Geophysical and geochemical constraints on Cretaceous-Cenozoic magmatism along the southern Australian margin

Abstract

Increasing levels of exploration along rifted continental margins, such as the southern Australian margin, has led to growing recognition of the detrimental impacts of magmatic activity on hydrocarbon prospectivity. Key exploration risks include the impact of intrusions on seal integrity, reservoir quality, source rock maturation and migration pathways. However, the extent and distribution of volcanic rocks along continental margins, such as the Australian southern margin, and the processes by which magma is transported through sedimentary basins are still poorly understood despite the wealth of available seismic datasets. Although classified as a 'non-volcanic' rifted margin, our analysis shows that an extensive and largely undescribed record of Cretaceous-Cenozoic magmatic activity is preserved within the sedimentary successions of the rift basins located along the southern Australian margin. The combination of seismic reflection data and geochronological and geochemical data shows that this magmatic activity cannot be solely attributed to continental break-up and related decompressional melting processes or the presence of a hotspot or plume.