Crustal growth in the Archean: Insights from zircon petrochronology of the far-east Yilgarn Craton, Western Australia

The Archean Yilgarn Craton in Western Australia represents one of the key areas for investigating the mechanisms of crustal growth during Earth's infancy. The far-eastern margin of the Yilgarn Craton has, however, received limited scientific scrutiny. In this study, in-situ zircon petrochronology (U-Pb, O, and Lu-Hf isotopes) is used to constrain the formation and evolution of the easternmost Yamarna and Burtville regions as well as the encompassing Eastern Goldfields (Super)Terrane (EGT) of the Yilgarn Craton. The new data highlight the unequivocal existence of relatively old (ca. 2840 – 2775 Ma), compared to the EGT, and isotopically juvenile (εHf: +2.1 to +3.5) and mantle-like (δ¹⁸O: 5.2 to 5.9‰) crust at the eastern edge of the exposed craton. We refer to this crust as the ‘Dorothy Hills Block’. The Dorothy Hills Block shows geochronological and isotopic similarities with the adjacent ‘Burtville Block’ and the Youanmi Terrane (>400 km further west), which suggests a shared history up to ca. 2720 Ma. In addition, linear greenstone belts characterised by younger magmatism (ca. 2720 – 2660 Ma) with a constant, mildly supra-chondritic Hf isotope composition (εHf: 0.0 to +3.5) are identified between the Burtville and Dorothy Hills Blocks. We refer to this region as the ‘Yamarna Rift’, by analogy to the better-understood ‘Kalgoorlie-Kurnalpi Rift’. It is inferred that the Burtville and Dorothy Hills Blocks formed via peri-cratonic magmatism (ca. <2970 Ma), associated with mantle upwelling focused along the eastern edge of the ca. >3300 Ma Yilgarn proto-craton. The Yamarna and Kalgoorlie-Kurnalpi Rifts (ca. 2720 – 2660 Ma) overlie this extended older substrate and formed via intra-cratonic rifting broadly coeval with a major mantle upwelling event. The revised Meso- to Neoarchean crustal evolution model for the EGT, including new nomenclature, suggests a sustained (>200 Myr) and autochthonous geological development of the eastern Yilgarn Craton resulting from mantle upwelling events, potentially within a back-arc tectonic setting. Comparable crustal evolutionary trends are recorded in other Archean cratons (e.g., Superior Craton), which suggests that similar geodynamic regimes operated on a global scale in the Archean.