The Field Description of Metamorphic Rocks. Dougal Jerram

Third edition John Milsom

The Field Description of Metamorphic Rocks

      SECOND EDITION

      Dougal Jerram

       Centre for Earth Evolution & Dynamics, University of Oslo, Norway

       DougalEARTH Ltd, Solihull, UK

      Mark Caddick

       Virginia Tech

       Blacksburg, VA, USA

This edition first published 2022 © 2022 John Wiley & Sons Ltd

      Edition History John Wiley & Sons Ltd (1e, 2013)

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       Library of Congress Cataloging‐in‐Publication Data

      Names: Jerram, Dougal, author.

      Title: The field description of metamorphic rocks / Dougal Jerram, Centre for Earth Evolution & Dynamics, University of Oslo, Norway, DougalEARTH Ltd, Solihull, UK, Mark Caddick, Virginia Tech, Blacksburg, VA.

      Description: Second edition. | Hoboken, NJ : Wiley, 2022. | Series: The geological field guide series | Revised edition of: The field description of metamorphic rocks / Norman Fry. 1984. | Includes bibliographical references and index.

      Identifiers: LCCN 2021052480 (print) | LCCN 2021052481 (ebook) | ISBN 9781118618752 (paperback) | ISBN 9781118618691 (adobe pdf) | ISBN 9781118618677 (epub)

      Subjects: LCSH: Metamorphic rocks–Handbooks, manuals, etc.

      Classification: LCC QE475.A2 F79 2022 (print) | LCC QE475.A2 (ebook) | DDC 552/.4–dc23/eng/20211204

      LC record available at https://lccn.loc.gov/2021052480 LC ebook record available at https://lccn.loc.gov/2021052481

      Cover design: Wiley

      Cover image: Courtesy of Susanne Schmid

PREFACE – THE FIELD DESCRIPTION OF METAMORPHIC ROCKS

      In many regards, metamorphic rocks represent some of the most complicated challenges that you will find in the field. They were obviously once igneous, sedimentary, or even different metamorphic rocks, and you may be able to interpret some of this early history at the outcrop. But they have subsequently been changed through combinations of pressure, temperature, and reaction with fluid so that they might now look radically different to their original form. In order to understand these changes (the rock’s metamorphosis), and to some extent the original ‘parent’ rock, the field description of metamorphic rocks requires careful observation and a grasp of many aspects of the broader range of the geosciences. It is not enough just to know how to identify key metamorphic minerals in the field: multidisciplinary skills borrowed from other branches of field geology, and even engineering, are increasingly essential requirements for the modern metamorphic geologist.

      This concise guide is designed to give students, professionals, and keen amateur geoscientists the key tools needed to help understand and interpret the origin and evolution of complex metamorphic systems in a focused way, while in the field. This extensively revised and reorganised colour guide builds on Norman Fry’s original version, published in 1984 as part of the (then) Geological Society of London Field Guide Series. Since 1984, much has changed in the scientific community’s understanding of metamorphic processes and in the ways that fieldwork is conducted. Accordingly, we have tried in this first colour revision to incorporate much of this newer thinking and methodology. At the same time, we have aimed to remain true to the original philosophy of a portable guide that concisely explains the basic concepts underpinning the field description of metamorphic rocks. Indeed, we have kept and built on some sections of Fry’s original text. The original version was necessarily limited by its black and white printing, and we have enjoyed updating the figures in this version: almost every figure in the original book has been replaced here or reproduced in colour. We hope that the inclusion of the new colour images and a simple, colour‐coded index system will help the reader to navigate their way through the different types, grades, and origins of metamorphic rocks. Both authors grew up with the original versions of the Geological Field Guide Series and one of us (Dougal) was even taught by Norman Fry at Cardiff University. So it has been a great pleasure, if not a long journey, to revise this field handbook, now published as part of Wiley Blackwell’s ‘Geological Field Guide Series’. We hope you find this new guide a great companion and an essential aid when confronted, perhaps for the first time, with metamorphic rocks in the field.

       Dougal Jerram and Mark Caddick 2021

Preface – Meet the Authors

      Dougal holds a 20% research professorship at the University of Oslo and is the director of DougalEARTH Ltd. He is primarily a field geologist and has undertaken fieldwork all over the world and experienced a wide range of Earth’s geology and landscapes from Africa to Antarctica. He started his geological career in the UK, where he cut his teeth on the many fundamental outcrops the UK has to offer through a