University of Tasmania

File(s) under permanent embargo

Multiple felsic events within post-10 Ma volcanism, Southeast Australia: inputs in appraising proposed magmatic models

journal contribution
posted on 2023-05-18, 06:58 authored by Sutherland, FL, Graham, IT, Hollis, JD, Sebastien MeffreSebastien Meffre, Zwingmann, H, Jourdan, F, Pogson, RE
Felsic episodes in young SE Australian volcanism were studied using new combined zircon U–Pb, feldspar 40Ar–39Ar and fission-track dating. Trachytes, xenocrysts in basalts and derived detrital crystals yielded an 8 Ma range for felsic sequences in the Macedon–Trentham (ca 8–5 Ma) and Western District (< 5–0.0 Ma) provinces of Victoria. At Newham, zircon and feldspar ages of 6.3–6.1 ± 0.1 Ma agree with the local basalt stratigraphy, while near Trentham zircon dating suggests felsic activity at ca 8.3 Ma and 6–5 Ma. Zircons crystallised in high-temperature crustal trachytes that evolved from alkali basalts, following amphibole crystallisation in the mantle (6.3 Ma Brimbank complex). The 8–5 Ma felsic episodes are attributed to lithospheric passage over an asthenospheric plume-like upwelling, now centred under Bass Strait. The Western District Province includes quartz-normative trachyte near Creswick (40Ar–39Ar age ca 2.4 ± 0.4 Ma), zircon xenocrysts in basalt near Daylesford (U–Pb age 1.8 ± 0.3 Ma) and zircon megacrysts in tuff at Bullenmerri maar (U–Pb zircon age 0.28 ± 0.04 Ma). The Creswick and Daylesford felsic phases may represent fractionation of basaltic icelandites during peak Western District volcanic activity. Bentonitic beds of trachyandesite affinities in NW Victoria–SE New South Wales lie in strata dated at ca 2 Ma and may mark a separate distal phase of peak Western District felsic volcanism. The E–W trend of post-5 Ma Western District basaltic activity has been attributed to lithospheric edge-driven or Tasman Fracture Zone fault-driven magmatic up-wells. However, new tomographic modelling of sublithospheric upper mantle suggests that Bassian asthenospheric inputs may explain young felsic components in adjacent basalts. Multiple felsic inputs allow greater appraisal of the young volcanic genesis and eruptive risks for the area.


Australian Research Council

AMIRA International Ltd

ARC C of E Industry Partner $ to be allocated

Anglo American Exploration Philippines Inc

AngloGold Ashanti Australia Limited

Australian National University

BHP Billiton Ltd

Barrick (Australia Pacific) PTY Limited

CSIRO Earth Science & Resource Engineering

Mineral Resources Tasmania

Minerals Council of Australia

Newcrest Mining Limited

Newmont Australia Ltd

Oz Minerals Australia Limited

Rio Tinto Exploration

St Barbara Limited

Teck Cominco Limited

University of Melbourne

University of Queensland

Zinifex Australia Ltd


Publication title

Australian Journal of Earth Sciences








School of Natural Sciences


Blackwell Publishing Asia

Place of publication

54 University St, P O Box 378, Carlton, Australia, Victoria, 3053

Rights statement

Copyright 2014 Geological Society of Australia

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences

Usage metrics

    University Of Tasmania


    Ref. manager