Pallas Green Geology 2007

  1. Pallas Green Geology Pt 1
  2. Pallas Green Geology Pt 2

 

Pallas Green Project, Ireland (23.6% owned)

Minco's strategy has been to develop the Pallas Green project in Co. Limerick, which is a joint venture with Xstrata Zinc (23.6%|76.4%), covering exploration licences totaling 294 square kilometres located on the southern boundary of the Irish Midland orefield between Limerick and Tipperary. The project is the focus of an intensive exploration drilling programme of a potentially world-class zinc-lead deposit and probably the largest such drill programme in the 50-year history of the Irish mining industry.

Ireland is an established regional zinc producer supplying around half of Europe's mine production. In its 2010 Half Yearly Results, issued on August 4 2010, Xstrata, referring to the Caherconlish Cluster, commented that "recent discoveries continue to show encouraging signs of a potential world-class resource."

The Stonepark North and Stonepark deposits of Connemara Mining-Teck joint venture to the west are believed to form part of a single, six kilometer by four kilometer, system of zinc-lead mineralisation.

In February 2011, Xstrata provided Minco with a revised JORC resource estimate, calculated as of 31 December 2010, at both a 6% cut-off and a 4% cut-off. The 4% zinc equivalent cut-off resource amounts to 25.9 million tonnes of inferred resources at an average grade of 7.51% zinc and 1.38% lead (8.89% zinc equivalent), while the 6% zinc equivalent cut-off resource amounts to 17.6 million tonnes of inferred resources at an average grade of 8.96% zinc and 1.72% lead (10.68% zinc equivalent). The Caherconlish area mineralised zones which form the inferred resource estimate comprise 8 to 10 distinct pods or lenses of higher grade mineralisation within a surrounding lower grade mineralised envelope. The resource tonnage of the individual pods varies between 0.8 million to 8.9 million tonnes.

In June 2011, Xstrata provided Minco with an updated non JORC compliant resource estimate (as of 31 April 2011). The 4% zinc equivalent cut-off resource amounts to 27.8 million tonnes of inferred resource category at an average grade of 7.4% zinc and 1.34% lead (8.73% zinc+lead), while the 6% zinc equivalent cut-off resource amounts to 19.0 million tonnes of inferred resource category at an average grade of 8.73% zinc and 1.6% lead (10.33% zinc+lead).

Irish Zinc-Lead Deposits
Deposit Mt Zn% Pb% Zn+Pb% Status
Navan 100.8 7.97 1.94 9.91 operating
Caherconlish 27.8 7.40 1.34 8.73 partially explored
Lisheen 22.6 11.92 2.03 13.95 operating
Silvermines 14.5 6.80 2.80 9.60 past mine
Tynagh 9.2 5.00 6.20 11.20 past mine
Galmoy 8.6 12.36 2.84 15.20 in salvage
Ballinalack 5.7 6.80 1.10 7.90 prospect
Harbeton Bridge 3.9 8.10 1.20 9.30 prospect
Tatestown 3.6 5.30 1.50 6.80 prospect
Keel 1.9 7.70 1.00 8.70 prospect

Caherconlish Area Deposits

The Caherconlish cluster remains open in all directions with encouraging results coming from exploration drilling currently ongoing between Knockroe and Tobermalug, Knockroe and Stonepark and to the south where 2529-78, 1.1 kilometres to the south of the current Tobermalug resource intersected 8.8m averaging 8.19% zinc and 1.79% lead and 2529-107, an 500m step-out south of Knockroe, intersected 4.3m averaging 4.03% zinc and 0.61% lead.

The Caherconlish cluster is comparable to the mineralised clusters currently supporting the Lisheen and Galmoy mining operations, respectively 55 and 60 kilometres to the northeast. Assuming that Tobermalug represents the eastern side and Stonepark the western side of the Caherconlish system, then it extends over an area of approximately twenty five square kilometres. In contrast the Lisheen system covers an area of approximately five square kilometres. The upside potential at Caherconlish remains high and considerably more exploration is required.

The Caherconlish and Lisheen Clusters
The Caherconlish and Lisheen Clusters (Drawn to same scale)

Typically, the major carbonate hosted Irish deposits, such as the Caherconlish cluster, are bounded to the south by major, northeast striking faults adjacent to which are located the highest grade and thickest sections of mineralisation.

North-South Section Through Tobermalug
North-South Section Through Tobermalug

At Lisheen these high grade lenses are small compared to the overall area of the deposit but, because of the higher average and thickness of these lenses, contain a high percentage of the contained metal, significantly impacting average resource grade. At Lisheen the Bog Zone was scheduled to supply 43 percent of the total metal produced between 2007 and 2011 (Hopperstead, 2008. 12th US/North American American Mine Ventilation Symposium).

Schematic North-South Section Through Lisheen
Schematic North-South Section Through Lisheen

The boundary fault zone has yet to be intersected in drilling to the south of the Caherconlish cluster but has been established through geological mapping to the northeast. The potential to significantly increase both the tonnage and average grade of the deposit is considered high. By analogy with Lisheen, lenses of thick, high grade mineralisation (20 percent plus zinc) can be anticipated in the immediate hanging wall of the boundary fault and the current 24.1Mt resource would represent just the northern, low grade part of a much larger system which overall could have an average grade similar to that of Lisheen.

Lisheen-type mineralisation is hosted by breccia systems developed within the Waulsortian reef, primarily the basal part of this unit. Unlike Lisheen, the thicknesses and distribution of the host breccias are not limiting factors to ore development within the Caherconlish area. Breccia development is almost ubiquitous within the area and breccia thicknesses are commonly in excess of 50m; and often mineralised, albeit intermittently and at low grade, throughout. For this reason, ore thicknesses of 50m or more within any high grade lenses associated with the boundary fault would not be surprising.

The Pallas Green Alteration Trend
The Caherconlish cluster is developed within the western part of the Pallas Green Alteration Trend. Approximately 70 percent of the alteration trend remains either unexplored or partially explored. The Pallas Green block of prospecting licences contains a west northwest trending alteration zone, the Pallas Green alteration trend, approximately 25 kilometres in length and 2 kilometres in width. This is considered analogous to the Lisheen alteration trend (approximately 20 kilometres in length and 2 kilometres in width) which hosts the Lisheen and Galmoy Mines, respectively 55 and 60 kilometres northeast of the Pallas Green area. The Caherconlish cluster is developed within the western part of the alteration trend.

Alteration Trends

The presence of widespread zinc-lead mineralisation has been established throughout those parts of the alteration trend explored by drilling and three small mineralised deposits have been discovered within the eastern part of the alteration trend.

Pallas Alteration Trend
Alteration Trend around Caherconlish

Approximately 70 percent of the alteration trend remains either unexplored or partially explored and expectations of further discoveries beyond the limits of the Caherconlish cluster remain high, with specific target areas identified where the northeast striking Dromkeen and Connagh Faults intersect with the Pallas Green Alteration Trend.