Igneous and Metamorphic Petrology

by Best, Myron G.

• ISBN13: 9781405105880
• ISBN10: 1405105887
• Edition: 2nd
• Format: Paperback
• Copyright: 2002-12-13
• Publisher: Wiley-Blackwell

Summary

Igneous and metamorphic petrology has over the last twenty years expanded rapidly into a broad, multifaceted and increasingly quantitative science. Advances in geochemistry, geochronology, and geophysics, as well as the appearance of new analytical tools, have all contributed to new ways of thinking about the origin and evolution of magmas, and the processes driving metamorphism.This book is designed to give students a balanced and comprehensive coverage of these new advances, as well as a firm grounding in the classical aspects of igneous and metamorphic petrology. The emphasis throughout is on the processes controlling petrogenesis, but care is taken to present the important descriptive information so crucial to interpretation. One of the most up-to-date synthesis of igneous and metamorphic petrology available. Emphasis throughout on latest experimental and field data. Igneous and metamorphic sections can be used independently if necessary.

Author Biography

Myron G. Best is Professor Emeritus at Brigham Young University, is a Fellow of the Geological Society of America, and a member of the American Geophysical Union.

Table of Contents

Preface
Overview of Fundamental Concepts
Energy and the Mantle Heat Engine	2	(8)
Forms of Energy	2	(1)
Flow and Transformation of Energy	3	(1)
Heat Flow in the Earth	3	(5)
Implications of Mantle Convection	8	(1)
Energy Budget of the Earth	9	(1)
Gravity, Pressure, and Geobaric Gradient	10	(1)
Rock-Forming Processes as Changing States of Geologic Systems	10	(1)
Rock Properties and Their Significance	11	(3)
Composition	12	(1)
Field Relations	13	(1)
Fabric	14	(1)
How Petrologists Study Rocks	14	(2)
Composition and Classification of Magmatic Rocks
Analytical Procedures	16	(6)
Sampling	16	(1)
Analyses	17	(5)
Mineral Composition of Magmatic Rocks	22	(1)
Glass	22	(1)
Chemical Composition of Magmatic Rocks	23	(2)
Variation Diagrams	23	(1)
Continuous Spectrum of Rock Compositions	24	(1)
Classification of Magmatic Rocks	25	(12)
Classification Based on Fabric	27	(1)
Classification Based on Field Relations	27	(1)
Classification Based on Mineralogical and Modal Composition	28	(2)
Classification Based on Whole-Rock Chemical Composition	30	(5)
Rock Suites	35	(2)
Classification of Basalt	37	(1)
Trace Elements	37	(7)
Partition Coefficients and Trace Element Compatibility	38	(2)
Rare Earth Elements	40	(2)
Other Normalized Trace Element Diagrams	42	(2)
Isotopes	44	(7)
Stable Isotopes	44	(1)
Radiogenic Isotopes	45	(2)
Cosmogenic Isotopes: Beryllium	47	(4)
Thermodynamics and Kinetics: An Introduction
Why Is Thermodynamics Important?	51	(1)
Elementary Concepts of Thermodynamics	52	(4)
Thermodynamic States, Processes, and State Variables	52	(1)
First Law of Thermodynamics	53	(1)
Enthalpy	53	(1)
Entropy and the Second and Third Laws of Thermodynamics	54	(1)
Gibbs Free Energy	55	(1)
Stability (Phase) Diagrams	56	(3)
Slope of the Melting Curve	57	(1)
Determination of Phase Diagrams	58	(1)
Thermodynamics of Solutions: Some Basic Concepts	59	(2)
Components and Mole Fractions	59	(1)
