Globally supracrustal sedimentary rocks are known to preferentially precipitate gold between 2400 Ma and 1800 Ma (Goldfarb et al. 2001). The Palaeoproterozoic Tanami and Pine Creek regions of Northern Australia host one world-class gold deposit and many other gold deposits in anomalously iron-rich marine mudstones (Figure 1). New fluid-rock modelling at temperatures between 275 - 350C suggest a strong correlation between gold grade and these Palaeoproterozoic iron-rich, fine-grained sedimentary rocks.

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The eastern Yilgarn Craton (EYC) of Western Australia is Australia's premier gold and nickel province, and has been the focus of geological investigations for over a century. Geoscience Australia, in conjunction with partners in the Predictive Mineral Discovery Cooperative Research Centre conducted a series of projects between 2001 and 2008 (Y4 project team, 2008). This article summarises the highlights and new findings from the research, many of which challenge previous paradigms on the tectonics and architecture, as well as the relationship of gold to structure, magmatism and metamorphism. Although a Yilgarn-based study, the results have general implications for other Archaean terranes.

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From 1995 to 2000 information from the federal and state governments was compiled for Comprehensive Regional Assessments (CRA), which formed the basis for Regional Forest Agreements (RFA) that identified areas for conservation to meet targets agreed by the Commonwealth Government with the United Nations. These 5 CDs were created as part of GA's contribution to the SE Queensland CRA. CD1 contains ArcView Legends and Projects, data coverages, shapefiles, all documents and reports and associated maps and figures. CD2 contains various edited versions of covers and shapefiles, original data supplied by custodians, and staff workareas. CD3 contains Landsat, Magnetics etc. images. CD4 contains DEM etc. CD5 contains integration data, miscellaneous ArcInfo grids, and ArcInfo graphic files.

The Tasman Orogen represents a long-lived accretionary orogen with numerous orogenic cycles of extension and subsequent orogeny. Although details of the orogen are controversial, it is evident that the present configuration represents the cumulate products of many orogenies including both accretion and significant rearrangement of terranes. As a result the Tasman Orogen plays host to a significant array of commodities within a myriad of deposit styles, related to a variety of tectonic regimes. It is also evident that many mineralisation styles are repeated through the different orogenic cycles, and commonly during the same parts of the orogenic cycle. For example, volcanic-hosted massive sulphide deposits form early in cycles, whereas lode gold deposits form during contractional orogenesis that terminates the cycle. The geological complexity is both an advantage and disadvantage. Although the complexity can hinder regional exploration, it offers significant potential for identifying regions where previously unrecognised mineralisation styles may be present, particularly under cover where the geology (and tectonic history) is less well constrained.

From 1995 to 2000 information from the federal and state governments was compiled for Comprehensive Regional Assessments (CRA), which formed the basis for Regional Forest Agreements (RFA) that identified areas for conservation to meet targets agreed by the Commonwealth Government with the United Nations. These 3 CDs were created as part of GA's contribution to the Tasmania CRA. CD1 contains final versions of all data coverages and shapefiles used in the project, and final versions of documents provided for publishing. CD2 contains Published Graphics files in ArcInfo (.gra), postscript (.ps) and Web ready (.gif) formats. CD3 contains all Geophysical Images and Landsat data.

Field investigations by AGSO-Geoscience Australia in late 2000, as part of a National Geoscience Agreement with the Northern Territory Geological Survey (NTGS), evaluated the geological setting of Proterozoic mafic-ultramafic intrusions in the Arunta Province of central Australia. The major aims of this regional study were to constrain the various mafic-ultramafic magmatic systems within the event chronology of the Arunta Province, and to provide a geoscientific framework for assessing the prospectivity and resource potential of the intrusions. This report summarises the field relationships and mineralisation features of the major mafic-ultramafic intrusions in the Arunta Province. They form large homogeneous gabbroic bodies, folded high-level mafic sills, steeply dipping amphibolite sheets and relatively undeformed ultramafic plugs with alkaline and tholeiitic affinities. Metamorphic grades range from granulite to sub-amphibolite facies. Chilled and contaminated margins and net-vein complexes resulting from the commingling of mafic and felsic magmas indicate that most intrusions crystallised in situ and were not tectonically emplaced. The intrusions were subdivided into western, central and eastern groups on the basis of lithology, metamorphic-structural history, degree of fractionation and limited geochronology. The field investigations described here and preliminary geochemical data (see Hoatson 2001) indicate that the western and central intrusions have some potential for Ni-Cu-Co sulphide deposits, whereas the eastern intrusions appear to be more prospective for platinum-group element (PGE) mineralisation. The recent emerging evidence that the eastern Arunta is prospective for PGE mineralisation is supported by exploration companies defining anomalous PGE-Cu-Au concentrations in hydrothermal veins hosted by the Riddock Amphibolite and in magnetite layers of the Attutra Metagabbro. These results, for the first time, highlight geographical differences in the mineral prospectivity of mafic-ultramafic rocks in the Arunta Province.

An orogenic cycle typically follows a sequence of events or stages. These are basin formation and magmatism during extension, inversion and crustal thickening during contractional orogenesis, and finally extensional collapse of the orogen. The Archaean granite-greenstone terranes of the Eastern Yilgarn Craton (EYC) record a major deviation in this sequence of events. Within the overall contractional stage, the EYC underwent a lithospheric-scale extensional event between 2665 Ma and 2655 Ma, resulting in changes to the entire orogenic system. These changes associated with regional extension include: the crustal architecture; greenstone stratigraphy; granite magmatism; thermo-barometry (PTt paths); and structure. Synchronous with these changes was the deposition of the first significant gold, and it is likely that the intra-orogenic extensional event was one of the critical factors in the region's world-class gold endowment.

Assessment of mineral potential in the Regional Forest Agreement Areas (RFAs) required collating mineral potential tract maps of individual deposit styles to produce composite, cumulative and weighted composite and cumulative maps. To achieve that an Avenue-script based ArcView extension was created to combine grids of mineral potential tract maps. The grids were combined to generate maps which showed either the highest (weighted or non-weighted) or cumulated (weighted or non-weighted) values. Resources and Advice Decision Support System (RADSS) combines features of the ArcView extension used in mineral potential assessments in RFAs and ASSESS. It is an ArcView extension with a 'Wizard'-like main dialog that leads the user through the process of creating an output. The system has the capacity to combine GIS-layers (raster and vector) to produce various mineral potential and other suitability maps.