Curie depth map for Sinai Peninsula, Egypt deduced from the analysis of magnetic data

Tectonophysics 506 (2011) 46–54

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Tectonophysics j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / t e c t o

Curie depth map for Sinai Peninsula, Egypt deduced from the analysis of magnetic data Essam Aboud a,c,⁎, Ahmed Salem b, Mahmoud Mekkawi c a b c

King Abdulaziz University, Faculty of Earth Sciences, P.O. Box. 80206, Jeddah 21589, Saudi Arabia Getech and University of Leeds, Kitson House, Elmete Hall, Elmete Lane, Leeds LS8 2LJ, UK National Research Institute of Astronomy and Geophysics, 11421 Helwan, Egypt

a r t i c l e

i n f o

Article history: Received 15 October 2010 Received in revised form 5 April 2011 Accepted 13 April 2011 Available online 23 April 2011 Keywords: Sinai Geothermal Magnetic Curie depth point

a b s t r a c t Sinai Peninsula is considered as a unique region in the world due to its geographical location, tectonic and thermal activities. It is located geographically at the crossroads of Europe, Asia, and Africa constituting a triple junction point between the three continents. It is also characterized by thermal manifestations represented by several hot springs with varied temperatures (30–70 °C). Most of these hot springs are located along the shoreline of the Gulf of Suez. In this study, we aim to map the Curie depth isotherm surface for Sinai Peninsula based on the analysis of ground magnetic data. Spectral analysis technique will be used to estimate the boundaries (top and bottom) of the magnetized crust. The depths obtained for the bottom of magnetized crust are assumed to correspond to Curie point depths where the magnetic layer loss its magnetization. Results of this study indicate that the shallow Curie depths (~15–18 km) are located at the southern part of Sinai Peninsula and along the shoreline of the Gulf of Suez and depths increase (22–25 km) towards the central and north western portions of Sinai Peninsula. The whole average Curie depth point of Sinai Peninsula is about 20 km. Generally, the shallow depths to Curie isotherm indicate that Sinai Peninsula is a promising area for further geothermal exploration particularly near the eastern side of the Gulf of Suez. © 2011 Elsevier B.V. All rights reserved.

1. Introduction Sinai Peninsula is surrounded by Mediterranean Sea in the north, Red Sea in the south, Gulf of Suez in the west, and Gulf of Aqaba in the east (Fig. 1) with a unique region in the world. Historically, this region was the origin center of the world's three main religions: Islamism, Judaism, and Christianity. Consequently, it was appraised as the “Holy Land”. The political and ideological conflicts between Arab and Jewish branded it as one of the hottest places in the world. Geographically, it is located at the crossroads of Europe, Asia and Africa as well as geologically at the junction of African continent and Middle East plate. The region has not only a geopolitical importance in global strategies but it is also characterized with obvious landscape and climate differences. Rich rainfall in the Mediterranean coastal region supports its unique climate pattern and dense vegetation. Exposed rocky mountains and valleys with extremely drought desert environmental ecosystem are the prevalent landscape in the central and southern Sinai. These unique features have attracted many researchers to study the region. ⁎ Corresponding author at: Faculty of Earth Science, King Abdulaziz University, P.O. Box. 80206, Jeddah 21589, Saudi Arabia. Tel.: +966 54803972. E-mail address: [email protected] (E. Aboud). 0040-1951/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.tecto.2011.04.010

Sinai Peninsula was covered by ground geological and geophysical surveys by the Egyptian Geological Survey (EGS) as a national project for exploration and development. Ground magnetic measurements were one of the geophysical surveys. In this study we use the ground magnetic data to estimate the Curie depth points for the whole Sinai Peninsula. The idea of using magnetic method to determine the Curie depth is based on the theory proposed by Bhattacharyya (1966) and developed by Spector and Grant (1970), Blakely (1988, 1995), Tanaka et al. (1999), Francisco and Antonio (2003), Ross et al. (2006), and Espinosa-Cardena and Campos-Enriqez (2008). They all use the analysis of power spectrum of the magnetic data to estimate the Curie depths. In this technique, the Curie-temperature isotherm corresponds to the temperature at which magnetic minerals lose their ferromagnetism (approximately 580 °C for magnetite). Magnetic minerals warmer than their Curie temperature are paramagnetic and are essentially nonmagnetic. Thus, the Curie-temperature isotherm corresponds to the basal surface of magnetic crust and can be calculated from the lowest wavenumbers of magnetic anomalies (e.g., Mishra and Naidu, 1974; Byerly and Stolt, 1977; Connard et al., 1983; Hamdy et al., 1984; Salem et al., 2000). In the present study, the ground magnetic data which were collected by the Egyptian Geological Survey (EGS) will be used to

