CEE 437 Lecture 2 Earth Materials I Earth Structure and Minerals Thomas Doe

Outline Global tectonic setting Global tectonic setting Rock cycle Rock cycle Rock forming minerals Rock forming minerals Paper 1 Paper 1

Announcements Paper and Quiz Schedule Paper and Quiz Schedule Quiz Quiz Paper Paper Field Trips Field Trips Oct 23 Oct 23 Nov 20 Nov 20 Office and Hours Office and Hours 132 G More 132 G More Before class (3:00) or by appointment Before class (3:00) or by appointment

Global Structure Based mainly on seismic information and meteorite compositions Based mainly on seismic information and meteorite compositions Crust ~25-75 km depending varying under continents and oceans Crust ~25-75 km depending varying under continents and oceans

Velocity Variation with Depth

Global Structure

Development of Plate Tectonics Evidence from ocean floor magnetism and ages Evidence from ocean floor magnetism and ages Evidence from seismicity Evidence from seismicity Evidence from cross-continent correlations of rocks Evidence from cross-continent correlations of rocks

Global Seismicity

Benioff Zone

Seafloor Spreading — Sediment Ages

Sea-floor Spreading Mantle convection driven Mantle convection driven

Evolution of Spreading Sea Floor — Atlantic Analog

Convergent Margins Ocean to Continent Ocean to Continent Continent to Continent Continent to Continent

Convergent Margin - Continental

Subduction Zone – Island Arc Subduction Zone – Island Arc

Evolution of Continents — North American Craton

North American Accretion

Rock Cycle Metamorphic Rocks Sedimentary Rocks Igneous Rocks Sediments Lithification Magma Weathering, Erosion Burial, metamorphism, recrystallization Melting Crystallization at depth or extrusion at surface Burial, metamorphism, recrystallization

Mineral Differentiation Plate tectonics and Igneous Processes Plate tectonics and Igneous Processes selective melting, selective recrystallization selective melting, selective recrystallization differentiation by density differentiation by density Weathering and Erosion Weathering and Erosion Selective weathering Selective weathering Concentration of quartz (pure Si0 2 ) Concentration of quartz (pure Si0 2 ) Conversion of alumino-silicates to clays Conversion of alumino-silicates to clays Concentration of soluble residues in seawater Concentration of soluble residues in seawater Deposition Deposition Courser materials near sediment source Courser materials near sediment source Finer materials far from sediment source Finer materials far from sediment source Redeposition of salts and solutes by evaporative (Na,KCl; CaSO 4 ) or biological processes (CaCO 3,; ) Redeposition of salts and solutes by evaporative (Na,KCl; CaSO 4 ) or biological processes (CaCO 3,; )

Differentiation of Crustal Composition Weathering differentiating towards higher Silica Preferential melting of high-silica materials Concentration of C, Ca, Na, K in sea and air Original basaltic composition of crust Carbonate concentrated by organic processes

Bowen Reaction Series How to get many different rocks from one melt composition? How to get many different rocks from one melt composition? Differentiation by selective crystallization and removal from system Differentiation by selective crystallization and removal from system

Bowen’s Reaction Series

Crustal Composition Main Elemental Groups Main Elemental Groups Silica Silica Aluminum Aluminum Ferro-Magnesian Ferro-Magnesian Ca, Na, K Ca, Na, K

Elemental Fates Silicon tends to concentrate in crust — quartz is very long lived Silicon tends to concentrate in crust — quartz is very long lived Aluminum — transforms from feldspars to clays Aluminum — transforms from feldspars to clays Mica — transform to clays Mica — transform to clays Fe-Mg-Ca-Na-K concentrate in some clays and micas, concentrate in oceans in biosphere Fe-Mg-Ca-Na-K concentrate in some clays and micas, concentrate in oceans in biosphere

Differentiation in Crystallization Versus Differentiation in Weathering Olivine Pyroxene Amphibole Biotite Muscovite Quartz Ca,Mg Feldspars K- Feldspars High Temperature, Low Silica, Hi Fe Mg Low Temperature, High Silica, Low Fe Mg Fast Weathering Slow Weathering

