Thermal structure of the Cappadocia region, Turkey: a review with geophysical methods

Abstract

This study is a review paper collecting all previous investigations on the thermal structure and the geothermal potential of the Cappadocia region. The main purpose of this review is to reveal the geothermal potential of the research area and stimulate the geothermal exploration. The scientific objective of this paper is to present a compilation of previous studies on the thermal behavior of the crust in the Cappadocia region and to indicate the geothermally prospective areas in the region. Authors of this study commenced the search of potential geothermal areas in Turkey using the aeromagnetic anomalies, starting from the Central Anatolia. They initiated the investigations of shallow crustal structure of Cappadocia, first and determined recently formed depressions down to 2 km. In the second stage of these research activities, detailed CPD calculations were performed and mapped throughout Cappadocia. They found an elliptical shallow CPD anomaly up to 7 km where the geothermal gradient is obtained as 68 °C/km in the apex of the anomaly. In connection with these values, heat flows were estimated up to 210 mW/m, while the radiogenic heat production is being observed as maximum of 0.70/μWm in this area. These calculations are different and more encouraging than the general regional heat-flow map of Turkey calculated previously from the hot springs and bottom-hole temperatures of shallow wells. A possible magma chamber beneath the caldera-like circular depression between Nevsehir–Aksaray–Nigde–Yesilhisar cities is thought to be the main reason for high heat flow and high geothermal gradient in association with the young volcanism in and around Cappadocia. Due to lack of reservoir units, hydrothermal–geothermal energy possibility is not expected in this region. On the other hand, large anomalous area between Nigde, Aksaray and Nevsehir presents very high hot dry rock (HDR) energy potential which is considered as the most prospective geothermal energy type in the future.