Magnetotellurics and Geomagnetic Depth Sounding in Queensland, South Eastern Australia -Evidence for the Tasman Line?

Abstract

The Tasman Line in eastern Australia is commonly defined as the locus of Rodinia- Gondwana breakup. It is a much discussed concept in the geology and tectonics of eastern Australia. However, the concept of the Tasman Line before now remains contentious and inconclusive. Most previous geophysical methods (e.g. magnetic and gravity anomalies) used to delineate the Tasman Line lie in the crust, but geophysical evidence for a contrast associated with Precambrian rocks to the west and Phanerozoic ones to the east is not limited to the crust. We have used eletromagnetic induction methods (magnetotellurics (MT) and geomagnetic depth sounding (GDS) and shown that the anomaly that marks the Tasman Line in Queensland extends to at least 90 km from the crust into the mantle. We combined information from phase analysis, strike angles (MT and GDS strikes), induction vectors and GDS perturbation tensors and located the Tasman Line at longitude (142.5±0.5)◦ E in Queensland. We interpreted and attributed the anomalous conductivity along the Tasman Line to collisional processes and to metal sediments produced during rifting and buried during rift closure.