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CEE 437 Lecture 4 Igneous and Metamorphic Rocks, Rock Lab

CEE 437 Lecture 4 Igneous and Metamorphic Rocks, Rock Lab. October 10, 2002 Thomas Doe. Outline. Igneous Rocks Metamorphic Rocks Rock Identification Lab. Northwest Igneous and Metamorphic Rocks. Cascade Volcanoes (recent). Cascade Batholiths (Felsic, Cret-Miocene).

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CEE 437 Lecture 4 Igneous and Metamorphic Rocks, Rock Lab

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  1. CEE 437 Lecture 4Igneous and Metamorphic Rocks, Rock Lab October 10, 2002 Thomas Doe

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

  3. 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)

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

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

  6. 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

  7. Igneous Rock Identification Igneous Rock Identification

  8. Igneous Rock Classification Acidic, Felsic Basic, Mafic Ultramafic SERPENTINITE Common Types in RED outline

  9. Igneous Structural Features

  10. Magma Generation on Continental Margins

  11. Magma Generation in Convergent Continental Plate Margins

  12. Igneous Structures

  13. 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

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

  15. Structures of Basalt Flows • Lava Tubes • Flow Stratigraphy • collonade • entablature • flow top breccia/scoria

  16. Hawaii Basalt Flows

  17. Basalt Flow Structures

  18. Eruptions of Acid-Rock Volcanoes

  19. Rhyolite Dome

  20. Caldera

  21. Mt. St. Helen’s Blast Zone

  22. Mt. Mazama Ash Distribution

  23. Subduction-Zone Metamorphism

  24. Metamorphism • Recrystallization of Rock Under Temperature and Pressure

  25. Metamorphic Rock Classification

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

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

  28. Origin of Foliation (gneissosity, schistosity)

  29. Metamorphism at Continental Collisions

  30. Contact Metamorphism

  31. Metmorphic Grade

  32. 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)

  33. Sauk River Quadrangle

  34. Malpasset Dam

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