CEE 437 Rocks - PowerPoint PPT Presentation

1 / 61
About This Presentation
Title:

CEE 437 Rocks

Description:

Crystallization at depth or extrusion at surface. Burial, ... Basalt greenschist, amphibolite. Non-foliated Metamorphic Rocks. Sandstone Quartzite ... – PowerPoint PPT presentation

Number of Views:54
Avg rating:3.0/5.0
Slides: 62
Provided by: tom98
Category:

less

Transcript and Presenter's Notes

Title: CEE 437 Rocks


1
CEE 437 Rocks!
  • Thomas Doe

2
Outline
  • Igneous Rocks
  • Sedimentary Rocks
  • Metamorphic Rocks
  • Rock Identification Lab

3
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
4
Northwest Igneous and Metamorphic Rocks
Cascade Volcanoes (recent)
Cascade Batholiths (Felsic, Cret-Miocene)
Columbia River Basalts (miocene)
Recent Basaltic Volcanism (Newberry Crater)
Yellowstone Region Acidic Volcanics (Pleistocene
to recent)
Snake River Basalts (pliocene)
5
Geologic Settings for Igneous Rocks
  • Oceanic
  • Hi Fe, Mg, Ca, low Si
  • basalt, gabbro
  • Continental
  • Hi Si, Na, K
  • granite, rhyolite, andesite

6
Igneous Origins
  • Intrusive
  • Batholithic or plutonic phaneritic
  • Dikes or sills that chill rapidly aphanitic
  • Extrusive
  • deposition as melt (lava)
  • pyroclastic
  • tuff
  • tephra
  • pyroclastic flows

7
Identifying Igneous Rocks
  • Chemistry
  • Acidic Basic (more Si, less Si)
  • Texture
  • Aphanitic crystals not visible
  • Phaneritic made of visible crystal components
  • Porphyritic Larger crustals in aphanitic or
    phaneritic ground mass

8
Igneous Rock Classification
Acidic, Felsic
Basic, Mafic
Ultramafic
SERPENTINITE
9
(No Transcript)
10
Magma Generation on Continental Margins
11
Magma Generation in Convergent Continental Plate
Margins
12
Extrusives
  • Viscosity varies with Si and water content
  • Basalt low viscosity
  • Rhyolite high viscosity
  • Rhyolite flows relatively unusual as rhyolite
    does not flow well
  • Explosive
  • Tuffs, pyroclastics

13
Volcano Types
Basaltic low viscosity Hawaii, Columbia
Plateau
Andesitic/Rhyolitic
14
Structures of Basalt Flows
  • Lava Tubes
  • Flow Stratigraphy
  • collonade
  • entablature
  • flow top breccia/scoria

15
Hawaii Basalt Flows
16
Basalt Flow Structures
17
Eruptions of Acid-Rock Volcanoes
18
Rhyolite Dome
19
Caldera
20
Mt. St. Helens Blast Zone
21
Mt. Mazama Ash Distribution
22
Sedimentary Rocks
  • Clastics, Siliciclastics, and Evaporites
  • Clastic rocks, depositional medium, and energy
  • Diagenesis chemical changes after deposition

23
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
24
Sediment Sources
25
Clastic Sedimentary Rocks
  • Clastic broken like iconoclast)
  • Often referred to as Siliciclastics as having Si
    based rock forming minerals
  • Based on grain size and to a lesser extent
    composition
  • Grain size related to energy of depositional
    environment
  • Relationship of medium velocity to maximum grain
    size)

26
Clastic Sedimentary Rocks
  • Clay, muds ? shales, mudstones, claystones
    (difference based on fissility)
  • Silts ? siltstones
  • Sands ? sandstones
  • Gravels ? Conglomerates (Breccia if angular,
    breccia may also be a term for tectonically
    fragmented rock)

27
Weathering Cycle
28
Clastic Sediments
29
Clay Minerals
  • Sheets of linked silica tetrahedra sandwiching
    octahedral layers of gibbsite composition,
    Al2(OH)6, or brucite Mg3(OH)6
  • Major Clay Groups
  • kaolinite single gibbsite layer
  • montmorilloniteweak water bonding between
    layers, moderated by Ca, Na, or K (near-shore
    environments)
  • illite K bonds between layers (off-shore
    environments)
  • bentonite highly expansive, volcanic-derived,
    Na-rich montmorillonite

