Although there is general agreement that the western two-thirds of Australia was assembled from disparate blocks during the Proterozoic, the details of this assembly are difficult to resolve, mainly due to ambiguous and often conflicting data sets. Many types of ore deposits form and are preserved in specific geodynamic environments. For example, porphyry-epithermal, volcanic-hosted massive sulfide (VHMS), and lode gold deposits are mostly associated with convergent margins. The spatial and temporal distributions of these and other deposits in Proterozoic Australia may provide another additional constraints on the geodynamic assembly of Proterozoic Australia. For example, the distribution of 1805-1765 Ma lode gold and VHMS deposits in the North Australian Element, one of the major building block of Proterozoic Australia, supports previous interpretations of a convergent margin to the south, and is consistent with the distribution of granites with subduction-like signatures. These results imply significant separation between the North and South Australian elements before and during this period. Similarly, the distribution of deposits in the Halls Creek Orogen is compatible with convergence between the Kimberly and Tanami provinces at 1865-1840 Ma, and the characteristics of the deposits in the Mount Isa and Georgetown provinces are most compatible with extension at 1700-1650 Ma, either in a back-arc basin or as a consequence of the break-up of Nuna.

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.

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

The western two-thirds of Australia is underlain by Precambrian rocks that are divisible into three Archean to Paleoproterozoic cratons, the West Australian, North Australian and South Australian cratons, separated by Paleoproterozoic to Mesoproterozoic orogens. The temporal and spatial record of Proterozoic rock units and orogenic events documents accretion and assembly of Precambrian, proto-Australia. The Archean Yilgarn and Pilbara cratons were assembled into the West Australian Craton along the Capricorn Orogen during the late Paleoproterozoic (2000 Ma) Glenburgh Orogeny, which then combined with the North Australian Craton along the Rudall Orogen during the 1800-1765 Ma, Yapungku Orogeny. Prior to about 1500 Ma the North and South Australian cratons show a similar geological history and are herein assumed to have evolved as a single entity, termed the North-South Australian Craton. It was bounded throughout most of the late Paleoproterozoic to earliest Mesoproterozoic by subduction zones along its south western and north eastern margins such that much of the craton occupied an upper plate, back arc basin environment. After ~1500 Ma the craton differentiated into the North Australian and South Australian cratons through rotation and lateral translation of the latter, resulting in convergence and collisional suturing with the West Australian craton along the 1345-1140 Ma Albany-Fraser Orogen. The Pinjarra Orogen developed along the margin of the West Australian Craton and records late Mesoproterozoic to Neoproterozoic strike-slip juxtaposition of India within an assembling Gondwana. The Neoproterozoic record of the Terra Australis Orogen, which extends along the eastern side of Precambrian Australia, records rifting and continental breakup within the supercontinent of Rodinia. Australian Proterozoic rocks host significant mineral resources, including world class banded iron-formations in the West Australian craton (Hamersley), and iron oxide copper gold deposits (Olympic Dam), Pb-Zn-Ag systems (Mount Isa and Broken Hill) and uranium deposits in the North-South Australian Craton.

We use seismic-reflection and rock-sample data to propose that the first-order physiography of New Caledonia Trough and Norfolk Ridge formed in Eocene to Miocene time, and was associated with the onset of subduction and back-arc spreading at the Australia-Pacific plate boundary. Our tectonic model involves an initial Cretaceous rift that is strongly modified by Cenozoic subduction initiation and hence we are able to explain: complex sedimentary basins of inferred Mesozoic age; a prominent unconformity and onlap surface of Middle Eocene to Early Miocene age at the base of flat-lying sediments beneath the axis of New Caledonia Trough; gently-dipping, variable thickness, and locally deformed Late Cretaceous strata along the margins of the trough; platform morphology and unconformities on either side of the trough that indicate a phase of Late Eocene to Early Miocene uplift to near sea level, followed by rapid Oligocene and Miocene subsidence of c. 1100-1800 m; and seismic-reflection facies tied to boreholes that suggest absolute tectonic subsidence at the southern end of New Caledonia Trough by 1800-2200 m since Eocene time. The Cenozoic part of the model involves delamination and subduction initiation followed by rapid foundering and rollback of the slab. This created a deep (>2 km) enclosed oceanic trough c. 2000 km long and 200-300 km across in Eocene and Oligocene time as the lower crust detached, with simultaneous uplift and local land development along basin flanks. Disruption of Late Cretaceous and Paleogene strata was minimal during this Cenozoic phase and involved only subtle tilting and local reverse faulting or folding. Basin formation was possible through the action of at least one detachment fault that allowed the lower crust to either be subducted into the mantle or exhumed eastward into Norfolk Basin. We suggest that delamination of the lithosphere, with possible mixing of the lower crust back into the mantle, is more widespread than previously thought.

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.

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.

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.

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.

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 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). Nearly 2300 line km of seismic data were acquired during these surveys. Geochemical, geochronological and complementary geophysical studies were undertaken in support of the seismic acquisition. Overviews of the geology of North Queensland and more detailed descriptions and the results of these surveys are presented in Hutton et al. (2009a, b), Korsch et al. (2009a), Withnall et al. (2009a, b), Henderson and Withnall (2009), and Henderson et al. (2009). The purpose here is to use the new geodynamic insights inferred from these data to provide comments on the large-scale geodynamic controls on energy and other mineral potential in North Queensland. This contribution draws on geodynamic and metallogenic overviews presented by Korsch et al. (2009b) and Huston et al. (2009)