Preserved intercratonic lithosphere reveals Proterozoic assembly of Australia

Abstract

The Proterozoic assembly of Australia, the understanding of which is critical for reconstructing Proterozoic supercontinents, involved amalgamation of the West Australian (WAC), North Australian (NAC), and South Australian cratons (SAC). However, the basement between these Archean to early Proterozoic lithospheric blocks is mostly buried beneath younger basins; hence, its composition and age and the timing of Proterozoic assembly remain uncertain. In situ zircon U-Pb-O-Hf analyses of igneous rocks from drillholes that intersected basement beneath the northwestern Canning Basin reveal the presence of a substantial domain of juvenile Proterozoic lithosphere, the Percival Lakes province, between the WAC and NAC. Although isotopically distinct from the neighboring WAC and NAC, the Percival Lakes province is strikingly similar to other juvenile Proterozoic tectonic elements between the WAC, NAC, and SAC. Combining isotope and seismic data, we interpret the Percival Lakes province as part of an ~1700 × 400 km Proterozoic lithospheric domain that lacks evidence of Archean provenance but consists mainly of reworked remnants of Mesoproterozoic oceanic crust that survived WAC-NAC-SAC convergence. The apparent absence of Archean lithosphere between the cratons implies they never directly collided or that complete collision was prevented by impingement of three-dimensional promontories in the converging lithospheric blocks. Instead, the Percival Lakes province and other Proterozoic elements between the WAC, NAC, and SAC consist of oceanic lithosphere extracted from Earth’s mantle in the Proterozoic. Our results imply that WAC-NAC convergence was younger than Columbia amalgamation at ca. 1.8 Ga and that Proterozoic Australia formed during the earliest phases of Rodinia assembly at ca. 1.3 Ga.

A linked evolution for granite-greenstone terranes of the Pilbara Craton from Nd and Hf isotopes, with implications for Archean continental growth

“…Whole rock hafnium (A) and neodymium (B) isotope data for the maficultramafic rocks of the Pilbara Craton analysed in this study (note that the data for seven ∼3.47 Ga basaltic samples reported byMurphy et al (2021), which were measured at WSU during the present study using the same techniques, are also plotted with the same symbols). Panel B also shows available Nd isotope data for felsic and mafic samples from across the Pilbara Craton (compiled inLu et al, 2022). Panel C compares the Hf isotope data from mafic-ultramafic rocks of this study with that published byNebel et al (2014), Hasenstab et al (2021 andTympel et al (2021).…”