Zinc, gold mining in Ireland flourish

Materials World magazine
,
25 Mar 2019

Ireland has had several mines close down, but it still ranks highly for policy and investment. 

Ireland continues to rate highly in the Fraser Institute (FI) annual survey of mining companies, which is completed by senior mining executives. At the time of going to press, the results of the 2018 survey of 83 jurisdictions had just been released.

Nevada and three other jurisdictions in the USA make up the top 10 for mining investment, as well as four from Canada and two from Australia. However, FI also compiles its Policy Perception Index (PPI), a report card informing governments of the attractiveness of their mining policies.

Geology and economics are important factors for exploration – a region’s policy climate is also an important investment consideration. The PPI is a composite index that measures the overall policy attractiveness of the 83 jurisdictions. Policy factors include uncertainty concerning administration, the environment, legal structures, taxation and land claims. Ireland sits fourth in the PPI rankings. The PPI top 10 is more geographically diverse than the previously mentioned investment index, as it incorporates four European jurisdictions, of which Ireland is the most respected.

This popularity has not, however, prevented a degree of uncertainty in recent years, as the country experienced the closure of several zinc operations. ‘Most recent closures have come from Irish mines that have been depleted of ore, i.e. Galmoy and Lisheen,’ Hannan Metals CEO Michael Hudson told Materials World. ‘Further dedicated exploration efforts are required for the next generation of mines to be found and subsequently operated in Ireland.’

Of course, Irish mining is not just about zinc, as BTU Metals announced encouraging figures from metallic exploration in Galway last May, while Hannan Metals continues its own exploration for a raft of metals.

Zinc of Ireland

The mid-2016 merger of ASX-listed Global Metals Exploration with the Australian public company Zinc Mines of Ireland, under the title Zinc of Ireland, has led to this new company exploring for Irish zinc from what it describes as a consolidated and dominant position. Key to this is a 1,000km2 land-holding spanning Ireland’s major mineral provinces, including tenure close to Ireland’s three largest zinc-lead deposits – Navan, Lisheen and Galmoy.

Zinc of Ireland is optimistic, basing this view on zinc’s status as the fourth most commonly used metal globally, after iron, aluminium and copper. A revitalised economy with demand for products such as zinc in the construction and automotive sectors underpins this optimism. The company has been helped in recent years by the closure of other zinc operations – Century mine in Australia and the Lisheen mine in Ireland closed, removing 600,000-700,000lb per year from the market.

One further boost comes from zinc’s role in zinc bromine batteries, which are an effective option for large-scale power storage. Some analysts are forecasting that an additional 3.0-3.5 million tonnes (Mt) of zinc are now required to balance the current deficit and meet the forecast demand.

Zinc of Ireland’s initial exploration lies in the Kildare Mississippi Valley Type (MVT) project, 40km south-west of Dublin. It includes several advanced zinc prospects containing both Irish-type and MVT mineralisation, along with numerous drill-defined prospects.

Kildare hosts numerous MVT zinc-rich breccia, with the favourable Waulsortian limestone host rock forming a bed across the district. A maiden high-grade inferred resource of 5.2Mt grades 7.2% zinc and 1.4% lead for 374,400t of contained zinc and 72,800t of contained lead, as determined in June 2017.

A recently completed diamond hole returned what Zinc of Ireland describes as a ‘spectacular intersection’ of 23.25m grading 12.7% zinc plus 1.0% lead, significantly extending what is called the Base of Reef mineralisation. This is one of the key mineralised horizons at Kildare, and demonstrating significant potential to grow the resource.

Further good news came Zinc of Ireland’s way in July 2017 with the discovery of high-grade zinc at the Celtic Tiger prospect. Here, one diamond hole intersected strong zinc mineralisation over multiple horizons, not least a best intercept of 2.85m grading 20.2% zinc and 0.88% lead.

BTU Metals

BTU Metals Corporation focuses its gold exploration work on its Dixie Halo Gold project in Ontario, Canada. In 2017, however, it acquired an option for a 100% interest in Irish company, Galway. This full ownership has now been attained after BTU Metals collected high-grade, multi-ounce samples.

Galway is a 160km2 property lying close to another project with indicated and inferred resources of 4.4 million ounces (Moz) of gold. BTU’s own exploration team has received assay results of samples collected on its recent field trip to Galway. The samples were processed at the laboratories of ALS Loughrea, itself in County Galway. High-grade samples and results were confirmed in two critical areas, Glenlusk and the escarpment area to its east.

