CEE 437 Lecture CEE 437 Lecture 22

Earth Materials IEarth Materials IEarth Structure Earth Structure

and Mineralsand MineralsThomas DoeThomas Doe

OutlineOutline

Global tectonic settingGlobal tectonic setting Rock cycleRock cycle Rock forming mineralsRock forming minerals Paper 1Paper 1

AnnouncementsAnnouncements

Paper and Quiz SchedulePaper and Quiz Schedule Quiz 1 10-11Quiz 1 10-11 Paper 1 10-18Paper 1 10-18

Field TripsField Trips Oct 23Oct 23 Nov 20Nov 20

Office and HoursOffice and Hours 132 G More132 G More Before class (3:00) or by appointmentBefore class (3:00) or by appointment

Global StructureGlobal Structure

Based mainly on seismic information Based mainly on seismic information and meteorite compositionsand meteorite compositions

Crust ~25-75 km depending varying Crust ~25-75 km depending varying under continents and oceansunder continents and oceans

Velocity Variation with Velocity Variation with DepthDepth

Global StructureGlobal Structure

Development of Plate Development of Plate TectonicsTectonics

Evidence from ocean floor Evidence from ocean floor magnetism and agesmagnetism and ages

Evidence from seismicityEvidence from seismicity Evidence from cross-continent Evidence from cross-continent

correlations of rockscorrelations of rocks

Global SeismicityGlobal Seismicity

Benioff ZoneBenioff Zone

Seafloor Spreading — Seafloor Spreading — Sediment AgesSediment Ages

Sea-floor SpreadingSea-floor Spreading

Mantle convection drivenMantle convection driven

Evolution of Spreading Evolution of Spreading Sea Floor — Atlantic Sea Floor — Atlantic

AnalogAnalog

Convergent MarginsConvergent Margins

Ocean to ContinentOcean to Continent Continent to ContinentContinent to Continent

Convergent Margin - Convergent Margin - Continental Continental

Subduction Zone – Subduction Zone – Island ArcIsland Arc

Evolution of Continents Evolution of Continents — North American — North American

CratonCraton

North American North American AccretionAccretion

Rock CycleRock 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 DifferentiationMineral Differentiation Plate tectonics and Igneous ProcessesPlate tectonics and Igneous Processes

selective melting, selective recrystallizationselective melting, selective recrystallization differentiation by densitydifferentiation by density

Weathering and ErosionWeathering and Erosion Selective weatheringSelective weathering Concentration of quartz (pure Si0Concentration of quartz (pure Si022)) Conversion of alumino-silicates to claysConversion of alumino-silicates to clays Concentration of soluble residues in seawaterConcentration of soluble residues in seawater

DepositionDeposition Courser materials near sediment sourceCourser materials near sediment source Finer materials far from sediment sourceFiner materials far from sediment source Redeposition of salts and solutes by evaporative Redeposition of salts and solutes by evaporative

(Na,KCl; CaSO(Na,KCl; CaSO44) or biological processes (CaCO) or biological processes (CaCO3,; 3,; ) )

Differentiation of Crustal Differentiation of Crustal CompositionComposition

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 SeriesBowen Reaction Series

How to get many different rocks How to get many different rocks from one melt composition?from one melt composition?

Differentiation by selective Differentiation by selective crystallization and removal from crystallization and removal from systemsystem

Bowen’s Reaction SeriesBowen’s Reaction Series

Crustal CompositionCrustal Composition Main Elemental GroupsMain Elemental Groups

SilicaSilica AluminumAluminum Ferro-MagnesianFerro-Magnesian Ca, Na, KCa, Na, K

Elemental FatesElemental Fates

Silicon tends to concentrate in crust Silicon tends to concentrate in crust — quartz is very long lived— quartz is very long lived

Aluminum — transforms from Aluminum — transforms from feldspars to claysfeldspars to clays

Mica — transform to clays Mica — transform to clays Fe-Mg-Ca-Na-K concentrate in some Fe-Mg-Ca-Na-K concentrate in some

clays and micas, concentrate in clays and micas, concentrate in oceans in biosphereoceans in biosphere

Differentiation in Differentiation in Crystallization Versus Crystallization Versus

Differentiation in Differentiation in WeatheringWeathering

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 Sedimentary DifferentiationDifferentiation

Sorting by Deposition MediumSorting by Deposition Medium Sorting by EnergySorting by Energy

