Hot Rocks in Australia - National Outlook Hill, A.J.1, Goldstein, B.A1 and Budd, A.R.2 goldstein.barry@saugov.sa.gov.au hill.tonyj@saugov.sa.gov.au Petroleum & Geothermal Group, PIRSA Level 6, 101 Grenfell St.Adelaide SA 50001 Anthony.Budd@ga.gov.au Onshore Energy & Minerals Division, Geoscience Australia, GPO Box 378 Canberra ACT 26012 Abstract: Evidence of climate change and knowledge of enormous hot rock resources are factors stimulating growth in geothermal energy research, including exploration, proof-of-concept appraisals, and development of demonstration pilot plant projects in Australia. In the six years since the grant of the first Geothermal Exploration Licence (GEL) in Australia, 16 companies have joined the hunt for renewable and emissions-free geothermal energy resources in 120 licence application areas covering ~ 67,000 km2 in Australia. The associated work programs correspond to an investment of $570 million, and that tally excludes deployment projects assumed in the Energy Supply Association of Australia's scenario for 6.8% (~ 5.5 GWe) of Australia's base-load power coming from geothermal resources by 2030. Australia's geothermal resources fall into two categories: hydrothermal (from relatively hot groundwater) and the hot fractured rock i.e. Enhanced Geothermal Systems (EGS). Large-scale base-load electricity generation in Australia is expected to come predominantly from Enhanced Geothermal systems. Geologic factors that determine the extent of EGS plays can be generalised as: - source rock availability, in the form of radiogenic, high heat-flow basement rocks (mostly granites); - low thermal-conductivity insulating rocks overlying the source rocks, to provide thermal traps; - the presence of permeable fabrics within insulating and basement rocks, that can be enhanced to create heat-exchange reservoirs; and - a practical depth-range, limited by drilling and completion technologies (defining a base) and necessary heat exchange efficiency (defining a top). A national EGS resource assessment and a road-map for the commercialisation of Australia's EGSs are expected to be published in 2008. The poster will provide a synopsis of investment frameworks and geothermal energy projects underway and planned in Australia.

During 2009-2011 Geoscience Australia completed a petroleum prospectivity study of the offshore northern Perth Basin. Basement is deep and generally not resolved in the reflection seismic data. Recent improvements to the magnetic ship-track database and magnetic anomaly grid allowed an assessment of depth to magnetic sources and estimation of sediment thickness, providing new insight into basement depth and trends. 2D models along several seismic transects and analysis using spectral methods indicate that penetration of the lower sediments by high susceptibility bodies is probable. The reflection seismic evidence for these bodies is not clear, though in some cases they may be associated with faults and structural highs. Where the modelled bodies penetrate the sediments, they are mostly below or within Permian strata, except in the west of the strudy area. A moderate positive magnetic anomaly (the Turtle Dove Ridge) is modelled by massive bodies whose tops are 5-15 km below sea floor. The depth to magnetic basement map highlights sub-basins and structural highs within the northern Perth Basin, with up to 12 km of sediment in the Zeewyck sub-basin.

Expedition 369 planned for September 2017 will drill several holes on the Naturaliste Plateau and the adjacent Mentelle Basin off southwest Australia. The unique tectonic and paleoceanographic setting of this region offers an outstanding opportunity to investigate a range of scientific issues of global importance, especially rapid climate change during the onset of the Cretaceous hot greenhouse. Equally fascinating and poorly documented is the sedimentary, tectonic and geodynamic history of the region. Expedition 369 provides a unique opportunity to study how the Earth's climate and oceans responded to elevated levels of atmospheric CO2 and the role of local tectonic events in the onset of anoxic conditions.

Abstract submitted to the 35th International Geological Congress, 27 August - 4 September 2016 Cape Town, South Africa. Deep seismic reflection profiling, combined with forward modelling of gravity data, lend strong support to the idea that the Paleo- to Mesoproterozoic Mount Isa mineral province comprises three vertically stacked and partially inverted sedimentary basins preserving a record of intracontinental rifting followed by passive margin formation.

