Oct 28, 1986 - Tulloch, A. J., and Brathwaite, R. L., 1986. Granitoid rocks and associated mineralization of Westland - West Nelson, New Zealand. NZ.
Journal of the Royal Society of New Zealand
ISSN: 0303-6758 (Print) 1175-8899 (Online) Journal homepage: http://www.tandfonline.com/loi/tnzr20
Classification of granitic rocks: A comment on Mason and Taylor (1987) Simon Nathan To cite this article: Simon Nathan (1987) Classification of granitic rocks: A comment on Mason and Taylor (1987), Journal of the Royal Society of New Zealand, 17:2, 138-138, DOI: 10.1080/03036758.1987.10423340 To link to this article: http://dx.doi.org/10.1080/03036758.1987.10423340
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Tulloch, A. J.,
1983. Granitoid rocks ofNew Zealand-a brief review. InJ. A. Roddick (Ed.): Circum-Pacijic Plutonic Terranes, pp. 5-20. Geological Society of America, Memoir 159.
Tulloch, A. J., and Brathwaite, R. L., 1986. Granitoid rocks and associated mineralization of Westland - West Nelson, New Zealand. NZ. Geological Survey Record 13: 65-92. Turner, F. J., 1933. The metamorphic and intrusive rocks of southern Westland. Transactions 0] the NZ. Institute 63: 178-284. Warren, G., 1967. Sheet 17, Hokitika (1st Ed.). Geological Map of New New Zealand 1 :250,000. DSIR, Wellington. White, A.
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Ultrametamorphism and granitoid genesis.
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- - - - - - 1983. Granitoid types and their distribution in the Lachlan Fold Belt, southeastern Australia. In J. A. Roddick (Ed.): Circum-Pacijic Plutonie Terranes, pp. 21-34. Geological Society of America, Memoir 159.
Wilbanks, J. R., 1972. Geology ofthe Fosdick Mountains, Marie Byrd Land. In R. J. Adie (Ed.): Antarctie Geology and Geophysics, pp. 277-284. Universitetsforlaget, Oslo, Norway. Young, D. J., 1968. The Fraser Formation in centtal Westland, New Zealand. NZ. Journal 0] Geology and Geophysies 11: 291-311. Reeeived 28 October 1986; aeeepted 16 Deeember 1986.
Classification of granitic rocks: a comment on Mason and Taylor (1987) Simon N athan * The naming of granitic rocks has long been a subject of debate; different systems of nomenclature have developed independently in Europe, England, and the USA. During the 1960s considerable international discussion led the Union ofGeological Sciences (lUGS) to create the Subcommis~ion on the Systematics ofIgneous Rocks, with the hope that a generally acceptable c1assification could be agreed on. The final report of the Subcommission (Streckeisen, 1976), now generally known as the Streckeisen c1assification, has been widely accepted. At a workshop on New Zealand granites in 1978 it was unanimously agreed to follow the Streckeisen c1assification, and this has been done in virtually all subsequently published work in New Zealand. Mason and Taylor (1987) state that they are using the Streckeisen c1assification "with the addition of an adamellite field for those rocks with subequal amounts of plagioclase and K-feldspar". U nfortunately this apparently minor amendment is a direct contradiction to one of the main points of the c1assification: to use the term granite for rocks with subequal amounts of quartz, plagioclase, and K-feldspar, which are generally the dominant lithology in most areas of granitoid rocks. As Streckeisen notes (p. 12):"It would not seem reasonable to assign to the most widespread granitic rocks any other name than that of granite". Streckeisen discussed the use ofthe term adamellite (pp. 12-13). Because ofits confused history, and because it is gene rally used as a synonym for rocks otherwise c1assified as granite, Streckeisen recommended that it should be abandoned.·This recommendation has been generally accepted in the literature over the last ten years; it is a pity that Mason and Taylor have revived this obsolete term, apparently only because of personal preference. In the interests of c1arity and uniformity, I urge readers to follow the internationally accepted c1assification, not the example of Mason and Taylor.
REFERENCES Streckeisen, A.,
1976.
To each plutonic rock its proper name. Earth Seimee Reviews 12: 1-33.
Mason, B., and Taylor, S. R., 1987. High-grade basement gneisses and granitoids in Westland, New Zealand. Journal 0] the Royal Society 0] NZ. 17: 115-138. •
New Zealand Geological Survey, Lower Hutt.
Reeeived 12 March 1987.
