Curie Point Depth Estimations for Northwest Iran Through Spectral Analysis of Aeromagnetic Data for Geothermal Resources Exploration

Abstract

The northwest of Iran is considered as a promising geothermal zone owing to its geographical properties, tectonic features, and thermal activities, particularly in Sabalan geothermal field. Several large stratovolcanoes such as Sahand and Sabalan mountains in northwestern Iran, each of which has a vast central dome probably located on a tectonic plate, comprising of intrusive and effusive volcanic rocks. This study mainly aimed at performing the spectral analysis of aeromagnetic data to estimate Curie point depth (CPD), geothermal gradient and heat flow in the northwest of Iran using random magnetization (centroid method and forward modeling of the spectral peak method) and fractal magnetization (de-fractal method). The reduced-to-pole aeromagnetic data were divided into 55 overlapping blocks of 80 × 80 km. The derived range of CPD in the study area using the centroid method, forward modeling spectral peak method and de-fractal method were 9.2–13.9 km, 8.9–13.7 km and 7.2–12.9 km, respectively The derived values of heat flows in the study area using the above-mentioned methods were higher than 104 mW/m2, 105 mW/m2 and 120 mW/m2, respectively. The results of this study were found to have good correlations with wells data and resistivity measurements collected in the Northwest Sabalan geothermal field. Good consistency was also found between the CDPs and earthquake distribution. Moreover, the locations of hot springs and the maximum temperatures of the wells were associated with the variations in the modelled depth of the geothermal resources. Promising regions were in the northeast and southwest parts of the study area.