The New England Orogen contains a geological record dominated by subduction-related rocks, indicating that the orogen has been part of, or adjacent to, convergent plate margins of eastern Gondwanaland from at least the Cambrian until the end of the Early Cretaceous (~95 Ma). In the late Devonian, the orogen records the change from an island arc setting to an Andean-style convergent continental plate margin (e.g., Flood & Aitchison 1992; Skilbeck and Cawood, 1994). The rock record prior to the Middle Devonian is fragmentary, but the Late Devonian to Carboniferous components of the continental margin magmatic arc, forearc basin and accretionary wedge system are well preserved in the New England Orogen, with the Lachlan Orogen, Thomson Orogen and Drummond Basin to the west being in a backarc setting at this time. This system ended in the Late Carboniferous, with the subduction zone stepping to the east (Cawood, 1984). Nevertheless, until at least the Early Cretaceous, the Australian component of the continental margin of East Gondwanaland faced the Proto-Pacific (Panthalassan) Ocean, and has been interpreted to form part of a subduction-related convergent plate margin (e.g. Powell 1984; Cawood 2005; Glen 2005). Here, we examine aspects of the southern New England Orogen from the Cambrian to the Early Permian to further document the nature of the convergent plate margin over this period of time. We are interested especially in the Tamworth Belt, where the changeover is recorded from the Cambrian-Late Devonian island arc setting, to the development of the Devonian-Carboniferous continental margin in a convergent plate setting, with its well developed forearc basin and accretionary wedge. The island arc component is referred to as the Gamilaroi Terrane by Aitchison and Flood (1995) and Offler and Gamble (2002).

Aspects of the tectonic history of Paleo- to Mesoproterozoic Australia are recorded by metasedimentary basins in the Mt Isa, Etheridge Provinces, and Coen Inlier in northern Australia and in the Curnamona Province of southern Australia. These deformed and metamorphosed basins are interpreted to have been deposited in a tectonically-linked system based on similarities in depositional ages and stratigraphy (Giles at al 2002). Neodymium isotope compositions of sediments and felsic volcanics, when combined with U-Pb geochronology, are independent data that are important tools for inferring tectonic setting, palaeogeography and sediment provenance in deformed and metamorphosed terrains.

This is a collection of conference program and abstracts presented at AOGC 2010, Canberra.

In this paper, we present a high resolution study focussed mainly on the Gorgon field and associated Rankin Trend gas fields, Carnarvon Basin, Australia (Figure 1). These gas fields are characterized by numerous stacked reservoirs with varying CO2 contents and provide a relevant natural laboratory for characterizing CO2 migration, dissolution and reaction by looking at chemical characteristics of the different reservoirs (Figure 2). The data we present reveal interesting trends for CO2 mol% and -13C both spatially and with each other as observed by Edwards et al. (2007). Our interpretation of the data suggests that mineral carbonation in certain fields can be significant and relatively rapid. The Gorgon and Rankin Trend fields natural gases may therefore be a unique natural laboratory, which give further insights into the rates and extent of carbonate mineral sequestration as applied to carbon storage operations.

The ca. 1000 Ma Brattstrand Paragneiss in the Larsemann Hills contains a unique assemblage of borosilicate-rich rocks: tourmaline (Tur) quartzite, prismatine (Prs) leucogneiss and grandidierite (Gdd) borosilicate gneiss. In situ analyses with a Cameca ims 4f ion microprobe gave '11B (= {[sample11B/10B / SRM 95111B/10B] - 1} × 1000) to be '3.0 to '14.3? in Tur, '9.6 to '18.1' in Prs and '1.9 to '8.7' in Gdd (1s mostly 1-2' per sample). In anatectic pegmatites, Tur '11B = 4.8 to '12.1'; comparison with host rock Tur implies melting and crystallization from melt together did not fractionate B isotopes. With two exceptions, average '11B increases in a given sample Prs < Tur < Gdd with Prs B 4.8±1.6' lighter and Gdd B 2.8±1.9' heavier than Tur B. This regularity is consistent with the preference of 10B for tetrahedral sites (Prs) and 11B for trigonal sites (Tur, Gdd) and crystallization in near isotopic equilibrium. The precursor of the B-rich rock least changed by metamorphism, Tur quartzite, is interpreted to be a product of pre-metamorphic, hydrothermal B-metasomatism. If there had been no '11B decrease from devolatization during metamorphism, quartzite Tur '11B ('8.7 to '5.7') constrains '11B of premetamorphic fluid to be '3 to 0' (2008 Tur-fluid '11B for 200 C), consistent with a continental source. However, more likely devolatization decreased Tur '11B, and '11B > 0' in the premetamorphic fluid, so an alternative precursor, such as mud volcanoes, should be considered.

