The Capricorn Orogen in Western Australia records the punctuated Proterozoic assembly of the Pilbara and Yilgarn Cratons to form the West Australian Craton, and over one billion years of subsequent intracratonic reworking and basin formation. The orogen is over 1000 km long, and includes the passive margin deposits of both the Pilbara and Yilgarn Cratons, variably deformed and metamorphosed granitic and metasedimentary rocks of the Gascoyne Province, and very low- to low-grade metasedimentary rocks that overly these three tectonic units. Several mineral systems have been recognized in the orogen, including the world-class hematite iron-ore deposits of the Hamersley Basin. Other deposits include volcanic-hosted metal sulphide (VHMS) copper-gold deposits, orogenic lode-gold mineralization, various intrusion- and shear zone related base metal, tungsten, rare earth element, uranium and rare-metal deposits, and sediment hosted lead-copper-zinc mineralization. A recent 581 km long vibroseis-source, deep crustal seismic survey across the Capricon Orogen, has provided critical information on the architecture and geological evolution of the orogen. The transect has identified several distinct crustal terranes, each separated by moderately south-dipping suture zones, as well as other major structures that cut through the crust to the mantle. This improved understanding of the Capricorn Orogen has shown that many of the mineral occurrences within the orogen are spatially associated with these crustal-scale structures, which appear to have concentrated fluids, energy, and metals into specific sites in the Capricorn Orogen crust.

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.

Collation of extended abstracts presented at the pmd*CRC conference 11-12 June 2008

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.

Palaeoproterozoic to Mesoproterozoic Geology of North Queensland IW Withnall1, NL Neumann2 & A Lambeck2 1 Geological Survey of Queensland, Department of Employment, Economic Development and Innovation 2 Geoscience Australia The Palaeoproterozoic to Mesoproterozoic rocks of north Queensland that crop out in the Georgetown, Yambo and Coen Inliers (Figure 1) are the most easterly rocks of this age in Australia. They are important to an understanding of the evolution of the continent and possible configurations of Rodinia. Most models for the evolution of the North Australian Craton assume Georgetown and the other inliers to be a part of it, although usually have given little thought to how they might fit in the model.

New geochronological data combined with existing data suggest that the Neoproterozoic period in Australia was reasonably well mineralised, with two major periods of mineralisation: (1) 850-800 Ma sediment-hosted Cu, unconformity U, and diamond deposits, and (2) 650-630 Ma epigenetic Au-Cu deposits. The early period appears to be associated with extension related to initiation of Rodinia break-up, whereas the geodynamic setting of the latter, more restricted, event is unclear.

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.

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