Sedimentary Differentiation Sorting by Deposition Medium Sorting by Deposition Medium Sorting by Energy Sorting by Energy

Mineral Definition Naturally occurring material with unique combination of chemical composition and crystalline structure Naturally occurring material with unique combination of chemical composition and crystalline structure Natural non-minerals — glasses, coal, amorphous silica Natural non-minerals — glasses, coal, amorphous silica Pseudomorphs: diamond:graphite Pseudomorphs: diamond:graphite

Galena, PbS Graphite, C

Crystalline Structure of Calcite

Crystalline Symmetry Groups

Isomorphic Crystal Forms, Cubic System

Physical Properties Density (Gravity) Density (Gravity) Electrical Conductivity (Resisitivity) Electrical Conductivity (Resisitivity) Thermal Expansion Thermal Expansion Strength Strength Elasticity (Mechanical properties, Elasticity (Mechanical properties, Seismic/Acoustic Velocity Seismic/Acoustic Velocity Rheology (Plasticity,Viscosity) Rheology (Plasticity,Viscosity)

Discussion: How to Rock Properties Relate to Mineral Structure How will anisotropy vary with crystal symmetry class? How will anisotropy vary with crystal symmetry class? Rock Salt versus Quartz? Rock Salt versus Quartz? How will aggregates of minerals (with same mineral behave? How will aggregates of minerals (with same mineral behave? Cubic versus non cubic Cubic versus non cubic Rock fabric Rock fabric Material property contrasts Material property contrasts

Rock Forming Minerals Composition of Crust Composition of Crust Dominantly O, Si, Fe, Mg, Ca, Na, K Dominantly O, Si, Fe, Mg, Ca, Na, K Near surface importance of bio-processes Near surface importance of bio-processes Silicates from inorganic processes Silicates from inorganic processes Carbonates mainly from shell-forming organisms Carbonates mainly from shell-forming organisms

Crustal Composition Main Elemental Groups Main Elemental Groups Silica Silica Aluminum Aluminum Ferro-Magnesian Ferro-Magnesian Ca, Na, K Ca, Na, K

Major Silicate Groups Silicon Tetrahedron Silicon Tetrahedron separate tetrahedra — olivine separate tetrahedra — olivine single chains — pyroxene single chains — pyroxene double chains — amphibole double chains — amphibole sheet silicates — micas and clays sheet silicates — micas and clays framework silicates — feldspars (with Al substitution), quartz as pure silica framework silicates — feldspars (with Al substitution), quartz as pure silica

Silica Tetrahedron

Forms of Silicates

Deformation Mechanisms

Effects on Physical Properties Anisotropy Anisotropy Properties differ by direction Properties differ by direction Heterogeneity Heterogeneity Properties vary by location Properties vary by location Mineral properties may have strong anisotropy when crystals are aligned Mineral properties may have strong anisotropy when crystals are aligned Heterogeneity may have strong mechanical effects when different minerals have different deformation properties Heterogeneity may have strong mechanical effects when different minerals have different deformation properties

Minerals versus Rocks Minerals Elements Minerals Elements Anisotropy from crystal structure Anisotropy from crystal structure Elastic Properties Elastic Properties Thermal Properties Thermal Properties Optical Properties Optical Properties Deformation Deformation Shear transformations Shear transformations Dislocations Dislocations Rock Elements Intragranular Anisotropy from fabric Crystal anisotropy if preferred orientation Anisotropy from bedding, foliation, flow structures Intergranular Cements Microcracks Heterogeneity Mineral composition Other segregration processes

Clay Minerals Extremely Important Mineral Group Extremely Important Mineral Group Seals Seals Stability Stability Pore pressure Pore pressure Chemical interaction Chemical interaction Swelling Swelling Slaking Slaking Confusion as both “Size” and “Mineral” Classification Confusion as both “Size” and “Mineral” Classification

