Earth's Oldest Rocks

Cover
Earth's Oldest Rocks
Section I: Getting Started
1 -
Early Solar System Materials, Processes, and Chronology
1. Introduction
2. Probes for the Early Solar System: Meteorites Versus Sample Return Space Missions
3. Meteorite Diversity and Classification
3.1 Definitions: What Are Meteorites?
3.2 The Principles of Meteorite Classification
3.3 Meteorite Statistics
3.4 Identification of the Meteorite Parent Bodies
4. Reservoirs and Processes Recorded in Meteorites
4.1 Origins of Solar System Matter: Evidence From Presolar Grains
4.2 Isotopic Variations at Larger Scales
4.3 Melting, Thermal Metamorphism, Aqueous Alteration, and Shock Metamorphism
4.4 Meteorites as an Imperfect Proxy to the Composition of the Solar System and the Earth
4.5 Organic Matter and Possible Traces of Extraterrestrial Life in Meteorites
5. Meteorite Chronology
5.1 Methods of Modern Meteorite Chronology
5.2 CAIs, Chondrules, and Achondrites: Three Cornerstones of Research in the Early Solar System Chronology
6. Future of Meteorite Research
References
Further Reading
2 -
Origin of the Earth and the Late Heavy Bombardment
1. The Solar Nebula
2. Giant Impacts and Formation of the Moon
3. The Composition of the Earth
4. Core Formation and the Late Veneer
5. The Late Heavy Bombardment
5.1 Constraints From Lunar Geology
5.2 Age Constraints From Lunar Samples
5.3 Lunar Basins: Provenance and Age Assignments
5.4 Constraints From Lunar Mass
5.5 Siderophile Elements in Lunar Highlands
5.6 Dynamical Implications
6. Implications for Early Earth
7. Conclusions
Acknowledgments
References
Further Reading
3 -
Early Earth Atmosphere and Oceans
1. Introduction
2. The Hadean Atmosphere and Ocean
2.1 Historical Perspective
2.2 Formation of the Ocean
2.3 The Late Heavy Bombardment (or Absence Thereof?)
2.4 Was the Hadean Climate Hot or Cold?
3. Archean Climate
3.1 Constraints, or Lack Thereof, From Oxygen Isotopes
3.2 Glacial Constraints on Surface Temperature
3.3 Constraints on Archean CO2 Concentrations
4. Atmospheric Redox Balance: Implications for Abiotic O2 Concentrations and the Origin of Life
4.1 Atmospheric Photochemistry and Redox Balance
4.2 Prebiotic CO Concentrations and Their Possible Implications for the Origin of Life
5. Summary
References
Section II: Overviews of Early Earth Processes
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Modeling Early Earth Tectonics: The Case for Stagnant Lid Behavior
1. Introduction
1.1 Hadean Observational Constraints
1.1.1 Utility of Geodynamic Simulations
1.1.2 Previous Geodynamic Models
2. Methodology
3. Results
3.1 Baseline Model
3.2 Initial Conditions
3.3 Giant Impacts
3.4 Heat-Pipe Volcanism
4. Discussion
5. Conclusions
References
5 -
The Earliest Subcontinental Lithospheric Mantle
1. Introduction
2. Subcontinental Lithospheric Mantle Composition
3. Archean Subcontinental Lithospheric Mantle
3.1 Archean Subcontinental Lithospheric Mantle Is Unique
3.2 What Is Its Bulk Composition?
3.2.1 Methods of Estimating Composition
3.2.2 What Do These Estimates Represent?
3.2.3 How Old Is It?
3.2.4 How Did It Form?
4. Is There More Archean Subcontinental Lithospheric Mantle Than We Think?
5. Implications for Crustal Evolution
Acknowledgments
References
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Distribution and Geochemistry of Komatiites and Basalts Through the Archean
1. Introduction
2. Geochemical Variations and Abundance of Different Komatiite and Basalt Types Through Time
2.1 Data Set
2.2 Classification of Komatiites and Komatiitic Basalts
2.3 Geochemical Characteristics of the Different Types of Komatiite
2.4 Classification of Basalts
2.5 Distribution of All Komatiite and Basalt Types Through Time
2.5.1 Komatiites
2.5.2 Basalts
3. Archean Basalt Chemistry in Comparison With Modern Settings
4. Discussion
4.1 The Tectonic Setting of Archean Basalts
4.2 MgO Contents and Eruption Temperatures of Komatiites Through Time
4.3 Evolution of Komatiite Compositions
5. Conclusions
Appendix
References
Further Reading
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The Formation of Tonalites-Trondjhemite-Granodiorites in Early Continental Crust
1. Introduction
2. Constraints on the Formation History of Early Archean Gray Gneiss Protoliths
2.1 Tonalites-Trondhjemites-Granodiorites
2.2 Non-Tonalite-Trondhjemite-Granodiorite Components of Gray Gneiss Complexes
