The structural evolution of the South Nicholson region is not well understood, hindering full appraisal of the resource potential across the region. Here, we outline new insights from a recent deep-reflection seismic survey, collected as part of the Australian Government’s Exploring for the Future initiative. The new seismic profiles, and new field observations and geochronology, indicate that the South Nicholson region was characterised by episodic development of a series of ENE-trending half grabens. These graben structures experienced two major episodes of extension, at ca. 1725 Ma and ca. 1640 Ma, broadly correlating with extensional events identified from the Lawn Hill Platform and the Mount Isa Province to the east. Southward stratal thickening of both Calvert and Isa Superbasin sequences (Paleoproterozoic Carrara Range and McNamara groups, respectively) into north-dipping bounding faults is consistent with syndepositional extension during half graben formation. Subsequent basin inversion, and reactivation of the half graben bounding faults as south-verging thrusts, appears to have been episodic. The observed geometry and offset are interpreted as the cumulative effect of multiple tectonic events, including the Isan Orogeny, with thrust movement on faults occurring until at least the Paleozoic Alice Springs Orogeny. <b>Citation:</b> Carson, C.J.. Henson, P.A., Doublier, M.P., Williams, B., Simmons, J., Hutton, L. and Close, D., 2020. Structural evolution of the South Nicholson region: insight from the 2017 L210 reflection seismic 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.

Exploring for the Future is a four-year $100.5 million programme to unveil new resource opportunities in Northern Australia and parts of South Australia. It is being conducted by Geoscience Australia in partnership with state and Northern Territory government agencies, CSIRO, and universities. This initiative, which is due for completion in 2020–2021, has started to deliver a suite of new products to help unveil new resource opportunities in Northern Australia. The programme has three inter-related elements: minerals, energy and groundwater, which collectively aims to: • provide baseline pre-competitive geoscience data to inform and encourage government, industry and community decision making about sustainable resources management to improve Northern Australia’s economic development • attract investment in resource exploration to Northern Australia • deliver an assessment of groundwater resources for irrigated agriculture and community water supplies as well as for mineral and energy development; and an assessment of the potential impacts of those developments. The minerals-focussed projects have been designed with a three-fold programme logic (Figure 1): 1) Northern Australia-wide projects, 2) focussed integrated studies, and 3) generic innovation and method development. The minerals-focussed project activities address a number of the highest and high priority themes identified by the mineral exploration industry in the UNCOVER Roadmap. 1) Northern Australia-wide projects This work programme will develop and use innovative tools and techniques to collect semi-continental a) geological, b) geochemical, and c) geophysical data on an unprecedented scale. The commencement of these projects is focussed on the region between Tennant Creek and Mt Isa (TISA). a) Geological projects Because one person’s cover is another person’s basement, a Northern Australia-wide series of time-based geological maps are being prepared. Building from the national 1:1 M scale Surface Geology Map of Australia, the Cenozoic, Mesozoic, Palaeozoic and Neoproterozoic layers will be successively removed to reveal a series of ‘solid geology’ maps at 1:1M scale. These maps will form the basis for subsequent 3D models and resource assessments. Extensive use is being made of national-scale potential field geophysical data and existing drillhole data. This has the combined effect of calibrating the geological interpretation of the geophysics with known rocks and attributing the interfaces with their actual depth (from drilling or geophysical estimates). Resultant 3D data are being stored in a new database called Estimates of Geological and Geophysical Surfaces (EGGS); this is a national repository for depth-determined geological information from any method (drilling or geophysical estimate). The EGGS’ database will form the depth-control points from which new 3D surfaces will be constructed and imported into a 3D geological model along with uncertainty. A new peak metamorphic map of Australia is also in production, with a subset available for Northern Australia in the first phase. This map is a compilation of quantitative and qualitative estimates of metamorphic conditions across Australia. The maps will provide important constraints on the crustal exhumation and (mineral) preservation history as well as thermo-barometric evolution of Australia. b) Geochemical projects An atlas of the surface of Northern Australia, as a subset of the national atlas, is in preparation. Geoscience Australia has time-series LANDSAT data from NASA extending back into the 1980s. Each pixel from each scene has been organised in Digital Earth Australia (DEA) so the archive can be ‘data-mined’ to extract pixels with the least vegetation and cloud-cover effects. Products of this work