MARKET RELEASE 5 th August 2013

Transcription

1 ACN MARKET RELEASE 5 th August 2013 ROCKLANDS COPPER PROJECT (CDU 100%) SIGNIFICANT QUANTITIES OF COPPER MINERAL CUPRITE (88.8% Cu) ASSOCIATED WITH NATIVE COPPER AND CHALCOCITE ORE ZONES AT LAS MINERALE Cuprite rarely identified during exploration and infill drilling, and only appeared in minor quantities during metallurgical test-work of 35 tonnes of wide-diameter (PQ) diamond core, suggesting it was not observed during geological logging and assay due to brittle powdery characteristics. Figure 1: Significant quantities of the copper mineral cuprite (88.8% Cu) appears to be associated with the Las Minerale native copper and chalcocite ore zones. Cuprite was rarely identified during geological logging of both RC and diamond drilling, in spite of the fact many holes intersected the cuprite-rich zones currently being mined. Due to the brittle and powdery nature (when struck) of the cuprite identified to date at Las Minerale, it is possible it was missed during logging and potentially washed out of impact-hammer drilling such as Reverse Circulation (RC) drilling. Inset shows XRF analysis of cut area of sample (LE = light elements). Unit 34, Brickworks Annex,19 Brolga Avenue, SOUTHPORT 4215 Phone: Facsimile: admin@cudeco.com.au

2 Significant Quantities of Copper Mineral Cuprite (88.8% Cu) Associated with Native Copper and Chalcocite Ore Zones at Las Minerale Significant quantities of the copper mineral cuprite (cuprite contains 88.8% Cu metal), appears to be associated with the Las Minerale native copper and chalcocite ore zones. Cuprite was rarely identified during geological logging of both RC and diamond drilling during exploration and infill drilling at Las Minerale, in spite of the fact many holes intersected the cuprite-rich zones currently being mined. Metallurgical test-work previously conducted on 35 tonnes of large-diameter (PQ) diamond drill core, recovered minor quantities of cuprite from the bulk-sample along with native copper in the gravity jigs. The density of cuprite is high at approximately 6.1 tonnes/m 3 (native copper = 8.9 tonnes/m 3 ) suggesting a significant quantity is likely to be captured with native copper during gravity separation...based on appearance of magnetite recovery (magnetite = 5.2 tonnes/m3) at similar stages in the process. Due to the brittle and powdery nature (when struck) of the cuprite identified to date at Las Minerale, it is possible cuprite was missed during geological logging and potentially washed out of samples collected from impact-hammer drilling in wet ore areas, such as may have occurred with Reverse Circulation (RC) drilling in central Las Minerale. Figure 2: Examples of separate large coarse native copper agglomerates recently unearthed at the Las Minerale Starter Pit, just 15-20m below surface. Image to the left shows zone of high-grade native copper and cuprite that has been mapped at the base of the pit for over 25m. The image to the right shows soft sooty chalcocite crystals (blue-grey colour) falling out of voids within the coarse native copper and associated cuprite like confetti down the face of the excavation...it is thought that during exploration drilling, much of this soft sooty chalcocite washed out of the vuggy drill-core due to high pressures required to maintain water returns during drilling, and has not been included in assay results. Native copper contains 99.65% Cu, cuprite contains 88.8% Cu and chalcocite contains 79.85% Cu. Page 2