Clay Sources Weathering Weathering Hydrothermal Alteration Hydrothermal Alteration Deposition Deposition Clay Transformations Clay Transformations Feldspar  Illite Feldspar  Illite Ferro-Magnesian  Chlorite Ferro-Magnesian  Chlorite Volcanics (alkaline conditions)  Smectite Volcanics (alkaline conditions)  Smectite Volcanics (acidic conditions)  Kaolinite Volcanics (acidic conditions)  Kaolinite Bentonite: plastic, highly swelling Bentonite: plastic, highly swelling

Clay Units From West, Geology Applied to Engineering, Prentice Hall, 1995)

Two and Three-Layer Clay Structure From West, Geology Applied to Engineering, Prentice Hall, 1995)

Mixed Layer Clays From West, Geology Applied to Engineering, Prentice Hall, 1995)

Topics Mineral Definition Mineral Definition Rock Forming Minerals Rock Forming Minerals Physical Proprieties of Minerals Physical Proprieties of Minerals Mineral Identification Mineral Identification Mineral Lab Mineral Lab

Clay Viewed from Electron Microscope

Mineral Identification Density Density Hardness Hardness Color, luster (metallic, non-metalic, semi- metallic) Color, luster (metallic, non-metalic, semi- metallic) Crystalline habit Crystalline habit Cleavage Cleavage Optical microscopy Optical microscopy Mineral chemistry, x-ray diffraction Mineral chemistry, x-ray diffraction

Hardness Scale

X-Ray Diffraction Bragg’s Law

Weathering Fates Feldspars to clays (clays, shales) Feldspars to clays (clays, shales) Quartz endures (siltstones, sandstones) Quartz endures (siltstones, sandstones) Calcium recirculated into carbonate minerals by organic processes (limestones) Calcium recirculated into carbonate minerals by organic processes (limestones) Consequence: Consequence: Over time, evolution of less dense more silicic continental crust Over time, evolution of less dense more silicic continental crust

Engineering Implications “Style” of geology and geo-engineering problems varies with plate tectonic setting “Style” of geology and geo-engineering problems varies with plate tectonic setting Faulting, and structural complexity Faulting, and structural complexity Maturity of materials varies with plate tectonics setting Maturity of materials varies with plate tectonics setting Higher degree of more stable materials from sorting by weathering Higher degree of more stable materials from sorting by weathering Geohazards vary with plate tectonic setting Geohazards vary with plate tectonic setting

Paper, Physical Properties of Rocks and Crystals 1. Physical Properties of Rocks and Crystals Prepare a table of material properties for selected rock-forming minerals and corresponding rock types. You should use both library and web sources. Choose among the following concepts: Prepare a table of material properties for selected rock-forming minerals and corresponding rock types. You should use both library and web sources. Choose among the following concepts: Role of mineral anisotropy and rock heterogeneity on strength and deformability Role of mineral anisotropy and rock heterogeneity on strength and deformability Role of mineral anisotropy and rock heterogeneity on mechanical effects during rock heating and cooling (consider qualitatively the influence of differential responses) Role of mineral anisotropy and rock heterogeneity on mechanical effects during rock heating and cooling (consider qualitatively the influence of differential responses) Useful Ref: Carmichael, Handbook of Physical Properties of Rocks (CRC Press) Useful Ref: Carmichael, Handbook of Physical Properties of Rocks (CRC Press) 2. Structure and Properties of Sheet Silicates 2. Structure and Properties of Sheet Silicates Define clay versus mica Define clay versus mica Physical properties of clays Physical properties of clays Differentiation of clays types Differentiation of clays types “Bad Actors” “Bad Actors” 3. The Rock Cycle and Its Influence on Rock Material Properties (non-geologists) 3. The Rock Cycle and Its Influence on Rock Material Properties (non-geologists) Differentiation by Plate Tectonics, Weathering and Deposition Differentiation by Plate Tectonics, Weathering and Deposition Track clays through the Rock Cycle Track clays through the Rock Cycle 4. Other topic (pre-approval recommended) 4. Other topic (pre-approval recommended)