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Dehghannejad, Mahdieh
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Publications (10 of 19) Show all publications
Dehghannejad, M., Malehmir, A., Svensson, M., Linden, M. & Möller, H. (2017). High-resolution reflection seismic imaging for the planning of a double-train-track tunnel in the city of Varberg, southwest Sweden. Near Surface Geophysics, 15(3), 226-240
Open this publication in new window or tab >>High-resolution reflection seismic imaging for the planning of a double-train-track tunnel in the city of Varberg, southwest Sweden
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2017 (English)In: Near Surface Geophysics, ISSN 1569-4445, E-ISSN 1873-0604, Vol. 15, no 3, p. 226-240Article in journal (Refereed) Published
Abstract [en]

A newly developed broadband digital-based seismic landstreamer system was employed for the planning of a double-train-track tunnel in the city of Varberg, southwest Sweden. Twenty-five seismic profiles, totalling more than 7.5 km of data, were acquired using a 2-to 4-m receiver and source spacing. At places where it was not possible to move the streamer such as road crossings, wireless recorders connected to 28-Hz geophones were used. In addition to the earlier refraction data analysis and first-break traveltime tomographic modelling, reflection processing of the data was considered in this study, given the realisation of reflections in raw shot gathers and their good quality. Bedrock is strongly reflective in most cases but is not evident in the sections when it gets near the surface. Bedrock undulation is noticeable in most reflection sections, and at one occasion, strong diffraction is observed in the bedrock or near to it. The diffraction is originated, not known during the survey, from a 400-m3 cylindrical (of about 3-m-height and 13-m-diameter) concrete-made fire-protection water tank situated in the bedrock and used in emergency situations. Reflection seismic data greatly complement the tomographic models and support deep bedrock where the excavation of the tunnel is planned in downtown Varberg. This interpretation implies different reinforcements and tunnel construction methods (e.g., roofed concrete) at this section of the tunnel. In addition, weakness zones associated with fracture systems are inferred from the reflection characteristics and in conjunction with the velocity models requiring verification by additional boreholes.

Place, publisher, year, edition, pages
EUROPEAN ASSOC GEOSCIENTISTS & ENGINEERS, 2017
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-334502 (URN)10.3997/1873-0604.2017011 (DOI)000408581700002 ()
Available from: 2018-01-10 Created: 2018-01-10 Last updated: 2018-06-04Bibliographically approved
Malehmir, A., Heinonen, S., Dehghannejad, M., Heino, P., Maries, G., Karell, F., . . . Salo, A. (2017). Landstreamer seismics and physical property measurements in the Siilinjarvi open-pit apatite (phosphate) mine, central Finland. Geophysics, 82(2), B29-B48
Open this publication in new window or tab >>Landstreamer seismics and physical property measurements in the Siilinjarvi open-pit apatite (phosphate) mine, central Finland
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2017 (English)In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 82, no 2, p. B29-B48Article in journal (Refereed) Published
Abstract [en]

We tested the applicability of a newly developed broadband (0-800 Hz) digital-based seismic landstreamer for open-pit mine planning in the apatite-bearing Siilinjarvi mine in central Finland. Four seismic profiles, in total approximately 2.5 km long (2-4 m source and landstreamer receiver spacing), two inside the pit and two on its margins, were acquired in combination with wireless recorders connected to 10 Hz geophones and fixed at every 10 m spacing along the seismic profiles while the streamer data were being acquired. Downhole logging and laboratory physical property measurements on core and rock samples were carried out to not only support the seismic interpretations but also to provide information about the possible geophysical signature of these unique types of deposits. In spite of a highly noisy mining environment, seismic data of high quality were acquired; however, reflection processing and interpretations were challenged by the geologic complexities of several generations of basic and carbonatite dikes. To complement the reflection data imaging and to account for the steep elevation changes and crookedness of some of the seismic profiles, 3D first-arrival traveltime tomography and 3D swath reflection imaging were also carried out. Clear refracted arrivals from the open-pit profiles suggest the possibility of low-velocity zones associated with either blasting or several shear zones intersecting the seismic profiles. In terms of reflectivity, reflections have a different appearance from short and flat to longer and steep ones. The downhole-and borehole logging data suggest that some of these reflections are associated with diabase dikes and some are likely from zones of weaknesses in the alkaline- carbonatite complex. We determine the potential of using seismic streamers for cost-and time-effective open-pit mine planning and encourage further testing in simpler geologic settings to be established.

