2D inversion of the magnetotelluric data from Mahallat geothermal field in Iran using finite element approach
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The natural-field magnetotelluric (MT) method has proven very useful for mapping the geothermal fields as resistivity sections. The depth of investigation of the MT method is sufficiently large to penetrate deep into the upper crust. MT soundings along two transects across Mahallat geothermal field in Iran were carried out to determine the crustal structure in the region. The selected MT profiles in the region cross over the hydrothermally altered zones and different geological structures. Data were acquired along two profiles crossing the Mahallat hot springs with a total of 28 MT stations in a frequency range of 8,000 to 0.008 Hz. Spacing between stations was kept 500 m for a good resolution. We have used the code MT2DInvMATLAB for inversion using the method of finite elements for forward modeling. Apparent resistivity and phase data of transverse electric (TE), transverse magnetic (TM), and TE + TM modes along each profile were modeled. The geothermal fluid reservoir is resolved at 1,000 to 3,000 m depth and the geothermal resource is estimated to be located at 7,000 m or deeper.
KeywordsElectrical resistivity Geothermal Interpretation Magnetotelluric Mahallat 2D inversion
The research council of the University of Tehran (UT) is acknowledged for the financial support of the first author’s sabbatical leave at Uppsala University (UU) in the period of October 2011 to October 2012. The Department of the Earth Sciences of UU is also appreciated for hosting the first author as guest researcher. We would like to thank Dr. M. Mirzaei from Arak University in Iran for the financial support of the field work and also Dr. M. Montahaee for her useful guidance on the data processing.
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