The geology of the southern Thomson Orogen is poorly understood due to extensive cover of Mesozoic and Cenozoic sedimentary basins and regolith. Small outcrops of the southern Thomson Orogen are exposed along the Eulo Ridge (south Qld) and in the southwest near Tibooburra (NSW). Cover is of varying thickness and overlies a pre-Cretaceous-age palaeotopography with much greater relief than the present-day landscape. Proximal to these regions the thickness of cover is estimated to be < 200 m, which is within current economic exploration and mining depths. The southern Thomson Orogen is true 'greenfields' country. Although the mineral potential of the region is largely unknown, the north-eastern Thomson Orogen is well mineralised (e.g., Thalanga and Charters Towers), as is the Koonenberry region to the southwest (e.g., Tibooburra and Milparinka) and the Lachlan Orogen to the south (e.g., Cadia and Cobar). In order to encourage exploration investment in the southern Thomson Orogen, Geoscience Australia (GA), the Geological Survey of Queensland (GSQ) and the Geological Survey of New South Wales (GSNSW) have commenced a three-year collaborative project (the Southern Thomson Orogen Project - STOP) to synthesise existing and collect new pre-competitive geoscience data. The first stage of the project has synthesised existing geology and geophysics (magnetic, gravity and seismic data) to produce a new, seamless solid geological map of the Paleozoic basement across the state border. This is supported by the collection of new isotopic age dating samples from industry drill holes in the region to assess magmatic, metamorphic and mineralisation ages. These new samples will also be used to assess the potential mineral systems present in the southern Thomson Orogen, the prospectivity of the region and to conduct a gap analysis. Secondly, new surface geochemical samples have been collected over the Eulo Ridge to complement other low sampling density samples collected by the Cooperative Research Centre for Landscape Environments and Mineral Exploration (CRC LEME) and as part of the National Geochemical Survey of Australia (NGSA). Early results from these samples highlight the use of surface samples and weak acid digestion to map the distal dispersion footprints of large mineralisation systems and bedrock terrains. The third stage of the project is to collect new geophysical data across the region to assess the depth of cover over the Eulo Ridge and to map lithospheric architecture. This involves collecting new airborne electromagnetic (AEM), gravity and magnetotelluric (MT) data. To date, 4267 line kilometres of new AEM data have been collected in the area. Over the Eulo Ridge, 3352 line kilometres was collected as a regional survey with east-west flight lines of 5000 m line spacing. This survey was designed to map the basement-cover interface across the Eulo Ridge, map basement geological units and potentially locate conductive targets in the basement. Two AEM traverses were also collected: from Gongolgon (NSW) to Thargomindah (Qld); and from Louth (NSW) to Eulo (Qld), of 915 total line kilometres. These two traverses are complemented by the acquisition of ~3550 new gravity stations at 333 m station spacing and ~200 new broadband MT stations at 5 km station spacing (in progress November - December 2014). The combined AEM, gravity and MT datasets will be used to model the lithospheric architecture of the southern Thomson Orogen and to reassess the Thomson Orogen-Lachlan Orogen boundary. A program of detailed audio frequency MT (AMT) acquisition is also underway to map geological structures across the Eulo Ridge in Queensland. The combined results will be synthesised and integrated into a precompetitive geoscience data package to encourage exploration investment. Interim products and datasets will be released throughout the project, with the final results delivered to industry in 2016.

description of lithospheric architecture of the Yilgarn Cratom

The chemical and isotopic composition of volatiles trapped in fluid inclusions provides valuable information in the formation and evolution of not only natural gases, but also sedimentary basin's fluid history. However, one of the critical issues is the difficult process in determining the isotopic composition of inclusion gases. This is mainly due to the low concentrations of gas components in the inclusions and lack of reliable process to extract and pre-concentrate the trace gas components without isotopic fractionation. Recently, the carbon isotopic compositions of fluid inclusion gases were measured in-line using an EA-IRMS and a GC-IRMS. In this study we use a hydraulic pressure crusher cell in line with a GC-IRMS. The system is designed to crush (routinely at 2500 psi) up to 2g rock samples (>0.3mm) to give a grain size distribution with a sub-micron tail, effectively decrepitating a high proportion of the fluid inclusions.

Short abstract for Australian Earth Sciences Convetion 2016

The Geological Survey of South Australia (GSSA) routinely collects regional gravity and aeromagnetic data as well as archiving company data. These datasets provide a useful starting point for explorers but a lot more information can be extracted from existing potential field data. This will lead us to a better understanding of crustal architecture and mineral systems.

Abstract for 2015 Conference of the Specialist Group of Tectonics and Structural Geology. Presentation of 3D Models in the Grampians-Stavely Zone, western Victoria. 3D geological models have been produced for two major geological units in the Grampians-Stavely Structural Zone in western Victoria. The Grampians-Stavely Zone is located on the eastern limit of the Cambrian-aged Delamerian Orogen in Victoria (VandenBerg et al., 2000; Crawford et al., 2003; Miller et al., 2005) and several belts of Cambrian igneous rocks with arc affinities have been recognised within this zone (Crawford and Keays, 1978; Buckland, 1987; VandenBerg et al., 2000; Crawford et al., 2003); including the exposed Mount Stavely Volcanic Complex (Buckland, 1987). The Mount Stavely Volcanic Complex, together with other belts of Cambrian igneous rocks, have been interpreted as fault slices of a now mostly buried magmatic arc system referred to as the Stavely Arc (Schofield et al., 2015; Cayley et al., in prep.). In order to address the outstanding geological questions and challenges to exploration in the Grampians-Stavely Zone, Geoscience Australia and the Geological Survey of Victoria established the collaborative Stavely Project in 2013. The Stavely Project forms part of the broader UNCOVER initiative (Australian Academy of Science, 2012) and aims to provide the fundamental framework for discovery in the Grampians-Stavely Zone. This is done using a mineral systems-based approach (Wyborn et al., 1994) through the provision of pre-competitive geoscientific data. This approach involves characterising the subsurface geology, recognising favourable geological environments for the formation of major mineral systems, identifying important elements that demonstrate mineral systems potential, and understanding the depth and nature of cover across the region. This study will focus on understanding the depth and nature of specific cover units across the region.