Continuation of the New England Orogen, Australia, beneath the Queensland Plateau and Lord Howe Rise

Abstract

Greywacke, argillite, greyschist and hypabyssal igneous rocks have been obtained from an Ocean Drilling Program core on the Queensland Plateau and from xenoliths in a volcanic breccia dredged from the crest of the Lord Howe Rise. Low to intermediate detrital quartz contents, 260 – 240 Ma K – Ar ages, and only moderately radiogenic Sr and Nd isotope compositions, suggest a correlation with the New England Orogen of eastern Australia, rather than with Australia's Lachlan Orogen or other adjacent geological provinces. Our results indicate that the New England Orogen terranes continue towards New Zealand at least as far as the southern Lord Howe Rise. The projected offshore boundaries of the major east Australian orogens are now known with more confidence, and do not appear to require any major cross-orogen offsets.

Key words:

• geochemistry
• Lord Howe Rise
• New England Orogen
• Ocean Drilling Program
• petrology
• potassium – argon dating
• Queensland Plateau
• strontium isotopes

Acknowledgements

We thank the NORFANZ cruise leader, Clive Roberts, and the staff of the Ocean Drilling Program core repository for providing samples. We are grateful to John Simes, Neville Orr and John Hunt for their technical support. We have had useful discussions with Cec Murray, Scott Bryan, Hamish Campbell, Chris Adams and Russell Korsch. Earlier versions of the manuscript were improved by comments from Andy Tulloch, Peter Cawood, Sebastien Meffre and Cec Murray. Funding was provided by the Foundation for Research Science & Technology (Mineral Wealth of New Zealand Programme).