The Geocentric Datum of Australia 1994 (GDA94) is a static coordinate datum realised with respect to the International Terrestrial Reference Frame (ITRF) at the reference epoch of 1 January 1994. At this time GDA94 and ITRF were coincident, however, as a consequence of the tectonic motion of the rigid Australian plate, ongoing refinement of the ITRF, and crustal deformation, the two reference frames have diverged, and the absolute difference between them is now approximately 1 m. Consequently, precise coordinate transformations between ITRF and GDA94 are required for many applications within the Australian spatial community, and in this study we review, improve and extend these transformations. We have computed new Helmert transformation parameters between ITRF and GDA94, including the specific ITRF realisations of ITRF1996, ITRF1997, ITRF2005 and ITRF2008. For the ITRF2005 and ITRF2008 cases these are the first available results. After transformation, we find ITRF based network solutions have residual coordinate differences with respect to GDA94 that are typically less than 10 and 30 mm in the horizontal and vertical components, respectively. However, maximum residuals can exceed 15 and 70 mm in the horizontal and vertical components, respectively, which highlights a limitation of GDA94 for many precise applications. Finally, we discuss implications and future strategies for managing the differences between GDA94 and ITRF, including novel coordinate transformation approaches, satellite trajectory transformations, and also options for the modernisation of the Australian geodetic datum.

As part of initiatives by the Australian and Queensland Governments to support energy security and mineral exploration, a deep seismic reflection survey was conducted in 2007 to establish the architecture and geodynamic framework of north Queensland. With additional support from AuScope, nearly 1400 km of seismic data were acquired along four lines, extending from near Cloncurry in the west to almost the Queensland coast. Important results based on the interpretation of the deep seismic data include: (1) A major, west-dipping, Paleo-proterozoic (or older) crustal boundary, which we interpret as a suture, separates relatively homogenous, thick crust of the Mt Isa Province from thinner, two layered crust to the east. This boundary is also imaged by magnetotelluric data and 3D inversion of aeromagnetic and gravity data. (2) East of the Mt Isa Province the lower crust is highly reflective and has been subdivided into three mappable seismic provinces (Numil, Abingdon and Agwamin) which are not exposed at the surface. Nd model ages from granites sampled at the surface above the western Numil and central Abingdon Seismic Provinces have very similar Nd model ages, suggesting that both provinces may have had a very similar geological history. By contrast, granites sampled above the eastern Agwamin Seismic Province have much younger Nd model ages, implying a significantly younger component in the lower crust; we consider that the Agwamin Seismic Province contains a strong Grenvillean-age component.

Six deep seismic reflection profiles totalling ~900 km were acquired across the Mount Isa Province in 2006 (Figure 1). Each vibe point was recorded to ~20 s TWT (two-way travel time), which equates to ~60 km depth. The aims of the survey were to develop a 3D model and a geodynamic history of the province, link deep crustal structure with known mineral deposits, and demonstrate the potential of deep seismic surveys in mineral exploration

Beginning in the Archean, the continent of Australia evolved to its present configuration through the accretion and assembly of several smaller continental blocks and terranes at its edges. Australia grew usually by convergent plate margin processes, such as arc-continent collision, continent-continent collision or through accretionary processes at subduction zones. The accretion of several island arcs to the Australian continent, through arc-continent collisions, played an important role in this process, and the geodynamic implications of some Archean and Proterozoic island arcs recognised in Australia will be discussed here.

Summary of forward gravity and flexure modelling of the New Caledonia Trough to highlight temporal variations in lithospheric rigidity during its evolution.

As part of the Australian Government's Onshore Energy Security Program and the Queensland Government's Smart Mining and Smart Exploration initiatives, deep seismic reflection surveys (~2300 line km) were conducted in North Queensland to establish the architecture and geodynamic framework of this area in 2006 (Mt Isa Survey; also involving OZ Minerals and pmd*CRC) and 2007 (Cloncurry-Georgetown-Charters Towers Survey; also involving AuScope). The purpose here is to use new geodynamic insights inferred from the seismic and other data to provide comments on the large-scale geodynamic controls on energy and other mineral potential in North Queensland.

