Contents lists available at ScienceDirect Renewable and Sustainable Energy Reviews journal homepage: www.elsevier.com/locate/rser Curie point depth, heat flow and geothermal gradient maps of Egypt deduced from aeromagnetic data S. Elbarbary a , M. Abdel Zaher a, ⁎ , H. Mesbah a , A. El-Shahat b , A. Embaby c a National Research Institute of Astronomy and Geophysics (NRIAG), 11421 Helwan, Cairo, Egypt b Geology Department, Faculty of Science, Mansoura University, 35516, Egypt c Geology Department, Faculty of Science, Damietta University, 34517, Egypt ARTICLE INFO Keywords: Geothermal resources Aeromagnetic Curie point depth Geothermal energy Heat flow ABSTRACT Regular annual reports issued by the Ministry of Electricity and Energy show that the established power gen- erating capacity of Egypt is based mainly on oil and natural gas resources. Due to its high energy demand, Egypt needs clean, renewable, alternative energy sources. From this perspective, it is earnestly imperative to utilize geothermal resources to produce power and add to the Egyptian energy supply in a clean and efficient way. This paper reviews the state-of-the-art geothermal resources in Egypt with an emphasis on the current investigation utilizing aeromagnetic data. Power spectral analysis was applied to the aeromagnetic data to estimate the Curie point depth (CPD), heat flow and geothermal gradient. The CPDs range from 8.6 to 35.7 km, the derived geo- thermal gradients vary from 16.3 to 67.4 °C/km, and the heat flow values range from 47.1 to 195.5 mW/m 2 . The relation between the CPDs and seismic activity was also examined. Most of the earthquakes that originated in areas with CPDs of less than 25 km are considered promising regions for geothermal exploration, especially in the Gulf of Suez. The results of the current study may guide governmental and private sectors interested in the geothermal energy industry to select the most appropriate geothermal power plant sites in Egypt. 1. Introduction Geothermal resources supply vital information on the sustainable power source represented by the Earth's internal heat. Egypt lies in the northeastern corner of Africa; it is bounded to the north by a zone of compression in the northeastern Mediterranean and to the east by the Red Sea and Gulf of Suez spreading centers [1,2]. Several studies have been conducted on the geothermal resources of Egypt [3–13]. In the southern part of the Mediterranean Ridge in northern Egypt, the heat flow is characterized by low and generally uniform values [14] that may be the result of a thick sedimentary cover [15]. Hence, the northern part of Egypt does not offer promising geothermal resources. In contrast, heat flow determinations from the northern Red Sea region yield high values (125–250 mW/m 2 ) associated with the axial depres- sion of the Red Sea rift [16]. The northern Red Sea occupies a critical position in the transition from continental to oceanic rifting and ex- tension [17]. The Red Sea-Gulf of Aden rift system is generally inter- preted as an embryonic and youthful sea basin shaped by the separation of a landmass [18]. In northeastern Egypt, the Red Sea bifurcates into the Gulf of Suez and the Gulf of Aqaba around the small Sinai Peninsula. The regional thermal anomaly therein is possibly related to the formation of the Red Sea. The Red Sea and the Gulf of Suez are re- sponsible for the geothermal activity around the Gulf of Suez [4]. The heat flow values in the southern part of the Gulf of Suez range from 45 to 115 mW/m 2 , which suggests that there is an anomalous hydro- thermal heat source located at relatively shallow depths that is likely due to the uplift of the basement in the area [13]. The geothermal gradient beneath the eastern coast of the Gulf of Suez varies between 20 and 44 °C/km with a heat flow ranging from 45 to 120 mW/m 2 that increases toward the rift axis of the Gulf of Suez [7]. The Hammam Faraun area has a subsurface temperature of 94.5 °C and a heat flow of approximately 122 mW/m 2 according to geothermometer data [9]. The average geothermal gradient in the Nile Delta ranges between 18.1 and 26.5 °C/km, indicating that the Nile Delta is a geothermally anomalous area due to lithological variations [19]. The geothermal gradient in the northern Western Desert is generally 30 °C/km, although a few locally high geothermal gradients (40 °C/km) are observed and are explained by potential local geothermal fields [12]. In this paper, the geological and tectonic setting of Egypt and the associated geothermal manifestations are briefly discussed to evaluate the geothermal resources therein. Furthermore, aeromagnetic data are used to estimate the Curie point depth (CPD), temperature gradient, https://doi.org/10.1016/j.rser.2018.04.071 Received 24 June 2017; Received in revised form 21 November 2017; Accepted 14 April 2018 ⁎ Corresponding author. E-mail address: moh_zaher@nriag.sci.eg (M. Abdel Zaher). Renewable and Sustainable Energy Reviews 91 (2018) 620–629 1364-0321/ © 2018 Elsevier Ltd. All rights reserved. T