Australian‐derived detrital zircons in the Permian‐Triassic Gympie terrane (eastern Australia): Evidence for an autochthonous origin

Abstract

The Tasmanides in eastern Australia record accretionary processes along the eastern Gondwana margin during the Phanerozoic. The Gympie terrane is the easternmost segment of the Tasmanides, but whether its origin was autochthonous or allochthonous is a matter of debate. We present U-Pb ages of detrital zircons from Permian and Triassic sedimentary rocks of the Gympie terrane with the aim of tracing the source of the sediments and constraining their tectonic relationships with the Tasmanides. Our results show that the Permian stratigraphic units from the Gympie terrane mainly contain Carboniferous and Permian detrital zircons with dominant age peaks at~263 Ma,~300 Ma,~310 Ma, and~330 Ma. The provenance ages of the Triassic sedimentary units are similar (~256 Ma,~295 Ma, and~328 Ma) with an additional younger age peak of~240 Ma. This pattern of provenance ages from the Gympie terrane is correlative to episodes of magmatism in the adjacent component of the Tasmanides (New England Orogen), indicating that the detrital zircons were dominantly derived from the Australian continent. Given the widespread input of detrital zircons from the Tasmanides, we think that the sedimentary sequence of the Gympie terrane was deposited along the margin of the eastern Australian continent, possibly in association with a Permo-Triassic continental arc system. Our results do not show evidence for an exotic origin of the Gympie terrane, indicating that similarly to the vast majority of the Tasmanides, the Gympie terrane was genetically linked to the Australian continent.

Different styles of modern and ancient non-collisional orogens and implications for crustal growth: a Gondwanaland perspective

“…The probability plots of the two Gympie Arc samples of Li et al (2015) from the early-middle Permian part of the terrane, which postdates the main volcanism, show a peak of 264 Ma in one sample (probably from the onset of ssz7 continental margin arc to the west, Li et al 2015). A Late Carboniferous 306 Ma peak, together with small numbers of grains around 612, 900, and 1000 Ma, in the other (Fig.…”

“…Latest Carboniferous arc magmatism terminated at ϳ305 Ma and was followed by plate boundary rollback (Holcombe et al 1997), tracked by the nature of volcanism changing from calcalka- Li et al (2015), and Nambucca Basin, replotted from Shaanan et al (2015). (B) Hf zircon data from Gympie Arc Terrane compared to New England Orogen granitoid data of Kemp et al (2009).…”

“…6C, panel L). Several authors have argued for its allochthoneity (e.g., Harrington 1983; see below), but a more likely setting is that it was separated from Gondwanaland by a backarc basin and developed upon rifted fragments of accretionary complex crust (Sivell and McCulloch 2001;Glen 2013;Li et al 2015; but see Cawood et al 2011). The Gympie Arc was accreted by ϳ245 Ma, and stitched by 220 Ma granites.…”

The geometry, kinematics, and reactivation history of major fault systems in eastern Australia: implications for deformation phases from the Permian to Cenozoic

“…The Kin Kin beds are unconformably overlain by the North Arm Volcanics (Murphy et al, 1976), which have been dated at ca 213 Ma (Late Triassic) by K-Ar geochronology (Green and Webb, 1974). Detrital zircons from the Kin Kin beds have recently been shown to be as young as ca 240 Ma (Li et al, 2015), indicating that deformation must have occurred after ca 240 Ma but before the initiation of Late Triassic volcanism. I suggest that this deformation was likely contemporaneous with the observed contractional deformation in the Esk Trough and Nymboida Coal Measures.…”

Pre-Permian basement and lithological controls on the development of the Jellinbah Thrust Belt: Insight from a new palinspastic reconstruction

“…Initial timing of the events using biostratigraphy in the New England Orogen (Briggs, 1993) proved problematic due to a relatively low biostratigraphic yield for much of the rock record. More recent work on sensitive high resolution ion microprobe (SHRIMP) U-Pb dating of zircons (Korsch et al, 2009a, Line, 2011, Li et al, 2015 constrain the onset of the Hunter-Bowen Orogeny to the early Permian, circa 300 Ma. This coincides roughly with the initial formation of the Bowen Basin.…”