The unconformable relationship eluded to above is directly analogous with the geological setting of the Alligator Rivers region of the Northern Territory, which hosts the world-class Ranger, Jabiluka and Koongarra uranium deposits. There, Pine Creek Orogen rocks, of similar composition to the Tanami Group, are unconformably overlain by the extensive flat-lying McArthur Basin sequence, which is correlated with the Birrindudu Basin. There are 12 identified uranium and/or rare earth occurrences within the area which generally occur at the Mesoproterozoic unconformity, including The Don, Killi Killi and Mt Mansbridge. Toro believes that the Tanami region has exceptional potential to host “blind” Proterozoic unconformity style uranium deposits. In addition, there is also rare earth and gold prospectivity.

 
PREVIOUS EXPLORATION

Gold and base metals have been explored for in the region since the discovery of gold at Tanami in the early 20th century. Within the last 40 years, uranium exploration has been limited and areas of exploration have concentrated on basement exposures and the observable unconformity with the Mesoproterozoic sandstone. Within more recent times, Northern Uranium and their strategic partner Areva have followed up a number of uranium and rare earth occurrences with drilling.

Figure 2: Birrindudu tenements, surface geology and known mineral occurrences.

EXPLORATION OBJECTIVES

Toro Energy will be pursuing an unconformity exploration model and has 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 in the basement.
•     Identify alteration in the sandstone cover that may be consistent with an unconformity model.
•     Utilise existing geophysical datasets (EM, magnetics and radiometrics) to identify 
       targets future drilling.

EXPLORATION COMPLETED

Following the desktop review of previous exploration, Cameco conducted three airborne geophysical surveys over the project area in 2007 and 2008. Radiometric and magnetic, and Tempest and VTEM electromagnetic surveys, were completed. The EM in particular identifies numerous prospective conductive features in the basement of possible stratigraphic (graphite) and structural origin.

EXPLORATION IN 2010

Currently, Toro is exploring for high grade uranium near the unconformity using a modified Athabasca Basin model, focussing exploration on conductive basement structures and alteration plumes evident in electromagnetic data. Of secondary interest are interpreted palaeochannels in the western part of the project area.

During 2010, thirteen aircore holes for 950m designed to test airborne electromagnetic trends, indicative of a large palaeochannel system, were drilled in the western part of the project area (refer Figure 3). Drilling showed that there are no significant permeable sands and that the conductive character can be adequately explained by shallow saline (>10000ppm TDS) groundwater present in the Tertiary clays. This 100m thick cover sequence is underlain by ubiquitous grey siltstones of the Canning Basin.

During 2010, Toro also undertook Reverse Circulation (RC) drilling of unconformity targets in the eastern and central parts of the project area (Ringer Soak and Ventura respectively; Figure 3). A total of five holes for 804m were drilled. The most encouraging results were from drill holes BR0001 and BR0003 at the Ventura prospect, coincident with a major WNW structure defined in magnetic data (refer Figure 4).

Dark grey, sulphidic and possibly graphitic alteration was intersected in Gardiner Sandstone over a 30m interval at approximately 45m depth in both holes (refer Figure 5). Various elements are elevated up to 10 times background in this zone including K, Al, U, Cu, Zn, Pb, Ag, As, Se and Tl. The mineralogy is currently being investigated. This zone is interpreted to be an alteration plume from a deeper source, perhaps at or near the unconformity.



Figure 3: Airborne EM image of the Birrindudu Project area with 2010 drill locations

Hole BR0002, drilled only 200m to the north of this alteration zone, intersected 253m of silicified sandstone and pelitic volcaniclastic sediments of the Gardiner Sandstone. Minor uranium anomalism to 27ppm U₃O₈ in chemical assays was encountered in the pelites. The depth of the unconformity and the lateral distribution of the alteration zone are currently not constrained by drilling or electromagnetics and will be a focus of exploration in Q3 2011. RC drilling at Ringer Soak was only partially completed due to start of the wet season rains.

During the year, Toro also collected soil samples from unconformity target areas throughout the Birrindudu Project, the results for which are expected in Q1 2011. These are expected to constrain the anomalism at Ventura and generate further targets for drill testing in 2011. Toro recently completed the $1m Earn-In expenditure requirement for triggering of the Joint Venture agreement with Cameco.

EXPLORATION PROPOSED FOR 2011

The anticipated exploration for Birrindudu in 2011 will involve Q3 drilling at the Ventura prospect and completion of the drill program at Ringer Soak. This may require ground EM to focus drill targets.  In addition, other target areas that are generated from soil sampling will be followed up and infilled.
 



Figure 4: Airborne magnetic image (first vertical derivative) of the Ventura prospect area showing the location of 2010 RC drill holes



Figure 5: RC sample pulps showing comparison of grey and graphitic altered, with adjacent unaltered Gardiner Sandstone.