3. Geochemical Constraints on the Origin of Tonalite-Trondhjemite-Granodiorite Melts: Source Rocks and Melting Sites
3.1 The Sources of Tonalite-Trondhjemite-Granodiorite
3.2 The Conditions of Melting/Fractionation
3.3 Petrogenetic Models for Tonalite-Trondhjemite-Granodiorite Formation
3.4 Further Complications
4. Experimental Constraints on Tonalite-Trondhjemite-Granodiorite Formation
4.1 Starting Material of Partial Melting Experiments
4.2 Melting Behavior in Nature in Comparison to Experiments
5. Petrological Phase Equilibrium Modeling
6. Geodynamic Models
6.1 Proposed Geodynamic Sites for the Origin of Tonalite-Trondhjemite-Granodiorite-a View From Modern Earth
6.2 Generation of Archean Tonalite-Trondhjemite-Granodiorite Melts
6.3 The Fate of Tonalite-Trondhjemite-Granodiorite Restites
6.4 Examples for Eo- and Paleoarchean Continental Crust Formation
7. Summary
Acknowledgments
References
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Archean Asteroid Impacts on Earth: Stratigraphic and Isotopic Age Correlations and Environmental Consequences
1. Introduction
2. Overview of Archean Impacts
3. Correlation of Impact Layers
3.1 Stratigraphic Correlations
3.2 Zircon Geochronology
3.3 Primary and Shocked Minerals
3.4 Platinum-Group Element and Other Geochemical Correlations
4. Environmental Effects of Impacts
4.1 Tsunami
4.2 Evaporation
4.3 Atmospheric Change
5. Tectonic Implications
6. Summary and Future Directions
References
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Paleoarchean (3.6-3.2Ga) Mineral Systems in the Context of Continental Crust Building and the Role of Mantle Plumes
1. Introduction
2. Early Earth Geodynamics
3. The Growth of the Paleoarchean Continental Crust and the Role of Mantle Plumes
3.1 Mantle Plumes
3.1.1 Paleoarchean Mantle Plumes
4. The Hadean to Paleoarchean
4.1 Pilbara Craton, Western Australia
4.1.1 East Pilbara Terrane
4.2 The Barberton Greenstone Belt (South Africa)
4.2.1 Paleoarchean Mineral Systems in the Barberton Greenstone Belt
5. Discussion and Conclusions
Acknowledgments
References
Further Reading
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Origin of Paleoarchean Sulfate Deposits
1. Introduction
2. Geological Context of Archean Barite Deposits
2.1 Kaapvaal Craton, Barberton Greenstone Belt
2.1.1 Londozi Barite Deposit
2.1.2 Vergelegen Barite Deposit
2.1.3 Stentor Barite Deposit
2.1.4 Mapepe Formation, Baryte Valley Syncline
2.2 Pilbara Craton
2.2.1 Dresser Formation of the North Pole Dome, Warrawoona Group
2.2.2 Strelley Pool Formation
2.2.3 Kangaroo Caves Formation
2.3 Dharwar Craton
2.3.1 Ghattihosahalli Belt
3. Nomenclature and Isotopic Notations
4. Multiple Sulfur Isotope Systematics of Early Archean Sulfates and Sulfides
4.1 Origin of Barite
4.2 Origin of Pyrite
4.3 Primary Photolytic Signal Versus Mass-Dependent Overprint
5. Discussion and Perspectives
Acknowledgments
References
Section III: The Most Ancient Remnants
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Earth's Oldest Rocks and Minerals
1. Introduction
2. Occurrences of Earth's Oldest Rocks
3. The Hadean Detrital Zircon Record
4. Zircon Age Spectra before 2.8 Ga
References
Further Reading
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The Oldest Terrestrial Mineral Record: Thirty Years of Research on Hadean Zircon From Jack Hills, Western Australia
1. Introduction
2. Jack Hills Metasedimentary Rocks
2.1 Age of Deposition
2.2 Metamorphism
2.3 Geology of Adjacent Rocks
3. Studies of Jack Hills Zircon
3.1 Images of Jack Hills Zircon
3.2 Age of the Hadean Zircon Population
3.2.1 The U-Pb Story
3.2.2 U Abundance, Radiation Damage, and Pb Loss
3.2.3 The Oldest Grains in the Jack Hills
3.2.4 Distribution of Hadean Grains
3.3 Oxygen Isotopes
3.4 Trace Elements
3.4.1 Lithium
3.4.2 Ti Thermometry
3.4.3 Rare Earth Elements, Yttrium and Phosphorous
3.4.4 Other Trace Elements (Al, Sc, Sm/Nd, Xe)
3.5 Hafnium Isotopic Compositions
3.6 Mineral Inclusion Studies
4. Early Earth Processes Recorded by Jack Hills Zircon
4.1 Derivation of Jack Hills Zircon From Early Mafic Crust (εHf)
4.2 Existence of ﹥4300 Ma Granitoid
4.3 Significance of Surface Alteration on the Early Earth
4.4 Impact Events Recorded in Jack Hills Zircon?
Acknowledgments
References
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Evidence of Hadean to Paleoarchean Crust in the Youanmi and South West Terranes, and Eastern Goldfields Superterrane of the ...