3 Figure 3: Example of the brittle, powdery nature of Las Minerale cuprite (88.8% Cu). Left; original sample and right; hit just twice firmly with a small geologists hammer, shatters easily into small flakes and powdery residue. Similar losses were identified in twin-hole drilling programmes comparing results of RC and diamond drilling for both native copper and chalcocite copper mineral recoveries from Las Minerale, which recent mining activities have confirmed. Significant native copper agglomerates have been identified that occur in east-west faults that cross-cut the main ore direction and appear to have played an important role in the enrichment process. Due to their orientation, it appears very few drill holes have actually intersected these zones and when they have, were effectively treated as outliers during resource estimation modelling. Many of the native copper agglomerates identified to date are several metres wide and contain zones of near sold native copper and include cuprite and chalcocite copper minerals, suggesting higher grades were clearly possible. The Rocklands Resource Block Model applies heavy discounts to the calculation of shallow oxide ore due to the often sporadic distribution of copper species in heavily oxidised and/or colluvium based ore profiles, especially within flood-plains, such as occur over central Las Minerale. Ore grades in areas above the coarse native copper zone mined to date have been higher than predicted by the resource model, which for the most part has been expected by the Company. Significant quantities of additional ore that was NOT originally included as ore in the mining schedule, has also been diverted to stockpiles for later processing that was previously destined for the waste dumps. Average grades of the Figure 4: Boulder of near-solid native copper oxide ore containing malachite, native copper, cuprite and chalcocite. Page 3

4 Figure 5: Native copper ore is categorised into two main types; native copper oxide and; native copper sulphide. These in turn are divided into high-grade and low-grade categories. The native copper ore type is determined based on the dominant copper species remaining after the native copper metal has been removed and becomes an important classification to ensure appropriate treatment of the remaining copper minerals as they progress through the process plant. Ore examples shown above are from the high-grade native copper (oxide) stockpile, that has been found to contain significant quantities of cuprite and chalcocite. All details shown above highlight high-grade copper ore (estimated between 8-10% Cu), containing malachite, azurite, chalcocite, cuprite and native copper minerals. Sample 1 (cuprite) was broken in two and an end cut-off with a diamond saw to reveal a near solid cuprite core (with some native copper and minor malachite). The cuprite was tested via XRF analysis (see figure 1) and assayed between 81-86% Cu on several attempts. The sample tested was approximately 320mm x 140mm x 120mm in size, weighed approximately 30kg and as such contains an estimated 26kg of copper metal in this small piece of ore. Page 4

5 Figure 6: Above; low-grade copper oxide ore stockpiles appear unexciting until you break open some fresh-rock or wash-down the green clays that dominate the oxide zones and cover the ore. Above centre; fresh-broken oxide ore showing copper species malachite, chalcocite, cuprite and fine native copper minerals and top right; detail showing cuprite (grey-blue-red minerals). Figure 7: Activity in the middle of the Las Minerale Starter Pit. A temporary native copper oxide stockpile can be seen at the bottom right, planned to be used for commissioning of the crushing circuit. high-grade oxide zone that does not include native copper is estimated at 5-8% CuEq, with localised areas returning grades as high as 20% CuEq. The Rocklands Process Plant has been designed specifically to treat native copper in all fraction sizes expected at Rocklands, with German designed and manufactured alljig native metal recovery systems included at a cost of more than A$20m. This same alljig process plant is used globally by companies for the recovery of primary and native metals including BHP Billiton and Anglo American. The process plant can treat up to 20% Cu (200kg per tonne Cu) in the form of native copper, whilst concurrently processing oxide (including cuprite), supergene and primary sulphide ores in a continuous, single-circuit copper recovery process flow-sheet. Sophisticated Stockpile Management Plan With mining underway and a significant stockpile inventory building, a sophisticated ore and stockpile management plan is being implemented. The characteristics of stockpiled ore are dictated by Process Plant requirements, which the pit geologists use to determine ore segregation logistics based on both species and grade categorisation. The goal is to be capable of presenting the various ore types and grades to the ROM when and as required. Page 5

