The Nicholson Project is located some 350 km north-north-west of Mount Isa and a few kilometres south of the Proterozoic Walford Creek lead-zinc-silver-copper deposit. It consists of two granted exploration permits (EPM15670 and EPM18203). The area has very good potential for the discovery of a large Proterozoic base metal deposit.
The area was taken up to cover an east-west trending graben of prospective Proterozoic sediments which host the Walford Creek deposit. The Proterozoic sediments are covered by a variable thickness of later unprospective quartz-rich clastic sediments of the South Nicholson Group. The Walford Creek deposit lies within the graben and adjacent to the Fish River Fault which forms the northern boundary of the graben. EPM15670 originally covered the centre of the graben and the Nicholson River Fault which forms the southern bounding fault of the graben. EPM15670 has been reduced and now covers the area south of the Walford Creek Prospect and the area of the graben adjacent to the Northern Territory border. These are the areas where the cover rocks to the prospective sediments are thinner. EPM18203 generally surrounds EPM15670 and also covers the Hedleys Uranium Prospect.
During July 2007 Superior completed a higher resolution airborne EM (VTEM) survey over two areas within the Nicholson Project. Interpretation of this data as well as interpretation of the results from other EM surveys have been used in defining other targets within the area.
Walford South Prospect
A trial Tempest airborne electromagnetic (EM) survey was completed over the Walford Creek Deposit in 1998. The results of the survey were subjected to advanced modelling which showed conductive anomalies associated with the mineralisation at Walford Creek and also showed a conductive anomaly to the south of Walford Creek at Walford South. The Walford South anomaly extends across the boundary and into EPM15670. The Walford South conductive anomaly is considered to be a high-priority target for base metal deposits.
Superior compiled available historical gravity data for EPM15670 and the surrounding area. In the Walford South area this data showed a gravity anomaly which gave good support to the conductive anomaly from modelling of the Tempest EM results.
During 2009 Superior drilled three drill holes, for a total of 2435m of drilling, into the combined EM and gravity anomaly at Walford South. All drill holes intersected the Mt Les Siltstone, which was the target horizon, and terminated in the underlying Walford Dolomite. The drilling indicated a thickening of the Mt Les Siltstone and the overlying Doomadgee Formation towards the south and this was partly responsible for the intersections being deeper than predicted.
Pyritic shale was intersected within the Mt Les Siltstone in all drill holes at Walford South with the intersection in hole WS003 being slightly thicker than in the other holes. All holes contained some scattered areas of low-grade sphalerite (zinc) mineralization which were well below what could be considered to be economic grades.
The presence of substantial amounts of strongly pyritic shale in the drill holes is encouraging as pyritic shale halos are associated with many of the large stratiform lead-zinc-silver deposits in northwest Queensland and the Northern Territory.
A gravity survey was completed over the Walford South Prospect to assist future drill targeting. Haines Surveys of Adelaide completed the gravity survey which involved the reading of 870 gravity stations at 100m intervals along 24 lines spaced at both 200 and 400m intervals over the Walford South Prospect area.
The gravity survey largely validates the anomaly present in the earlier compilation of historical gravity data for the area but provides much more accurate detail than was previously available. The survey indicates a close association of the bouguer gravity anomaly with the Calvert Fault Zone with this fault forming the southern boundary to the main bouguer gravity anomaly at Walford South. The gravity data improves the prospectivity of the area adjacent to the Calvert Fault in that many of the large stratiform lead-zinc-silver deposits in northwest Queensland and the Northern Territory occur adjacent to large regional faults such as the Calvert Fault and the faults are considered to play important roles in the formation of the deposits.
Four target areas for further work have been identified from the gravity survey results. Modelling of the gravity data to produce a 3D density model has been completed to assist further drill targeting in the area. This density modelling indicates that the best of the gravity anomalies lies along the Calvert Fault Zone.
Nicholson West Prospect
The VTEM anomaly is apparently sourced by conductive material at a depth of about 300m and which is interpreted to be within the Mount Les Siltstone which is the host of the mineralization at the Walford Creek Prospect and is also the host of the pyritic shale drilled by Superior at Walford South. Where it outcrops to the north of Nicholson West, the Mount Les Siltstone contains scattered occurrences of vein-lead mineralisation which confirms its potential to host larger Proterozoic stratiform deposits of lead-zinc.
Conductivity sections derived by modelling of the VTEM data over Nicholson West compare favourably with similar sections over the deeper pyritic shale at the Walford Creek Prospect.
Preparations have been made for drilling of the Nicholson West Prospect with access and drill pads prepared in 2010. Drilling is proposed when funding is available.
Hedleys Uranium Prospect
The Hedleys Uranium Prospect lies within EPM18203. The prospect is a strong localised airborne uranium radiometric anomaly associated with the major Nicholson River Fault. The anomaly has previously been considered to be an anomaly related to radon gas dissolved in spring waters. No drilling has been done on the area.
Superiorís work in the Nicholson Project area indicates that the anomaly lies approximately 100 to 150m above the major unconformity between the sandstones and siltstones of the South Nicholson Group and the underlying carbonaceous siltstones of the Doomadgee Formation and the Mt Les Siltstone.
A number of major uranium deposits in the Athabasca Basin of Canada and the Alligator River Region of Australia lie on or close to unconformities between Proterozoic reduced crystalline rocks and overlying sandstones. There has been some interest in the prospect from other parties. Interest should increase when the uranium price returns to previous levels. The Hedleys Uranium Prospect warrants drilling when funding becomes available.