1. CEE 437 Lecture 4 Igneous 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 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)

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

8. Igneous Rock Classification SERPENTINITE Acidic, FelsicBasic, MaficUltramafic 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 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)

35. Sauk River Quadrangle

36. Malpasset Dam