Partial Molar Volume	59	(1)
Partial Molar Gibbs Free Energy: The Chemical Potential	60	(1)
P-T-X Phase Diagram	61	(1)
Application of Thermodynamics to Solutions	61	(5)
Fugacity and Activity	61	(1)
Equilibrium Constants	62	(1)
Silica Activity, Silica Buffers, and Silica Saturation	63	(1)
Oxygen Buffers	64	(2)
Fe-Ti Oxide Buffers: Oxygen Geobarometers and Geothermometers	66	(1)
Kinetics	66	(6)
Activation Energy	67	(1)
Overstepping and Metastable Persistence and Growth	68	(4)
Silicate Melts and Volatile Fluids in Magma Systems
Nature of Magma	72	(3)
Atomic Structure of Melts	73	(2)
Volatile Fluids in Melts	75	(5)
Nature of Volatiles	75	(1)
Solubilities of Volatiles in Silicate Melts	76	(3)
Exsolution of Volatiles from a Melt	79	(1)
Consequences of Fluid Exsolution from Melts	80	(7)
Explosive Volcanism	80	(2)
Global Atmosphere and Climate	82	(2)
Fumaroles, Hydrothermal Solutions, Ore Deposits, and Geothermal Reservoirs	84	(3)
Crystal-Melt Equilibria in Magmatic Systems
Phase Diagrams	87	(2)
Phase Rule	87	(2)
Melting of a Pure Mineral and Polymorphism	89	(1)
Volatile-Free Equilibria	89	(1)
Melting of a Pure Mineral in the Presence of Volatiles	89	(1)
Phase Relations in Binary Systems	90	(8)
Basic Concepts: CaMgSi2O6 (Di)-CaAl2Si2O8 (An) System at P = 1 atm	90	(3)
Mg2SiO4-SiO2 System at 1 atm	93	(5)
Crystal-Melt Equilibria in Real Basalt Magmas	98	(2)
Makaopuhi Basalt	98	(1)
Basalt Magmas at High Pressures and High Water Concentrations	99	(1)
Feldspar-Melt Equilibria	100	(12)
KAlSi3O8 (Kf)-CaAl2Si2O8 (An) Binary System: Limited Solid Solution	100	(1)
NaAlSi3O8 (Ab)-CaAl2Si2O8 (An) Binary Plagioclase System: Complete Solid Solution	101	(1)
NaAlSi3O8 (Ab)-KAlSi3O8 (Kf) Binary Alkali Feldspar System	102	(2)
KAlSi3O8 (Kf)-NaAlSi3O8 (Ab)-CaAl2Si2O8 (An) Ternary Feldspar System	104	(4)
KAlSi3O8 (Kf)-NaAlSi3O8 (Ab)-SiO2 (silica)-H2O: The Granite System	108	(4)
Crystal-Melt Equilibria Involving Anhydrous Mafic Minerals: Olivine and Pyroxene	112	(1)
Crystal-Melt Equilibria in Hydrous Magma Systems	113	(4)
Equilibria in the Granodiorite-Water System	113	(1)
Equilibria Involving Melt and Micas and Amphiboles	114	(3)
Geothermometers and Geobarometers	117	(1)
Assessing States of Equilibrium in Rocks	117	(1)
A Brief Comment Regarding Subsolidus Reactions in Magmatic Rocks	118	(4)
Chemical Dynamics of Melts and Crystals
Viscosity of Melts	122	(4)
Chemical Diffusion	126	(4)
Types of Diffusion	126	(1)
Theory and Measurement	127	(1)
Factors Governing Diffusivities	128	(1)
Average Diffusion Distance	129	(1)
Soret Diffusion	129	(1)
Diffusion of Heat	130	(1)
The Role of Body Shape on Conductive Cooling	131	(1)
Interfacial Energy	131	(2)
Crystallization	133	(6)
Why Is It Important to Study Nucleation and Crystallization?	133	(1)
Nucleation	133	(2)
Crystal Growth	135	(2)
Crystal Size in Magmatic Rocks	137	(2)
Secondary Overprinting Processes Modifying Primary Crystal Size and Shape	139	(3)
Crystal Dissolution	139	(1)
Textural Equilibration: Grain Boundary Modification	140	(2)
Vesiculation and Fragmentation of Magma	142	(9)
Nucleation and Growth of Bubbles---Vesiculation	142	(3)
Melt Fragmentation and Explosive Volcanism	145	(6)
Kinetic Paths and Fabric of Magmatic Rocks
Fabrics Related to Crystallization Path: Crystallinity and Grain Size	151	(7)