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Fig. 1. The location map of Sinai Peninsula with its most important cities and roads, Egypt.

estimate the Curie depth isotherm map for Sinai Peninsula based on the spectral analysis technique.

2. Geologic setting of Sinai Peninsula Sinai Peninsula is wedged between Africa, Anatolian, and Arabian plates, constituting a transition between the Eastern Egyptian desert and the Middle East region (Ben-Menahem et al., 1976; McKenzie et al., 1970). These regions/plates have been shaped since the Early Mesozoic by a series of rifting phases that formed the northeastern margin of the Afro-Arabian continent (Ben-Avraham and Ginzburg, 1990; Garfunkel, 1998). The boundaries of Sinai Peninsula are defined by the Gulf of Suez and the Gulf of Aqaba-Dead Sea fault System (Mckenzie et al., 1970). The Gulf of Suez has been considered as the site of a very low rate of extension (1 mm/year) and a tectonic subsidence (Steckler et al., 1988). On the other hand, the Gulf of Aqaba–Dead Sea system is a left lateral transform linking to the Zagros–Taurus zone of continental collision with the sea floor spreading in the Red Sea. Many researchers studied

the geology and tectonic setting of Sinai Peninsula area (Ben-Menahem et al., 1976; Garfunkel, 1981, Hall, 1994; McKenzie et al., 1970). Sinai Peninsula covers a land area of approximately 61,000 m2, highly dissected by igneous and metamorphic mountains, which rise to a height of 2675 m (Gebel Musa), forming the southern tip of the Peninsula. In the south, the exposed Pre-Cambrian igneous and metamorphic rocks form a part of the so-called Arabian-Nubian Shield which is a stable tectonic unit. The central part of Sinai Peninsula consists of sub horizontal Mesozoic and Tertiary sediments (Fig. 2), creating the plateau of Gebel El Tih-Egma that represents a thin sedimentary cover, which is affected only by normal faulting (unfolded central Sinai stable foreland). These faults are distinguished into N–S to NNE–SSW, NW–SE and E–W trends. A shear zone of right lateral E–W strike slip faults with up to 2.5 km of displacement has been recognized in Central Sinai; Raqabet El-Naam right lateral wrench fault. Northward from Raqabet El-Naam right lateral wrench fault, the style of deformation becomes complex. The topography comprises low alluvial plains, which are broken by large uplifted Mesozoic domes and anticlines, such as Gebel Yelleg, Gebel Halal and Gebel Maghara. These anticlines are of minor dimensions

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Fig. 2. Geologic map of Sinai Peninsula (Ginzburg et al., 1979; Neev, 1975). The rose diagram shows the main trends of the geologic faults in Sinai Peninsula. Gulf of Suez and Gulf of Aqaba trends can be easily recognized on the rose diagram.

and are oriented in 65°N to 85°E. These anticlinal features have been described as a part of the Syrian Arc System. The Syrian Arc structures attain a more northerly trend aligning themselves with the sinister Dead Sea and the Plusium line, to the east and northeast of Sinai. The area to the north of 30°N is crossed by a strong fractured zone running in NE–SW direction (Hinge Belt). The E–W faults forming the boundaries of the Hinge Belt are as old as the Gulf of Suez faults. The West Sinai Rift area is another structural unit that comprises a narrow elongate rifted plain extending from the Bitter lakes southwards to Ras Mohammed. This part of Sinai is composed essentially of alluvial and wadi deposits. It is also characterized by the presence of a series of normal faults of varying lengths and displacements. All these faults are oriented in NW–SE direction (El Shazly et al., 1974). 3. Magnetic data Sinai Peninsula was covered by regional magnetic survey as a national project for development and exploration within the period of 1991–1998. Data was collected as 3–5 km station interval as easy access location as shown in Fig. 3. Two magnetometers were used to carry out the survey; G856 proton magnetometer from Geometrics

