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Pyrometamorphic breakdown of cordierite - muscovite intergrowths

Published online by Cambridge University Press:  05 July 2018

R. H. Grapes
R. H. Grapes*
Affiliation:
Institut für Mineralogie, Petrologie und Geochemie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg, Germany
*
* E-mail: [email protected]
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Abstract

Backscattered electron imaging of cordierite-muscovite intergrowths near the margin of a schist xenolith in trachytic tephra of the Wehr Volcano, East Eifel area, Germany, show that they have undergone disequilibrium melting to form spinel + biotite + sillimanite/?mullite + peraluminous melt. Textures indicate that in the initial stage of reaction, spinel, biotite and sillimanite/?mullite formed with melt produced in cordierite and spinel + ?mullite with melt after muscovite, providing evidence of two different reaction pathways. Fe-Mg distributions between biotite/spinel, cordierite/spinel, cordierite/ biotite suggest a melting temperature of ∼770°C, implying overstepping of various calculated and experimentally determined mineral breakdown curves of between 30 and 170°C during short-term heating before the xenolith was quenched on eruption.

Keywords

pyrometamorphismcordieritemuscoviteWehr volcanoGermany.
Type
Research Article
Information
Mineralogical Magazine , Volume 67 , Issue 4 , August 2003 , pp. 653 - 663
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2003

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