Plutonic rocks classification

Plutonic rock classification by petrologic means is a simple procedure involving the use of Streckeisen ternary diagrams. Unfortunately, classification suffers from modal estimation errors involving visual estimates, or representativity issues from point counts or image analysis procedures applied to thin sections or slabs of insufficient size. 

Basalt classification using the Ne-Di-Ot-Hy-Q diagram Granite classification using the Ab-An-Or diagram Volcanic and plutonic rock classification using Q (F )- ANOR... 

Figure 3,3 The chemcial classification and nomenclature of pluomic rodts using the total alkalis versus silica (TAS) diagram of Cox et ai (1979) adapted by Wilson (1989) for plutonic rocks. The curved solid line subdivides the alkalic from subalkaiic ro<. -...

Fi re 3.9 The classification of plutonic rocks using their molecular normative compositions (after Streckeisen and Le Maitre, 1979). The numbered fields correspond to those in the modal QAPF diagram of Streckeisen (1976). The named rock types are plotted at the position of their highest concentradon in the data file used by Streckeisen and Le Maitre. 

The diagram for plutonic rocks is given in Figure 3.10 and an example of the calculation of R1 and R2 is given in Table 3.2. The advantages of this classification scheme are that ... 

Figure 3JO The classification of plutonic rocks using the parameters R1 and R2 (after dc la Roche...

De la Roche H., Leterrier J., Grande Claude P. and Marchal M., 1980, A classification of volcanic and plutonic rocks using R1-R2 diagrams and major element analyses — its relationships and current nomenclature, CAew. Geol., 29, 183-210. 

Strecbeisen A., 1976, To each plutonic rock its proper name. Earth. Sci. Rev., 12, 1-33. Streckeisen A. and Le Maitre R.W., 1979, A chemical approximation to the modal Q F classification of igneous rocks. Neues Yahrb. MineruL Abh., 136, 169-206. 

Streckeisen, A.L. Classification and Nomenclature of Plutonic Rocks. Recommendations of the lUGS Subcommission on the Systematics of Igneous Rocks. Geologische Rundschau. Internationale Zemchrift far Geologie, 63 (2) (1974) 773-785. 

Figure 13.5. Classification of Ultramafic Rocks [after Streckeisen, A.L. - Classification and Nomenclature of Plutonic Rocks. Recommendations of the lUGS Subcommission on the Systematics of Igneous Rocks. - Ge-ologische Rundschau. Internationale Zeitschrift fur Geologie, 63 (2) 773-785. Copyright 1974 Springer-Verlag and reproduced with kind permission of Springer Science and Business Media.] Ol + Opx + Cpx + Hbl (+ Bi + Gar + Sp) > 95 Opaque minerals < 5 a. ultramafic rocks composed of olivine, orthopyroxene, and clinopyroxene b. ultramafic rocks that contain horneblende.

Microlithofacial classification of the sandstones is based on Dott s classification modified by Pettijohn et al. (1972). They are mostly arenites and subarkose and quartz wackes (rare sublithic, sporadically lithic and arkosic). Quartz is the main component of the sandstones (about 60-70 vol. percent). Feldspars (6 vol. percent) are mostly represented by potassium feldspars with plagioclases in lesser amounts. Some micas (muscovite and biotite) and chlorites are observed. Mica content of arenites reaches 3 vol. %, but is higher in the wackes. Heavy minerals present include zircon, sphene, rutile and apatite. Magmatic rocks (volcanic more than Plutonic) are predominant among lithoclasts (about 2 vol. %), but some metamorphic and sedimentary clasts being present too. 

Fig. 3.21 The classification of plutonic igneous rocks by Streckeisen (1967, 1976) is based on the modal abundances of quartz (Q), alkali feldspar (including albite, An < 5%) (A), and plagioclase (An >5%) (P). The fields have been numbered in order to identify the rock types that correspond to them 1. quartz, 2. alkali granite, 3. granite, 4. granodiorite, 5a. quartz diorite (trondhjemite), 5b. quartz diorite (tonalite), 6. alkali syenite, 7a. quartz syenite, 7b. syenite, 8a. quartz monzonite (adamellite), 8b. monzonite, 9a. monzodiorite, 9b. monzogabbro, 10. diorite/gabbro (Adapted from Streckeisen 1967)...

Fig. 5.17 The plutons of Hope Granite that intruded the metasedimentary basement rocks of the Shackleton-Glacier area are collectively referred to as the Queen Maud batholith. The modal concentrations of Quartz (Q), alkali feldspar (A), and plagioclase (P) are used to classify a representative collection of the Hope Granite from this area (see also Fig. 3.21, Appendix 3.6.1). The distribution of data points indicates that the Hope Granite consists of granite (field 3), granodiorite (field 4), and quartz diorite (field 5) (Data by Wade and Cathey (1986) and classification of plutonic igneous rocks by Streckeisen (1967))...

Mathews G. W. A classification of uranium deposits in and related to plutonic igneous rock. Reference 15, 15-21. 

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