Legacy product - no abstract available

A diverse range of mineralisation, including porphyry and epithermal deposits, intrusion-related gold and other metal deposits, iron oxide-copper-gold (IOCG) deposits and orogenic gold deposits all have linkages to crustal growth and magmatic arcs. Furthermore, all of these deposit types are associated with fluids containing H2O, CO2 and NaCl in varying and differing proportions. In all cases, it can be argued that magmas are a key source of hydrothermal fluids for these types of mineral system, and that subduction processes are critical to controlling fluid chemistries, the metal-bearing capabilities of the fluids and depositional processes. The differences on typical/bulk fluid chemistries between deposit types can be explained in part by differences in the P-T conditions of fluid segregation from its magmatic source. The most significant control here is the pressure at which fluid forms from the magma as this has a strong effect on fluid CO2/H2O values. This is clearly exemplified by the rare occurrence of readily detectable CO2 in deep porphyry systems (Rusk et al., 2004). On the other hand, fluid Cl contents (which strongly influence its base metal carrying capacity) are very sensitive to the magma's bulk composition. However, only some subduction-related magmas are fertile, and the differences do not seem to be due solely to variations in effectiveness of depositional processes. So what controls the volatile content of the magmas? Isotopic and other evidence, in particular for S and Cl, shows (unsurprisingly) that the greater contents of these elements in arc magmas compared to other melts is due to contributions from subducted materials, although there may be additional, lower crustal sources of Cl. Variations in the budget of volatiles subducted may thus play a role in controlling the chemistry of magmas and associated hydrothermal fluids, but variations within individual arcs suggests that again this is not the entire story.

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.

Abstract attached

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.

The Herberton/Mount Garnet area is situated in north Queensland, southwest of Cairns (Fig. 1). It is bounded by latitudes 17°15'S and 17°45'S, and by longitudes 145°00'E and 145°30'E, and comprises 2885 sq km. The area is covered by the Herberton and Mount Garnet 1-mile Military map sheets, and lies within the Atherton 1:250,000 Sheet area. Almost the whole of the productive part of the Herberton Tinfield* is covered by the two 1-mile map sheets.

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. This CD was created as part of GA's contribution to the Central Highlands CRA. It contains final versions of all data coverages and shapefiles used in the project, Published Graphics files in ArcInfo (.gra), postscript (.ps) and Web ready (.gif) formats, all Geophysical Images and Landsat data and final versions of documents provided for publishing.

DRAFT Australia's Resources Supporting Economic Growth in the Nation and the Region Paul J Kay Geoscience Australia A new book on Australia's geology viewed through the lens of human activity has been prepared by Geoscience Australia for the 34th International Geological Congress (IGC). Geological factors influencing the nation's recent economic development make up one chapter of the IGC book. Australia's long geological history, fringing passive margins, limited recent deformation and overall landscape stability has formed and preserved a vast quantity of high quality bulk commodity resources. The nation's educated workforce, system of government and legal framework has provided a sound, stable foundation allowing the geological legacy to be utilised through a large export industry for societal and national benefit. The bulk resources of coal, iron, aluminium and liquefied natural gas (LNG) account for more than 50 percent of Australia's export earnings, sustaining the nation's economic success and the lifestyle of the Australian people. Mining has been a cornerstone of the Australian economy since the 19th century gold rushes and importance the resources sector has increased markedly since the mid 20th century, largely a consequence of accelerating export income from the bulk commodities. The industrialisation of Asia has provided the demand, driving infrastructure investment in remote regions of Australia. Advances in technology combined with massive economies of scale and sound public policy have enabled access to the resource and helped to satiate the growing regional market. Responding to changes in the existing status quo, be they trade or societal, will require ongoing interactions between the geosciences and other disciplines to maintain and improve Australia's standard of living.