will be a new national Bare Earth image along with iron oxide, silica and clay mineral maps of the surface at 25 m resolution. The European Space Agency’s Sentinel 2 satellite system provides global coverage of multispectral earth-observation data at 10 m resolution from these data. A new cloud-free seamless Sentinel 2 national map will be produced at 10 m resolution. A suite of new machine learning codes has been produced in collaboration with DATA61. These codes are being deployed on the national whole rock and surface geochemical datasets to produce national surface maps of the major elements. An isotopic atlas for northern Australia is being prepared, consisting of a suite of map layers including Sm–Nd, Lu–Hf, U–Pb, Ar–Ar and Pb–Pb; it will be delivered in GIS form, and draped on the aforementioned 3D surfaces. In addition, selected age dating of geological units through U–Pb SHRIMP geochronology and various other dating techniques for direct dating of key mineral deposits are being undertaken. c) Geophysical projects The world’s largest airborne electromagnetic (AusAEM) survey and the most extensive long-period magnetotelluric (AusLAMP) survey are well underway. At the time of writing (February 2018), 20 600 line-km of the 60,000 planned AusAEM data have been flown and 155 new AusLAMP stations have been acquired. In addition, a new seismic tomographic velocity model will be constructed from historical earthquake data; these data form the basis of the Australia-wide AusARRAY project. Gravity data are being infilled at higher resolutions in areas where station spacing is >4 km using a mix of ground and airborne gravity and airborne gravity gradiometry. 2) Focused Integrated Studies (TISA) The region between Tennant Creek and Mt Isa (TISA) is the initial focus of all the above-mentioned activities plus a series of additional projects. This vast under cover region lies between the great mining centres of Tennant Creek (Cu, Au) and Mt Isa (Cu, Pb, Zn, Ag). The thickness of cover is variable and the underlying ‘basement’ geology is poorly known. The region lies at a key junction in Australian geology, with north-south striking domains in the east joining east-west and northwest-southeast striking domains in the west. The region showed unexplained base metal anomalism in the National Geochemical Survey of Australia (NGSA) and at depth, it has variable seismic velocity and Moho depths. The programme has collected 782 surface geochemical and 118 groundwater samples to augment the broad-spaced NGSA dataset; laboratory results are being modelled with the first products due for release in March 2018. The AusARRAY project deployed 120 passive seismic recorders that will remain in the TISA region until later this year. Two more deployments are expected in the life of the programme at locations to be confirmed. A total of 2724 ground gravity stations were collected; the data was released in 2017. A total of 1100 km of deep seismic reflection data have been acquired and processed (see Henson this volume), with processed data to be released in March 2018, and interpretation products to follow. The aim of focusing the activities into one region is to provide the best possible suite of data that will be integrated into an assessment of the undercover mineral potential of the TISA region. This assessment and the geological and mineral systems interpretations of the above data will be tested by a stratigraphic drilling programme in 2019. Assessments are underway for basin-hosted base metals (Cu, Pb, Zn) and for iron-oxide-copper-gold mineral systems. The basin assessment will draw on well-established petroleum systems approaches and apply them to these mineral systems. When the programme is complete, the TISA region will arguably be the best imaged and understood piece of lithosphere on the planet. 3) Innovation and Method Development To complement data acquisition, new big data management and data analytical methods, tools and platforms are being developed to maximise data value. Strategic collaborations have been established with world-leading experts at Australian universities and DATA61 to develop a suite of new geoscience-relevant computer codes and products that will be released in open source repositories (GitHub) and be incorporated into the Australian National Virtual Geophysical Laboratory (ANVGL). Given the vast range of activities being conducted, many of which are novel, effort is being made to share the generic lessons. This includes publishing software codes and standard operating procedures as well as developing an Explorer’s Guide for the TISA region that will have generic applicability elsewhere. Particular effort is being made to transfer knowledge and receive feedback from industry through a series of workshops that commenced in 2017. Conclusions Exploring for the Future, an exciting initiative in collaboration with state and NT partners, will: • Assist in securing an ongoing pipeline of new discoveries and help maintain Australia’s position as a major global mineral and energy exporter. • Determine the location, quantity and quality of groundwater resources to inform water management options, including infrastructure development and water banking. • Benefit the Mining Equipment, Technology and Services (METS) sector by drawing on private sector expertise in undertaking data acquisition and analysis.

