Palaeomagnetic dating and tectonic significance of dolerite intrusions in the Albany Mobile Belt, Western Australia

Dolerite dykes and sills in the Mesoproterozoic Albany Mobile Belt and Neoproterozoic Stirling Range Formation metasediments in southwestern Australia provide evidence for extensional events between Australia, East Antarctica and Greater India. Paleomagnetic analysis shows that primary remanence was carried by single domain magnetite for samples from seven localities. Palaeomagnetic poles for the majority of sites fall close to the earliest Cambrian part of the Australian apparent polar wander path (APWP). The interpreted earliest Cambrian dykes intrude both extensional (dominant) and shear fractures, indicating NNE-SSW extension between the Western Australian and East Antarctic Shields and a horizontal, ESE-WNW maximum compressive stress. Dyke emplacement appears to be contemporaneous with mafic volcanism in central and northern Australia and igneous intrusion in once contiguous parts of the East Antarctic Shield. These features are interpreted as being related to Gondwanaland assembly, and may represent a response to far-field stresses resulting from the collision between East and West Gondwanaland. nd suite of NW-striking, mid-Carboniferous dykes is related to NE-SW extension and rifting between Greater India and the Western Australian Shield during early stages in the formation of the Perth Basin in a sinistral transtensional regime along the southern Western Australian margin. A palaeopole from the primary remanence in a NNW-striking dolerite dyke falls on the poorly defined Triassic to Early Cretaceous part of the Australian APWP, indicating a possible third phase of dyke emplacement. Regional tectonic constraints for rifting in the Perth Basin suggest that this youngest dyke most likely intruded during the Triassic.