The Field Description of Metamorphic Rocks, Second Edition
This pocket-sized field guide describes how metamorphic rocks and rock masses may be observed, recorded and mapped in the field. Written at a level suitable for Earth Science undergraduate students, this book is an essential tool for any geologist - student, professional or amateur - faced with the task of making a general description of an area of metamorphic rocks. A clear, systematic framework, together with numerous colour diagrams, illustrations and checklists, enables readers with different backgrounds to produce useful descriptions, despite possible differences of background or specialist interest. Additional information is also provided to aid those who are undertaking field mapping courses or must compile field evidence into reports on the metamorphic evolution of a region. This book:
- Shows the reader how to observe metamorphic rocks in the field, from the outcrop to the hand specimen scale
- Is fully revised and updated to incorporate new developments in the field
- Offers a user-friendly and accessible writing style including a revised format with tabbed sections for easy navigation
- Covers key topics including classification and mapping of metamorphic rocks, understanding key textures and fabrics, and details on contacts and fault zones
Table of Contents
Preface vii
Acknowledgments ix
1 Introduction and Occurrence 1
1.1 The Importance of Fieldwork in Metamorphic Terrains 1
1.2 Understanding Metamorphism; Pressure/Temperature Relationships 4
1.3 Mode of Occurrence of Metamorphic Bodies 4
1.4 Summary 13
2 Field Skills and Mapping Outcrop Structures 17
2.1 Equipment 17
2.2 Preparing Maps and Basic Mapping 19
2.3 Notebooks and Data Recording 20
2.4 Digital 3D Outcrop Mapping 33
3 Metamorphic Minerals, Rock Types, and Classification 37
3.1 Minerals 37
3.2 The Basic Classification of Metamorphic Rocks in P-T 46
3.3 Metamorphic Rock Names 48
3.4 Reporting Rock Types 50
3.5 Compositional Category and Metamorphic Grade 54
4 Understanding Textures and Fabrics 1: Banding, Cleavage, Schistosity, and Lineations 67
4.1 General Terminology 67
4.2 Rocks without a Metamorphic Directional Fabric 71
4.3 Banding 71
4.4 The Development of Fabric, Cleavage, Schistosity, and Lineations 79
4.5 Refraction, Kinking, and Shearing of Fabrics 88
4.6 Deformation Fabrics and Folds 89
5 Understanding Textures and Fabrics 2: Metamorphic Crystals, Pseudomorphs, and Scattered Entities 95
5.1 Recording Metamorphic Textures 95
5.2 Metamorphic Crystal Growth and Porphyroblasts 97
5.3 Boudins, Shear Pods, and Knockers 109
6 Contacts, Reaction Zones, and Veins 115
6.1 Igneous Contacts - Aureoles and Metasomatism 115
6.2 Veins and Pegmatites 124
6.3 Reaction Zones and Chemical Changes at Contacts 130
7 Faults, Mylonites, and Cataclasites 137
7.1 Fault and Shear Zone Types 137
7.2 Faults and Fault Breccias 138
7.3 Cataclasites and Pseudotachylites 141
7.4 Mylonites and Shear Zones 144
8 Summary Tables, Checklists, and Mapping Report Advice 151
8.1 Compositional Categories and Their Grade Indicators 151
8.2 Minerals 157
8.3 Further Mapping Advice; Formations, Markers, and a Final Report 164
Checklist of Rock Features 171
Further Reading Suggestions 173
Index 175
