Abstract
The Nandewar Mountains, N.S.W., Australia, are the remains of a Miocene continental alkaline volcano whose products range from olivine basalts to comendites and alkali rhyolites. Intermediate hawaiites, mugearites and benmoreites predominate in the shield, in which olivine basalts are rare, and the trachytic rocks form many intrusions into the shield. The Nandewar alkaline series shows extreme fractionation of a relatively differentiated alkali olivine basalt magma, saturated with silica, to yield extremely oversaturated peralkaline comendites and peraluminous alkali rhyolites. The nature of the ferromagnesian phases forming was controlled by low oxygen fugacities. Throughout the series clinopyroxenes range from diopsidic augite, through sodic ferrohedenbergites to hedenbergite-acmite solid solutions. Riebeckite-arfvedsonite solid solutions appear in the trachytes and comendites, and aenigmatite appears in some of the peralkaline rocks. The feldspars in the series fractionate from calcic labradorite through potash oligoclase and calcic anothoclase towards the minimum melting alkali feldspar composition, Ab65Or35. The compositions of the alkali rhyolites approach the minimum in the system SiO2-KAlSi3O8-NaAlSi3O8. All the mineralogical and chemical evidence points to the development of the Nandewar series by the processes of extreme crystallization differentiation of an alkali olivine basalt parent magma. No significant contamination occurred, xenoliths and xenocrysts are absent, and volatile transfer and metasomatism played a minor role.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Abbott, M. J.: K and Rb in a continental alkaline igneous rock suite. Geochim. et Cosmochim. Acta 31, 1035–1041 (1967a).
—: Aenigmatite from the groundmass of a peralkaline trachyte. Am. Mineralogist 52, 1895–1901 (1967b).
Aoki, K. I.: Clinopyroxenes from alkaline rocks of Japan. Am. Mineralogist 49, 1199–1223 (1964).
Bailey, D. K., and J. F. Schairer: Feldspar-liquid equilibria in peralkaline liquids — the orthoclase effect. Am. J. Sci. 262, 1198–1206 (1964).
— —: The system Na2O-Al2O3-Fe2O3-SiO2 at 1 atmosphere, and the petrogenesis of alkaline rocks. J. Petrology 7, 114–170 (1966).
Bowen, N. L.: Phase equilibria bearing on the origin and differentiation of alkaline rocks. Am. J. Sci. 243A, Daly vol., 75–89 (1945).
Buddington, A. F., and D. H. Lindsley: Iron-titanium oxide minerals and synthetic equivalents. J. Petrology 5, 310–357 (1964).
Carmichael, I. S. E.: The feldspar phenocrysts of some Tertiary acid glasses. Mineral. Mag. 32, 587–608 (1960).
—: Pantelleritic liquids and their phenocrysts. Mineral. Mag. 33, 86–113 (1962).
—: The crystallization of feldspar in volcanic acid liquids. Quart. J. Geol. Soc. London 119, 95–131 (1963).
—: Natural liquids and the phonolitic minimum. Geol. J. 4, 55–60 (1964).
Chayes, F., and E. G. Zies: Sanidine phenocrysts in some peralkaline volcanic rocks. Ann. Rept. Gephys. Lab. Yearbook 61, 112–118 (1962).
Deer, W. A., R. A. Howie, and J. Zussman: Rock forming minerals, vol. 2, Chain silicates. London: Longmans 1963.
Edwards, A. B.: Three olivine basalt—trachyte provinces and some theories of petrogenesis. Proc. Roy. Soc. Victoria 48, 13–26 (1935).
—: The tertiary volcanic rocks of Central Victoria. Quart. J. Geol. Soc. London 94, 243–320 (1938a).
—: Petrology of the tertiary older volcanic rocks of Victoria. Proc. Roy. Soc. Victoria 51, 73–98 (1938b).
Ernst, W. G.: Synthesis, stability relations, and occurrence of riebeckite and riebeckitearfvedsonite solid solutions. J. Geol. 70, 689–736 (1962).
