Chapter 2- Classification of Igneous ROcks - Faculty web pages
Chapter 2- Classification of Igneous ROcks - Faculty web pages
Chapter 2- Classification of Igneous ROcks - Faculty web pages
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<strong>Classification</strong> <strong>of</strong> <strong>Igneous</strong> RocksFigure 2-1a. Method #1 for plotting a point with the components: 70% X, 20% Y, and 10% Z ontriangular diagrams. An Introduction to <strong>Igneous</strong> and Metamorphic Petrology, John Winter, Prentice Hall.
<strong>Classification</strong> <strong>of</strong> <strong>Igneous</strong> RocksFigure 2-1b. Method #2 for plotting a point with the components: 70% X, 20% Y, and 10% Z on triangulardiagrams. An Introduction to <strong>Igneous</strong> and Metamorphic Petrology, John Winter, Prentice Hall.
F(a)The rock must contain a total <strong>of</strong>at least 10% <strong>of</strong> the minerals below.Renormalize to 100%90QQuartzolite90Quartz-richGranitoid<strong>Classification</strong> <strong>of</strong><strong>Igneous</strong> RocksAlkali Fs.Quartz SyeniteAlkali Fs.SyeniteA510(Foid)-bearingAlkali Fs. Syenite2060QuartzSyeniteQuartzMonzonite60QuartzMonzodioriteSyenite Monzonite Monzodiorite10 35 65(Foid)-bearingSyenite(Foid) SyeniteAlkali Feldspar GraniteGranite(Foid)Monzosyenite(Foid)-bearingMonzoniteGranodiorite(Foid)MonzodioriteTonalite(Foid)-bearingMonzodiorite(Foid) Gabbro9020Qtz. Diorite/Qtz. Gabbro510Diorite/Gabbro/AnorthositeP(Foid)-bearingDiorite/GabbroFigure 2-2. A classification <strong>of</strong> the phaneritic igneousrocks. a. Phaneritic rocks with more than 10% (quartz +feldspar + feldspathoids). After IUGS.60(Foid)olites60
<strong>Classification</strong> <strong>of</strong> <strong>Igneous</strong> RocksPlagioclase90AnorthositeFigure 2-2. A classification <strong>of</strong> the phaneriticigneous rocks. b. Gabbroic rocks. c. Ultramaficrocks. After IUGS.TroctoliteGabbroOlivinegabbroOlivine90DunitePeridotitesPyroxenePlagioclase-bearing ultramafic rocks(b)Olivine40HarzburgiteLherzoliteWehrliteOrthopyroxenite(c)10OrthopyroxeneOlivine WebsteriteWebsteriteClinopyroxenite10PyroxenitesClinopyroxene
QF<strong>Classification</strong> <strong>of</strong><strong>Igneous</strong> Rocks60 60RhyoliteDacite20 20A10Trachyte Latite Andesite/Basalt(foid)-bearingTrachyte35 65(foid)-bearingLatite(foid)-bearingAndesite/Basalt10PFigure 2-3. A classification and nomenclature<strong>of</strong> volcanic rocks. After IUGS.PhonoliteTephrite60 60(Foid)ites
<strong>Classification</strong> <strong>of</strong> <strong>Igneous</strong> RocksFigure 2-4. A chemical classification <strong>of</strong> volcanics based on total alkalis vs. silica. After Le Bas et al.(1986) J. Petrol., 27, 745-750. Oxford University Press.
<strong>Classification</strong> <strong>of</strong> <strong>Igneous</strong> RocksFigure 2-5. <strong>Classification</strong> <strong>of</strong> the pyroclastic rocks. a. Based on type <strong>of</strong> material. After Pettijohn(1975) Sedimentary Rocks, Harper & Row, and Schmid (1981) Geology, 9, 40-43. b. Based on thesize <strong>of</strong> the material. After Fisher (1966) Earth Sci. Rev., 1, 287-298.
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