The Ballachulish Igneous Complex and aureole: a field guide

by David R.M. Pattison and Ben Harte

(University of Calgary, Canada, T2N 1N4; The University of Edinburgh, Scotland, EH9 3JW)

2001, Edinburgh Geological Society

Published by Edinburgh Geological Society c/o BGS, Murchison House, West Mains Road, Edinburgh EH9 3LA

First published in 2001

All rights reserved. No part of this publication may be reproduced. sorted in a retrieval system. or transmitted, in any form or by any means, electronic. mechanical, photocopying, recording or otherwise, without the prior permission of the Edinburgh Geological Society.

ISBN 0 904440 117 © Edinburgh Geological Society

Bibliographic reference: Pattison. D.R.M. and Hark:, B. The Ballachulish Igneous Complex and Aureole: A Field Guide (Edinburgh: Edinburgh Geological Society)

Printed in Great Britain by Bell Bain Ltd.. Glasgow

The Maps indicated as Figures 8b, 9b. 10b. 11b. 12b. 13b are reproduced from the Ordnance Survey map by permission of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office, © Crown Copyright ED 274720.

(Front cover) Cover photograph. View looking east from the summit of Sgorr Dhonuill to Sgorr Dhearg. The ridge in the foreground is underlain by granite  of the Ballachulish Igneous Complex. The summit of Sgorr Dhearg, is underlain by white Appin Quartzite or the host Dalradian metasediments. On the left skyline is Ben Nevis and the peaks the Mamore range.

Contents

Part 1 – Setting and summary of geology

Introduction

The SW Scottish Highlands and the development of geological studies

Regional setting of the Ballachulish Igneous Complex

The Ballachulish Igneous Complex and the 'Newer' Granites

Host rocks to the Ballachulish Igneous Complex

Stratigraphy

Structure

Regional metamorphism

The Ballachulish Igneous Complex

The Ballachulish aureole

Metapelites

Siliceous carbonates and quartzites

Cause and duration of contact metamorphism

Fluid movement in the aureole

Illustrations of exposures and rocks in literature

Part 2 - The five days of field excursions

Summary of the field excursions

Logistics

Weather and hill conditions - equipment

Hammering and sampling

Forestry roads and vehicular access

Maps and grid references

Excursion for Day 1 — Overview of the Ballachulish Igneous Complex, Dalradian host rocks, and contact hornfelses

Excursion for Day 2 — Rock types and intrusive relationships of the igneous complex

Excursions for day 3

Day 3, Part 1 — Fraochaidh prograde sequence

Day 3, Part 2 — Chaotic Zone migmatites

Excursions for day 4

Excursion for Day 4 — Prograde sequence in the Ballachulish Slate along the Gleann a' Fhiodh – Coire Chaorann ridge; appinitc and quartz diorite relations; migmatitcs and Crd+Grt+Opx hornfelses

Excursions for day 5

Excursion for Day 5 — Medium- to high-grade pelitic and talc-silicate hornfelses, marbles; migmatites, including 'chocolate-tablet' type; summit(s) of Beinn a' Bheithir.

Acknowledgements

We acknowledge Forest Enterprise, and in particular Donald Hendry, for advice on paths and roads through the Glen Duror Forest and for much logistical assistance. Stefan Weiss suggested the Day 2 traverse and provided abundant additional advice and factual information, in addition to compiling and hand-drafting the original map that became the basis for the Coloured Map (Map 1) in the back pocket. Gerard White showed much skill and wizardry in handling computer graphics to compile the Coloured Map (Map 1) and prepare the other maps in this guide. The Edinburgh Geological Society and Moray Endowment Fund (University of Edinburgh) provided grants in support of the publication of this guide book.