Aurora’s project portfolio includes a large number of calcrete uranium projects in the Yeelirrie region of Western Australia, held through its 100% subsidiary, Dawn Metals Limited, and through its 50% (approximately) subsidiary, Desert Energy Limited. These types of uranium deposits can be very valuable.
Initial drilling at Desert Energy’s Downs East and Old Station West projects, while focussing on only a small fraction of the prospective ground, has outlined the significant potential of the portfolio by identifying very large volumes of the target rock, calcrete, hidden beneath sand cover. Calcrete is the host rock to the world’s largest calcrete-uranium deposit at Yeelirrie (reported to contain 52,000 tonnes of U3O8) located in the same region.
Together, Aurora Minerals (through Dawn Metals Limited) and Desert Energy hold many uranium projects in the sand covered areas of the Yeelirrie region, the richest calcrete uranium province in the world. All of these projects are covered by a thin blanket of sand and soil, which has masked the potential presence of uranium deposits lying beneath the surface. Aurora and Desert Energy use sophisticated, modern techniques to identify the uranium targets through the sand, making them a compelling exploration targets.
Dawn Metals Limited also holds a significant number of similar exploration tenements and applications more widespread across central Western Australia, on the Yilgarn Block a noted host of uranium deposits.
In September 2008 a new government was elected in Western Australia with a strong pro-mining policy and indicating its intention to allow the mining of uranium. Aurora Minerals is well positioned with uranium exploration projects in this new pro-mining environment.
The Company’s Yilgarn Block Uranium project areas include Tertiary to Recent drainage channels where calcrete and/or other valley fill sediments have accumulated. The Yilgarn Block is host to the Yeerlirrie deposit and a number of other known Calcrete Uranium deposits, and a large number of uranium occurrences where mineralizing processes have been at work in the arid surface environment. The location of these occurrences is shown on the Yilgarn Block location map attached to this report.
Due to the large number of Aurora Minerals tenements, they have been grouped into North Murchison and South Murchison Project areas.
The Berringarra and Chesterfield tenements cover large sections of the soil and sand covered plain alongside the Murchison River and its main tributaries. Calcrete is exposed along the main present-day river channels and is inferred to exist beneath the recent soil and sand cover flanking the rivers.
The Downs and Charlie prospects cover uranium-channel radiometric responses over sections of various drainages along the northern edge of the Yilgarn Craton.
There is potential for calcrete-hosted uranium mineralization on tenements at Dawson and Old Station prospects. Airborne radiometric coverage shows uranium-channel anomalies coincident with mapped drainage and valley-fill sediments.
In the Gascoyne Complex of central Western Australia, known uranium deposits in Tertiary calcrete overlying Proterozoic granite and metamorphics include Minindi Creek, 250 km east of Carnarvon, and Jailor Bore, 200 km northeast of Carnarvon. The location map attached gives a broad overview of the distribution of known uranium occurrences in the Gascoyne Complex.
Desert Energy has a large ground position in the Gascoyne Complex including areas of uranium radiogenic granites, potential sources for uranium to be released into streams and deposited in sediments and drainage channels. Despite the numerous uranium occurrences in the area, previous uranium exploration within the tenements appears to have been localized.
Desert Energy's Yannarie Project is located over calcrete deposits along parts of the Yannarie River and its tributaries. These drain a large area of Proterozoic uranium-rich granites which host several uranium occurrences.
Within the Minnie Creek Project area, uranium mineralization has been identified at Middle Well, and nearby Poorinoo Well. The project covers the junction of the Alma and Edmund tributaries to the Lyons River which drain broad areas of radiogenic granite.
The Minnie Creek and Yannarie exploration licence applications cover 125 km of interpreted uranium-channel airborne radiometric anomalies and more than 165 km strike length of near-surface calcrete.
A government report records grades of 0.03% to a maximum of 0.15% U3O8 from surface grab samples by previous explorers in a small area at Minnie Creek. Follow up drilling of this area, over 150m by 50m, produced maximum grades between 0.03% and 0.07% U3O8. Previous exploration records up to 0.09% U3O8 in shallow drilling in the northern part of the Yannarie project. Follow up drilling of this area, over 10km by 3km grid produced samples up to 0.03% U3O8. The results demonstrate that the conditions in the area were potentially favourable for the formation of uranium, as the mineral carnotite, in calcrete.
Yannarie and Minnie Creek Projects lie north of the Paddy Well uranium prospect of U3O8 Limited, and south of the Manyingee uranium deposit of Paladin Resources (resource of 12,000t of contained U3O8).
Uranium in calcrete has been identified in tributaries to the Gascoyne River, and the Company’s tenement holding at the Glenburgh Project along the Gascoyne River and its tributaries holds potential for secondary uranium mineralisation, including areas covered by more recent river sediments potentially covering earlier-formed calcrete.
The re-processed airborne radiometric database at the Company’s Limejuice property has defined radiometric responses over targets with no or limited previous exploration and where potential for uranium mineralization is believed to exist.
Selection process
Desert Energy has a portfolio of tenement applications prospective for calcrete hosted uranium deposits in the Gascoyne and Yilgarn Provinces of Western Australia. Uranium deposits in calcrete are the largest of the near surface (surficial) deposits of which the Yeelirrie deposit in Western Australia is the best known example.
In Western Australia, Calcrete Uranium deposits and occurrences are believed to have been formed where uranium has been leached from granites in a semi-arid to arid climate, and transported along the creeks or rivers, to be redeposited in or near calcrete, at suitable “trap” sites within the drainage system.
In Western Australia calcrete tends to occur in valley fill sediments along Tertiary drainage channels and in playa lake sediments. The drainage channels can be up to several kilometres wide, and can be very long, with calcrete developed variably along the length. Uranium mineralization may, if geological and mineralizing conditions are favourable, be deposited in small portions of these channels.
Uranium mineralization is generally detected by measuring the response of its natural radioactive decay. Airborne radiometric surveys have been and continue to be used extensively in the exploration for uranium mineralization. These surveys can be followed up by closer spaced surveys in order to highlight the best anomalies for drilling.
In 2006 Desert Energy commissioned a specialist geophysical consultant group to compile a GIS database of available uranium channel airborne radiometric surveys over Western Australia.
Using this database, together with Geological Survey of Western Australia published mapping, the Company then proceeded to apply a series of selection criteria to identify acquisition opportunities in the Archean Yilgarn Block in the southern part of Western Australia, and the Proterozoic Gascoyne province in central Western Australia.
The preferred selection criteria included: