Foreign contemporaries – Unravelling disparate isotopic signatures from Mesoproterozoic Central and Western Australia

Abstract

Extensive time constrained isotopic (Sm–Nd, Lu–Hf) datasets on samples with well-studied geological context demonstrates that the Musgrave Province of central Australia and the Albany–Fraser Orogen of south Western Australia evolved through temporally similar Mesoproterozoic orogenies – at 1345–1260 and 1215–1140Ma – but on completely different basement. The West and North Australian Cratons amalgamated before the 1345–1260Ma event, which saw the convergence and final amalgamation of those combined cratons with the South Australian Craton. Well-defined Nd- and Hf-isotopic evolution arrays for the Musgrave Province reflect a juvenile basement with distinct 1950–1900, 1600–1550Ma crust formation events. Rare non-radiogenic material is seen only in detritus and in magmas that assimilated this material. This evolved detritus was derived from non-Yilgarn Archean sources, and reworked Archean sources, which were added to sedimentary basins developed over the Musgrave Province basement during and after c. 1400Ma. To the south of the Musgrave Province, the Madura Province has a similarly radiogenic signature to the Musgrave Province and is likely contiguous with it beneath younger cover sequences. It shows 2.0–1.4Ma mantle extraction ages and is dominated by juvenile rocks reflecting oceanic crust consumed to the north of the South Australian Craton and east of the West Australian Craton. Available data support the suggestion that the Musgrave Province is simply modified Madura Province crust situated along the edge of the North Australian Craton. Together, the Musgrave Province and the Madura Province represent Proterozoic Australia's most juvenile crustal remnant. In stark contrast to this juvenile remnant, the isotopic evolution array for the Albany–Fraser Orogen reveals a much more evolved signature, charting progressive juvenile input into an Archean source with strong isotopic and age similarity to the Yilgarn Craton of the West Australian Craton.