Implications for a Geothermal Reservoir at Abgarm, Mahallat, Iran: Magnetic and Magnetotelluric Signatures

Abstract

One of the well-known geothermal potential areas in Iran is the Abgarm in Mahallat region. Due to existence of several hot springs, the Abgarm area is of particular importance in geothermal studies. To investigate the geothermal mechanism at Abgarm, geophysical surveys of magnetometry and magnetotelluric (MT) were utilized near hot springs to image the geometry of all geological requisites for trapping a geothermal reservoir. The ground magnetic data were inverted in 3D to construct a magnetic susceptibility model, where a deep intrusive igneous rock (as a heat source) and a shallow magmatic lava were inferred from the physical model. Euler depth estimation also provided insight to a shallow granodiorite unit embedded in a thick sequence of sediments. Dimensionality and strike analysis of the MT data were performed through the phase tensor method to investigate the general geometry of the sought reservoir for running a 2D TE + TM mode inversion scheme. Through 2D inversion of the MT data along three profiles across the favorable zones, the electrical resistivity models were used to image sedimentary units (i.e., cap rock, top soil, bedrock and reservoir) and magmatic rocks. Considering both geophysical properties led to illustrate a plausible geothermal reservoir in the area.