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CEE 437 Lecture 2 Earth Materials I Earth Structure and Minerals

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Elemental Fates. Silicon tends to concentrate in crust quartz is very long lived ... Weathering Fates. Feldspars to clays (clays, shales) Quartz endures ... – PowerPoint PPT presentation

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Title: CEE 437 Lecture 2 Earth Materials I Earth Structure and Minerals


1
CEE 437 Lecture 2Earth Materials IEarth
Structure and Minerals
  • Thomas Doe

2
Outline
  • Global tectonic setting
  • Rock cycle
  • Rock forming minerals
  • Paper 1

3
Global Structure
  • Based mainly on seismic information and meteorite
    compositions
  • Crust 25-75 km depending varying under
    continents and oceans

4
Velocity Variation with Depth
5
Global Structure
6
Development of Plate Tectonics
  • Evidence from ocean floor magnetism and ages
  • Evidence from seismicity
  • Evidence from cross-continent correlations of
    rocks

7
Global Seismicity
8
Benioff Zone
9
Seafloor Spreading Sediment Ages
10
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11
Sea-floor Spreading
  • Mantle convection driven

12
Evolution of Spreading Sea Floor Atlantic Analog
13
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14
Convergent Margins
  • Ocean to Continent
  • Continent to Continent

15
Convergent Margin - Continental
16
Subduction Zone Island Arc
17
Evolution of Continents North American Craton
18
North American Accretion
19
Rock Cycle
Crystallization at depth or extrusion at surface
Magma
Melting
Igneous Rocks
Burial, metamorphism, recrystallization
Metamorphic Rocks
Weathering, Erosion
Sediments
Burial, metamorphism, recrystallization
Sedimentary Rocks
Lithification
20
Mineral Differentiation
  • Plate tectonics and Igneous Processes
  • selective melting, selective recrystallization
  • differentiation by density
  • Weathering and Erosion
  • Selective weathering
  • Concentration of quartz (pure Si02)
  • Conversion of alumino-silicates to clays
  • Concentration of soluble residues in seawater
  • Deposition
  • Courser materials near sediment source
  • Finer materials far from sediment source
  • Redeposition of salts and solutes by evaporative
    (Na,KCl CaSO4) or biological processes (CaCO3,
    )

21
Differentiation of Crustal Composition
Weathering differentiating towards higher Silica
Carbonate concentrated by organic processes
Preferential melting of high-silica materials
Original basaltic composition of crust
Concentration of C, Ca, Na, K in sea and air
22
Bowen Reaction Series
  • How to get many different rocks from one melt
    composition?
  • Differentiation by selective crystallization and
    removal from system

23
Bowens Reaction Series
24
Crustal Composition
  • Main Elemental Groups
  • Silica
  • Aluminum
  • Ferro-Magnesian
  • Ca, Na, K

25
Elemental Fates
  • Silicon tends to concentrate in crust quartz is
    very long lived
  • Aluminum transforms from feldspars to clays
  • Mica transform to clays
  • Fe-Mg-Ca-Na-K concentrate in some clays and
    micas, concentrate in oceans in biosphere

26
Differentiation in Crystallization Versus
Differentiation in Weathering
Slow Weathering
Quartz
Low Temperature, High Silica, Low Fe Mg
Muscovite
K-Feldspars
Biotite
Amphibole
Ca,Mg Feldspars
High Temperature, Low Silica, Hi Fe Mg
Pyroxene
Olivine
Fast Weathering
27
Sedimentary Differentiation
  • Sorting by Deposition Medium
  • Sorting by Energy

28
Mineral Definition
  • Naturally occurring material with unique
    combination of chemical composition and
    crystalline structure
  • Natural non-minerals glasses, coal, amorphous
    silica
  • Pseudomorphs diamondgraphite

29
Graphite, C
Galena, PbS
30
Crystalline Structure of Calcite
31
Crystalline Symmetry Groups
32
Isomorphic Crystal Forms, Cubic System
33
Physical Properties
  • Density (Gravity)
  • Electrical Conductivity (Resisitivity)
  • Thermal Expansion
  • Strength
  • Elasticity (Mechanical properties,
  • Seismic/Acoustic Velocity
  • Rheology (Plasticity,Viscosity)

34
Properties and Mineral Symmetry
35
Tensor Properties of Crystals
Cubic Group
Lower Symmetry Groups
General Form for Heat Flow (for example)
36
Discussion How to Rock Properties Relate to
Mineral Structure
  • How will anisotropy vary with crystal symmetry
    class?
  • Rock Salt versus Quartz?
  • How will aggregates of minerals (with same
    mineral behave?
  • Cubic versus non cubic
  • Rock fabric
  • Material property contrasts

37
Rock Forming Minerals
  • Composition of Crust
  • Dominantly O, Si, Fe, Mg, Ca, Na, K
  • Near surface importance of bio-processes
  • Silicates from inorganic processes
  • Carbonates mainly from shell-forming organisms

