPA. - 104:3-4(2012), pp. 163-175. [10.1007/s00710-011-0184-4]
Evidence for extreme fractionation of peralkaline silicic magmas, the Boseti volcanic complex, Main Ethiopian Rift
LUSTRINO, Michele;
2012
Abstract
Matrix glass and melt inclusions in phenocrysts from pantellerite lavas of the Boseti volcanic complex, Ethiopia, record extreme fractionation of peralkaline silicic magma, with Al 2O 3 contents as low as 2.3 wt.%, FeO* contents up to 17 wt.% and SiO 2 contents ~65 wt.%. The new data, and published data for natural and experimental glasses, suggest that the effective minimum composition for peralkaline silicic magmas has ~5 wt.% Al 2O 3, 13 wt.% FeO* and 66 ± 2 wt.% SiO 2. The dominant fractionating assemblage is alkali feldspar + fayalite + hedenbergite + oxides ± quartz. Feldspar - melt relationships indicate that the feldspar is close to the minimum on the albite-orthoclase solid solution loop through the entire crystallization history. There is petrographic, mineralogical and geochemical evidence that magma mixing may have been a common process in the Boseti rhyolites. © 2011 The Author(s).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.