Using Geochemical Data: To Understand Geological Processes

Half title
Reviews
Title page
Imprints page
Contents
Preface to the Second Edition
Preface to the First Edition
Abbreviations
1 Geochemical Data
	1.1 Introduction
	1.2 Geological Processes and Their Geochemical Signatures
		1.2.1 Processes Which Control the Formation and Differentiation of Planetary Bodies
		1.2.2 Processes Which Control the Chemical Composition of Igneous Rocks
			1.2.2.1 Processes Which Take Place in the Mantle Source
			1.2.2.2 Partial Melting Processes
			1.2.2.3 Magma Chamber Processes
			1.2.2.4 Post-solidus Processes
		1.2.3 Processes Which Control the Chemical Composition of Metamorphic Rocks
		1.2.4 Low-Temperature Processes in the Earth’s Surficial Environment
			1.2.4.1 Atmospheric Processes
			1.2.4.2 Weathering Processes
			1.2.4.3 Water Chemistry
			1.2.4.4 The Impact of Human Activity on the Earth’s Surface Environment
		1.2.5 Processes Which Control the Chemical Composition of Sedimentary Rocks
			1.2.5.1 Provenance
			1.2.5.2 Weathering
			1.2.5.3 Processes in the Depositional Environment
		1.2.6 Biogeochemical Processes
			1.2.6.1 The Search for Early Life on Earth
	1.3 Geological Controls on Geochemical Data
		1.3.1 Sample Collection
	1.4 Analytical Methods in Geochemistry
		1.4.1 Sample Preparation
		1.4.2 Sample Dissolution
		1.4.3 X-Ray Fluorescence (XRF)
			1.4.3.1 Wavelength Dispersive X-Ray Fluorescence Spectrometry (WDXRF)
			1.4.3.2 Energy Dispersive X-Ray Fluorescence (EDXRF)
		1.4.4 Instrumental Neutron Activation Analysis (INAA)
		1.4.5 Atomic Absorption Spectrophotometry (AAS)
		1.4.6 Mass Spectrometry
			1.4.6.1 Thermal Ionisation Mass Spectrometry (TIMS)
			1.4.6.2 Gas Source Mass Spectrometry
			1.4.6.3 Laser Fluorination Gas Source Mass Spectrometry
			1.4.6.4 Isotope Dilution Mass Spectrometry
		1.4.7 Inductively Coupled Plasma (ICP) Spectrometry
			1.4.7.1 ICP-Optical Emission Spectrometry (ICP-OES)
			1.4.7.2 ICP-Mass Spectrometry (ICP-MS)
			1.4.7.3 Laser Ablation ICP Mass Spectrometry (LA-ICP-MS)
		1.4.8 Electron Probe Micro-analysis (EPMA)
		1.4.9 The Ion Microprobe (SIMS)
		1.4.10 Synchrotron X-Ray Spectroscopic Analysis
	1.5 Selecting an Appropriate Analytical Technique
	1.6 Sources of Error in Geochemical Analysis
		1.6.1 Contamination
		1.6.2 Calibration
		1.6.3 Peak Overlap
		1.6.4 Detecting Errors in Geochemical Data
2 Analysing Geochemical Data
	2.1 Introduction
	2.2 A Statistical Approach?
		2.2.1 Geochemical Investigation versus Statistical Trials
		2.2.2 Statistical Limitations Associated with Geochemical Data
			2.2.2.1 Constrained or Closed Data and the Constant Sum Problem
			2.2.2.2 Non-uniform Errors (Heteroscedasticity)
			2.2.2.3 Small n
			2.2.2.4 Outliers
		2.2.3 Can We Address These Limitations?
	2.3 Histograms, Averages and Probability Functions
		2.3.1 Histograms
		2.3.2 Averages
		2.3.3 Probability Functions and Kernel Density Estimates
		2.3.4 Cumulative Distribution Function
		2.3.5 Chi-Square (χ2) ‘Goodness of Fit’ Test
	2.4 Correlation
		2.4.1 The Pearson Linear Correlation Coefficient (r)
			2.4.1.1 The Significance of the Correlation Coefficient
			2.4.1.2 Assumptions Associated with the Correlation Coefficient
		2.4.2 Rank Correlation Coefficients
			2.4.2.1 Spearman Rank Correlation
			2.4.2.2 Kendall Rank Correlation
		2.4.3 The Strength of a Correlation
