New provenance data from Palaeoproterozoic and possible Archaean sedimentary units in the central eastern Gawler Craton forms part of a growing dataset suggesting that the Gawler Craton shares important basin formation and tectonic time lines with the adjacent Curnamona Province and the Isan Inlier in northern Australia. U-Pb dating of detrital zircons from the Eba Formation (previously mapped as Tarcoola Formation), yield exclusively Archaean ages (~2530-3300 Ma). This is consistent with whole rock Nd and zircon Hf isotopic data for the Eba Formation which have evolved compositions. Elsewhere in the eastern Gawler Craton, cover sequences historically considered to be Palaeoproterozoic in age also contain exclusively Neo and Meso Archaean aged detrital zircons (Reid et al, 2009 Econ. Geol.; Szpunar et al, 2007, SGTSG). The absence of Palaeoproterozoic detrital grains in several differently mapped sequences (including the Eba Formation) despite the proximity of voluminous Palaeoproterozoic rock units, suggests that the Eba Formation may be part of a Neo-Archaean or early Palaeoproterozoic cover sequence derived from erosion of a complex Archaean aged source region. The Labyrinth Formation unconformably overlies the Eba Quartzite, and contains rhyolitic units that constrain deposition to 1715 ± 9 Ma (Fanning et al., 2007; PIRSA Bulletin 55). This age is identical to the timing of deposition of the lower Willyama Supergroup in the adjacent Curnamona Province. Detrital zircon ages in the Labyrinth Formation range from NeoArchaean to Palaeoproterozoic, and are consistent with derivation from > 1715 Ma components of the Gawler Craton. Isotopic zircon Hf data and whole rock Nd data also suggest a source region with a mixed crustal evolution (-Nd -4.5 to -6), consistent with what is known about the Gawler Craton. Compared to the Lower Willyama Supergroup, the Labyrinth Formation has a source more obviously reconcilable with the Gawler Craton.

Ocean margins are the transitional zones between the oceans and continents. They represent dynamic systems in which numerous processes shape the environment and result in impacting the utilization and hazard potentials for humans. These processes are influenced by a variety of steering mechanisms, from mountain building and climate on the land to tectonics and sea-level fluctuations in ocean margins. This book examines various aspects of regulation for the long-term development of ocean margins, of the impact of fluids and of the dynamics of benthic life at and below the seafloor in ocean margin systems.

Many countries around the world, including some developing countries, have carried out geochemical surveys of their territory. Data and information layers that result from these surveys have been put to a multitude of beneficial uses, such as discovering mineralisation, improving the land-use decision-making process, delineating natural or anthropogenic risks to plants, animals and humans, and better rehabilitating contaminated sites. In 2007, following on from the successful completion of a series of pilot projects in south-eastern Australia, Geoscience Australia initiated Australia's first national geochemical survey. In collaboration with the State and Northern territory geoscience agencies an ultra low density sampling campaign has commenced. Samples of catchment outlet (overbank) sediments are being collected from two depths (0-10 cm below surface and from a 10 cm interval at around 60-90 cm). These sediments are deposited as fine-grained detritus during the receding phase of major floods and are believed to best represent the average composition of the upstream catchment. Samples are prepared and split into <2 mm and <75 mm fractions before being analysed using a wide range of analytical techniques including XRF and ICP-MS. Two years into this four-and-a-half year project, 78% of samples have been collected and 25% of samples from across the nation have been analysed; the preliminary findings will be reported here. Australia's pilot surveys identified geochemical patterns relating to soil acidity and salinity and reflecting known areas of mineralisation as well as element concentrations in agricultural soils that were above or below national and international guidelines. Ultimately the National Geochemical Survey of Australia project will rapidly and cost-effectively deliver a national geochemical atlas that will underpin positive outcomes in the exploration and mining, environmental, agricultural, forestry, recreational, and health and well-being sectors.