6 Figure 8: Mining block-model at RL210, with ore types and grades delineated in the upper oxide zones. The image on the left is marked out as outlines on the based of the pit and the image on the right, which has added grade details, is used by the pit-spotters and geologists to identify which ore goes where on the stockpiles, subject to in-pit confirmation. The current mining schedule employs a mining rate 1.5 times that required, (ie. 4.5m tonnes of ore per annum is mined instead of 3mt), which facilitates high-grading the front end of the mill feed process. Extensive economic studies show this approach results in a net increase in revenues even after the higher costs of mining, but in doing so also results in the added bonus of leaving free ore at surface on the stockpiles for later processing, resulting in significantly reduced mining costs in later years. In essence, mining is being timed to provide high-grade ore for when the plant becomes fully operational. Some of the highest grade ores at Las Minerale occur between depth, and these are the depths planned to be sitting on the top of the stockpiles by the time they are required. Accelerated aging studies show negligible loss in recoveries of stockpiled ore for the anticipated timeframes with a simple adjustment of the flotation regime for sulphide ore types, and native copper and oxide ore is not affected by aging for the planned mining periods. Figure 9: Pit mark-up at RL210 in a section of the Las Minerale starter pit. The areas marked include chalcopyrite (CPY), chalcocite (CC), native copper (NatCu), Oxide (Ox) and ore-based waste (W). In the middle stands a PVC drill collar from a decommissioned inpit dewatering borehole. The ore zone is approximately 50m wide at this location. Page 6

7 Figure 10: Activity in the middle of the Las Minerale Starter Pit. The flat area to the left of the foreground digger has been marked out for mining of ore (see figures 8 & 9). The above image shows waste on flanks of the main ore main zones being mined. The previously mined box-cut is in the middle ground between the two diggers. The higher mining rate and stockpiling scenario also provides additional benefits, including maintaining a contingent ore supply in the unlikely event the pit becomes inaccessible for any reason, and/or alternative monetisation options such as crushing and simple beneficiation of stockpiled ore to concentrate grades as a separate programme to ore being directly fed into the process plant. These options are also being incorporated into the Rocklands stockpile management plan. The current strategy, based on the increased mining rate, is to mine the first 30mt of ore in just over 6 years instead of 10 years. After high-grading the ore-feed to the mill, remaining ore will be stockpiled, resulting in between 9-12mt tonnes of ore sitting on the stockpiles at the end of year 6. At this point we have several options; Decommission the mining fleet, retaining only required plant to shift the remaining free ore from the stockpiles to the ROM pad, resulting in significant cost reductions. Keep mining past year 6 and continue to high-grade the mill feed as per the first 6 years - requires amendment to the EA. Increase the process plant capacity to 5 million tonnes per annum or more and subsequently extend mining beyond 10 years based on our measured and indicated resource of 97.9 million 0.96% CuEq (0.4% CuCoAu cut-off - see notes to the resource statement from page 6) - requires amendment to the EA. The crushing circuit was purchased from EMS/Index Australia, was designed by Trio in the United States, and is capable of crushing up to 5 millions tonnes of ore per annum depending on the final crush size and operating configuration. For example, if the final-crush size is increased to -50mm (from the current - 38mm), throughput increases to around 5.7 million tonnes per annum. The Crushing Circuit will initially operate at just 3 millions tonnes per annum, comfortably under nameplate throughput capacity. The company is also investigating the option of beneficiation of mined ore prior to mill-feed, utilising specially designed ore-sorters that will at least double the grade of mill-feed ore presented to the mill. Whilst these ore-sorters are capable of generating beneficiated ore to well over 20%, the plan is to limit this to between 2.5-3% head-grades. Associated high-grade coarse native copper will be additional to the above, as the Rocklands plant is capable of accepting head grades up to 25% Cu (20% native copper and 5% other ore types concurrently). Page 7

8 Figure 11: Current mining of waste either-side of the box-cut that accessed coarse native copper ore to be used for commissioning of the crushing circuit. The ore zone is approximately 50m wide at this location. In the interim, the Company is focussing it's investigation on the use of ore sorters for beneficiation of ore coming directly from the pit to produce a Direct Shipping Ore (DSO) product for early sales, either using the Company s mobile crushing circuit, or soon to be commissioned three-stage Crushing Circuit. Recent test-crushing of native copper ore through the mobile crushing circuit exceeded all expectations, further enhancing the possibility of generating near-term DSO ore. The Company recently held discussions with smelters, and other processing companies in relation to this possibility. Yours faithfully Peter Hutchison Executive Director Page 8

