To be technically viable, a geothermal energy prospect has two requirements: sufficiently high temperatures at economically-accessible depths; and a viable reservoir from which to extract the heat by flowing fluid at a suitable rate. In recent years, Geoscience Australia (GA) has applied conductive thermal modelling to 3D geological maps to improve predictive targeting of elevated temperatures in the Australian crust. GA is developing capability to improve targeting of favourable reservoir characteristics, using a combination of geothermal modelling techniques, and the use of geophysical and other geoscience data. GA's assessments of crustal temperature potential have incorporated temperature measurements, heat flow data, thermal conductivity measurements and heat production estimates based on geochemistry data. They have also incorporated other datasets such as outcrop geology, drillhole intersections, seismic and gravity data. GA's initial assessment of North Queensland was qualitative and based on a 2D GIS approach. Subsequent assessments were quantitative and based on 3D thermal models, however, due to computational restrictions; uncertainty in the temperature predictions was assessed only qualitatively. More recently, thermal modelling was conducted on a 3D geological map of the Cooper Basin region in South Australia and Queensland (Meixner et al., 2012) using the SHEMAT software (Clauser, 2003). Uncertainty in the temperature predictions was estimated via a Monte-Carlo based approach using the National Computational Infrastructure (NCI) at the Australian National University. The second requirement for a viable geothermal energy prospect is reservoir potential. GA is developing capability to identify reservoir potential using two related approaches. The first involves use of the TOUGH2-MP reservoir modelling code on the NCI. This code will be used to simulate fluid-flow in synthetic geothermal reservoirs with varying geometries and permeability structures, to identify the most desirable characteristics. The second approach involves application of geophysical methods to improve predictive targeting of geothermal reservoirs. GA has used numerical modelling techniques to improve predictive targeting of elevated crustal temperatures and is now building capability to assist predictive targeting of favourable reservoir characteristics. This will allow new geothermal targets to be identified based on the two geological requirements for a successful geothermal prospect. By applying this approach on a national scale, GA will be able to provide an integrated, Australia-wide assessment of geothermal potential. Clauser, C. (ed.), 2003. Numerical Simulation of Reactive Flow in Hot Aquifers: SHEMAT and Processing SHEMAT. Springer-Verlag: Berlin Heidelberg. Meixner, A.J., Kirkby, A.L., Lescinsky, D.T., and Horspool, N., 2012b. The Cooper Basin 3D Map Version 2: Thermal modelling and temperature uncertainty. Record 2012/60. Geoscience Australia: Canberra.

The Australian Geothermal Association compiled data on the installed capacity of direct-use geothermal and geoexchange systems in Australia, including large-scale ground source heat pumps and hot sedimentary applications through to December 2018. Large-scale direct-use hot sedimentary aquifer systems includes systems to heat swimming pools or provide hydronic heating systems. In geoexchange systems, the Earth acts as a heat source or a heat sink, exploiting the temperature difference between the surface (atmosphere) and at depth. The temperature of the Earth just a few metres below the surface is much more consistent than atmospheric temperature, especially in seasonal climates. These resources do not require the addition of geothermal heat.

The Geoscience Australia Rock Properties database stores the result measurements of scalar and vector petrophysical properties of rock and regolith specimens and hydrogeological data. Oracle database and Open Geospatial Consortium (OGC) web services. Links to Samples, Field Sites, Boreholes. <b>Value:</b> Essential for relating geophysical measurements to geology and hydrogeology and thereby constraining geological, geophysical and groundwater models of the Earth <b>Scope:</b> Data are sourced from all states and territories of Australia

The collection includes 17,247 measurements of temperature and temperature gradients collected down 5513 individual wells. This information formed the basis for the 'OZTemp Interpreted Temperature at 5km Depth' image of Australia <b>Value: </b>These observations are used to assess heat flow which can be used to infer deep geologic structure, which is valuable for exploration and reconstructions of Australia's evolution <b>Scope: </b>Nationwide collection corresponding to accessible boreholes and published measurements