38
Crustal Composition
  • Main Elemental Groups
  • Silica
  • Aluminum
  • Ferro-Magnesian
  • Ca, Na, K

39
Major Silicate Groups
  • Silicon Tetrahedron
  • separate tetrahedra olivine
  • single chains pyroxene
  • double chains amphibole
  • sheet silicates micas and clays
  • framework silicates feldspars (with Al
    substitution), quartz as pure silica

40
Silica Tetrahedron
41
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42
Forms of Silicates
43
Deformation Mechanisms
44
Effects on Physical Properties
  • Anisotropy
  • Properties differ by direction
  • Heterogeneity
  • Properties vary by location
  • Mineral properties may have strong anisotropy
    when crystals are aligned
  • Heterogeneity may have strong mechanical effects
    when different minerals have different
    deformation properties

45
Minerals versus Rocks
  • Minerals Elements
  • Anisotropy from crystal structure
  • Elastic Properties
  • Thermal Properties
  • Optical Properties
  • Deformation
  • Shear transformations
  • 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

46
Clay Minerals
  • Extremely Important Mineral Group
  • Seals
  • Stability
  • Pore pressure
  • Chemical interaction
  • Swelling
  • Slaking
  • Confusion as both Size and Mineral
    Classification

47
Clay Sources
  • Weathering
  • Hydrothermal Alteration
  • Deposition
  • Clay Transformations
  • Feldspar ? Illite
  • Ferro-Magnesian ? Chlorite
  • Volcanics (alkaline conditions) ? Smectite
  • Volcanics (acidic conditions) ? Kaolinite
  • Bentonite plastic, highly swelling

48
Clay Units
From West, Geology Applied to Engineering,
Prentice Hall, 1995)
49
Two and Three-Layer Clay Structure
From West, Geology Applied to Engineering,
Prentice Hall, 1995)
50
Mixed Layer Clays
From West, Geology Applied to Engineering,
Prentice Hall, 1995)
51
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52
Topics
  • Mineral Definition
  • Rock Forming Minerals
  • Physical Proprieties of Minerals
  • Mineral Identification
  • Mineral Lab

53
Clay Viewed from Electron Microscope
54
Mineral Identification
  • Density
  • Hardness
  • Color, luster (metallic, non-metalic,
    semi-metallic)
  • Crystalline habit
  • Cleavage
  • Optical microscopy
  • Mineral chemistry, x-ray diffraction

55
Hardness Scale
56
X-Ray Diffraction
Braggs Law
57
Weathering Fates
  • Feldspars to clays (clays, shales)
  • Quartz endures (siltstones, sandstones)
  • Calcium recirculated into carbonate minerals by
    organic processes (limestones)
  • Consequence
  • Over time, evolution of less dense more silicic
    continental crust

58
Engineering Implications
  • Style of geology and geo-engineering problems
    varies with plate tectonic setting
  • Faulting, and structural complexity
  • Maturity of materials varies with plate tectonics
    setting
  • Higher degree of more stable materials from
    sorting by weathering
  • Geohazards vary with plate tectonic setting

59
Paper and Paper Topics
  • Paper I Topics
  • Columbia River Basalts Origin, Structure,
    Hydrologic and Engineering Properties
  • Geology and Engineering Geology of the Snoqualmie
    Pass Quadrangle
  • Clay Minerals Origin, Crystal Structure,
    Engineering Properties
  • 6 Pages, 1.5 space, plus figures, include
    references.

60
Undergrad Presentations
  • 1. Geologic History of Columbia Plateau
  • 2. Geologic History of Olympic Peninsula
  • 3. Coal Mines of Newcastle, Washington
  • 4. Geological Issue Effecting Construction I-5
    through Seattle
  • 5. The Seattle Fault
  • 6. Foundations on Peat
  • 7. Rock Slope Stability Problems in I-90
  • 8. Fracture Image Logging Technologies
  • 9. Tunneling for Sound Transit
  • 10. Engineering Properties of Organic Soils in
    the Puget Sound Area
  • 11. Engineering Properties of Glacial Soils in
    the Puget Sound Area 12. Solute Transport in
    Fractured Rock 13. Economic Minerals of
    Washington State 14. Quarry Mines of Puget Sound
  • 15. Failure of Malpassat Dam
  • 16. Rock Tunnel Failures in the Alps
  • 17. Seattle Watershed Geology

61
Grad Requirements
  • Add Goodman Engineer as Artist (unless discuss
    with us otherwise)

62
Paper and Paper Topics
  • Paper I Topics
  • Columbia River Basalts Origin, Structure,
    Hydrologic and Engineering Properties
  • Geology and Engineering Geology of the Snoqualmie
    Pass Quadrangle
  • Clay Minerals Origin, Crystal Structure,
    Engineering Properties
  • 6 Pages, 1.5 space, plus figures, include
    references.

63
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