Interpretation of deep seismic reflection profiling coupled with forward modelling of gravity and aeromagnetic data, new zircon U-Pb age dating and the interpretation of the basement geology beneath the southern margin of the Eromanga Basin has provided insights into the southern part of the underlying Thomson Orogen and its relationship with the Lachlan Orogen to the south. Our interpretations of these data suggest that the northern Lachlan and southern Thomson orogens possessed a similar history from the mid-Late Silurian through to the Carboniferous. Major older differences, however, are suggested by the presence in the southern Thomson Orogen of relics of a possible Neoproterozoic arc, of Late Ordovician turbidites, by the geophysical evidence for crustal thickening caused by elevation of reflective lower crustal metavolcanic rocks high into the crust on a low-angle, north-dipping detachment thrust, and by old K-Ar age dates in southwestern Queensland. The seismically-imaged, north-dipping, crustal-scale Olepoloko Fault corresponds to the surface expression of Thomson-Lachlan boundary, and reflects the dip-slip and strike-slip partial reactivation and short-cutting of an older fault, which occurred in the Carboniferous, and probably also in the latest Silurian and Early Devonian.

The Asia-Pacific Reference Frame (APREF) project is an initiative that recognizes the importance of improving the regional geodetic framework in the Asia-Pacific region. A substantial number of state-of-the-art GNSS networks, operated by national mapping agencies and private sector organizations, are available in the region. In the APREF initiative these networks are combined to realize a high-standard regional reference frame. The GNSS data of the network are processed by different Analysis Centres (ACs). The contributions of the different ACs are combined into a weekly solution by the APREF Central Bureau. This weekly solution is the core product of the APREF; it contains weekly estimates of the coordinates of the participating Asia-Pacific GNSS tracking stations and their covariance information. The APREF products, which have been available since the first quarter of 2010, gives a reliable time-series of a regional reference frame in the International Terrestrial Reference Frame and a quality assessment of the performance of the GNSS CORS stations included in the network. This contribution gives an overview of the current status of the APREF network and an analysis of the first APREF products.

We have used data recorded by a temporary seismograph deployment to infer constraints on the state of crustal stress in the Flinders Ranges in south-central Australia. Previous stress estimates for the region have been poorly constrained due to the lack of large events and limited station coverage for focal mechanisms. New data allowed 65 events with 544 first motions to be used in a stress inversion to estimate the principal stress directions and stress ratio.While our initial inversion suggested that stress in the region was not homogeneous, we found that discarding data for events in the top 2km of the crust resulted in a well-constrained stress orientation that is consistent with the assumption of homogeneous stress throughout the Flinders Ranges. We speculate that the need to screen out shallow events may be due to the presence in the shallow crust of either: (1) small-scale velocity heterogeneity that would bias the ray parameter estimates, or (2) heterogeneity in the stress field itself, possibly due to the influence of the relatively pronounced topographic relief. The stress derived from earthquakes in the Flinders Ranges show an oblique reverse faulting stress regime, which contrasts with the pure thrust and pure strike slip regimes suggested by earlier studies. However, the roughly E-W direction of maximum horizontal compressive stress we obtain supports the conclusion of virtually all previous studies that the Flinders Ranges are undergoing E-W compression due to orogenic events at the boundaries of the Australian and Indian Plates.

The rifting history of the magma-poor conjugate margins of Australia (Great Australian Bight) and Antarctica (Terre Adélie) is still a controversial issue. In this paper, we present a model for lithosphere-scale rifting and deformation history from initial rifting to breakup, based on the interpretation of two regional conjugate seismic profiles of the margins, and the construction of a lithosphere-scale, balanced cross section, sequentially restored through time. The model scenario highlights the symmetric pattern of initial stretching resulting to pure shear at lithospheric-scale accompanied by the development of four conjugate detachments and crustal half-graben systems. This system progressively evolves to completely asymmetric shearing along a single south-dipping detachment at the scale of the lithosphere. The detachment accounts for the exhumation of the mantle part of the Australian lithosphere, and the isolation of a crustal klippe separated from the margin by a peridotite ridge. Antarctica plays the role of the upper plate with the formation of an external crustal high separated from the unstretched continental crust by a highly extended zone still active during the Australian exhumation phase. The total elongation amount of the Australian-Antarctic conjugate system reaches ~413km (61%). Elongation was partitioned through time: ~189km and ~224km during symmetric and asymmetric stages, respectively. During symmetric stage, both margins suffered relatively the same elongation accommodated by crustal stretching (~105km (45%) and ~84km (38%) for Australia and Antarctica, respectively). Again, both margins accommodated relatively the same elongation during the asymmetric stage: the Antarctic upper plate records an elongation amount of ~225km (40%) as crustal tectonic stretching, above the inferred low-angle south dipping detachment zone, whereas the Australian lower plate suffered ~206km (61%) of elongation through mantle exhumation.

This article presents the results of studies in North Queensland associated with the 2007 Mt Isa-Georgetown-Charters Towers seismic survey. Results include seismic interpretation, geophysical studies and 3D maps, tectonic and metallogenic syntheses and energy potential assessment.

As part of initiatives by the Australian and Queensland Governments, four new seismic reflection lines and three corresponding magnetotelluric lines were acquired in 2007 over the Mt Isa, Georgetown and Charters Towers regions. These data, combined with existing multidisciplinary data, have provided new insights into the 3D architecture, geodynamics and economic potential of the North Queensland region.

Interpretation of the 2006 deep seismic reflection data across the western Lachlan Orogen of southeast Australia have provided important insights into crustal-scale fluid pathways and possible source rocks in the Victorian orogenic gold province. The seismic profiles span three of the most productive structural zones in Victoria: the Stawell, Bendigo and Melbourne zones. Variations in the age and style of gold deposits across the structural zones are reflected by changes in crustal structure and composition, as revealed by the seismic data.

The secular distribution of zinc deposits is pulsed and related to changes in Earth processes and conditions, including the supercontinent cycle and oxygenation of the atmosphere and hydrosphere. Deposits hosted by volcanic successions formed during the assembly of supercontinents along convergent margins, probably as the consequence of high heat flow and a greater likelihood that such tectonic systems are preserved. Siliciclastic-hosted and carbonate-hosted deposits post-date the first oxygenation event as fluids that formed these deposits were oxidized. Siliciclastic-hosted deposits formed both during assembly and breakup of supercontinents, whereas carbonate-hosted deposits formed during supercontinent or microplate assembly.

Extended abstract of metalogenic implications of seismic and allied results in North Queensland

The Tasman Orogen represents a long-lived accretionary orogen with numerous orogenic cycles of extension and subsequent orogeny. Although details of the orogen are controversial, it is evident that the present configuration represents the cumulate products of many orogenies including both accretion and significant rearrangement of terranes. As a result the Tasman Orogen plays host to a significant array of commodities within a myriad of deposit styles, related to a variety of tectonic regimes. It is also evident that many mineralisation styles are repeated through the different orogenic cycles, and commonly during the same parts of the orogenic cycle. For example, volcanic-hosted massive sulphide deposits form early in cycles, whereas lode gold deposits form during contractional orogenesis that terminates the cycle. The geological complexity is both an advantage and disadvantage. Although the complexity can hinder regional exploration, it offers significant potential for identifying regions where previously unrecognised mineralisation styles may be present, particularly under cover where the geology (and tectonic history) is less well constrained.