Perth, Sep 11, 2008 AEST (ABN Newswire) - Copperco Limited (ASX:CUO)(PINK:CPPWF) announce an updated Measured, Indicated and Inferred Mineral Resource estimate for the Lady Brenda Prospect has returned 5Mt at 0.6% Cu, using a 0.3% Cu cut-off grade for 29,300 tonnes of contained copper metal. This estimate represents a 179% increase in contained copper from the inaugural Lady Brenda resource estimate, reported 29 November 2007, from 10,500 tonnes to 29,300 tonnes.
A relatively high degree of confidence in the Mineral Resource is demonstrated by 52% of total resource tonnage contained within the Measured and Indicated categories. As a consequence of the Lady Brenda Mineral Resource update, the Company's global Mineral Resources now total 40.5Mt at 0.8% Cu (350,200 tonnes of contained copper metal), after depletion of resources due to mining at Mount Clarke and Flying Horse.
The Lady Brenda Mineral Resource adjoins the Lady Annie Deposit, and offers some synergies and efficiencies for future mining in conjunction with Lady Annie. Further potential for lateral oxide mineralisation extensions and deeper sulphide mineralisation will be evaluated by future drilling programmes
Background
The Lady Annie Copper Project is the flagship of CopperCo's Mount Isa tenement holding located 137 km's north of Mount Isa. The Project currently encompasses oxide copper Ore Reserves of 144,010 tonnes of copper metal (ASX Release of 12 June 2008), from global oxide and sulphide resources of 40Mt at 0.9% Cu, containing 358,700 tonnes of copper metal.
The Project will initially mine five ore bodies over a 6.5 year mine life (as of September 2008) by conventional open pit mining. Ore will be treated by a heap leaching, solvent extraction and electrowinning process (SX-EW). Mining operations commenced in June 2007, development of the mine and processing infrastructure has been completed and first production of copper cathode from the Lady Annie Project occurred in October 2007. The Company is currently producing at an annualised rate of 19,000 tonnes per annum ("tpa"), ramping up to 25,000tpa by end of December 2008, and to 30,000tpa by mid-2009. Construction for the production ramp-up will be completed this month. The current mining plan does not yet include Ore Reserve estimates for the Lady Brenda or Anthill Prospects.
The Company continues to see great potential for further resource development on the Company's tenure within the region. Now that a solid foundation has been established for the oxide copper leach operations, the Company will continue to explore for further oxide copper resources to replace reserves, and assess the potential to extend mine life for the oxide copper heap leach operations. Attention is also being directed at sulphide resources beneath the oxide caps at Lady Annie, Flying Horse, Mount Clarke and Buckley River. The conceptual target for exploration is to ultimately define sufficient suphide copper resources to support a 20,000 tonne per annum 10 year mine life copper in concentrate operation.
Lady Brenda Prospect - Resource Modelling and Estimation
Resource modelling of copper mineralisation at the Lady Brenda Prospect, located immediately south and southwest of the Lady Annie Deposit has been completed by consultants CSA Global Pty Ltd. A total Measured, Indicated and Inferred Mineral Resource estimate of 5Mt at 0.6% Cu containing 29,300 tonnes of contained copper has been generated at a 0.3% Cu ore cut-off grade.
The updated Mineral Resource estimate for the Lady Brenda Prospect represents a 179% increase in contained metal from the previously reported figure of 1.9Mt at 0.6% Cu for 10,500 tonnes of copper (ASX Release of 29 November 2007). The total proportion of the resource tonnage in the Measured and Indicated categories is 52%, representing a relatively high degree of confidence in the estimate due to the extensive drill coverage, and well documented, and understood geological controls on mineralisation.
The Mineral Resource includes both oxide and sulphide material. The oxide proportion comprises 2.8Mt at 0.6% Cu, containing 16,600t of copper metal. The sulphide proportion comprises 2.2Mt at 0.6% Cu, containing 12,700t of copper metal. Oxide mineralisation is potentially amenable to shallow open-pit mining and SX-EW treatment, pending mine optimisation studies.
The Mineral Resource has been estimated using the Ordinary Kriging methodology for grade estimation, the method considered most suitable for this style of deposit. Mineralisation is estimated within a wireframe constructed with reference to the geological and structural model for the deposit, as well as analytical copper grades. Mineralisation is subdivided into a subhorizontal oxide domain and a shallow westerly dipping sulphide domain. The resource estimate has been checked using a second method, that of Inverse Distance Weighting, and has produced similar validatory results.
All laboratory analyses on resource definition drill samples have been conducted by an ore grade technique utilising a mixed acid digest with AAS determination. Systematic Quality Assurance/ Quality Control (QAQC) procedures involving insertion and monitoring of regular duplicate, standard, and blank samples are in place.
A block model generated within the mineralised wireframe utilises a block cell size of 10m x 10m x 5m, with a sub-block size of 2.5m x 2.5m x 2.5m. These sizes are considered appropriate for the style of deposit, the level of contained data, and the method of mining to be applied.
