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Heat flow in Eastern Egypt: The thermal signature of a continental breakup
Abstract
The Red Sea is a modern example of continental fragmentation and incipient ocean formation. Heat flow data have been collected from eastern Egypt to provide information relating to the mode and mechanism of Red Sea opening. Preliminary heat flow data, including new data reported here, are now available from twenty-five sites in eastern Egypt and one site in western Sinai. A pattern of low to normal heat flow (35–55 mW m−2) inland with high heat flow (75–100 mW m−2) in a zone within 30 to 40 km of the coast is indicated.Moderately high heat flow (around 70 mW m−2) is indicated for the Gulf of Suez. The coastal zone thermal anomaly appears continuous with high heat flow previously reported for the Red Sea shelf. Heat production data indicate that the coastal thermal anomaly is not primarily related to crustal radiogenic heat production. The effects of rapid erosion may contribute to the anomaly, but are not thought to be the primary cause of the anomaly. If the anomaly is caused by lateral conduction from hot, extended, offshore lithosphere, the extension must have been active for the last 30 Ma or so, and a minimum of 100% extension is indicated. Alternatively, the anomaly is primarily caused by high mantle heat flow causing lithospheric thinning, centred beneath the Red Sea. The Red Sea is probably underlain by dominantly basic crust, formed either by intrusion into attenuated continental crust or sea-floor spreading, and for most purposes the crust formed in these two modes of extension may be essentially indistinguishable. Fission-track ages from eastern Egypt indicate that uplift started prior to, or at latest at the time of initial Red Sea opening, and this result, together with thermo-mechanical considerations, suggests an active asthenospheric upwelling beneath the Red Sea and high temperature in the lithosphere prior to extension.
Supplementary resources (2)
... All t-T paths with <0.05 GOF did not appear in the model; ≥0.05 (≥5%) rates were accepted models and presented in green, and ≥0.5 (≥50%) rates were good models represented in purple in the model. Additionally, the code calculated the best GOF model and displayed it in black, and the model with the weighted mean value was displayed in blue [94,95]. ...
... Thermal history models reconstructed using the HeFTy code [104]. The resulting t-T path represent four levels of reliability; acceptable fit (green), good fit (purple), the best fit (black), an the weighted mean (blue) paths [95,104]. Five constraints were used to limit the modeling random ness, where the 1st represented the initial box at depth, the 2nd represents the post-accretion-relate exhumation event, the 3rd shows the ZFT age, the 4th shows the AFT age, and the 5th represent the Suez Rift opening. ...
... Thermal history models reconstructed using the HeFTy code [104]. The resulting t-T paths represent four levels of reliability; acceptable fit (green), good fit (purple), the best fit (black), and the weighted mean (blue) paths [95,104]. Five constraints were used to limit the modeling randomness, where the 1st represented the initial box at depth, the 2nd represents the post-accretion-related exhumation event, the 3rd shows the ZFT age, the 4th shows the AFT age, and the 5th represents The obtained AFT cooling ages did not reset during the Oligocene-Miocene rift-related exhumation event (the youngest AFT age is ca. ...
The Suez Rift developed as a northern extension of the Red Sea rift during the Oligocene-Miocene, whose flanks were constructed from the Neoproterozoic basement rocks of the Arabian–Nubian Shield. These basement rocks are comprised of the whole tectonic history since their formation. The Suez Rift initiation model and proposed thermal overprint role in the rifting process and flank development remain uncertain. Additionally, the amplitude of different regional tectonic events’ effects on the region is still debatable. Integration of fission-track thermochronology data with modeling of the time-temperature history has demonstrated efficiency in addressing such issues. In the context of this study, eleven representative samples were collected from the different rock units in the Wadi El-Dahal area at the northern tip of the western flank of the Suez Rift. These samples revealed Carboniferous zircon fission-track cooling ages of 353 ± 9 Ma and 344 ± 11 Ma. Meanwhile, the apatite fission-track analysis provided two spatially separated age groups: Permian-Triassic and Late Cretaceous, with average ages of 249 ± 11 Ma and ca. 86 ± 10 Ma, respectively. The time-temperature modeling revealed four possible cooling pulses representing exhumation events, which were initiated as a response to four tectonic activities: the accretion-subsequent event of erosion during the Neoproterozoic, the Hercynian (Variscan) tectonic event during the Devonian-Carboniferous, the Mid-Atlantic opening during the Cretaceous, and the Suez Rift opening during the Oligocene-Miocene. The western flank of the Suez Rift suggests a passive mechanical type with no extra thermal overprint, as indicated by the dominance of older thermochronological ages, modest rift flank elevations, and a reduction in the heat flow.
... The CPDs derived from 20 km LP wavelength filtering applied to TMI and RTP data are of approximately the same range (from 15 to 25 km) and spatial distribution. Conversely, applying a [69][70][71]. Black circles represent the centers of the analyzed regions. All maps are superimposed by the triangle of the exposed basement rocks and other major structural elements. ...
... A comparison was carried out between the estimated HF from all magnetic datasets except the 40 km LP wavelength RTP, and the available HF data within the western, southern, and the eastern portions of the Sinai Peninsula [69][70][71]). Feinstein et al. [69] and Morgan et al. [70] used the data from the bottom hole temperature and recognized that the topmost part of the Gulf of Suez (Suez city) is characterized by low HF with a value of 40-52 mW/m 2 that increases southward, reaching 80 mW/m 2 in the Ras Garra area (Figure 6f). ...
