The Ben Nevis intrusive ring tuff, Scotland; re-interpretation of the "flinty crush rock" as part of an ignimbrite conduit in the roots of an ancient caldera

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doi: 10.1144/sjg33020149
Authors:Burt, R. M.; Brown, P. E.
Author Affiliations:Primary:
University of St. Andrew, Department of Geology, Fife, United Kingdom
Other:
University of Canterbury, New Zealand
Volume Title:Scottish Journal of Geology
Source:Scottish Journal of Geology, Vol.33(Part 2), p.149-155. Publisher: Scottish Academic Press, Edinburgh, United Kingdom. ISSN: 0036-9276
Publication Date:1997
Note:In English. 29 refs.; illus., incl. geol. sketch map
Summary:Intermittently exposed around the margins of the Ben Nevis volcanic pile is a thin (<5m) rhyolite with a well developed magmatic flow foliation that includes rock previously described as "flinty crush rock". Previous models for the development of this "flinty crush rock" suggested that it developed as a result of intense mechanical shearing during subsidence of the volcanic pile into the underlying Inner Granite. New field, petrographic and geochemical evidence presented here, indicate that the "flinty crush rock" is magmatic and part of a larger body of flow-foliated rhyolite that represents the remains of an ignimbrite conduit formed during caldera collapse. Post-eruption closure of the conduit imposed a well developed flow-foliation on the rhyolite destroying any primary pyroclastic textures. The rhyolite is compositionally identical to a small outcrop of amphibole-biotite Inner Granite, suggesting an intimate and probably co-genetic relationship between flow-foliated rhyolite and Inner Granite magmas. It is recommended that the term "flinty crush rock" be abandoned and replaced by "Ben Nevis Intrusive Ring Tuff". This unit affords a rare opportunity to examine a ring fracture conduit associated with a caldera-forming eruption. [R.A.H.]
Subjects:Calderas; Complexes; Geochemistry; Igneous rocks; Ignimbrite; Interpretation; Petrography; Petrology; Pyroclastics; Revision; Rhyolites; Volcanic features; Volcanic rocks; Europe; Great Britain; Scotland; United Kingdom; Western Europe; Ben Nevis Tuff; Volcanic piles
Abstract Numbers:98M/1938
Record ID:1998022765
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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