Basemetals

Northern Ireland is one of the most prospective areas of the United Kingdom for base metal mineralisation. Historical production of lead has resulted in numerous small adits and shafts across parts of Counties Down, Armagh and Tyrone. Modern exploration commenced in the late 1960s, following the introduction of the Mineral Development Act (Northern Ireland) 1969 and continues to the present day. At present three main areas are considered to have the highest prospectivity for base metal deposits. However, as further data are collected and new models developed other areas may become targets.

The Sperrins

The Sperrin Mountains have the potential to host economic base metal deposits. The Glenlark prospect, 3km from the Curraghinalt gold deposit, is believed to represent a stratabound mineralisation system (Zn-Pb-Au-Ag). Surveys over areas underlain by Neoproterozoic Dalradian rocks (c. 590Ma) have highlighted targets which merit follow-up investigation. Bedrock base metal sulphide mineralisation has been discovered throughout the region.

The base metals of copper, lead and zinc are important for today’s technologically driven society. Transport systems rely on these metals for the production of cars, aeroplanes and ships and the communications industry would never have reached its current level without the use of these metals in telephones, televisions, computers, satellites and cables.

Tyrone Igneous Complex

The Tyrone Igneous Complex to the southeast of the Sperrins comprises the Tyrone Volcanic Group (TVG) and the Tyrone Plutonic Group. The volcanic, volcaniclastic and thin sedimentary rocks of the TVG are characteristic of an Island Arc setting making it highly prospective for Volcanogenic Massive Sulphide-style deposits. Porphyry-style mineralisation associated with acid intrusive bodies has been identified at Cashel Rock. Geologically this area represents the eastern extension of the ‘palaeo’ island arc that hosts the Buchans deposits in Newfoundland.

The Northwest Irish Carboniferous Basin

The Lower Carboniferous lithologies of Counties Fermanagh and Tyrone are considered prospective for carbonate hosted Zn-Pb-Ag deposits. Exploration in the 1970s identified sub-economic concentrations of base metal sulphides and as a result of the GSNI geochemical surveys, part of the Clogher Valley was highlighted as an area with enhanced prospectivity. Outcrops of Waulsortian stratigraphy (host to the majority of deposits in the Republic of Ireland) remain to be fully evaluated.

Other Areas

The Dalradian inlier of northeast Co. Antrim exposes similar rocks to those found in the Sperrins and may represent a target for base metal mineralisation. Drilling through the Palaeocene Antrim Lava Group also identified mineralised Dalradian bedrock at shallow depths.

At Ballymoney, native copper was drilled in the basalt below the lignite deposit. The prospectivity of the Antrim Lava Group for copper and nickel remains largely unknown.

A number of anomalous areas have been highlighted in south Co. Armagh which are not believed to be related to the historical workings. A belt of anomalous Zn values in soil extends from the area of known gold mineralisation at Keady to the southeastern part of Co. Down. This anomalous zone occurs within the Lower Palaeozoic sedimentary rocks.