The Republic of Ireland is one of the largest zinc producers in Europe and its base metal deposits have drawn some of the biggest names in the mining business — from Boliden and Glencore (LON: GLEN) to Teck Resources (TSX: TECK.B; NYSE: TECK) and Vedanta.
Junior explorer Connemara Mining (LON: CON) and Group Eleven Resources (TSXV: ZNG) hope their Stonepark deposit in Limerick will one day join the island’s illustrious list of zinc deposits.
The partners completed a resource estimate in April showing that, while still small, it is high grade, with an inferred resource of 5.3 million tonnes grading 8.55% zinc and 2.60% lead, or 11.5% zinc and lead combined. The resource is based on 88 diamond drill holes totalling 37,270 metres, and uses a cut-off grade of 4.5% zinc-equivalent.
Stonepark is next to Glencore’s Pallas Green zinc project, one of the largest undeveloped zinc projects in the world. Pallas Green, 1 km east of Stonepark, has an inferred resource of 44.2 million tonnes grading 8.4% zinc and lead combined, or 7.2% zinc and 1.2% lead. The deposit occurs over an area of 4,000 metres by 4,000 metres and from 300 metres to 1,300 metres below surface.
Patrick Cullen, Connemara’s president and CEO, says the orebodies at Stonepark and Pallas Green are contiguous and the centres of each deposit are 5 km apart.
“They’re the same. They’re just different expressions of it, I suppose,” he says in a telephone interview from Ireland. “If Glencore were to develop a mine at Pallas Green then you could make a safe bet that something would have to happen at Stonepark. That would be a win for Connemara.”
In terms of scale, however, Stonepark “would have to be bigger before you start talking about a mine, but it’s open along strike, and it’s a fairly flat-lying deposit. It’s relatively shallow.”
The deposit occurs at depths ranging from 190 metres to 395 metres and consists of flat-lying, stratiform (1- to more than 7.5-metre-thick) lenses of massive to semi-massive sphalerite, galena and pyrite hosted in 10- to 75-metre-thick hydrothermal alteration bodies (mostly black matrix breccia) within the Waulsortian limestone.
Connemara and Teck jointly discovered Stonepark in 2007, and the resource estimate was based on drilling Teck completed between discovery and 2011.
Group Eleven bought Teck’s stake in the project at the end of last year for $2.5 million. Teck has a 4.5% net smelter return royalty (NSR). (Group Eleven can buy back part of the NSR in incremental stages after delivering a preliminary economic assessment and a feasibility study.)
Group Eleven owns 76.56% of the project, and Connemara the other 23.44%.
Stonepark’s resource is contained in three main zones: Stonepark North, Stonepark West and Stonepark. Most of the tonnage lies in the high-grade Stonepark North body, which has 4 million tonnes grading 11.95% zinc and lead (9.10% zinc and 2.86% lead), and lies 190 metres to 240 metres below surface.
The partners restarted drilling to gain a better understanding of the structural controls of the mineralization, and Group Eleven wants to determine whether exploration success at Pallas Green can be replicated within the same limestone units in adjoining areas. The Limerick basin underlies Stonepark as well as Group Eleven’s contiguous PG West property.
Cullen notes that Group Eleven was interested in buying Connemara’s stake in Stonepark when it bought Teck’s stake in the project, but Connemara didn’t want to sell.
“We’ve been in zinc for a long time and it’s starting to bear fruit,” Cullen says.
In addition to Stonepark, Connemara has a joint venture with Teck at its Oldcastle zinc project, 20 km northwest of the giant lead-zinc ore deposit at the Tara mine, operated by Boliden of Sweden. Teck is earning a 75% stake in the Oldcastle project.
Ireland makes 25% of Europe’s total zinc production, and holds the Lisheen, Tara, Tynagh, Silvermines and Galmoy zinc deposits.