The orebody was discovered in 1970 by Tara Prospecting, 2km northwest of the town of Navan (Fig. 1; OBrien and Romer, 1971). Shallow soil geochemical surveys displaying peak anomaly values of 5000ppm Zn and 2000ppm Pb were followed by the discovery of mineralized boulders and minor sulfides in a small outcrop. Induced polarization surveys generated strong anomalies and follow-up diamond drilling immediately intersected ore. Initial reserves amounted to 69.9Mt grading, 10.1% Zn and 2.6% Pb. Due to actions of third parties, ore north of the River Blackwater became unavailable to Tara leaving some 60.9Mt grading, 10.1% Zn and 2.7% Pb available for mining. Production commenced in 1977 and up to the end of 1993 amounted to some 36Mt. At the end of 1993 total reserves amounted to 41.8Mt grading 8.04% Zn and 2.68 % Pb. Currently Outokumpu Zinc - Tara Mines Ltd, produces some 2.6Mt of ore per annum grading 8.0% Zn and 2.0% Pb, from an underground, highly mechanized, trackless operation employing blast-hole open stoping as the principal mining method (Libby et al, 1985). The Tara mine, since its inception, has maintained a major emphasis on environmental monitoring. This has involved minimization of noise, blasting vibrations, dust and trace element emissions as well as close control of the visual impact of the Navan operation
Figures & Tables
Irish Carbonate-Hosted Zn-Pb Deposits
This paper describes the stratigraphy, basin evolution, and structural geology of Ireland so that the hydrothermal processes which formed the deposits can be placed in a geological context. Informal regional nomenclature are used throughout this paper to provide a clearer overview, rather than the myriad of existing local formation names (see Jones and Earls, this volume). The stratigraphy, together with series and stage designation and available radiometric ages, is presented in Figure 1.