1. 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.

2. 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.

3. Classification of Igneous RocksQ
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

4. 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)

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

6. 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, Oxford University Press.

7. 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, b. Based on the size of the material. After Fisher (1966) Earth Sci. Rev., 1,