BASE METAL MINERALISATION

Oakdale have interpreted that the geology on Eyre Peninsula is favourable for hosting deposits of Archaean age: VHMS (“volcanogenic massive sulphide”) deposits containing zinc-copper (± lead) and nickel-copper sulphide deposits as well as structurally controlled zinc, copper and lead deposits.

 

Drilling has intersected a volcanic terrane ranging from komatiitic-basaltic-felsic composition interbedded with fine grained meta-sediments. The age of these rocks has been verified by Oakdale with lead isotope radioactive dating as 2540 (Ma) age.

The Malache base metal project is within the south-east portion of tenement EL4537. Drill hole BLDD004 intercepted19.2m at 1.8% zinc and 0.9% lead, plus 3.1m at 4.9% zinc further down the hole.

 

Geology and Mineralisation

Oakdale have interpreted that the geology on Eyre Peninsula is favourable for hosting deposits of Archaean age: VHMS (“volcanogenic massive sulphide”) deposits containing zinc-copper (± lead) and nickel-copper sulphide deposits as well as structurally controlled zinc, copper and lead deposits.

 

Drilling has intersected a volcanic terrane ranging from komatiitic-basaltic-felsic composition interbedded with fine grained meta-sediments. The age of these rocks has been verified by Oakdale with lead isotope radioactive dating as 2540 (Ma) age.

 

The exploration target deposits are thus similar to those in the Yilgarn and Pilbara Shields of Western Australia and the Canadian Shield. VHMS deposits containing zinc-copper (± lead) characteristically contain silver, gold and other metals occasionally recoverable as biproducts.

 

The structurally controlled base metal mineralisation at Malache contains gallium, germanium and indium as well as the principal metals. The Oakdale sequence is a package of meta- mafic volcanics, altered felsic volcanics, komatiites, graphitic schist, graphite-bearing feldspathic gneiss, sillimanite gneiss and various calc-silicates metamorphosed to the lower granulite facies.

 

Regional Exploration Activities within the Oakdale Tenements

Regional exploration work has included:

 

  • Flying of 2600 line kilometres of low-level helicopter aeromagnetic survey.

  • Completion of 694 new gravity stations on the Bramfield iron and Malache-Oakdale prospects.

  • Completion of 21 line km of ground magnetic surveying over the Bramfield, Kappawanta and Malache-Oakdale prospect areas.

  • Collection and assaying of 1640 calcrete geochemical samples. Petrological work, assaying and metallurgical studies have been integrated with this exploration.

 

The Lynch Group and its previous joint-venture partners have drilled 422 air core holes for 28 017 m, six RC drill holes for 1130 m, carried out 6551 line km of aeromagnetic surveying, 1304 line km of ground magnetic surveying and 27 line km of ground EM surveys.

 

MALACHE PROSPECT

Diamond drilling results at Malache Prospect

 

Drillhole BLDD04, (see Figure 1), the Malache Prospect discovery diamond drill hole, averages 0.45% zinc over 144.80 m, which includes the following: 92.27 m grading 0.67% zinc from 83.4 m to175.67 m, which includes:

 

19.2 m grading 1.77% zinc, 0.86% lead and 3.5ppm silver from 141.0 m to160.2 m, and 3.07 m grading 4.92% zinc, 3.3 ppm silver and 0.12 ppm gold from 172.6 m to 175.67 m

 

The “breccia hosted zinc” mineralisation is present in low temperature milled breccias, adjacent crackle breccias and fractures which cut across a high metamorphic grade metasedimentary and volcanic sequence. Sphalerite in the mineralisation is iron-poor and hosts high concentrations of indium, germanium, gallium and molybdenum.

 

Drill hole BLDD12 averages 0.36% zinc over 90.4 m, which includes the following: 7.00 m grading 0.38% zinc, 0.13% lead from 169.6 m to 176.6 m, 36.40 m grading 0.65% zinc, 0.19% lead from 191.6 m to 228.0 m. 5.50 m grading 0.36% zinc, 0.13% lead from 23.5 m to 241.0 m. 7.10 m grading 0.75% zinc and 0.36% lead from 308.3 m to 315.4 m. Several other 1.0 m intersections of <0.4% zinc are present.

 

The relationship between drill holes BLDD04 and BLDD12, which intersected a mineralised zone of similar thickness is shown on Figure 2.

 

Figure 2. Cross section through BLDD04 and BLDD12 - intersections and correlation.

 

The Malache Prospect (and Oakdale Prospect) diamond drill collars are shown on magnetic imagery, Figure 3.

 

Figure 3. Malache and Oakdale prospects - diamond drilling shown on magnetic imagery superimposed on topography

 

Hopping Jack Well Prospect – Base Metals and Uranium

It is known that the Oakdale Sequence is also present ~10km to the south-south-west where Stockdale intersected anomalous base metals in iron-rich meta-pelites/felsic volcanics (anomaly MH36; 14 m grading 0.25% zinc and 0.1% lead) near the Hopping Jack Well Prospect.

 

Air core drilling by Oakdale in 2011 located the Hopping Jack Well Prospect base metal mineralisation in a parallel major north-west trending shear system. Base metal values of up to 1.6% combined lead and zinc were assayed at the base of the air core holes. The system is open in all directions.

 

Diamond drill hole (KADD02) at Hopping Jack Well, designed to test the base metal target also intersected 10 m of uranium mineralisation in thin veins associated with an oxidised hematite breccias, with uranium values of up to 700 ppm.

Summary

At Malache, Oakdale is hopeful of discovering rich structurally controlled base-metal deposits, and believes that IP (induced polarisation) might be the most suitable technique to outline mineralised domains containing disseminated sulphides within this trend.

 

Oakdale also believes that the basic to felsic volcanic stratigraphy is favourable for the development of Volcanic Massive Sulphide (VHMS) deposits as well. Elecromagnetic surveys (EM) and Gradient Array Induced Polarisation (IP) will be used to explore for the base metal targets.

If the target contains enough pyrite, pyrrhotite and galena to form a conductor then these geophysical methods can detect the mineralisation. Sphalerite, the zinc sulphide is not very conductive, especially when pure or iron-poor.

 

The sphalerite at Malache has been shown to be mainly iron-poor but does have chalcopyrite and galena associated with it when high grade and thus detectable by geophysical methods. Nickel mineralisation associated with komatiitic basalts may occur in conductive sulphides and therefore selective combined EM and IP surveys can detect the mineralisation.

 

Aircore drilling along the known Malache structural zone, at least ~30km in length will also be used extensively. Also continued calcrete sampling and air core drilling of anomalous zones will be carried out on the extensions of the 35km long Malache/Tooligie shear zone and parallel structures, such as Hopping Jack Well.

 

RC percussion and/or diamond drilling of zones of interest would follow up any anomalies found when exploration commences after the graphite mineralisation has been evaluated.