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CEE 437 Rocks!. Thomas Doe. Silica Tetrahedron. Feldspar Structure. All tetrahedra corners occupied Both Si and Al tetrahedra Cations in voids of structure to balance charge. Feldspar Compositions. Clay Minerals. Extremely Important Mineral Group Seals Stability Pore pressure - PowerPoint PPT Presentation
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CEE 437 CEE 437 Rocks!Rocks!
Thomas DoeThomas Doe
Silica TetrahedronSilica Tetrahedron
Feldspar StructureFeldspar Structure
All tetrahedra All tetrahedra corners occupiedcorners occupied
Both Si and Al Both Si and Al tetrahedratetrahedra
Cations in voids of Cations in voids of structure to structure to balance chargebalance charge
(a)
(b)
diad axis
T1T1 T1
T1T1 T1
T2 T2 T2
T2T2T2
b
Feldspar CompositionsFeldspar Compositions
aa
KAlSi3O8
NaAlSi3O8 albite
CaAl2Si2O8 anorthite
Plagioclase feldspars
sanidineorthoclasemicrocline
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, Kaolinite Illite, Kaolinite 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)
Clay Viewed from Clay Viewed from Electron MicroscopeElectron Microscope
Northwest Igneous and Northwest Igneous and Metamorphic RocksMetamorphic Rocks
Columbia River Basalts
(miocene)
Snake River Basalts
(pliocene)
Yellowstone Region Acidic Volcanics (Pleistocene to
recent)
Cascade Volcanoes (recent)
Recent Basaltic Volcanism (Newberry Crater)
Cascade Batholiths (Felsic, Cret-Miocene)
Geologic Settings for Geologic Settings for Igneous RocksIgneous Rocks
OceanicOceanic Hi Fe, Mg, Ca, low SiHi Fe, Mg, Ca, low Si basalt, gabbrobasalt, gabbro
Continental Continental Hi Si, Na, KHi Si, Na, K granite, rhyolite, andesitegranite, rhyolite, andesite
Igneous OriginsIgneous Origins
IntrusiveIntrusive Batholithic or plutonic: phaneriticBatholithic or plutonic: phaneritic Dikes or sills that chill rapidly: aphaniticDikes or sills that chill rapidly: aphanitic
ExtrusiveExtrusive deposition as melt (lava)deposition as melt (lava) pyroclasticpyroclastic
tufftuff tephratephra pyroclastic flowspyroclastic flows
Identifying Igneous Identifying Igneous RocksRocks
ChemistryChemistry Acidic: Basic (more Si, less Si)Acidic: Basic (more Si, less Si)
TextureTexture Aphanitic: crystals not visibleAphanitic: crystals not visible Phaneritic: made of visible crystal Phaneritic: made of visible crystal
componentscomponents Porphyritic: Larger crustals in aphanitic Porphyritic: Larger crustals in aphanitic
or phaneritic ground massor phaneritic ground mass
Igneous Rock Igneous Rock ClassificationClassification
SERPENTINITE
Acidic, Felsic Basic, Mafic Ultramafic
Magma Generation on Magma Generation on Continental MarginsContinental Margins
Magma Generation in Magma Generation in Convergent Continental Convergent Continental
Plate MarginsPlate Margins
ExtrusivesExtrusives
Viscosity varies with Si and water Viscosity varies with Si and water contentcontent Basalt — low viscosityBasalt — low viscosity Rhyolite — high viscosityRhyolite — high viscosity
Rhyolite flows relatively unusual as Rhyolite flows relatively unusual as rhyolite does not flow wellrhyolite does not flow well ExplosiveExplosive Tuffs, pyroclasticsTuffs, pyroclastics
Volcano TypesVolcano Types
Basaltic: low viscosity — Hawaii, Columbia Plateau
Andesitic/Rhyolitic
Structures of Basalt Structures of Basalt FlowsFlows
Lava TubesLava Tubes Flow StratigraphyFlow Stratigraphy
collonadecollonade entablatureentablature flow top breccia/scoriaflow top breccia/scoria
Hawaii Basalt FlowsHawaii Basalt Flows
Basalt Flow StructuresBasalt Flow Structures
Eruptions of Acid-Rock Eruptions of Acid-Rock VolcanoesVolcanoes
Rhyolite DomeRhyolite Dome
CalderaCaldera
Mt. St. Helen’s Blast Mt. St. Helen’s Blast ZoneZone
Mt. Mazama Ash Mt. Mazama Ash DistributionDistribution
Basic Metamorphic Basic Metamorphic TypesTypes
Quartz Sandstone Quartz Sandstone Quartzite Quartzite Limestone, Dolomite Limestone, Dolomite Marble Marble Shale Shale