9 Competent Person Statement The information in this report that relates to Exploration Results is based on information compiled by Mr Andrew Day. Mr Day is employed by GeoDay Pty Ltd, an entity engaged, by CuDeco Ltd to provide independent consulting services. Mr Day has a BAppSc (Hons) in geology and he is a Member of the Australasian Institute of Mining and Metallurgy (Member #303598). Mr Day has sufficient experience which is relevant to the style of mineralisation and type of deposits under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined in the 2004 Edition of the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ores Reserves. Mr Day consents to the inclusion in this report of the information in the form and context in which it appears. The information in this report insofar as it relates to Metallurgical Test Results and Recoveries, is based on information compiled by Mr Peter Hutchison, MRACI Ch Chem, MAusIMM, a full-time executive director of CuDeco Ltd. Mr Hutchison has sufficient experience in hydrometallurgical and metallurgical techniques which are relevant to the results under consideration and to the activity which he is undertaking to qualify as a Competent Person for the purposes of this report. Mr Hutchison consents to the inclusion in this report of the information, in the form and context in which it appears. Rocklands style mineralisation Dominated by dilational brecciated shear zones, throughout varying rock types, hosting coarse splashy to massive primary mineralisation, high-grade supergene chalcocite enrichment and bonanza-grade coarse native copper. Structures hosting mineralisation are sub-parallel, east-south-east striking, and dip steeply within metamorphosed volcanosedimentary rocks of the eastern fold belt of the Mt Isa Inlier. The observed mineralisation, and alteration, exhibit affinities with Iron Oxide-Copper-Gold (IOCG) classification. Polymetallic copper-cobalt-gold mineralisation, and significant magnetite, persists from the surface, through the oxidation profile, and remains open at depth. Notes on Assay Results All analyses are carried out at internationally recognised, independent, assay laboratories. Quality Assurance (QA) for the analyses is provided by continual analysis of known standards, blanks and duplicate samples as well as the internal QA procedures of the respective independent laboratories. Reported intersections are down-hole widths. Au = Gold Cu = Copper Co = Cobalt Zn = Zinc CuEq = Copper Equivalent Copper Equivalent (CuEq) Calculation The formula for calculation of copper equivalent is based on the following metal prices and metallurgical recoveries: Copper: $2.00 US$/lb; Recovery: 95.00% Cobalt: $26.00 US$/lb; Recovery: 90.00% Gold: $ US$/troy ounce Recovery: 75.00% CuEq = Cu(%) x Co(ppm) x Au(ppm) x In order to be consistent with previous reporting, the drill intersections reported above have been calculated on the basis of copper cut-off grade of 0.2% Cu, or a copper equivalent grade of 0.35%, with an allowance of up to 4m of internal waste. The recoveries used in the calculations are the average achieved to date in the metallurgical test-work on primary sulphide, supergene, oxide and native copper zones. The Company s opinion is that all of the elements included in the copper equivalent calculation have a reasonable potential to be recovered. Page 9

10 Disclaimer and Forward-looking Statements This report contains forward-looking statements that are subject to risk factors associated with resources businesses. It is believed that the expectations reflected in these statements are reasonable, but they may be affected by a variety of variables and changes in underlying assumptions which could cause actual results or trends to differ materially, including, but not limited to: price fluctuations, actual demand, currency fluctuations, drilling and production results, reserve estimates, loss of market, industry competition, environmental risks, physical risks, legislative, fiscal and regulatory developments, economic and financial market conditions in various countries and regions, political risks, project delays or advancements, approvals and cost estimates. Page 10