uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Hübert, Juliane
Publications (10 of 12) Show all publications
García Juanatey, M. d., Hübert, J., Tryggvason, A., Juhlin, C., Pedersen, L. B., Bauer, T. E. & Dehghannejad, M. (2019). 2D and 3D MT in the central Skellefte Ore District, northern Sweden. Tectonophysics, 764, 124-138
Open this publication in new window or tab >>2D and 3D MT in the central Skellefte Ore District, northern Sweden
Show others...
2019 (English)In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 764, p. 124-138Article in journal (Refereed) Published
Abstract [en]

New broadband magnetotelluric (MT) data have been acquired along two parallel profiles in the central part of the metallogenic Skellefte district in northern Sweden. The data were recorded as part of the Swedish 4D modelling of mineral belts project and cover an area with several economical and sub-economical deposits. The dimensionality and quality of the data were carefully analyzed and new error floors were systematically determined prior to inverse modelling in 2D and 3D. The algorithms used were EMILIA and WSINV3DMT. For the 2D inversion, only the determinant of the impedance tensor was used, while for the 3D inversion all elements were considered. The obtained models fit the inverted data, and image the main regional features. A detailed comparison reveals the superiority of the 3D model, both in model structures and data fit. After assessing the main features in the model, an interpretation is proposed and refined with the support of previous geophysical studies. The most interesting features are large and medium-sized conductors associated with crustal-scale shear zones and faults within the Skellefte Group rocks. These may be depicting a network of fossil pathways for hydrothermal fluid transport and as such, provide new insight into past processes in the area.

Keywords
Magnetotellurics, 3D inversion, Deep exploration, Brownfield, Shear zones, Mineral systems
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-178057 (URN)10.1016/j.tecto.2019.04.003 (DOI)000472697900008 ()
Projects
VINNOVA 4D modeling of mineral belts
Funder
Vinnova
Available from: 2012-07-26 Created: 2012-07-26 Last updated: 2019-08-16Bibliographically approved
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
Show others...
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. & Pedersen, L. B. (2013). Imaging the Kristineberg mining area with two perpendicular magnetotelluric profiles in the Skellefte Ore District, northern Sweden. Geophysical Prospecting, 61(1), 200-219
Open this publication in new window or tab >>Imaging the Kristineberg mining area with two perpendicular magnetotelluric profiles in the Skellefte Ore District, northern Sweden
2013 (English)In: Geophysical Prospecting, ISSN 0016-8025, E-ISSN 1365-2478, Vol. 61, no 1, p. 200-219Article in journal (Refereed) Published
Abstract [en]

New magnetotelluric (MT) data from two perpendicular profiles in the Kristineberg area, northern Sweden, were analysed and modelled. In the Skellefte Ore District, the Kristineberg volcanic hosted massive sulphide (VHMS) deposit mine is one of the largest and deepest (1250 m). Seventeen broadband magnetotelluric stations were installed along two existing seismic reflection lines. The profiles were 6 and 12 km long with 500 m and 1 km site spacing, respectively. The obtained MT transfer functions in the period range of 0.0015–200 s are of fairly good quality. Detailed strike and dimensionality analysis reveal consistent but period dependent, strike directions, indicating a change in the geoelectrical strike with depth. From the two-dimensional inversion of the determinant of the impedance tensor, two stable conductivity models with good data fit were obtained. The addition of seismic reflection information from the co-located survey, improved the data fit of one of them. Extensive sensitivity analyses helped to delineate the well resolved regions of the models and to determine the position of pronounced boundaries. The results are in good agreement with previous studies, especially regarding the presence of a deep conductor interpreted as a structural basement to the district. They also reveal with more detail the configuration of the main geological units of the Skellefte Ore District, especially of the ore bearing volcanic rocks and the embedded alteration zones.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2013
Keywords
Mining, Magnetotelluric, 2D inversion
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-163596 (URN)10.1111/j.1365-2478.2011.01040.x (DOI)000312548300015 ()
Projects
VINNOVA 4D modeling of the Skellefte District
Available from: 2011-12-13 Created: 2011-12-13 Last updated: 2017-12-08Bibliographically 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
Show others...
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
García Juanatey, M. d., Tryggavson, A., Juhlin, C., Bergström, U., Hübert, J. & Pedersen, L. B. (2013). MT and reflection seismics in northwestern Skellefte Ore District, Sweden. Geophysics, 78(2), B65-B76
Open this publication in new window or tab >>MT and reflection seismics in northwestern Skellefte Ore District, Sweden
Show others...
2013 (English)In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 78, no 2, p. B65-B76Article in journal (Refereed) Published
Abstract [en]