The Exploring for the Future program is an initiative by the Australian Government dedicated to boosting investment in resource exploration in Australia. The initial phase of this program led by Geoscience Australia focussed on northern Australia to gather new data and information about the potential mineral, energy and groundwater resources concealed beneath the surface. The northern Lawn Hill Platform is an intracratonic poly-phased history region of Paleoproterozoic to Mesoproterozic age consisting of mixed carbonates, siliciclastics and volcanics. It is considered a frontier basin with very little petroleum exploration to date, but with renewed interest in shale and tight gas, that may present new exploration opportunities. An understanding of the geochemistry of the sedimentary units, including the organic richness, hydrocarbon-generating potential and thermal maturity, is therefore an important characteristic needed to understand the resource potential of the region. As part of this program, Rock-Eval pyrolysis analyses were undertaken by Geoscience Australia on selected rock samples from 2 wells of the northern Lawn Hill Platform.

This report presents key results from hydrogeological investigations at Alice Springs, completed as part of Exploring for the Future (EFTF)—an eight year, $225 million Australian Government funded geoscience data and information acquisition program focused on better understanding the potential mineral, energy and groundwater resources across Australia. The Southern Stuart Corridor (SSC) project area within the Northern Territory extends in a north–south corridor from Tennant Creek to Alice Springs, encompassing four water control districts and a number of remote communities. Water allocation planning and agricultural expansion in the SSC is currently limited by a paucity of data and information regarding the volume and extent of groundwater resources and groundwater systems more generally. This includes recharge rates, surface water –groundwater connectivity, and the dependency of ecosystems on groundwater. Outside the proposed agricultural areas, the project includes numerous remote communities where there is a need to secure water supplies. Geoscience Australia, in partnership with the Northern Territory Department of Environment and Natural Resources and the Power and Water Corporation, undertook an extensive program of hydrogeological investigations between 2017 and 2019. Data acquisition included helicopter airborne electromagnetic (AEM) and magnetic data, investigative groundwater bore drilling, ground-based and downhole geophysical data (including nuclear magnetic resonance for mapping water content and induction conductivity/gamma for defining geological formations), and hydrochemistry for characterising groundwater systems. This report investigates the hydrogeology across the Alice Springs focus area, which includes the Roe Creek and proposed Rocky Hill borefields, where five hydrostratigraphic units were mapped based on AEM interpretation and borehole geophysical information. The mapping supports the presence of a syncline, with a gentle parabolic fold axis that plunges westward, and demonstrates that the main Siluro-Devonian Mereenie Sandstone and Ordovician Pacoota Sandstone aquifers are continuous from Roe Creek borefield to the Rocky Hill area. Areas with the highest potential for recharge to the Paleozoic strata are where Roe Creek or the Todd River directly overlie shallow subcrop of the aquifer units. Three potential recharge areas are identified: (1) Roe Creek borefield, (2) a 3 km stretch of Roe Creek immediately west of the proposed Rocky Hill borefield, and (3) the viticulture block to the east of Rocky Hill. Analysis of groundwater chemistry and regional hydrology suggests that the rainfall threshold for recharge of the Paleozoic aquifers is ~125 mm/month, and groundwater isotope data indicate that recharge occurs rapidly. The groundwaters have similar major ion chemistry, reflecting similar geology and suggesting that all of the Paleozoic aquifers in the focus area are connected to some degree. Groundwater extraction at Roe Creek borefield since the 1960s has led to the development of a cone of depression and a groundwater divide, which has gradually moved eastward and is now east of the proposed Rocky Hill borefield. The majority of the