Low-temperature thermal history of the McArthur Basin: Influence of the Cambrian Kalkarindji Large Igneous Province on hydrocarbon maturation

The McArthur Basin of the North Australian Craton is one of the very few places on Earth where extensive hydrocarbons are preserved that were generated from Mesoproterozoic source rocks, prior to the development of extensive multicellular life. It is, however, unclear precisely when hydrocarbons from these source rocks matured, and if this occurred as a singular event or multiple phases. In this study, we present new apatite fission track data from a combination of outcrop and sub-surface samples from the McArthur Basin to investigate the post-depositional thermal history of the basin, and to explore the timing of hydrocarbon maturation. Apatite fission track data and thermal modelling suggest that the McArthur Basin experienced a basin-wide reheating event contemporaneous with the eruption of the Cambrian Kalkarindji Large Igneous Province in the North and West Australian cratons, during which thick (>500 m) basaltic flows blanketed the basin surface. Reheating at ca. 510 Ma coinciding with Kalkarindji volcanism is consistent with a proposed timing of elevated hydrocarbon maturation, particularly in the Beetaloo Sub-basin, and provides a mechanism for petroleum generation throughout the basin. Subsequent regional cooling was slow and gradual, most likely facilitated by gentle erosion (ca. 0.01-0.006 km/Ma) of overlying Georgina Basin sediments in the Devonian-Carboniferous with little structural reactivation. This model provides a framework in which hydrocarbons, sourced from Mesoproterozoic carbon-rich rocks, may have experienced thermal maturation much later in the Cambrian. Preservation of these hydrocarbons was aided by a lack of widespread structural exhumation following this event.