1. Introduction
2. Evidence of Hadean to Paleoarchean Yilgarn Crust Outside the Narryer Terrane
2.1 Detrital and Xenocrystic Zircon Ages
2.1.1 Youanmi Terrane
2.1.2 South West Terrane
2.1.3 Eastern Goldfields Superterrane
2.2 Isotope Studies
2.2.1 Whole-Rock Sm-Nd Isotopes
2.2.2 Zircon Lu-Hf Isotopes
2.2.2.1 Magmatic and Xenocrystic Zircons
2.2.2.2 Detrital Zircons
3. Discussion
4. Conclusions
Acknowledgments
References
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Hadean to Paleoarchean Rocks and Zircons in China
1. Introduction
2. General Geology
3. North China Craton
3.1 Anshan
3.2 Eastern Hebei Province
3.3 Xinyang Area
3.4 Other Areas of the North China Craton
4. South China Craton
4.1 Yangtze Block
4.2 Cathaysia Block
5. Tarim Craton
6. Younger Orogenic Belts
7. Discussion
8. Conclusions
Acknowledgments
References
Further Reading
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The Acasta Gneiss Complex
1. Introduction
2. Acasta Gneiss Complex Geology
3. Geochronology
3.1 Zircon U-Pb
3.2 Whole-Rock Dating Techniques
3.3 Thermochronology
4. Geochemistry
4.1 Whole-Rock Elemental Compositions
4.2 Isotope Geochemistry and Source Compositions
4.2.1 Pb Isotopes
4.2.2 147Sm-143Nd
4.2.3 146Sm-142Nd
4.2.4 182Hf-182W
4.2.5 176Lu-176Hf
4.3 Oxygen Isotopes
5. Tectonic Setting for the Acasta Gneiss Complex
6. Comparison to Other Eoarchean Gneiss Terranes
7. Conclusions
Acknowledgments
References
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The Nuvvuagittuq Greenstone Belt: A Glimpse of Earth's Earliest Crust
1. Introduction
2. The Nuvvuagittuq Greenstone Belt: A Review
2.1 Geology
2.1.1 Nuvvuagittuq Greenstone Belt Supracrustal Assemblages
2.1.1.1 Mafic Metavolcanic Rocks
2.1.1.2 Metasedimentary Rocks
2.1.2 Felsic Plutonic Rocks Surrounding the Nuvvuagittuq Greenstone Belt
2.2 Age of the Nuvvuagittuq Greenstone Belt
2.2.1 An Eoarchean Age for the Nuvvuagittuq Greenstone Belt
2.2.2 Hadean Age for the Nuvvuagittuq Greenstone Belt
3. Discussion
3.1 How Old is the Nuvvuagittuq Greenstone Belt?
3.2 Nature of the Earliest Crust, Early Geological Settings, and Environments
4. Concluding Remarks
References
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The 3.9-3.6Ga Itsaq Gneiss Complex of Greenland
1. Introduction
2. The Itsaq Gneiss Complex
2.1 Discovery
2.2 Diversity Within the Itsaq Gneiss Complex
2.3 The Isua Supracrustal Belt and Surrounding Granitoids
3. Itsaq Gneiss Complex Protoliths
3.1 Discriminating Protolith Features
3.2 Banded Gray Gneisses: Multigenerational Plutonic Complexes
3.3 Amphibolites: Pillow Lavas and Gabbros
3.4 Ultramafic Rocks: Layered Peridotites and Massive Dunites and Harzburgites
3.5 Felsic Schists: Andesitic-Dacitic Volcanic and Volcanoclastic Rocks
3.6 Carbonates: Discrimination of Sedimentary and Metasomatic Rocks
4. Geochemistry
4.1 Mafic and Intermediate Rocks
4.2 Tonalites and Dacites
4.3 Granites and Coeval Gabbros
4.4 Long Half-Life Radiogenic Isotope Signatures
4.5 Short Half-Life Radiogenic Isotope Signatures
5. Relict Eoarchean Tectonic Structures and Metamorphic Assemblages in the Itsaq Gneiss Complex
5.1 Pre-3700 Ma Tectonic Intercalation of Crust and Mantle
5.2 Pre-3660 Ma Metamorphic History
5.3 Isukasian Orogeny: <3670 Ma Crustal Thickening Followed by High-Temperature Extension
6. Discussion
6.1 The Evidence for Terranes in the Eoarchean
6.2 Eoarchean Suprasubduction Zone Ophiolite
6.3 Death of Eoarchean Suprasubduction Zone Ophiolites by Collisional Orogeny
6.4 Quasiuniformitarian Eoarchean Geodynamics
7. Conclusion
Acknowledgments
References
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The Narryer Terrane, Yilgarn Craton, Western Australia: Review and Recent Developments
1. Introduction
2. Historical
3. Characteristics of the Narryer Terrane
3.1 Overview
3.2 Quartzofeldspathic Gneisses
3.2.1 Meeberrie Gneiss
3.2.2 Dugel Gneiss
3.2.3 Manfred Complex
3.2.4 Eurada Gneiss
3.2.5 Porphyritic Meta-granites
3.2.6 Other Gneissic Rocks
3.3 Supracrustal Belts
3.3.1 Mount Narryer Supracrustal Belt
3.3.2 Jack Hills Belt and Environs
3.3.3 Other Metasedimentary Occurrences
3.4 Late Archean Intrusives
3.4.1 Neoarchean Gneisses
3.5 Timing of Deformation and Metamorphism
3.5.1 Mount Narryer Region
3.5.2 Jack Hills Belt
4. Isotopic Studies
4.1 Gneissic and Granitic Rocks
4.2 Detrital Minerals From Jack Hills
4.3 Detrital Minerals From Mount Narryer
5. Some Outstanding Issues
5.1 Regional Correlations
5.2 Sedimentary Environment
5.3 The Source of the Detrital Zircons, Including Those ﹥4000 Ma
Acknowledgments
References
Section IV: Well-Preserved Granitoid- Greenstone Terrains
