Geochemical and reactive transport simulations of S.A. palaeochannel/sandstone hosted uranium systems. predictive mineral discovery CRC - PIRSA Numerical Modelling Projects Update #5

Structural architecture, 3D modelling and target generation in the Lawn Hill Platform, Queensland, Project G14 Final report

Project G15 Final Report Sunrise Dam Gold Mine Geological Study Project Geological Study Project

Work conducted at the Bureau of Mineral Resources (now Geoscience Australia) in the early 1990s was instrumental in bringing hot rocks geothermal research and development to Australia. Following the announcement of the Australian Government's Energy Initiative in August 2006, a new geothermal project has been started at Geoscience Australia. This paper, presented at 3rd Hot Rock Energy Conference in Adelaide, August 2007, outlines the scope of the Onshore Energy Security Program and the development, implementation and progress to date of the Geothermal Energy Project.

This paper aims to present an overview of mineral exploration highlights and hotspots in Australia for 2007. Presented at the Association of Mining and Exploration Companies National Mining Congress 7-9 June 2007, Perth Convention Centre, Western Australia.

Paper presented at the Association of Mining and Exploration Companies (AMEC) National Mining Congress 2007, 7-8 June 2007, Perth Convention Centre, Western Australia. Ore deposits of Proterozoic age account for more than 90% of Australia's known iron ore, uranium and lead resources, most of Australia's known zinc (84%) and copper (71%) resources, and significant gold (17%) resources. Most of these deposits were formed by mineralising systems in the period 2000-1500 Ma, with the most fertile being the period 1690-1500 Ma. Recent Geoscience Australia regional projects conducted under the National Geoscience Agreement with State and NT partners have brought new understanding to the controls on distribution of these deposits.

Geologic observations suggest two stages of hydrothermal activity at a number of presently subeconomic iron oxide copper-gold systems in the Olympic Dam district, eastern Gawler craton. They contain high-, and moderate- to low-temperature Fe oxide-rich hydrothermal alteration. The mineral assemblages include magnetite-calc-silicate-alkali feldspar ± Fe-Cu sulfides and hematite-sericite-chlorite-carbonate ± Fe-Cu sulfides ± U, REE minerals. In all documented prospects, the minerals of the hematitic assemblages replace the minerals of the magnetite-rich assemblages. The bulk of the subeconomic Cu-Au mineralization is associated with the hematitic alteration assemblages. Microanalysis by proton ion probe (PIXE) of hypersaline fluid inclusions in magnetite-rich assemblages, however, demonstrates that significant amounts of copper (>500 ppm) were transported by the early-stage high-temperature (>400C) fluids responsible for the magnetite-rich alteration. These brine inclusions contain multiple solid phases (liquid + vapor + multiple solids) including chalcopyrite in some cases. In comparison, inclusions of the hematitic stage are relatively simple liquid + vapor types, with homogenization temperatures of 200C to 300C and containing 1 to 8 wt percent NaCl equiv. The Br/Cl ratios of the magnetite-forming fluids measured by PIXE lie beyond the range of typical magmatic and/or mantle values, allowing for the possibility that the fluids originated as brines from a sedimentary basin or the crystalline basement. Sulfur isotope compositions of chalcopyrite and pyrite demonstrate that sulfur in both alteration assemblages was derived either from cooling magmas and/or crystalline igneous rocks carried by relatively oxidized fluids ({sum}SO42- {approx} {sum} H2S, {delta}34Ssulfides from +5 to +2{per thousand}) or from crustal sedimentary rocks ({delta}34Ssulfides from +5 to +10{per thousand}). Oxygen and hydrogen isotope compositions of waters calculated for minerals of the magnetite-rich assemblage have {delta}18O values of +7.7 to +12.8 per mil and {delta}D values of +15 to +21 per mil. The only available {delta}18O and {delta}Dfluid values for the hematitic assemblage are +4.7 and +9 per mil, respectively. The isotopic compositions of both fluids, coupled with the available literature data, can be explained in terms of fluid reequilibration with felsic Gawler Range Volcanics or other felsic igneous rocks in the region and with metasedimentary rocks of the Wallaroo Group at low water-to-rock ratios prior to their arrival at the mineralization sites. The lack of significant copper mineralization associated with magnetite-forming fluids that carried copper suggests that there was no effective mechanism of saturation of copper minerals or the quantity of these fluids was not sufficient to produce appreciable copper mineralization. Association of the copper-gold mineralization with the hematitic alteration in the subeconomic prospects can be explained by a two-stage model in which preexisting hydrothermal magnetite with minor associated copper-gold mineralization was flushed by late-stage oxidized brines that had extensively reacted with sedimentary or metamorphic rocks. The reduction of these brines, driven by conversion of magnetite to hematite, resulted in precipitation of copper and gold. The oxidized brines may have contributed additional copper and gold to the system in addition to upgrading preexisting subeconomic Cu-Au mineralization. When compared to published models for the Olympic Dam deposit, the new data for fluids in subeconomic Fe-oxide Cu-Au prospects of the Olympic Dam district indicate the diversity of origins of iron oxide-copper-gold systems, even within the same geologic region.

Externally sourced data. Based on the statewide 1:25,000 conrours coverage (10m contours) with additional processes forcing drainage. Additional processes performed on the completed DEM so metadata does not totally mirror the 10m contour dataset. Accuracy remains at half a contour interval (+-5m). Cell size is 25m. Supplied by TAS Dept. of Primary Industries, Water and Environment (DIPWE)

This is an extended abstract prepared for the Mines and Wines conference run by SMEDG_GSNSW_AIG in Orange, NSW on 18-21 September 2007.

Initial 'straw man' used in the targeting exercise and developed from earlier Y4 (PDT) Meeting in May 2007