Glassy Texture	151	(2)
Aphanitic Texture	153	(2)
Phaneritic Texture	155	(2)
Porphyritic Texture	157	(1)
Poikilitic and Ophitic Textures	158	(1)
Fabrics Related to Crystallization Path: Grain Shape	158	(2)
Fabrics Related to Crystallization Path: Inhomogeneous Grains	160	(2)
Zoned Crystals	160	(1)
Reaction Rims	160	(1)
Subsolidus Decomposition and Exsolution in Unstable Minerals	161	(1)
Fabric Related to Textural Equilibration: Secondary Grain-Boundary Modification	162	(1)
A Word of Caution on the Interpretation of Crystalline Textures	163	(2)
Magmatic Rock Texture and Order of Crystallization	163	(2)
Fabrics Related to Nonexplosive Exsolution of Volatile Fluids	165	(1)
Volcaniclastic Fabrics Related to Fragmentation of Magma	166	(5)
Pyroclastic Processes	167	(2)
Autoclastic Processes	169	(2)
Fabrics Related to Consolidation of Volcaniclasts into Solid Rock	171	(1)
Anisotropic Fabrics	171	(10)
Descriptive Geometric Aspects	171	(4)
Origin	175	(6)
Inclusions	181	(2)
Physical and Thermal Dynamics of Bodies of Magma
Stress and Deformation	183	(3)
Concepts of Stress	183	(1)
Deformation	184	(1)
Ideal Response to Stress	185	(1)
Rheology of Rocks and Magmas	186	(8)
Rheology of Rocks	187	(3)
Non-Newtonian Rheology of Magma	190	(1)
Deformation and Flow of Magma	191	(3)
Density of Magma and Buoyancy	194	(3)
Density Determinations	194	(1)
Densities of Minerals and Melts	195	(1)
Buoyancy	196	(1)
Conductive Heat Transfer	197	(2)
Conductive Cooling Models	198	(1)
Advective Heat Transfer	199	(2)
Magma Convection	201	(9)
Thermal Convection in a Completely Molten Body of Melt	201	(2)
Thermochemical Convection in Crystallizing Magmas	203	(2)
Replenishment in Evolving Magma Chambers	205	(5)
Magma Ascent and Emplacement: Field Relations of Intrusions
Movement of Magma in the Earth	210	(3)
Neutral Buoyancy and the Crustal Density Filter	210	(2)
Magma Overpressure	212	(1)
Mechanisms of Magma Ascent	213	(1)
Sheet Intrusions (Dikes)	213	(9)
Description and Terminology	213	(3)
Some Thermomechanical Concepts Pertaining to Emplacement of Sheet Intrusions	216	(2)
Geometry and Orientation of Sheet Intrusions	218	(2)
Basalt Diking in Extensional Regimes	220	(2)
Diapirs	222	(2)
Magma Emplacement in the Crust: Providing the Space	224	(17)
Some Aspects of Granitic Plutons	225	(1)
Emplacement Processes and Factors	226	(10)
The Intrusion--Host Rock Interface	236	(5)
Magma Extrusion: Field Relations of Volcanic Rock Bodies
Overview of Extrusion: Controls and Factors	241	(4)
Moving Magma to the Surface: What Allows Extrusion	242	(1)
Two Types of Extrusions: Explosive and Effusive	242	(3)
Effusions of Basaltic Lava	245	(9)
Types of Basaltic Lava Flows	245	(4)
Columnar Joints	249	(1)
Subaerial Lava Accumulations	250	(2)
Submarine Basaltic Accumulations	252	(2)
Effusions of Silicic Lava	254	(5)
Morphological Characteristics and Growth	254	(2)
Internal Fabric	256	(3)
Explosive Eruptions	259	(19)
Explosive Mechanisms: Production of Pyroclasts	259	(3)
Pyroclasts in Volcanic Plumes	262	(1)
Pyroclast Transport and Deposition	262	(5)
Explosive Style	267	(3)
Pyroclastic Flows and Deposits: Overview	270	(1)
Block-and-Ash Flows	271	(1)
Ignimbrite-Forming Ash Flows	271	(4)
Calderas	275	(2)
Subaqueous Pyroclastic Flows	277	(1)