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Paleoarchean Development of a Continental Nucleus: The East Pilbara Terrane of the Pilbara Craton, Western Australia
1. Introduction
2. Geology of the Pilbara Craton
3. Geology of the East Pilbara Terrane
3.1 Lithostratigraphy in Greenstone Belts
3.1.1 Warrawoona Group
3.1.2 Kelly Group
3.1.3 Sulphur Springs Group
3.1.4 Soanesville Group
3.2 Granitic Rocks
3.3 Evidence for Sialic Basement to the Greenstones
3.4 Geochemistry
3.4.1 Ultramafic Rocks
3.4.2 Mafic Rocks
3.4.3 Felsic Volcanic Rocks
3.4.4 Granitic Rocks
3.5 Deformation and Metamorphism
3.6 Later Events
4. Tectonic Models, Old and New
4.1 Tectonic Setting of Greenstone Belt Development
4.2 Tectonic Models of Deformation
4.3 Current Model of Crust Formation
Acknowledgments
References
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The Oldest Well-Preserved Felsic Volcanic Rocks on Earth: Geochemical Clues to the Early Evolution of the Pilbara Supergrou ...
1. Introduction
2. Regional Geological Summary
3. Analytical Methods
4. Coonterunah Subgroup
4.1 Geochemistry of the Coonterunah Subgroup
4.1.1 Table Top Formation-Basalts and Komatiites
4.1.2 Coucal Formation-Basalts to Rhyolites
5. Duffer Formation
5.1 Geochemistry of the Duffer Formation
6. Felsic Volcanic Units at Higher Stratigraphic Levels
7. Petrogenesis of Mafic Volcanic Rocks
8. Petrogenesis of Felsic Volcanic Rocks
9. Implications for Early Pilbara Crustal Evolution
9.1 Early Felsic Crust-TTG or Tholeiitic Andesite?
9.2 Early Crust Formation Through Internal Differentiation
9.3 Continued Crustal Cycling
10. Conclusions
Acknowledgments
References
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Geochemistry of Paleoarchean Granites of the East Pilbara Terrane, Pilbara Craton, Western Australia: Implications for Earl ...
1. Introduction
2. Regional Geological Summary
3. Granite Geochemistry and Petrology
3.1 Introduction
3.2 c.3.5-3.42Ga Granites
3.3 c.3.32-3.24Ga granites
4. Geochemistry
4.1 Analytical Methods
4.2 c.3.5-3.42Ga Granites
4.3 c.3.32-3.24Ga Granites
5. Granite Petrogenesis
5.1 Introduction
5.2 Partial Melting Versus Fractional Crystallization
5.3 Partial Melting
5.4 LILE, Th, and εNd Variability
5.5 Toward a Petrogenetic Model
6. Discussion
6.1 Transitional TTGs
6.2 Conclusions
Acknowledgments
References
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Paleoarchean Mineral Deposits of the Pilbara Craton: Genesis, Tectonic Environment, and Comparisons With Younger Deposits
1. INTRODUCTION
2. PALEOARCHEAN GEOLOGICAL EVOLUTION OF THE PILBARA CRATON
3. PALEOARCHEAN MINERAL DEPOSITS OF THE PILBARA CRATON
3.1 Volcanic-Hosted Massive Sulfide Deposits and Stratiform Barite Deposits
3.1.1 The North Pole Barite Deposits
3.1.2 The Big Stubby Deposit
3.1.3 The Lennon's Find Deposits
3.1.4 Deposits Hosted by the Sulphur Springs Group
3.1.5 Other Possible Volcanic-Hosted Massive Sulfide Prospects
3.2 Lode-Gold Deposits
3.2.1 The Marble Bar, Comet, and Warrawoona Districts
3.2.2 Bamboo Creek District
3.2.3 North Pole District
3.2.4 Minor Lode-Gold Districts
3.2.5 The Age of Mineralization
3.3 Deposits of the Porphyry-Epithermal Environment
3.3.1 The Spinifex Ridge Mo-Cu Porphyry Deposit
3.3.2 Cu-Mo Deposits in the McPhee Dome
3.3.3 Other Possible Porphyry-Related Systems
3.3.4 Cu-Au and Zn-Pb-Ag-Au Deposits in the McPhee Dome
3.3.5 Miralga Creek Epithermal Gold Deposit
3.3.6 Other Possible Porphyry-Epithermal Mineral Deposits and Alteration Assemblages
3.4 Banded Iron Formations
4. METALLOGENESIS IN OTHER PALEOARCHEAN TERRAINS
5. A COMPARISON OF PALEOARCHEAN, NEOARCHEAN, AND PHANEROZOIC METALLOGENY
5.1 Volcanic-Hosted Massive Sulfide Deposits and Stratiform Barite Deposits
5.2 Lode-Gold Deposits
5.3 Porphyry Mo-Cu and Epithermal Au Deposits
5.4 Banded Iron Formations
6. IMPLICATIONS FOR TECTONIC PROCESSES DURING THE PALEOARCHEAN
7. CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
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Early Archean Crustal Evolution in Southern Africa-An Updated Record of the Ancient Gneiss Complex of Swaziland
1. Introduction
2. Geological Setting
3. Field Relationships, Geochemsitry, and Origin of Components of the Ancient Gneiss Complex
4. Geochronology and Implications for Gneiss-Greenstone Relationships
4.1 Ngwane Gneiss
4.2 Dwalile Supracrustal Suite
4.3 Tsawela Gneiss
4.4 Mhlatuzane Gneiss
5. Discussion and Conclusions
Acknowledgments
References
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Geologic Evolution of the Barberton Greenstone Belt-A Unique Record of Crustal Development, Surface Processes, and Early Li ...
