Proterozoic crustal evolution of NE Australia during Nuna assembly: Insights from geophysical and radiogenic isotope data

Jiangyu Li1, H. K. H. Olierook2, 3, Zheng-Xiang Li1, Adam R. Nordsvan1, 4, Amaury Pourteau1, Silvia Volante1,5, Chris Elders2, William J. Collins1, Luc S. Doucet1

1Earth Dynamics Research Group, The Institute for Geoscience Research (TIGeR), School of Earth and Planetary Sciences, Curtin University, Perth, Australia, 2Faculty of Science and Engineering, The Institute for Geoscience Research (TIGeR), School of Earth and Planetary Sciences, Curtin University, Perth, Australia, 3Timescales of Mineral Systems, Centre for Exploration Targeting – Curtin Node, and John de Laeter Centre, Curtin University, GPO Box U1987, Perth, Australia, 4Department of Earth Sciences, University of Hong Kong, Pokfulam, China, 5Institute of Geology, Mineralogy and Geophysics, Ruhr-Universität Bochum, Bochum, Germany

The final assembly of the Proterozoic supercontinent Nuna occurred via a collisional event between Australia and Laurentia in NE Australia at ca. 1.60 Ga[1]. However, detailed collisional processes and the resulting orogenic architecture in NE Australia remain elusive. Here, we combine aeromagnetic[2] and gravity data[3] with surface geological data and a reinterpretation of seismic profiles[4-5] to depict the deep crustal structure that developed during this collisional event. Neodymium and hafnium isotopic data from Proterozoic mafic and felsic intrusions[6] were also compiled to investigate the crustal evolutionary processes. A N–S trending, distinctive terrane boundary is recognized on the eastern margin of the Mount Isa Inlier from the filtered aeromagnetic and gravity grid, coinciding with the Gidyea Suture Zone previously recognised from the seismic reflection data. Between the Mount Isa and Georgetown inliers, a west-dipping, crustal dissecting fault is interpreted as another suture zone with additional smaller-scale thrusts that are antithetic to the main suture. The duplexed crustal architectures between the Mount Isa and Georgetown inliers are interpreted to have formed during a crustal thickening event associated with the docking of the Georgetown Inlier along a west-dipping subduction zone. The Georgetown Inlier is isotopically distinguishable from the Mount Isa Inlier at ca. 1.68 Ga, but shares the same isotopic history after ca. 1.60 Ga. Subduction may have initiated at ca. 1.64 Ga but ceased at 1.60 Ga, with the Georgetown Inlier accreted to the Mount Isa Inlier, possibly along the Empress Suture Zone during the final Nuna assembly. 

[1] A Pourteau et al., Geology 46 (11), 959 (2018).

[2] M Greenwood, (2018).

[3] C Roger, (2014).

[4] JL Maher, (2008).

[5] JL Maher, (2009).

[6] D Champion, (2013).


Biography

Jiangyu Li is a Ph.D student joint the Earth Dynamic Group at Curtin University in 2017. His Ph.D. project involves understanding the Proterozoic crustal evolutionary process in NE Australia during the 1.6 Ga supercontinent Nuna assembly. His tools are Argon thermochronology, aeromagnetic and gravity data processing and seismic profile interpretation.

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