Crustal-scale reflection seismic investigations in the Bathurst Mining Camp, New Brunswick, Canada

Abstract

The Bathurst Mining Camp, northern New Brunswick, Canada contains the super giant Brunswick No. 12 massive sulphide deposit and the smaller, now abandoned, Brunswick No. 6 deposit. Discoveries of additional base metal deposits in the camp require a better understanding of geological structures at depth. To this end, reflection seismic data in the Brunswick No. 6 area were acquired along three 2D profiles in 1999, with a total length of about 30 km. We have recovered, processed and interpreted these seismic data in conjunction with petrophysical and geological data from the study area. The seismic data and the borehole geophysical data allow a better understanding of both the shallow and deep structures (to 9 km depth) in the area. The seismic data show steeply dipping structures of the Brunswick No. 6 area, many of which reach the surface and allow for correlation with the surface and borehole geological information. Finite-difference modeling of major geological formations constrained with borehole petrophysical measurements indicates good correlation between the observed seismic and the synthetic data. A sequence of seismically reflective and transparent zones indicates a thrust stack in the Brunswick No. 6 area. The contact between the reflective and transparent zones is a series of faults bringing the two units over each other. A reflective package is observed in all three profiles and correlates well with the Brunswick horizon, the key mineralized zone in the study area. The Brunswick horizon extends down to depth greater than 3 km, increasing the hope for discovery of deeper base metal deposits. Two other sets of reflections are also observed in all three profiles in the depth range of about 5–8 km. We interpret them as two sets of thrusted sheets, which could be an indication that the Brunswick belt extends down to a maximum depth of 8 km.