- Kalkaroo contained copper metal increased by more than 80% to 1.14 million tonnes and contained gold by more than 60% to 2.77 million ounces (excluding 0.52 million ounce gold cap).
- New resource estimate follows inclusion of data from an additional 74 holes (previously reported) and extensive re-interpretation, block modelling and re-estimation work by an experienced, independent resource geologist.
- Kalkaroo copper-gold deposit mineral resource estimate now stands at 232.5 million tonnes at 0.49% copper and 0.37g/t gold (equivalent of 0.79% copper), using a 0.4% copper equivalent lower cut-off.
- Resource estimate does not include significant unquantified credits of molybdenum, cobalt and sulphur or the higher grade gold cap.
- The deposit remains open at depth and along strike, with considerable scope for expansion.
- Represents one of the largest undeveloped copper-gold deposits in Australia.
The new resource estimate is: 232.5 million tonnes at 0.49% copper and 0.37 g/t gold for 1.14 million tonnes of contained copper and 2.77 million ounces of contained gold (at a 0.4 % copper equivalent lower cut-off) in JORC measured, indicated and inferred resources as summarised in Table 1. This excludes a substantial gold cap of 21.7 million tonnes at 0.74 g/t gold for 515,000 ounces of contained gold (using a 0.2 g/t lower cut-off, see Table 1 in link below).
The Kalkaroo deposit does not outcrop, and the revised resource incorporates all drillholes in the earlier 2012 resource model plus some additional drillholes that have been previously reported, including:
- 69 infill aircore holes at West Kalkaroo that were designed to improve confidence levels in the saprolite gold and native copper mineralisation (reported in ASX announcement of 29 November 2013).
- 5 diamond drillholes that were designed to test the down-dip depth extensions of the primary sulphide mineralisation in the Kalkaroo main zone area (reported in ASX announcement of 30 November 2012).
An experienced independent resource geologist incorporated the updated geological interpretations and additional drilling data provided by Havilah into the new resource model. A detailed summary of the resource estimation methodology used and all of the supporting data is provided in Appendix 1, which is taken from Table 1 of the 2012 version of the JORC code. During the process extensive consistency checks were run against the 2012 resource model, and for the measured and indicated resources, the contained copper and gold metal contents are within the limits of estimation errors for the two models. The inclusion of a sizeable inferred resource component for the first time brings Havilah's reporting in line with its peers who have reported appreciable inferred resources for their copper deposits (eg Rex Minerals and Altona Mining).
The grade-tonnage curves attached demonstrate the potentially large metal inventory available if mining efficiencies allow lower cut-off grades to be achieved and highlight the very substantial copper potential of the Kalkaroo deposit.
The mineral resource includes both secondary ore and primary sulphide ore as detailed in Table 2 (see link below). Primary sulphide mineralisation at Kalkaroo consists of chalcopyrite - pyrite below approximately 140 metres depth, which marks the base of total oxidation over most of the deposit. During extended periods of deep weathering the primary sulphide minerals were progressively dissolved and the metals reconstituted and enriched at shallower depths to produce a consistent vertical zonation of secondary ore types comprising from top to bottom: a gold cap (lacking copper and therefore modelled separately), native copper and chalcocite as shown in the picture below (refer to link below). This gold cap provides a potential early cash flow bonus as it will be mined to access the deeper copper-gold resource and better than 97% gold recoveries have been achieved in cyanide bottle roll leach tests.
This resource estimate takes no account of the substantial molybdenum and cobaltian pyrite credits in the Kalkaroo deposit, which it is expected could be recovered in additional flotation cells after the copper concentrate. With increasing cobalt demand, the cobaltian pyrite offers the prospect of deriving additional revenue from Kalkaroo, especially if roasted to recover all the valuable components, including cobalt, gold, sulphur, iron ore and electric power (refer to conceptual chart in ASX release of 7 March 2017).
Earlier scoping studies based on the 2012 resource model and also applicable to the new model indicate that to develop Kalkaroo at its optimum throughput rate will require an estimated capital investment of at least $350 million. The substantial additional inferred resource reported here underscores the potential opportunity to considerably extend the mine life and thereby enhance the project economics. It is also noteworthy that the Kalkaroo deposit is open at both ends along strike and on all drilling sections at depth, so there is good scope to increase the resource size with further drilling.
Havilah Managing Director, Dr Chris Giles, commented: "With some additional strategic drilling, the Kalkaroo copper and gold resource has been considerably expanded to over 1.1 million tonnes of copper and almost 3.3 million ounces of gold.
"The full extent of the Kalkaroo deposit remains untested and we are confident that further drilling will continue to expand the resource.
"Kalkaroo is somewhat of a rarity these days in being a large undeveloped open pit copper-gold deposit in a low sovereign risk and logistically favourable jurisdiction.
"New copper mining developments have slowed at the very time when copper usage is expanding with the highly copper intensive renewable energy generation and storage revolution, not to mention electric vehicles and antimicrobial applications.
"A copper and gold combination of metals is good to have, as they are natural hedges against each other - gold being driven to a large extent by uncertainty and instability and the so called Dr Copper by stable industrial production and economic development.
"The large metal inventory means that with careful attention to capital and operating costs, Kalkaroo can potentially turn into a multi decade copper-gold mining operation of long term significance to South Australia.
"We would like to attract a partner with suitable expertise and financial ability to help us develop the deposit, and we are willing to trade project equity for finance and development experience with the right partner.
"In the meantime, we will continue to systematically tick off key tasks which to date have included securing land ownership, finalisation of the mining lease proposal and the present resource upgrade".
About the Kalkaroo deposit
Kalkaroo lies 55 km north of the Barrier highway and transcontinental railway line, roughly 100 km west of Broken Hill and 450 km northeast of Adelaide. It is situated on a 550 km2 pastoral lease, which is owned by Havilah.
Kalkaroo is an extremely continuous and geologically consistent 40 - 80 metre thick stratabound copper-gold deposit that has been drilled over a 3 km strike length. It has a distinctive arcuate shape and a shallow 30 - 45 degree dip owing to replacement of a favourable stratigraphic horizon, that follows the north-plunging nose of a large structural dome. Later faulting and vein emplacement is associated with local displacement and enrichment of the mineralisation, particularly at West Kalkaroo.
Deep weathering of the primary sulphide deposit has produced a consistent sub-horizontal stratification of secondary supergene enriched mineralisation comprising from top to bottom:
1. Supergene gold in saprolite (gold cap) with insignificant copper.
2. Native copper and gold in saprolite.
3. Chalcocite dominant with gold, recoverable by conventional flotation.
4. Primary sulphide mineralisation - chalcopyrite dominant with gold and locally rich molybdenum, recoverable by conventional flotation to produce a comparatively high grade copper concentrate with no penalty elements (eg uranium and arsenic).
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About Havilah Resources Ltd
Havilah Resources Ltd (ASX:HAV) has successfully financed and developed its first gold mine at Portia in north-eastern South Australia, which is a high margin operation producing a steady cash flow. It plans to follow on with two copper-gold developments that can potentially support an initial production of at least 34,000 tonnes of copper and 105,000 ounces of gold annually. This is underpinned by a JORC minerals resource inventory of over 900,000 tonnes of copper and 2.4 million ounces of gold.
Havilah Resources Ltd