Classification of Igneous Rocks Figure 2-1a. Method #1 for plotting a point with the components: 70% X, 20% Y, and 10% Z on triangular diagrams. An Introduction to Igneous and Metamorphic Petrology, John Winter, Prentice Hall.

Classification of Igneous Rocks Figure 2-1b. Method #2 for plotting a point with the components: 70% X, 20% Y, and 10% Z on triangular diagrams. An Introduction to Igneous and Metamorphic Petrology, John Winter, Prentice Hall.

Classification of Igneous Rocks Q The rock must contain a total of at least 10% of the minerals below. Quartzolite Renormalize to 100% 90 90 Quartz-rich Granitoid 60 60 Granite Grano- Tonalite Alkali Feldspar Granite diorite Alkali Fs. 20 20 Qtz. Diorite/ Quartz Syenite Quartz Quartz Quartz Qtz. Gabbro Alkali Fs. Syenite Monzonite Monzodiorite Syenite 5 5 Diorite/Gabbro/ Syenite Monzonite Monzodiorite A 10 35 65 90 Anorthosite (Foid)-bearing (Foid)-bearing (Foid)-bearing P Syenite Monzonite Monzodiorite (Foid)-bearing 10 10 Diorite/Gabbro (Foid)-bearing Alkali Fs. Syenite (Foid) Syenite (Foid) (Foid) Monzosyenite Monzodiorite (Foid) Gabbro Figure 2-2. A classification of the phaneritic igneous rocks. a. Phaneritic rocks with more than 10% (quartz + feldspar + feldspathoids). After IUGS. 60 60 (Foid)olites F

Classification of Igneous Rocks Figure 2-2. A classification of the phaneritic igneous rocks. b. Gabbroic rocks. c. Ultramafic rocks. After IUGS. Olivine Clinopyroxene Orthopyroxene Lherzolite Harzburgite Wehrlite Websterite Orthopyroxenite Clinopyroxenite Olivine Websterite Peridotites Pyroxenites 90 40 10 Dunite (c)

Classification of Igneous Rocks Figure 2-3. A classification and nomenclature of volcanic rocks. After IUGS.

Classification of Igneous Rocks Figure 2-4. A chemical classification of volcanics based on total alkalis vs. silica. After Le Bas et al. (1986) J. Petrol., 27, 745-750. Oxford University Press.

Classification of Igneous Rocks Figure 2-5. Classification of the pyroclastic rocks. a. Based on type of material. After Pettijohn (1975) Sedimentary Rocks, Harper & Row, and Schmid (1981) Geology, 9, 40-43. b. Based on the size of the material. After Fisher (1966) Earth Sci. Rev., 1, 287-298.