Geophysical evidence for a deep crustal root beneath the Yilgarn Craton and the Albany-Fraser Orogen

Abstract

Using a marine seismic reflection survey as a source for onshore and offshore seismic refkaction recorders, high quality refkaction data were recorded to a maximum offset of 400 km. A two-dimensional velocity model for Line 19 of Geoscience Australia survey 280 in the Bremer Sub-basin and its onshore extension was derived by forward modelling using iterative ray tracing. Our velocity model indicates the presence of a deep crustal root located under the southern margin of the Yilgam Craton and the Albany-Fraser Orogen. Comparison of the gravity response derived fkom this model with the gravity profile extracted fkom regional grids shows reasonable correlation. However, fine tuning of the seismic model is required to better define the complex geometry of the crustal root. Deep crustal roots are common under Proterozoic mobile belts that surround Archaean cratons. However, these results also indicate the presence of a crustal root under the southern margin of the Yilgam Craton. This is consistent with the view that Proterozoic taphrogenesis penetrated tens of kilometres into the Yilgam Craton.