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Open AccessArticle

Underground Vertical Seismic Profiling with Conventional and Fiber-Optic Systems for Exploration in the Kylylahti Polymetallic Mine, Eastern Finland

1
Department of Geosciences and Geography, University of Helsinki, PL 68, 00014 Helsinki, Finland
2
Vibrometric Oy, Taipaleentie 127, 01860 Perttula, Finland
3
Boliden Finnex Oy, Polvijärventie 22, 83700 Polvijärvi, Finland
4
Institute of Geophysics, Polish Academy of Sciences, Ksieçia Janusza 64, 01452 Warszawa, Poland
*
Authors to whom correspondence should be addressed.
Minerals 2018, 8(11), 538; https://doi.org/10.3390/min8110538
Received: 28 September 2018 / Revised: 27 October 2018 / Accepted: 13 November 2018 / Published: 20 November 2018
(This article belongs to the Special Issue Seismic Methods in Mineral Exploration)
Seismic reflection methods have been used for the exploration of mineral resources for several decades. However, despite their unmatched spatial resolution and depth penetration, they only have played a minor role in mineral discoveries so far. Instead, mining and exploration companies have traditionally focused more on the use of potential field, electric and electromagnetic methods. In this context, we present a case study of an underground Vertical Seismic Profiling (VSP) experiment, which was designed to image a (semi-)massive sulfide deposit located in the Kylylahti polymetallic mine in eastern Finland. For the measurement, we used a conventional VSP with three-component geophones and a novel fiber-optic Distributed Acoustic Sensing (DAS) system. Both systems were deployed in boreholes located nearby the target sulfide deposit, and used in combination with an active seismic source that was fired from within the underground tunnels. With this setup, we successfully recorded seismic reflections from the deposit and its nearby geological contrasts. The recording systems provided data with a good signal-to-noise ratio and high spatial resolution. In addition to the measurements, we generated a realistic synthetic dataset based on a detailed geological model derived from extensive drilling data and petrophysical laboratory analysis. Specific processing and imaging of the acquired and synthetic datasets yielded high-resolution reflectivity images. Joint analysis of these images and cross-validation with lithological logging data from 135 nearby boreholes led to successful interpretation of key geological contacts including the target sulfide mineralization. In conclusion, our experiment demonstrates the value of in-mine VSP measurements for detailed resource delineation in a complex geological setting. In particular, we emphasize the potential benefit of using fiber-optic DAS systems, which provide reflection data at sufficient quality with less logistical effort and a higher acquisition rate. This amounts to a lower total acquisition cost, which makes DAS a valuable tool for future mineral exploration activities. View Full-Text
Keywords: mineral exploration; reflection seismic imaging; hardrock seismics; vertical seismic profiling; distributed acoustic sensing mineral exploration; reflection seismic imaging; hardrock seismics; vertical seismic profiling; distributed acoustic sensing
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MDPI and ACS Style

Riedel, M.; Cosma, C.; Enescu, N.; Koivisto, E.; Komminaho, K.; Vaittinen, K.; Malinowski, M. Underground Vertical Seismic Profiling with Conventional and Fiber-Optic Systems for Exploration in the Kylylahti Polymetallic Mine, Eastern Finland. Minerals 2018, 8, 538.

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