The spatial distribution of igneous intrusions in the Exmouth Plateau and Exmouth Sub Basin, North West Shelf, Western Australia

The North West Shelf of Australia is a volcanic rifted margin. Jurassic-Cretaceous breakup of Gondwana resulted in the intrusion of significant volumes of igneous material into sediments of the Northern Carnarvon Basin. The last major review of the regional distribution of this intrusive material was published over 20 years ago. Since, there have been major advances in the understanding of intrusions in sedimentary basins, and step changes in the quality of 3D and reprocessed 2D seismic data available in Northern Carnarvon basin. 

We present preliminary findings of a new study building on these advances that investigates the regional spatial and temporal distribution of intrusions in the basin and the impact of this magmatism on petroleum systems. In this paper, we have mapped plumbing systems of intruded igneous complexes, interpreted on 3D surveys within the Exmouth Sub-basin, and on the Exmouth Plateau. 

Within the study area we see (1) typical ‘saucer shaped’, and ‘stepped’ intrusion geometries; (2) intrusions exploiting faults and cross cutting stratigraphy as they rise to the surface; (3) interconnected intrusions, forming continuous magmatic plumbing systems >50km in length; (4) intrusions mainly present within in the Triassic Mungaroo Formation, and (5) intrusions possibly sourced from a hotspot that was located beneath the current Cape Range Fracture Zone during breakup.