30
Clay Structure
31
Clay Structure Contd.
Kaolinite
Montmorillonite
Illite
32
Lithification
  • Cementation
  • deposition of a material different from clasts
  • Crystallization
  • crystal growth on clasts to fill pore space
  • Compaction
  • Diagenesis
  • Early post-depositional chemical transformation
    of sediments, e.g. calcite to dolomite

33
Carbonates
  • Generally like siliciclastics carbonate muds,
    sands, etc.
  • Often deposited in reefs
  • Major portion of world oil deposits
  • Properties depend strongly on post-depositional
    pore chemistry
  • Cementation
  • Dissolution

34
Carbonate Environments
35
Evaporites
  • Rock salt (NaCl), Gypsum-Anhydrite (CaSO4),
    Sylvite (KCl)
  • Deposition in regions where evaporation exceeds
    recharge
  • desert lakes
  • restricted seas (Mediterranean)
  • lagoons, back-reef areas
  • Subject to flow and diapirism

36
Other Sedimentary Rocks
  • Chert finely crystalline silica
  • as replacement/diagenetic nodules
  • as bedded material from silica-shelled biota
  • Coal
  • Derived from vegetation
  • Banded Iron Formation
  • Likely bacteria derived, mainly Pre-Cambrian

37
Sedimentary Rocks and Rock Properties
  • Properties for a given geologic description vary
    wildly based on cementation, porosity and other
    diagenetic factors.
  • Properties can be strong anisotropic and
    heterogeneous based on bedding

38
Depositional Environments
  • Synchroneity of deposition of different rock
    types
  • Sedimentary facies
  • A rock unit is not everywhere the same age
    Bright Angel Shale
  • Related to energy of environment
  • (example channels and banks in fluvial systems)
  • Energy related to topography, climate, and
    tectonic activity

39
Sediment Sorting
40
Sedimentary Structure Cross Bedding
41
Fluvial and Lacustrine Environments
  • Fluvial
  • Channelization
  • Complex and close interrelationship of fine and
    course sediments
  • Challenge for characterization due to high
    variability
  • Special examples glacial environments
  • Lacustrine
  • Deltaic deposits at margins, finer materials in
    lake beds

42
Deltaic Environments
  • Variability based on proximity to source
  • Stratigraphy effected by progradation

43
Deltaic Development and Sedimentary Facies
44
Continental Slope Environments
  • Turbidites and turbidity currents
  • Graded bedding
  • poor sorting
  • vertical zonation with fining upwards

45
Turbidites and Turbidity Currents
46
Metamorphic Classification
  • Original Material
  • sandstone, limestone, shale, basalt)
  • Metamorphic Grade (Temperature, Pressure)
  • Source of Metamorphism (Regional, Contact)

47
Basic Metamorphic Types
  • Quartz Sandstone ? Quartzite
  • Limestone, Dolomite ? Marble
  • Shale ?
  • Slate cleavage, no visible xls
  • Phyllite foliation, mica sheen but xls not
    visible
  • Schist clear foliation, visible mica
  • Gneiss like granite but with foliation/gneissosi
    ty
  • Basalt ? greenschist, amphibolite

48
Non-foliated Metamorphic Rocks
  • Sandstone gt Quartzite
  • Limestone gt Marble
  • Dolomite gt Dolomitic Marble

49
Foliated Metamorphic Rocks
  • Shale/Mudstone
  • Slate
  • Phyllite (Greek for leaves e.g. phyllo dough)
  • Schist
  • Gneiss

50
Origin of Foliation (gneissosity, schistosity)
51
Engineering Properties
  • Anisotropy of strength and elastic properties
  • Preferred failure on foliation

52
Slate
53
Phyllite
54
Schist
55
Chlorite Schist
56
Gneiss
57
Banded Gneiss
58
Metamorphic Grade
59
Subduction-Zone Metamorphism
60
Metamorphism at Continental Collisions
61
Contact Metamorphism
Write a Comment
User Comments (0)
About PowerShow.com