Ltd., and ENVI proton magnetometer from Scintrex Ltd., (Ismail et al. 2001). Diurnal and IGRF corrections were performed and the data was gridded using reasonable grid interval (500 m) in order to produce corrected magnetic anomaly map as shown in Fig. 3. The total intensity magnetic anomaly map of Sinai Peninsula (Fig. 3) shows the distribution and relief of the exposed basement rocks. High magnetic anomalies can be observed at the southern part of Sinai Peninsula which well matches with the exposed geologic units that are mainly composed of igneous rocks (back to geologic map in Fig. 2). It is also can be observed that, Sinai Peninsula can be divided into two geologic provinces based on the magnetic features. The southern province is characterized by high magnetic anomalies and the northern province with low magnetic anomalies. These two provinces are separated by one of the main tectono stratigraphic event, Syrian arc structure (black line on Fig. 3) which forms a fold– thrust belt composed of structure and topographic highs extending from Egyptian western desert, Sinai Peninsula, Levant and Central Syria (Abd El-Motaal and Kusky, 2003). The magnetic map and geologic map show a good correlation between exposed geologic units and magnetic signatures. The southern part of the map shows also several circular magnetic anomalies that could be related to strikeslip movements of the Gulf of Aqaba (Ben-Avraham, 1985). The

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Fig. 3. Magnetic anomaly map of Sinai Peninsula. Black circles show the locations of the magnetic stations.

northern part of the map area is characterized by elongated magnetic anomalies trending in the E–W direction which could be related to the Raqabet El-Naam E–W shear zone (Ghazala, 1994). Other circular anomalies are observed and could be interpreted as uplifting basement or intrusion of dibasic dykes. 4. Curie depth point Magnetic anomalies are analyzed for estimating the depths to the bottom of magnetized bodies in the crust. When these depths are contoured, they reflect the variation of the Curie isotherm level. These variations correlate to a significantly high degree with various known indices of geothermal activity in the area under consideration. Several authors published a scientific paper on this subject as of Spector and Grant (1970), Bhattacharyya and Leu (1975, 1977), Smith et al. (1977) and Byerly and Stolt (1977). More publications have been performed on a country level; Japan (Okubo et al., 1985, 1989; Okubo and Matsunaga, 1994), USA (Blakely, 1988; Mayhew, 1985; Shuey et al., 1977), Greece (Tsokas et al., 1998; Stampolidis and Tsokas, 2002),

Portugal (Okubo et al., 2003), Central Europe (Chiozzi et al., 2005), and Bulgaria (Trifonova et al., 2009). The practical importance of a study on this correlation lies in the possibility of establishing a useful method for rapid regional geothermal exploration. There are two methods to estimate the Curie point depth 1) geothermal method and 2) magnetic method. Geothermal method is based on utilization geothermal data such as heat flow, geothermal gradient, heat production, and heat conduction. The difficulties in employing geothermal method are always relating to the inability of taking direct measurements of geothermal parameters at great depths. At the same time, this method has some advantages for determination of the Curie depth, which are related to the exact value of the Curie point and which should be specified as one of the initial conditions. The use of magnetic method for estimating the Curie depth was based on the theory of Bhattacharyya (1966) where crustal rocks lose their magnetization at the Curie point temperature (570 °C). At this temperature, ferromagnetic rocks become paramagnetic, and their ability to generate detectable magnetic anomalies disappears. The

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Table 1 Comparison between using magnetic method and geothermal method in order to estimate the Curie depth point. Region

Heat flow (mW/m2)

Geothermal gradient (K/km)

Curie depth (km)

