This talk summarises the ‘essential ingredients’ considered important for formation of major Olympic Dam-style IOCG systems in the Gawler Craton, and elsewhere. A ‘working model’ of a crustal-scale IOCG system is presented for the Olympic Dam region. Finally, the newly released IOCG Potential Map of the Gawler Craton is described.

The absence of basement outcrop and the nearly complete lack of surface expression of mineralisation in the Olympic Cu-Au province is the major impediment to mineral exploration in the province. In such circumstances, analysis of potential field data is one of the usual ways of inferring hidden geology, as high-quality datasets, especially aeromagnetic data, are available for most of the actively explored areas of Australia. Quantitative interpretation of potential field data principally involve 2D forward modelling of profiles, or sections, by skilled interpreters but it can be difficult, and time-consuming, to correctly track structure and geology from one section to the next should one wish to create a 3D model of the geology. To alleviate this problem, we have used a modification of the methods of Li and Oldenburg (1996 & 1998), constrained by known geological information, to give geologically and geophysically consistent solutions to the possible distributions of sources giving the magnetic and gravitational fields observed in a region about Olympic Dam.

This talk was presented at the Gawler Craton 2002: State of Play conference held in Adelaide, December 2002.

This talk was presented at the Gawler Craton 2002: State of Play conference held in Adelaide, December 2002.

Shared geological and geochemical processes are involved in the formation of particular groups of uranium deposits. Three families of uranium mineral systems are recognised: magmatic-, metamorphic- and basin-related. End-member fluids in each family are magmatic-hydrothermal, 'metamorphic' (including fluids reacted with metamorphic rocks at elevated temperatures), and surficial fluids such as meteoric water, lake water and seawater. Most well known uranium deposit types can be accommodated within this tripartite framework, which explicitly allows for hybrid deposit types.

The oldest rocks in the Australian continent, older than about 3.0 billion years, have long been thought to be restricted to relatively small areas of the Yilgarn and Pilbara cratons in Western Australia. Recent results from GA's new SHRIMP facility are changing that view, showing that early Mesoarchean (~3150 Ma) rocks are present on the eastern margin of the Gawler Craton. These rocks are approximately half a billion years older than the oldest previously-dated rock from South Australia, and indicate that parts of the Gawler Craton are of similar antiquity to parts of the Yilgarn and Pilbara. The new results have significant implications for the geodynamic evolution of the Gawler Craton and Australia more broadly. The distribution of this newly-identified ancient crust may also provide explanation for contrasting patterns of mineralisation within the Gawler Craton, and guide predictive models for mineral exploration.

Presented at the Evolution and metallogenesis of the North Australian Craton Conference, 20-22 June 2006, Alice Springs. The Tanami Region (TANAMI and THE GRANITES 1:250 000 map sheet areas) is centrally located within the North Australian Craton and contains a gold-mineralised Palaeoproterozoic orogenic sequence. Page et al (1995) postulated Neo-Archaean granitic gneiss as basement to the Tanami Group, although no lower sedimentary contact has been observed. <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>

Pending

UNCOVER vision Geological models: building and testing Surface and cover Upper crust Deeper lithosphere Applying mineral systems undercover (examples) Current and future programme: testing geological models with drilling

The HyLogger hyperspectral core-mapping instrument, developed by CSIRO's Mineral Mapping Technologies Group (MMTG), can log up to 1000 m of core per day (more for chips) and has automated core tray handling, digital imaging and spectral scanning and specialised mineral identification software for rapid logging capability. The Central Gawler Gold Province HyLogger project is a collaborative undertaking between the collaborators/developers: CSIRO MMTG, Primary Industries and Resources South Australia (PIRSA) / Cooperative Research Centre for Landscape Environments and Mineral Exploration (CRC LEME) and Geoscience Australia. The Tunkillia prospect, part of the Central Gawler Gold Province, is located some 250 km South of Coober Pedy, and is a regolith-dominated landscape with up to 300m of cover. The area delineated as a de-magnetised zone by earlier studies, was extensively drilled with Diamond and RC drilling. Selected diamond holes from Tunkillia were selected for this HyLogger investigation. At Tunkillia, high gold shows some correlation with white mica composition (phengite-muscovite), as well as mica crystallinity and spectral absorption feature wavelength shifts, possibly representing an increasing in acidity due to mixing of metamorphic muscovite and hydrothermal fluid in the altered granitic host rocks. Alteration occurring in mafic dykes, are well delineated by chlorite-carbonate minerals which can be easily mapped. Gold is predominantly confined to a granitic host, high gold in mafic rocks appears to occur in nearly all cases on margins / fracture zones between the dyke and the host rock. This talk was presented at the Workshop on iron oxide copper-gold systems of the Gawler Craton, held at the AMF Centre, Adelaide on 24 February, 2006.