Abstract. In an effort to improve our understanding of southeast Australia’s enigmatic tectonic evolution, we analyse teleseismic earthquakes recorded by 24 temporary and 8 permanent broadband stations using the receiver function method. Crustal thickness, bulk seismic velocity and internal crustal structure of the southern Tasmanides – an assemblage of Palaeozoic accretionary orogens that occupy eastern Australia – are constrained by our new results which point to: (1) a 39.0 ± 0.5 km thick crust, a relatively high Poisson’s ratio (0.262 ± 0.014) and a broad (> 10 km) crust-mantle transition beneath the Lachlan Fold Belt. This is interpreted to represent magmatic underplating of mafic materials at the base of the crust; (2) a complex crustal structure beneath VanDieland, a postulated Precambrian continental fragment embedded in the southernmost Tasmanides, where the crust thickens (37.5 ± 1.2 km) towards the northern tip of the microcontinent as it enters south central Victoria but thins south into Bass Strait (30.5 ± 2.1 km), before once again becoming thicker beneath western Tasmania (33.5 ± 1.9 km). The thinner crust beneath Bass Strait can be attributed to lithospheric stretching that resulted from the break-up of Antarctica and Australia and the opening of the Tasman Sea; (3) stations located in the East Tasmania Terrane and eastern Bass Strait (ETT+EB) collectively indicate crust of uniform thickness (∼ 33 km) and a slightly broad Moho transition that reflect a possible underplating event associated with a Palaeozoic subduction system. The relative uniformity of Vp/Vs and Poisson’s ratio in VanDieland – suggesting uniformity in composition – could be used in support of the VanDieland microcontinental model that explains the tectonic evolution of southeast Australia.
POSSIBLE INTRUSION-RELATED GOLD SYSTEMS INTHE WESTERN LACHLAN OROGEN, SOUTHEAST AUSTRALIA