LOCATION AND ACCESS

The Amadeus Project covers prospective ground of the Amadeus Basin, south and west of Alice Springs in the Northern Territory (Figure 1). Granted tenements are solely on pastoral (native title affected) land, but there are a number of applications on Aboriginal freehold (ALRA affected) land, most of which are in moratorium. Access is provided by the Mereenie Loop Road and Stuart Highway from Alice Springs. Toro currently has access agreements in place for two of the granted tenements, but obtaining physical access has proven difficult thus far due to local issues.

Figure 1:  Location of Amadeus Project tenements. Granted tenements have no pattern fill, while applications are stippled. Cross hatched tenements are in moratorium.

GEOLOGICAL SETTING

The project tenements lie largely within the Amadeus Basin (Figure 2), a large intracratonic sedimentary basin containing (broadly) Neoproterozoic to Carboniferous sediments covered by some surficial Tertiary and Quaternary deposits. Palaeo- to Meso-proterozoic metamorphic rocks of the Arunta Complex unconformably underlie much of the northern Amadeus Basin.

Figure 2:   Geological setting of the Amadeus Project. The brown tone depicts Arunta basement and the pink tone indicates Neoproterozoic to Carboniferous basin cover (Amadeus Basin).

The tenements cover part of the mapped Hermannsburg Sandstone which stratigraphically equates with Pertnjara Group comprising Upper Devonian – Lower Carboniferous fluvio–continental sediments. This sequence and its equivalents hosts the Pamela and Angela uranium deposits south of Alice Springs and the Bigrlyi, Walbiri, Malawiri and Dingo’s Rest uranium deposits of the Ngalia Basin to the north.

Uranium mineralisation in the Ngalia and Amadeus Basins is localised at redox interfaces in the Devonian-Carboniferous sequence. These interfaces can be peneconcordant or lateral or both. They are stratigraphically related to the tops or lateral terminations of reduced sequences contained in oxidized, red-bed sequences. The reduced beds are grey or sometimes white where bleaching has occurred by oxidation of sulphides (pyrite). Pamela and Angela are hosted in the upper-most member the Undandita Member. The Bigryli deposit is hosted towards the top of the Mt Eclipse Sandstone. The other deposits in the Ngalia Basin occur at a similar stratigraphic level.

In the central Australian Fold Belt, there is evidence of significant remobilisation of uranium from the radiogenic Arunta basement into the overlying Proterozoic, Palaeozoic and Tertiary sedimentary cover units, including the Ngalia, Amadeus and Tertiary Basins. The uranium deposits at Bigrlyi, Napperby (New Well) and Angela attest to this.

In the vicinity of the Amadeus West tenements (ELs 25049 and 27183), there is exposure of an exhumed Tertiary palaeochannel with a strong radiometric signature (Figure 3). The origin of this signature is unknown, but is likely to be surficial enrichment of uranium and other radionucleiides onto ferruginous crusts on outcrop. However, this may be an indicator of subsurface primary mineralisation.

Figure 3:  Regional radiometrics (uranium channel) showing the strong signature of exhumed Tertiary palaeochannels and the Mereenie Sandstone of the Amadeus Basin.

PREVIOUS EXPLORATION

Uranium has been explored for in the area in the 1970s and 1980s, culminating in the discovery of the Angela-Pamela deposits, 25 km south of Alice Springs (11500 t of U3O8 at 0.13% - UIC June 2005; currently Cameco-Paladin JV). However, the nature of the exploration has been largely restricted to shallow near surface vacuum drilling and surface sampling, in search of evidence of redox features and geochemical variations that may indicate deeper ‘Angela style’ uranium within the Pertnjara Group. This form of exploration is likely to have been ineffective, as the depth of modern weathering is well beyond the penetration of the vacuum drilling system. Toro believes there is reasonable scope to test the ‘Angela’ hypothesis via deeper drilling and potentially, airborne EM. Petroleum exploration has also been active in the region, focussed on the Amadeus Basin, which has two producing gas fields, Mereenie and Palm Valley. These gasfields are nearby to Toro’s tenements and this fact is considered highly supportive of applying the sedimentary uranium model to other parts of this Basin.

EXPLORATION OBJECTIVES

The principal exploration model that will be pursued is the Angela-style uranium in a foreland sedimentary sequence of the Amadeus Basin. After reviewing of the available data and reports, Toro composed the following objectives for this project:

·        Determine the nature of regional and local radiometric responses in outcrop.

·        Identify reduced facies or evidence of redox changes that may relate to hydrocarbon migration.

·        Image the sedimentary cover and internal structure using modern techniques such as EM.

·        Develop tools for exploration in this terrain that may also be applicable to other similar-aged basins, including geochemical and geophysical.

EXPLORATION COMPLETED

In 2006/2007, the first year of grant, Nova Energy (now a 100% held subsidiary of Toro) carried out the following activities:

·        Acquisition of selected open file reports by previous explorers

·        Acquisition of all Northern Territory Government and Geoscience Australia data

·        Acquisition of digital Landsat satellite imagery

·        Compilation of all the above into a database

·        Geological interpretation of the satellite imagery

·        Interpretation of the database to generate exploration targets.

Following this desktop review, a helicopter-assisted reconnaissance program was carried out, aimed largely at assessing the redox state and facies of the Pertnjara Group in the southern part of the project area. A number of tenements were relinquished in the Idracowra area following this exercise, but the Waterhouse tenement in particular was considered highly prospective and was maintained. Attempts to undertake shallow aircore or RC drilling have been unsuccessful because Traditional Owners have objected to exploration, despite an agreement being in place with Nova Energy. Clearly sentiment changes through time and is difficult to predict. An unsuccessful meeting was held in 2009 and a final meeting to determine Toro’s path is scheduled for later in 2010.

EXPLORATION IN 2010

The exploration programme for 2010 will largely involve helicopter-assisted sampling of the Amadeus West tenements (ELs 25049 and 27183) for surficial uranium in an exhumed Tertiary palaeochannel that has a strong radiometric signature (Figure 3). If negotiations for access onto the Waterhouse tenement are successful, a RC drilling program may be launched later in 2010.