The first large scale projects for geological storage of carbon dioxide on the Australian mainland are likely to occur within sedimentary sequences that underlie or are within the Triassic Cretaceous Great Artesian Basin aquifer sequence. Recent national and state assessments have concluded that certain deep formations within the Great Artesian Basin show considerable geological suitability for the storage of greenhouse gases. These same formations contain trapped methane and naturally generated carbon dioxide stored for millions of years. In July 2010, the Queensland Government released exploration permits for Greenhouse Gas Storage in the Surat and Galilee basins. An important consideration in assessing the potential economic, environmental, health and safety risks of such projects is the potential impact carbon dioxide migrating out of storage reservoirs could have on overlying groundwater resources. The risk and impact of carbon dioxide migrating from a greenhouse gas storage reservoir into groundwater cannot be objectively assessed without an adequate knowledge of the natural baseline characteristics of the groundwater within these systems. Due to the phase behaviour of carbon dioxide, geological storage of carbon dioxide in the supercritical state requires depths greater than 800m, but there are few hydrogeochemical studies of these deeper aquifers in the prospective storage areas. Historical hydrogeochemical data were compiled from various State and Federal Government agencies. In addition, hydrogeochemical information has been compiled from thousands of petroleum well completion reports in order to obtain more information on the deeper aquifers, not typically used for agriculture or human consumption. The data were passed through a quality checking procedure to check for mud contamination and ascertain whether a representative sample had been collected. The large majority of the samples proved to be contaminated but a small selection passed the quality checking criteria.

<p>The onshore Canning Basin in Western Australia is the focus of a regional hydrocarbon prospectivity assessment being undertaken by the Exploring for the Future (EFTF) program; an initiative by the Australian Government dedicated to boosting investment in resource exploration in Australia. The four-year program led by Geoscience Australia focusses on the acquisition of new data and information about the potential mineral, energy and groundwater resources concealed beneath the surface in northern Australia and parts of South Australia. As part of this program, significant work has been carried out to deliver new pre-competitive data including new seismic, drilling of a stratigraphic well and the geochemical analysis of petroleum recovered from exploration wells. <p>Current conventional remaining gas resources of the Canning Basin are deemed limited (0.2 TCF; AERA, 2018), whereas unconventional gas resources are inferred to be extremely high, with estimated recoverable resources for shale gas and tight gas being 452.3 TCF (5% of P50,Table 2; AREA, 2018). This disparity arises from the high degree of uncertainty of key geological factors, particularly the poor constraints on source rock volumetrics, the lack of understanding of the volume of gaseous hydrocarbons generated and the origin and degree of thermal maturity of the gases. Carbon isotopic data are scarce and hydrogen isotopic data are non-existent, even though numerous gas discoveries have been made across the Lennard Shelf, Broome Platform and Fitzroy Trough following the initial discovery at Pictor 1 in 1984 by BHP Petroleum (Cadman et al., 1993; Jonasson, 2001). Indeed, gas samples have only been available for analyses since the drilling campaign by Buru Energy in 2010, and more recently, mud gases collected in IsoTubes are routinely sampled during drilling and presented in well completion reports (e.g. Cyrene 1; Nicolay 1, Paradise Deepening 1, Theia 1, Yulleroo 3 and Yulleroo 4). <p>This component of the EFTF program, evaluates the molecular and isotopic composition of natural gases from petroleum wells and a hot-spring seep at Mount Wynne, to constrain the much publicised resource potential inferred in this basin. Interpretation of these data will also assist with in the determination of their origin, and hence increase our understanding of the Larapintine Petroleum Supersystem, as proposed by Bradshaw (1983) and Bradshaw et al. (1984). All gas analyses in this study were undertaken by Geoscience Australia’s Organic Geochemistry Laboratory.

The evolution of the Paleo- and Mesoproterozoic of Australia is controversial. Early tectonic models were largely autochthonous, in part driven by the chemical characteristics of Proterozoic felsic magmatism: overwhelmingly potassic, often with elevated Th and U contents, and with evolved isotopic signatures, consistent with crustal sources and the implication they were not generated within continental arcs. This model has been increasingly challenged over the last 30 years, driven by the recognition of the diversity of Proterozoic magmatism, of linear magmatic belts often with subduction-compatible geochemistry and juvenile isotopic signatures, and of across-strike trends in isotope signatures, all consistent with continental margin processes. These, and other geological evidence for crustal terranes, suggest subduction-related tectonic regimes and collisional orogenesis. Current tectonic models for the Australia Proterozoic invoke such processes with varying number of continental fragments and arcs, related to assembly/break-up of the Nuna Supercontinent. Problems still exist however as the observations of early workers still largely hold-much Proterozoic magmatism was intracratonic, and interpreted backarc magmatism largely lacks obvious related arcs. This has led to more recent hybrid arc-plume models. No one model is completely satisfactory, however, reflecting ambiguity of geochemical data and secular arguments (when did modern-style tectonics actually begin).

