Title: CEE 437 Rocks
1CEE 437 Rocks!
2Outline
- Igneous Rocks
- Sedimentary Rocks
- Metamorphic Rocks
- Rock Identification Lab
3Rock 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
4Northwest 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)
5Geologic Settings for Igneous Rocks
- Oceanic
- Hi Fe, Mg, Ca, low Si
- basalt, gabbro
- Continental
- Hi Si, Na, K
- granite, rhyolite, andesite
6Igneous Origins
- Intrusive
- Batholithic or plutonic phaneritic
- Dikes or sills that chill rapidly aphanitic
- Extrusive
- deposition as melt (lava)
- pyroclastic
- tuff
- tephra
- pyroclastic flows
7Identifying 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
8Igneous Rock Classification
Acidic, Felsic
Basic, Mafic
Ultramafic
SERPENTINITE
9(No Transcript)
10Magma Generation on Continental Margins
11Magma Generation in Convergent Continental Plate
Margins
12Extrusives
- 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
13Volcano Types
Basaltic low viscosity Hawaii, Columbia
Plateau
Andesitic/Rhyolitic
14Structures of Basalt Flows
- Lava Tubes
- Flow Stratigraphy
- collonade
- entablature
- flow top breccia/scoria
15Hawaii Basalt Flows
16Basalt Flow Structures
17Eruptions of Acid-Rock Volcanoes
18Rhyolite Dome
19Caldera
20Mt. St. Helens Blast Zone
21Mt. Mazama Ash Distribution
22Sedimentary Rocks
- Clastics, Siliciclastics, and Evaporites
- Clastic rocks, depositional medium, and energy
- Diagenesis chemical changes after deposition
23Rock 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
24Sediment Sources
25Clastic 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)
26Clastic 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)
27Weathering Cycle
28Clastic Sediments
29Clay 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
30Clay Structure
31Clay Structure Contd.
Kaolinite
Montmorillonite
Illite
32Lithification
- 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
33Carbonates
- 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
34Carbonate Environments
35Evaporites
- 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
36Other 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
37Sedimentary 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
38Depositional 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
39Sediment Sorting
40Sedimentary Structure Cross Bedding
41Fluvial 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
42Deltaic Environments
- Variability based on proximity to source
- Stratigraphy effected by progradation
43Deltaic Development and Sedimentary Facies
44Continental Slope Environments
- Turbidites and turbidity currents
- Graded bedding
- poor sorting
- vertical zonation with fining upwards
45Turbidites and Turbidity Currents
46Metamorphic Classification
- Original Material
- sandstone, limestone, shale, basalt)
- Metamorphic Grade (Temperature, Pressure)
- Source of Metamorphism (Regional, Contact)
47Basic 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
48Non-foliated Metamorphic Rocks
- Sandstone gt Quartzite
- Limestone gt Marble
- Dolomite gt Dolomitic Marble
49Foliated Metamorphic Rocks
- Shale/Mudstone
- Slate
- Phyllite (Greek for leaves e.g. phyllo dough)
- Schist
- Gneiss
50Origin of Foliation (gneissosity, schistosity)
51Engineering Properties
- Anisotropy of strength and elastic properties
- Preferred failure on foliation
52Slate
53Phyllite
54Schist
55Chlorite Schist
56Gneiss
57Banded Gneiss
58Metamorphic Grade
59Subduction-Zone Metamorphism
60Metamorphism at Continental Collisions
61Contact Metamorphism