High-grade gold (Au), copper (Cu) and bismuth (Bi) ores in the Tennant Creek goldfield have been mined from hydrothermal magnetite and/or hematite-rich ironstone bodies. Less well known is a style of Au-Cu-Bi mineralisation hosted by quartz vein systems within shear zones outside ironstones. Sensitive High Resolution Ion Micro Probe (SHRIMP) U-Pb-Th analyses of hydrothermal monazite [(LREE)PO4] associated with this mineralisation style at the Orlando East Au-Cu-Bi deposit and Navigator 6 Au prospect yield ages of 1659 ± 13 Ma and 1659 ± 15 Ma, respectively. These ages are nearly 200 million years younger than the age established from ironstone-hosted ores in the district. This new result widens the exploration ‘search space’ for gold into rock formations previously regarded as too young to host this style of mineralisation. <b>Citation:</b> Skirrow, R.G., Cross, A.J., Magee, C.W., Lecomte, A., and Mercadier, J., 2020. Identification of a new ca. 1660 Ma Au-Cu-Bi metallogenic event at Tennant Creek. 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.

One of the aims of the Exploring for the Future program is to promote the discovery of new mineral deposits in undercover frontiers. Iron oxide–copper–gold mineral systems are a desirable candidate for undercover exploration, because of their potential to generate large deposits with extensive alteration footprints. This mineral potential assessment uses the mineral systems concept: developing mappable proxies of required theoretical criteria, combined to demonstrate where conditions favourable for mineral deposit formation are spatially coincident. This assessment uses a 2D geographical information system workflow to map the favourability of the key mineral system components. Two outputs were created: a comprehensive assessment, using all available spatial data; and a coverage assessment, which is constrained to data that have no reliance on outcrop. The results of these assessment outputs were validated with spatial statistics, demonstrating how the assessment can predict the presence of known ore deposits. Both assessment outputs present new areas of interest with prospectivity in under-explored regions of undercover northern Australia. The intended aims are already being realised, as this tool has aided area selection for pre-competitive stratigraphic drilling as part of the MinEx CRC National Drilling Initiative. <b>Citation:</b> Murr, J., Skirrow, R.G., Schofield, A., Goodwin, J., Coghlan, R., Highet, L., Doublier, M.P., Duan, J. and Czarnota, K., 2020. Tennant Creek – Mount Isa IOCG mineral potential assessment. 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.

Water, energy and mineral resources are vital for Australia’s economic prosperity and sustainable development. However, continued supply of these resources cannot be taken for granted. It is widely accepted that the frontier of exploration now lies beneath the Earth’s surface, making characterisation of the subsurface a unifying challenge. Between 2016 and 2020, the $100.5 million Exploring for the Future program focused on addressing this challenge across northern Australia in order to better define resource potential and boost investment. The program applied a multiscale systems approach to resource assessment based on characterisation of the Australian plate from the surface down to its base, underpinned by methodological advances. The unprecedented scale and diversity of new data collected have resulted in many world-first achievements and breakthrough insights through integrated systems science. Through this multi-agency effort, new continental-scale datasets are emerging to further enhance Australia’s world-leading coverage. The program has identified prospective regions for a wide range of resources and pioneered approaches to exploration undercover that can be applied elsewhere. The outcomes so far include extensive tenement uptake for minerals and energy exploration in covered terranes, and development of informed land-management policy. Here, we summarise the key scientific achievements of the program by reviewing the main themes and interrelationships of 62 contributions, which together constitute the Exploring for the Future: extended abstracts volume. <b>Citation:</b> Czarnota, K., Roach, I.C., Abbott, S.T., Haynes, M.W., Kositcin, N., Ray, A. and Slatter, E., 2020. Exploring for the Future: advancing the search for groundwater, energy and mineral resources. 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.

Mafic igneous rocks are thought to be an important source of metals for the ca. 1640–1595 Ma sediment-hosted base metal deposits in the Paleo- to Mesoproterozoic Mount Isa – McArthur Basin system of northern Australia. Such rocks are widespread—the voluminous rift-related mafic magmatism at ca. 1790–1775 Ma and ca. 1730–1710 Ma—and show local evidence for intense hydrothermal alteration and metal leaching. To better constrain the nature, degree, and regional and temporal extent of alteration and metal leaching in these rocks, we have undertaken regional sampling of mafic igneous units from available drillcore, for geochemistry, stable isotopes and petrological examination. Sampling focused on magmatism of both ages in the southeastern MacArthur Basin, complementing the extensive pre-existing data for the Mount Isa region. Alteration in the mafic igneous rocks of the southeastern McArthur Basin ranges from mildly to strongly chloritic in the older units to strongly potassic (K-feldspar–chlorite–hematite) in the younger units. The latter alteration is ubiquitous, well developed and characterised by strong K2O enrichment and extreme depletion in CaO and Na2O. Geochemical data show that this intense and pervasive potassic alteration extends to similar-aged mafic rocks in the western Mount Isa region. Metal leaching is present in both alteration types, with strong Cu and Pb depletion in the most chlorite-altered rocks, and Zn and Cu depletion in the potassic alteration. Our oxygen isotope data for these mafic rocks (of both ages) in the southeastern McArthur Basin show a limited range of values (δ18O of 6–10‰) that are negatively correlated with K2O content. Our values are significantly lighter than published data for similar igneous rocks to the west, and indicate either a temperature zonation (ca. 250 °C in the east versus ca. 100 °C in the west; preferred) and/or different fluids. Results from our geochemical forward modelling indicate the requirement for exogenous K2O to produce the observed potassic alteration. The most likely source of this K was saline brines, consistent with the interpreted lacustrine and/or evaporitic environments for much of the McArthur Basin. Timing of alteration is uncertain, and the alteration may have included diagenetic low-temperature local K-rich brines and younger higher-temperature deep basinal brines. The temporal and geographically restricted nature of the potassic alteration, however, suggests restriction of K-rich, bittern evaporitic brine production in the younger and inboard parts of the Mount Isa – McArthur Basin system. Our results provide insights that directly relate to the genesis and exploration of basin-hosted Zn-Pb and Cu-Co mineral systems. They confirm that mafic igneous rocks in the region have lost significant amounts of both Zn and Cu, many times more than required for known deposits. The study also shows that metal leaching was accompanied by magnetite-destructive alteration. Hence, identifying zones of metal leaching may be possible using inversions of geophysical data, which may assist in targeting exploration. <b>Citation:</b> Champion, D.C., Huston, D.L., Bastrakov, E., Siegel, C., Thorne, J., Gibson, G.M. and Hauser, J., 2020. Alteration of mafic igneous rocks of the southern McArthur Basin: comparison with the Mount Isa region and implications for basin-hosted base metal deposits. 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.

