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  • Effective mineral, energy and groundwater resource management and exploration rely on accurate geological maps. While geological maps of the surface exist and increase in resolution, maps of the subsurface are sparse, and the underpinning geological and geophysical constraints are disordered or non-existent. The Estimates of Geological and Geophysical Surfaces (EGGS) database seeks to enable robust subsurface geological mapping by establishing an ordered collection of precious geological and geophysical interpretations of the subsurface. EGGS stores the depth to geological boundaries derived from boreholes as well as interpretations of depth to magnetic top assessments, airborne electromagnetics inversions and reflection seismic profiles. Since geological interpretation is iterative, links to geophysical datasets and processing streams used to image the subsurface are stored. These metadata allow interpretations to be readily associated with the datasets from which they are derived and re-examined. The geological basis for the interpretation is also recorded. Stratigraphic consistency is maintained by linking each interpretation to the Australian Stratigraphic Units Database. As part of the Exploring for the Future program, >170 000 points were entered into the EGGS database. These points underpin construction of cover thickness models and economic fairway assessments. <b>Citation:</b> Mathews, E.J., Czarnota, K., Meixner, A.J., Bonnardot, M.-A., Curtis, C., Wilford, J., Nicoll, M.G., Wong, S.C.T., Thorose, M. and Ley-Cooper, Y., 2020. Putting all your EGGS in one basket: the Estimates of Geological and Geophysical Surfaces database. 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.

  • With the increasing need to extend mineral exploration undercover, new approaches are required to better constrain concealed geology, thereby reducing exploration risk and search space. Hydrogeochemistry is an under-utilised tool that can identify subsurface geology and buried mineral system components, while also providing valuable insights into environmental baselines, energy systems and groundwater resources. With this aim, 238 water bores spanning seven geological provinces in the Northern Territory and Queensland were sampled and analysed for major cations and anions, trace elements, stable and radiogenic isotopes, organic species, and dissolved gases. Here, we demonstrate the utility of this dataset for identifying carbonate-rich aquifers and mineral system components therein. First, we use trends in major element ratios (Ca+Mg)/Cl– and SiO2/HCO–3, then strontium isotope ratios (87Sr/86Sr), to define subpopulations that reflect both spatial and compositional differences. We then apply mafic-to-felsic trace element ratios (V/Cs and Cu/Rb) to reveal elevated base metal concentrations near Lake Woods caused by water–rock interaction with dolerite intrusions. Correlated Sr concentrations between groundwater and surface sediments suggest that the geochemical evolution of these mediums in carbonate-dominated terrains is coupled. Our work develops an approach to guide mineral exploration undercover via the characterisation and differentiation of groundwaters from different aquifers, resulting in improved identification of geochemical anomalies. <b>Citation:</b> Schroder, I., de Caritat, P. and Wallace, L., 2020. The Northern Australia Hydrogeochemical Survey: aquifer lithologies, local backgrounds and undercover processes. 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.

  • <p>Australia has a significant number of surface sediment geochemical surveys that have been undertaken by industry and government during the past 50 years. These surveys represent a vast investment, but up to now have been used in isolation from one another. The key to maximising the full potential of these data and the information they provide for mineral exploration, environmental management and agricultural purposes is using all surveys together, seamlessly. These geochemical surveys have not only sampled various landscape elements but have used multiple analytical techniques, instrumentation and laboratories. The geochemical data from these surveys need to be levelled to eliminate, as much as possible, non-geological variation. Using a variety of methodologies, including reanalysis of both international standards and small subsets of samples from previous surveys, we have created a seamless surface geochemical map for northern Australia, from nine surveys with 15605 samples. We tested our approach using two surveys from the southern Thomson Orogen, which removed interlaboratory and other analytical variation. Creation of the new combined and levelled northern Australian dataset paves the way for the application of statistical techniques, such as principal component analysis and machine learning, which maximise the value of these legacy data holdings. The methodology documented here can be applied to additional geochemical datasets that become available. <p><b>Citation:</b> Main, P. T. and Champion, D. C., 2020. Geochemistry of the North Australian Craton: piecing it together. 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.