A seismic reflection and MT survey was carried out along a 27-km long transect in northwestern Skellefte District, as part of a bigger 3D modeling project. The main motivation for the data acquisition is to elucidate the geologic relationship between the known mineralizations in the Adak mining camp to the north and in the well studied Kristineberg area south of the transect. The seismic reflection data were acquired with a VIBSIST system, and show reflectivity down to 3 s. Apart from the conventional processing for crystalline environments, the seismic data was also subject to an azimuthal binning procedure and cross-dip analysis, allowing the orientation of planar reflectors in 3D. Regarding the MT data, it is primarily of good quality along the 17 installed sites. The inversion of the determinant of the impedance tensor yielded a stable 2D resistivity model, dominated by resistors corresponding to the postorogenic intrusions along the transect. Adding the location of the analyzed seismic reflectors in the MT inversion rendered an integrated model that facilitated a preliminary joint interpretation of the data sets. Overall, the results are in good agreement with surface observations and reveal a crude configuration of the geologic units below the transect. The most prominent outcomes are the lateral and depth extent of the large postorogenic intrusions in the area reaching to 5- or 6-km depth, the dimensions of the nearly vertical Brännäs gabbro extending to 6-km depth, and the presence of enhanced conductivities along the transect at about 10 km depth. The latter is probably related to the deep conductor previously identified in the district.

Place, publisher, year, edition, pages
Society of Exploration Geophysicists, 2013
Keywords
2D, magnetotelluric, mining, imaging, inversion
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-178056 (URN)10.1190/geo2012-0169.1 (DOI)000319858000002 ()
Projects
VINNOVA 4D modeling of the Skellefte District
Available from: 2012-07-26 Created: 2012-07-26 Last updated: 2017-12-07
Hübert, J., García Juanatey, M. d., Malehmir, A., Tryggavson, A. & Pedersen, L. B. (2013). The upper crustal 3-D resistivity structure of the Kristineberg area, Skellefte district, northern Sweden revealed by magnetotelluric data. Geophysical Journal International, 192(2), 500-513
Open this publication in new window or tab >>The upper crustal 3-D resistivity structure of the Kristineberg area, Skellefte district, northern Sweden revealed by magnetotelluric data
Show others...
2013 (English)In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 192, no 2, p. 500-513Article in journal (Refereed) Published
Abstract [en]

A 3-D model of the crustal electrical resistivity was constructed from the inversion of magnetotelluric data in the Kristineberg area, Skellefte district, the location of one of Sweden's most successful mining activities. Forward modelling of vertical magnetic transfer data supports our model which was derived from the magnetotelluric impedance only. The dominant features in the 3-D model are the strong conductors at various depth levels and resistive bodies of variable thickness occurring in the shallower subsurface. The deepest conductor, previously associated with the Skellefte crustal conductivity anomaly, is imaged in the southern part of the area as a north-dipping feature starting at similar to 4 km depth. Several shallow conductors are attributed to graphite in the black shales defining the contact between the metasedimentary rocks and the underlying metavolcanic rocks. Furthermore, an elongated intermediate depth conductor is possibly associated with alteration zones in the metavolcanic rocks that host the ore occurrences. The most prominent crustal resistors occur in the southern and northern part of the area, where their lateral extent on the surface coincides with the late-orogenic Revsund type intrusions. To the east, a resistive feature can be correlated to the early-orogenic Viterliden intrusion. The 3-D model is compared with two previous 2-D inversion models along two perpendicular profiles. The main electrical features are confirmed with the new model and previous uncertainties regarding 3-D effects, caused by off-profile conductors, can be better assessed in 3-D, although the resolution is lower due to a coarser model discretization. The comparison with seismic sections along two north-south profiles reveals structural correspondence between electrical features, zones of different reflectivity and geological units.

Keywords
Crustal structure, Electrical properties, Magnetotelluric
National Category
Geophysics Natural Sciences
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-163597 (URN)10.1093/gji/ggs044 (DOI)000313623100004 ()
Available from: 2011-12-13 Created: 2011-12-13 Last updated: 2017-12-08Bibliographically approved
Bastani, M., Hübert, J., Kalscheuer, T., Pedersen, L. B., Godio, A. & Bernard, J. (2012). 2D joint inversion of RMT and ERT data versus individual 3D inversion of full tensor RMT data: An example from the Trecate site in Italy. Geophysics, 77(4), WB233-WB243
Open this publication in new window or tab >>2D joint inversion of RMT and ERT data versus individual 3D inversion of full tensor RMT data: An example from the Trecate site in Italy
Show others...
2012 (English)In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 77, no 4, p. WB233-WB243Article in journal (Refereed) Published
Abstract [en]

Tensor radiomagnetotelluric (RMT) and electrical resistivity tomography (ERT) data were acquired along 10 parallel lines to image electrical resistivity of the vadose and the saturated zone in an area near Trecate, 45 km west of Milan in Italy. In 1994, the area was exposed to an oil contamination caused by a tank explosion and has since been subject to monitoring and remediation programs. For the first time, we have examined a 3D inversion of full tensor RMT data and have compared the results with 2D joint inversion of RMT and ERT data. First, a synthetic 3D resistivity model with similar variations close to those measured at the Trecate site was generated for the comparison. The synthetic tests showed that resistivity models from 2D joint inversion of ERT and RMT data contain more details closer to the surface compared to the models from the 3D inversion of tensor RMT data. High resistivity structures are better resolved by the 2D joint inversion, whereas the more conductive features are better recovered by the 3D inversion. In the next step, the ERT and RMT data collected in the Trecate site were modeled with the same approaches used in the synthetic modeling. Using the measured tensor RMT data, it was possible to carry out full 3D inversion to study the underlying geology. Comparison between the resistivity models from both inversions with the lithological data from the existing boreholes, resistivity models from the inversion of crosshole resistivity data, and water content models from magnetic resonance soundings measurements showed that the electrical resistivity, depth to the top and thickness of the water saturated zone is modeled more accurately With the 3D inversion.