1. Introduction
2. General Geology of the Barberton Greenstone Belt
2.1 Stratigraphy
2.1.1 Structure
2.1.2 Alteration
3. Tectonostratigraphic Blocks
3.1 Songimvelo Block-South of the Komati Fault
3.2 Songimvelo Block-North of the Komati Fault
3.2.1 Komati Formation
3.2.2 Hooggenoeg Formation
3.2.2.1 H1: Chert
3.2.2.2 H2: Tholeiitic Basalt
3.2.2.3 H3: Komatiitic and Tholeiitic Basalt and Komatiite
3.2.2.4 H4: Komatiitic Basalt, Basalt, and Komatiite
3.2.2.5 H5: Tholeiitic Basalt
3.2.2.6 H6: Felsic Igneous and Volcaniclastic Rocks
3.2.3 Kromberg Formation
3.2.3.1 K1: The Buck Reef Chert
3.2.3.2 K2: Mafic Lapilli Tuff and Lapillistone
3.2.3.3 K3: Basalt
3.2.4 Mendon Formation
3.2.5 Fig Tree and Moodies Strata
3.2.6 Songimvelo Intrusives and Related Rocks
3.3 Umuduha Block
3.3.1 Mendon Formation
3.3.2 Lower Fig Tree Group
3.3.3 Moodies Group
3.3.4 Intrusive Rocks
3.4 Kaap Valley Block
3.4.1 Onverwacht Group
3.4.2 Fig Tree Group
3.4.3 Moodies Group
3.4.4 Intrusives and Related Rocks
4. Structural Development of the Barberton Granite-Greenstone Terrain
4.1 Pre-D1 Deformation
4.2 D1: Extension
4.3 ∼3330 Ma Rifting
4.4 D2
4.5 D3
4.6 D4
4.7 D5
5. Evolution of the Barberton Granite-Greenstone Terrain
6. Conclusions
Acknowledgments
References
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TTG Plutons of the Barberton Granitoid-Greenstone Terrain, South Africa
