The Olympic Copper-Gold Province of the eastern Gawler Craton of South Australia, in hosting the Olympic Dam, Prominent Hill, Carrapateena and Moonta-Wallaroo deposits, has the greatest known iron-oxide, copper, gold and uranium (IOCGU) metal endowment of any geological province on Earth. The historic Moonta-Wallaroo copper-gold mining fi eld is within the Moonta sub-domain and is hosted by the ~1750 Ma Wallaroo Group that preserves some evidence of evaporitic sedimentation, similar to other major iron oxide-copper-gold (IOCG) provinces in Australia and North America. Observations in the Moonta-Wallaroo district indicate that mineralisation was broadly associated with intense metasomatic alteration, intrusion of granites and gabbros of the Hiltaba Suite, moderate grade metamorphism and intensely partitioned deformation. The driving force of this extensive ~1600 to 1500 Ma hydrothermal, magmatic and tectonic event was a major thermal pulse, the cause of which remains under debate. The vein-style mineralisation in the Moonta-Wallaroo district developed in ground prepared by ductile shearing. Widespread sub-economic copper mineralisation in the region is associated with intense regional magnetite-bearing skarn-like alteration of the Cloncurry type, with oxidation and hematite replacement of early magnetite. Targeting of structurally-controlled demagnetised zones and the oxidised margins of magnetic anomalies has been applied successfully in the northern Olympic Copper-Gold Province (e.g. Prominent Hill) and is also applicable to the Moonta-Wallaroo region. The recently discovered copper-gold mineralisation at the Hillside copper-gold deposit demonstrates the continued prospectivity of this southern portion of the Olympic Copper-Gold Province.

This paper describes the highlights of AGSO's work in the North Pilbara Project, a joint AGSO-Western Australia Geological Survey (GSWA) effort conducted under the National Geoscience Mapping Accord (NGMA) between 1995 and 2000. One of the principal drivers for AGSO's research in the Pilbara was the possible inapplicability of exploration models and genetic interpretations of Archaean mineral deposits because these models were commonly based upon late Archaean examples. One of our goals was to document the differences between the late Archaean and the early-mid Archaean mineral systems, and to develop regional thematic synthesis datasets so that more robust models could be developed to encompass the entire Archaean era. These datasets, together with our research into new exploration tools, have, and continue to assist exploration in the Pilbara. Our results also have applications to other terranes.

Chemical modeling of gold mineralisation in the Lachlan Fold Belt shows that gold can be precipitated over a wide temperature range (from 320 to 200 ?C in this study) from CO2-bearing, low salinity, aqueous fluid flowing upwards through faults in turbiditic sequences. In agreement with field observations, the veins are predicted to be mostly quartz (> 93 vol.%) with minor amounts of pyrite, arsenopyrite and muscovite (sericite) precipitating above 230 ?C. The predicted alteration assemblage contains pyrite, arsenopyrite, calcite, muscovite (sericite), chlorite and feldspar. Varying some of the chemical characteristics of the initial fluid has resulted in the following changes to the model: Preventing the fluid from boiling stops gold precipitating below 310 ?C but has little effect on the vein mineralogy or the mineralogy of the surrounding alteration assemblage. Removing CO2 from the fluid also prevents gold precipitation in the veins below 300 ?C. The modeling also generates an alteration assemblage with a number of Ca-rich minerals as less calcium carbonate exists in this system. Removing sulfur species from the initial fluid decreases the amount of gold precipitated by more than a factor of ten, which is to be expected if sulfur ligands are the main species for gold transport. However, the vein assemblage and the lack of sulfide minerals in the surrounding alteration assemblage also suggest that sulfur species are important in this mineral system. Increasing the initial oxidation state (?O2) of the fluid inhibits gold precipitation in the veins above 260 ?C and leads to a high proportion of dolomite in the surrounding alteration assemblage. On the other hand, decreasing the initial oxidation state of the fluid lead to gold precipitation over a range of temperatures below 310 ?C but predicts that mainly graphite ? quartz precipitates in the veins and that the surrounding alteration assemblage is dominated by feldspar proximal to the veins. This style of mineralogy is not commonly observed in gold deposits in the Lachlan Fold Belt. Increasing the initial pH of the fluid inhibits the amount of minerals that precipitate in the veins, which are dominated by calcite at high temperatures and graphite at low temperatures and corresponding minor amounts of gold. The proximal alteration assemblage is dominated by K-feldspar with amphibole, biotite and epidote. This mineral assemblage is not commonly observed in these deposits. Decreasing the initial pH of the fluid allows gold to precipitate below 280 ?C but generates a proximal alteration assemblage dominated by pyrophyllite, which again is not commonly observed. The results are in agreement with the widely accepted premise that gold is transported as bisulfide complexes and that the ore-bearing fluid is typically a low-salinity, mixed aqueous-carbonic fluid with low-moderate CO2 contents (Ridley and Diamond, 2000). However, the modeling has shown that the absence of certain physico-chemical processes or fluid constituents, such as boiling or lack of CO2 may inhibit gold precipitation in some environments. Large fluctuations in ?O2 or pH will also significantly change the vein and alteration mineralogy and generally reduce the amount of gold that is precipitated. This suggests that these fluids remain rock buffered during their journey from the source to the trap site.