Tholeiitic intrusion-hosted nickel sulphide deposits are highly sort exploration targets due to their potential size and co-products platinum-group elements and copper. The Norilsk-Talnakh (Russia), Voisey's Bay (Canada) and Jinchuan (China) deposits are world class examples. Although Australia holds the largest economic resources of nickel in the world, its nickel resources are mainly sourced from komatiitic-hosted and lateritic deposits. Known resources of tholeiitic intrusion-hosted nickel sulphides are relatively small, with Nebo-Babel and Nova-Bollinger in Western Australia the most significant examples. Given the abundance of tholeiitic igneous rocks in Australia, this important deposit type seems to be under-represented when compared to other continents with similar geology. To support the discovery of world class nickel sulphide deposits in Australia, Geoscience Australia has recently undertaken a continental-scale GIS-based prospectivity analysis for tholeiitic intrusion-hosted deposits across Australia. This analysis exploits a suite of new relevant digital datasets recently released by Geoscience Australia. For example, the analysis utilises the Australian Mafic-Ultramafic Magmatic Events GIS Dataset which places mafic and ultramafic rocks across Australia into 74 coeval magmatic events based on geochronological data. Whole rock geochemistry of mafic and ultramafic rocks has been used to differentiate between magma series and discriminate between different magmatic events and units within those events. Other new datasets include crustal domain boundaries derived from both deep crustal seismic data and neodymium depleted mantle model age data as well as a coverage of the minimum thickness of mafic rocks in the crust derived from the Australian Seismogenic Reference Earth Model. This continental-scale GIS-based nickel sulphide prospectivity analysis uses a mineral systems approach to map the four essential components of ore-forming mineral systems; (1) sources of ore constituents, (2) crustal and mantle lithospheric architecture, (3) energy sources or drivers of the ore-forming system, and (4) gradients in ore depositional physico-chemical parameters. These four components are combined into a prospectivity map using weights-of-evidence GIS-based techniques, with the most prospective areas across the continent occurring where all components are present. The mineral systems approach allows for the identification of a much larger footprint than the deposit itself, and can be applied to greenfield and/or undercover areas. The results highlight areas that contain known tholeiitic intrusion-hosted nickel sulphide deposits, such as the Musgrave and Pilbara Provinces, as well as regions that do not contain any known deposits, such as the southern margin of the Arunta Province in the Northern Territory, the Mount Isa Province in Queensland and the Paterson Province in Western Australia.

One of the main outputs of the Earthquake Hazard project at Geoscience Australia is the national earthquake hazard map. The map is one of the key components of Australia's earthquake loading standard, AS1170.4. One of the important inputs to the map is the rate at which earthquakes occur in various parts of the continent. This is a function of the strain rate, or the rate of deformation, currently being experienced in different parts of Australia. This paper presents two contrasting methods of estimating the strain rate, and thus the seismicity, using the latest results from the seismology and geodynamic modelling programs within the project. The first method is based on a fairly traditional statistical analysis of an updated catalogue of Australian earthquakes. Strain rates, where measurable, were in the range of 10-16s-1 to around 10-18s-1 and were highly variable across the continent. By contrast, the second method uses a geodynamic numerical model of the Australian plate to determine its rate of deformation. This model predicted a somewhat more uniform strain rate of around 10-17s-1 across the continent. The uniformity of the true distribution of long term strain rate in Australia is likely to be somewhere between these two extremes but is probably of about this magnitude. In addition, this presentation will also give an overview of how this kind of work could be incorporated into future versions of the national earthquake hazard map in both the short and long term.

As part of initiatives by the Australian and Queensland Governments to support energy security and mineral exploration, a deep seismic reflection and magnetotelluric survey was conducted in 2007 to establish the architecture and geodynamic framework of north Queensland. With additional support from AuScope, nearly 1400 km of seismic data were acquired along four lines, extending from near Cloncurry in the west to almost the Queensland coast.

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.