Stratigraphic and geochronological constraints on the supracrustal succession of the South West Terrane of the Yilgarn Craton of Western Australia: Insight into Archean terrane amalgamation

• Contrasting geodynamic mechanisms simultaneously drive craton growth. • Case study into the evolution of the western Yilgarn Craton. • Early history of the South West Terrane is not shared across terrane boundarys. • Documentation of a Paleoarchean history in the South West Terrane. An outstanding question in Archean geodynamics is how the earliest continental crust was formed and stabilised, and how similar this process was to what is observed in the present day. Continental crust formation is often proxied by evidence of either allochthonous processes, such as terrane accretion and other subduction-like processes, or autochthonous processes involving in situ crustal growth and reworking. Subsequent interpretations are typically expressed in the terrane nomenclature for a given craton. An example is the Yilgarn Craton of Western Australia, which is associated with a wide range of tectonic models that incorporate various combinations of autochthonous and allochthonous processes. Despite these models, the South West Terrane and its connection to the rest of the Yilgarn Craton remain poorly understood. Here, this study addresses this paucity of data by reassessing the stratigraphic and magmatic history of the Toodyay area in the northern South West Terrane using integrated field mapping, U–Pb zircon geochronology, and Sm–Nd isotopic data. Our new data reveal evidence for a multistage Paleoarchean history of the South West Terrane, which modifies models of craton assembly. The > 3234 Ma Toodyay Formation is defined, which records a younger, more juvenile provenance distinct from age-equivalent quartzites in the Youanmi and Narryer Terranes of the Yilgarn Craton. Deposition was followed by 3234 ± 2 Ma magmatism and subsequent large-scale erosion, preserved as a unique unconformity spanning ages that are well represented in the rest of the craton. After this apparent hiatus, younger granitic suites (<2700 Ma) were emplaced in the South West Terrane that share geochemical signatures with coeval granites in the Youanmi Terrane. We interpret these data to indicate that an initially isolated South West Terrane was later juxtaposed with the Youami Terrane through lateral accretion, coinciding with extensive autochthonous growth in the Eastern Yilgarn (<2720). This suggests that allochthonous and autochthonous processes operated concurrently during craton formation and evolution, underscoring the complexity of Archean geodynamics beyond simple autochthonous or allochthonous models.