		2.4.4 Correlation and Non-homogeneous Data
		2.4.5 Correlation Matrices
	2.5 Regression Analysis
		2.5.1 Ordinary Least Squares (OLS) Regression
		2.5.2 Orthogonal Regression
		2.5.3 Reduced Major Axis Regression
		2.5.4 Weighted Least Squares Regression
		2.5.5 Robust Regression
		2.5.6 Some Problems with Traditional Approaches to Correlation and Regression
	2.6 Ratio Correlation
		2.6.1 The Improper Use of Ratio Correlation: Pearce Element Ratio Diagrams
		2.6.2 Application to Trace Element Diagrams
		2.6.3 Ratio Correlation in Isotope Geology
	2.7 Compositional Data Analysis
		2.7.1 Aitchison’s Approach to Constrained Compositional Data
		2.7.2 The Biplot
		2.7.3 Some Geochemical Applications of the Log-Ratio Approach
	2.8 Multivariate Data Analysis
		2.8.1 Principal Component and Factor Analysis
		2.8.2 Discriminant Analysis
			2.8.2.1 Limitations of Discriminant Analysis
		2.8.3 Multidimensional Scaling (MDS)
	2.9 Statistics and Ternary Plots
	2.10 Geochemical Data and Statistical Analysis
3 Using Major Element Data
	3.1 Introduction
		3.1.1 Processing Major Element Data
		3.1.2 Major Element Mobility
		3.1.3 The Compositions of Some Major Earth Reservoirs
	3.2 Rock Classification
		3.2.1 Classifying Igneous Rocks Using Oxide-Oxide Plots
			3.2.1.1 The Total Alkalis-Silica Diagram (TAS) for Volcanic Rocks
			3.2.1.2 A TAS Diagram for Plutonic Rocks
			3.2.1.3 Discrimination between the Alkalic and Sub-alkalic Rock Series Using TAS
			3.2.1.4 The K2O versus SiO2 Diagram for the Sub-division of the Sub-alkalic Series
		3.2.2 Classifying Igneous Rocks Using Normative Mineralogy
			3.2.2.1 CIPW Norm
			3.2.2.2 The Cation Norm
			3.2.2.3 Normative Mineralogy and the Oxidation State of Iron
			3.2.2.4 Normative Mineralogy and Basalt Classification
			3.2.2.5 Normative Mineralogy and Granite Classification
		3.2.3 Classifying Igneous Rocks Using Cations
			3.2.3.1 The Jensen Plot
			3.2.3.2 The Hanski Plot
			3.2.3.3 Classification of High-Mg Rocks on the TAS Diagram
		3.2.4 A Combined Major Element Oxide and Cation Classification for Granitoids
		3.2.5 The Chemical Classification of Sedimentary Rocks
			3.2.5.1 Sandstones
			3.2.5.2 Mudrocks
			3.2.5.3 Limestones
		3.2.6 Discussion
	3.3 Variation Diagrams
		3.3.1 Recognising Geochemical Processes on a Major Element Variation Diagram
			3.3.1.1 Fractional Crystallisation
			3.3.1.2 Assimilation and Fractional Crystallisation
			3.3.1.3 Partial Melting
			3.3.1.4 Mixing Lines in Sedimentary Rocks
			3.3.1.5 The Identification of Former Weathering Conditions in Sedimentary Rocks
			3.3.1.6 Artificial Trends
		3.3.2 Selecting a Variation Diagram
			3.3.2.1 Bivariate Plots
			3.3.2.2 Compositional Data and Bivariate Diagrams
			3.3.2.3 So Why Do Bivariate Plots Appear to Work?
		3.3.3 Ternary Diagrams
			3.3.3.1 The AFM Diagram
		3.3.4 Interpreting Trends on Variation Diagrams
			3.3.4.1 Extract Calculations
			3.3.4.2 Addition–Subtraction Diagrams
			3.3.4.3 Limitations to the Application of Extract Calculations
			3.3.4.4 Trends Showing an Inflection
			3.3.4.5 Scattered Trends
		3.3.5 Modelling Major Element Processes in Igneous Rocks
			3.3.5.1 Modelling Fractional Crystallisation
			3.3.5.2 Modelling Fractional Crystallisation and Assimilation
	3.4 Diagrams on Which Rock Chemistry and Experimentally and Thermodynamically Determined Phase Boundaries Are Plotted Together
