Dougal Jerram - The Field Description of Metamorphic Rocks

1 Cover

2 Series Page The Geological Field Guide Series Field Hydrogeology, Fourth edition Rick Brassington Drawing Geological Structures Jörn H. Kruhl Field Hydrogeology, Third edition Rick Brassington Basic Geological Mapping, Fifth edition Richard J. Lisle, Peter Brabham, and John W. Barnes The Field Description of Igneous Rocks, Second edition Dougal Jerram and Nick Petford Sedimentary Rocks in the Field, Fourth edition Maurice E. Tucker Field Geophysics, Fourth edition John Milsom and Asger Eriksen Field Geophysics, Third edition John Milsom

3 Title Page 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

4 Copyright Page

5 PREFACE – THE FIELD DESCRIPTION OF METAMORPHIC ROCKS Preface – Meet the Authors

6 ACKNOWLEDGMENTS

7 1 INTRODUCTION AND OCCURRENCE 1.1 The Importance of Fieldwork in Metamorphic Terrains 1.2 Understanding Metamorphism; Pressure/Temperature Relationships 1.3 Mode of Occurrence of Metamorphic Bodies 1.4 Summary

8 2 FIELD SKILLS AND MAPPING OUTCROP STRUCTURES 2.1 Equipment 2.2 Preparing Maps and Basic Mapping 2.3 Notebooks and Data Recording 2.4 Digital 3D Outcrop Mapping

9 3 METAMORPHIC MINERALS, ROCK TYPES, AND CLASSIFICATION 3.1 Minerals 3.2 The Basic Classification of Metamorphic Rocks in P‐T 3.3 Metamorphic Rock Names 3.4 Reporting Rock Types 3.5 Compositional Category and Metamorphic Grade

10 4 UNDERSTANDING TEXTURES AND FABRICS 1 4.1 General Terminology 4.2 Rocks without a Metamorphic Directional Fabric 4.3 Banding 4.4 The Development of Fabric, Cleavage, Schistosity, and Lineations 4.5 Refraction, Kinking, and Shearing of Fabrics 4.6 Deformation Fabrics and Folds

11 5 UNDERSTANDING TEXTURES AND FABRICS 2 5.1 Recording Metamorphic Textures 5.2 Metamorphic Crystal Growth and Porphyroblasts 5.3 Boudins, Shear Pods, and Knockers

12 6 CONTACTS, REACTION ZONES, AND VEINS 6.1 Igneous Contacts – Aureoles and Metasomatism 6.2 Veins and Pegmatites 6.3 Reaction Zones and Chemical Changes at Contacts

13 7 FAULTS, MYLONITES, AND CATACLASITES 7.1 Fault and Shear Zone Types 7.2 Faults and Fault Breccias 7.3 Cataclasites and Pseudotachylites 7.4 Mylonites and Shear Zones

14 8 SUMMARY TABLES, CHECKLISTS, AND MAPPING REPORT ADVICE 8.1 Compositional Categories and Their Grade Indicators 8.2 Minerals 8.3 Further Mapping Advice; Formations, Markers, and a Final Report SUMMARY TABLES, CHECKLISTS, AND MAPPING REPORT ADVICE

15 FURTHER READING SUGGESTIONSGeneral helpful texts (including books that have helped inspire us with this revised edition): Advanced reading –good research papers and reviews that cover both field & laboratory-based studies integrated with theoretical frameworks

16 Index

17 End User License Agreement

1 Chapter 3Table 3.1 An overview of the key rock types formed from the major protolith ...Table 3.2 Some metamorphic rocks and the most diagnostic minerals associated ...Table 3.3 Some fine‐grained rock types (colours indicate protolith see tabl ...

2 Chapter 4Table 4.1 Suggested procedure for describing banded rocks.

3 Chapter 5Table 5.1 List of common pseudomorph minerals.

4 Chapter 7Table 7.1 The classification of fault associated rock types.

5 Chapter 8Table 8.1 An overview of the key rock types formed from the major protolith ...Table 8.2 Main mineral constituents of some compositional categories at diff ...Table 8.3 Main mineral groups and other common bulk minerals. Table 8.4 ‘Metamorphic minerals’, often as grains embedded in bulk minerals. ...Table 8.5 Accessory minerals’, bearing minor chemical components. Table 8.6 Summary of main rock types and minerals.

