The Lead lenses are believed to have formed at the top of the original ore system as shown in Figure 8.2, but have been folded into their current position.
8.2 North Mine
Mining at the North Mine was completed in 1993 after producing an estimated 34 million tonnes, mainly from the underground operation and 0.7 million tonnes from surface mining. Underground mining recommenced at the North Mine in March 2003. Little has been published on the mine geology of the North Mine since the 1950’s. The mineralization at the North Mine consisted of the high-grade lead 2 and 3 Lens and one minor Zinc Lode. The lenses are associated with a welldeveloped pale, creamy, pink garnet-quartz rock. Between the two lenses, extensive silicification and sulfide remobilization formed large zones of siliceous blue-quartz lode with minable grades. The current configuration of the North Mie lenses is shown in Figure 8.3.