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Significance of clinopyroxene compositions from the Cudgegong Volcanics and Toolamanang Volcanics: Cudgegong-Mudgee district, NSW, Australia

  • J. W. Pemberton (a1) and R. Offler (a2)

Synopis

Clinopyroxene phenocrysts and groundmass crystals are relict phases in altered basalt and basaltic andesite lavas, and arenites of the Cudgegong Volcanics and Toolamanang Volcanics, Cudgegong-Mudgee district, New South Wales. Petrography, field relationships and clinopyroxene compositions indicate that basaltic blocks in the latter unit are reworked from the Cudgegong Volcanics. Clinopyroxene phenocrysts show a restricted compositional range and minor Feenrichment from core to rim, features considered indicative of a calc-alkaline parent magma. It is proposed that the Cudgegong Volcanics crystallized under hydrous conditions, at least in the later stages, with rising f O 2 resulting in a Fe-Ti oxide crystallizing as a primary phase. The clinopyroxenes are considered to have crystallized at moderate (5–6 kbar) and falling pressures and at minimum temperatures in the range 900 to 1000°C. Coupled substitutions affecting the “other” components in the clinopyroxene structural formula indicate that the ivAl-viFe3+, ivAl-viAl and ivAl-viTi4+ couples are important. The Sofala Volcanics, south of the study area, and the Cudgegong Volcanics are similar in age, petrography and stratigraphic position, and contain relict clinopyroxenes which are chemically similar. This suggests that the units are laterally equivalent and adds further evidence to the proposal that an oceanic island arc system was active in central western New South Wales during the Late Ordovician.

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Aokl, K., and Kushiro, I. (1968) Contrib. Mineral. Petrol. 18, 326-37.
Barton, B.J. (1976) Am. J. Sci. 276, 604-36.
Barton, B.J. and Barron, L.M. (1976) Am. J. Sci, 276, 637-69.
Bender, J.F., Hodges, F.N., and Beaus, A. E. (1978) Earth Planet. Sci. Lett. 41. 277302.
Best, E.G., and Mercy, E.L.P. (1967) Am. Mineral. 52, 436-75.
Cas, R. (1980) Geol. Soc. Austr. A.S.G. Conference Abstracts 2, 64-5.
Coish, R.A. and Taylor, L.A. (1978) Geol. Soc. AM. Pres. and Abstr. Toronto Heetlng, 382.
Deer, W.A., Howie, R.A., and Zussman, J. (1971) An Introduction to the Rock Forming Minerals. Longman. London.
Ewart, A. (1976) In Trondhjemltes, Dacites and Related Rocks. F. Barker (ed.)
Fodor, R.V. (1971) Earth Planet. Sci. Lett, 11, 385-90.
Fodor, R.V., Keil, K., and Bunch, T.E. (1975) Contrib. Mineral. Petrol. 50, 173-95.
Garcia, M.O. (1978) Earth sci. Rev. 14, 147-65.
Gibb, F.G.F. (1973) J. Petrol. 14-2, 203-30.
Gill, J.B. (1981) Orogenic Andesltes and Plate Tectonics. Spriztger-Verlag, New York.
Green, T.H. (1972) Cotrib. Mineral. Petrol. 34. 150-66.
Grove, T.L., Gerlach, D.C., and Sando, T.W. (1982) Contrib. Mineral. Petrol. 80, 160-82.
Hellman, P.L., Smith, R.E., and Henderson, F. (1977) Contrib. Mineral. Petrol. 63. 135-64.
Huekenholz, H.G., Schairer, J.F., and Yoder, H.S. Jnr. (1969) Mineral. Soc. Am. Spec. Pep. 2, 163-77.
Kay S., Mahlborg, Kay, R.W., Brueckner, H.K., and Rubenstone, J.L. (1983) Contrib, Mineral. Petrol. 82-1, 99116.
Leterrier, J., Maury, R.C., Thonon, P., Girard, D., and Marchal, M. (1982) Earth Plant. Sci. Left. 59, 139-54.
Lindsley, D.H. (1983) Am. Mineral. 68, 677-93.
Lindsley, D.H. and Andersen, D.J. (1983) J. Geophys. Res. 88, 887906.
Marcelot, G., Maury, R.C., and Le Fevre, C. (1983) Lithos 16, 133-51.
Mevel, C., and Velde, B. (1976) Earth Planet. Sci. Lett. 32, 158-66,
Morse, S.A. (1980) Basalts and Phase Diagram Springer-Verlag, New York.
Mueller, R,F., and Saxena, S.K, (1977) Chemical Petrology Springer-Verlag, New York.
Mullen, K.D. (1983) Earth Planet. Sci. Lett. 62, 5362.
Nash, W.P., and Wilkinson, J.F.G. (1970) Contrib. Mineral, Petrol, 28, 261-69
Nisbet, E.C., and Pearce, J.A. (1977) Coutrib. Mineral. Petrol. 65, 149-60.
Offler, R., and Pemberton, J.W. (1983) Geol. Soc. Anstr. Ahstr. 9, 62.
Osborn, E.F. (1959) Am. J. Sci. 257, 609-47.
Packham, G.H. (1968) Proc. Linnean Soe. New South Wales 93, 111-63.
Papike, J.J., Cameron, K.L., and Baldwin, K. (1974) Geol. Sue. Am. Abstr. 6, 1033-4.
Pemberton, J.W. (1980) J. Proc. R. Soc. New South Wales 113, 4962.
Pickett, J.W. (1982) Geol. Surv. New South Wales Unpubl. Palaeo. Report 82/10.
Poldervaart, A., and Hess, H.H. (1951) J. Geol. 59, 472-89.
Powell, C.MnA. (1982) Geol. Soc. Austr. Symposium Abstr. 6, 67.
Reed, S.J.B. and Ware, N.G. (1925) J. Petrol. 16. 499519.
Robinson, P. (1980) In Reviews in Mineralogy : vol. 7 Fyrozeaes. C.T. Prewitt (ed.). 419-90.
Scheibner, E. (1978) Teetonophysics 48, 153-7.
Smith, R.E. (1969) J. Petrol, 9, 191219.
Smith, R.E. and Smith, S.E. (1976) Earth Planet. Scl. Lett. 32, 114-20.
Traey, R.J., and Robinson, P. (1977) Am. Mineral. 62, 634-45.
Vieten, K. (1980) Neues. jahrb. Mineral. Abh. 140, 5488.
Wager, L.R. and Brown, G.M. (1968) Layered Igneous Rocks. Oliver Boyd, Edinburgh.
Wass, S.Y. (1979) Lithos 12, 115-32.

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