groundwater within the focus area is of good quality, with <1000 mg/L total dissolved salts (TDS). The brackish water (7000 mg/L TDS) further to the east of the proposed Rocky Hill borefield warrants further investigation to determine the potential risk of it being captured by the cone of depression following the development of this borefield. This study provides new insight to the hydrogeological understanding of the Alice Springs focus area. Specifically, this investigation demonstrates that the Roe Creek and proposed Rocky Hill borefields, and a nearby viticulture area are all extracting from the same aquifer system. This finding will inform the future management and security of the Alice Springs community water supply. New groundwater resource estimates and a water level monitoring scheme can be developed to support the management of this vital groundwater resource.

Multiple geochronology and isotopic tracer datasets have been compiled at continental scale and visualised in map view. The compiled datasets include Sm-Nd model ages of magmatic rocks; Lu-Hf isotopes from zircon; Pb isotopes from ore-related minerals such as galena and pyrite; U-Pb ages of magmatic, metamorphic and sedimentary rocks; and K-Ar and 40Ar-39Ar ages from minerals and whole rocks. A variety of maps can be derived from these datasets, which we refer to as an Isotopic Atlas of Australia. This ‘atlas’ provides a convenient visual overview of age and isotopic patterns reflecting geological processes that have led to the current configuration of the Australian continent, including progressive development of continental crust from the mantle (Sm-Nd; Lu-Hf), chemical and isotopic evolution in the source regions for mineralising fluids (Pb-Pb), magmatic and high-grade metamorphic reworking of the crust (U-Pb), and cooling and exhumation of the mid-crust (K-Ar; 40Ar-39Ar). These datasets and maps unlock the collective value of several decades of geochronological and isotopic studies conducted across Australia, and provide an important complement to other geological maps and geophysical images—in particular, by adding a time dimension to 2D and 3D maps and models. <b>Citation: </b>Fraser, G.L., Waltenberg,K., Jones, S.L., Champion, D.C., Huston, D.L., Lewis, C.J., Bodorkos, S., Forster, M., Vasegh, D., Ware, B. and Tessalina, S., 2020. An Isotopic Atlas 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 report presents key results from the Howard East project conducted as part of Exploring for the Future (EFTF), an Australian Government funded geoscience data and information acquisition program. The four-year (2016–20) program focused on better understanding the potential mineral, energy and groundwater resources in northern Australia. Groundwater is an essential part of Darwin’s water supply and is sourced from the Koolpinyah Dolostone Aquifer (KDA) at the Howard East Borefield (HEB) and McMinns Borefield, which are ~25 km to 30 km southeast of Darwin. Previous work suggests that electrical conductivity anomalies observed in airborne electromagnetic (AEM) data within 5 km of HEB may be caused by saline groundwater within the KDA that is separated from HEB by dykes and other geological features that effectively compartmentalise the aquifer (Fell-Smith & Sumner, 2011; Tan et al., 2012). Nevertheless, concerns have grown that increased groundwater use may result in migration of saline groundwater toward HEB, which could compromise the groundwater resource. We collected groundwater chemistry including isotopes, time-series groundwater salinity, AEM, and induction and gamma data to better understand the complexities of the KDA. We show that groundwater in the KDA typically has a fresh Mg-Ca-HCO3 type composition, as is expected for a dolomitic aquifer. Highly saline Na-Cl type groundwater with a composition similar to seawater exists at some locations as well as groundwater with a mixed composition. These findings confirm previous interpretations for the area (e.g. Fell-Smith & Sumner, 2011). We sampled saline groundwater on the opposite side of two dolerite dykes to HEB to its northeast. Age dating results for this sample cannot be used to determine whether this saline groundwater represents relict seawater or whether groundwater at this site is in hydraulic connection with the modern ocean. Our groundwater chemistry results also