Projects - Overview

Limbla

The Limbla project area is believed to be highly prospective for uranium mineralisation, particularly of the unconformity type:

• Regional geophysics shows large areas of basement with elevated uranium values, providing a source.
• The Illogwa Creek Schist Zone has been recognised as a crustal scale feature of tectonic significance12.
• Metapelites and carbonates of variable metamorphic grade from greenschist to amphibolite facies are the most favourable host rocks12.
• Strong structural controls are evident, including the Albarta fault and Star Creek fault.
• The Harts Range Group and/or Amadeus Basin sediments may represent a Kombolgie sandstone equivalent, providing a cover to preserve deposits.
• Modern exploration data and processing techniques have been applied by WDR to vector new areas not previously investigated.   At Albarta, significant U/Th ratio anomalies adjacent to detailed drilling in 1978 remain untested.
• In the southern part of the tenement group the regional geophysical image clearly highlights unexplored areas of elevated uranium.

Proposed exploration

The following exploration program is proposed for the Limbla area.

• Extensive detailed airborne geophysical surveys, comprising helicopter-borne magnetics and radiometrics.
• Ground radiometric surveys and geological mapping of anomalies identified by the airborne survey.
• Ground EM or IP surveys at specific sites to identify possible sulphidic or graphitic zones which may represent a reducing environment in the concealed unconformity surface.
• Percussion drill testing of targets generated, with attendant radiometric logging and/or geochemical assay

Burt Plain

This project comprises an area of about 800 square kilometres located 40 kilometres north of Alice Springs.  The area of interest was originally identified as an iron ore prospect from government aeromagnetic data.  Further analysis by WDR suggests the area is highly prospective for copper-gold-(uranium), nickel and other mineralisation. 

High grade metamorphics of the Palaeoproterozoic Arunta Block crop out in the north-east part, and sporadically in the western part, of the tenement.   Interpretation of government aeromagnetic and gravity information shows anomalies indicative of a huge iron oxide system.  The source of the geophysical anomalies is concealed beneath recent cover.  It is interpreted to be seven km long by five km wide, and is in places within 50 metres of the surface.  This area, called the Capricorn prospect, has many attractive exploration attributes:

• The geophysical anomalies are consistent with known geophysical responses over IOCGU style mineralising events.
• The geophysical signature is comparable with that over the giant Olympic Dam deposit in South Australia.
• The magnetite-rich zones may have associated molybdenum and tungsten.
• The geological setting is similar in rock type and age to the Voisey’s Bay nickel deposit in Canada (137 Mt @ 1.59% Ni)14.
• A further analogue is mafic intrusion of the Norlisk type(1.5 billion tonnes @ 0.57% Ni and 1.1% Cu)15.
• Geographically very close to Alice Springs – easy access to site and services.
• Prospect is trannsected by the Stuart Highway and Australasia Railway line.

The aeromagnetic anomaly is the highest total magnetic intensity reading in the Northern Territory.   It indicates a local area of intense magnetite concentration, and reflects extreme conditions in terms of geological, structural and metamorphic history of the area.   These sites are the preferred loci for accumulation of economic mineral deposits during mineralising fluid movement episodes.

The gravity data shows a coincident anomaly of about ten milligals.  The magnetic intensity is a direct result of magnetite concentration.   Magnetite is the most magnetic mineral, and has a high specific gravity, or density, of about 5.1 grams/cc.   The combined magnetic/gravity expression clearly indicates a substantial accumulation of magnetite.   If an oxidising event has subsequently occurred, then some of the magnetite may be altered to hematite. The presence of sulphide mineralisation is also possible.

It is interesting to note that the aeromagnetic data show other, weaker magnetic anomalies occurring in the area.   Significantly, the complex at Capricorn prospect is the only one with a coincident gravity anomaly.

Previous drilling near the northern edge of the complex intersected strong magnetite mineralisation between 40 and 75 metres vertical depth (minimum 6% mtt).   Results from advanced interpretation of the aeromagnetic data indicate zones up to 20% magnetite.

It is expected that many holes may be required to complete a first-pass test of the prospect.   To put the size of the complex into perspective, it would require 22 holes just to test the >10% magnetite zone on a one x one kilometre grid.

Of particular interest is the U/Th ratio data, which shows a general correlation of elevated values with drainage patterns.   Significantly, the highest U/Th ratio values occur in the central eastern part of the tenement area, adjacent to inferred and mapped structures.  This further expands the uranium exploration opportunities in the project area to include roll-front deposits in palaeochannels incised in basement, and calcrete deposits.

Proposed exploration

• Induced polarisation survey over the Capricorn prospect to define conductive areas possibly representing sulphides or reducing environments.
• Ground gravity survey on a 200x200 metre grid over the Capricorn prospect.
• Synthesis of magnetic, gravity and IP interpretations to provide direct drill targets to investigate the magnetite-rich and/or conductive zones of the complex.
• Field follow-up including geological mapping and ground radiometric surveys over the uranium/thorium anomaly.
• Drilling of selected targets.   Five holes to 500 metres are proposed initially.

Spring Hill

Spring Hill is located in the Pine Creek Gold Field, 150 km south of Darwin.   The tenement package comprises an 1100 ha Mining Lease Application surrounded by the 36 km2 Exploration Licence.

The project area is in the southern part of the Palaeoproterozoic to Mesoproterozoic Pine Creek Geosyncline, straddling a regional shear zone, the Pine Creek shear.   The shear is related to a number of significant gold deposits in the region.   Importantly, Spring Hill is within the Pine Creek Orogen, which hosts the Alligator Rivers Uranium Field (ARUF).   In addition to an Indicated Resource of 3.6Mt at 2.34 g/t containing 274,000 oz of gold, the area is highly prospective for uranium deposits6.

Mining first commenced at Springhill in 1882.  Historical recorded gold production is 21,170 ounces.  The deposit is hosted by sediments of the Mount Bonnie Formation.   Subsequent deformation has created the southerly plunging asymmetric Springhill anticline, whose western limb hosts most of the gold mineralisation as either sheeted quartz veins (Hong Kong zone) or axial planar lodes and saddle reefs (Main and East Lodes).   The Union Reefs plant located 15 km from Spring Hill operated profitably treating low-grade (0.7 grams/tonne gold) ore during the last years of its operational life, and is well suited to treat Springhill ore of similar tenor23.

McDonald Speijers24 completed a resource estimate in 2003, based on the Billiton/Ross Mining 1988-94 drill hole database (254 holes 24,000 metres).  Their figure of 3.6Mt averaging 2.34 grams/tonne gold (274,000 ozs) is classified as Indicated under the JORC code of 1999 (1.0 g/t cut-off grade).   WDR intend to conduct an updated feasibility study to re-evaluate the economics of the resource at current gold prices.

Further gold exploration potential has been identified:

• Extensions to the identified resource, both at depth and along strike.
• The sulphide zone beneath the middle lode workings, are virtually untested.
• Re-interpretation of existing EM data indicates the presence of untested conductors at depth.

Sulphide-associated gold mineralisation in areas of similar structure/stratigraphy to the north of existing workings.