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.

Over the last decade there have been significant advances in our understanding of the: stratigraphy; magmatism; deformation; metamorphism; and timing of mineralisation, in the Eastern Goldfields Superterrane (EGST) of Yilgarn Craton, WA. The integration of these disciplines has enabled a holistic review of the tectonic history of the EGST, thereby providing a para-autochthonous geodynamic context for its mineralisation. A significant advance has been the recognition of a ~2.81 Ga rifting event off the eastern margin of the Youanmi Terrane which set up the north-northwest trending architecture of the EGST, as expressed in the Nd TDM map. Rifting was followed by the establishment of a convergent margin characterised by a west dipping subduction zone to the east of the EGST. Subduction resulted in the deposition of the 2.715-2.67 Ga volcanic stratigraphy and the emplacement of voluminous TTG magmatism, which resulted in magmatic thickening of the crust. Volcanism was terminated by a ~5 Ma pulse of east-northeast contraction which triggering lithospheric and lower crustal delamination associated with mid-orogenic extension. The lack of ultra-high pressure metamorphism and the presence of high geothermal gradients preclude this event from recording a continent-continent collision. Mid-orogenic extension initiated at 2.665 Ga resulted in the introduction of metasomatised mantle melts (Mafic-granites and Syenites), deposition of late-stage siliciclastic basins (which record anticlockwise PTt paths) and the start of significant economic gold mineralisation in the EGST. The delamination associated with this event resulted in significant heat input into the base of the crust, which eventually led to the emplacement of Low-Ca (crustal melt) granites and cratonisation of the EGST.

A deep seismic reflection and magnetotelluric survey, conducted in 2007, established the architecture and geodynamic framework of north Queensland, Australia. Results based on the interpretation of the deep seismic data include the discovery of a major, west-dipping, Paleoproterozoic (or older) crustal boundary, interpreted the Gidyea Suture Zone, separating relatively nonreflective, thick crust of the Mount Isa Province from thinner, two layered crust to the east. East of the Mount Isa Province, the lower crust is highly reflective and is subdivided into three mappable seismic provinces (Numil, Abingdon and Agwamin) which are not exposed at the surface. To the west of Croydon, a second major crustal boundary also dips west or southwest, offsetting the Moho and extending below it. It is interpreted as the Rowe Fossil Subduction Zone. This marks the boundary between the Numil and Abingdon seismic provinces, and is overlain by the Etheridge Province. The previously unknown Millungera Basin was imaged below the Eromanga-Carpentaria basin system. In the east, the Greenvale and Charters Towers Provinces, part of the Thomson Orogen, have been mapped on the surface as two discrete provinces, but the seismic interpretation raises the possibility that these two provinces are continuous in the subsurface, and also extend northwards to beneath the Hodgkinson Province, originally forming part of an extensive Neoproterozoic-Cambrian passive margin. Continuation of this passive margin at depth beneath the Hodgkinson and Broken River Provinces suggests that these provinces (which formed in an oceanic environment, possibly as an accretionary wedge at a convergent margin) have been thrust westwards onto the older continental passive margin. The Tasman Line, originally defined to represent the eastern limit of Precambrian rocks in Australia, has a complicated geometry in three dimensions, which is related to regional deformational events during the Paleozoic.

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.

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

We compare GPS derived geodetic strain rates with estimates from seismic moment release for the Western Australian Seismic Zone. The geodetic strain rates were derived from occupations, in 2002 and 2006, of a 48 site regional network in the SW corner of Australia. The high precision nature of the experiment enabled us to identify 16 sites where antenna errors were the cause of the anomalous displacements. The cause of this is considered to be due to errors in the phase centre of three antennas. The ~1200 km2 study area is one of the most seismically active areas of mid-continental crust worldwide. The geodetic and seismic derived compressional strain-rates are 0.8±0.8 x10-9 yr-1 and 4.9 ±1.9 x10-9 yr-1 (±1) respectively. In effect, the geodetic strain rate would appear to be significantly less than the seismic rate which is amongst the highest of all mid-continental crust rates. With over 95% confidence we can exclude the geodetic and seismic strain rates being the same. This suggests that the contemporary seismic moment release it significantly higher than the long-term moment release. Thus the seismicity of this region is possibly not following the Poissonian behaviour normally observed for inter-plate earthquakes and may be episodic. Thus estimates of the long-term seismic hazard in this area based solely on the earthquake data are likely to be overestimates. Whether the geodetic stain rate reflects the Australian continental average or an intermediate value will require several repeat occupations.

In July 2009, Geoscience Australia initiated a new project within the Geospatial and Earth Monitoring Group to update the national earthquake hazard map using current methods and data. The map is a key component of Australia's earthquake loading code. As part of developing the project, between the 20th and 22nd of October 2009 Geoscience Australia hosted a workshop with Australian experts in seismic hazard assessment. The aim of the workshop was to scope out the short and long term direction of the earthquake hazard project and the national map. This report was developed from the input and advice received from that workshop.

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.

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

This report presents the results of a geodynamic synthesis of South Australia, focusing predominantly on the Archean to Mesoproterozoic of the Gawler Craton and Curnamona Province in terms of geodynamic setting, architecture, and age, using results of a geological synthesis, seismic interpretation, sequence stratigraphy, geochronology and geochemistry. This was undertaken with the dual aims: 1. To better understand the tectonic and geodynamic setting of the Gawler Craton and Curnamona Province 2. To accompany the interpretation of recently-acquired seismic reflection transects (see related product below), and to highlight new geochemical and geochronological data collected from South Australia.