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Title

Application of the QUIlF thermobarometer to the peralkaline trachytes and pantellerites of the Eburru volcanic complex, East African Rift, Kenya.

Department

Geosciences

Document Type

Article

Publication Date

10-2006

Abstract

The Quaternary Eburru volcanic complex in the south-central Kenya Rift consists of pantelleritic trachytes and pantellerites. The phenocryst assemblage in the trachytes is sanidine+fayalite+ferrohedenbergite+aenigmatite±quartz±ilmenite±magnetite± pyrrhotite±pyrite. In the pantellerites, the assemblage is sanidine+quartz+ferrohedenbergite+fayalite+aenigmatite+ferrorichterite+ pyrrhotite±apatite, although fayalite, ferrohedenbergite and ilmenite are absent from more evolved rocks (e.g. with SiO2N71%). QUILF temperature calculations for the trachytes range from 709 to 793 °C and for the pantellerites 668–708 °C, the latter temperatures being among the lowest recorded for peralkaline silicic magmas. The QUILF thermobarometer demonstrates that the Eburru magmas crystallized at relatively low oxidation states (ΔFMQ +0.5 to −1.6) for both trachytes and pantellerites. The trachytes and pantellerites evolved along separate liquid lines of descent, the trachytes possibly deriving from a more mafic parent by fractional crystallization and the pantellerites from extreme fractionation of comenditic magmas.

Journal Title

Lithos

Journal Volume

91

Article Starting Page

109

Article Ending Page

124

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