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Metamorphic rocks of an intermediate facies series juxtaposed at the Start boundary, southwest England

Published online by Cambridge University Press:  01 May 2009

D. Robinson
D. Robinson
Affiliation:
Department of Geology Queen's BuildingUniversity WalkBristol BS8 1TR, England
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Summary

X-ray diffraction analysis of metamorphic rocks from the Start peninsula shows that the dominant mineral assemblage in the Start schists is quartz-muscovite-chlorite ± paragonite ± albite. The assemblage in the Devonian phyllites to the north of the Start boundary is quartz-muscovite-chlorite and the crystallinity of the white mica there is indicative of greenschist fades. The b0 parameter of white micas indicates that the metamorphism was of an intermediate facies series (Barrovian type), but of a lower pressure variety to the north of the Start boundary juxtaposed against a higher pressure variety to the south. No evidence exists of the high pressure metamorphism needed to support tectonic models in which the Start boundary is identified as a suture representing a Variscan subduction margin.

Type
Articles
Information
Geological Magazine , Volume 118 , Issue 3 , May 1981 , pp. 297 - 301
Copyright
Copyright © Cambridge University Press 1981

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