Other Volcaniclastic Deposits	278	(5)
Epiclastic Processes and Deposits	278	(1)
Volcanic Debris Flows: Lahars	278	(1)
Composite Volcanoes	279	(4)
Generation of Magma
Melting of Solid Rock: Changes in P, T, and X	283	(5)
Temperature Increase, +ΔT	284	(2)
Decompression, -ΔP	286	(1)
Changes in Water Concentration, +ΔXwater	287	(1)
Mantle Source Rock	288	(7)
Mantle-Derived Inclusions	289	(2)
Metasomatized and Enriched Mantle Rock	291	(4)
Generation of Magma in Mantle Peridotite	295	(5)
Equilibrium (Batch) Partial Melting of Lherzolite	295	(2)
Fractional Partial Melting of Lherzolite	297	(1)
Factors Controlling Partial Melt Composition	297	(2)
Modeling Partial Melting Using Trace Elements	299	(1)
Characteristics of Primary Magma	300	(1)
Magma Generation in Subarc Mantle Wedge	300	(6)
Dehydration of Subducting Oceanic Crust	301	(2)
Magma Generation in the Mantle Wedge	303	(2)
Partial Melting of Subducted Basaltic Oceanic Crust: Adakite	305	(1)
Generation of Alkaline Magmas in Metasomatically Enriched Mantle Peridotite	306	(2)
The Metasomatized Mantle Connection	307	(1)
Magma Generation in the Continental Crust	308	(9)
Partial Melting of Continental Source Rocks	309	(2)
``Alphabet'' Granitic Magmas: Contrasting Sources	311	(1)
Crystalline Residues	312	(1)
Melt Segregation	313	(1)
Felsic Magma Generation and the Mantle Connection	313	(4)
Differentiation of Magmas
Using Variation Diagrams to Characterize Differentiation Processes	317	(1)
Closed-System Magmatic Differentiation	318	(7)
Crystal-Melt Fractionation	318	(4)
Physical Separation of Immiscible Melts	322	(2)
Fluid-Melt Separation: Pegmatites	324	(1)
Open-System Differentiation: Hybrid Magmas	325	(4)
Magma Mixing	325	(3)
Assimilation	328	(1)
Differentiation in Basaltic Intrusions	329	(9)
Palisades Sill	329	(2)
Layered Intrusions	331	(6)
Oceanic-Ridge Magma Chambers	337	(1)
Origin of the Calc-Alkaline Differentiation Trend	338	(11)
Tonga--Kermadec--New Zealand Arc	339	(1)
Factors Controlling Development of the Calc-Alkaline Trend	339	(10)
Magmatic Petrotectonic Associations
Oceanic Spreading Ridges and Related Basaltic Rocks	349	(5)
Mid-Ocean Ridge Basalt (MORB)	350	(3)
Iceland	353	(1)
Mantle Reservoirs	354	(1)
Mantle Plumes and Oceanic Island Volcanic Rocks	354	(10)
Character of Volcanic Rocks	356	(3)
Hawaiian Islands: Tholeiitic and Alkaline Associations	359	(3)
Highly Alkaline Rocks on Other Oceanic Islands	362	(2)
Plume Heads and Basalt Flood Plateau Lavas	364	(6)
Oceanic Plateaus	364	(1)
Continental Flood Basalt Plateaus	365	(4)
Continental Breakup	369	(1)
Arc Magmatism: Overview	370	(1)
Oceanic Island Arcs	371	(5)
Rock Associations	372	(2)
Magma Evolution	374	(1)
Back-Arc Basins	375	(1)
Ophiolite	376	(1)
Characteristics	376	(1)
Origin and Emplacement	377	(1)
Calc-Alkaline Continental Margin Magmatic Arcs	377	(9)
Volcanic Arcs on Continental Margins	378	(4)
Plutonic Arcs on Continental Margins: Granitic Batholiths	382	(4)
Granites in Continent-Continent Collision Zones	386	(1)
Anorogenic A-Type Felsic Rocks	387	(3)
Characteristics	388	(1)
Petrogenesis	389	(1)
Anorogenic Ring Complexes in Nigeria and Niger	390	(1)
Granites and Granites	390	(2)
Continental Rift Associations: Bimodal and Alkaline Rocks	392	(5)
Transitions from Continental Arc to Rift Associations in Western North America	394	(1)