  • Metamorphic rocks provide a semi-continuous record of the thermal and barometric history of the crust, which is particularly useful in constraining paleo-crustal architectures, tectonic models and thereby mineral exploration. Given this importance, regional metamorphic studies in Australia have flourished during the past 30 years. However, the national metamorphic map of Australia has not been updated in more than 37 years. Here, we provide a snapshot of a national synthesis of all available quantitative metamorphic data, metamorphic chronology and metamorphic map patterns, integrated with stratigraphic, magmatic and kinematic datasets. Forty-eight orogenic cycles have been identified, spanning from the Paleoarchean to the Miocene, and most of permissible pressure (P) and temperature (T) space, indicating a wide variety of tectonic settings. This compilation provides a basis for establishing best-estimate working models for the metamorphic evolution of all orogenic systems, provinces and terranes. These insights are important in advancing the understanding of mineral systems in Australia.. <b>Citation:</b> Goscombe, B., Czarnota, K. Blewett, R.S. Skirrow, R.G. Everard, J.L. and Lawson, C., 2020. Metamorphic evolution of Australia. 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.

  • This compilation data release is a selection of remotely sensed imagery used in the Exploring for the Future (EFTF) East Kimberley Groundwater Project. Datasets include: • Mosaic 5 m digital elevation model (DEM) with shaded relief • Normalised Difference Vegetation Index (NDVI) percentiles • Tasselled Cap exceedance summaries • Normalised Difference Moisture Index (NDMI) • Normalised Difference Wetness Index (NDWI) The 5m spatial resolution digital elevation model with associated shaded relief image were derived from the East Kimberley 2017 LiDAR survey (Geoscience Australia, 2019b). The Normalised Difference Vegetation Index (NDVI) percentiles include 20th, 50th, and 80th for dry seasons (April to October) 1987 to 2018 and were derived from the Landsat 5,7 and 8 data stored in Digital Earth Australia (see Geoscience Australia, 2019a). Tasselled Cap Exceedance Summary include brightness, greenness and wetness as a composite image and were also derived from the Landsat data. These surface reflectance products can be used to highlight vegetation characteristics such as wetness and greenness, and land cover. The Normalised Difference Moisture Index (NDMI) and Normalised Difference Water Index (NDWI) were derived from the Sentinel-2 satellite imagery. These datasets have been classified and visually enhanced to detect vegetation moisture stress or water-logging and show distribution of moisture. For example, positive NDWI values indicate waterlogged areas while waterbodies typically correspond with values greater than 0.2. Waterlogged areas also correspond to NDMI values of 0.2 to 0.4. Geoscience Australia, 2019a. Earth Observation Archive. Geoscience Australia, Canberra. http://dx.doi.org/10.4225/25/57D9DCA3910CD Geoscience Australia, 2019b. Kimberley East - LiDAR data. Geoscience Australia, Canberra. C7FDA017-80B2-4F98-8147-4D3E4DF595A2 http://pid.geoscience.gov.au/dataset/ga/129985

  • Real advances in understanding geology for mineral, energy and groundwater resource potential of the Australian continent will come from unveiling what lies at depth, especially in the extensive under-explored regions that are obscured by cover. In this context, airborne electromagnetics (AEM) is a geophysical method at the forefront in addressing the challenge of exploration undercover. In collaboration with the state and territory geological surveys, Geoscience Australia has led a national initiative whose goal is to acquire AEM data at 20 km line spacing across Australia. This initiative, AusAEM, represents the world’s largest AEM survey flown to date; it has covered ~2.5 million km2, a substantial part of northern Australia, and is providing new insights in areas that have not been extensively explored. Regional models of subsurface electrical conductivity derived from AusAEM data support a range of applications that include geological mapping, mineral and petroleum exploration, watershed management and environmental studies. <b>Citation:</b> Ley Cooper, A.Y.. and Brodie, R.C.., 2020. AusAEM: imaging the near-surface from the world’s largest airborne electromagnetic survey. 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.

