Building Blocks of Cratonic Lithosphere in Southwestern Australia: Early Results of WA Array

Abstract

Using data from Western Australia (WA) Array—a decadal data acquisition project by the State government of WA—we construct a seismic profile crossing major tectonic units of the region. We perform converted-wave imaging of vertical gradients in seismic impedance and rock texture in conjunction with ambient noise tomography constraints on bulk seismic properties. With ∼40 km station spacing, we can detect lateral variations in seismic properties that correspond to major tectonic units. We outline lithospheric regions with similar seismic properties, and demonstrate the importance of interpreting seismic signatures of rock fabric. We show that major tectonic boundaries are inclined, identify an apparently cratonic fragment within the Proterozoic Albany–Fraser Orogen, refine boundaries of Neoarchean tectonic domains in the southwestern Yilgarn Craton, and document focused deformation at the crust-mantle boundary beneath one of these domains. Our findings strengthen the notion of cratonic lithosphere as a mosaic of distinct tectonic domains.