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.

This abstract discusses the metallogeny of the North Australian Craton and possible links to the assembly and breakup of Nuna, the Paleoproterozoic supercontinent. Before ~1750 Ma, deposits such as VHMS, porphyry Cu and orthomagmatic Cu-Ni deposits formed during the assembly of the NAC as the Kimberley, Numil-Abingdon and Aileron provinces converged and were then accreted onto the NAC. These deposits were formed in arc and backarcs, which generally involved local extension, within overall convergent geodynamic settings. After ~1750 Ma, the metallogeny changed, with deposits such as Broken Hill- and Mt Isa-type Zn-Pb-Ag deposits, unconformity U and iron oxide Cu-Au(U) deposits forming largely during extension associated with the breakup of Nuna.

Over the last fifteen years, Geoscience Australia, through its Onshore Energy Security Program, in conjunction with Primary Industries and Resources South Australia (PIRSA), the Geological Survey of New South Wales (Industry & Investment NSW), the Australian Geodynamics Cooperative Research Centre, and the Predictive Mineral Discovery Cooperative Research Centre (pmd*CRC), has acquired several deep seismic reflection profiles, which, when combined, form an east-west transect about 870 km long in southeastern Australia. The seismic data vary from low-fold, dynamite-source to higher-fold, vibroseis-source data. The combined seismic profiles, from the western Eyre Peninsula to the Darling Basin, provide a near complete cross-section of the crust across the Gawler Craton, Adelaide Rift System, Curnamona Province, Koonenberry Belt and Darling Basin. The entire region is dominated by east-dipping faults, some of which originated as basin-bounding extensional faults, but most appear also to have a thrust sense of movement overprinting the extension. In the Gawler Craton, an inferred shallow, thin-skinned thrust belt occurs to the west of an inferred thick-skinned thrust belt. The boundary between the two thrust belts, the Kalinjala Mylonite Zone, was active at least during the Kimban Orogeny, with possible extensional movement at that time. The thrust movement possibly occurred during the ~1600 Ma Olarian Orogeny.

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.

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.

The Georgina-Arunta deep seismic reflection line (09GA-GA1) has provided an image of the entire crust in this part of central Australia. At a first approximation, beneath the Neoproterozoic-Devonian sedimentary basins, the crust can be divided into four distinct regions, namely, the Aileron, Irindina and Davenport Provinces, and the Ooratippra Seismic Province. Each of these regions is separated from each other by major, crustal-scale faults. The observed crustal architecture has implications for geodynamic models for the evolution of the region, implying amalgamation of these crustal blocks in the Paleoproterozoic and major shortening and basin inversion in the Paleozoic.

Metallogenic, geologic and isotopic data indicate secular changes in the character of VHMS deposits relate to changes in tectonic processes, tectonic cycles, and changes in the hydrosphere and atmosphere. The distribution of these deposits is episodic, with peaks at 2740-2680 Ma, 1910-1840 Ma, 510-460 Ma and 370-355 Ma that correspond to the assembly of Kenorland, Nuna, Gondwana and Pangea. Quiescent periods of VHMS formation correspond to periods of supercontinent stability. Large ranges in source 238U/204Pb that characterize VHMS deposits in the Archean and Proterozoic indicate early (Hadean to Paleoarchean) differentiation. A progressive decrease in - variability suggests homogenisation with time of these differentiated sources. Secular increases in the amount of lead and decreases in 100Zn/(Zn+Pb) relate to an increase in felsic-dominated sequences as hosts to deposits and an absolute increase in the abundance of lead in the crust with time. The increase in sulfate minerals in VHMS deposits from virtually absent in the Meso- to Neoarchean to relatively common in the Phanerozoic relates to oxidation of the hydrosphere. Total sulfur in the oceans increased, resulting in an increasingly important contribution of seawater sulfur to VHMS ore fluids with time. Most sulfur in Archean to Paleoproterozoic deposits was derived by leaching rocks below deposits, with little contribution from seawater, resulting in uniform, near-zero-permil values of 34Ssulfide. In contrast the more variable values of younger deposits reflect the increasing importance of seawater sulfur. Unlike Meso- to Neoarchean deposits, Paleoarchean deposits contain abundant barite, which is inferred to have been derived from photolytic decomposition of atmospheric SO2 and does not reflect overall oxidised oceans. Archean and Proterozoic seawater was more salty than Phanerozoic, particularly upper Phanerozoic, seawater. VHMS fluids ore fluids reflect this, also being saltier in Precambrian deposits.

