The Delamerian NDI: Linking South and eastern Australia.

The western Murray Basin obscures the interpreted transition between Proterozoic and Phanerozoic rocks of Australia in the upper crust, often referred to as the Tasman Line. The South Australian part of this continental margin has been interpreted, based on sparse extrapolated constraints, to have sat in various geodynamic settings associated with a Cambrian subduction system. We use newly acquired multi-disciplinary datasets and the results of the MinEx CRC Delamerian National Drilling Initiative program to elucidate the architecture of this hidden Cambrian margin, revealing unrecognised potential for a spectrum of mineral systems. Whilst it has been accepted for a number of years that the Stavely Zone in western Victoria represents a volcanic arc in the mid-Cambrian, continent-ward belts to the west (beneath the Murray Basin), have had uncertain affinities. With the results of recent drilling, we show that both regional, and highly partitioned back-arc extension were present in the period 515-500 Ma, and speculate that inherited structure in pre-Cambrian basement rocks are responsible for the variation in deformation styles present in drill core.