Magmatism in the East African Rift System	395	(2)
Alkaline Orphans, Mostly in Stable Cratons	397	(8)
Lamprophyres	398	(1)
Lamproite, Orangeite, and Kimberlite Clans	398	(7)
Metamorphic Rocks and Metamorphism: An Overview
Examples of Equilibration in Metamorphic Rocks	405	(19)
Incipient Metamorphism: Crystallization of New Minerals and Preservation of Relict Protolith Fabrics	405	(5)
Recrystallization under Hydrostatic Conditions: Newly Imposed Granoblastic Fabric	410	(4)
Recrystallization under Nonhydrostatic States of Stress: Tectonite Fabric	414	(7)
Crystalloblastic Series	421	(1)
Metasomatism	422	(2)
The Nature of Metamorphism	424	(17)
The Nature of the Protolith	424	(2)
Types of Metamorphism Based on Metamorphic Conditions	426	(1)
Geologic Field Settings: Metamorphic Terranes	426	(4)
Metamorphic Grade	430	(1)
Metamorphic Zones	431	(5)
Intensive Variables and Stable Mineral Assemblages	436	(1)
Metamorphic Facies	437	(1)
Metamorphic Facies Series	438	(1)
Metamorphic Field Gradients and P--T--t Paths	438	(3)
Why Study Metamorphic Rocks? Metamorphic Petrology and Continental Evolution and Tectonics	441	(6)
Petrography of Metamorphic Rocks: Fabric, Composition, and Classification
Metamorphic Fabrics	447	(8)
Anisotropic Fabrics of Tectonites	448	(4)
Summary List of Metamorphic Textures	452	(3)
Classification and Description of Metamorphic Rocks	455	(11)
Metamorphic Rock Names Based on Fabric	455	(1)
Strongly Foliated Rocks	456	(1)
Weakly Foliated Rocks	457	(3)
Nonfoliated Mafic Rocks	460	(1)
Nonfoliated High-Grade Felsic Rocks	461	(1)
Other Nonfoliated Metamorphic Rocks	462	(1)
Serpentinite	463	(2)
Metasomatic Rock Types	465	(1)
Misfits	465	(1)
High-Strain-Rate Rocks in Fault and Shear Zones	465	(1)
Veins	466	(1)
Graphical Representation of Mineral Assemblages in Composition Diagrams	466	(8)
Fundamentals	466	(1)
Examples of Composition Diagrams in Hypothetical Three-Component Systems	467	(2)
Compatibility Diagrams for Metamorphic Rocks	469	(5)
Metamorphic Mineral Reactions and Equilibria
Equilibrium Mineral Assemblages	474	(1)
Overview of Metamorphic Mineral Reactions	475	(1)
Polymorphic Transitions	475	(4)
The Al2SiO5 System	476	(3)
Net Transfer Solid--Solid Reactions	479	(5)
Basic Relations in a System of Pure End-Member Phases	479	(2)
Model Reactions in the Basalt--Granulite--Eclogite Transition	481	(3)
Continuous Reactions Between Crystalline Solid Solutions	484	(4)
Solid Solution in the Continuous Net Transfer Reaction Plagioclase = Jadeitic Clinopyroxene + Quartz	485	(1)
Continuous Exchange Reactions in Fe--Mg Solid Solutions	485	(3)
Solid--Fluid Mineral Reactions	488	(10)
Fluids in the Crust of the Earth	488	(3)
Fundamental Concepts of Solid--Fluid Reactions	491	(2)
Equilibria with Mixed-Volatile Fluids	493	(2)
Local versus External Control of Fluid Composition during Devolatilization Reactions	495	(3)
Fluid Flow During Metamorphism of the Continental Crust	498	(6)
Evidence for Fluid Flow	498	(2)
Mechanics of Fluid Flow	500	(4)
Metasomatism	504	(4)
Ion Exchange Reactions in Open Metasomatic Systems	504	(1)
The Thompson Model of Metasomatic Zoning and Local Equilibrium	505	(1)
Low-Variance Assemblages in Metasomatic Rocks	506	(1)
Frames of Reference and the Isocon Diagram	506	(2)
