No abstract available

The Cobar project of the pmd*CRC utilised potential field inversions to delineate zones of alteration within the Cobar region, NSW. These zones of alteration and correlation with mineralisation is consistent with the mineral system analysis of the region, performed by the T11 Cobar project.

An integrated package comprising geological, structural, geophysical, geochronological and geochemical data. The GIS encompasses the outcropping and covered portions of Palaeoproterozoic and Mesoproterozoic rocks straddling the NSW-SA border (the Broken Hill, Euriowie, Olary, Mount Painter and Mount Babbage Inliers). The GIS features recent data collected by the Broken Hill Exploration Initiative.

Deposits of the iron oxide copper-gold (IOCG) family are diverse in composition, ranging from relatively reduced magnetite-rich to hematite-dominated oxidized styles that may contain major uranium resources. These variations reflect an interplay between multiple hydrothermal fluids with different properties and the varied host lithological settings, each of which ultimately relate to differences in the tectonic evolution of IOCG provinces. - Early Mesoproterozoic and late Paleoproterozoic terranes of southern Australia host the 7.7 Bt Olympic Dam Cu-Au-U deposit as well as numerous lesser known IOCG±U deposits and prospects. They represent the spectrum of magnetite- to hematite-dominated IOCG deposit styles. Magnetite-rich styles of IOCG alteration and mineralization occur in the eastern Gawler Craton and western Curnamona Province. These styles developed at mesozonal to epizonal crustal levels between ~1610 Ma and ~1575 Ma when the terranes were subject to low pressure - high temperature metamorphism and compressional deformation. Magnetite-rich alteration was spatially and temporally associated with high-temperature A-type granitoids of the Hiltaba Suite and with mafic magmas, although the magnetite-forming fluids show major chemical and isotopic contributions from non-magmatic sources. Magnetite-rich alteration varies between IOCG districts and includes biotite-albite or albite-clinopyroxene-actinolite or K-feldspar. Generally minor quantities of chalcopyrite, gold, pyrite and rare pyrrhotite occur in magnetite-rich alteration. - Higher grade IOCG ±U mineralization is associated with hematite-rich alteration (± sericite, chlorite, carbonate) which generally overprinted magnetite-rich assemblages and formed at epizonal crustal levels prior to ~1575 Ma. In the Olympic Dam district uplift and exhumation inferred between ~1595 Ma and ~1575 Ma resulted in superposition of hematitic ±U mineralization on magnetite-rich alteration. Brittle deformation structures and the temporal and broad spatial association of hematitic alteration with bimodal volcanism and alkaline mafic magmatism are consistent with an extensional setting, although supporting data are not yet comprehensive. - The switch from syn-orogenic mesozonal magnetite-rich IOCG formation to post-orogenic epizonal hematite-rich IOCG mineralization is suggested to reflect a change from compressional to extensional tectonism at ~1595-1590 Ma. Contrary to propositions of an 'anorogenic' setting for the Olympic Dam deposit, back-arc settings have been advocated recently. However, several features including the composition of the Hiltaba Suite and co-magmatic volcanics are inconsistent with typical backarc settings. Alternatively, intracontinental orogenesis was closely followed by extension and uplift. A possible driver was convective removal or delamination of thickened lithospheric mantle, triggered by convergence at distant plate margins. This model reconciles magma compositions and timing of volcanism with a switch from compression to extension.

This web service provides access to the Geoscience Australia (GA) ISOTOPE database containing compiled age and isotopic data from a range of published and unpublished (GA and non-GA) sources. The web service includes point layers (WFS, WMS, WMTS) with age and isotopic attribute information from the ISOTOPE database, and raster layers (WMS, WMTS, WCS) comprising the Isotopic Atlas grids which are interpolations of the point located age and isotope data in the ISOTOPE database.

No abstract available

Comprehensive studies of the well preserved, Paleoarchean Panorama volcanic-hosted massive sulfide (VHMS) district provide for the first time definitive evidence that Zn, Pb, Cu, Mo and Ba were leached from the base of the volcanic pile and redeposited at the top in VHMS deposits. This leaching provided more than enough metal to form known deposits, implying that direct input of metal is not required. Sulfur is depleted from the base of the volcanic pile, in line with an increase in Fe2O3/FeO and hematite alteration. These data, combine with sulfur isotope data, indicate that seawater sulfate reduction was facilitated by the oxidation of rock FeO to hematite at high temperature in the H2S stability field. This is the first time such processes have been demonstrated regionally in ancient VHMS mineral systems. The data presented here require Paleoarchean seawater to be sulfate-bearing.