Slate — cleavage, no visible xl’sSlate — cleavage, no visible xl’s Phyllite — foliation, mica sheen but xl’s not Phyllite — foliation, mica sheen but xl’s not
visiblevisible Schist — clear foliation, visible micaSchist — clear foliation, visible mica Gneiss — like granite but with Gneiss — like granite but with
foliation/gneissosityfoliation/gneissosity Basalt Basalt greenschist, amphibolite greenschist, amphibolite
Non-foliated Non-foliated Metamorphic RocksMetamorphic Rocks
Sandstone —> QuartziteSandstone —> Quartzite Limestone —> MarbleLimestone —> Marble Dolomite —> Dolomitic MarbleDolomite —> Dolomitic Marble
Foliated Metamorphic Foliated Metamorphic RocksRocks
Shale/MudstoneShale/Mudstone SlateSlate Phyllite (Greek for leaves e.g. phyllo Phyllite (Greek for leaves e.g. phyllo
dough)dough) SchistSchist GneissGneiss
Origin of Foliation Origin of Foliation (gneissosity, schistosity)(gneissosity, schistosity)
Engineering PropertiesEngineering Properties
Anisotropy of strength and elastic Anisotropy of strength and elastic propertiesproperties
Preferred failure on foliationPreferred failure on foliation
SlateSlate
PhyllitePhyllite
SchistSchist
Chlorite SchistChlorite Schist
GneissGneiss
Banded GneissBanded Gneiss
Metamorphic GradeMetamorphic Grade
Subduction-Zone Subduction-Zone MetamorphismMetamorphism
Metamorphism at Metamorphism at Continental CollisionsContinental Collisions
Contact MetamorphismContact Metamorphism
Sedimentary RocksSedimentary Rocks
Clastics, Siliciclastics, and Clastics, Siliciclastics, and EvaporitesEvaporites
Clastic rocks, depositional medium, Clastic rocks, depositional medium, and energyand energy
Diagenesis — chemical changes Diagenesis — chemical changes after depositionafter deposition
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
Sediment SourcesSediment Sources
Clastic Sedimentary Clastic Sedimentary RocksRocks
Clastic — broken like iconoclast)Clastic — broken like iconoclast) Often referred to as Siliciclastics as Often referred to as Siliciclastics as
having Si based rock forming mineralshaving Si based rock forming minerals Based on grain size and to a lesser Based on grain size and to a lesser
extent compositionextent composition Grain size related to energy of Grain size related to energy of
depositional environmentdepositional environment Relationship of medium velocity to Relationship of medium velocity to
maximum grain size)maximum grain size)
Clastic Sedimentary Clastic Sedimentary RocksRocks
Clay, muds Clay, muds shales, mudstones, shales, mudstones, claystones (difference based on claystones (difference based on fissility)fissility)
Silts Silts siltstones siltstones Sands Sands sandstones sandstones Gravels Gravels Conglomerates (Breccia if Conglomerates (Breccia if
angular, breccia may also be a term angular, breccia may also be a term for tectonically fragmented rock) for tectonically fragmented rock)
Weathering CycleWeathering Cycle
Clastic SedimentsClastic Sediments
Clay MineralsClay Minerals
Sheets of linked silica tetrahedra sandwiching Sheets of linked silica tetrahedra sandwiching octahedral layers of gibbsite composition, octahedral layers of gibbsite composition, AlAl22(OH)(OH)66, or brucite Mg, or brucite Mg33(OH)(OH)66
Major Clay GroupsMajor Clay Groups kaolinite: single gibbsite layerkaolinite: single gibbsite layer montmorillonite:weak water bonding between montmorillonite:weak water bonding between
layers, moderated by Ca, Na, or K (near-shore layers, moderated by Ca, Na, or K (near-shore environments)environments)
illite: K bonds between layers (off-shore illite: K bonds between layers (off-shore environments)environments)
bentonite: highly expansive, volcanic-derived, Na-bentonite: highly expansive, volcanic-derived, Na-rich montmorilloniterich montmorillonite
Clay StructureClay Structure
Clay Structure Cont’d.Clay Structure Cont’d.