Method

Reference

Basin and range province, USA Eastern USA Azerbaijan

35–105 35–63 45–104 33–50 16–123 38–157

25–45 15–25 30–43 20–30 11–94 30–100

22 37 18–32 32–42 10–35 6–12 9–16 4–22 7–17 10 6.5–15

Geothermal method Geothermal method Geothermal method

Blackwell (1971) Blackwell (1971) Pilchin (1983)

Geothermal method Geothermal method Magnetic method Magnetic method

Al-Zoubi (1992) Badalyan (2000) Bhattacharyya and Morley (1965) Shuey et al. (1977)

Magnetic method Magnetic method

Salem et al. (2000) Okubo et al. (1985)

Jordan Armenia Ontario, Canada Yellow stone, USA Quseir, Egypt Kyushu, Japan

Curie temperature for titanomagnetite (the most common magnetic mineral in igneous rocks) is less than approximately 570 °C. Consequently, it may be possible to locate a point on the isothermal surface by determining the depth to the bottom of a polarized rock mass. Thus, the deepest level in the crust creates specific signatures in a magnetic anomaly map which is generally interpreted as the depth to the Curie isotherm. Results of Curie depth point estimation

worldwide using geothermal and magnetic methods are listed in Table 1. 5. Curie point depth estimation To summarize the mathematical formula for the method, assume that the layer extends infinitely far in all horizontal directions, depth

Fig. 4. Nine overlapping subregions (A, B, C, D, E, F, G, H, and I). Each subregion is centered at gray circle and extended 50 km in four main directions. Available heat flow values are posted on the map (F = Feinstein et al. (1996), M = Morgan et al. (1985), G = Girdler and Evans (1977)).

E. Aboud et al. / Tectonophysics 506 (2011) 46–54

to top bound of a magnetic source is small compared with the horizontal scale of a magnetic source, and that magnetization M (x, y) is a random function of x and y. Blakely (1995) introduced the power– density spectra of the total-field anomaly ΦΔT:


 ΦΔT kx ; ky = ΦM kx ; ky F kx ; ky  2

2  −2jkjzt 2 2 1−e−jkjðzb −zt Þ F kx ; ky = 4π 2 Cm jΘm j Θf  e

ð1Þ

is power–density spectra of the magnetization ΦM Cm is proportional constant m and f are factors for magnetization direction and geomagnetic field direction, respectively. Zt and Zb are top and basal depth of magnetic source, respectively. The above equation can be simplified by noting that all terms, except |m|2 and |f |2 are radially symmetric. The radial average of m and f is constant. If M (x, y) is completely random and uncorrelated, ΦM(kx, ky) is constant. Hence, the radial average of ΦΔT is: −2jkjZt

ΦΔT ðjkjÞ = A e


 −jkjðZb −Zt Þ 2 1−e

ð2Þ

where A is a constant. For wavelengths less than about twice the thickness of the layer, Eq. (2) can be simplified as: h i 1=2 = ln B−jkjZt ln ΦΔT ðjkjÞ

ð3Þ

where B is a constant. Okubo et al. (1985) proposed an algorithm to estimate the basal depth from magnetic data by considering a two-dimensional modeling technique for the determination of the depth to the base for a single block with the average parameters of the ensemble. Then, the algorithm estimates the depth to the centroid (z0) from the slope of radially averaged frequency-scaled power spectrum in the low wavenumber part and depth to the top (zt) from the slope of radially averaged power spectrum of magnetic anomaly. From the slope of the power spectrum of total field anomaly, Zt can be estimated. Consequently, Eq. (2) can be written as: 1=2

