Abstract
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. 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. 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. 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. A Bobcat-mounted drophammer, 500 kg, was used to generate the seismic signal. Within 4 days, approximately 3.5 km of seismic data using 2–10 m source and receiver spacing were acquired. 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. 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.
Highlights
Economic metallic deposits have usually strong seismic contrast[1, 2], product of velocity and density, with their host rocks
The most striking feature in the section is a set of high-amplitude reflections associated with the known mineralization
It is so noticeable and bright-spot looking that it cannot be anything than from the mineralization; it is consistent with the logging data (Fig. 2) suggesting their high acoustic impedance contrast with their host rocks
Summary
Since 2015, we have downhole logged six boreholes (Fig. 1, BB12004, BB14001, BB14002, BB14004, BB14005 and BB14008) using full-waveform triple sonic, natural gamma, magnetic susceptibility, formation resistivity, fluid conductivity and temperature. Density measurements were conducted on core samples at every 1–3 m allowing studying seismic response of the mineralization using synthetic 1D seismograms. Maries et al.[16] detail the physical property studies and how the results can be correlated with RQD and other types of measurements
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