Australia's thorium resources currently amount to 452,000tonnes Th of which 364,000tonnes (80.5%) occur in heavy mineral sand deposits, 53,300tonnes (11.7%) in a vein type deposit at Nolans Bore in the Northern Territory and another 35,000tonnes (7.7%) are in an alkaline trachyte plug at Toongi in New South Wales. This distribution of thorium resources differs from the world wide distribution where 31.3% of the resources occur in carbonatites, 24.6% are in placers, 21.4% in vein type deposits and 18.4% in alkaline rocks. This variance is at least partly due to relatively more, although still inadequate, data on thorium resources being generated by the very active heavy mineral sand operations around Australia. Even where thorium analyses have been carried out for other types of deposits that host thorium, such results are not published since thorium is not considered to be economically important. All of Australia's thorium resources occur in multi-commodity deposits, dominantly the heavy mineral sands and in rare earth deposits where the extraction cost would be shared with if not totally supported by the other commodities in the deposit. Because there has been no large-scale demand for thorium, there has been little incentive for companies to assess the cost for the extraction of thorium resources. Hence there is insufficient information to determine how much of Australia's thorium resources are economic for purposes of electricity power generation in thorium nuclear reactors. Geoscience Australia is currently engaged in upgrading its database on thorium resources as part of the five-year Onshore Energy Security Program and Australia's figures on its thorium resources will be refined as a result of this work. Because of limited demand, there has been very little exploration for thorium in Australia. As part of its five year Onshore Energy Security Program, Geoscience Australia is in process of upgrading its continent wide airborne radiometric coverage and is conducting a low density geochemical sampling program across the continent. These programs will help to develop a better understanding of the geological and geochemical environment of thorium in Australia and provide basic pre-competitive data to reduce risk the level of risk for the mineral exploration industry. Assessment of thorium resources by the minerals industry in the future will depend upon the development of commercial-scale thorium nuclear reactors and the resulting demand for thorium resources.

Abstract

Presented at the Evolution and metallogenesis of the North Australian Craton Conference, 20-22 June 2006, Alice Springs. The King Leopold and Halls Creek Orogens in the Kimberley region of northern Australia are divided into three distinct terranes, each representing a different tectonic setting, that may be part of a larger, diverse collisional orogen on a scale similar to the present Alpine-Himalayan Orogen. Collision with the Kimberley Craton drove intracratonic deformation in the adjacent Tanami and Arunta regions of the North Australian Craton. <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

Presented at the Evolution and metallogenesis of the North Australian Craton Conference, 20-22 June 2006, Alice Springs. The 2005 Tanami Seismic Collaborative Research Project was developed to provide a better understanding of the crustal architecture and mineral systems of the Tanami region within Western Australia and the Northern Territory. This was achieved through the acquisition of four regional scale deep crustal seismic reflection profiles. The Tanami Seismic Collaborative Research Project involved Geoscience Australia, the Northern Territory Geological Survey, the Geological Survey Western Australia, Newmont Exploration Pty Ltd and Tanami Gold NL. <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>

Uranium-rich igneous rocks are recognised as an important source of metals in uranium mineral systems. Magmatic-related uranium mineralisation may be orthomagmatic in origin, forming via favourable igneous processes, or may result from the exsolution of uranium-rich fluids from particular magmas. Additionally, it is recognised that igneous rocks also may contribute directly to basin-related uranium mineral systems as a metal source. Thus, mapping of the distribution of uranium in igneous rocks has the potential to highlight prospective regions for uranium mineralisation at a macro-scale. Geoscience Australia has produced a series of three digital maps showing the uranium content of igneous rocks across Australia, drawing together geochemical and geological datasets from disparate open file sources. Map 1 shows the uranium concentration in whole rock geochemical analyses plotted as point data on a background of igneous rock type, which itself is derived from Geoscience Australia's 1:1 000 000 national surface geology map. Map 2 integrates these datasets, and shows the average uranium content of all intersecting geochemical data point for outcropping individual igneous rock units. In Map 3, a similar approach is employed in mapping the average uranium content of igneous rocks occurring under cover, using interpreted solid geology coverages. Combined, these maps provide a comprehensive picture of the province-scale trends in igneous uranium content across the continent. Using an applied knowledge of processes leading to uranium concentration in magmatic systems, igneous rocks exhibiting a favourable combination of factors are able to be identified for further analysis of prospectivity for uranium mineral systems.

Uranium deposits are generally classified into types based on host rock, orebody morphology or structural setting. Widely used schemes contain 14 or more deposit types and numerous sub-types. However, groups of deposit types were formed by similar geological and geochemical processes and likely represent 'variations on a theme'. An alternative scheme is presented that recognises the continuum of possible uranium deposit styles between three families of mineral systems: magmatic-related, 'metamorphic'-related, and basin-related. Formation of uranium deposits in each family involves fluids of three end-member type: magmatic-hydrothermal, 'metamorphic' (including diagenetic waters and fluids reacted with metamorphic rocks at elevated temperatures), and surface-derived fluids such as meteoric waters, seawater, lakewater and groundwater. By better understanding the fundamental geological and geochemical processes involved in ore formation in each family of uranium mineral systems, the most important geological 'symptoms' can be recognised and mapped. This mineral systems approach has been applied to magmatic-related uranium systems in Australia. The predictions of potential suggest that the under-representation of magmatic-related uranium resources relative to other parts of the world with similar geology may be due not to low endowment but to lack of discovery.

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 Eromanga Basin has the potential to contain significant sandstone-hosted uranium mineralisation. Publicly available geophysical and geochemical datasets have been integrated into a 3D geological map for the Eromanga Basin. Initial uranium mineral system assessment has highlighted two regions of potential exploration significance: the region east of Mt Isa corresponding to the Euroka Arch and the area southwest of Lake Eyre.

Presented at Science at the Surveys Seminar, Melbourne, 22 March 2010