		3.4.1 Melting the Mantle
			3.4.1.1 The Yoder and Tilley CIPW Normative Tetrahedron
			3.4.1.2 CMAS Diagrams
			3.4.1.3 FeO–MgO Plots
		3.4.2 Melting Mafic Crust
		3.4.3 Melting Felsic (Continental) Crust
			3.4.3.1 The Normative Albite–Orthoclase–Quartz Diagram: The ‘Granite System’
			3.4.3.2 Partial Melting of Crustal Rocks
		3.4.4 What Melted?
			3.4.4.1 The Aluminium Saturation Index (ASI)
			3.4.4.2 Al–Fe–Mg–Ti–Ca Diagrams
4 Using Trace Element Data
	4.1 Introduction
		4.1.1 The Classification of Trace Elements According to Their Geochemical Behaviour
			4.1.1.1 Trace Element Groupings in the Periodic Table
			4.1.1.2 Trace Element Behaviour in Magmatic Systems
			4.1.1.3 Trace Elements of Economic Significance
	4.2 Physical Controls on Trace Element Distribution
		4.2.1 Partition Coefficients
			4.2.1.1 Measuring Partition Coefficients
			4.2.1.2 Calculating Partition Coefficients Using Lattice Strain Theory
			4.2.1.3 Physical Controls on the Value of Partition Coefficients in Mineral-Melt Systems
			4.2.1.4 Selecting an Appropriate Partition Coefficient
			4.2.1.5 Partition Coefficients in Basalts
			4.2.1.6 Partition Coefficients in Andesites
			4.2.1.7 Partition Coefficients in Dacites and Rhyolites
			4.2.1.8 Partition Coefficients in Accessory Minerals
		4.2.2 Geological Controls on the Distribution of Trace Elements
			4.2.2.1 Element Mobility
			4.2.2.2 Partial Melting
			4.2.2.3 Crystal Fractionation
			4.2.2.4 Sedimentary Processes
	4.3 The Rare Earth Elements (REE)
		4.3.1 The Chemistry of the REE
		4.3.2 Presenting REE Data
			4.3.2.1 Difficulties with Chondrite Normalisation
			4.3.2.2 Choosing a Set of Normalising Values
			4.3.2.3 REE Ratio Diagrams
			4.3.2.4 Shale Normalisation for Sediments
			4.3.2.5 Rock Normalisation
		4.3.3 Interpreting REE Patterns
			4.3.3.1 REE Patterns in Igneous Rocks
			4.3.3.2 REE Patterns in Seawater and River Water
			4.3.3.3 REE Patterns in Sediment
	4.4 Normalised Multi-element Diagrams or Incompatible Element Diagrams
		4.4.1 Multi-element Diagrams for Igneous Rocks
			4.4.1.1 Chondrite-Normalised Multi-element Diagrams
			4.4.1.2 Primordial (Primitive) Mantle Normalised Multi-element Diagrams
			4.4.1.3 MORB-Normalised Multi-element Diagrams
			4.4.1.4 Interpreting Multi-element Diagrams for Igneous Rocks
		4.4.2 Multi-element Diagrams for Clastic Sediments
	4.5 Diagrams Displaying Highly Siderophile Elements (HSE) and Platinum Group Elements (PGE)
		4.5.1 The Application of the HSE in Cosmochemistry
		4.5.2 The Application of the HSE in Mantle Geochemistry
	4.6 Bivariate Trace Element and Trace Element Ratio Plots
		4.6.1 The Selection of Trace Elements to Plot on Bivariate Graphs for Igneous Rocks
			4.6.1.1 The Behaviour of the Highly Incompatible Elements
			4.6.1.2 Estimation of Partition Coefficients from Trace Element Concentration Plots