1. Introduction
1.1 Archean Tonalite-Trondhjemite-Granodiorite
1.2 Regional Geology of the Barberton Granitoid-Greenstone Terrain
2. Data Source and Interpretation
2.1 Field Data
2.2 Geochronology
2.3 Geochemistry
2.3.1 Major Elements Geochemistry
2.3.2 Trace Elements Geochemistry
3. Geology and Geochemistry of BGGT TTGs
3.1 The Kaap Valley and Nelshoogte Plutons (TTG3b)
3.1.1 Kaap Valley Pluton
3.1.2 Nelshoogte Pluton
3.1.3 Regional Context and Comparisons
3.2 Badplaas-Inyoni (TTG3a and 3b)
3.2.1 Badplaas Complex
3.2.2 Inyoni Shear Zone
3.2.3 Regional Context
3.3 The Stolzburg Block (TTG2)
3.3.1 Central Plutonic Domains
3.3.2 Contact Zones Around the Plutons
3.3.3 Regional Context and Comparisons
3.4 Steynsdorp Gneisses (TTG1)
4. Isotope Geochemistry
5. Discussion
5.1 Controls of the Geochemistry of TTG Suites
5.1.1 Fractionation and Intrasuite Differentiation
5.1.2 Sources and Depth of Melting
5.1.2.1 The Lack of Evidence for Any Old Crustal Input
5.1.2.2 A Slightly ``Enriched'' Mafic Source
5.1.2.3 Slightly Variable Sources
5.1.2.4 Variable Depths of Melting
5.1.3 The Magmatic History of Barberton TTGs
5.2 Tectonic Models
5.2.1 3.51-3.45 Ga: Formation of TTGs in a Mafic Plateau
5.2.2 3.2 Ga Evolution
5.2.2.1 Partial Convective Overturn in Barberton?
5.2.2.2 Subduction-Accretion Models
5.2.2.3 A ``Deformable Lid'' Model for the Barberton Granitoid-Greenstone Terrain
6. Conclusion
Acknowledgments
Appendix
Methods
Analytical Conditions
Results
References
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Tectonometamorphic Controls on Archaean Gold Mineralization in the Barberton Greenstone Belt, South Africa
1. Introduction
2. Geological Setting
3. Tectonic Evolution and Timing of Gold Mineralization
4. Characteristics of Greenschist Facies Gold Deposits
4.1 Sheba and Fairview Gold Mines
5. The New Consort Gold Mine
5.1 Structural Evolution
5.2 Structural Control on Mineralization in Underground Workings
5.3 Metamorphism
5.4 Gold Mineralization
6. Discussion
6.1 Tectonometamorphic Controls on Gold Mineralization
7. Implications
Acknowledgments
References
Section V: Filling the Gaps
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Paleoarchean Gneisses in the Minnesota River Valley and Northern Michigan, USA
1. INTRODUCTION
2. REGIONAL SETTING
3. GEOLOGIC SETTING
3.1 Minnesota River Valley
3.2 Northern Michigan
4. GEOCHRONOLOGY
4.1 Minnesota River Valley
4.1.1 Montevideo Block
4.1.2 Morton Block
4.1.3 Benson Block
4.2 Northern Michigan
5. GEOCHEMICAL AND ISOTOPIC STUDIES
5.1 Geochemical Data
5.2 Isotopic Data
5.2.1 Lu-Hf Data
5.2.2 Sm-Nd Data
6. DISCUSSION
6.1 What Was the Origin of the MRV Rocks?
6.2 Ages of Migmatitic Gneiss Components in the MRV
6.3 Thermotectonic History of the Benson, Montevideo, and Morton Blocks in the MRV
6.4 When Were the Benson, Montevideo, and Morton Blocks Assembled?
6.5 How Are the MRV and Northern Michigan Terranes Related to the Superior Craton?
6.5.1 Tectonic History of the Superior Province
6.5.2 Accretion of the Minnesota River Valley Terrane to the Superior Craton
ACKNOWLEDGMENTS
REFERENCES
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The Assean Lake Complex: Ancient Crust at the Northwestern Margin of the Superior Craton, Manitoba, Canada
1. Introduction
2. Principal Geological Elements of the Northwestern Superior Craton Margin
2.1 Pikwitonei Granulite Domain
2.2 Split Lake Block
2.3 Thompson Nickel Belt
2.4 Trans-Hudson Orogen
3. Geology of the Assean Lake Complex
3.1 Structural Domains of the Assean Lake Area
3.2 Lithotectonic Assemblages of the Assean Lake Complex
3.2.1 Clay River Assemblage
3.2.2 Central Felsic Intrusive Rocks (Orthogneiss Domain)
3.2.3 Lindal Bay Assemblage
