Finite-frequency tomography of the upper mantle beneath the proterozoic Capricorn Orogen in the central West Australian Craton

The Capricorn Orogen, central to the West Australian Craton (WAC) and flanked by the Pilbara Craton to the north and the Yilgarn Craton to the south, records complex tectonic processes spanning from the Archean to the Neoproterozoic, including two major Paleoproterozoic collisions—the 2,215–2,145 Ma Ophthalmia Orogeny and the 2,005–1,950 Ma Glenburgh Orogeny—that welded the two cratons. Using finite-frequency tomography, we present the first high-resolution P wave velocity model of the upper mantle beneath this region, providing new constraints on cratonic architecture and tectonic evolution. Our results reveal high-velocity anomalies beneath the Pilbara and Yilgarn Cratons, extending to depths of ∼150–200 km, indicative of thick cratonic keels. The northern edge of the Yilgarn Craton trends northeast, likely extending beneath sedimentary basins to connect with the Pilbara Craton. Its eastern surface trace aligns with the Goodin Fault, while its western margin lies south of the Narryer Terrane, a component of the northwest Yilgarn Craton, suggesting that southward translation of this terrane occurred during the Glenburgh and Capricorn Orogenies. The southern edge of the Pilbara Craton, marked by the Talga Fault, appears structurally diffuse, possibly reflecting its passive margin origins prior to collision. Low- (<−0.5%) velocity anomalies within the Capricorn Orogen suggest extensive mantle metasomatism, likely associated with subduction-driven hydration during the Ophthalmia and Glenburgh Orogenies. These findings provide new insights into the long-term stabilization and reworking of Archean lithosphere, underscoring the significance of early Paleoproterozoic orogenesis in shaping the deep structure of cratonic regions.