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CEE 437 Rocks! Thomas Doe. Outline Igneous Rocks Igneous Rocks Sedimentary Rocks Sedimentary Rocks Metamorphic Rocks Metamorphic Rocks Rock Identification.

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Presentation on theme: "CEE 437 Rocks! Thomas Doe. Outline Igneous Rocks Igneous Rocks Sedimentary Rocks Sedimentary Rocks Metamorphic Rocks Metamorphic Rocks Rock Identification."— Presentation transcript:

1 CEE 437 Rocks! Thomas Doe

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

3 Rock 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

4 Northwest Igneous and Metamorphic 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)

5 Geologic Settings for Igneous Rocks Oceanic Oceanic Hi Fe, Mg, Ca, low Si Hi Fe, Mg, Ca, low Si basalt, gabbro basalt, gabbro Continental Continental Hi Si, Na, K Hi Si, Na, K granite, rhyolite, andesite granite, rhyolite, andesite

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

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

8 Igneous Rock Classification SERPENTINITE Acidic, FelsicBasic, MaficUltramafic

9

10 Magma Generation on Continental Margins

11 Magma Generation in Convergent Continental Plate Margins

12 Extrusives Viscosity varies with Si and water content Viscosity varies with Si and water content Basalt — low viscosity Basalt — low viscosity Rhyolite — high viscosity Rhyolite — high viscosity Rhyolite flows relatively unusual as rhyolite does not flow well Rhyolite flows relatively unusual as rhyolite does not flow well Explosive Explosive Tuffs, pyroclastics Tuffs, pyroclastics

13 Volcano Types Basaltic: low viscosity — Hawaii, Columbia Plateau Andesitic/Rhyolitic

14 Structures of Basalt Flows Lava Tubes Lava Tubes Flow Stratigraphy Flow Stratigraphy collonade collonade entablature entablature flow top breccia/scoria 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. Helen’s Blast Zone

21 Mt. Mazama Ash Distribution

22 Sedimentary Rocks Clastics, Siliciclastics, and Evaporites Clastics, Siliciclastics, and Evaporites Clastic rocks, depositional medium, and energy Clastic rocks, depositional medium, and energy Diagenesis — chemical changes after deposition Diagenesis — chemical changes after deposition

23 Rock 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

24 Sediment Sources

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

26 Clastic Sedimentary Rocks Clay, muds  shales, mudstones, claystones (difference based on fissility) Clay, muds  shales, mudstones, claystones (difference based on fissility) Silts  siltstones Silts  siltstones Sands  sandstones Sands  sandstones Gravels  Conglomerates (Breccia if angular, breccia may also be a term for tectonically fragmented rock) 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, Al 2 (OH) 6, or brucite Mg 3 (OH) 6 Sheets of linked silica tetrahedra sandwiching octahedral layers of gibbsite composition, Al 2 (OH) 6, or brucite Mg 3 (OH) 6 Major Clay Groups Major Clay Groups kaolinite: single gibbsite layer kaolinite: single gibbsite layer montmorillonite:weak water bonding between layers, moderated by Ca, Na, or K (near-shore environments) montmorillonite:weak water bonding between layers, moderated by Ca, Na, or K (near-shore environments) illite: K bonds between layers (off-shore environments) illite: K bonds between layers (off-shore environments) bentonite: highly expansive, volcanic-derived, Na-rich montmorillonite bentonite: highly expansive, volcanic-derived, Na-rich montmorillonite

30 Clay Structure

31 Clay Structure Cont’d. Kaolinite Illite Montmorillonite

32 Lithification Cementation Cementation deposition of a material different from clasts deposition of a material different from clasts Crystallization Crystallization crystal growth on clasts to fill pore space crystal growth on clasts to fill pore space Compaction Compaction Diagenesis Diagenesis Early post-depositional chemical transformation of sediments, e.g. calcite to dolomite Early post-depositional chemical transformation of sediments, e.g. calcite to dolomite

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

34 Carbonate Environments

35 Evaporites Rock salt (NaCl), Gypsum-Anhydrite (CaSO 4 ), Sylvite (KCl) Rock salt (NaCl), Gypsum-Anhydrite (CaSO 4 ), Sylvite (KCl) Deposition in regions where evaporation exceeds recharge Deposition in regions where evaporation exceeds recharge desert lakes desert lakes restricted seas (Mediterranean) restricted seas (Mediterranean) lagoons, back-reef areas lagoons, back-reef areas Subject to flow and diapirism Subject to flow and diapirism

36 Other Sedimentary Rocks Chert: finely crystalline silica Chert: finely crystalline silica as replacement/diagenetic nodules as replacement/diagenetic nodules as bedded material from silica-shelled biota as bedded material from silica-shelled biota Coal Coal Derived from vegetation Derived from vegetation Banded Iron Formation Banded Iron Formation Likely bacteria derived, mainly Pre-Cambrian 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 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 Properties can be strong anisotropic and heterogeneous based on bedding

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

39 Sediment Sorting

40 Sedimentary Structure — Cross Bedding

41 Fluvial and Lacustrine Environments Fluvial Fluvial Channelization Channelization Complex and close interrelationship of fine and course sediments Complex and close interrelationship of fine and course sediments Challenge for characterization due to high variability Challenge for characterization due to high variability Special examples: glacial environments Special examples: glacial environments Lacustrine Lacustrine Deltaic deposits at margins, finer materials in lake beds Deltaic deposits at margins, finer materials in lake beds

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

43 Deltaic Development and Sedimentary Facies

44 Continental Slope Environments Turbidites and turbidity currents Turbidites and turbidity currents Graded bedding Graded bedding poor sorting poor sorting vertical zonation with fining upwards vertical zonation with fining upwards

45 Turbidites and Turbidity Currents

46 Metamorphic Classification Original Material Original Material sandstone, limestone, shale, basalt) sandstone, limestone, shale, basalt) Metamorphic Grade (Temperature, Pressure) Metamorphic Grade (Temperature, Pressure) Source of Metamorphism (Regional, Contact) Source of Metamorphism (Regional, Contact)

47 Basic Metamorphic Types Quartz Sandstone  Quartzite Quartz Sandstone  Quartzite Limestone, Dolomite  Marble Limestone, Dolomite  Marble Shale  Shale  Slate — cleavage, no visible xl’s Slate — cleavage, no visible xl’s Phyllite — foliation, mica sheen but xl’s not visible Phyllite — foliation, mica sheen but xl’s not visible Schist — clear foliation, visible mica Schist — clear foliation, visible mica Gneiss — like granite but with foliation/gneissosity Gneiss — like granite but with foliation/gneissosity Basalt  greenschist, amphibolite Basalt  greenschist, amphibolite

48 Non-foliated Metamorphic Rocks Sandstone —> Quartzite Sandstone —> Quartzite Limestone —> Marble Limestone —> Marble Dolomite —> Dolomitic Marble Dolomite —> Dolomitic Marble

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

50 Origin of Foliation (gneissosity, schistosity)

51 Engineering Properties Anisotropy of strength and elastic properties Anisotropy of strength and elastic properties Preferred failure on foliation 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


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