Downhole-logging investigations including full-waveform sonic and laboratory density measurements were conducted 16 prior to this study suggesting iron-oxide deposits (magnetite and hematite) in the study area should seismically be detectable. Earlier reflection seismic studies 14, 15 targeting similar types of commodities (iron-oxide mineralization) in the region, Bergslagen mineral district of central Sweden, as the one in this study further encouraged us to take this initiative. The choice of the streamer was justified in this study due to the road accessibility, and the possibility of high-voltage power cables, railroad and noise contamination if the conventional geophone-type sensors were used instead 13. Seismic landstreamers are not new and have been used since the 80s for mainly urban or in general near-surface (>100 m) applications 5, 6, 7, 8, 9, 10, 11, 12. Within an on-going project involving petrophysical, geological and geophysical studies, we have examined the potential of a newly developed, for urban environment, MEMS-based seismic landstreamer 3 for cost-effective mine planning and mineral exploration at two sites in Finland 4 and Sweden (this study, Fig. Decrease in receiver cost and higher quality sensors have allowed some contributions but on the source side this is still an issue. There is therefore a high demand in reducing this cost in order the method to be established in the mineral exploration sector similar to a variety of other geophysical methods. While seismic methods have considerably better resolution and penetration depths than other geophysical methods, the high acquisition and processing cost poses a constraint in using them routinely for mineral exploration purposes. Therefore, at the presence of favourable geometry, size and signal-to-noise ratio, they should be detectable using seismic methods. This is encouraging and suggests such a cost-effective exploration method can be used in the area and elsewhere to delineate similar depth range iron-oxide deposits.Įconomic metallic deposits have usually strong seismic contrast 1, 2, product of velocity and density, with their host rocks. Reflection data processing results clearly image the mineralization as a set of strong high-amplitude reflections and likely slightly extending beyond the known 850 m depth. Within 4 days, approximately 3.5 km of seismic data using 2–10 m source and receiver spacing were acquired. A Bobcat-mounted drophammer, 500 kg, was used to generate the seismic signal. Combined streamer (100-3C-MEMS (micro-electromechanical system), 2–4 m spacing) and 75 wireless recorders (mixed 10 Hz and MEMS, 10 m spacing) were used. Here, we present a pilot study examining the potential of the streamer for deep targeting a known, down to approximately 850 m depth, iron-oxide mineralization in the Bergslagen mineral district of central Sweden. Since 2013 and through a number of case studies, we have been testing a newly developed for urban environment, digital-based 240 m long, seismic landstreamer for mine planning and mineral exploration purposes. To be fully embraced into mineral exploration, seismic data require to be acquired fast, cheaper and with minimum environmental impacts addressing also the often brown-field highly noisy environment where these surveys are employed.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |