The Antamina Cu-Zn mine which lies in the high Andes of Peru, 270km north of Lima, is operated by Compañía Minera Antamina S.A., for a consortium of owners including BHP Billiton, Xstrata, Teck Resources, and Mitsubishi Ltd. An expansion of the mine has been recently approved which takes advantage of a 75% increase in reserves; the current extraction rate of 94,000 tonnes/day will be increased by 38% by 2012, with a corresponding extension of the mine life to 2029. With a rapidly expanding open pit in mountainous terrain, it is imperative to have a good understanding of the structural and lithological architecture, to ensure continuing safe and profitable extraction of the orebody.
Since 2004, SRK has been involved in producing and updating a 3D model of the major structures in the vicinity of the open pit. The current model comprises 60 structures in 6 suites of faults, characterised by their initiation and development history, continuity and geotechnical characteristics. A 3D LeapfrogTM geological model produced from drillhole data shows the distribution of the major rock types encountered during pit development, including intrusive rocks, endoskarn and exoskarn, hornfels, marble and limestone, as illustrated and explained below.
The combined structural and lithological models have been used for a variety of purposes, including geological and geotechnical evaluations and hydrogeological studies. As development of the mine proceeds, updated information will continually be used to revise and refine the structural geological model.
