Sum11.208.rocksIg

Sum11.208.rocksIg - Rocks are made of Minerals(Minerals in Granite Rocks The Geologic Dictionary Rock Cycle Deposition Sediment Lithification

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Unformatted text preview: Rocks are made of Minerals (Minerals in Granite) Rocks The Geologic Dictionary Rock Cycle Deposition Sediment Lithification Transport Sedimentary Rocks Erosion Metamorphism Weathering Igneous Rocks Soil, sediment, weathered rock, regolith Crystallization Metamorphic Rocks Melting Magma Rock Identification is based on: • Composition Proportions of Rock Types on the Earth • Texture What minerals make up the rock? What is the shape, size and orientation of the mineral grains that make up the rock? Major Difference: Crystalline vs. Clastic igneous & metamorphic rocks = crystalline rocks Rock Cycle Deposition Sediment Lithification Igneous Rocks Transport Sedimentary Rocks Erosion Metamorphism Weathering Igneous Rocks Crystallization Metamorphic Rocks Melting Magma Identification Igneous Composition Igneous Minerals (p.21) M ineral Mafic Properties O livine Green to yellow-green; vitreous; fractures; small, equidimensional grains Usually white or gray; 2 cleavages at 90°; elongate grains; striations sometimes visible Greenish black or brownish black; rather dull luster; blocky grains Black with shiny, splintery appearance; two cleavages at 60° and 120°; elongate grains Shiny, black sheets; one perfect cleavage Usually white or pink; 2 cleavages at 90°; equidimensional grains Shiny, silvery sheets; one perfect cleavage Colorless to gray; vitreous with conchoidal fracture; irregular grains in intrusive rocks; equidimensional phenocrysts in extrusive rocks Plagioclase Pyroxene Amphibole B iotite Orthoclase Felsic Olivine Muscovite Q uartz Ca Plagioclase Olivine Mafic Rocks Pyroxene Ca Plagioclase Amphibole Pyroxene Amphibole Na Plagioclase Na Plagioclase Biotite Biotite Orthoclase Muscovite Quartz Orthoclase Bowen’s Reaction Series Muscovite Quartz Ca Plagioclase Olivine Ca Plagioclase Olivine Pyroxene Pyroxene Amphibole Na Plagioclase Biotite Intermediate Rocks Amphibole Na Plagioclase Biotite Orthoclase Orthoclase Muscovite Muscovite Quartz Quartz Felsic Rocks Igneous Textures - Crystalline Igneous Textures - Crystalline Porphyritic Coarse Grained Fine Grained Groundmass Phenocrysts Igneous Textures - Crystalline Igneous Textures - Pyroclastic/Fragmental Made of rock fragments rather than crystals Glassy Vesicular Ultramafic Rock - Dunite Igneous Rocks Gabbro Intermediate Diorite Granodiorite Felsic Granite Fine Coarse Mafic Basalt Andesite Dacite Rhyolite Igneous Rocks (p.20) COMPOSITION (Minerals Present) Coarsegrained* Finegrained* M afic Intermediate Intermediate F elsic Olivine (Pyroxene) TEXTURES Ultramafic CaPlagioclase Pyroxene Olivine NaPlagioclase Amphibole Pyroxene Biotite Na-Plagioclase Amphibole Quartz Biotite Q uartz Orthoclase Biotite Na-Plagioclas e D UNITE GABBRO DIORITE GRANODIORITE GRANITE B ASALT ANDESITE DACITE RHYOLITE Glassy Vesicular Igneous Rocks Interpretation OBSIDIAN S CORIA PUMICE Fragmental T UFF (Pyroclastic) *Some igneous rocks have a porphyritic texture. If a rock has 2 grain sizes, the rock is named after the smaller grain size and the word porphyritic is added as an adjective. For example, if a rock is predominantly fine-grained and mafic, it would be a basalt. If phenocrysts are present in the finegrained matrix, this rock would be called a porphyritic basalt. Silicate Magmas Sir James Hall Scottish Geologist Felsic (Rhyolitic) Magma Mafic (Basaltic) Magma Igneous Rock “Translations” Magma Source: Partial Melting Hypothetical Solid Rock: Intermediate Composition • Composition (Mafic v. Felsic) • Magma source • Texture Grain Size, etc. • How quickly and where magma cooled Mineral Melting Temp A (Mafic) 1200°C B (Int) 1000°C C (Felsic) 800°C Temperature = 500°C Magma Source : Partial Melting Mineral Magma Source : Partial Melting Melting Temp Mineral Melting Temp A (Mafic) A (Mafic) 1200°C B (Int) 1000°C B (Int) 1000°C C (Felsic) Intermediate Magma (All Minerals Melt) 1200°C 800°C C (Felsic) 800C Temperature = 1400°C Temperature = 900°C Magma Magma Separates Bottom Line on Partial Melting Felsic Mineral A (Mafic) Melting Temp 1200°C B (Int) More Mafic 1000°C C (Felsic) Remaining Rock: Partial Melting produces a magma that is more felsic than the parent rock 800°C Rock Ultramafic Mafic Intermediate Felsic Magma from Partial Melting Mafic Intermediate Felsic (more) Felsic Magma Temperature = 900°C Composition: Magma Source Mafic Intermediate Felsic Ocean Crust - Mafic Rock Melts to form int./felsic magma Continental Crust - Felsic Rock Mantle - Ultramafic Rock Melts to form mafic magma Ultramafic mantle Source: Partial Melting of ultramafic mantle at Divergent Zones and… Composition: Magma Source Mafic Intermediate Composition: Magma Source Felsic Source: Partial Melting of ultramafic mantle at Divergent Zones and … Hot Spots Mafic Intermediate Felsic Source: Partial Melting of mantle, ocean crust and continent at Subduction Zones Composition: Magma Source Mafic Intermediate Composition: Magma Source Felsic Source: Partial melting felsic continent above Hot Spots & Subduction Zones Mafic Intermediate Felsic Eventually mafic magma from mantle erupts (last phase of continental hotspot) Texture - Grain Size: Plutons and Volcanoes Extrusive (Volcanic) Surface Magma Rises and Cools Fine Grained Magma Chamber Coarse Grained Intrusive (Plutonic) Name this Igneous Feature… Plutonic Structures Xenoliths Igneous Dike Source: William E. Ferguson Why do we find Plutons at the Surface? Other Textures First slow (underground) then fast (volcanic) Porphyritic Glassy Uplift & Erosion Cools Very Fast Volcanic (On land/shallow water) Vesicular Volcanic (On land) Pyroclastic Sierra Nevada Mountains Batholith, California Intermission: Quiz Intermission: Quiz What Can you say about the history of this rock? What Can you say about the history of this rock? Magma produced by partial melting of the mantle that erupted from a volcano at a divergent zone or hot spot. Basalt Magma produced by partial melting of the mantle that cooled underground (plutonic) at a divergent zone or hot spot. Gabbro Intermission: Quiz Intermission: Quiz What Can you say about the history of this rock? What Can you say about the history of this rock? Magma produced by partial melting of the continental crust that cooled underground (plutonic) at a subduction zone or continental hot spot. Granite Magma produced by partial melting of the mantle, ocean crust & continental crust, that erupted from a volcano at a subduction zone. Andesite ...
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This note was uploaded on 01/11/2012 for the course GEO 208 taught by Professor Robviens during the Summer '11 term at Bellevue College.

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