Naturaliste Plateau, offshore Western Australia: A submarine window into Gondwana assembly and breakup

  1. Jacqueline A. Halpin*,1,
  2. Anthony J. Crawford1,
  3. Nicholas G. Direen†,2,
  4. Millard F. Coffin3,
  5. Caroline J. Forbes§,4 and
  6. Irina Borissova5
  1. 11ARC Centre of Excellence in Ore Deposits, University of Tasmania, Private Bag 79, Hobart, TAS 7001, Australia
  2. 22Continental Evolution Research Group, University of Adelaide, DP 313, Adelaide, SA 5005, Australia
  3. 33National Oceanography Centre, Southampton, University of Southampton, Waterfront Campus European Way, Southampton SO14 3ZH, UK
  4. 44Geological Survey of Western Australia, 100 Plain Road, Perth, Western Australia 6004, Australia
  5. 55Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia
  1. *E-mail: jahalpin{at}utas.edu.au.

  • ↵† Current address: School of Earth Sciences, University of Tasmania, Private Bag 79, Hobart, TAS 7001, Australia.

  • ↵§ Current address: Centre for Mineral Exploration Under Cover, University of Adelaide, Adelaide SA 5005, Australia.

Abstract

The origin of the submarine Naturaliste Plateau off the southwestern coast of Australia is controversial; previous work supports both oceanic and continental affinities for the basement to volcanic and sedimentary sequences. We report the first evidence of reworked Mesoproterozoic (ca. 1230–1190 Ma) continental crust, based on laser ablation–inductively coupled plasma–mass spectrometry analysis of zircons from granite and orthogneiss samples dredged from the southern margin of the plateau. Thermobarometry of peak metamorphic minerals and electron microprobe chemical dating of monazite reveal that these igneous rocks were metamorphosed to ~700 °C and ~6.5 kbar during the Cambrian Pinjarra Orogeny at ca. 515 Ma. These data confirm a continental origin for a significant swathe of the southern Naturaliste Plateau, and suggest that the protoliths may have affinities to Mesoproterozoic crust within the Albany-Fraser-Wilkes Orogen (Australia-Antarctica). The present Naturaliste Plateau basement beneath its volcanic carapace probably represents a middle-to lower-crustal extensional allochthon exhumed during Cretaceous hyperextensional breakup between Australia and Antarctica.

    • Received 16 April 2008.
    • Revision received 2 July 2008.
    • Accepted 13 July 2008.
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  1. doi: 10.1130/G25059A.1 Geology October 2008 v. 36 no. 10 p. 807-810
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