This web service provides access to the Geoscience Australia (GA) ISOTOPE database containing compiled age and isotopic data from a range of published and unpublished (GA and non-GA) sources. The web service includes point layers (WFS, WMS, WMTS) with age and isotopic attribute information from the ISOTOPE database, and raster layers (WMS, WMTS, WCS) comprising the Isotopic Atlas grids which are interpolations of the point located age and isotope data in the ISOTOPE database.

The oxygen isotopic record obtained from Globigerina bulloides, Globorotalia inflata, and Neogloboquadrina pachyderma (s.) was analysed for 5 sediment traps moored in the Southern Ocean and Southwest Pacific. The traps extend from Subtropical to the Polar Frontal environments, providing the first analysis of seasonal foraminiferal d18O records from these latitudes. Comparison between the foraminiferal records and various equations for predicted d18O of calcite reveals that the predicted d18O is best captured by the equations of Epstein et al. (1953) [Epstein, S., Buchsbaum, R., Lowenstam, H.A., Urey, H.C., 1953. Revised carbonate-water isotopic temperature scale. Geological Society of America Bulletin 64, 1315-1326.] and Kim and O'Neil (1997) [Kim, S.-T., O'Neil, J.R., 1997. Equilibrium and non-equilibrium oxygen isotope effects in synthetic carbonates. Geochimica et Cosmochimica Acta 61, 3461-3475.]. The Epstein equation shows a constant offset from the -18O of G. bulloides and N. pachyderma (s.) across the full range of latitudes. The seasonal range in -18O values for these two species implies a near-surface habitat across all sites, while G. inflata most likely dwells at 50 m depth. A significant finding in this study was that offsets from predicted -18O for G. bulloides do not correlate to changes in the carbonate ion concentration. This suggests that [CO32-] in and of itself may not capture the full range of carbonate chemistry conditions in the marine system. This sediment trap deployment also reveals distinct seasonal flux patterns for each species. Comparison between flux-weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint. At the 51°S site, G. bulloides has a spring flux peak while N. pachyderma (s.) is dominated by summer production.

Australia as it exists today is a product of geological processes that have occurred over its 4.5 billion year history. Isotopic studies are one approach to understanding the history and evolution of the Australian continent. Isotope geochronology tells us about the timing of a wide range of geological processes like crystallisation, deformation and cooling of rocks. Isotope geochemistry informs on the precursor components from which the rocks formed, and can act as 'paleogeophysical' sensors to tell us more about the subsurface. The Isotopic Atlas of Australia brings together five of the most widely used isotopic systems in geology and delivers publicly available maps and datasets in a consistent format. This work is unlocking the collective value of decades of investment in data collection, and facilitating qualitative and quantitative comparison and integration with other datasets such as geophysical images. This talk will be an introduction to the world of isotopes as applied to understand geology, and an overview of the Isotopic Atlas recently produced as part of the Exploring for the Future Program.

Earth is the only terrestrial planet in the solar system with continents, and hence understanding their evolution is vital to unravelling what makes Earth special – our liquid oceans, oxygenated atmosphere, and ultimately, life. The continental crust is also host to all our mineable mineral deposits, and hence it has played a key role in the establishment of human civilisation. This link between the crust and human development will be even more prominent through the need for critical metals, as our society transitions toward green technologies. In this talk, we will discuss the link between the time-space evolution of the continental crust and the location of major mineral systems. By using isotopic data from micron-scale zircon crystals, we can map the crustal architectures that control the large-scale localisation of numerous mineral provinces. This work demonstrates the intimate link between the evolution of the continents, the understanding of mineral systems, and ultimately our continued evolution as an industrialised society.

This report is published in two volumes; Volume I: Bowen-Surat and Cooper-Eromanga Basins, Volume II: Gippsland, Bass, Otway, Stansbury, McArthur, Amadeus, Adavale, Galilee and Drummond Basins. Following the basin-by-basin analysis of geochemical characteristics of eastern Australia's oils, a selection of oils that best represented the major families of each region were selected. These oils were statistically analysed using a subset of geochemical (OilMod) parameters derived from GC, GC-MS and carbon isotopic analyses. This exercise was intended to display the variability in oil compositions across the whole of the eastern part of the continent. The chemical classification of oils follows closely upon, and verifies the analysis based on, palaeogeography and the supersystem concepts.