National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-165142 (URN)10.1190/GEO2011-0525.1 (DOI)000307799500022 ()
Available from: 2012-01-03 Created: 2012-01-03 Last updated: 2017-12-08Bibliographically approved
Hübert, J. (2012). From 2D to 3D Models of Electrical Conductivity based upon Magnetotelluric Data: Experiences from two Case Studies. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>From 2D to 3D Models of Electrical Conductivity based upon Magnetotelluric Data: Experiences from two Case Studies
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Magnetotelluric measurements are among the few geophysical techniques capable of imaging the structure both in the shallow subsurface as well as the entire crust of the Earth. With recent technical and computational advances it has become possible to derive three-dimensional inversion models of the electrical conductivity from magnetotelluric data, thereby overcoming the problems arising from the simplified assumption of two-dimensionality in conventional two-dimensional modeling. The transition from two-dimensional to three-dimensional analysis requires careful reconsideration of the classical challenges of magnetotellurics: galvanic distortion, data errors, model discretization and resolution.This work presents two examples of magnetotelluric investigations, where a new three-dimensional inversion algorithm has been applied. The new models are compared with conventional two-dimensional models and combined with the results of other geophysical techniques like reflection seismics and electrical resistivity tomography. The first case presents magnetotelluric investigations of the Kristineberg mining area in the Skellefte district, northern Sweden. This study is part of a joint geophysical and geological project to investigate the present structure and evolution of the whole district. Together with reflection seismic and surface geological information a three-dimensional conductivity model, derived through the inversion of magnetotelluric data, was interpreted. A comparison with two-dimensional modeling gives insights into the capabilities and challenges of three-dimensional inversion strategies with respect to data sampling and model resolution.The second case presents a study of remediation monitoring  with geophysical methods after an oil blow-out in Trecate, Italy. A three-dimensional conductivity model was derived from radiomagnetotelluric measurements. In addition, two-dimensional joint inversion of radiomagnetotelluric and electrical tomography data was performed. Compared with electrical resistivity tomography, radiomagnetotelluric data is more sensitive to conductors and the derived three-dimensional inversion model resolves the vadose zone and the underlying aquifer.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. p. 58
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 890
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-165143 (URN)
Public defence
2012-02-17, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2012-01-27 Created: 2012-01-03 Last updated: 2012-02-15Bibliographically approved
Skyttä, P., Bauer, T., Tavakoli, S., Weihed, P., Allen, R., Dehghannejad, M., . . . Hübert, J. (2011). 4-dimensional geological modelling of mineral belts. In: : . Paper presented at Bergforsk Annual Meeting 2011 : 04/05/2011 - 05/05/2011.
Open this publication in new window or tab >>4-dimensional geological modelling of mineral belts
Show others...
2011 (English)Conference paper, Oral presentation only (Other academic)
National Category
Geology
Research subject
Ore Geology; Applied Geophysics
Identifiers
urn:nbn:se:uu:diva-327819 (URN)
Conference
Bergforsk Annual Meeting 2011 : 04/05/2011 - 05/05/2011
Available from: 2017-08-11 Created: 2017-08-11 Last updated: 2017-08-16Bibliographically approved
Garcia Juanatey, M. d., Hübert, J., Juhlin, C., Malehmir, A. & Tryggavson, A. (2011). Integrated MagnetoTelluric and seismic reflection study: Skellefte Ore District, northern Sweden. In: : . Paper presented at Society of Exploration Geophysicists (SEG) Annual Meeting, 18-23 September 2011, San Antonio, Texas, USA (pp. 1247-1251). , 30(1)
Open this publication in new window or tab >>Integrated MagnetoTelluric and seismic reflection study: Skellefte Ore District, northern Sweden
Show others...
2011 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

The Skellefte District is a very rich mining area in northern Sweden. The main deposits consist of volcanic-hosted massive sulphides VHMS rich in zinc, copper, lead, gold and silver. Since the area has been mined and explored for over a century, today's challenge is to locate deeper deposits. The VINNOVA 4D modeling project aims to address this challenge by understanding the regional setting of the district and its evolution over time. © 2011 Society of Exploration Geophysicists.

Series
SEG Technical Program Expanded Abstracts, ISSN 1949-4645
Keywords
Case history, Europe, Magnetotelluric, Mining, Seismic
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-165353 (URN)10.1190/1.3627429 (DOI)
Conference
Society of Exploration Geophysicists (SEG) Annual Meeting, 18-23 September 2011, San Antonio, Texas, USA
Projects
VINNOVA 4D modelling of the Skellefte district
Available from: 2012-01-05 Created: 2012-01-05 Last updated: 2017-01-25Bibliographically approved
Organisations

Search in DiVA

Show all publications