In addition to typical seafloor VHMS deposits, the ~3240 Ma Panorama district contains contemporaneous greisen- and vein-hosted Mo-Cu-Zn-Sn occurrences that hosted by the Strelley granite complex, which drove VHMS circulation. High-temperature alteration zones in volcanic rocks underlying the VHMS deposits are dominated by quartz-chlorite±albite assemblages, with lesser low-temperature quartz-sericite±K-feldspar assemblages, typical of VHMS hydrothermal systems. Alteration assemblages associated with granite-hosted greisens and veins, which do not extend into the overlying volcanc pile, include quartz-topaz-muscovite-fluorite and quartz-muscovite(sericite)-chlorite-ankerite. Fluid inclusion and stable isotope data suggest that the greisens formed from high temperature (~590C), high salinity (38-56 wt % NaCl equiv) fluids with high densities (>1.3 g/cm3) and high -18O (9.3±0.6-), which are compatible with magmatic fluids evolved from the Strelley granite complex. Fluids in the volcanic pile (including the VHMS ore-forming fluids) were of lower temperature (90-270C), lower salinity (5.0-11.2 wt % NaCl equiv), with lower densities (0.88-1.01 g/cm3) and lower -18O (-0.8±2.6), compatible with evolved Paleoarchean seawater. Fluids that formed the quartz-chalcopyrite-sphalerite-cassiterite veins, which are present within the upper granite complex, were intermediate in temperature and isotopic composition (T = 240-315C; -18O = 4.3±1.5-) and are interpreted to indicate mixing between the two end-member fluids. Evidence of mixing between evolved seawater and magmatic-hydrothermal fluid in the granite complex, along with a lack of evidence for a magmatic component in fluids from the volcanic pile, suggest partitioning of magmatic-hydrothermal from evolved seawater hydrothermal systems in the Panorama VHMS system, interpreted as a consequence swamping of the system by evolved seawater or density contrasts.

This Bulletin summarises the results of regional mapping by teams of the Bureau of Mineral Resources and the Geological Survey of Queensland from 1961 to 1967 over an area of some 67 000 km2 near Townsville. Small areas of high-grade metamorphics may be Precarnbrian, or may be correlatives of the oldest dated rocks (Late Cambrian to Early Ordovician). These early strata occupied a major east-west basin which was destroyed by orogeny and granitic intrusion in Middle Ordovician time. A further period of granitic intrusion consolidated the Lolworth-Ravenswood Block as a major east-west structural high. Of the Palaeozoic sedimentary basins, the Burdekin Basin received sediments from Givetian to Tournaisian times. Ranging in tectonic activity between a mildly unstable shelf and a yoked intracratonic basin, it presented an alternation of marine and continental conditions as it gradually expanded northwards. South of the Lolworth-Ravenswood Block, a miogeosyncline formed in the Middle Devonian. In the Tabberabberan Orogeny a geanticline rose in the geosynclinal belt, and the Drummond Basin formed on its western side. This transverse basin received sediments from Late Devonian to Middle Carboniferous times in three well-marked cycles, each beginning with torrential sediments and ending with mature ones. In its later life, it possibly emptied into the Burdekin Basin. The Broken River Embayment received sediments more or less continuously from Silurian to Carboniferous times, but only the lowest and highest units occur in the map area. The lowest units are shelf and trough sediments, the highest is shallow-marine and lacustrine. At the latest stage in its development the Embayment reached its greatest extension to the southeast and may have connected with the Burdekin Basin. The Late Devonian to Early Carboniferous sediments and volcanics near the coast represent the northern extremity of a basin probably connected with the Yarrol Basin. These basins were destroyed in the Kanimblan Orogeny, and from Late Carboniferous to Early Permian times the area was dominated by igneous activity. The Bowen Basin developed in the Permian volcanic episode, and passed through a series of marine incursions to a continental environment. Local coastal conditions during the first marine incursion produced the Collinsville Coal Measures. Possible correlatives of Bowen Basin units are widespread, although some of the relationships are tenuous. Triassic orogeny ended deposition in the Bowen Basin, and was followed in the south coastal area by a period of igneous activity in the Early Cretaceous. Quiet conditions followed, and by the end of the Cretaceous the area was topographically mature. In the early Cainozoic some earth movement continued, producing the Hillsborough Basin and resulting in erosion of much Triassic sandstone. The mature topography re-established by mid-Tertiary was the base for the subsequent lateritic episode, interrupted by further erosion and deposition. The evolution of the area was completed by Cainozoic volcanism followed by slight erosion. The physiography of the coastal area is dominated by corridors between high ranges. Faulting can be reasonably suspected as a cause, and in some cases there is some evidence. The inland area is occupied mainly by the Burdekin catchment, which developed its present form by movements in the Cainozoic but still retains some northeasterly trends from Palaeozoic structures.