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Feldspar relations in Icelandic alkalic rhyolites

Published online by Cambridge University Press:  05 July 2018

Haraldur Sigurdsson
Haraldur Sigurdsson*
Affiliation:
Dept. of Geology, The University of Durham1
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Summary

Alkalic rhyolites with peralkaline affinities, bearing quartz and potassic feldspar phenocrysts, are described from Iceland for the first time. Evidence from electron-probe analyses of feldspar phenocrysts indicates crystallization in or near the thermal valley of the system SiO2-Or-Ab. Icelandic acid volcanic rocks are subdivided into alkalic rhyolites, belonging to transitional and alkalic basalt lineages, and the mildly calc-alkaline rhyolites of tholeiite lineages.

Type
Research Article
Information
Mineralogical Magazine , Volume 38 , Issue 296 , December 1971 , pp. 503 - 510
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1971

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Footnotes

1

Present address: Seismic Research Unit, University of the West Indies, St. Augustine, Trinidad.

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