Magnetotelluric Survey of NW Sabalan Geothermal Project, Iran

Abstract

2-D-resistivity modeling of the data from the latest MT survey undertaken in 2007 was used to map a shallow resistivity anomaly located east of Pad E and west of the young lava domes of the Post-caldera Kasra Volcanic Formation. The anomaly is postulated to represent the possible upflow region of the NW Sabalan geothermal field. The interface between the conductive layer and the underlying higher resistivity body lies beneath Moil Valley at an elevation of ~2000 m asl and shoals toward the southeast. It is shallowest east of Pad E at an elevation of ~2500 m asl. This interface coincides with the base of the smectite zone in Wells NWS-1 and NWS-4, where temperatures exceeding 180ºC were measured. It is inferred that elevated temperatures most likely exceeding 240ºC could be encountered beneath the shallowest part of the interface of the conductive and the high resistivity layers.
The general NW trend of the resistivity anomaly at a depth of 800 m and elevations of 2300 m asl and 2600 m asl is consistent with the major structural fabric of the Moil Valley. This indicates that faults along this direction exhibit good permeability and are attractive drilling targets. A resistivity gradient between stations 6 and 7 is inferred to be a possible southeastern extension of NNW3 Fault and is a good drilling target to test the projected higher temperature in the area east of Pad E.