Insights into changes in crust formation mechanisms across the Archean-Proterozoic Transition: Receiver function observations in the Capricorn Orogen, Western Australia

The transition from the Archean to Proterozoic marks a critical period in Earth’s tectonic history, where primary crustal formation mechanisms may have shifted from vertical-accretion mantle plume tectonics to horizontal-accretion modern-style plate tectonics. Seismological evidence suggests that this regime shift might have left imprints in the crust of stable regions. However, due to sparse spatial and temporal sampling, there is no global consensus on whether seismic observations can infer the secular evolution of crustal characteristics. In this study, we utilized a dense seismic array deployed in the Capricorn Orogen of the West Australian Craton. By analyzing teleseismic receiver functions, we characterized the crustal V_P/V_S ratio and interface features across approximately two billion years of Archean to Proterozoic craton crust and correlated these observations with the two-stage Nd age model of surficial rocks. Our results indicate that during the Mesoarchean to Paleoproterozoic, crustal thickness in the Capricorn Orogen gradually increased. The changes of V_P/V_S ratio suggest a crustal evolution from felsic to more intermediate compositions, and the Moho gradient evolves from sharp to gradational. Significant crustal thickening and mafic compositions were observed along major block boundaries, accompanied by weak Moho amplitudes, and asymmetrically dipping Moho, spatially correlating with the Ophthalmia Orogeny (∼2.2 Ga) and the Glenburgh Orogeny (∼2.0 Ga). We propose that these changes in the crustal characteristic initially originated during these two collisional orogenies and were further modified by post-collision thermal and deformational events. Similar features are evident in seismic observations across many Precambrian subduction zones. Thus, we infer that around 2.2 to 2.0 billion years ago, primary crustal formation mechanisms in the West Australian Craton had transitioned to horizontal accretion modern plate tectonics. This study reveals the geometrical characteristics of Neoarchean to Paleoproterozoic subduction, providing new deep constraints for understanding the Archean-Proterozoic crustal accretion and geodynamic regime transitions.