Reconstructing the Mesoproterozoic palaeogeography of northern Australia through coupled detrital thermo- and geo-chronometers

Yang, Bo1, Collins, Alan1, 2, Blades, Morgan1, Jourdan, Fred3

 1Tectonics and Earth Systems Research Group, Mawson Centre for Geosciences (MCG), Department of Earth Sciences, The University of Adelaide, SA 5005, Australia, 2Mineral Exploration Cooperative Research Centre (MinEX CRC), WA 6151, Australia, 3Western Australian Argon Isotope Facility, Department of Applied Geology, Curtin University, Perth, WA 6845, Australia.

This study presents detrital muscovite 40Ar/39Ar data from the Mesoproterozoic Roper Group and the overlying latest Mesoproterozoic to early Neoproterozoic unnamed successions in the Beetaloo Sub-basin, northern Australia. Detrital muscovite chronology, compiled with the previous detrital zircon data, is used to identify basin source regions, providing integrated thermo- and geo- constraints on the basin provenance. The coupled detrital thermo- and geo-chronometers illustrate a dynamics tectonothermal history of the North Australia Craton (NAC) through the Mesoproterozoic. 

Data show that the Bessie Creek Sandstone, the oldest analysed formation from the Roper Group, provenance from multiple sources, whereas the overlying formation (the Velkerri Formation) consists of detritus from a dominant source. The predominant ca. 1.48 Ga muscovite and ca. 1.60 Ga zircon analyses seen in the Velkerri Formation closely match the published data from the exposed basement rocks to the southeast of the basin (e.g. Mt Isa Region, South Australia Craton (SAC), and the palinspastically adjacent Georgetown Province).These southeast source regions are located along the eastern margin of the Proterozoic Australia, and would have been uplifted, as rift-shoulders, during the separating between the Proterozoic Australia and the Laurentia at ca. 1.45 Ga. The uplifted southeast sources then became the most significant topographic highs, and subsequently swamped the basin with ca. 1.47 Ga detrital muscovite grains as well as the ca. 1.60 Ga detrital zircon grains, as those seen in the Velkerri Formation. The successions overlying the Velkerri Formation exhibit a gradually increased introduction of southern sources derived detritus. Data show that the Kyalla Formation, the youngest analysed formation from the Roper Group, was predominately sourced from the southern sources (e.g. Aileron Province and Tanami Region). The coeval absence of ca.1.47 Ga detrital muscovite and ca. 1.60 Ga detrital zircon grains indicates the Kyalla Formation received little contributions from the southeast sources. Further, detrital muscovite 40Ar/39Ar data show that the cumulated lag time of the Kyalla Formation is distinctly longer than the underlying formations. This is interpreted to reflect a different exhumation mechanism within source regions corresponding to a changed tectonic setting. The change in provenance and tectonic background is interpreted to relate to the closure of an ocean basin during the period 1.35–1.25 Ga, which resulted in uplift of the southern margin of the North Australia Craton. 

The latest Mesoproterozoic to early Neoproterozoic sandstone successions overlying the Roper Group provenance from the Musgrave Province. Coupled detrital zircon and muscovite data imply a rapid cooling at ca. 1.20–1.15 Ga that is interpreted to reflect a syn-orogenic exhumation during the Musgrave Orogeny. This quick exhumation is temporally consistent with the syn-orogenic cooling and exhumation in the Albany-Fraser Orogen. The synchronous orogenic exhumation events, seen in the Albany-Fraser Orogen and the Musgrave Province respectively, might represent a coeval collision of the West Australia Craton with the combined NAC and SAC, at ca. 1.20 Ga.


Biography

Bo Yang works in tectonics, basin evolution, sedimentary geochronology and geochemistry. He completed his PhD at the University of Adelaide in 2019 and is currently working as a post-doc in the same university.

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