Examining tectonic scenarios using geodynamic numerical modelling: Halls Creek Orogen, Australia

Abstract Paleoproterozoic orogens record the accretion and collision of older tectonic blocks, and this record the tectonic development of a region. The Halls Creek Orogen (HCO) is a well-exposed Paleoproterozoic orogenic belts which can provide insight into the assembly of the Kimberley Craton to the Diamantina Craton during the Nuna Supercontinent amalgamation. Despite the relative abundance of rock exposure, there is still controversy as to how the Halls Creek Orogen developed. The 1865 Ma Tickalara Metamorphics seem to be a key unit within the Central Zone of the Halls Creek Orogen that can help solving the controversy. The formation of the protoliths to the Tickalara Metamorphics, and other sedimentary and igneous rocks of Central Zone have been described as either forming in: (1) an oceanic island arc setting above an easterly dipping subduction zone outboard of Kimberley Craton; or (2) an ensialic marginal basin located closer to the margin of Kimberley Craton. The two plausible tectonic scenarios of the Halls Creek Orogen are examined through 33 2D thermo-mechanical-petrological numerical experiments based on I2VIS code. The initial constraints for model setup aim to best represent the tectonic environment for the protoliths to the Tickalara Metaomorphics as either intra-ocean subduction or ocean-continent subduction and collision. With this approach, we were able to find experiments with specific physical parameters with results that are consistent with the geology observed in the Halls Creek Orogen. The results indicate that the geology of the Halls Creek Orogen is best represented by the ensialic marginal basin scenario. This scenario is most consistent with the observed geology and reveals processes which led to the generation of key lithological units and major structures. The numerical experiments can also explain sources of magmatism and development of metamorphic conditions that occurred during the tectonic evolution of the Halls Creek Orogen.