Mineral DefinitionMineral Definition

Naturally occurring material with Naturally occurring material with unique combination of chemical unique combination of chemical composition and crystalline composition and crystalline structurestructure

Natural non-minerals — glasses, Natural non-minerals — glasses, coal, amorphous silicacoal, amorphous silica

Pseudomorphs: diamond:graphitePseudomorphs: diamond:graphite

Galena, PbS Graphite, C

Crystalline Structure of Crystalline Structure of CalciteCalcite

Crystalline Symmetry Crystalline Symmetry GroupsGroups

Isomorphic Crystal Forms, Isomorphic Crystal Forms, Cubic SystemCubic System

Physical PropertiesPhysical Properties

Density (Gravity)Density (Gravity) Electrical Conductivity (Resisitivity)Electrical Conductivity (Resisitivity) Thermal ExpansionThermal Expansion StrengthStrength Elasticity (Mechanical properties, Elasticity (Mechanical properties,

Seismic/Acoustic VelocitySeismic/Acoustic Velocity Rheology (Plasticity,Viscosity)Rheology (Plasticity,Viscosity)

Discussion: How to Rock Discussion: How to Rock Properties Relate to Properties Relate to Mineral StructureMineral Structure

How will anisotropy vary with How will anisotropy vary with crystal symmetry class?crystal symmetry class? Rock Salt versus Quartz?Rock Salt versus Quartz?

How will aggregates of minerals How will aggregates of minerals (with same mineral behave?(with same mineral behave? Cubic versus non cubicCubic versus non cubic Rock fabricRock fabric Material property contrastsMaterial property contrasts

Rock Forming MineralsRock Forming Minerals

Composition of CrustComposition of Crust Dominantly O, Si, Fe, Mg, Ca, Na, KDominantly O, Si, Fe, Mg, Ca, Na, K Near surface importance of bio-Near surface importance of bio-

processesprocesses Silicates from inorganic processesSilicates from inorganic processes Carbonates mainly from shell-forming Carbonates mainly from shell-forming

organismsorganisms

Crustal CompositionCrustal Composition Main Elemental GroupsMain Elemental Groups

SilicaSilica AluminumAluminum Ferro-MagnesianFerro-Magnesian Ca, Na, KCa, Na, K

Major Silicate GroupsMajor Silicate Groups

Silicon TetrahedronSilicon Tetrahedron separate tetrahedra — olivineseparate tetrahedra — olivine single chains — pyroxenesingle chains — pyroxene double chains — amphiboledouble chains — amphibole sheet silicates — micas and clayssheet silicates — micas and clays framework silicates — feldspars (with Al framework silicates — feldspars (with Al

substitution), quartz as pure silicasubstitution), quartz as pure silica

Silica TetrahedronSilica Tetrahedron

Forms of SilicatesForms of Silicates

Deformation Deformation MechanismsMechanisms

Effects on Physical Effects on Physical PropertiesProperties

AnisotropyAnisotropy Properties differ by directionProperties differ by direction

HeterogeneityHeterogeneity Properties vary by locationProperties vary by location

Mineral properties may have strong Mineral properties may have strong anisotropy when crystals are alignedanisotropy when crystals are aligned

Heterogeneity may have strong mechanical Heterogeneity may have strong mechanical effects when different minerals have effects when different minerals have different deformation propertiesdifferent deformation properties

Minerals versus RocksMinerals versus Rocks Minerals ElementsMinerals Elements

Anisotropy from crystal Anisotropy from crystal structurestructure

Elastic PropertiesElastic Properties Thermal PropertiesThermal Properties Optical PropertiesOptical Properties

DeformationDeformation Shear transformationsShear transformations DislocationsDislocations

Rock ElementsRock Elements IntragranularIntragranular

Anisotropy from fabricAnisotropy from fabric Crystal anisotropy if Crystal anisotropy if

preferred orientationpreferred orientation Anisotropy from Anisotropy from

bedding, foliation, flow bedding, foliation, flow structuresstructures

IntergranularIntergranular CementsCements MicrocracksMicrocracks

HeterogeneityHeterogeneity Mineral compositionMineral composition Other segregration Other segregration

processesprocesses

Clay MineralsClay Minerals

Extremely Important Mineral GroupExtremely Important Mineral Group SealsSeals StabilityStability Pore pressurePore pressure Chemical interactionChemical interaction SwellingSwelling SlakingSlaking

