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

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • 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
Delineating hydrothermal stockwork copper deposits using controlled-source and radio-magnetotelluric methods:  A case study from northeast Iran
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics. (Electromagnetic studies)
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. (Electromagnetic studies)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics. (Electromagnetic studies)
Show others and affiliations
2009 (English)In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 74, no 5, B167--B181 p.Article in journal (Refereed) Published
Abstract [en]

Radio- and controlled-source-tensor magnetotelluric (RMT and CSTMT)   methods are used to target hydrothermal veins of copper mineralization.   The data were acquired along six eastwest- and three   north-south-trending profiles, covering an area of about 500 x 400   m(2). The tensor RMT data were collected in the 10-250-kHz frequency   band. A double horizontal magnetic dipole transmitter in the 4-12.5-kHz   frequency range allowed us to constrain the deeper parts of the   resistivity models better. To obtain optimum field parameters, ground   magnetic profiling was conducted prior to the RMT and CSTMT surveys.   Although the study area (in Iran) is remote, a number of radio   transmitters with acceptable signal-to-noise ratio were utilized. The   2D inversion of RMT data led to unstable resistivity models with large   data misfits. Thus, the RMT data were used to complement and analyze   the near-surface resistivity anomalies observed in the 2D CSTMT models.   Analyses of strike and dimensionality from the CSTMT data suggests that   the low-resistivity structures are mainly three dimensional; therefore,   2D inversion of determinant data is chosen. Independent 2D inversion   models of the determinant CSTMT data along crossing profiles are in   good agreement. Known copper mineralization is imaged well in the CSTMT   models. The thinning of the conductive overburden correlates very well   with magnetic highs, indicating the bedrock is resistive and magnetic.   In this sense, the magnetic and electromagnetic fields complement each   other. Analysis of the 2D resistivity models indicates the volcanic   rock deepens at the center of the study area. This zone is associated   with a magnetic low and therefore is recommended for detailed   exploration work.

Place, publisher, year, edition, pages
2009. Vol. 74, no 5, B167--B181 p.
Keyword [en]
electromagnetics, 2D, magnetics, inversion, magnetotelluric
National Category
Earth and Related Environmental Sciences
Research subject
Geophysics with specialization in Solid Earth Physics; Mineral Chemistry, Petrology and Tectonics
Identifiers
URN: urn:nbn:se:uu:diva-102769DOI: 10.1190/1.3174394ISI: 000270381400005OAI: oai:DiVA.org:uu-102769DiVA: diva2:216726
Available from: 2009-05-11 Created: 2009-05-11 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Controlled Source Radiomagnetotelluric (CSRMT) Applications in Environmental and Resource Exploration
Open this publication in new window or tab >>Controlled Source Radiomagnetotelluric (CSRMT) Applications in Environmental and Resource Exploration
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

An integrated use of radio magnetotelluric (RMT) and controlled source tensor magnetotelluric (CSTMT) measurements, the so-called CSRMT method, has been employed in environmental and resource exploration studies. A number of case histories, including a groundwater investigation in glacial deposits, a study of fracture zones for geotechnical purposes and a mining exploration study of a copper deposit, are presented in this thesis in order to illustrate the usefulness and capability of the CSRMT method. The resolutions of the estimated models using various types of data are studied. Magnetotelluric transfer functions are used to analyze the dimensionality, the near surface resistivity distortions and the near field effects in the case of CSTMT data analysis. The near field effects in CSTMT data have also been identified by performing 2½D forward modelling.

Data analysis, dimensionality tests and forward modelling show that at the lowest frequencies used the CSTMT transfer functions are generally distorted by source effects, except when the source-receiver distances are sufficient large compared with the penetration depth. Regarding CSTMT transfer functions, apparent resistivities are generally less distorted than phases. TM mode transfer functions are more affected by the sources than TE mode, while tipper vectors generally contain source signatures at all frequencies.

Based on the analysis of dimensionality and source effects 2D inverse modelling of CSTMT and RMT data, as well as their combination, have been performed under the plane wave assumption. The RMT method proved to be a powerful tool for imaging the upper 50 m near-surface, but their penetration depth reduces as a conductive layer structures cover the targets at depth. The penetration depth can be increased by including the CSTMT data in the modelling if the measurements are in the far field range. The resolution of the deeper parts of the models may be improved by performing a joint inversion of TE and TM modes, if the strike direction is well-defined. Alternatively, inversion of determinant data can be performed, since the determinant data are less affected by 3D structures and source effects. However the resolution of the determinant models is somewhat degraded compared to the models inverted from combined TE and TM modes.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 66 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 655
Keyword
Magnetotelluric, radio magnetotelluric, controlled-source tensor magnetotelluric, plane wave, near surface geophysics, sediment, fracture zone, inversion, forward modelling, near field effect, two-dimensional model, three-dimensional model, resolution
National Category
Geophysics
Research subject
Earth Sciences with Specialization Environmental Analysis; Hydrology; Mineral Chemistry, Petrology and Tectonics
Identifiers
urn:nbn:se:uu:diva-102750 (URN)978-91-554-7550-5 (ISBN)
Public defence
2009-06-05, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2009-05-14 Created: 2009-05-11 Last updated: 2009-05-25Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Malehmir, AlirezaIsmail, NazliPedersen, Laust

Search in DiVA

By author/editor
Malehmir, AlirezaIsmail, NazliPedersen, Laust
By organisation
Geophysics
In the same journal
Geophysics
Earth and Related Environmental Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 557 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • 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