Place, publisher, year, edition, pages
SOC EXPLORATION GEOPHYSICISTS, 2017
National Category
Geophysics Geochemistry
Identifiers
urn:nbn:se:uu:diva-320272 (URN)10.1190/GEO2016-0443.1 (DOI)000396852200003 ()
Funder
VINNOVA, 2014-06238Swedish Research Council Formas, 25220121907
Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2017-04-18Bibliographically approved
Malehmir, A., Brodie, B., Dehghannejad, M., Juhlin, C. & Lundberg, E. (2016). A state-of-the-art MEMs-based 3C Seismic Landstreamer for Various Near-surface Applications. In: : . Paper presented at 78th EAGE Conference and Exhibition 2016, 30 May - 2 June, 2016, Vienna, Austria.
Open this publication in new window or tab >>A state-of-the-art MEMs-based 3C Seismic Landstreamer for Various Near-surface Applications
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2016 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Within a large academia-industry consortium we have developed a unique state-of-the-art consisting of 100-3C MEMs-based sensors seismic landstreamer for various near surface applications and particularly for urban underground infrastructure planning projects. The streamer has been tested and evaluated in several places against plant-type geophones and the same type MEMs sensors but planted and for the planning of several major tunnelling projects inside and outside Sweden. When compared to plant-type geophones in a highly electrical noisy environment, the streamer sensors illustrated their potentials in being uncontaminated and superior to its predecessor geophone-based streamers. Being GPS-time stamped and sampled, it allows the streamer data to be merged with wireless data operating in a passive mode further overcoming some of the challenges encountered in complex urban and geological environments. Here, we present the streamer and its characteristics and examples of data and results obtained from it. In particular, we present results from a survey comprising of 25 profiles of about 7.5 km long in total and a surface-tunnel experiment where the streamer data were crucial to recognize mode-converted signals from fracture systems intersected in the tunnel.

National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-294451 (URN)10.3997/2214-4609.201601638 (DOI)
Conference
78th EAGE Conference and Exhibition 2016, 30 May - 2 June, 2016, Vienna, Austria
Available from: 2016-05-21 Created: 2016-05-21 Last updated: 2017-01-25Bibliographically approved
Tavakoli, S., Dehghannejad, M., Garcia Juanatey, M. d., Bauer, T. E., Weihed, P. & Elming, S.-Å. (2016). Potential Field, Geoelectrical and Reflection Seismic Investigations for Massive Sulphide Exploration in the Skellefte Mining District, Northern Sweden. Acta Geophysica, 64(6), 2171-2199
Open this publication in new window or tab >>Potential Field, Geoelectrical and Reflection Seismic Investigations for Massive Sulphide Exploration in the Skellefte Mining District, Northern Sweden
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2016 (English)In: Acta Geophysica, ISSN 1895-6572, E-ISSN 1895-7455, Vol. 64, no 6, p. 2171-2199Article in journal (Refereed) Published
Abstract [en]

Multi-scale geophysical studies were conducted in the central Skellefte district (CSD) in order to delineate the geometry of the upper crust (down to maximum similar to 4.5 km depth) for prospecting volcanic massive sulphide (VMS) mineralization. These geophysical investigations include potential field, resistivity/induced polarization (IP), reflection seismic and magnetotelluric (MT) data which were collected between 2009 and 2010. The interpretations were divided in two scales: (i) shallow (similar to 1.5 km) and (ii) deep (similar to 4.5 km). Physical properties of the rocks, including density, magnetic susceptibility, resistivity and chargeability, were also used to improve interpretations. The study result delineates the geometry of the upper crust in the CSD and new models were suggested based on new and joint geophysical interpretation which can benefit VMS prospecting in the area. The result also indicates that a strongly conductive zone detected by resistivity/IP data may have been missed using other geophysical data.

Keywords
potential field data, seismic reflection, resistivity, induced polarization, magnetotelluric, 3D modeling
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-316139 (URN)10.1515/acgeo-2016-0088 (DOI)000391967700009 ()
Available from: 2017-03-03 Created: 2017-03-03 Last updated: 2017-11-29Bibliographically approved
Malehmir, A., Zhang, F., Dehghannejad, M., Lundberg, E., Dose, C., Friberg, O., . . . Moller, H. (2015). Planning of urban underground infrastructure using a broadband seismic landstreamer - Tomography results and uncertainty quantifications from a case study in southwestern Sweden. Geophysics, 80(6), B177-B192
Open this publication in new window or tab >>Planning of urban underground infrastructure using a broadband seismic landstreamer - Tomography results and uncertainty quantifications from a case study in southwestern Sweden
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2015 (English)In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 80, no 6, p. B177-B192Article in journal (Refereed) Published
Abstract [en]