ΦΔT ðjkjÞ

−jkjZ0

= Ce




−jkjðZt –Z0 Þ

e

−jkjðZb –Z0 Þ

−e



51

spectrum, that is, there is sensitivity to finite data length (Ravat et al., 2007). This is one of the limitations of the spectral analysis. The advantage of the spectrum analysis of a magnetic anomaly is that estimates of the top bound and the centroid of a magnetic source can be obtained with simple assumptions of the dimension of magnetic sources and the magnetization vector. 6. General assumptions and limitations A number of general assumptions and limitations are associated with this Curie depth estimation. A complete discussion of these limitations is given in Blakely (1995) and Ross et al. (2006). A summary of these limitations is given here. Firstly, deep magnetic sources have long wavelengths and low amplitudes, which make them difficult to distinguish from anomalies caused by shallow sources. The dimension of the subregion must be sufficiently large to capture these long wavelengths, which forces a trade-off between accurately determining Zb within each subregion and resolving small changes in Zb across subregions. Secondly, subtle discontinuities can occur along survey boundaries owing to differences in survey specifications, regional-field removal, and quality of data acquisition. These discontinuities can contribute long-wavelength noise to the regional compilation and may contaminate long-wavelength signal caused by deep magnetic sources. Third, the assumption of random magnetization is critical to this spectral-analysis method in order that the power–density spectrum be a constant. The degree of randomness, however, depends on the geology of the region. The magnetization of an extrusive volcanic layer, for example, may have different statistical properties from plutonic rocks (Blakely, 1988). Fedi et al. (1997) and Pilkington et al. (1994) have shown that magnetization has a degree of correlation and have suggested power-law decay rates to correct for this correlation. There is no agreement on the decay rates that should be

ð4Þ

where C is constant. At long wavelength, Eq. (4)is rewritten as: 1=2

ΦΔT ðjkjÞ

−jkjZ0

= Ce




−jkjð−dÞ

e

−jkjðdÞ

−e

 −jkjZ0 2jkjd e Ce

ð5Þ

where 2d is the thickness of magnetic source. From Eq. (5), it can be concluded that: ln

nh o i 1=2 ΦΔT ðjkjÞ jkj = ln D−jkj Z0

=

ð6Þ

where D is constant. By fitting a straight line through the high and low wavenumber parts from the radially average power spectrum of ln [ΦΔT (|k|)1/2] and [ΦΔT (|k|)1/2]/|k|, Zt and Z0 can be estimated. Finally, the basal depth of the magnetic source is: Zb = 2Z0 −Zt

ð7Þ

The obtained basal depth of the magnetic source is assumed to be the Curie point depth. The obtained Curie point depth reflects the average value of the area. Therefore the results may not delineate local shallow or deep Curie point depth anomaly. Magnetic anomalies which are only partly included in the data may degrade the estimated

Fig. 5. Example of power spectrum for one subregion and linear fitting to estimate Zt (a) and Z0 (b).

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Table 2 Values of the top, centroid, and basal depths of the magnetic sources including error estimation for each. Subregion Zt km Error Zt Z0 km Error Z0 Zb = 2 Z0 − Zt km (top depth) (± km) (centroid depth) (± km) (basal depth) A B C D E F G H I

5.20 5.90 4.10 4.90 4.80 5.30 4.50 5.04 5.0

0.14 0.28 0.09 0.03 0.06 0.21 0.04 0.07 0.11

12.5 12.06 14.40 12.20 13.3 11.40 11.30 12.80 9.7

0.37 0.51 1.46 0.43 1.00 0.99 0.87 1.60 0.12

19.80 18.22 24.70 19.50 21.80 17.50 18.10 20.56 14.40

used, however, so we have assumed a purely uncorrelated magnetization in our investigation. 7. Data processing and analysis Trifonova et al. (2009) estimated the Curie depth point in six blocks with dimensions 300 × 300 km of Bulgaria using the criteria of minimal size of the block that does not cut the spectral peak. Tanaka

et al. (1999) divided the East and Southeast Asia into subregions data (≅200 × 200 km) and estimated the power density spectra for each region from which they calculated the Curie depth map. Blakely (1988) divided the area of Nevada into subregions (120 × 120 km) in terms of magnetic aeromagnetic data and mapped the Curie depth of Nevada state. Connard et al. (1983) divided a magnetic data of Cascade Range, central Oregon into overlapping cells (77 × 77 km) and calculated the radially average power spectrum for each cell. However, the spectrum of the map only contains a depth information to a depth of length/2π (Shuey et al., 1977). In our study, magnetic data of Sinai Peninsula area was divided into overlapping nine subregions (A, B, C, D, E, F, G, H, and I) with an area of (100 km by 100 km) in an average area size of (10,000 km2) for each region. For each subregion, Curie depth point was located at the center of the subregion as shown in Fig. 4. The selection of the previous dimensions was based on the criteria of minimal size of the block that does not cut the spectral peak (Ravat et al., 2007). Power density spectrum was calculated for each grid. The most advantage of the 2D power spectrum is that the depth of sources is easily determined from by measuring the slope of the energy (power) spectrum and dividing it by 4π. An example of power spectrum of a subregion in central Sinai is shown in Fig. 5A.

