SEISMIC-REFLECTION TECHNIQUES FOR BASE-METAL EXPLORATION IN EASTERN CANADA - EXAMPLES FROM BUCHANS, NEWFOUNDLAND

In 1989, as part of the Lithoprobe East program, high-resolution 60-fold seismic reflection profiles were recorded using Vibroseis sources in the vicinity of the Buchans mine. The area is considered to be a fold and thrust belt in which the massive sulphide-barite orebodies occurring within volcanic and sedimentary units of the Buchans Group are repeated in a large number of thrust systems. The main objective was to image the individual faults, generally narrow zones of brittle shear, some of which have been intruded by diabase sills. In 1991, Memorial University of Newfoundland recorded a 24-fold line using explosives as sources, coincident with one of the Lithoprobe lines, in order to compare the resolution of shallow structures of economic importance with that obtained using Vibroseis. The explosive sources provided reflections richer in high frequencies than the Vibroseis sources for depths less than 1 km. The resolution of the reflections is greatly improved by two processes: (1) the application of refraction static corrections, and (2) spectral balancing of the NMO-corrected CMP gathers over two octaves prior to stacking. Compared with Vibroseis, the approach using small explosive sources is considered preferable for future work in mineral exploration and mine development because of lower costs and better resolution of shallow moderately-dipping faults.