This data package comprises three data sets which cover the ST ARNAUD 1:250 000 map sheet area (ST ARNAUD). This area has recently been covered by airborne geophysical surveys by the Australian Geological Survey Organisation and geologically mapped by the Geological Survey of Victoria and this data package intends to compliment these data.

Cratonic margins host many of the natural resources upon which our society depends. Despite this, little is known about the dynamic evolution of these regions and the stability of substantial steps in plate thickness that delineate their boundaries with adjacent mantle. Here, we investigate the spatio-temporal evolution of Australian cratonic lithosphere and underlying asthenospheric mantle by using the geochemical composition of mafic volcanic or shallow intrusive rocks preserved throughout the continent’s history. We have collated a large database of mafic samples that were screened to remove data affected by crystal fractionation or assimilation of cumulate material. We use forward and inverse modelling of igneous trace element compositions to calculate the depth and extent of melting for 28 distinct igneous provinces in the North Australian Craton. These results are used to infer mantle potential temperature and lithospheric thickness at the time of eruption. The majority of Paleoproterozoic magmatic events record high mantle potential temperatures of 1350–1450 °C and relatively low lithospheric thicknesses of ≤50 km. In contrast, younger igneous provinces show a gradual decrease in potential temperature and an increase in lithospheric thickness with time. These constraints on the mantle lay the foundation for the development of a quantitative geodynamic understanding of the evolution of the Australian lithosphere and its resources. <b>Citation:</b> Klöcking, M., Czarnota, K., Champion, D.C., Jaques, A.L. and Davies, D. R., 2020. Mapping the cover in northern Australia: towards a unified national 3D geological model. In: Czarnota, K., Roach, I., Abbott, S., Haynes, M., Kositcin, N., Ray, A. and Slatter, E. (eds.) Exploring for the Future: Extended Abstracts, Geoscience Australia, Canberra, 1–4.

The present report is a compilation of 531 geochemical maps that result from the National Geochemical Survey of Australia. These constitute the first continental-scale series of geochemical maps based on internally consistent, state-of-the-art data pertaining to the same sampling medium collected, prepared and analysed in a uniform and well documented manner and over a short time period (four years). Interpretations of the data and maps will be published separately. The geochemical maps can be used for better understanding the accumulation, mobility and significance of chemical elements in the near-surface environment of Australia. It is expected that they will provide a new, additional pre-competitive dataset for the energy and mineral resource exploration industry, which should help prioritise areas for further exploration investment and thus reduce risk. Further, it is also likely that some of the geochemical maps will find use in other disciplines related to natural resource management and environmental monitoring.

Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and the Department of Environment and Natural Resources within the Northern Territory Government (DENR) undertook collaborative seabed mapping surveys (GA0351/SOL6187, GA4452/SOL6432 and combined GA0361 & GA0362) in the Darwin-Bynoe Harbour region between 2015 and 2018. This seabed mapping project forms a core component of a four-year collaborative research program between DENR, GA and AIMS, which was funded by the INPEX-operated Ichthys LNG Project to DENR, with co-investment by GA and AIMS. The purpose of the program is to improve knowledge of the marine environments in the Darwin and Bynoe Harbour regions through the collation and acquisition of baseline data that enable the creation of habitat maps to better inform marine resource management decisions. Mapping and sampling in the survey area utilised multibeam echosounders, sub-bottom profilers, underwater cameras and grab samplers. In total, this data package extends over an area of 1978 km2, including 1754 km2 mapped using multibeam echosounders, during four marine surveys over 247 days. The baseline environmental data acquired in this program provides new insights into the marine environments of the Greater Darwin and Bynoe Harbour region, will inform future environmental assessments in the region and help build our knowledge of seabed features and processes in tropical northern Australia.