Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
2D and 3D MT in the central Skellefte Ore District, northern 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.ORCID iD: 0000-0002-2511-187X
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.ORCID iD: 0000-0003-2776-0846
Show others and affiliations
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.

Place, publisher, year, edition, pages
2019. Vol. 764, p. 124-138
Keywords [en]
Magnetotellurics, 3D inversion, Deep exploration, Brownfield, Shear zones, Mineral systems
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
URN: urn:nbn:se:uu:diva-178057DOI: 10.1016/j.tecto.2019.04.003ISI: 000472697900008OAI: oai:DiVA.org:uu-178057DiVA, id: diva2:541936
Projects
VINNOVA 4D modeling of mineral belts
Funder
VinnovaAvailable from: 2012-07-26 Created: 2012-07-26 Last updated: 2019-08-16Bibliographically approved
In thesis
1. Seismics, 2D and 3D Inversion of Magnetotellurics: Jigsaw pieces in understanding the Skellefte Ore District
Open this publication in new window or tab >>Seismics, 2D and 3D Inversion of Magnetotellurics: Jigsaw pieces in understanding the Skellefte Ore District
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Skellefte District (SD) is one of the richest metallogenic mining areas in Sweden. The main deposits consist of volcanic-hosted massive sulphides (VHMS) rich in zinc, copper, lead, gold and silver, that have been explored and mined for more than a century. Considering that technological advancements allow deeper mining, and that today new discoveries rarely occur, renewed efforts are now directed at locating targets at greater depths.  

Thus, current exploration strategies need to be adapted, and a better understanding of regional scale structures is necessary. To address these questions the project VINNOVA 4D modeling of the Skellefte District was launched. Its main purpose is to unravel the regional structures and tectonic setting of the SD. To accomplish this, new geological and geophysical data have been acquired in two key localities.

This thesis presents the contribution from 2D and 3D inversion of magnetotelluric (MT) data and seismic reflection data. The main findings include: conductive hydrothermally altered zones within the otherwise resistive rocks of the Skellefte Group, the depth extension of early and postorogenic intrusions, prominent shear zones in the central part of the district, and enhanced reflectivity and conductivity at the base of the Skellefte Group throughout the SD.

Even though the application of these methods is challenged by the complex geological setting of the SD, it is shown that after a careful processing and analysis of the data, they are able to provide a robust image of the deep subsurface. Additionally, the combination of reflection seismics and MT has proved to be a powerful tool for hypothesis testing and to develop the general understanding of the configuration and history of the SD.

Furthermore, two 3D inversion models of MT data are presented and compared with the results of standard 2D determinant inversions. The 3D procedure shows significant improvements in data fit and is able to constrain better the observed model features. Although 3D inversion of MT data is not yet a run of the mill scheme and issues like model assessment and galvanic distortion effects need to be further addressed, results from complex environments with areal coverage, are already superior to those from 2D inversions.

Abstract [sv]

Skellefteåfälten är ett av de viktigaste malmdistrikten i Sverige. Malmkropparna består av vulkaniskvärda Massiva Sulfider (VHMS) rika på Zink, Koppar, Bly, Guld och Silver, och har utforskats och brutits i mer än ett sekel. Med tanke på att de senaste tekniska framstegen tillåter djupare brytning, och att nya upptäckter är ovanliga idag, riktas nya ansträngningar mot att lokalisera malm på större djup.

Aktuella prospekteringsstrategier måste därför anpassas, och en bättre förståelse av regionala strukturer är nödvändig. För att lösa dessa frågor lanserades projektet VINNOVA 4D modeling of the Skellefte District. Dess främsta syfte är att utreda de regionala strukturerna och det tektoniska läget av Skelleftefältet. För att uppnå detta, har nya geologiska och geofysiska data insamlats vid två viktiga platser i distriktet.

Denna avhandling presenterar bidrag från inversionsmodellering i 2D och 3D av magnetotelluriska (MT) data samt resultaten av en reflektionsseismisk profil. De viktigaste resultaten är: bra ledande hydrotermiskt förändrade zoner inom de annars resistiva bergarterna i Skellefte-gruppen, djupet till tidiga och postorogeniska intrusioner, framstående skjuvzoner i den centrala delen av området, och ökad reflektionsförmåga och konduktivitet vid basen av Skellefte-gruppen i hela fältet.

Även om tillämpningen av dessa metoder utmanas av fältens komplexa geologiska läge, visas det efter en noggrann bearbetning och analys av data att de ger en robust bild av den lite djupare berggrunden. Dessutom har kombinationen av reflektionsseismik och MT visat sig vara ett kraftfullt verktyg för hypotesprövning och för att utveckla den allmänna förståelsen av Skelleftefältet och dess historia.

Därutöver presenteras två 3D inversionsmodeller av MT data och jämförs sedan med resultaten från 2D determinantinversioner. 3D tekniker visar betydande förbättringar av datapassform och begränsar observerade anomalier bättre. Även om 3D inversion av MT data ännu inte är en vanlig teknik och frågor som modellbedömning och galvaniska distorsionseffekter måste behandlas ytterligare, är resultat från komplexa miljöer med lagom yttäckning redan överlägsna.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. p. 46
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 946
Keywords
Magnetotellurics, 2D inversion, 3D inversion, hard rock seismics, mineral exploration, integrated geophysics, 4D modeling
National Category
Geophysics
Research subject
Geophysics with specialization in Solid Earth Physics
Identifiers
urn:nbn:se:uu:diva-178060 (URN)978-91-554-8409-5 (ISBN)
Public defence
2012-09-07, Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Projects
VINNOVA 4D modeling of the Skellefte District
Available from: 2012-08-17 Created: 2012-07-26 Last updated: 2013-01-22Bibliographically approved

Open Access in DiVA

fulltext - submitted version(10439 kB)27 downloads
File information
File name FULLTEXT09.pdfFile size 10439 kBChecksum SHA-512
e680e83a69baf1d65d533617d5927ecf035ee3499b4e6d2d11dea8eab191fa6783f375da803d36a1c8120bb4fdcf8d13c015bf4b9cd1d6e4c7280488c5645cba
Type fulltextMimetype application/pdf
fulltext - manuscript version(6903 kB)7 downloads
File information
File name FULLTEXT10.pdfFile size 6903 kBChecksum SHA-512
c3d3224d8f1e19beddcd38fc40db44bb8e9ed3c8b2fe27102d6b37cf31b441dec2fcde15f77d69182b894f59ccab4a0d2ee7ec3b13228f677d58bd255b1272c9
Type fulltextMimetype application/pdf
The full text will be freely available from 2021-04-13 15:31
Available from 2021-04-13 15:31

Other links

Publisher's full text

Search in DiVA

By author/editor
García Juanatey, María de los AngelesHübert, JulianeTryggvason, AriJuhlin, ChristopherPedersen, Laust B.Dehghannejad, Mahdieh
By organisation
Geophysics
In the same journal
Tectonophysics
Geophysics

Search outside of DiVA

GoogleGoogle Scholar
Total: 55 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 2421 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf