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High-resolution 2D seismic imaging and forward modeling of a polymetallic sulfide deposit at Garpenberg, central Sweden
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
Boliden Mines.
2013 (English)In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 78, no 6, B339-B350 p.Article in journal (Refereed) Published
Abstract [en]

We acquired a high-resolution 2D seismic profile to test the capability of the seismic method in imaging a sulfide ore body at Garpenberg, central Sweden. Delineation of the geologic structures, which surround and host the ore body, is another goal of the survey. Due to the 3D geology of the structures, a cross-dip correction performed to image out-of-the-plane reflections, resulting in a clear high amplitude anomaly at a time and location to that to be expected from near the top of the ore body. Furthermore, DMO processing and migration are applied to the data, providing images of four main reflection groups. The reflections have been interpreted as corresponding to geologic rock units in the area that partly interfere with the potential ore body signal. To further investigate the seismic response of the ore body, forward modeling by ray-tracing is applied using the ore body geometry as mapped by drilling. We use two ray-tracing approaches: standard 3D ray-tracing and an exploding reflector approach. Seven representative samples from the mine area are used to determine P-wave velocities. The measurements show a considerable contrast between the ore body and host rock. By comparing the modeled and observed data, we find that the high amplitude signal in the real seismic section most likely emanates from near the top of one concentrated ore which lies inside the larger mapped ore body that has been modeled as a resource. The base of the ore body is only observed on the synthetic data whereas a signal penetration analysis suggests that the seismic signal penetrated efficiently along the entire survey line. Presence of disseminated ore and lower fold toward the northern end of the profile could be combined reasons that make imaging the base of the ore body difficult.

Place, publisher, year, edition, pages
2013. Vol. 78, no 6, B339-B350 p.
Keyword [en]
2D, processing, ray tracing, modeling
National Category
Geophysics
Identifiers
URN: urn:nbn:se:uu:diva-210135DOI: 10.1190/geo2013-0098.1ISI: 000330223800003OAI: oai:DiVA.org:uu-210135DiVA: diva2:661281
Available from: 2013-11-01 Created: 2013-11-01 Last updated: 2017-12-06
In thesis
1. Application of the Seismic Reflection Method in Mineral Exploration and Crustal Imaging: Contributions to Hardrock Seismic Imaging
Open this publication in new window or tab >>Application of the Seismic Reflection Method in Mineral Exploration and Crustal Imaging: Contributions to Hardrock Seismic Imaging
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The seismic reflection method has been used extensively in mineral exploration and for imaging crustal structures within hardrock environments. In this research the seismic reflection method has been used and studied to address problems associated with hardrock settings. Papers I and II, address delineating and imaging a sulfide ore body and its surrounding rocks and structures in Garpenberg, central Sweden, at an active mine. 3D ray-tracing and finite-difference modeling were performed and the results suggest that although the detection of the ore body by the seismic reflection method is possible in the area, the presence of backfilled stopes in the mine makes seismic imaging of it difficult. In paper III the deeper structures of the Pärvie fault system in northern Sweden were revealed down to about 8 km through 2D seismic reflection profiling. The resulting images were interpreted using microearthquake data as a constraint. Based on the interpretation, some locations were suggested for future scientific deep drilling into the fault system. In paper IV, the seismic signature of complex geological structures of the Cue-Weld Range area in Western Australia was studied using a portion of a deep 2D seismic reflection profile. The pronounced reflections on the seismic images were correlated to their corresponding rock units on an available surface geological map of the study area. 3D constant velocity ray-tracing was performed to constrain the interpretation. Furthermore, the proposed structural model was tested using a 2D acoustic finite-difference seismic modeling method. Based on this study, a new 3D structural model was proposed for the subsurface of the area. These studies have investigated the capability of the seismic reflection method for imaging crustal structures within challenging hardrock and complex geological settings and show some its potential, but also its limitations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 76 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1269
Keyword
Seismic reflection, Hardrock, Mineral exploration, Crustal imaging, Interpretation, Modeling
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-259396 (URN)978-91-554-9290-8 (ISBN)
Public defence
2015-09-25, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2015-08-26 Created: 2015-08-02 Last updated: 2015-10-01

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Ahmadi, OmidJuhlin, ChristopherMalehmir, Alireza

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