Heat flow data across Australia are sparse, with around 150 publicly-available data-points. The heat flow data are unevenly distributed and mainly come from studies undertaken by the Bureau of Mineral Resources (BMR) and the Research School Earth Sciences at the Australian National University in the 1960s and 1970s. Geoscience Australia has continued work started under the federally-funded Onshore Energy Security Program (OESP), collecting data to add to the heat flow coverage of the continent. This report presents temperature, natural gamma and thermal conductivity data for eight boreholes across Australia. Temperature logging was performed down hole with temperatures recorded at intervals less than 20 cm. Samples of drill core were taken from each well and measured for thermal conductivity at Geoscience Australia. One dimensional, conductive heat flow models for the boreholes are presented here. These new determinations will add to the 53 already released by Geoscience Australia under the OESP, totalling 61 determinations added to the Australian continental heat flow dataset since 2007.

The Australian Geothermal Association compiled data on the installed capacity of direct-use geothermal and geoexchange systems in Australia, including large-scale ground source heat pumps and hot sedimentary applications through to December 2018. Large-scale direct-use hot sedimentary aquifer systems includes systems to heat swimming pools or provide hydronic heating systems. In geoexchange systems, the Earth acts as a heat source or a heat sink, exploiting the temperature difference between the surface (atmosphere) and at depth. The temperature of the Earth just a few metres below the surface is much more consistent than atmospheric temperature, especially in seasonal climates. These resources do not require the addition of geothermal heat.

<div>Diamond exploration over the past decade has led to the discovery of a new province of kimberlitic pipes (the Webb Province) in the Gibson Desert of central Australia. The Webb pipes comprise sparse macrocrystic olivine set in a groundmass of olivine, phlogopite, perovskite, spinel, clinopyroxene, titanian-andradite and carbonate. The pipes resemble ultramafic lamprophyres (notably aillikites) in their mineralogy, major and minor oxide chemistry, and initial 87Sr/ 86Sr and <em>ε</em>Nd-<em>ε</em>Hf isotopic compositions. Ion probe U-Pb geochronology on perovskite (806 ± 22 Ma) indicates the eruption of the pipes was co-eval with plume-related magmatism within central Australia (Willouran-Gairdner Volcanic Event) associated with the opening of the Centralian Superbasin and Rodinia supercontinent break-up. The equilibration pressure and temperature of mantle-derived garnet and chromian (Cr) diopside xenocrysts range between 17 and 40 kbar and 750–1320°C and define a paleo-lithospheric thickness of 140 ± 10 km. Chemical variations of xenocrysts define litho-chemical horizons within the shallow, middle, and deep sub-continental lithospheric mantle (SCLM). The shallow SCLM (50–70 km), which includes garnet-spinel and spinel lherzolite, contains Cr diopside with weakly refertilized rare earth element compositions and unenriched compositions. The mid-lithosphere (70–85 km) has lower modal abundances of Cr diopside. This layer corresponds to a seismic mid-lithosphere discontinuity interpreted as pargasite-bearing lherzolite. The deep SCLM (&gt;90 km) comprises refertilized garnet lherzolite that was metasomatized by a silicate-carbonatite melt.</div><div><br></div><div>Geoscience Australia’s Exploring for the Future program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.</div><div><br></div><div><strong>Citation:</strong></div><div>Sudholz, Z. J., et al. (2023). Petrology, age, and rift origin of ultramafic lamprophyres (aillikites) at Mount Webb, a new alkaline province in Central Australia. <i>Geochemistry, Geophysics, Geosystems</i>, 24, e2023GC011120.</div><div>https://doi.org/10.1029/2023GC011120</div>

The Australian Geothermal Association compiled data on the installed capacity of direct-use geothermal and geoexchange systems in Australia, including large-scale ground source heat pumps and hot sedimentary applications through to December 2018. Large-scale direct-use hot sedimentary aquifer systems includes systems to heat swimming pools or provide hydronic heating systems. In geoexchange systems, the Earth acts as a heat source or a heat sink, exploiting the temperature difference between the surface (atmosphere) and at depth. The temperature of the Earth just a few metres below the surface is much more consistent than atmospheric temperature, especially in seasonal climates. These resources do not require the addition of geothermal heat.