We have developed a multicomponent broadband seismic landstreamer system based on digital sensors and particularly suitable for noisy environments and areas in which high-resolution images of the subsurface are desired. We have evaluated results, interpretations, and approaches using the streamer in the planning of an approximately 3-km-long underground tunnel in the city of Varberg in the southwestern Sweden. Prospective targets were imaging of the shallow (<20 m) bedrock surface and weak zones, such as fracture and shear zones. Over the course of three weeks, 25 profiles were acquired with a total length of approximately 7.5 km using a source and receiver spacing of 2-4 m. A novel approach of the data acquisition was to integrate the landstreamer with wireless sensors in areas in which the accessibility was restricted by roads and also to increase the source-receiver distances (offsets). Although the area was highly noisy, the seismic data, in conjunction with available boreholes, successfully led to delineation of the bedrock surface, its undulations, and areas of poor rock quality. To overcome challenges due to geologic complexities and crooked-line data acquisition, 3D tomographic inversion of first breaks was carried out. Comparisons of the results with the existing boreholes indicated that in most places, the bedrock surface was well resolved by the method, which supported the indication of weak zones in the bedrock, represented by low-velocity structures in the tomographic results. We also evaluated the effect of poor geodetic surveying, particularly regarding elevation data, which adulterated the tomography results toward undulating bedrock surfaces or zones of low velocities.

National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-277910 (URN)10.1190/GEO2015-0052.1 (DOI)000368347800048 ()
Funder
Swedish Research Council FormasSwedish Transport Administration
Available from: 2016-02-25 Created: 2016-02-23 Last updated: 2017-11-30Bibliographically approved
Dehghannejad, M. (2014). Reflection seismic investigation in the Skellefte ore district: A basis for 3D/4D geological modeling. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Reflection seismic investigation in the Skellefte ore district: A basis for 3D/4D geological modeling
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Skellefte ore district in northern Sweden is a Palaeoproterozoic volcanic arc and one of the most important ones hosting volcanogenic massive sulfide (VMS) deposits, producing mainly base metals and orogenic gold deposits. Due to high metal prices and increased difficulties in finding shallow deposits, the exploration for and exploitation of mineral resources is quickly being moved to greater depths. For this reason, a better understanding of the geological structures in 3D down to a few kilometers depth is required as a tool for ore targeting. As exploration and mining go deeper, it becomes more and more evident why a good understanding of geology in 3D at exploration depths, and even greater, is important to optimize both exploration and mining.

Following a successful pilot 3D geological modeling project in the western part of the district, the Kristineberg mining area, a new project "VINNOVA 4D modeling of the Skellefte district" was launched in 2008, with the aim of improving the existing models, especially at shallow depth and extending the models to the central district. More than 100 km of reflection seismic (crooked) profiles were acquired, processed and interpreted in conjunction with geological observations and potential field data. Results were used to constrain the 3D geological model of the study area and provided new insights about the geology and mineral potential at depth.

Results along the seismic profiles in the Kristineberg mining area proved the capability of the method for imaging reflections associated with mineralization zones in the area, and we could suggest that the Kristineberg mineralization and associated structures dip to the south down to at least a depth of about 2 km. In the central Skellefte area, we were able to correlate main reflections and diffractions with the major faults and shear zones. Cross-dip analysis, reflection modeling, pre-stack time migration, swath 3D processing and finite-difference seismic modeling allowed insights about the origin of some of the observed reflections and in defining the imaging challenges in the associated geological environments.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. p. 68
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1143
Keywords
Skellefte district, reflection seismic, mineral exploration, 3D/4D modeling, mineralization, faults and shear zones
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-221225 (URN)978-91-554-8937-3 (ISBN)
Public defence
2014-06-05, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Projects
VINNOVA 4D modeling of the Skellefte district
Funder
Vinnova
Available from: 2014-05-14 Created: 2014-03-26 Last updated: 2014-06-30
Bauer, T. E., Tavakoli, S., Weihed, P., Skytta, P., Hermansson, T., Allen, R., . . . Juhlin, C. (2013). A regional scale 3D-model of the Skellefte mining district, northern Sweden. In: Proceedings of the 12th SGA Biennial Meeting 2013.: . Paper presented at 12th Biennial SGA Meeting (pp. 62-65). Uppsala
Open this publication in new window or tab >>A regional scale 3D-model of the Skellefte mining district, northern Sweden
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2013 (English)In: Proceedings of the 12th SGA Biennial Meeting 2013., Uppsala, 2013, p. 62-65Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Uppsala: , 2013
Series
MINERAL DEPOSIT RESEARCH FOR A HIGH-TECH WORLD, VOLS. 1-4
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-259497 (URN)000337983900013 ()978-91-7403-207-9 (ISBN)
Conference
12th Biennial SGA Meeting
Available from: 2015-08-05 Created: 2015-08-05 Last updated: 2017-08-16
Andersson, M., Malehmir, A., Troll, V. R., Dehghannejad, M., Juhlin, C. & Ask, M. (2013). Carbonatite ring-complexes explained by caldera-style volcanism. Scientific Reports, 3, 1677
Open this publication in new window or tab >>Carbonatite ring-complexes explained by caldera-style volcanism
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2013 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, p. 1677-Article in journal (Refereed) Published
Abstract [en]