Redox Mineral Equilibria	508	(1)
Kinetics and Mineral Reactions: What Actually Happens in Metamorphic Rocks	509	(2)
Role of Fluids in the Mechanism of Metamorphic Reactions	509	(2)
Putting Mineral Equilibria to Work: Broader Petrologic Implications	511	(10)
Isograds	511	(2)
Evaluation of Intensive Variables during Metamorphism	513	(1)
Mineral Thermobarometers	514	(7)
Evolution of Imposed Metamorphic Fabrics: Processes and Kinetics
Solid-State Crystallization Under Static Conditions	521	(7)
Nucleation and Growth	522	(2)
Equilibration of Grain Size and Shape	524	(2)
Intragrain Textural Features	526	(2)
Ductile Flow	528	(15)
Diffusive Creep	529	(3)
Intracrystalline Plastic Deformation	532	(6)
Crystal Defects	538	(3)
Recovery during Dislocation Creep	541	(1)
Hydrolytic Weakening of Silicates during Plastic Slip	541	(2)
Power Law in Ductile Flow	543	(1)
Interactions Between Deformation, Crystallization, and Fluids in Tectonites	543	(12)
Role of Fluids in Tectonite Fabric Development	545	(1)
Timing of Deformation and Crystallization: Larger Scale Implications	545	(1)
Pre-, Syn-, and Postkinematic Fabrics	546	(3)
Polymetamorphism	549	(2)
Shear-Sense Indicators	551	(3)
Patterns of Deformation and Flow: Tectonic Significance of Fabric Geometry	554	(1)
Origin of Anisotropic Fabric in Metamorphic Tectonites	555	(10)
Preferred Dimensional Orientation of Mineral Grains	556	(1)
Preferred Orientation of Crystal Lattices in Tectonites	556	(2)
Cleavage, Schistosity, and Compositional Layering	558	(7)
Metamorphism at Convergent Plate Margins: P--T--t Paths, Facies, and Zones
P--T--t Paths	565	(4)
Thermal Considerations	565	(1)
Petrologic Determination of P--T--t Paths	566	(3)
A Brief Anatomical Overview of Metamorphism in Orogens	569	(7)
Specific Regional Metamorphic Terranes	570	(6)
Intermediate- to Low-P Metamorphic Zones and Facies	576	(13)
Pelitic Rocks in Typical Barrovian Zones at Intermediate Pressures	576	(6)
P--T--t Paths and Chronology of Barrovian Metamorphism	582	(1)
Buchan Metamorphism	583	(4)
Mineral Assemblages in Mafic Protoliths: A Brief Overview	587	(1)
Metabasites at Intermediate Pressures	587	(2)
Ocean-Ridge Metamorphism	589	(3)
Petrology of Metamorphosed Seafloor Rocks	590	(2)
Intact Slabs of Ophiolite	592	(2)
Near-Trench Metamorphic Associations	594	(7)
The Franciscan Complex, California	594	(1)
Melange	594	(2)
Serpentinite	596	(1)
Subgreenschist Facies Rocks	597	(2)
Metabasites at High Pressures	599	(1)
P--T--t Paths and Tectonic Evolution of High P/T Terranes	600	(1)
Ultrahigh-P Metamorphic Rocks	601	(11)
Coesite and Diamond: Diagnostic UHP Minerals	602	(1)
Dora Maira Massif in the Western Alps	603	(2)
Dabie--Sulu Terrane	605	(1)
Evolution of UHP Terranes	606	(6)
Precambrian Rock Associations
The Young Earth---A Brief Overview	612	(1)
Archean Granitoid--Greenstone Terranes	613	(10)
General Character of Greenstone Belts	614	(3)
Itsaq Gneiss Complex, West Greenland: Earliest Record of Crustal Process at 3900--3600 Ma	617	(3)
Kaapvaal Craton	620	(1)
Yilgarn Craton	621	(1)
Superior Province	622	(1)
Archean Volcanic Rocks	623	(10)
Komatiite	623	(6)
Basalts	629	(1)
Archean Megacrystic Anorthosite	630	(2)
Other Volcanic Rocks in Greenstone Belts	632	(1)
Archean Granitoids	633