Chapter 16: Discovery of the Tara Deep Zn-Pb Mineralization at the Boliden Tara Mine, Navan, Ireland: Success with Modern Seismic Surveys.
John H. Ashton, Alastair Beach, Robert J. Blakeman, David Coller, Paul Henry, Rowan Lee, Murray Hitzman, Charles Hope, Simon Huleatt-James, Brendan O’Donovan, Michael E. Philcox, 2018. "Discovery of the Tara Deep Zn-Pb Mineralization at the Boliden Tara Mine, Navan, Ireland: Success with Modern Seismic Surveys.", Metals, Minerals, and Society, Antonio M. Arribas R., Jeffrey L. Mauk
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In the first decade of the 21st century, surface exploration drilling around the Boliden Tara mine at Navan, Ireland, aimed at ~1-km-deep targets, was becoming ineffective. During 2010, the extensive geologic knowledge of the existing Navan orebody was leveraged in an Experts Meeting to promote near-mine discovery. Two ideas, of many, were of relevance to this paper: (1) undiscovered mineralized fault-related zones were predicted south of the orebody, and (2) seismic surveys could locate subsurface faults. By late 2012, seven 2D seismic lines (totaling 101 km) had been acquired, processed, and initially interpreted. Pre-stack time migration images were used for interpretation, augmented by diamond drill core data where available. The seismic imaging proved a “game changer” in terms of subsurface visualization and a priority target was identified 2 km south of the mine on the footwall crest of a large south-dipping basin-margin fault. The first hole intersected 34 m of mineralized rock with 14% Zn + Pb, but at greater depth than anticipated. Follow-up drilling was initially successful but proved to be challenging. The first hole intersected a deep structurally complex section of the newly discovered zone that required more drilling to establish its location and attitude. Further drilling, utilizing extensive navigational deflection technology, outlined a mineralized zone similar in nature to the Navan 5 Lens at depths of 1 to 2 km. Inferred resources through 2016 were estimated at 10.2 Mt grading 8.5% Zn and 1.8% Pb. Underground exploration development of this zone commenced in April 2017, and will allow accurate delineation of this significant discovery.