3.3 Tracer Isotopic Constraints on the Antiquity of the Assean Lake Complex
3.3.1 Whole-Rock Sm-Nd Isotopic Results
3.3.2 Combined Whole-Rock Sm-Nd and Lu-Hf Isotopic Results
3.3.3 Zircon Lu-Hf Isotopic Results
3.4 U-Pb Age Constraints of the Assean Lake Complex
4. Extent of the Mesoarchean Assean Lake Complex
4.1 Eastern Extent of the Assean Lake Complex
4.2 Northern and Western Extent of the Assean Lake Complex
4.3 The Assean Lake Complex-Split Lake Block Connection
4.3.1 Supracrustal Rocks
4.3.2 Felsic Plutonism
5. Potential Source Material for the Assean Lake Complex
6. Concluding Remarks
Acknowledgments
References
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Oldest Rocks of the Wyoming Craton
1. Introduction
2. Known Occurrences of Eo- and Paleoarchaean Rocks and Minerals
2.1 Eoarchaean Detrital Zircons and Cores
2.2 Paleoarchaean Rocks of Southwestern Montana-The Montana Metasedimentary Province (MMP)
2.3 Paleoarchaean Rocks of the Beartooth Mountains
2.4 Paleoarchaean Rocks of the Granite Mountains, the Sacawee Block
3. Isotopic Evidence of Ancient Crust in Meso- to Neoarchaean Plutons and Sedimentary Rocks
4. Discussion
5. Conclusions
References
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Early Crustal Evolution as Recorded in the Granitoids of the Singhbhum and Western Dharwar Cratons
1. Introduction
2. Singhbhum Craton
2.1 Regional Geology
2.2 Champua Suite (Older Metamorphic Tonalite Gneiss in Older Literature) and Equivalent Granitoids
2.2.1 Geological Setting and Age
2.2.2 Geochemistry
2.2.3 Petrogenesis
2.3 Singhbhum Suite
2.3.1 Geological Setting
2.3.2 Geochemistry and Age
2.3.3 Petrogenesis
2.4 Bonai Suite
2.4.1 Geological Setting
2.4.2 Geochemistry and Age
2.4.3 Petrogenesis
2.5 Paleoarchean Crustal Evolution in the Singhbhum Craton
3. Dharwar Craton
3.1 Regional Geology
3.2 Granitoids
3.2.1 Anmodghat (Goa) Region
3.2.2 Chikmagalur Region
3.2.3 Holenarsipur Region
3.2.4 Gundlupet Region
3.3 Paleoarchean (to Mesoarchean) Crustal Evolution in the Western Dharwar Craton
4. Discussion
Appendix 1: Analytical Techniques
Whole-Rock Element Analysis
Zircon U-Pb Dating
Zircon Hf Isotope Analysis
Acknowledgments
References
Further Reading
31 -
Paleoarchean Crustal Evolution of the Bundelkhand Craton, North Central India
1. Introduction
2. General Geology of the Bundelkhand Craton
3. Field Observations and Structural Analyses
4. U-Pb SHRIMP Zircon Geochronology
4.1 Analytical Methods
4.2 Results
5. Geochemistry
5.1 Analytical Methods
5.2 Results
6. Petrology, Mineral Chemistry, and P-T Estimates
6.1 Analytical Methods
6.2 Results
7. Tectonic Implications
Acknowledgments
References
Further Reading
32 -
Paleoarchean Rocks in the Fennoscandian Shield
1. Introduction
2. Geological Setting
3. Paleoarchean Rocks
3.1 Vodlozero
3.1.1 Sm-Nd and Lu-Hf
3.1.2 Age Determinations
3.1.2.1 Methods
3.1.2.2 Samples
3.1.2.3 Results
4. Discussion
Acknowledgments
References
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Archean Crustal Evolution in the Ukrainian Shield
1. Introduction
2. Archean Geology, Geochemistry, and Age Correlations in the Ukrainian Shield
2.1 The Podolian Domain
2.1.1 The Dniester-Bug Series
2.1.1.1 U-Pb Ages
2.1.1.2 Hf, Nd, and Sr Isotope Systematics
2.1.1.3 Geochemistry
2.1.1.4 O Isotopes in Quartzose Rock From the Odesa Stone Pit
2.1.1.5 Formation of the Oldest Dniester-Bug Series
2.2 The Azov Domain
2.3 The Middle Dnieper Domain
2.3.1 Geochronology
3. Summary of Pre-Neoarchean Crustal Evolution in the Ukrainian Shield
3.1 In Honor of Elena Bibikova
Acknowledgments
References
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The Paleoarchean Record of the Zimbabwe Craton
