Shaping Western Australia's Geological Framework: Insights from the WA Array Phase One

In recent years, the deployment of extensive passive seismic arrays across Western Australia has significantly advanced our understanding of lithospheric structures. At the forefront of these efforts is the WA Array program, a transformative 10-year initiative featuring 1,600 broadband stations spanning the entire state of Western Australia. Launched in late 2022, the program has started generating a highly valuable dataset. The data and model outputs from Phase One (from December 2022 to December 2023) mark a long-term effort to compile a state-wide, high-resolution model that will evolve over the course of the program. By integrating this new data with insights from past and ongoing geophysical, geochemical and geological studies, the project aims to unravel the intricate lithospheric structure of the region, ultimately creating detailed models that illuminate Western Australia’s geological history and evolution.
Initial findings reveal significant shallow and crustal features. Measurements of the very shallow subsurface show strong correlation with tectonic setting and also mapped palaeovalleys which have uses in estimation of seismic hazard for engineering projects and potential targets for mineral exploration. Crustal models show significant lateral and vertical variations across geological domains, with the Perth Basin standing out as a prominent low-velocity zone, indicative of basin infill and history of the rifting along the margin of the adjoining craton. The Moho displays flat, distinct transitions in cratonic regions but varies west of the Darling Fault, reflecting the region’s complex tectonic setting. A pervasive NE-SW trend in Moho depth, seismic velocities, and isotopic data suggests compositional segmentation of the Yilgarn Craton into discrete blocks, challenging lateral accretion models and highlighting the influence of deep structures on crustal evolution and resource distribution. Lithospheric imaging further reveals compositional and thermal variations, including deep tectonic features beneath the Yilgarn Craton. An estimate of the lithosphere-asthenosphere boundary exhibits strong spatial correlations between the maximum gradient of the boundary with surface mineralization zones. These observations support the idea that tectonic architecture exerts a fundamental control on resource deposits, consistent with established theories linking deep lithospheric processes to mineral systems. These findings provide valuable insights into the tectonic evolution and resource potential of Western Australia.