<div>The lithology, geochemistry, and architecture of the continental lithospheric mantle (CLM) underlying the Kimberley Craton of north-western Australia has been constrained using pressure-temperature estimates and mineral compositions for &gt;5,000 newly analyzed and published garnet and chrome (Cr) diopside mantle xenocrysts from 25 kimberlites and lamproites of Mesoproterozoic to Miocene age. Single-grain Cr diopside paleogeotherms define lithospheric thicknesses of 200–250 km and fall along conductive geotherms corresponding to a surface heat flow of 37–40 mW/m 2. Similar geotherms derived from Miocene and Mesoproterozoic intrusions indicate that the lithospheric architecture and thermal state of the CLM has remained stable since at least 1,000 Ma. The chemistry of xenocrysts defines a layered lithosphere with lithological and geochemical domains in the shallow (&lt;100 km) and deep (&gt;150 km) CLM, separated by a diopside-depleted and seismically slow mid-lithosphere discontinuity (100–150 km). The shallow CLM is comprised of Cr diopsides derived from depleted garnet-poor and spinel-bearing lherzolite that has been weakly metasomatized. This layer may represent an early (Meso to Neoarchean?) nucleus of the craton. The deep CLM is comprised of high Cr2O3 garnet lherzolite with lesser harzburgite, and eclogite. The peridotite components are inferred to have formed as residues of polybaric partial mantle melting in the Archean, whereas eclogite likely represents former oceanic crust accreted during Paleoproterozoic subduction. This deep CLM was metasomatized by H2O-rich melts derived from subducted sediments and high-temperature FeO-TiO2 melts from the asthenosphere.</div><div><br></div><div>Geoscience Australia’s Exploring for the Future program provides precompetitive information to inform decision-making by government, community and industry on the sustainable development of Australia's mineral, energy and groundwater resources. By gathering, analysing and interpreting new and existing precompetitive geoscience data and knowledge, we are building a national picture of Australia’s geology and resource potential. This leads to a strong economy, resilient society and sustainable environment for the benefit of all Australians. This includes supporting Australia’s transition to net zero emissions, strong, sustainable resources and agriculture sectors, and economic opportunities and social benefits for Australia’s regional and remote communities. The Exploring for the Future program, which commenced in 2016, is an eight year, $225m investment by the Australian Government.</div><div><br></div><div><strong>Citation:</strong></div><div>Sudholz, Z.J., et al. (2023) Mapping the Structure and Metasomatic Enrichment of the Lithospheric Mantle Beneath the Kimberley Craton, Western Australia,&nbsp;<em><i>Geochemistry, Geophysics, Geosystems</i>,</em>&nbsp;24, e2023GC011040.</div><div>https://doi.org/10.1029/2023GC011040</div>

3D constrained gravity inversions have been applied to gravity data in the Cooper Basin region of South Australia to delineate low density regions within the basement, beneath thick sequences of sedimentary cover. The low density regions, which are interpreted as granite bodies, may act as heat sources beneath thermally insulating sediments, thereby enhancing geothermal prospectivity. The Cooper Basin is the site of Australia's first geothermal project , where elevated crustal temperatures result from high-heat producing granites of the Big Lake Suite beneath the basin sediments. A 3D map of sediment stratigraphy was populated with densities and used to constrain the contribution of low density cover sediments to the observed gravity field. The resulting constrained density inversion model produced low density regions in the basement that coincide with local gravity lows. Further gravity inversions were generated and combined with gravity worm data to constrain the lateral and vertical extent of these discrete low density regions which we interpret as granite bodies. These Interpreted Granite Bodies (IGBs) coincide with granites intersected in wells. Analyses of a regional thermal model generated for a previous study, indicate that extra heat-production is required in the regions of the model that coincide with a number of the IGBs. Further thermal modelling was undertaken to determine the heat production differential between these high-heat producing IGBs and the surrounding basement. Two regions were identified where the high-heat producing IGBs are located beneath thick sequences of thermally insulating sediments. These regions, located to the east of the Big Lake Suite granodiorite and in the centre of the study area coinciding with the Barrolka gravity low, are considered to have high geothermal prospectivity.