show that saline intrusion is occurring northwest of HEB. AEM data were collected to better characterise geological and hydrogeological features in the area. Estimates of bulk conductivity of the subsurface were derived by inverting AEM data using both deterministic and stochastic methods. Using these AEM inversions and other hydrogeological information, we characterised high-conductivity anomalies within 5 km of HEB and the upper surface of unweathered dolerite in the two dykes northeast of HEB. We interpreted conductivity anomalies as pyritic shales, although drilling is required to investigate the salinity of groundwater in the KDA in this area. Where we were able to resolve the upper surface of unweathered material in the two dykes using the AEM, we found that it commonly occurs below sea level. Characterising the geometry of these dykes will aid in assessing their role in aquifer compartmentalisation. Our findings contribute to building a robust conceptual understanding of the KDA and will guide future investigations into the groundwater system. A number of other products exist for the EFTF Howard East project. The findings of this report are integrated with hydrodynamic analyses undertaken by Woltmann (in prep.) and reported in Haiblen et al. (2020). Hydrochemistry data presented here are contained in McGrath-Cohen et al. (2020), water level and salinity monitoring data can be found in Turner et al. (2020), AEM data are in Ray et al. (2020b), and induction and gamma data are in Tan et al. (2020).

This web service provides access to datasets generated by the North Australian Craton (NAC) Iron Oxide Copper Gold (IOCG) Mineral Potential Assessment. Two outputs were created: a comprehensive assessment, using all available spatial data, limiting data where possible to capture mineral systems older than 1500 ma, and; a coverage assessment, which is constrained to data that have no reliance on outcrop or age of mineralisation.

This web service provides access to datasets generated by the North Australian Craton (NAC) Iron Oxide Copper Gold (IOCG) Mineral Potential Assessment. Two outputs were created: a comprehensive assessment, using all available spatial data, limiting data where possible to capture mineral systems older than 1500 ma, and; a coverage assessment, which is constrained to data that have no reliance on outcrop or age of mineralisation.

This web service provides access to datasets generated by the North Australian Craton (NAC) Iron Oxide Copper Gold (IOCG) Mineral Potential Assessment. Two outputs were created: a comprehensive assessment, using all available spatial data, limiting data where possible to capture mineral systems older than 1500 ma, and; a coverage assessment, which is constrained to data that have no reliance on outcrop or age of mineralisation.

The magnetotelluric (MT) method is increasingly being applied to map tectonic architecture and mineral systems. Under the Exploring for the Future (EFTF) program, Geoscience Australia has invested significantly in the collection of new MT data. The science outputs from these data are underpinned by an open-source data analysis and visualisation software package called MTPy. MTPy started at the University of Adelaide as a means to share academic code among the MT community. Under EFTF, we have applied software engineering best practices to the code base, including adding automated documentation and unit testing, code refactoring, workshop tutorial materials and detailed installation instructions. New functionality has been developed, targeted to support EFTF-related products, and includes data analysis and visualisation. Significant development has focused on modules to work with 3D MT inversions, including capability to export to commonly used software such as Gocad and ArcGIS. This export capability has been particularly important in supporting integration of resistivity models with other EFTF datasets. The increased functionality, and improvements to code quality and usability, have directly supported the EFTF program and assisted with uptake of MTPy among the international MT community. <b>Citation:</b> Kirkby, A.L., Zhang, F., Peacock, J., Hassan, R. and Duan, J., 2020. Development of the open-source MTPy package for magnetotelluric data analysis and visualisation. 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.