Increasingly, positioning applications in hazard assessment, mining, agriculture, construction, emergency, land, utility and asset management have a demonstrated need for centimetre level or better geodetic infrastructure. However, the geodetic infrastructure in the Asia-Pacific, when compared to other geographical regions, can be generally assessed as being sparse, inhomogeneous in accuracy, infrequently realised and difficult to access. Correspondingly, it has become increasingly clear that the Asia-Pacific infrastructure is below the standard that is now available in other regions, such as Europe and the Americas, and it represents a loss in competitive advantage. The Permanent Committee for GIS Infrastructure Asia-Pacific (PCGIAP) and the International Association of Geodesy (IAG) have made some progress in developing the Asia-Pacific geodetic infrastructure; however, it can still be characterised as being a work in progress. In this presentation, we review recent efforts to improve the region's geodetic infrastructure. Specifically, we focus on crustal deformation and show results from the Asia-Pacific component of the International Association of Geodesy (IAG) working group on regional velocity fields, which includes crustal velocity estimates for over 1200 stations. This velocity field incorporates solutions derived from Continuous GPS (CGPS) data, episodic campaign based data and also velocity-only information where precise coordinates are not available. Our combination method, including our approach of incorporating velocity-only information expressed in a variety of reference frames, such as plate-fixed frames, will be overviewed. Finally, we will review the key elements of the Asia-Pacific Reference Frame (APREF) initiative, which will create and maintain a modern regional geodetic framework based on continuous GNSS data.

Deep seismic reflection profiles have been acquired and interpreted to better understand the crustal architecture and geodynamic evolution of Australia's geological provinces. Here, we examine some of these profiles to better understand how the Australian continent formed in the Archean and Proterozoic. The 2007 deep seismic reflection survey in North Queensland imaged a major, west-dipping, Paleoproterozoic (or older) crustal boundary, which we interpret as a suture, separating relatively nonreflective, thick crust of the Mount Isa Province in the west from thinner, two layered crust to the east. This boundary is also imaged by magnetotelluric data and 3D inversions of aeromagnetic and gravity data. Farther to the northeast, a second major boundary dips west or southwest, offsetting the Moho and extending below it. It is interpreted as a fossil subduction zone, and is overlain by supracrustal rocks of the Etheridge Province, with ages of ~1720 Ma, which is interpreted as the minimum age of the suture. Seismic profiles in southeast Australia, collected between 1996 and 2009, were combined to provide a cross section of the crust across the Archean-Mesoproterozoic Gawler Craton, Neoproterozoic-Paleozoic Adelaide Rift System, Mesoproterozoic Curnamona Province, Neoproterozoic-Paleozoic Koonenberry Belt and Silurian-Devonian Darling Basin. The transect imaged at least four discrete seismic provinces in the middle to lower crust, all bounded by east-dipping, crustal-penetrating fault zones which extend to the Moho. As the seismic provinces have not been traced to the surface, age control is poor, but they are inferred to be older that the upper crustal rocks above them, most of which are Archean to Mesoproterozoic in age.

Geological regions with abnormally high endowment in metals appear to have resulted from the fortunate juxtaposition in space and time of numerous, possibly exceptional, processes. The Archean eastern Yilgarn Craton, Western Australia is such a region. The approach taken in this Special Issue is to consider the gold mineral system in the eastern Yilgarn Craton in terms of a series of integrated components, referred to by Price and Stoker (2002) and Barnicoat (2007) as the Five Questions: 1. What are the geodynamic and P-T histories of the system? 2. What is the architecture of the system? 3. What are the fluid reservoirs? 4. What are the fluid flow drivers and pathways? 5. What are the metal and sulphur transport and depositional processes? In order to better understand these components and the geological processes which define them, a range of scales needs to be considered. At each scale, however, the relative benefits of considering any one of the five components are varied. For example at the terrane scale, an analysis of the geodynamics and architecture provides most insight, whereas an analysis of deposition mechanisms is best conducted at a deposit scale. This Special Issue focuses specifically on the first two questions, in order to provide a greater understanding of the geodynamic and architectural processes which have contributed to the elevated endowment of gold in the eastern Yilgarn Craton. The papers in this Special Issue reports some of the results produced by the Predictive Mineral Discovery Cooperative Research Centre (pmd*CRC, www.pmdcrc.com.au), a research centre funded for seven years by the Australian Government, universities and mineral exploration industry partners.