Fergusson, C.L., and Henderson, R.A. (2015) Early Palaeozoic continental growth in the Tasmanides of northeast Gondwana and its implications for Rodinia assembly and rifting. Gondwana Research, 28 (3). pp. 933-953.

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Abstract

Gondwana formed in the Neoproterozoic to Cambrian mainly from collision along the East African and Kuunga orogens at about the same time that the Gondwana palaeo-Pacific facing margin became a long-lived active margin and formed the Terra Australis Orogen. This orogen, and in particular the Tasman Orogenic Belt (the Tasmanides) sector of eastern Australia, is distinguished by widespread shortening of quartz turbidite successions and underlying oceanic basement, with less abundant island arc assemblages. Early Palaeozoic accretionary development of the Tasmanides followed Rodinia breakup at 800–750 Ma to form the palaeo-Pacific Ocean. In eastern Australia, a second rifting episode at 600–580 Ma is more widely developed with siliciclastic sedimentation and rift-related igneous activity. In parts of the Delamerian Orogen of South Australia and northwestern New South Wales and in the exposed northern Thomson Orogen of north and central Queensland, the rift-related sedimentary successions have a dominant 1.3 to 1 Ga detrital zircon age signature implying local sources. They are considered to be derived from an eastward continuation of the 1.3–1 Ga Musgrave Province in central Australia, which marks a major Late Mesoproterozoic suture between the North Australian and South Australian/West Australian cratons and now buried within continental crust of the Thomson Orogen. Palaeomagnetic data suggest that an intraplate 40° anticlockwise rotation occurred between the North Australian Craton and an amalgam of the West and South Australian cratons during the transpressional Petermann Orogeny in central Australia at 650 to 550 Ma and overlapped the 600–580 Ma rifting event. The zone of rotational intraplate shearing is considered to have remobilised the preceding Late Mesoproterozoic suture and provides a marker in Rodinia that supports the AUSMEX reconstruction. Detrital zircon of 650–500 Ma, known as the Pacific–Gondwana association, is very widely represented in Phanerozoic sediment of eastern Australia. It may be that an upper crustal igneous assemblage, now removed by erosion, developed in the Petermann Orogeny contributed to part of this age association. However, a primary Antarctic far-field source is favoured. Given that prior to 650 Ma, the unravelled intraplate rotation shows substantial overlap of the Thomson Orogen and the South Australian Craton, much of the former must have developed by continental growth largely after 550 Ma. The Diamantina Structure, which truncates the Mount Isa Province and forms the northwestern margin of the Thomson Orogen, marks the eastern line of intraplate rotation. This zone of crustal weakness continues into the northern Thomson Orogen where it was remobilised in the mid-Palaeozoic to offset the Mossman Orogen and to later facilitate the Late Mesozoic–Cenozoic Townsville Trough and basin, a major feature of the continental margin. Basement cores and bedrock geology of the Thomson Orogen indicate deposition of widespread quartzose turbidites dominated by Pacific–Gondwana detrital zircon ages (650–500 Ma) that were affected by inferred Middle to Late Cambrian deformation and metamorphism (Delamerian Orogeny). The widespread Delamerian event was succeeded by Late Cambrian–Early Ordovician backarc extension and dominantly silicic igneous activity with granites, volcanic and volcaniclastic successions in the northern Thomson Orogen. Ordovician quartz turbidite deposition followed by compressional deformation in the Late Ordovician–Early Silurian Benambran Orogeny and scattered syn- and post-orogenic granitic plutonism is characteristic of northeast Gondwana and dominates rock assemblages of the Lachlan Orogen.

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