1 Chapter 1 Figure 1.1 Schematic of the plate tectonic settings where metamorphism is oc ... Figure 1.2 The P/T diagram: (a) the classic fields of metamorphism of mafic ... Figure 1.3 The classic Barrovian Zones of regional metamorphism first descri ... Figure 1.4 Examples of classic (Barrovian) regional metamorphic rocks Figure 1.5 (a) Blueschist facies, Syros, Greece (Mark Caddick for scale) wit ... Figure 1.6 Highly folded metamorphic carbonate turbidites, Namibia Figure 1.7 Contact metamorphism. (a) schematic of contacts around a granite ... Figure 1.8 Serpentinised ocean crust from the Troodos Ophiolite, Cyprus. A f ... Figure 1.9 Summary of the two main types of tectonic settings with an outlin ...

2 Chapter 2 Figure 2.1 Be prepared! Picture of field kit; hard hat, compass clinometer, ... Figure 2.2 Example of a simple but effective start of day layout. Figure 2.3 Example of a field notebook with an outline sketch of an outcrop.... Figure 2.4 Example of a field notebook with outcrop sketch and closer sketch ... Figure 2.5 Examples of small, detailed, texture sketches Figure 2.6 Example of a field notebook with synoptic sketch Figure 2.7 Example of a graphic log highlighting a banded meta‐gabbro sequen ...Figure 2.8 Detailed lithostratigraphic log of metamorphic units found south ...Figure 2.9 Some of the common mapping symbols used in metamorphic terrains ...Figure 2.10 Detailed map sketch within a notebook Figure 2.11 Example of a metamorphic map of part of the Isle of Syros, Greec ...Figure 2.12 Example of contact relationships within a complex terrain, inclu ...Figure 2.13 (a) The process of mapping outcrops in 3D using a drone. The cor ...Figure 2.14 3D outcrop model of large folds in metamorphic calc‐schists, NW ...

3 Chapter 3Figure 3.1 Generalised mineral occurrences and compatibilities in the typica ...Figure 3.2 Examples of pillow structures within basic igneous protoliths at ...Figure 3.3 Sillimanite in two forms: (a) Folded fibrolitic sillimanite from ...Figure 3.4 Vein containing white calcite (CaCO3) crystals that have orange‐b ...Figure 3.5 (a) High‐pressure metamorphic pyroxene, with green colour due to ...Figure 3.6 (a) A version of the classic metamorphic facies diagram, showing ...Figure 3.7 Characteristics of various protolith types upon heating Figure 3.8 (a) Apparent lawsonite crystals at the outcrop scale. A thin sect ...Figure 3.9 Stabilities of the Al2SiO5 polymorphs (aluminium silicates). (a) ...Figure 3.10 (a) A P‐T grid showing possible reactions experienced by pelitic ...Figure 3.11 The Barrovian sequence can be deceptive! This staurolite, garnet ...Figure 3.12 The compositions of key minerals in mafic, pelitic, and calc‐sil ...Figure 3.13 Notebook example where a triangular diagram has been drawn to he ...Figure 3.14 Reactions between contrasting compositional portions of a rock c ...Figure 3.15 Representative rocks of the Barrovian sequence, and their approx ...Figure 3.16 Reactions between contrasting compositional portions of a rock c ...Figure 3.17 A schematic PT grid showing the three major reactions associated...

4 Chapter 4Figure 4.1 Banded rocks of the Greenland Banded orthogneiss in contact with ...Figure 4.2 Examples of compositional complexities. (a) Small en‐echelon vein ...Figure 4.3 Later cross‐cutting examples. (a) An early intrusion into a parag ...Figure 4.4 Examples of types of banding. (a) Deformed, quartz‐rich segregati