Title: CEE 437 Lecture 2 Earth Materials I Earth Structure and Minerals
1CEE 437 Lecture 2Earth Materials IEarth
Structure and Minerals
2Outline
- Global tectonic setting
- Rock cycle
- Rock forming minerals
- Paper 1
3Global Structure
- Based mainly on seismic information and meteorite
compositions - Crust 25-75 km depending varying under
continents and oceans
4Velocity Variation with Depth
5Global Structure
6Development of Plate Tectonics
- Evidence from ocean floor magnetism and ages
- Evidence from seismicity
- Evidence from cross-continent correlations of
rocks
7Global Seismicity
8Benioff Zone
9Seafloor Spreading Sediment Ages
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11Sea-floor Spreading
12Evolution of Spreading Sea Floor Atlantic Analog
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14Convergent Margins
- Ocean to Continent
- Continent to Continent
15Convergent Margin - Continental
16 Subduction Zone Island Arc
17Evolution of Continents North American Craton
18North American Accretion
19Rock 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
20Mineral 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,
)
21Differentiation 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
22Bowen Reaction Series
- How to get many different rocks from one melt
composition? - Differentiation by selective crystallization and
removal from system
23Bowens Reaction Series
24Crustal Composition
- Main Elemental Groups
- Silica
- Aluminum
- Ferro-Magnesian
- Ca, Na, K
25Elemental 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
26Differentiation 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
27Sedimentary Differentiation
- Sorting by Deposition Medium
- Sorting by Energy
28Mineral Definition
- Naturally occurring material with unique
combination of chemical composition and
crystalline structure - Natural non-minerals glasses, coal, amorphous
silica - Pseudomorphs diamondgraphite
29Graphite, C
Galena, PbS
30Crystalline Structure of Calcite
31Crystalline Symmetry Groups
32Isomorphic Crystal Forms, Cubic System
33Physical Properties
- Density (Gravity)
- Electrical Conductivity (Resisitivity)
- Thermal Expansion
- Strength
- Elasticity (Mechanical properties,
- Seismic/Acoustic Velocity
- Rheology (Plasticity,Viscosity)
34Properties and Mineral Symmetry
35Tensor Properties of Crystals
Cubic Group
Lower Symmetry Groups
General Form for Heat Flow (for example)
36Discussion 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
37Rock 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
38Crustal Composition
- Main Elemental Groups
- Silica
- Aluminum
- Ferro-Magnesian
- Ca, Na, K
39Major 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
40Silica Tetrahedron
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42Forms of Silicates
43Deformation Mechanisms
44Effects 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
45Minerals 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
46Clay Minerals
- Extremely Important Mineral Group
- Seals
- Stability
- Pore pressure
- Chemical interaction
- Swelling
- Slaking
- Confusion as both Size and Mineral
Classification
47Clay Sources
- Weathering
- Hydrothermal Alteration
- Deposition
- Clay Transformations
- Feldspar ? Illite
- Ferro-Magnesian ? Chlorite
- Volcanics (alkaline conditions) ? Smectite
- Volcanics (acidic conditions) ? Kaolinite
- Bentonite plastic, highly swelling
48Clay Units
From West, Geology Applied to Engineering,
Prentice Hall, 1995)
49Two and Three-Layer Clay Structure
From West, Geology Applied to Engineering,
Prentice Hall, 1995)
50Mixed Layer Clays
From West, Geology Applied to Engineering,
Prentice Hall, 1995)
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52Topics
- Mineral Definition
- Rock Forming Minerals
- Physical Proprieties of Minerals
- Mineral Identification
- Mineral Lab
53Clay Viewed from Electron Microscope
54Mineral Identification
- Density
- Hardness
- Color, luster (metallic, non-metalic,
semi-metallic) - Crystalline habit
- Cleavage
- Optical microscopy
- Mineral chemistry, x-ray diffraction
55Hardness Scale
56X-Ray Diffraction
Braggs Law
57Weathering 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
58Engineering 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
59Paper 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.
60Undergrad 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
61Grad Requirements
- Add Goodman Engineer as Artist (unless discuss
with us otherwise)
62Paper 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.
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