1. Archean Geology of the Zimbabwe Craton
2. The Pre-3.2 Ga Record of the Zimbabwe Craton
2.1 Sebakwe Proto-Craton
2.2 Mushandike and Mont d'Or Granitoids
2.3 Sebakwian Group
2.3.1 Sebakwian Group of the Tokwe Gneiss Terrain
2.3.2 Sebakwian Group of the Rhodesdale Gneiss Terrain
2.4 Detrital Zircon Record
2.5 Eoarchean Subcontinental Lithospheric Mantle
3. Discussion and Conclusions
Acknowledgments
References
35 -
Ancient Antarctica: The Archean of the East Antarctic Shield
1. Introduction
2. Overview of the Geology of the East Antarctic Shield
2.1 Late Neoproterozoic to Cambrian Tectonic Belts
2.2 Late Mesoproterozoic to Early Neoproterozoic Provinces
2.3 Archean and Archean-Paleoproterozoic Terranes With Little Pre-3000 Ma Record
2.4 Archean and Archean/Proterozoic Terranes With Pre-3000 Ma Crustal Records
2.4.1 The Grunehogna Craton, Western Dronning Maud Land
2.4.2 The Ruker Terrane, Southern Prince Charles Mountains
2.4.3 The Archean Mather Terrane, Rauer Province, Prydz Bay
2.4.4 The Kemp Land Coast Region
2.4.5 The Archean Napier Complex, Enderby Land
3. The Oldest Rocks: ﹥3400 Ma
3.1 The Manning Orthogneisses-Central Mawson Escarpment
3.2 Early Archean Orthogneisses of the Mather Terrane
3.3 Reworked Early Archean Crust in the Rayner Province of Kemp Land
3.4 The Napier Complex
3.4.1 Fyfe Hills
3.4.2 Aker Peaks
3.4.3 Mount Sones
3.4.4 Gage Ridge
3.4.5 Dallwitz Nunatak and the Further Impacts of Ancient Pb Mobility Within Zircon
4. Conclusions
Acknowledgments
References
Section VI: Life
36 -
Implications of Carbonate and Chert Isotope Records for the Early Earth
1. Introduction
2. The Sr Isotope Composition of the Early Ocean
3. The C Isotope Composition of Early Marine Carbonate Rocks
4. The O Isotope Composition of Early Marine Sedimentary Rocks
5. Summary
Acknowledgments
References
37 -
Archean Cherts: Formation Processes and Paleoenvironments
1. Introduction
2. Chert: Definition and Occurrence in the Barberton Greenstone Belt
3. Pervasive Silicification of the Archean Oceanic Crust
3.1 Metasomatic Alteration of Volcanic Units
3.2 Chemical Disturbance
3.3 Origin of Silica Alteration Zones
4. S-Chert and Early Silicification on the Seafloor
4.1 Si-Metasomatism within Bedded Chert Units
4.2 Chemical Disturbances
4.3 Oceanic Versus Hydrothermal Silicification
5. C-Chert and Chemical Precipitation at the Seafloor
5.1 Occurrence in the Barberton Greenstone Belt and Relevance for Early Life
5.2 Origin of Pure Silica Layers
5.3 Mechanism of Silica Precipitation
5.4 Origin of the Layering
5.5 Buck Reef Chert: A Habitat of Early Life
6. Silicon Isotopes, a Promising Tool to Investigate Archean Ocean Composition?
6.1 Basic Principle
6.2 Silica Sources and Paleoseawater Temperature
6.3 Microscale Analyses
6.4 Limitations of the Approach: The Fractionation Factors
7. Conclusions
References
38 -
The Significance of Carbonaceous Matter to Understanding Life Processes on Early Earth
1. Introduction
2. Alteration of Biomass to Carbonaceous Material
3. Mineral Matrices in Which Carbonaceous Material Is Preserved
4. Abiogenic Carbonaceous Material
4.1 Fischer-Tropsch-Type Synthesis in Ultramafic-Hosted Hydrothermal Processes
4.2 Thermal Decomposition of Carbonate Minerals
4.3 Fluid-Deposited Graphite
5. Controversies
5.1 Fluid-Deposited Graphite in the Akilia Association, Southern West Greenland
5.2 Graphite in the Isua Supracrustal Belt, Southern West Greenland
5.3 Hydrothermal Feeder Veins, Apex Chert, Pilbara, Western Australia
6. Discussion and Future Directions
References
39 -
Eoarchean Life From the Isua Supracrustal Belt (Greenland
1. Introduction
2. Geology of the Isua Supracrustal Belt
3. Metasedimentary Rocks-the Most Obvious Targets for Early Life Evidence
3.1 3800 Ma Rocks
3.2 ∼3750 Ma Dividing Sedimentary Unit
3.3 3710-3705 Ma Felsic Volcanosedimentary Rocks and Mafic Pelites
3.4 ∼3700 Ma Banded Iron Formations, Dolomitic, and Quartz-Rich Sedimentary Rocks of the Central Tectonic Domain
4. Less Obvious Early Life Targets in Isua
5. Isua Chemofossil Evidence for Eoarchean Life
5.1 Carbon Isotope Signatures of Carbonates
5.2 Graphite Isotopic Signature and Microstructure
5.3 Iron Isotopic Signatures of Banded Iron Formation and Carbonates
6. Eoarchean Fossils
6.1 Isuasphaera isua (Pflug) Microfossils
6.2 Stromatolites
7. Discussion
7.1 Banded Iron Formation
7.2 Low-Temperature Dolomite
8. Conclusions
Acknowledgments
References
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Depositional Setting of the Fossiliferous, c.3480Ma Dresser Formation, Pilbara Craton: A Review
1. Introduction
2. Geological Setting
3. Previous Work
3.1 Paleoenvironmental Model
3.2 Evidence for Life
4. Stratigraphy of the North Pole Chert
4.1 Middle Basalt Member
4.2 Upper Chert Member
5. Dresser Hydrothermal Veins and Footwall Alteration
5.1 Mineralized Hot Spring Pools
5.2 Vein Geometry
5.3 Hydrothermal Alteration of Footwall Basalts
6. Environmental Model
Acknowledgments
References
41 -
Early Archean (Pre-3.0Ga) Cellularly Preserved Microfossils and Microfossil-Like Structures From the Pilbara Craton, Wester ...
1. Introduction
2. Geological Setting
3. Cellularly Preserved Microfossils and Microfossil-Like Structures
3.1 Warrawoona Group
3.1.1 Dresser Formation
3.1.2 Chert of the Mount Ada Basalt
3.1.3 Chert of the Apex Basalt
3.1.4 Panorama Formation
3.2 Strelley Pool Formation
3.3 Kangaroo Caves Formation of the Sulfur Springs Group
3.4 Dixon Island Formation
3.5 Farrel Quartzite of the Gorge Creek Group
4. Discussion
4.1 Diversity of Habitats
4.2 Implications for Life Cycle, Taxonomy, and Biological Affinity of Archean Spheroid and Lenticular Microfossils
4.2.1 Small Spheroids
4.2.2 Large Spheroids
4.2.3 Lenticular Microfossils
5. Conclusions
Acknowledgments
References
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Traces of Early Life From the Barberton Greenstone Belt, South Africa
1. Geological Setting
2. Traces of the Ancient Biosphere
2.1 The 3.472-3.416 Ga Hooggenoeg Formation, Onverwacht Group
2.1.1 Middle Marker (H1)
2.1.2 Cherts H3c and H5c
2.1.3 Upper Hooggenoeg Hyaloclastites and Basalts
2.2 The 3.416-3.334 Ga Kromberg Formation, Onverwacht Group
2.2.1 Buck Reef Chert (K1)
2.2.2 Josefsdal Chert (K3c)
2.2.2.1 Carbonaceous Laminations
2.2.2.2 Clotted Carbonaceous Textures
2.2.3 Lower Kromberg Basalts
2.2.4 Other Kromberg Cherts
2.3 The 3.334-3.258 Ga Mendon Formation, Onverwacht Group
2.4 The 3.26-3.23 Ga Fig Tree Group
2.4.1 3.260 Ga Swartkoppie and 3.245 Sheba Formations
2.5 The 3.22 Ga Moodies Group
2.5.1 Microbial Mats
2.5.2 Coelobionts
2.5.3 Acritarchs
3. Discussion
3.1 Distribution of Traces of Ancient Life in the Barberton Greenstone Belt
3.2 Microbial Biomes of the BGB
3.3 Hydrothermal Habitats From the Paleoarchean
4. Conclusions
Acknowledgments
References
Subject Index
Author Index