Physical property measurements provide a critical link between geological observations and geophysical measurements and modelling. To enhance the reliability of gravity and magnetic modelling in the Yilgarn Craton's Agnew-Wiluna greenstone belt, mass and magnetic properties were analysed on 157 new rock samples and combined with an existing corporate database of field measurements. The new samples include sulphide ore, serpentinised and olivine-bearing ultramafic host rocks, granitoid, and felsic and mafic volcanic and volcaniclastic country rock. Synthesis of the data provides a useful resource for future geophysical modelling in the region. Several rock types in the region have sufficiently distinct physical properties that a discriminant diagram is proposed to facilitate a basic classification of rock types based on physical properties. However the accumulation of emplacement, metamorphic, hydrothermal and structural processes has complicated the physical properties of the rocks by imposing duplicate and sometimes opposing physical property trends. The data confirms that massive sulphide and ultramafic rocks have the most distinctive mass and magnetic properties but with variability imposed by their complex history. Sulphide content imposes the strongest control on densities, but can only be identified when comprising > 10 vol. % of the rock. The pyrrhotite-rich Ni-sulphide assemblages generally have similar magnetic properties to the host ultramafic rocks, but can have much lower susceptibilities where the thermal history of the rocks has favoured development of hexagonal pyrrhotite over monoclinic pyrrhotite. In ultramafic rocks that contain < 10 vol. % sulphides, density and susceptibility are primarily controlled by serpentinisation, with olivine breaking down to serpentine and magnetite in the presence of water.

A metamorphic database covering the entire eastern Yilgarn Craton has been compiled from pre-existing mapping, 14,500 sites with qualitative metamorphic information, and 470 new key sites with detailed quantitative metamorphic data including P, T, temperature/depth ratio and P-T paths. The derived temporal and spatial patterns contrast with previous tectonic models and invariant crustal depth with the single prograde metamorphic event of the long-standing metamorphic paradigm. In particular, there are large variations in peak metamorphic crustal depths (12 to 31 km), and five metamorphic periods can now be recognised. &#149; Ma: Very localised, low-P granulite of high temperature/depth ratio (>50ºC/km). &#149; M1: High-P (8.7kb), low temperature/depth ratio (<20ºC/km) assemblages localised to major shear zones with clockwise isothermal decompression P-T paths. &#149; M2: Regional matrix parageneses with T ranging 300-550ºC across greenstone belts and elevated temperature/depth ratio of 30-40ºC/km throughout. Tight clockwise paths evolved through maximum prograde pressures of 6 kb and peak metamorphic pressures of 3.5-5.0 kb. &#149; M3a: An extension related thermal pulse localised on the Ockerburry Fault and post-volcanic late basins. Anticlockwise paths to peak conditions of 500-580ºC and 4.0 kb, define moderately high temperature/depth ratio of 40-50ºC/km. &#149; M3b: Multiple localised hydrothermal alteration events during a period of exhumation from 4 kb to 1 kb. Metamorphic patterns during each event have been temporally and spatially integrated with the new deformation framework (Blewett & Czarnota, 2007c) by a process of metamorphic domain analysis and using metamorphic field gradients. The continual evolution with time of fundamental metamorphic parameters throughout the entire history have been constructed as evolution curves and integrated with the deformation, magmatic, stratigraphic and mineralization history. <p>Related material<a href="https://www.ga.gov.au/products/servlet/controller?event=GEOCAT_DETAILS&catno=69771">East Yilgarn Craton Metamorphism and Strain</a> - Map.</p>

Hyperspectral airborne images from the Eastern Fold Belt of the Mount Isa Inlier, were validated as new tool for the detection of Iron oxide Cu-Au (IOCG) related alteration. High resolution mineral maps derived from hyperspectral imaging (4.5m/pixel) enables the recognition of various types of hydrothermal alteration patterns and the localisation of fluid pathways. Four different types of hydrothermal alteration patterns were identified with the hyperspectral mineral maps: (1) Metasomatic 1: White mica mineral maps were applied to map the spatial distribution of regional sodic-calcic alteration in metasedimentary successions of the Soldiers Cap Group in the Snake Creek Anticline. (2) Metasomatic 2: Alteration zoning is evident from albitised granites, assigned to the Williams-Naraku Suite, along the Cloncurry Fault show characteristic absorption features in the shortwave infrared range (SWIR) and can be detected with white mica mineral maps (white mica composition, white mica content, white mica crystallinity index).