JUST three years after listing on the ASX, copper and gold explorer Horseshoe Metals is galloping towards success, following a 40 per cent increase in the copper resource for its flagship Horseshoe Lights project.
The resources were added to the mineral resource estimate for the Kumarina project, established in and March, the company now boasts an overall copper metal inventory of 148,000t within WA’s highly prospective Peak Hill Mineral Field.
Through its wholly-owned subsidiary Murchison Copper Mines, Horseshoe Metals holds a 100 per cent interest in both Horseshoe lights and Kumarina, which cover 297.1 square kilometres of mining tenements north of Meekatharra.
Horseshoe Lights
The Horseshoe Lights project comprises 16 tenements across 79.98sqkm. The deposit was discovered in 1946 an mined until 1994, during which time it produced more than 300,000oz of gold and 54,000t of copper. The mine produced at rates of about 1.7 per cent copper and 2.9 grams per tonne of gold, leading Horseshoe Metals to report that the area had demonstrated significant mineralisation.
A drilling program undertaken during 2010 and 2011, and then 2012 and 2013 – comprising 94 reverse core drill holes, nine diamond drill holes and threediamond tails for 19,951m – returned encouraging results such as 4.3m at 2.6 per cent copper, including 1m at 10 per cent copper and 0.1g/t gold.
Drilling proved the copper mineralisation to be consistent with geological modelling. It also confirmed the potential for further down dip and plunge extensions to the south and west of the existing open pit.
In June these results were used to update the project’s JORC-compliant measured, indicated and inferred mineral resource to 12.85 million tonnes grading 1 per cent copper and 0.1g/t of gold, for 128,600t of copper and 36,000oz of gold (using a 0.5 per cent copper cut-off grade). This result was a 40 per cent increase on the 2011 resource estimate, and about 30 per cent of the new resource estimate fell within the measured and indicated categories.
Horseshoe Metals managing director Neil Marston told Proactive Investors that the company’s forward plan was to add tonnes to the resource.
“We have target areas at Horseshoe Lights with little drilling, and we will step-out on the eastern side to follow up historical plus 1 per cent copper intercepts,” Mr Marston said.
With continued drilling, Horseshoe Metals would be well-positioned to substantially expand the resource in the copper rich region, he said.
A detailed geophysical study for the project was completed during the June quarter using all exploration data generated by the company in the last three years, as well as historical soil sampling and drilling data.
The aim of the study was to obtain the best possible understanding of the geology at and surrounding the historicalHorseshoe Lights mine and to identify exploration targets for the next stage of drilling.
“The study has identified large fold and thrust structures at mine corridor scale, and tracked the very detailed location of the east-west trending thrust fault that separates the Bryah Group from the Bangemall Group,” the company stated.
“Several historical copper and gold soil geochemical anomalies have been identified south of the Horseshoe Lights mine on the adjoining exploration licence and prospecting licences in Ravelstone Formation rocks which warrant follow-up exploration.
“Five east-west drilling transects have been recommended to cross the more prominent geochemical anomalies and adjacent structures.”
A down hole electromagnetic survey began at the project in July, aimed at testing for off-hole conductors that could represent large sulphide copper-gold mineralisation within the Narracoota Formation, where it lies largely untested beneath the overlying Ravelstone Formation.
“Overall…there remains excellent potential to substantially grow the copper inventory at the Horseshoe Lights project with targeted drilling and exploration in other largely untested areas,” Horseshoe Metals stated.
The Kumarina project comprises one exploration licence and one mining lease covering 217.1sqkm. Copper deposits on the tenements were discovered in 1913 and worked intermittently until 1973. These workings were undertaken across a series of pits, shafts and shallow open cuts that covered almost 3km.
The main pit, Kumarina copper mine, was entirely underground with drives from the main shaft extending for about 200m in the upper levels and for about 100m in the lower levels at a depth of 49m below surface.
“Records indicate that the Kumarina copper mine was the second largest producer in the Bangemall Basin group of copper mines,” Horseshoe Metals stated.
The mine was worked until the late 1960s and recorded production of 481t at a grade of 37 per cent copper and 2340t at a grade of 17.51 per cent copper, however the current tenement area has been subjected to only limited modern exploration.
Satellite imagery interpretation completed by Murchison Copper Mines in 2009 identified several high priority targets for detailed exploration anddrilling by Horseshoe Metals in 2011 and 2012 identified significant copper mineralisation at the Rinaldi prospect.
In February, a maiden JORC-compliant measured, indicated and inferred mineral resource was established for the Rinaldi prospect: 835,000t grading 1.3 per cent copper for 10,600t of contained copper metal (using 0.5 per cent copper cut-off grade).
Two other prospects have been identified at the project, Kumarina Deeps and Snell North.
The Kumarina Deeps prospect is a strong aeromagnetic anomaly running for about 1km, 250m below surface.
“Drilling activities originally planned for June 2013 were postponed due to delays in obtaining the necessary heritage survey clearance which were originally planned for May 2013,” Horseshoe Metals reported.
The company now expects to receive heritage survey clearance by the end of September.
“As a result of the delay in obtaining site access, the company’s co-funding
grant from the WA State Government, under the Exploration Incentives Scheme, expired on 30 June, 2013,” it reported.Horseshoe Metals is able to re-apply for the next round of co-funding, due to open in August/September.
The Snell North Prospect, which is about 1km west of the Great Northern Highway, was identified in 2012 as part of a regional soil sampling program. The prospect comprises two sets of historical workings along an interpreted dolerite intrusive. The workings are about 340m apart and consist of three vertical shafts between 10m and 15m deep, with evidence of horizontal workings running off the shafts.
In July, Horseshoe Metals undertook ground reconnaissance at the Snell North prospect, and some of the other soil anomalies identified by the 2012 soil sampling.
“Rock samples collected from the mullock piles around the shafts show that copper in the form of Chalcocite, Malachite and possibly other copper oxides was being mined,” the company stated.
“Hand held XRF [X-ray fluorescence] copper readings taken of the rock samples are very encouraging. No sulphide minerals are evident in the samples collected however this is not unexpected considering the depth of the workings.
“Importantly, there is no evidence of any drilling along the line of this structure which extends for several kilometres to the [south-southwest].”
Horseshoe Metals reported that it intended to drill test the Snell North prospect as soon as possible.
Looking to the future
The company reported that its future plans would include undertaking a preliminary economic assessment of Horseshoe Lights; pending positive results, this would be followed by a preliminary feasibility study.
Meanwhile, further drilling would be undertaken down dip and down plunge of the main zone and exploration activities would focus on identifying geophysical targets showing repetitions of the main zone.
“The area east of the Horseshoe Lights open pit is of particular interest as it has a complex geological setting that was difficult to interpret from airborne geophysics due to the data interference created by the old plant,
buildings and other infrastructure,” the company reported.
Horseshoe Metals reported that it would undertake a ground-based magnetic survey using east-west orientated lines at 25m spacing during the September quarter to evaluate the area. The company also plans to begin the next phase of drilling to the east of the open pit.
At Kumarina, exploration would focus on drilling the southern extension of the Rinaldi prospect, the old Kumarina copper mine, regional targets and the Kumarina Deeps prospect.
Horseshoe Metals reported that during the September quarter it would conduct additional field reconnaissance work of soil anomalies to identify potential drill targets; obtain approval from the Department of Mines and Petroleum for drilling at the Snell North prospect; undertake a heritage survey of proposed drill sites at the Kumarina Deeps, Snell North, and any other proposed drilling locations; and begin drilling once heritage survey site clearances were obtained.