Hydrothermal zircons have been previously reported from F- and/or CO2-rich systems (Rubin et al. 1993), quartz-tourmaline mesothermal gold veins (Claoue-Long et al. 1990; Kerrich & King, 1993), and at the Olympic Dam Cu-uranium deposit (Oreskes & Einaudi, 1990). However, it has previously been difficult to prove that the zircons were truly hydrothermal in origin. Hydrothermal zircons were characterised by the following multi-techniques: (1) their distinct mor-phology and their paragenetic relationships to ore and mineral assemblages within the orebodies, (2) the higher concentration of zircon within the orebody relative to that of the host rocks, (3) the presence of ore and alteration minerals as solid mineral inclusions within the zircons, (4) similar fluid inclusion composi-tions in these zircons and the associated ore and gangue minerals, and (5) their trace element composition and zonation as measured by the CSIRO-GEMOC nuclear microprobe and LA-ICPMS analysis. Studies within a number of deposits have demonstrated the distinctive chemical composition of `hydrothermal? zircons when compared to temporally and spatially associated magmatic zircons (Table 1). Trace element discriminant diagrams, previously constructed for magmatic zircons clearly show the different trace element characteristics hydrothermal zircons and allow the source of both magmatic and hydrothermal zircons to be obtained. Table 1 Element enrichment in hydrothermal zircons from deposits in Australia and Papua New Guinea. Deposit Type Elemental Enrichment Enterprise, NT, Australia Intrusive-related, vein Au Cu, As, Ag, Sn, Sb, Ba Bottle Creek, WA, Australia Lode Au deposit Fe, As, Sr, Sn ,Sb, Ba Gidginbung, NSW, Australia High sulfidation Au deposit As, Sb, Th, Yb, U, Y, Hf Nena, Papua New Guinea High sulfidation Au deposit Fe, Cu, Yb, Th, Sn, Sb, Ba The Dam, NSW, Australia Porphyry Au-Cu deposit Fe, Cu, Sn ,Sb, Ba Many mineral deposits are difficult to date precisely due to the lack of suitable zircon-bearing host rocks or due to the resetting of other isotopic systems. In these instances, U-Pb dating of hydrothermal zircons directly associated with mineralisation may have a particular advantage over other isotopic systems that rely on less stable minerals. References Claoue-Long J.C., King R.W. & Kerrich R., 1990, Archaean hydrothermal zircon in the Abitibi greenstone belt: constraints on the timing of gold mineralisation. Earth and Planetary Science Letters, 98, 109-128. Kerrich R. & King R., 1993, Hydrothermal zircon and baddeleyite in Val-d?Or Archaean mesothermal gold deposits: characteristics, composition and fluid inclusion properties with implication for timing of primary gold mineralisation. Canadian Journal of Earth Sciences, 30, 2334-2351. Oreskes N. & Einaudi M.T., 1990, Origin of rare earth element-enriched hematite breccias at the Olympic Dam Cu-U-Au-Ag deposit, Roxby Downs, S. Australia. Economic Geology, 85, 1-28. Rubin J.N., Henry C.D., Price J.G., 1993, The mobility of zirconium and other ?immobile? elements during hydrothermal alteration. Chemical Geology, 110, 29-47. Acknowledgements TPM and KCL publish with permission of the CEOs of Geoscience Australia and CRC LEME.

Presented at the Evolution and metallogenesis of the North Australian Craton Conference, 20-22 June 2006, Alice Springs. The southern Arunta region contains a number of small (<5 Mt) Zn-Cu-Pb (Ag-Au) deposits. Although none of these deposits are economic, they do indicate a moderate level of base-metal potential for this region. Most of these deposits are located in the Strangways Range, which forms part of the Aileron Province. These deposits were classified as Oonagalabi-type deposits by Warren & Shaw (1985), citing similarities in metal assemblages, alteration assemblages, and host units, and interpreted as volcanic-hosted massive sulphide (VHMS) deposits. More detailed geological mapping and geochemical and geochronological data suggest that the Oonagalabi group should be subdivided further into three types, the Utnalanama-type, the re-defined Oonagalabi-type and the Johnnies-type (Hussey et al., 2005). <p>Related product:<a href="https://www.ga.gov.au/products/servlet/controller?event=GEOCAT_DETAILS&amp;catno=64764">Evolution and metallogenesis of the North Australian Craton Conference Abstracts</p>

Cenozoic basins of the Lake Frome region in South Australia host the Beverley in-situ recovery uranium mine as well as the Honeymoon, Four Mile, Oban, and Goulds Dam deposits and recently discovered Pepegoona prospect several kilometres to the north of Beverley. Most deposits occur in organic-rich sands and silts of the Eocene Eyre Formation or Miocene Namba Formation (Beverley). However, the recognition of Eromanga Basin host rocks at the Four Mile West deposit (Heathgate Resources, pers. comm., 2009) extends the age range of host stratigraphic units into the Mesozoic. We define the Frome Uranium Province as the 3-dimensional volume encompassing known and potentially mineralised areas of Cenozoic and Mesozoic basins in the Lake Frome region, constrained on three sides by Proterozoic inliers (Fig. 1). The northern extent of the metallogenic province is unknown; recent discovery of anomalous uranium in Cenozoic sediments near Moomba (Crescent Gold Ltd, September 2009, www.crescentgold.com) points to the potential of the Lake Eyre Basin for uranium mineralisation well to the north of Lake Frome.

