Seismic anisotropy analysis across Southwestern Australia reveals ENE‐trending lithospheric architecture linked to Archean Yilgarn Craton formation

The southwest region of Western Australia is one of the oldest continental regions on Earth, hosting the Archean Yilgarn Craton, bounded by the Proterozoic Albany-Fraser and Pinjarra orogens. Here we calculate shear wave splitting of the PKS and SKS teleseismic phases using stations from Phases 1 and 2 of the WA Array (average station spacing 40 km), as well as other temporary and permanent networks in the study region. We find evidence for coherent seismic anisotropy, with the regional average delay time (1.24 ± 0.62 s) comparable to the global average, δt = 1 s. Although fast polarization orientations show variation, they are not aligned with current plate motion and the expected asthenospheric flow direction. In the South West Terrane, fast polarization orientations match the trend of ancient structural faults. By contrast, structural faults in the Youanmi Terrane and the Eastern Goldfields Superterrane are oriented at an angle compared to the E–W and NE–SW fast polarizations. Instead, the seismic anisotropy pattern shows a striking similarity to E–W trending Precambrian (2.42 Ga) dykes that extend uninterrupted across the Yilgarn Craton. We propose that lithospheric fabrics frozen-in at the time of craton formation (~2.76–2.65 Ga) generated a mechanical weakness which subsequently influenced the orientation and emplacement of the dykes. Further evidence for a similar, ancient (~2.73 Ga) architectural fabric comes from recent isotope geochemistry analysis of primary ENE-trends within the Yilgarn Craton. Overall, these results point toward large-scale, fossilized lithospheric fabric within the Yilgarn Craton, preserved for over two billion years, offering a unique window into the formation and early evolution of the continent.