The primary target area within Galway is, however, the Lee target. Here there is an exposed vein with historical grab samples ranging from 2.1g/t up to 66.4g/t gold – one high-grade sample hosted 247g/t gold and 0.85% lead – and an interpreted multi-vein structure based on ground and air geophysics.

The Galway Gold property is part of the Dalradian Supergroup meta-sediments and is situated 45km northwest of the city of Galway. It has been targeted for orogenic and low-sulphidation mineralisation based on a number of key features, including:

  • Its location within the Caledonian (Lower Paleozoic) orogenic zone, which offers favourable lithology for metal precipitation within the Dalradian meta-sediments
  • The fertile source rocks for gold, namely arc volcanics
  • Numerous large-scale fault zones, shears and cross-cutting faults, and
  • Known gold occurrences related to shear zones, as well as late cross-cutting fault structures, some of which are suggestive of near-surface boiling.

Two types of potential gold targets lie within the Galway area, being orogenic lode-gold – a subtype of the mesothermal lode-gold class – and epithermal gold. The former is characterised by cross-cutting quartz-carbonate ± sulphide veins, typically in shear zones, that formed by regional scale fluid flow due to orogenesis and the accompanying metamorphic dewatering. The epithermal deposits are near-surface gold-silver deposits almost exclusively associated with volcanic centres relating to arc volcanism.

Hannan Metals

Hannan Metals Limited exploration company is the 100% owner of the County Clare zinc-lead-silver-copper project, which comprises nine prospecting licences covering 35,444ha. The company has stated Ireland’s base-metal ore-field ranked first in the world in terms of zinc discovered per square kilometer, and second for lead.

Hannan Metals told Materials World permits for exploration activities are streamlined and contained within what it calls an administrative one-stop shop.

The licences included an historical exploration database with a significant number of regional soil sample results and approximately 140km of diamond drilling, which had defined a maiden indicated resource at Kilbricken of 2.6Mt at 8.8% zinc equivalent, as well as an inferred resource of 1.7Mt at 8.2% zinc equivalent. This is the company’s flagship project.

Continued drilling has shown a best drill hole zinc intersecting 8m at 4.1%, 33.7% lead and 174g/t silver. In addition, soil sampling has defined seven new anomalous areas within a 12km x 2km-long northwest trending, multi-element geochemical anomaly. Seismic data has revealed a critical new set of subsurface data across much of the Clare licence areas. Hannan Metals is now in the planning stage for a 20km diamond drilling programme designed to further increase the size of the Kilbricken resource. To achieve this, the company is drilling seismic targets 8km south of Kilbricken at Kilmurry on its major land package.

In geological terms, the property is underlain by Upper Devonian (sandstones) to Lower Carboniferous (sandstones and limestones) rocks. Hannan Metals notes that the stratigraphy appears simple, as the beds are what it calls the right way up and most major units are consistent in thickness across the property. Later structures, however, appear to complicate the geological framework.

Considering this, are there any difficult geological conditions in any sector of the company’s operations? Apparently so, as Michael Hudson said the Irish Carboniferous limestones are ‘variably abundant with ground water’.

The Lower Carboniferous sequence includes the Waulsortian limestone, which hosts most of Ireland’s important zinc-lead sulphide deposits. Two such Waulsortian-hosted zinc-lead deposits lie within Kilbricken and Milltown, a smaller prospect where exploration back in 1994 revealed 13.3m at 5.8% lead and 10.5% zinc from 45.4m in drill hole 3788/19.

Massive sulphide mineralisation at Kilbricken most commonly consists of early massive-textured, fine-grained pyrite, galena and sphalerite, cross-cut by coarse-grained sphalerite and galena, resembling sulphides found in the overlying veins. It differs from most other Irish zinc-lead prospects in that it is rich in silver, where the silver is generally associated with galena-rich zones.

Where are we now?

Irish mining is enjoying a period of success. Its high position within the FI survey underlines the global respect, which it has earned, and Hannan Metals was keen to inform Materials World of the ‘great pool of well-qualified and trained geologists in Ireland’.

Beyond extraction, there is also confidence in Ireland’s expertise in mine reclamation. Hudson said, ‘Galmoy is the only mine to have won a Green Apple Award [the International Green Apple Environmental Gold Award presented by The Green Organisation] for a mine closure, with the old tailings now a wetland that has attracted rare bird species back to their habitat.

‘The Irish are world leaders in 21st Century mine rehabilitation.’