Estimation of Curie point depths and heat flow from Ardebil province, Iran, using aeromagnetic data
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ORIGINAL PAPER
Estimation of Curie point depths and heat flow from Ardebil province, Iran, using aeromagnetic data Allahyar Khojamli 1 & Faramarz Doulati Ardejani 2 & Ali Moradzadeh 2 & Ali Nejati Kalate 3 & Amin Roshandel Kahoo 3 & Soheil Porkhial 4
Received: 12 March 2015 / Accepted: 26 February 2016 / Published online: 27 April 2016 # The Author(s) 2016. This article is published with open access at Springerlink.com
Abstract This study attempts to estimate the Curie point depth (CPD) using the centroid and forward modelling of the spectral peak methods in the Sabalan geothermal field in Ardabil, NW of Iran. The reduced-to-pole aeromagnetic data were divided into 18 overlapping blocks of the sizes of 100 × 100 km. In the centroid method, the average depth to the top of the deepest crustal block, Zt, was first computed by linear fitting to the second longest wavelength segment of the power spectrum of aeromagnetic data. Then, depth to the centroid of the deepest crustal block, Z0, was computed by linear fitting to the longest wavelength segment of the power spectrum of the aeromagnetic data. The depth to the magnetic bottom was obtained from Zb = 2Z0 − Zt. In the forward modelling of the spectral peak method, the modelled spectra fitted to the observed spectrum iteratively and Zt and Zb were finally estimated. According to the obtained results, the CPD
* Allahyar Khojamli [email protected] Faramarz Doulati Ardejani [email protected] Ali Moradzadeh [email protected] Ali Nejati Kalate [email protected]
1
Faculty of Engineering, Malayer University, Hamadan, Iran
2
School of Mining, College of Engineering, University of Tehran, Tehran, Iran
3
Faculty of Mining, Petroleum and Geophysics, Shahrood University of Technology, Shahrood, Iran
4
Renewable Energy Organization of Iran (SUNA), Tehran, Iran
varies from 10 to 18.6 km. The Curie temperature of magnetite was used to determine the thermal gradient and the heat flow in the area. The study area is found to have a great energy potential in the west, northwest and the southwest of the Sabalan with shallow CPD, high geothermal gradient and heat flow. Keywords Curie point depth . Aeromagnetic . Geothermal . Sabalan . Spectral analysis
Introduction The Curie point (approximately 580 °C for magnetite at atmospheric pressure) is the temperature at which the spontaneous magnetization vanishes and magnetic minerals show paramagnetic susceptibility. The depth at which temperature reaches the Curie point is assumed to be the bottom of the magnetized bodies in the earth crust. Curie point temperature varies from region to region depending on the geology and the mineralogical content of the rocks. Therefore, one can normally expect shallow Curie point depth (CPD) at the regions which have geothermal potential, young volcanisms and thin crust (Aydin and Oksum 2010). The assessment of the variations in the Curie depth of an area can provide valuable information about the regional temperature distribution at depth and the potential of subsurface geothermal
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