Controversy continues on the origin of gold deposits in metamorphic belts and the role of magmatism in these regions. We adopt a Minerals Systems approach to analyse and compare some chemical processes related to the formation of major Australian Au-dominated deposits that have been classified as either orogenic or intrusion-related. Fluid inclusion data was compiled from deposits in the Archaean Yilgarn Craton, the Proterozoic Tanami, Pine Creek and Paterson areas, and the Palaeozoic western Lachlan Fold Belt. On a regional scale, and a deposit scale, the dominant lithologies in each area are mafic and felsic igneous rocks, graphite-bearing clastic sediments and banded iron-formations. Significantly, evaporites are absent from all areas. A clear spatial association exists in the Tanami, Telfer and Pine Creek regions with reduced granites. The complied data show that the deposits form over a wide range of temperature-pressure conditions (<200 to >600ºC, <1.4 kbar) and that they involve fluids with broadly similar major chemical components (i.e. H2O+NaCl+CO2± CH4 ± N2). The main difference is that Telfer, Tanami and Pine Creek deposits have higher salinity fluids. Elsewhere, deposits classified as orogenic gold deposits have low salinity fluids (typically <10 wt.% NaCl eq.) with CO2 contents ranging from 10 to 25 mol.% (Ridley & Diamond, 2000), whilst intrusion-related gold deposits may show evidence of higher CO2 and/or high salinity fluid inclusions (Thompson & Newberry, 2000). Processes thought to cause gold precipitation in both types of deposits are fluid-rock interaction (e.g. desulphidation), phase separation, or fluid mixing. We have re-examined the impact of the H2O-NaCl-CO2 system on the nature of the dominant gold precipitation mechanisms at different crustal levels (Fig. 1). The latter infers different roles of chemical (fluid-rock interaction) vs rheological (phase separation and/or fluid mixing) host-rock controls on gold deposition. This also implies that at the site of deposition, similar precipitation mechanisms operate at similar crustal levels for both orogenic and intrusion-related gold deposits

Sandstone uranium mineral systems

Detailed analysis and modeling of regional gravity and magnetic datasets from the Stuart Shelf around the Olympic Dam iron oxide-copper-gold (IOCG) deposit, constrained by geological observations from deep drillcores, show that the eastern Gawler Craton at 1.61-1.59 Ga consisted of an Archean core with two volumes of supracrustal successions stepping out eastward from it. This pattern is consistent with that displayed on the Eyre Peninsula. Detailed models of potential-field data show no evidence for the presence of widespread mafic rocks or extensional basin systems developed immediately prior to, or during, IOCG mineralization. The high intrusive level, and geometry of Hiltaba Suite plutons emplaced immediately prior to IOCG mineralization is difficult to explain in terms of a genetic association with mantle plumes, continental extension, or rifting. Instead, the tectonic setting inferred from the basement architecture during mineralization is one of low-strain compression, based on geometric considerations. A case can be made for mild extension in a localized accommodation zone during emplacement of the Hiltaba Suite and Gawler Range Volcanics, in an overall orogenic setting with northwest-southeast directed tectonic transport in present coordinates. An IOCG minerals system produced during low-strain compression is consistent with maximum rates and volumes of fluid flow in the upper crust, and access of these fluids to a variety of basement rock types to buffer metal-scavenging fluids. This fluid-driving mechanism does not require, or implicate, a genetic role for regional mafic magmatism and volcanism synchronous with IOCG mineralization. The approach used in this study is generally applicable to exploration for IOCG systems, and other mineral systems in covered terranes that have distinctive geophysical signatures resulting from redox fluid-wallrock geochemical reactions.

The report on the Geology of the Carnarvon Basin is issued in three separate and relatively independent Parts. Each Part treats an individual section of the subject and is accompanied by a Summary and an appropriate list of References. Part 1 (published 1965) deals with the Pre-Perrnian Stratigraphy and also includes a General Summary and other introductory information. Part 2 (published 1967) deals with the Permian Stratigraphy, and Part 3 details the Post-Permian Stratigraphy and also contains information on Regional Structure, Palaeogeography, and Economic Geology. These Parts are being published separately, but, as they are parts of a single report, text-figure numbers are continued through the Parts. The regional map of the Basin is included in Part 1.