Contrasts between i- and s-type granitoids of the kosciusko batholith

R. Hine, I. S. Williams, B. W. Chappell, A. J R White, R. Hine, I. S. Williams

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Abstract

Two distinct groups of granitoids occur on the eastern side of the Kosciusko Batholith. Those considered to be derivatives of sedimentary source rocks (S-types) are usually foliated and either contain cordierite or white-mica secondary after cordierite. The granitoids produced from igneous source material (I-types) are generally massive and frequently contain hornblende. Geochemical parameters provide the best discriminant between the two groups, I-types have higher Ca, Al, Na2O/K2O, and Fe2O3/FeO, and lower Fe, Mg, Sc, V, Cr, Co, Ni, Cu, Zn, Ba, Rb, Th, La, Ce, and Y than S-types of comparable SiO2values. The differences between the two groups are not the result of differences in the melt-forming process but reflect differences in the nature of the source material. Thus the geochemical features of the S-type granitoids are indicative of their source rocks having been through a process of chemical weathering in a sedimentary cycle. Conversely, the I-type granitoids were derived from fractionated rocks that had not been involved in weathering processes.

Original languageEnglish
Pages (from-to)219-234
Number of pages16
JournalJournal of the Geological Society of Australia
Volume25
Issue number3-4
DOIs
Publication statusPublished - 1978

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Hine, R., Williams, I. S., Chappell, B. W., White, A. J. R., Hine, R., & Williams, I. S. (1978). Contrasts between i- and s-type granitoids of the kosciusko batholith. Journal of the Geological Society of Australia, 25(3-4), 219-234. https://doi.org/10.1080/00167617808729029