Kaolinite
Illite
Montmorillonite
LithificationLithification
CementationCementation deposition of a material different from clastsdeposition of a material different from clasts
CrystallizationCrystallization crystal growth on clasts to fill pore spacecrystal growth on clasts to fill pore space
CompactionCompaction DiagenesisDiagenesis
Early post-depositional chemical Early post-depositional chemical transformation of sediments, e.g. calcite to transformation of sediments, e.g. calcite to dolomitedolomite
CarbonatesCarbonates
Generally like siliciclastics — Generally like siliciclastics — carbonate muds, sands, etc.carbonate muds, sands, etc.
Often deposited in reefsOften deposited in reefs Major portion of world oil depositsMajor portion of world oil deposits Properties depend strongly on post-Properties depend strongly on post-
depositional pore chemistrydepositional pore chemistry CementationCementation DissolutionDissolution
Karst topography, cave formationKarst topography, cave formation
Carbonate EnvironmentsCarbonate Environments
EvaporitesEvaporites
Rock salt (NaCl), Gypsum-Anhydrite Rock salt (NaCl), Gypsum-Anhydrite (CaSO(CaSO44), Sylvite (KCl)), Sylvite (KCl)
Deposition in regions where Deposition in regions where evaporation exceeds rechargeevaporation exceeds recharge desert lakesdesert lakes restricted seas (Mediterranean)restricted seas (Mediterranean) lagoons, back-reef areaslagoons, back-reef areas
Subject to flow and diapirismSubject to flow and diapirism
Other Sedimentary RocksOther Sedimentary Rocks
Chert: finely crystalline silicaChert: finely crystalline silica as replacement/diagenetic nodulesas replacement/diagenetic nodules as bedded material from silica-shelled as bedded material from silica-shelled
biotabiota CoalCoal
Derived from vegetationDerived from vegetation Banded Iron FormationBanded Iron Formation
Likely bacteria derived, mainly Pre-Likely bacteria derived, mainly Pre-CambrianCambrian
Sedimentary Rocks and Sedimentary Rocks and Rock PropertiesRock Properties
Properties for a given geologic Properties for a given geologic description vary wildly based on description vary wildly based on cementation, porosity and other cementation, porosity and other diagenetic factors.diagenetic factors.
Properties can be strongly Properties can be strongly anisotropic and heterogeneous anisotropic and heterogeneous based on beddingbased on bedding
Depositional Depositional EnvironmentsEnvironments
Synchroneity of deposition of different Synchroneity of deposition of different rock typesrock types
Sedimentary faciesSedimentary facies A rock unit is not everywhere the same age: A rock unit is not everywhere the same age:
Bright Angel ShaleBright Angel Shale Related to energy of environmentRelated to energy of environment
(example channels and banks in fluvial (example channels and banks in fluvial systems)systems)
Energy related to topography, climate, Energy related to topography, climate, and tectonic activityand tectonic activity
Sediment SortingSediment Sorting
Sedimentary Structure — Sedimentary Structure — Cross BeddingCross Bedding
Fluvial and Lacustrine Fluvial and Lacustrine EnvironmentsEnvironments
FluvialFluvial ChannelizationChannelization Complex and close interrelationship of fine Complex and close interrelationship of fine
and course sedimentsand course sediments Challenge for characterization due to high Challenge for characterization due to high
variabilityvariability Special examples: glacial environmentsSpecial examples: glacial environments
LacustrineLacustrine Deltaic deposits at margins, finer materials in Deltaic deposits at margins, finer materials in
lake bedslake beds
Deltaic EnvironmentsDeltaic Environments
Variability based on proximity to Variability based on proximity to sourcesource
Stratigraphy effected by Stratigraphy effected by progradationprogradation
Deltaic Development and Deltaic Development and Sedimentary FaciesSedimentary Facies
Continental Slope Continental Slope EnvironmentsEnvironments
Turbidites and turbidity currentsTurbidites and turbidity currents Graded beddingGraded bedding
poor sortingpoor sorting vertical zonation with fining upwardsvertical zonation with fining upwards
Turbidites and Turbidity Turbidites and Turbidity CurrentsCurrents
Metamorphic Metamorphic ClassificationClassification
Original MaterialOriginal Material sandstone, limestone, shale, basalt)sandstone, limestone, shale, basalt)
Metamorphic Grade (Temperature, Metamorphic Grade (Temperature, Pressure)Pressure)
Source of Metamorphism (Regional, Source of Metamorphism (Regional, Contact)Contact)
K. Troost
Glacial EnvironmentsGlacial Environments