Mineral exploration ideally involves researching geological potential within the constraints of economic feasibility. Nevertheless, explicit consideration of economic factors is often delayed until late in the exploration cycle. This is not ideal. Like mineral prospectivity, projected economic feasibility can be used to refine the search space and thereby reduce the risks associated with mineral exploration undercover. Here, we outline an exploration strategy based on the notion of identifying economic fairways—that is, regions permissive to resource development from an economic perspective. The approach appraises the economics of Au, Cu, Ni, Pb, Zn, potash and phosphate deposits by modelling revenue against capital expenditure (such as the costs of employment, mining overburden and access to infrastructure). We demonstrate the economic fairways approach through regional assessment of a Tennant Creek–style iron oxide–copper–gold deposit across northern Australia. Our results indicate that such a mineral deposit is expected to be economically viable across much of northern Australia, including in areas with several hundreds of metres of overburden. Our analysis sheds light on the need for accurate cover thickness models, without which undercover economic fairways cannot be defined. Our online tool benefits mineral explorers, and also helps to inform investors about the relative strengths of potential mineral projects; policy makers could use it to plan regional infrastructure development in frontier mineral provinces. <b>Citation:</b> Haynes, M.W., Walsh, S.D.C., Czarnota, K., Northey, S.A. and Yellishetty, M., 2020. Economic fairways assessments across northern 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 Record presents new zircon U–Pb geochronological data, obtained via Sensitive High Resolution Ion Microprobe (SHRIMP) for six samples of volcanic and intrusive rocks from the Cobar Basin, NSW. The work is part of an ongoing Geochronology Project, conducted by the Geological Survey of New South Wales (GSNSW) and Geoscience Australia (GA) under a National Collaborative Framework (NCF) agreement, to better understand the geological evolution and mineralisation history of the Cobar Basin. The results herein correspond to zircon U–Pb SHRIMP analysis undertaken by the GSNSW-GA Geochronology Project during the July 2018 – June 2019 reporting period.

<div><strong>Output Type:</strong> Exploring for the Future Extended Abstract</div><div><br></div><div><strong>Short Abstract: </strong>An advanced understanding of regional-scale metallogenic characteristics and ore-formation controls is fundamental for mineral discovery, particularly in underexplored covered terranes, such as the Delamerian Orogen of southeastern Australia. The Delamerian Orogen is defined as the spatial extent of rocks first deformed by the Delamerian Orogeny, though the Orogen was also affected by younger geodynamic events. Petrology of the mineralised host rocks from over 20 mineral prospects and deposits has led to the recognition of four types of mineral systems related to the geodynamic history of the Delamerian Orogen on mainland Australia, including (1) porphyry-epithermal; (2) volcanic-hosted massive sulphide (VHMS); (3) orogenic gold; and (4) mafic-ultramafic magmatic Cu-Ni-PGE systems. Several other prospects are yet to be classified due to insufficient data, although there is strong evidence to suggest that these are magmatic-hydrothermal in origin. Direct dating of hydrothermal alteration and mineralisation at key mineral deposits and prospects (using U-Pb in titanite and apatite, and Sm-Nd in fluorite) identified four major metallogenic events in the Delamerian Orogen margin. The middle to late Cambrian (505–494 Ma) mineral systems, throughout the eastern margin of the Delamerian Orogen, are potentially the most significant. However, our new dating indicates other metallogenic events at 590–580 Ma, 480–460 Ma, and 412–399 Ma. Analysis of data related to mineral systems fertility reveals crustal controls on the location and type of mineralisation in the Delamerian Orogen. Integration of Hf and O isotopes in zircon, and S isotopes in sulphide minerals indicates that the geology of the Orogen may host multiple opportunities for mineral system development. An indicative map of ca.600–400 Ma mineral system potential was developed by integrating this new data, together with other geological, geochemical and geophysical datasets within the geodynamic context of the Delamerian Orogen. Importantly, this study demonstrates the metallogenic characteristics of multiple types and episodes of mineral system development, and the geological processes that have controlled their formation to aid exploration.</div><div><br></div><div><strong>Citation: </strong>Cheng, Y., Gilmore, P., Lewis, C., Roach, I., Clark, A., Mole, D., Pitt, L., Doublier, M., Sanchez, G., Schofield, A., O'Rourke, A., Budd, A., Huston, D., Czarnota, K., Meffre, S., Feig, S., Maas, R., Gilbert, S., Cairns, C., Cayley, R., Wise, T., Wade, C., Werner, M., Folkes, C. &amp; Hughes, K., 2024. Mineral systems and metallogeny of the Delamerian Orogen margin. In: Czarnota, K. (ed.) Exploring for the Future: Extended Abstracts. Geoscience Australia, Canberra. https://doi.org/10.26186/149657</div><div><br></div>