Jensen, H. I.: Geology of the volcanic area of the East Moreton and Wide Bay districts of Queensland. Proc. Linnean Soc. N.S.Wales 31, 73–173 (1906).
—: The geology of the Warrumbungle Mountains. Proc. Linnean Soc. N. S. Wales 32, 557–626 (1907a).
—: The geology of the Nandewar Mountains. Proc. Linnean Soc. N. S. Wales 32, 842–914 (1907b).
Joplin, G. A.: A petrography of Australian igneous rocks. Sydney: Angus & Robertson 1964.
LeMaitre, R. W.: Petrology of volcanic rocks, Gough Island, South Atlantic. Geol. Soc. Am. Bull. 73, 1309–1340 (1962).
Lindsley, D. H.: Accessory minerals. Investigations in the system FeO-Fe2O3-TiO2. Ann. Rept. Geophys. Lab. Yearbook 61, 100–106 (1962).
MacDonald, G. A.: Dissimilarity of continental and oceanic rock types. J. Petrology 1, 172–177 (1960).
McDougall, I., and J. F. G. Wilkinson: Potassium-argon dates on some Cainozoic volcanic rocks from Northeastern New South Wales. J. Geol. Soc. Australia 14, 225–233 (1967).
Muir, I. D., and C. E. Tilley: Mugearites and their place in alkali igneous rock series. J. Geol. 69, 186–203 (1961).
Nockolds, S. R., and R. Allen: The geochemistry of some igneous rock series. Part 2. Geochim. et Cosmochim. Acta 5, 253–276 (1954).
Norrish, K., and B. W. Chappell: X-ray fluorescence spectrography. In: Physical methods in determinative mineralogy (ed. J. Zussman). London: Academic Press 1967.
Richards, H. C.: The volcanic rocks of South-Eastern Queensland. Proc. Roy. Soc. Queensland 27, 105–204 (1916).
Stipp, J. J., and I. McDougall: Australian J. Sci. (in press).
Taylor, S. R.: The application of trace element data to problems in petrology. Phys. Chem. of the Earth 6, 133–213 (1965).
Thornton, C. P., and O. F. Tuttle: Chemistry of igneous rocks. I. The differentiation index. Am. J. Sci. 258, 664–684 (1960).
Tilley, C. E., and I. D. Muir: Intermediate members of the oceanic basalt — trachyte association. Geol. Fören. i Stockholm Förh. 85, 434–443 (1964).
Turner, F. J., and J. Verhoogen: Igneous and metamorphic petrology. New York: McGraw-Hill Book Co. 1960.
Tuttle, O. F.: Optical studies on alkali feldspars. Am. J. Sci. 250 A, Bowen vol., 553–567 (1952).
—, and N. L. Bowen: Origin of granite in the light of experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O. Geol. Soc. Am. Mem. 74, 1–153 (1958).
Upton, B. G. J.: The geology of Tugtutoq and neighbouring islands, South Greenland. Part II Nordmarkitic syenites and related alkaline rocks. Medd. Grønland 169, no. 2 (1964).
Watkins, N. D., and S. E. Haggerty: Primary oxidation variation and petrogenesis in a single lava. Contr. Mineral. and Petrol. 15, 251–271 (1967).
Webb, A. W., N. C. Stevens, and I. McDougall: Isotopic age determinations on tertiary volcanic rocks and intrusions of South-Eastern Queensland. Proc. Roy. Soc. Queensland 79, 79–92 (1967).
Wilkinson, J. F. G.: Clinopyroxenes of alkali olivine-basalt magma. Am. Mineralogist 41, 724–743 (1956).
—: The clinopyroxenes of a differentiated teschenite sill near Gunnedah, New South Wales. Geol. Mag. 94, 123–134 (1957).
Yagi, K.: The system acmite-diopside and its bearing on the stability relations of natural pyroxenes of the acmite-hedenbergite-diopside series. Am. Mineralogist 51, 976–1000 (1966).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Abbott, M.J. Petrology of the Nandewar Volcano, N.S.W., Australia. Contr. Mineral. and Petrol. 20, 115–134 (1969). https://doi.org/10.1007/BF00399627
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00399627