The Tertiary Volcanic Rocks of Central Victoria

Abstract

The Tertiary era in Victoria was marked by two extensive periods of intermittent vulcanicity; one ranging from the Oligocene to the Middle Miocene (Older Volcanic Series), the other from the Pliocene to the Recent (Newer Volcanic Series). The Older Volcanic Series, now greatly eroded, occurs mostly south and east of Melbourne. The Newer Volcanic Series, which has suffered much less erosion, extends north-west and west from Melbourne as a broad plain of about 10,000 square miles in area, and forms the floor of the Great Valley of Victoria. This paper is concerned with lavas of the Newer Volcanic Series lying between longitudes 144° E. and 145° E. (Fig. 1). The Geological Survey of Victoria generously provided facilities for cutting 500 thin sections, and lent to me another 500 slides on my departure for England, besides putting at my disposal maps, literature, and unpublished analyses. Mr. D. E. Thomas, of the Survey, in conjunction with whom the detailed field work was done, generously withdrew from the work. Fifty chemical analyses were prepared in the Geochemistry Department, Imperial College of Science and Technology, London, under Dr. H. F. Harwood. Much helpful criticism was received from Professors Boswell and Brammall, and my thanks are due to Dr. G. W. Tyrrell of Glasgow and Dr. E. S. Hills of Melbourne for reading the manuscript, and to Professor Brammall for seeing the paper through the press. P revious L iterature A bibliography of references to Victorian basalts is provided in Professor Skeats's Presidential Address, on the volcanic

Geochemistry and petrogenesis of the newer basalts of Victoria and South Australia

“…H. Green, unpubl. data) and within the Older Volcanics of Victoria (Edwards, 1938a). Normatively, they are varieties of basanite and nepheline mugearite, although they differ significantly from the basanites of the Western District in their lower K 2 O, SiO 2 , and A1 2 O 3 , coupled with higher CaO, TiO 2 ', and P 2 O 5 .…”

“…The first, in the Palaeocene to Early Miocene, is represented by the Older Volcanics, which occur as eroded plugs and flow remnants chiefly in Gippsland (eastern Victoria), but also sporadically to the north and west of Melbourne (see Singleton & Joyce, 1969;Edwards, 1938a). Post-Miocene volcanic activity is represented by the Newer Volcanics, which were erupted chiefly from Late Pliocene to Recent over large areas of Victoria (the Western District Plains, Werribee Plains, and Central Highlands) and in a small region in the far southeast of South Australia (see Fig.…”

The magmatic affinities of some volcanic rocks from the Tweed Shield Volcano, S.E. Queensland — N.E. New South Wales

“…The olivine 1 There are comparatively few descriptions of tholeiitic lavas from the East Australian mainland. However, the norm of the average of 16 labradorite-basalts (Footscray and Trentham types) from the Newer Volcanic Series of Victoria, widely cited as a typical alkaline series, contains 12-9 Di, 21 -3 Hy, 0-1 Ol (SiO 2 49-86, Fe 2 O 3 4-21, FeO 7-02, Na 2 O 2-80, K 2 O 1 -23 per cent) (Edwards, 1938, (Kuno et al, 1957), the Red Hill dolerite-granophyre association, Tasmania (McDougall, 1962), and Thingmuli volcano, Iceland (Carmichael, 1964) are also indicated. Note that the Thingmuli trend does not include any accumulative rocks and that some variants at Red Hill plot at low differentiation indices below the potash trend.…”

Magnetic and chemical stratigraphy for the Werribee Plains basaltic lava flow-field, Newer Volcanics Province, southeast Australia: implications for eruption frequency

“…The main interest of many studies of the Newer Volcanics Province has been the geochemistry and petrogenesis of the magmas (Edwards 1938;Irving & Green 1976;Frey et al 1978;McDonough et al 1985;Price et al 1997;Vogel & Keays 1997). Due to poor outcrop, few stratigraphic studies have been attempted (Price et al 1997), and issues such as whether the composition of the magmas in the Newer Volcanics Province has changed with time, have been difficult to address.…”