Curie Point Depth, Geothermal Gradient and Heat-Flow Estimation and Geothermal Anomaly Exploration from Integrated Analysis of Aeromagnetic and Gravity Data on the Sabalan Area, NW Iran

Abstract

Prospecting the geothermal resources in northwest of Iran, conducted in 1975, revealed several promising areas and introduced the Sabalan geothermal field as a priority for further studies. The Sabalan Mt., representing the Sabalan geothermal field, is a large stratovolcano which consists of an extensive central edifice built on a probable tectonic horst of underlying intrusive and effusive volcanic rocks. In this study, Curie point depth (CPD), geothermal gradient and heat-flow map were constituted from spectral analysis of the aeromagnetic data for the NW of Iran. The top of the geothermal resource (i.e., the thickness of the overburden) was evaluated by applying the Euler deconvolution method on the residual gravity data. The thickness of the geothermal resource was calculated by subtracting the Euler depths obtained from the CPDs in the geothermal anomalous region. The geothermal anomalous region was defined by the heat-flow value greater than 150 mW/m2. CPDs in the investigated area are found between 8.8 km in the Sabalan geothermal field and 14.1 in the northeast. The results showed that the geothermal gradient is higher than 62 °C/km and the heat-flow is higher than 152 mW/m2 for the geothermal manifestation region; the thickness of the geothermal resource was also estimated to vary between 5.4 and 9.1 km. These results are consistent with the drilling and other geological information. Findings indicate that the CDPs agree with earthquake distribution and the type of thermal spring is related to the depth of the top of the geothermal resource.