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Lecture 4 Igneous Rocks, Intrusive Activity and the Origin of Igneous Rocks Physical Geology I II III A) B) Rock Types Definitions Igneous Rocks Extrusive v Intrusive Textures i. ii. iii. Intrusive Textures Extrusive Textures Porphyritic Texture C) Composition A) Chemistry IV B) C) V Lecture Outline Magma i. ii. iii. iv. Felsic Intermediate Mafic Ultramafic i. ii. Bowen's Reaction Series Fractionation Formation of Magma Magmatic Variability Plate Tectonics and Igneous Rocks A) B) C) VI Divergent Boundary Convergent Boundary Hot Spot Intrusive Bodies Physical Geology Rock Types What is the basis for this classification? Physical Geology Definitions magma molten rock that is produced from pre-existing rock in the asthenosphere by Earth's internal heat. The magma then rises into the lithosphere and cools on the surface or in the subsurface. lava - magma flowing on the surface of the Earth igneous - formed from fire plutonic - formed at depth Physical Geology Igneous Rocks Physical Geology Igneous Rocks Intrusive Rocks Extrusive Rocks Physical Geology Igneous Rocks Intrusive Textures Pegmatitic Phaneritic Physical Geology Igneous Rocks Extrusive Textures Aphanitic Glassy Fragmental Vesicular Physical Geology Igneous Rocks Porphyritic Texture Physical Geology Igneous Rocks Composition Major Elements Minor (Trace) Elements Oxide SiO2 Al2O3 TiO2 Fe2O3 FeO MnO MgO CaO Na2O K2O H2O+,P2O5 CO2 Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn Ga,Rb, Sr, Y, Zr, Nb, Ba, Pb, F, Cl, S % by Weight 35.0-80.0 8.0-22.0 } 4.030.0 1.5-8.0 0.5-8.0 varies <0.15 varies Rare Earth Elements Physical Geology Magma Physical Geology Felsic Magma silica content temperature viscosity Na, K, Al content Ca, Fe, Mg content eruption minerals - high, >65% < 9000C high high very low explosive (Mount St. Helens) Na-rich plagioclase feldspar potassium feldspar quartz Physical Geology Intermediate Magma silica content temperature viscosity Na, K, Al content Ca, Fe, Mg content eruption minerals - intermediate, 53 - 65% 900 - 11000C intermediate intermediate intermediate intermediate (Andes Mtns.) plagioclase feldspar amphibole Physical Geology Mafic Magma silica content temperature viscosity Na, K, Al content Ca, Fe, Mg content eruption minerals - low, 45 - 52% 1100 - 13000C low (fluid) low high quiet (Kilauea) Ca-rich plagioclase feldspar pyroxene olivine Physical Geology Ultramafic Magma silica content temperature viscosity Na, K, Al content Ca, Fe, Mg content eruption minerals - very low, <45% ~14000C very low (fluid) very low very high none (Cyprus) pyroxene olivine Physical Geology Igneous Rocks Magma Formation Processes Decompression Melting Addition of Impurities Temperature (Geothermal Gradient) Physical Geology Magma Formation The Geothermal Gradient Physical Geology Magma Formation Impurities Physical Geology Magmatic Variability Bowen's Reaction Series Physical Geology Magmatic Variability Fractionation Differentiation/Partial Melting Assimilation Mixing Physical Geology Magmatic Variability Differentiation Physical Geology Magmatic Variability Assimilation Physical Geology Magmatic Variability Magma Mixing Physical Geology Plate Tectonics and Igneous Rocks Physical Geology Plate Tectonics and Igneous Rocks Divergent Boundary Physical Geology Plate Tectonics and Igneous Rocks Convergent Boundary Physical Geology Plate Tectonics and Igneous Rocks Hot Spots Physical Geology Intrusive Bodies Physical Geology Shallow Intrusive Bodies Ship Rock, NM Volcanic Neck Physical Geology Shallow Intrusive Bodies Sill Dike Physical Geology Deep Intrusive Bodies Batholith Stock Diapir
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