CEE 437 Rocks! Thomas Doe Outline Igneous Rocks Sedimentary Rocks Metamorphic Rocks Rock Identification Lab Rock Cycle Crystallization at depth or extrusion at surface Igneous Rocks Sediments Lithification Magma Burial, metamorphism, recrystallization Weathering, Erosion Melting Metamorphic Rocks Burial, metamorphism, recrystallization Sedimentary Rocks Northwest Igneous and Metamorphic Rocks Cascade Volcanoes (recent) Cascade Batholiths (Felsic, CretMiocene) Columbia River Basalts (miocene) Recent Basaltic Volcanism (Newberry Crater) Snake River Basalts (pliocene) Yellowstone Region Acidic Volcanics (Pleistocene to recent) Geologic Settings for Igneous Rocks Oceanic Hi Fe, Mg, Ca, low Si basalt, gabbro Continental Hi Si, Na, K granite, rhyolite, andesite Igneous Origins Intrusive Batholithic or plutonic: phaneritic Dikes or sills that chill rapidly: aphanitic Extrusive deposition as melt (lava) pyroclastic tuff tephra pyroclastic flows 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 Igneous Rock Classification Acidic, Felsic Basic, Mafic Ultramafic SERPENTINITE Magma Generation on Continental Margins 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 Non-foliated Metamorphic Rocks Sandstone —> Quartzite Limestone —> Marble Dolomite —> Dolomitic Marble Foliated Metamorphic Rocks Shale/Mudstone Slate Phyllite (Greek for leaves e.g phyllo dough) Schist Gneiss Origin of Foliation (gneissosity, schistosity) Engineering Properties Anisotropy of strength and elastic properties Preferred failure on foliation Slate Phyllite Schist Chlorite Schist Gneiss Banded Gneiss Metamorphic Grade Subduction-Zone Metamorphism Metamorphism at Continental Collisions Contact Metamorphism