Timing of Proterozoic metamorphism in the southern Curnamona Province: implications for tectonic models and continental reconstructions ∗

∗Appendix 1 [indicated by an asterisk (∗) in the text and listed at the end of the paper] is a Supplementary Paper; copies may be obtained from the Geological Society of Australia's website (www.gsa.org.au) or from the National Library of Australia's Pandora archive (http://nla.gov.au/nla.arc-25194).

Abstract

Chemical U – Th – Pb monazite ages from metasedimentary and meta-igneous units of the Willyama Supergroup have confirmed initial SHRIMP U – Pb metamorphic zircon ages constraining the onset of the earliest tectonometamorphic event (the Olarian Orogeny) at ca 1610 Ma in the southern Curnamona Province. An additional episode of high-grade metamorphism and heterogeneously distributed retrograde metamorphism and monazite recrystallisation occurred between ca 1570 and 1550 Ma. On the basis of monazite chemical U – Th – Pb ages from across the southern Curnamona Province, tectonometamorphic models based on ca 1690 Ma low-P, high-T metamorphism in the southern Curnamona Province are not supported. Furthermore, tectonic reconstructions that rely on the correlation of ca 1690 Ma deformation and metamorphism in the Broken Hill region with a similar aged event in the Mojave tarrane of southwestern Laurentia (AUSWUS) are not supported.

Key words:

• chemical uranium – thorium – lead dating
• Curnamona Province
• metamorphism
• monazite
• Proterozoic

Acknowledgements

Robin Offler and Michael Wingate are thanked for thoughtful reviews that greatly improved this manuscript. Allan Collins and Wolfgang Preiss are thanked for their comments on an earlier version of this manuscript. Dave Steele from University of Tasmania and John Terlet and Angus Netting from Adelaide Microscopy, University of Adelaide, are thanked for their assistance in setting up chemical dating of monazite, and maintenance of the SEM and electron microprobe. Rod Page and Barney Stevens are thanked for assisting with fieldwork in the Broken Hill region. Colin Conor, Wolfgang Preiss, Mike Szpunar, Alistair Crooks, Andy Burtt and Stuart Robertson from Primary Industries and Resources of South Australia are thanked for offering their time for many discussions on the geology of the Curnamona Province. This work was supported by an ARC Linkage grant LP0347342 to Martin Hand, Karin Barovich and John Foden.

Notes

∗Appendix 1 [indicated by an asterisk (∗) in the text and listed at the end of the paper] is a Supplementary Paper; copies may be obtained from the Geological Society of Australia's website (www.gsa.org.au) or from the National Library of Australia's Pandora archive (http://nla.gov.au/nla.arc-25194).