Lundin Mining Corporation (TSX:LUN)(OMX:LUMI) has announced further high-grade copper intersections at its recently discovered Semblana copper-rich massive sulphide deposit located adjacent to its 100% owned Neves-Corvo mine in southern Portugal.
Seven additional drill holes have been completed since the discovery news release and base metal assays for three of these holes have been received. Significant intersections from the three assayed holes include:
- 20 metres at 3.47% copper (including 7 metres at 5.48% copper) in hole PSK48;
- 39 metres at 2.59% copper (including 11 metres at 7.02% copper) in hole PSK48-1; and
- 13 metres at 4.14% copper in hole PSK50-2.
Surface exploration drilling has continued to intercept a thick massive sulphide lens underlain by extensive stockwork sulphides, now delineated over an area exceeding 800 x 300 metres. The sulphide deposit is currently constrained by only one hole on the western side, three widely spaced holes on the eastern side and is completely open to the north and south.
Neil O'Brien, Senior Vice President of Exploration and New Business Development for Lundin Mining commented, "Our drilling has now intersected strong sulphide mineralization in 16 holes, six of which contain very significant copper mineralization.
"While we have lots of drilling yet to do, Semblana is growing into the type of high-grade resource that can significantly contribute to future copper production.
"Combined with the current copper resources and nearly 100 million tonnes of zinc resources, the future of Neves Corvo as a leading, long-life copper-zinc producer looks very good," Dr. O'Brien said.
(Note: as disclosed in August 31, 2010 news release, as of June 30, 2010 total zinc resources at Neves Corvo were 58,047,000 tonnes grading 6.2% zinc in the Measured category, 13,929,000 tonnes grading 6.9% zinc in the Indicated category and 26,791,000 tonnes grading 4.9% zinc in the Inferred category)
Neves-Corvo Development
Neves-Corvo has two processing plants capable of treating copper and zinc ores. It has a single shaft that is responsible for hoisting of all ore and waste. Shaft capacity has recently been increased to an estimated 4.6 million tonnes per annum and this remains as the strategic constraint to production volume.
Potential future production from Semblana, and any further new discoveries, has to be considered in light of this shaft constraint. Whilst incremental increases may be possible, until significant new infrastructure is constructed the development of Semblana will need to be co-ordinated with existing production and the on-going development of Lombador, potentially necessitating production choices on the basis of highest net return.
Mine development studies, including consideration of the need for a second shaft, are presently constrained by the knowledge available on Lombador, Semblana and other near-mine resources. Lundin Mining's exploration effort is now being significantly increased to obtain a better understanding of the ultimate potential of Neves-Corvo in order to facilitate these mine development studies.
Neves-Corvo Exploration Strategy
Exploration effort at Neves-Corvo over the last three years has been focussed on the discovery of new copper resources to supplement and replace mature producing orebodies. This has been successful in replacing mined production and adding new copper resources and reserves as well as rapidly expanding the zinc resources in the higher-grade Lombador deposit.
However, Neves-Corvo remains under-explored, particularly at deeper levels (greater than 700 metres below surface), and the ability to plan longer-term infrastructure development is restricted as a result. Drilling from surface accurately to these depths is expensive and slow. It is considered uneconomic to drill at a close enough spacing from surface to support resource estimates on which mine plans can be assessed.
To support long-term mine development and expansion studies, Lundin Mining is pursuing a three-fold exploration strategy at Neves-Corvo as follows:
- The access ramp to the Lombador orebody is being accelerated to reach a depth of 900 metres below surface by Q1 2012. Exploration drives from the ramp will allow in-fill drilling of the copper and zinc resources for detailed mine planning. It will also allow cost effective further exploration that will be key to gaining a full understanding of the zinc, and more importantly copper, mineralisation associated with Lombador.
There remain high-priority exploration targets at Lombador where drill-testing could discover significant additional new resources that would further impact these mine development studies.
In order to fund the development of the ramp, a small upper section of Lombador South has been under-going feasibility studies and is expected to be complete in Q1 2011.
- Semblana is being explored initially from surface with five drill rigs. An 80,000 metre surface drilling program is planned for 2011 which will deliver an initial resource estimate for Semblana prior to the end of 2011. Drilling will be focused on step-out holes to determine the ultimate limit of this large deposit and to search for additional copper-zinc rich zones as well as on in-fill holes to provide data for the resource estimate.
Once Semblana is better understood, access options can be assessed to ensure maximum utilisation of existing infrastructure.
- The discovery of Semblana will significantly contribute to future copper production at Neves Corvo and it has also opened up new target areas for exploration. Accordingly a 24 square kilometre high resolution 3D seismic survey, to cover the entire near-mine area is planned, which will attempt to detect other nearby massive sulphide lenses.
An earlier seismic survey, carried out in 1996, was able to clearly detect the large Lombador massive sulphide lens at depths exceeding 1000 metres.
It is estimated that this program may take as long as three years to complete and that infrastructure development options will be evaluated in parallel to this.
Commenting on the exploration programme at Neves-Corvo Mr. Phil Wright, President and CEO said, "We continue to view Neves-Corvo as under-explored and are very encouraged by the results to-date.
"Our efforts over the last few years have enabled us to replace mined copper production and add to reserves. However, this has generally been at lower-grade which means we have to move more tonnes in order to maintain copper production.
"Semblana is the first time we have seen something enriched in copper at a significant scale that offers the potential of a rejuvenation of Neves-Corvo's copper business.
"We remain very optimistic on the longevity of our copper and zinc production at Neves-Corvo," Mr. Wright said.
Sampling and Analytical Protocol:
NQ sized drill core was logged, cut in half with a diamond saw and sampled by Company personnel at its facilities at the Neves-Corvo mine. Mineralized intervals are analyzed for a suite of elements including Zn, Cu, Pb and Sn at the Neves-Corvo laboratory using XRF methods. Bob Carmichael, P.Eng., General Manager, Resource Exploration, is the Qualified Person as defined by National Instrument 43-101 and has reviewed and approved the technical information contained in this release.
Source: Lundin Mining Corporation