  • Groundwater is an essential part of Darwin’s water supply mix, and is sourced from Howard East Borefield (HEB) and McMinns Borefield in the Koolpinyah Dolostone Aquifer (KDA), east of Darwin. Previous work suggested that electrical conductivity anomalies observed in airborne electromagnetic (AEM) data within 8 km of HEB may be caused by saline groundwater within the KDA that is separated from HEB by geological features that effectively compartmentalise the aquifer. Nevertheless, concerns grew that increased groundwater use may result in migration of saline groundwater towards HEB, which could compromise the groundwater resource. We collected hydrochemistry, including isotopes, time-series groundwater salinity and AEM data to better understand the complexities of the KDA. These data are presented here, along with a hydrodynamic analysis undertaken by the Northern Territory Department of Environment and Natural Resources, which shows that drawdown is occurring more rapidly from the NE of HEB and that dykes ~8 km NE of HEB act as barriers to groundwater flow. We show that groundwater sampled on the NE side of these dykes has a seawater composition. We use new AEM data to map the elevation of the top of unweathered dyke material and to characterise AEM conductors proximal to HEB. Our mapping reveals that the top of the unweathered portion of these dykes is commonly below sea level. We also show that AEM conductors proximal to HEB are more likely mineralised clays than saline groundwater within the aquifer. Drilling is required to confirm these results. Our findings contribute to building a robust conceptual understanding of the KDA and will inform future modelling of the groundwater system. <b>Citation:</b> Haiblen, A.M., Symington, N.J., Woltmann, M.J., Ray, A., Gow, L.J., Leplastrier, A. and McGrath, E.S.B., 2020. A multifaceted approach to investigating hydrogeological complexities in the Koolpinyah Dolostone Aquifer, Howard East, Northern Territory. 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 North Australian Zinc Belt is the largest zinc–lead province in the world, containing 3 of the 10 largest individual deposits known. Despite this pedigree, exploration in this province during the past two decades has not been particularly successful, yielding only one significant deposit (Teena). One of the most important aspects of exploration is to choose regions or provinces that have greatest potential for discovery. Here, we present results from zinc belts in northern Australia and North America, which highlight previously unused datasets for area selection and targeting at the craton to district scale. Lead isotope mapping using analyses of mineralised material has identified gradients in μ (238U/204Pb) that coincide closely with many major deposits. Locations of these deposits also coincide with a gradient in the depth of the lithosphere–asthenosphere boundary determined from calibrated surface wave tomography models converted to temperature. In Australia, gradients in upward-continued gravity anomalies and a step in Moho depth corresponding to a pre-existing major crustal boundary are also observed. The change from thicker to thinner lithosphere is interpreted to localise prospective basins for zinc–lead and copper–cobalt mineralisation, and to control the gradient in lead isotope and other geophysical data. <b>Citation:</b> Huston, D.L., Champion, D.C., Czarnota, K., Hutchens, M., Hoggard, M., Ware, B., Richards, F., Tessalina, S., Gibson, G.M. and Carr, G., 2020. Lithospheric-scale controls on zinc–lead–silver deposits of the North Australian Zinc Belt: evidence from isotopic and geophysical data. 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 Kidson Sub-basin covers ~91 000 km2, and is a largely under-explored and sparsely imaged region of the Canning Basin in northern Western Australia. The 872 km Kidson Sub-basin seismic survey was acquired to enhance understanding of the subsurface and thereby assist in the assessment of the region for hydrocarbon and mineral potential. Specifically, the survey aimed to improve basin-wide stratigraphic correlation, determine the extent of basin depocentres, image major structures and place constraints on the sub-basin’s geological event history. The new seismic profile reveals that the Kidson Sub-basin is ~500 km long and ~6.5 km deep. It contains a lower conformable package of Ordovician to Devonian clastic sediments, carbonates and evaporites unconformably overlain by the clastic-dominated Permian Grant Group and Poole Sandstone. Normal faults imaged at the base of the sequence with growth strata in the hanging wall constrain rifting to between Cambrian and Silurian in age. Folding along the southeastern edge of the basin is inferred to be a consequence of the Carboniferous Meda Transpression linked to the Alice Springs Orogeny in central Australia. The known source rocks of the Goldwyer and Bongabinni formations have been interpreted to extend across the Kidson Sub-basin, which is encouraging for energy prospectivity in the region. <b>Citation:</b> Southby, C., Carr, L.K., Henson, P., Haines, P.W., Zhan, A., Anderson, J.R., MacFarlane, S., Fomin, T. and Costelloe, R., 2020. Exploring for the Future: Kidson Sub-basin seismic interpretation. 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.

  • A key focus of the Exploring for the Future program was the Kidson Sub-basin, a large, underexplored and poorly understood depocentre in the southern part of the Canning Basin of Western Australia. The Canning Basin hosts proven petroleum systems and has recently become an area of interest for unconventional hydrocarbon exploration. Several formations within deeper basin depocentres are under investigation. Unconventional petroleum resource evaluation is generally dependent on an understanding of both local and regional stresses, as these exert a control over subsurface fluid flow pathways, as well as the geomechanical properties of reservoir units. Gaps exist in our understanding of these factors within the Canning Basin, and particularly the Kidson Sub-basin where wellbore coverage is sparse. This study identifies a generally NE–SW-oriented regional maximum horizontal stress azimuth from interpretation of borehole failure in five petroleum wells, and a broadly strike–slip faulting stress regime from wireline data and wellbore testing. Variations in stress regime at different crustal levels within the basin are highlighted by one-dimensional mechanical earth models that show changes in the stress regime with depth as well as by lithology, with a general shift towards a normal faulting stress regime at depths greater than ~2.5 km. <b>Citation:</b> Bailey, A.H.E. and Henson, P., 2020. Present-day stresses of the Canning Basin, WA. 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.