Seismic approaches for structural studies of the Sudbury basin

Abstract

This study investigates the feasibility of applying seismic techniques in the search for ore deposits, with particular emphasis given to locating orebodies at great depths. The basic procedure followed was essentially an understanding of the forward problem, whereby the effects of the subsurface structure in a typical mining district were thoroughly studied. The initial stage of the study was devoted to determining the elastic parameters by laboratory measurement of seismic velocities and densities of core samples obtained from the Sudbury basin, Canada. By virtue of its ability to handle lateral as well as vertical inhomogeneities, fast computing time and flexibility, the asymptotic ray theory was judged to be more suitable for studying the effect of geologic structures typically found in the Sudbury basin. Both large-scale and small-scale models, representing actual geologic conditions in Sudbury, were constructed. The computed seismic response of the large-scale models shows that the micropegmatite/oxide-rich quartz gabbro and the mafic norite/granite gneiss contacts are characterized by substantially strong reflections, indicating that these two interfaces can serve as marker horizons in future seismic surveys. In the small-scale models of mineralized structures, the sulfide body was outlined by a distinctly high amplitude.of reflection. Both the traveltime and the dynamic characteristics of these models have features that are indicative of the presence of mineralized structures.