Carbonatites are rare, carbonate-rich magmatic rocks that make up a minute portion of the crust only, yet they are of great relevance for our understanding of crustal and mantle processes. Although they occur in all continents and from Archaean to present, the deeper plumbing system of carbonatite ring-complexes is usually poorly constrained. Here, we show that carbonatite ring-complexes can be explained by caldera-style volcanism. Our geophysical investigation of the Alno carbonatite ring-complex in central Sweden identifies a solidified saucer-shaped magma chamber at similar to 3 km depth that links to surface exposures through a ring fault system. Caldera subsidence during final stages of activity caused carbonatite eruptions north of the main complex, providing the crucial element to connect plutonic and eruptive features of carbonatite magmatism. The way carbonatite magmas are stored, transported and erupt at the surface is thus comparable to known emplacement styles from silicic calderas.

National Category
Earth and Related Environmental Sciences
Research subject
Earth Science with specialization in Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-200348 (URN)10.1038/srep01677 (DOI)000317581800010 ()
Available from: 2013-05-28 Created: 2013-05-27 Last updated: 2017-12-06
Skytta, P., Bauer, T., Hermansson, T., Dehghannejad, M., Juhlin, C., Juanatey, M. d., . . . Weihed, P. (2013). Crustal 3-D geometry of the Kristineberg area (Sweden) with implications on VMS deposits. Solid Earth, 4(2), 387-404
Open this publication in new window or tab >>Crustal 3-D geometry of the Kristineberg area (Sweden) with implications on VMS deposits
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2013 (English)In: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 4, no 2, p. 387-404Article in journal (Refereed) Published
Abstract [en]

Structural analysis of the Palaeoproterozoic volcanogenic massive sulfide (VMS) hosting Kristineberg area, Sweden, constrained by existing magnetotelluric (MT) and seismic reflection data, reveals that the complex geometry characterized by non-cylindrical antiformal structures is due to transpression along the termination of a major high-strain zone. Similar orientations of the host rock deformation fabrics and the VMS ore lenses indicate that the present-day geometry of the complex VMS deposits in the Kristineberg area may be attributed to tectonic transposition. The tectonic transposition was dominantly controlled by reverse shearing and related upright to overturned folding, with increasing contribution of strike-slip shearing and sub-horizontal flow towards greater crustal depths. Furthermore, the northerly dip of the previously recognized subsurface crustal reflector within the Kristineberg area is attributed to formation of crustal compartments with opposite polarities within the scale of the whole Skellefte district. The resulting structural framework of the main geological units is visualized in a 3D model which is available as a 3-D PDF document through the publication website.

National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-214060 (URN)10.5194/se-4-387-2013 (DOI)000328256200013 ()
Available from: 2014-01-07 Created: 2014-01-07 Last updated: 2017-12-06Bibliographically approved
García Juanatey, M. d., Hübert, J., Tryggavson, A., Juhlin, C., Pedersen, L. B., Dehghannejad, M., . . . Skytta, P. (2013). Magnetotelluric measurements in the Skellefte ore district, northern Sweden. In: : . Paper presented at 12th Biennial SGA Meeting on Mineral Deposit Research for a High-Tech World (pp. 138-141).
Open this publication in new window or tab >>Magnetotelluric measurements in the Skellefte ore district, northern Sweden
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2013 (English)Conference paper, Published paper (Refereed)
Abstract
Series
MINERAL DEPOSIT RESEARCH FOR A HIGH-TECH WORLD, VOLS. 1-4
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-259499 (URN)000337983900032 ()978-91-7403-207-9 (ISBN)
Conference
12th Biennial SGA Meeting on Mineral Deposit Research for a High-Tech World
Available from: 2015-08-05 Created: 2015-08-05 Last updated: 2017-08-11
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