			4.6.1.3 Identification of Igneous Source Characteristics from Incompatible Element Ratio Plots
			4.6.1.4 Some Important Trace Element Ratios
			4.6.1.5 Applications to Felsic Rocks
			4.6.1.6 Compatible Element Plots
		4.6.2 Bivariate Plots in Sedimentary Rocks
	4.7 Enrichment–Depletion Diagrams
	4.8 Modelling Trace Element Processes in Igneous Rocks
		4.8.1 Vector Diagrams
		4.8.2 Modelling on Multivariate Diagrams
			4.8.2.1 Partial Melting
			4.8.2.2 Crystal Fractionation
			4.8.2.3 Crustal Contamination and AFC Processes
			4.8.2.4 Open System Processes
			4.8.2.5 Magma and Source Mixing
		4.8.3 Inversion Techniques Using Trace Elements
			4.8.3.1 Inverting Mineral Compositions to Estimate the Composition of a Melt
			4.8.3.2 Inverting Melt Compositions to Estimate the Melting Process and the Nature of the Source
		4.8.4 A Final Comment on Geochemical Modelling
5 Using Geochemical Data to Identify Tectonic Environments
	5.1 Introduction
		5.1.1 Tectonic Environments
		5.1.2 The Current Approach to Discrimination Diagrams
		5.1.3 Immobile Trace Elements
		5.1.4 Using Discrimination Diagrams
	5.2 Elemental Discrimination Diagrams for Ultramafic and Mafic Volcanic Rocks
		5.2.1 Nb/Y–Ti/Y, NbN–ThN, and Ce, Dy, Yb Diagrams
		5.2.2 Ti/Y–Zr/Y
		5.2.3 Ti/1000–V
		5.2.4 Zr–Ti
		5.2.5 Na/100–25Nb–Sr
		5.2.6 Si/1000–Ti/40–Sr
		5.2.7 100Eu–500Lu–Sr
		5.2.8 V–Ti/50–5Sc
		5.2.9 50Sm–Ti/50–V
		5.2.10 Th–Hf/3–Ta
		5.2.11 La/10–Y/15–Nb/8
		5.2.12 Major Elements
		5.2.13 TiO2, Zr, Y, Sr
		5.2.14 TiO2, Nb, V, Y, Zr
	5.3 Elemental Discrimination Diagrams for Intermediate Volcanic Rocks
	5.4 Elemental Discrimination Diagrams for Acid Plutonic Rocks
		5.4.1 The Yb–Ta and Y–Nb Discrimination Diagrams
		5.4.2 Major Element Diagrams
		5.4.3 Some Words of Caution
	5.5 Discrimination Diagrams for Clastic Sediments
		5.5.1 A Discrimination Diagram for Sand-Sized Clastic Sediment
		5.5.2 Discrimination Diagrams for Fine-Grained Clastic Sediment
		5.5.3 Provenance Studies
	5.6 Tectonic Controls on Magmatic and Sedimentary Geochemistry
6 Using Radiogenic Isotope Data
	6.1 Introduction
	6.2 Radiogenic Isotopes in Geochronology
		6.2.1 Isochron Calculations
			6.2.1.1 Pb Isotope Isochrons
			6.2.1.2 Fitting an Isochron
			6.2.1.3 Errorchrons
			6.2.1.4 The Geochron
		6.2.2 Model Ages
			6.2.2.1 CHUR Model Ages
			6.2.2.2 Depleted Mantle Model Ages (TDM)
			6.2.2.3 Hf Depleted Mantle Model Ages Calculated for Zircon
			6.2.2.4 Assumptions in the Calculation of Model Ages
		6.2.3 Important Concepts in Geochronology
			6.2.3.1 Closure Temperature (Tc)
			6.2.3.2 What Is an ‘Age’?
		6.2.4 Whole-Rock versus Mineral Age?
		6.2.5 Isotopic Systems Used in Geochronology
			6.2.5.1 The K–Ar and Ar–Ar Systems
			6.2.5.2 The Rb–Sr System
			6.2.5.3 The U–Th–Pb/He System
			6.2.5.4 The Sm–Nd System
			6.2.5.5 The Lu–Hf System
