Field Description of Igneous Rocks

Revised by Dr Nicholas Petford, Lecturer at School of Earth Sciences, Kingston University, London, UK.Written by Richard Thorpe (Deceased) and Geoffrey Brown (Deceased).

“The reader will return repeatedly to the excellent sketches and tables throughout the book, and the "how to” sections provide some memorable highlights.”  (PESGB, 1 January 2014)“A second edition of The Field Description of Igneous Rocks has been long overdue, and the authors are to be commended for reproducing an excellent and comprehensively revised version.”  (Geological Journal, 1 January 2013) “Overall, if you are examining igneous rocks in the field or studying an OU course then, yes, I would recommend this book.”  (Open University Geological Society Journal, 1 November 2012)“To be fair, the authors of this book have undertaken an incredibly difficult task. They succeed at reaching the novice audience but fall a bit short when it comes to more experienced mapping geologists.”  (Environmental & Engineering Geoscience, 1 November 2012)"This book is certain to be of use to all geological students and enthusiasts interested in studying igneous geology in the field." (American Mineralogist, 2012) "As a pocket field guide, the book, because of its size, sometimes undersells the fantastic images it contains, but as a whole, it is a welcome, useful resource. Highly recommended. Upper-division undergraduates." (Choice, 1 October 2011)

• Preface xiAcknowledgements xv1 Introduction and Occurrence 11.1 The Importance of Fieldwork 11.2 The Global Picture – Igneous Rocks in Relation to Regional Tectonics 21.3 Mode of Occurrence of Igneous Bodies 41.4 Summary 112 Field Skills and Outcrop Structures 152.1 Equipment 152.2 Preparing Maps and Basic Mapping 162.3 Notebooks and Data Recording 172.4 Primary Outcrop Structures 182.5 Secondary or Late Stage Outcrop Structures 282.6 Outcrop Contact Relationships 322.7 Summary of Igneous Outcrop Descriptions 333 Igneous Textures and Classification 373.1 Describing Rock Types 373.2 Colour and Composition 383.3 Texture, Grain-Size/Shape and Fabric 433.4 Mineral Identification 493.5 Naming and Classification 584 Volcanics 1 – Lava Flows 694.1 Lava Flow Emplacement Mechanisms 694.2 A Compositional Divide for Lava Flows 714.3 Mafic/Basaltic Lava Flows 734.4 Felsic/Silicic Flows 804.5 Pillow Lavas and Hyaloclastites 825 Volcanics 2 – Pyroclastic Rocks 935.1 Structures, Textures and Classification 935.2 Pyroclastic Flows and Ignimbrites 1015.3 Scoria Cones 1085.4 Water/Magma and Sediment/Magma Interactions 1095.5 Epiclastic Deposits 1126 Shallow-Level Intrusions 1196.1 Sill and Dykes 1196.2 Working Out Emplacement History 1246.3 Volcanic Plugs and Diatremes 1306.4 Shallow-Level Subvolcanic Intrusions 1337 Granitic Complexes 1377.1 Introduction 1377.2 General Features and Occurrence 1377.3 Zoned Plutons 1427.4 Internal Structures and Textures 1457.5 Internal Contacts 1507.6 Emplacement Timing 1587.7 Distinctive Granitoid Textures 1627.8 Metamorphic Aureoles 1647.9 Summary of the Field Characteristics of Granitic Complexes 1658 Mafic Complexes 1718.1 General Features and Occurrence 1718.2 Continental Mafic-Ultramafic Intrusions 1738.3 Ophiolite Complexes 1778.4 Komatiites 1838.5 Summary of the Field Characteristics of Mafic-Ultramafic Intrusions 1849 Magma Mixing and Mingling 1899.1 Magma Rheology 1899.2 Magma Mixing 1909.3 Magma Mingling 1929.4 Synplutonic Dykes and Sills 1969.5 Magma Mingling in Subvolcanic and Volcanic Environments 2009.6 Xenoliths 2019.7 A Word of Warning 2029.8 Summary 20310 Mineralisation and Geotechnical Properties 20710.1 Mineralisation and Key Minerals 20710.2 Mineralisation in Layered Mafic Intrusions 20910.3 Geotechnical Properties of Igneous Rocks 21310.4 Rock Mass Classification 21610.5 Summary 226Appendix 229Further Reading 231Index 233