Confusion as both “Size” and Confusion as both “Size” and “Mineral” Classification“Mineral” Classification

Clay SourcesClay Sources

WeatheringWeathering Hydrothermal AlterationHydrothermal Alteration DepositionDeposition Clay TransformationsClay Transformations

Feldspar Feldspar Illite Illite Ferro-Magnesian Ferro-Magnesian Chlorite Chlorite Volcanics (alkaline conditions) Volcanics (alkaline conditions) Smectite Smectite Volcanics (acidic conditions) Volcanics (acidic conditions) Kaolinite Kaolinite

Bentonite: plastic, highly swellingBentonite: plastic, highly swelling

Clay UnitsClay Units

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

Two and Three-Layer Clay Two and Three-Layer Clay StructureStructure

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

Mixed Layer ClaysMixed Layer Clays

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

TopicsTopics

Mineral DefinitionMineral Definition Rock Forming MineralsRock Forming Minerals Physical Proprieties of MineralsPhysical Proprieties of Minerals Mineral IdentificationMineral Identification Mineral LabMineral Lab

Clay Viewed from Clay Viewed from Electron MicroscopeElectron Microscope

Mineral IdentificationMineral Identification

DensityDensity HardnessHardness Color, luster (metallic, non-metalic, Color, luster (metallic, non-metalic,

semi-metallic)semi-metallic) Crystalline habitCrystalline habit CleavageCleavage Optical microscopyOptical microscopy Mineral chemistry, x-ray diffractionMineral chemistry, x-ray diffraction

Hardness ScaleHardness Scale

X-Ray DiffractionX-Ray Diffraction

spacing lattice,angle incidence,wavelength,sin2

dd

Bragg’s Law

Weathering FatesWeathering Fates

Feldspars to clays (clays, shales)Feldspars to clays (clays, shales) Quartz endures (siltstones, sandstones)Quartz endures (siltstones, sandstones) Calcium recirculated into carbonate Calcium recirculated into carbonate

minerals by organic processes minerals by organic processes (limestones)(limestones)

Consequence:Consequence: Over time, evolution of less dense more Over time, evolution of less dense more

silicic continental crustsilicic continental crust

Engineering ImplicationsEngineering Implications

““Style” of geology and geo-engineering Style” of geology and geo-engineering problems varies with plate tectonic problems varies with plate tectonic settingsetting Faulting, and structural complexityFaulting, and structural complexity

Maturity of materials varies with plate Maturity of materials varies with plate tectonics settingtectonics setting Higher degree of more stable materials from Higher degree of more stable materials from

sorting by weatheringsorting by weathering Geohazards vary with plate tectonic Geohazards vary with plate tectonic

settingsetting

Paper, 10-18Paper, 10-18 1. Physical Properties of Rocks and Crystals1. Physical Properties of Rocks and Crystals Prepare a table of material properties for selected rock-forming Prepare a table of material properties for selected rock-forming

minerals and corresponding rock types. You should use both library minerals and corresponding rock types. You should use both library and web sources. Choose among the following concepts:and web sources. Choose among the following concepts:

Role of mineral anisotropy and rock heterogeneity on strength and Role of mineral anisotropy and rock heterogeneity on strength and deformabilitydeformability

Role of mineral anisotropy and rock heterogeneity on mechanical Role of mineral anisotropy and rock heterogeneity on mechanical effects during rock heating and cooling (consider qualitatively the effects during rock heating and cooling (consider qualitatively the influence of differential responses)influence of differential responses)

Useful Ref: Carmichael, Handbook of Physical Properties of Useful Ref: Carmichael, Handbook of Physical Properties of Rocks (CRC Rocks (CRC Press)Press)

2. Structure and Properties of Sheet Silicates2. Structure and Properties of Sheet Silicates Define clay versus micaDefine clay versus mica Physical properties of claysPhysical properties of clays Differentiation of clays typesDifferentiation of clays types ““Bad Actors”Bad Actors” 3. The Rock Cycle and Its Influence on Rock Material Properties (non-3. The Rock Cycle and Its Influence on Rock Material Properties (non-

geologists)geologists) Differentiation by Plate Tectonics, Weathering and DepositionDifferentiation by Plate Tectonics, Weathering and Deposition Track clays through the Rock CycleTrack clays through the Rock Cycle 4. Other topic (pre-approval recommended)4. Other topic (pre-approval recommended)