Some partial geographic overlap of the Lady Annie and Lady Brenda Mineral Resource models has resulted in the re-allocation and transfer of some minor low grade resource blocks from Lady Annie to Lady Brenda. As a consequence there are also some minor revisions to the previously reported Lady Annie resource model and estimate (ASX Release of 29 November 2007).
In summary, detailed resource modelling has comprised:
- Database validation
- Geological modelling and wireframing of mineralised zones
- Variography and statistical analyses
- Block modelling, and
- Resource estimation
As previously defined, oxide mineralisation is that which overlies the base of complete oxidation (BOCO), a sub-horizontal weathering surface delineated from logged drill data.
Sulphide mineralisation underlies the oxide zone. Bulk density figures used for the estimate were 1.8 for oxide material, 2.7 for transitional sulphide material and 2.8 for primary sulphide material. These figures are based on numerous determinations on diamond core from both Lady Brenda and Lady Annie.
As a consequence of the Lady Brenda Mineral Resource update, the Company's global Mineral Resources now total 40.5Mt at 0.8% Cu, containing 350,200 tonnes of copper metal. After allowance for resource depletion of 2.7Mt at 1% Cu from mining at Mount Clarke and Flying Horse, the figures represent a 5% increase in total pre-mining resources, and demonstrate the Company's ability to replenish depleted resources and reserves.
About the Lady Brenda Mineral Resource
The Lady Brenda Mineral Resource adjoins the Lady Annie Deposit, and is located immediately southwest of the planned pit for Lady Annie. Lady Brenda lies within an area of structural complexity caused by the intersection of several major fault structures. Copper in soil anomalism (+50 ppm Cu) is widespread. Historic drilling through the area was not systematic and much of the deeper drilling targeted sulphide copper, with minimal evaluation or analyses of the oxide zone. Systematic RC drilling by CopperCo during 2007 defined an inaugural Inferred Mineral Resource of 1.9Mt at a grade of 0.6% Cu for 10,500 tonnes of contained metal. Both RC and diamond drilling programmes have continued evaluation of the prospect area since late last year.
The resource model for Lady Brenda now covers a 700 metre strike interval from 811,400N on the southeastern margin of the prospect through to 812,100N on the northwestern margin.
Resource modelling is based on RC drilling at cross-sectional intervals of 25 - 50m, with drill hole spacing of 50m on section. CopperCo has completed total drilling of 18,296m in 174 drill holes since early 2007. This total comprises 17,720m of RC drilling in 169 drill holes and 576m of diamond drilling in 5 drill holes at the prospect. Drill holes are subject to regular down hole surveying, and collar positions have been surveyed using RTK-DGPS. This drilling has all been completed to relatively shallow depth, focussing on delineation of oxide mineralisation.
Mineralisation occurs in two main sub-parallel, northerly trending, shallow westerly dipping, structurally controlled mineralised zones. Host rocks are variably weathered siltstones, sandstones and carbonaceous shales, equivalent to those hosting the Lady Annie mineralisation. Oxide mineralisation occurs predominantly as malachite and minor azurite, both distributed on joint, fracture and bedding surfaces. Sulphide mineralisation occurs as chalcopyrite (+/-minor chalcocite), associated with carbonate-quartz vein stockworking and brecciation.
Oxide mineralisation forms a variably thick sub-horizontal blanket overlying and adjacent to primary mineralised zones. Both eastern and western zones of mineralisation display strike extents in the vicinity of 400m - 500m each. Mineralisation is continuous between the two zones over a short central interval where the combined mineralised width of the prospect approaches 600m. Together, both zones of mineralisation have a combined areal extent in the vicinity of 700m x 700m.
The resource is composed predominantly of oxide mineralisation located above a geological horizon called the Base of Complete Oxidation (BOCO), controlled by geological logging of drill holes. The BOCO surface is differentiated on the basis of iron oxide and primary carbonate content, and lies at levels generally in the range of 40m - 80m vertical depth. Mineralisation below this level falls into the sulphide category (either transitional or primary sulphide).
Several deeper historic diamond drill holes have revealed strong potential for sulphide mineralisation beneath the oxide zone with a best historic result of 29m at 1.73% Cu from 192m depth in drill hole R107/ P092. Oxide mineralisation also remains open and untested to the south of the western mineralised zone.
Future drilling programmes will target oxide extensions to the south of the western mineralised zone. Optimisation studies on the oxide zone at Lady Brenda are being scheduled. Deeper sulphide evaluation drilling programmes are being planned, and will accompany sulphide evaluation drill programmes for Lady Annie East. A sulphide resource comprising 8.9Mt at 0.9% Cu (77,700t of contained copper) has already been defined at Lady Annie West and the potential for additional sulphide resources at both Lady Annie East and Lady Brenda is considered high.
Contact
Brian Rear
Managing Director
Tel: +61-8-9260-8800
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