Tectono–thermal evolution of the east-central Australian intraplate: Rb–Sr, K–Ar and 40Ar/39Ar geochronology of authigenic illite.

Low-temperature geochronology using multiple isotopic systems is a powerful approach for reconstructing the tectono-thermal evolution of sedimentary basins. As individual dating techniques have distinct strengths and limitations, integrating complementary geochronological methods provides a more robust framework for constraining shallow-crustal thermal events. In this study, we examine the thermal and tectonic evolution of east-central Australia, from the eastern coast to the continental interior, through isotopic dating of authigenic illitic clay minerals. We integrate new and published Rb–Sr, K–Ar, and ⁴⁰Ar/³⁹Ar illite geochronology and critically assess the applicability of these methods when applied to low-temperature mineral systems.

Our results identify multiple episodes of thermal and fluid-flow activity during the Early Jurassic (~200–190 Ma), Middle Jurassic (~165 Ma), Early Cretaceous (~120–115 Ma), and Late Cretaceous (~100–95 Ma, ~85–80 Ma, and ~70 Ma). These events broadly coincide with periods of subduction-related orogenesis and rifting along eastern Australia. Jurassic illite ages from the Permo-Carboniferous Galilee Basin are nearly synchronous with the development of the Eromanga, Surat, and Clarence–Moreton basins, and reflect contemporaneous intraplate tectonism linked to subduction processes.Early Cretaceous ages correspond with magmatic activity in eastern Queensland, including the Whitsunday Volcanic Province, and associated arc- or rift-related tectonism. Late Cretaceous ages are consistent with apatite fission-track (AFT) data and indicate a regional extensional regime that culminated in sea-floor spreading east of the Australian continent.

Although these thermal events occurred far from the active Mesozoic plate margin, they are best explained by the dynamic effects of shallow subduction and/or the transmission of far-field stresses into a mechanically and thermally weakened continental interior, resulting in widespread subsidence, extension, and enhanced heat and fluid flow. These findings have important implications for energy and resource exploration, as Cretaceous tectonic reactivation defines fault zones that currently facilitate geothermal fluid upwelling in east-central Australia. Interaction of these fluids with Precambrian granitic basement rocks enriched in incompatible and radioactive elements highlights the potential of low-temperature geochronology to constrain the timing of fluid–rock interaction and to inform exploration strategies for critical metals and carbon-free gas resources in sedimentary basins.