Development of tomographic systems for mining, mineral exploration and environmental purposes

A research project was carried out to develop and test a prototype seismic tomographic system suitable for use in the exploration, mining and civil en gineering industries. Tomographic techniques are attractive because they ca n provide information from the unknown areas between drill-holes and are no n-destructive, which is particularly important for civil engineering and ra dioactive waste disposal projects. The starting point was the SEAMEX-Compact seismic system, developed in 1991 for use in the coal industry, which had limited capabilities. Prototype de velopment involved the redesign of existing seismic systems, development an d assembly of compact units and production of new acquisition and control s oftware. Emphasis was placed on high dynamic range and control mechanisms. The prototype system was named SUMMIT-Compact and the final version is much advanced from the SEAMEX system. The prototype was calibrated and tested a t two Ruhrkohle AG sites in Germany, the Reocin zinc-lead mine in Spain, a nearby Reocin exploration area and the Grimsel rock laboratory for radioact ive waste disposal in Switzerland. Work at Reocin mine and in the explorati on area was supported by studies of matrix porosity, fluid inclusions and i sotopes to model the zinc-lead sulphide orebodies. The seismic tomographic technique proved highly successful for short-hole surveys in the Reocin min e and at the Grimsel rock underground laboratory. These surveys demonstrate d clearly the effectiveness of seismic tomography in holes drilled both fro m the surface and underground, and in wet or dry conditions. The technique can be used immediately for surveys of the type required by many civil engi neering projects, for underground radioactive waste-disposal projects and t o address specific mining problems. Exploration area testwork, carried out in deep drillholes, gave poor result s because the open joints and cavities in the karstified dolomites reduced the strength of the seismic transmissions. The seismic equipment operated w ell and the results might well have been good if the rocks had been less af fected by deep weathering. The technique has considerable potential for use in deep-hole mineral exploration in suitable geological environments such as the Scandinavian Shield and the Spanish-Portuguese Pyrite Belt. The prototype SUMMIT-Compact system is the most advanced of its type in the world and the field tests demonstrated the effectiveness of seismic tomogr aphic techniques in small-scale surveys of the type required for many indus trial applications. Mineral exploration is a large market waiting to be dev eloped, but tomography is in its infancy in this field and the technique ha s yet to be proved effective in deep drill-holes. The prototype system is b eing modified and manufactured for marketing worldwide. Further research is warranted to refine the resolution and penetration of the system and addit ional research is urgently required to test the seismic tomographic techniq ue in deep holes in a variety of suitable geological environments. The project was coordinated by Asturiana de Zinc S.A. (Spain) and the partn ers were Deutsche Montan Technologie GmbH (Germany), Escuela Tecnica Superi or de Ingenieros de Minas de Madrid (Spain) and the British Geological Surv ey.