			6.2.5.6 The Re–Os System
			6.2.5.7 Data Reduction Software Used in Geochronology
		6.2.6 The Interpretation of Model Ages
	6.3 Using Radiogenic Isotopes in Petrogenesis
		6.3.1 The Role of the Different Isotope Systems in Identifying Reservoirs and Processes
			6.3.1.1 Sm–Nd Isotopes
			6.3.1.2 Lu–Hf Isotopes
			6.3.1.3 U–Th–Pb Isotopes
			6.3.1.4 Rb–Sr Isotopes
			6.3.1.5 Re–Os Isotopes
		6.3.2 Recognising Isotopic Reservoirs
			6.3.2.1 Oceanic Mantle Sources
			6.3.2.2 Continental Crustal Sources
			6.3.2.3 Seawater
		6.3.3 Mantle Evolution Diagrams and the Isotopic Evolution of the Mantle with Time
			6.3.3.1 The Evolution of Nd Isotopes with Time
			6.3.3.2 The Evolution of Hf Isotopes
			6.3.3.3 The Evolution of Os Isotopes
			6.3.3.4 The Evolution of Pb Isotopes
		6.3.4 Epsilon, Gamma and Mu Notations
			6.3.4.1 Calculating Epsilon Values
			6.3.4.2 Epsilon Values for Sr Isotopes
			6.3.4.3 Calculating Gamma Values for Os Isotopes
			6.3.4.4 Reducing Epsilon Uncertainties on Isochron Diagrams
			6.3.4.5 The Significance of Epsilon Values
			6.3.4.6 The Fractionation Factor fSm/Nd
			6.3.4.7 Epsilon Nd Time Plots
			6.3.4.8 Short-Lived Isotopes and the μ Notation
		6.3.5 Isotope Correlation Diagrams
			6.3.5.1 Using Isotope Correlation Diagrams and Epsilon Plots to Recognise Processes
			6.3.5.2 Crustal Contamination
			6.3.5.3 Isotope versus Element Plots
			6.3.5.4 Coupled versus Decoupled Isotope Behaviour
		6.3.6 Crust–Mantle Geodynamics
			6.3.6.1 The Secular Variation of the Mantle
			6.3.6.2 The Genesis of the Continental Crust
			6.3.6.3 Crust and Mantle Mass-Balance Models
7 Using Stable Isotope Data
	7.1 Introduction
	7.2 Principles of Stable Isotope Geochemistry
		7.2.1 Notation
			7.2.1.1 Isotope Ratios: The δ Value
			7.2.1.2 The Fractionation Factor α
		7.2.2 Equilibrium Stable Isotope Fractionation
		7.2.3 Kinetic Controls on Stable Isotope Fractionation
		7.2.4 Mass-Independent Stable Isotope Fractionations
		7.2.5 Clumped Isotopes
	7.3 Traditional Stable Isotopes
		7.3.1 Oxygen
			7.3.1.1 Variations of δ18O in Nature
			7.3.1.2 Oxygen Isotope Thermometry.
			7.3.1.3 Oxygen Isotope–Radiogenic Isotope Correlation Diagrams
		7.3.2 Hydrogen Isotopes and the Stable Isotope Geochemistry of Water and Hydrothermal Fluids
			7.3.2.1 Hydrogen Isotopes
			7.3.2.2 The Distribution of Hydrogen Isotopes in the Solar System
			7.3.2.3 The Distribution of Hydrogen Isotopes in Natural Waters
			7.3.2.4 The Distribution of Hydrogen Isotopes in Terrestrial Reservoirs
			7.3.2.5 Calculating the Isotopic Composition of Hydrothermal Fluids from Mineral Compositions
			7.3.2.6 Quantifying Water–Rock Ratios
			7.3.2.7 Examples of Water–Rock Interaction
		7.3.3 Carbon Isotopes
			7.3.3.1 Controls on the Fractionation of Carbon Isotopes
			7.3.3.2 Carbon Isotopes in Meteorites
