Presented at the Evolution and metallogenesis of the North Australian Craton Conference, 20-22 June 2006, Alice Springs. The Mt Isa Inlier and southern McArthur basin are, arguably, the most extensively studied and best understood Palaeo- to Mesoproterozoic terranes in Australia, and possibly the world. These rocks host one of the world's largest base metal repositories. The McArthur - Mt Isa - Cloncurry mineral belt contains several world class Zn-Pb-Ag, Cu, and Cu-Au deposits as well as hosting significant uranium resources. Since 1995, Geoscience Australia, in combination with the Geological Surveys of Queensland and the Northern Territory, has implemented a series of integrated, multidisciplinary projects in the Mt Isa and southern McArthur regions with the aim of generating a chronostratigraphic understanding of basin evolution. The integration of detrital and magmatic U-Pb zircon SHIRMP geochronology with depositional facies and sequence stratigraphic analysis has allowed the development of a chronostratigraphic framework for the Leichhardt (~1800-1745 Ma), Calvert (~1730-1690 Ma) and Isa (~1670-1575 Ma) Superbasins of the Mt Isa and southern McArthur regions. The new event chart recognises three supersequences in the Leichhardt Superbasin, two supersequences in the Calvert Superbasin, and seven supersequences in the Isa Superbasin. Each of the supersequences is unconformity-bounded. In the Mt Isa region, times of increased magmatic activity broadly coincided with intervals of incision and gaps in the sedimentary rock record. <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>

The available geological data suggest two stages of hydrothermal activity at a number of sub-economic iron-oxide copper-gold systems of the Olympic Dam region of the Olympic Cu-Au province of the eastern margin of the Gawler Craton. They contain high- (>400?C), and moderate- to low-(200 to 300C?) temperature Fe-oxide rich hydrothermal alteration. The mineral assemblages are CAM: calcsilicate - alkali feldspar ? magnetite ? Fe-Cu sulphides, and HSCC: hematite-sericite-chlorite-carbonate ? Fe-Cu sulphides ? U, REE minerals ([Skirrow, 2002 #563; Skirrow et al., this volume). The bulk of the sub-economic Cu-Au mineralisation is associated with HSCC stage. Microanalytical results by PIXE, however, demonstrate that significant amount of copper (>500 ppm) has been transported by early-stage high-temperature fluids. These fluids were recorded as extremely concentrated fluid inclusions with multiple solid phases, compared to relatively simple liquid-vapour inclusions of the HSCC stage. Sulfur isotopes demonstrate that sulphur in these system was be derived either from magmatic rocks by relatively oxidised fluids (?34Ssulfides from ?5 to 2?), or from crustal sedimentary rocks (?34Ssulfides from 5 to 10?). Oxygen and hydrogen isotopes suggest ?metamorphic? rather then ortho-magmatic origin of the HSCC fluids. These observations can be reconciled with a two-stage model where pre-existing geochemical trap of hydrothermal magnetite (? sub-economic copper-gold mineralisation) is flushed by oxidised brine of sedimentary or metamorphic origin. The reduction of this brine due to magnetite to hematite conversion results in precipitation of copper and gold.

The presence of relatively abundant bedded sulfate deposits before 3.2 Ga and after 1.8 Ga, the peak in iron formation abundance between 3.2 and 1.8 Ga, and the aqueous geochemistry of sulfur and iron together suggest that the redox state and the abundances of sulfur and iron in the hydrosphere varied widely during the Archean and Proterozoic. We propose a layered hydrosphere prior to 3.2 Ga in which sulfate produced by atmospheric photolytic reactions was enriched in an upper layer, whereas the underlying layer was reduced and sulfur-poor. Between 3.2 and 2.4 Ga, sulfate reduction removed sulfate from the upper layer, producing broadly uniform, reduced, sulfur-poor and iron-rich oceans. As a result of increasing atmospheric oxygenation around 2.4 Ga, the flux of sulfate into the hydrosphere by oxidative weathering was greatly enhanced, producing layered oceans, with sulfate-enriched, iron-poor surface waters and reduced, sulfur-poor and iron-rich bottom waters. The rate at which this process proceeded varied between basins depending on the size and local environment of the basin. By 1.8 Ga, the hydrosphere was relatively sulfate-rich and iron-poor throughout. Variations in sulfur and iron abundances suggest that the redox state of the oceans was buffered by iron before 2.4 Ga and by sulfur after 1.8 Ga.

Metallogeny of eastern Australia As part of the `Felsic Igneous Rocks of Australia' project, Geoscience Australia personnel have been compiling and synthesising datasets of various metallogenic parameters for intrusive and country rock units of the Tasmanides of eastern Australia (previously reported in the xxx issue of AUSGEO News; web address; see http://www.ga.gov.au/rural/projects/aust_felsic_igneous_rocks.jsp), to assist the exploration industry in the search for intrusion-related and other mineralisation systems. As reported earlier this approach is been undertaken as regional modules, with datasets for north Queensland currently being prepared for release, and datasets for Tasmania now completed and released as a joint Geoscience Australia - Mineral Resources Tasmania product. This article reports on aspects of intrusion-related gold systems in northern Qld utilising the results of the new datasets for that region.

This paper reviews recent developments in igneous metallogeny, in particular, with regard to intrusion-related copper-gold and gold mineralisation, to show that eastern Australia is still prospective for granite-related gold systems.

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Whole of Australia. Preliminary release. Sediments, Granites, Grid, Coast, Buffer and Rockchem data included.

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As part of the 11th SGA Biennial meeting in Townsville, Australia, the Organising Committee is offering a series of field trips to examine the geology and setting of important mineral provinces in Australia, New Zealand and Papua New Guinea. The purpose of this short article is to provide an overview of the metallogeny of Australia, which is considered within the framework of the geological evolution of the Australian continent.

To assist explorers, Geoscience Australia (GA) has compiled a fact sheet (2006) of products produced by GA related to those commodities (nickel, copper, cobalt, chromium, platinum-group elements, titanium, vanadium) associated with Precambrian mafic-ultramafic rocks in Australia. These products include national review publications (e.g., Nickel sulphide deposits in Australia), reports of metallogenic province studies (Kimberleys, Pilbara, Arunta, Gawler), and various maps, PowerPoint presentations, and digital datasets. Most products can be downloaded free through the www links provided on the fact sheet.