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Resetting of the Rb–Sr whole-rock isotope system of an Ordovician microgranite during Devonian low-grade metamorphism

Published online by Cambridge University Press:  01 May 2009

J. A. Evans
J. A. Evans
Affiliation:
NERC Isotope Geology Centre, 64 Gray's Inn Road, London WCIX 8NG, U.K.
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Abstract

The Bwlch y Cywion microgranite intrudes an Ordovician sedimentary sequence in northeast Snowdonia, North Wales. Its age is recorded by hornfelses within its metamorphic aureole which give an Ordovician age of 454 ± 20 Ma. The whole-rock Rb–Sr isotope systems of the intrusion, however, and of an associated ash-flow tuff and a rhyolite of the Llewelyn Volcanic Group (Caradoc), were reset during low-grade metamorphism and give Devonian ages of 392±11 Ma, 392±5 Ma, and 405 ± 6 Ma, respectively.

Type
Articles
Information
Geological Magazine , Volume 126 , Issue 6 , November 1989 , pp. 675 - 679
Copyright
Copyright © Cambridge University Press 1989

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