Fig. 6. Map of Curie depth of Sinai Peninsula with contour line interval of 2 km. Gray circles show the centers of subregions.

E. Aboud et al. / Tectonophysics 506 (2011) 46–54

Once the depth to the top bound was estimated, the previous technique was applied to radially averaged frequency-scaled power (Fig. 5B) to estimate the centroid depth (Z0). Consequently, the basal depth (Zb) is then obtained using Eq. (7). In our study, we followed the Okubo et al. (1985) procedures and estimated the depths to the top and centroid magnetic sources (Zt and Z0) as listed in Table 2. The depths to the top bound of the magnetic sources are ranging between 4 and 6 km while the depth of the centroid magnetic sources varied from 9 to 14 km. Manual approximation was used to spread out the Curie depths to produce Curie depth “contour map” reflecting an approximate pattern of the Curie isotherm depth map of Sinai Peninsula. Curie depth data were gridded and manually contoured as shown in Fig. 6. The Curie depths in continental areas are generally deeper than those in oceanic areas (Tanaka et al., 1999). This well agree with the results of Curie depths in Sinai Peninsula where Fig. 6 shows that along the shore line of the Gulf of Suez, shallow Curie depths are observed (15–18 km) while deep Curie depths (22–25 km) are located at the central and north western part of Sinai Peninsula. The available heat flow data of the Gulf of Suez (Morgan et al., 1985) were posted in Fig. 4 indicating that low heat flow is located near Suez city (the upper northern part of the Gulf of Suez) with a value of 40–52 mW/m2 corresponding with N25 km Curie depth values. Passing by Hammam Faroun area (the highest temperature

53

hot spot in Egypt, 70 °C) the heat flow reaches to be the highest values (N104 mW/m2) corresponding with b20 km Curie depth values. It can be recognized that, the heat flow values re-decrease toward south direction along the Gulf of Suez (e.g. Abu Rudies city, 60–65 mW/m2, El-Tur city, 65–70 mW/m2). These results indicate that the highest heat flow values (N104 mW/m2) and shallow Curie depth point are located at/around Hammam Faroun area. 8. Curie depth map and seismicity of Sinai Peninsula Egyptian National Seismic Network (ENSN) continuously records the seismicity data allover Egypt. This data is available within the National Research Institute of Astronomy and Geophysics (NRIAG). Geostatistical analysis of the seismicity data of the Sinai Peninsula (ENSN, 2007) within the period of 1995–2007 indicates that the main depth for all earthquakes is about 14–16 km which associated with the average Curie depth point along the Gulf of Suez. Moreover, the seismicity in the Gulf of Suez and Gulf of Aqaba is higher than the central Sinai Peninsula which also agrees with the Curie depth contour map. Fig. 7 shows the distributions of the earthquakes in Sinai Peninsula based on depth variation. This seismic activity could be the main reason for the possibility of thermal accumulation which could be responsible for the observed Curie depths. Geostatistical analysis of

Fig. 7. Curie depth contour map and the locations of the earthquakes in Sinai Peninsula.