			7.3.3.3 Carbon Isotopes in the Mantle
			7.3.3.4 Carbon Isotopes in Igneous Rocks
			7.3.3.5 Carbon Isotopes in Carbon-Bearing Sediments
			7.3.3.6 Biologically Derived (Organic) Carbon
			7.3.3.7 Carbon Isotopes and the Search for Early Life on Earth.
			7.3.3.8 Carbon Isotopes in Crustal Fluids
			7.3.3.9 Combined Oxygen and Carbon Isotope Studies of Carbonates: δ18O–δ13C Plots
			7.3.3.10 Carbon Isotope Thermometry
		7.3.4 Sulphur Isotopes
			7.3.4.1 The Distribution of Sulphur Isotopes in Nature
			7.3.4.2 Controls on the Fractionation of Sulphur Isotopes
			7.3.4.3 Using Sulphur Isotopes to Identify Multiple Sources in Igneous Rocks and Hydrothermal Mineral Deposits
			7.3.4.4 Using Sulphur Isotopes to Understand the Evolution of the Earth’s Atmosphere
			7.3.4.5 Using Sulphur Isotopes to Understand the Development of Early Life on Earth
		7.3.5 Nitrogen Isotopes
			7.3.5.1 The Distribution of Nitrogen Isotopes in Nature
			7.3.5.2 Controls on the Fractionation of Nitrogen Isotopes
			7.3.5.3 Using Nitrogen Isotopes as a Tracer in Geological and Biological Processes
			7.3.5.4 Using Nitrogen Isotopes to Understand Processes in the Early Earth
	7.4 Non-traditional Stable Isotopes
		7.4.1 Lithium Isotopes
			7.4.1.1 The Distribution of Lithium Isotopes in Nature
			7.4.1.2 Controls on the Fractionation of Lithium Isotopes
			7.4.1.3 Using Lithium Isotopes as a Tracer in Geological Processes
		7.4.2 Magnesium Isotopes
			7.4.2.1 The Distribution of Magnesium Isotopes in Nature
			7.4.2.2 Controls on the Fractionation of Magnesium Isotopes
			7.4.2.3 Using Magnesium Isotopes as a Tracer in Geological and Biological Processes
		7.4.3 Silicon Isotopes
			7.4.3.1 The Distribution of Silicon Isotopes in Nature
			7.4.3.2 Controls on the Fractionation of Silicon Isotopes
			7.4.3.3 Using Silicon Isotopes as a Tracer in Geological and Biological Processes
		7.4.4 Chromium Isotopes
			7.4.4.1 The Distribution of Chromium Isotopes in Nature
			7.4.4.2 Controls on the Fractionation of Chromium Isotopes
			7.4.4.3 Using Chromium Isotopes as a Tracer in Cosmological and Geological Processes
		7.4.5 Iron Isotopes
			7.4.5.1 The Distribution of Iron Isotopes in Nature
			7.4.5.2 Controls on the Fractionation of Iron Isotopes
			7.4.5.3 Using Iron Isotopes as a Tracer in Geological and Biological Processes
Appendices
	Appendix 3.1 The CIPW Norm Calculation (after Kelsey, 1965, and Cox et al., 1979)
	Appendix 5.1 Discriminant Function Equations for Tectonic Discrimination Diagrams
		Axes for Figure 5.5, Oceanic Basalts (Vermeesch, 2006a)
		Axes for Figure 5.6, Ultramafic and Mafic Rocks (Verma and Agrawal, 2011)
		Axes for Figure 5.7, Intermediate Rocks (Verma and Verma, 2013)
		Axes for Figure 5.9, Acid Rocks (Verma et al., 2012)
		Axes for Figure 5.10, Sedimentary Rocks (Verma and Armstrong-Altrin, 2013)
References
Index