Classification of igneous rocks

Classification of Igneous Rocks Using Lithogeochemistry Data, Essential Rock Mineralogy, and Projective Geometry in a Streckeisen Ternary Diagram Approach... 

Le Maitre RW (ed) (1989) A Classification of igneous rocks and glossary of terms. Blackwell, Oxford, 193 pp... 

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. 

TaM 13.19. Simplified classification of igneous rocks (wt.% silica in parenthesis)... 

From Le Maitre, R.W. Bateman, P. Dudek, A. and Keller, J. A Classification of Igneous Rocks and Glossary of Terms Blackwell Scientific Publications, Oxford (1989). 

The Lux-Flood theory relates to oxide melts. Geologists have often used acid-base concepts for the empirical classification of igneous silicate rocks (Read, 1948). Silica is implicitly assumed to be responsible for acidity, and the silica content of a rock is used as a measure of its acid-base balance ... 

Feldspars are the most abundant minerals of igneous rocks, where their ubiquity and abundance of their components influence normative classifications. They are also abundant in gneisses, and may be observed in several facies of thermal and regional metamorphic regimes. Notwithstanding their alterability, they are ubiquitously present in sedimentary rocks, as authigenic and/or detritic phases. Only in carbonaceous sediments is their presence subordinate. 

Streckeisen, A., Zanettin, B.A., Le Bas, M.J., Bonin, B., Bateman, P., Bellieni, G., Dudek, A., Efremova, S., Keller, J., Lameyre, J., Sabine, P.A., Schmid, R., Sorensen, H., Woolley, A.R. 2002. Igneous rocks a classification and glossary of terms recommendations of the International union of Geological Science Subcommission on the Systematics of Igneous Rocks. Cambridge University Press, Cambridge, U.K., 800 p. 

Streckeisen AL (1967) Classification and nomenclature of igneous rocks. Neues Jahrbuch Miner. Abhandlungen 107(2/3) 144-240... 

CIPW from Cross, W. Iddings, J.P. Pirsson, L.V. and Washington, H.S. A Quantitative Chemico-Minera-logical Classification and Nomenclature of Igneous Rocks /. Geology 10 (1912) 555-690. 

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.

Geologically and genetically, clay minerals are difficult to define simply and adequately, but broadly they are layer lattice silicates of secondary origin. In the same classification are the micas, talc, chlorites, and serpentines which are not strictly clay minerals. In this context, secondary origin means that mineral formation has arisen from the weathering of primary or igneous rock, e.g. granites and basalts. 

In an exploration area in northern Peru, igneous rocks cover an area of several square km within a metamorphosed series of quartzites and limestones. The younger sequence consists of ignimbrites, tuffs and tuffites of approximately 1000 m thickness. The metamorphism produced skams, which are connected with the ore body. A porphyry Cu deposit occurs in the metamorphosed rocks and is characterised by intense hydrothermal alteration (quartz-kaolinite-sericite) which makes determination and classification of magmatic and sedimentary rocks at the surface very difficult. A zone of propylitic alteration can locally be followed up to 500 m into the andesitic-dioritic wall rocks. 

This chapter will examine the ways in which major element data axe used in geochemistry. The discussion will be restricted to the ten elements traditionally listed as oxides in a major element chemical analysis — Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K and P. Geochemists make use of major element data in three principal ways — in rock classification, in the construction of variation diagrams and as a means of comparison with experimentally determined rock compositions, whose conditions of formation are known. Each of these uses will be discussed in a separate section of this chapter. In addition, major elements are used, often together with trace elements, in the identification of the original tectonic setting of igneous and some sedimentary rocks. This topic will be discussed in Chapter 5. 

Arenite/wacke Unlike many igneous rocks it is difficult to find a simple relationship between the mineralogy of sandstones and their chemical composition. For this reason the geochemical classification of sandstones does not mimic the conventional mineralogical classification of sandstones based upon quartz-feldspar-lithic fragments. Rather it differentiates between mature and immature sediments. 

Table3.2 Relation ofthe terminology of AUiboneetal. (1993a, b) to the classification of the igneous and metamorphic rocks in Victoria, Wright, and Taylor valleys by Allen and Gibson (1962), McKelvey and Webb (1962), and Haskell et al. (1965a), respectively...

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