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the seismicity data indicates that the mean depth of the earthquakes is about 13 km (mean Curie depth is about 16 km). 9. Discussion and conclusion The ground magnetic data was used successfully to map the Curie depths in Sinai Peninsula. The results indicated that the Curie depth is as shallow as 15–18 km along the southern part of Sinai Peninsula and eastern border of the Gulf of Suez and as deep as 22–25 km at the central and northwestern part of Sinai Peninsula with an average Curie depth point of 20 km for the whole Sinai Peninsula. Morgan et al. (1985) studied the heat flow measurements from wells in the eastern Egypt and Gulf of Suez and concluded that the highest heat flow values more (N115 mW/m2) are located along the Gulf of Suez. The results of the Curie depth estimation and the available heat flow data indicate that the Gulf of Suez is a promising area for geothermal exploration particularly at Hammam Faroun area. From the previous results, we recommend further more detailed studies at Hammam Faroun area (magnetotelluric, electromagnetic, and geochemical studies) in order to evaluate and model the subsurface geothermal reservoir. Finally, based on the seismicity data; there are great heterogeneities surrounding the Sinai subplate (the eastern borders are greater than the western borders) explaining, to a great extent, the variation in the earthquake activities from east to west (Abdel-Rahman et al., 2009). While inside the Sinai subplate, the heterogeneities are lower than that of both Gulfs of Aqaba and Suez. This agrees with the results of Curie depths where shallow Curie depths can be observed at both Gulfs (Suez and Aqaba) and deep at the central part of Sinai. We can conclude that once there are seismic activities, shallow Curie depths could be observed unless there is an active rift. References Abd El-Motaal, E., Kusky, T.M., 2003. Tectonic evolution of the intraplate S-shaped Syrian arc fold–thrust belt of the middle east region in the context of plate tectonics. The Third International Conference on the Geology of Africa, vol. 2, pp. 139–157. Abdel-Rahman, K., Al-Amri, A., Abdel-Moneim, E., 2009. Seismicity of Sinai Peninsula, Egypt. Arab J. Geosci. 2, 103–118. Al-Zoubi, A., 1992. Deep geologic composition of Jordan by geophysical data, Ph.D. thesis, Mining Institute. Sankt-Petersburg (in Russian). Badalyan, M., 2000. Geothermal features of Armenia: a country update, Trans. of the World Geothermal Congress, Kyushu—Tohoku, Japan, May 28–June 10 2000, pp. 71–76. Ben-Avraham, Z.O., 1985. Structural framework of the Gulf of Elat (Aqaba), Northern Red Sea. Geophys. Res. 90, 703–726. Ben-Avraham, Z., Ginzburg, A., 1990. Displaced terranes and crustal evolution of the Levant and East Mediterranean. Tectonics 9, 613–622. Ben-Menahem, A., Amos, N., Moshe, V., 1976. Tectonics, seismicity and structure of the Afro-Eurasian Junction. The breaking of an incoherent plate. Phys. Earth Planet. Inter. 12 (1), 1–50. Bhattacharyya, B.K., 1966. Continuous spectrum of the total magnetic field anomaly due to a rectangular prismatic body. Geophysics 31, 97–121. Bhattacharyya, B.K., Morley, L.W., 1965. The delineation of deep crustal magnetic bodies from total field aeromagnetic anomalies. J. Geomagn. Geoelectr. 17, 237–252. Bhattacharyya, B., Leu, L., 1975. Spectral analysis of gravity and magnetic anomalies due rectangular prismatic bodies. Geophysics 42, 41–50. Bhattacharyya, B.K., Leu, L.K., 1977. Spectral analysis of gravity and magnetic anomalies due to rectangular prismatic bodies. Geophysics 42, 41–50. Blackwell, D.D., 1971. The thermal structure of the continental crust. In: Heacock, J.D. (Ed.), The Structure and Physical Properties of the Earth's Crust: AGU, Geophys. Monogr. Ser., vol. 14, pp. 169–184. Blakely, R.J., 1988. Curie temperature isotherm analysis and tectonic implications of aeromagnetic data from Nevada. J. Geophys. Res. 93, 817–832. Blakely, R.J., 1995. Potential Theory in Gravity and Magnetic Applications. Cambridge University Press, Cambridge. Byerly, P.E., Stolt, R.H., 1977. An attempt to define the Curie point isotherm in northern and central Arizona. Geophysics 42, 1394–1400. Chiozzi, P., Matsushima, J., Okubo, Y., Pasquale, V., Verdoya, M., 2005. Curie-point depth from spectral analysis of magnetic data in central–southern Europe. Phys. Earth Planet. Inter. 152, 267–276. Connard, G., Couch, R., Gemperle, M., 1983. Analysis of aeromagnetic measurements from the Cascade Range in central Oregon. Geophysics 48, 376–390.

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