... A comparison was carried out between the estimated HF from all magnetic datasets except the 40 km LP wavelength RTP, and the available HF data within the western, southern, and the eastern portions of the Sinai Peninsula [69][70][71]). Feinstein et al. [69] and Morgan et al. [70] used the data from the bottom hole temperature and recognized that the topmost part of the Gulf of Suez (Suez city) is characterized by low HF with a value of 40-52 mW/m 2 that increases southward, reaching 80 mW/m 2 in the Ras Garra area (Figure 6f). Further to the eastern part of Sinai Peninsula, Girdler and Evans [71] showed that the median value of HF along the Gulf of Aqaba is approximately 92 mW/m 2 . ...
The estimation of the Curie point depth (CPD) and heat flow (HF) from magnetic data is useful for geothermal and tectonic studies. However, the methodology of estimating these values is still controversial as numerous studies have used different types of transformed magnetic data. Most studies utilize the total magnetic intensity (TMI) or the reduced to the pole (RTP) data, and since shallow magnetic bodies may affect the final CPD values, low-pass (LP) wavelength filtering has also been used to estimate the CPD. In this study, the two-dimensional radially averaged spectral analysis was applied to the land-based magnetic data from the Sinai Peninsula. TMI and RTP data were both analyzed, using different LP filtered wavelengths, and the final CPD and HF values were compared. The cut-off wavelength parameter was selected in terms of the geologic complexity. The results show that the estimated CPD values are well correlated regardless of whether the magnetic data were either TMI or RTP. The RTP data produced a spatial shift in the CPD smaller than the window size being used. Additionally, the centroid method is primarily dependent on the wavenumber, which varied slightly on applying the RTP. There were slight differences in the estimated CPDs when a short LP filter (e.g., 20 km) was applied, whereas increasing the wavelength (e.g., 40 km) caused the CPD values to increase exceeding the plausible depth limits, and the associated spatial trends varied when compared to the other methods. In areas where the basement rocks were shallow or exposed, a LP filter can be applied with short cut-off wavelength. The estimated CPDs were discussed in the context of seismicity data, gravity-based Moho depths, and HF measurements.
... (M. Abdel Zaher) The geothermal potentiality of Egypt has been investigated by many authors in different regions, such as Morgan et al. (1983Morgan et al. ( , 1985, Swanberg et al. (1983), Boulos (1990), Hosney (2000), Abdel Zaher et al. (2011a, 2011b, 2012a, 2012b, Lashin (2013Lashin ( , 2015, Chandrasekharam et al. (2015Chandrasekharam et al. ( , 2016aChandrasekharam et al. ( , 2016b, Mohamed et al. (2015), and Atef et al. (2016). GIS-based techniques have been applied in many countries, such as northern Japan (Noorollahi et al., 2007), USA (Coolbaugh et al., 2005), Iran (Yousefi et al., 2010;Noorollahi et al., 2008), and Italy (Trumpy et al., 2015(Trumpy et al., , 2016, to detect geothermal resources. ...
... The average value is about 31°C/km which is closer to the world average (30°C/km). On the other hand, thermal conductivities of bottom formation in each well was calculated based on data from Morgan et al. (1983Morgan et al. ( , 1985 and information about type of bottom formation; 3.2 ± 0.1 W/m°C for basement rocks; 2.4 ± 0.2 W/m°C for sandstone; 2.2 ± 0.2 W/m°C for carbonate rocks. ...
... The El-Gouna region, which is located south of the Gulf of Suez, yields a higher geothermal probability, which may be identified with the Sinai triple intersection of Africa, Arabia, and Sinai. 9. Heat flow map of Egypt based on a combination of temperature data from 596 deep onshore and offshore wells, which was provided by the Egyptian General Petroleum Corporation and thermal conductivity of the rocks (average of 2.65 W/m°C) (Morgan et al., , 1985. The map indicates that heat flow increases eastward of Egypt towards Red Sea and Gulf of Suez regions. ...
The energy of Egypt is generally derived from petroleum products. However, advancements in the development of the generation capacity using sustainable and renewable resources, for example, solar, wind and geothermal resources and investment in nuclear power plants are planned. The geology and structure setting of Egypt affirms that reasonable geothermal resources are available, particularly along the Gulf of Suez, the Red Sea, the Western Desert and parts of the Nile Valley. The main objective of this research is to develop a geothermal favourability map of Egypt, which may be considered as a screening tool for the assessment of optimal areas for geothermal development. Digital data layers and maps were employed in a GIS model to select the most promising areas for geothermal potentiality. The ArcGIS model includes six thematic layers: distance to faults, Bouguer anomaly, distance to seismic activity, Curie depth, heat flow, and temperatures at different depths. The validation of the generated geothermal favourability map was performed by a comparison with thermal water wells and hot springs. Generally, the most encouraging zones for geothermal probability in Egypt are located near the shorelines of the Gulf of Suez and the Red Sea.
... Previous studies of heat flow and geothermal regime in Egypt (Issar et al., 1971;Morgan and Swanberg, 1979;Morgan et al., 1980Morgan et al., , 1985Swanberg et al., 1983;Boulus, 1990;Zaghloul et al., 1995;Hosney, 2000) related the geothermal features to the tectonic evolution of the area. ...
... The low heat flow of the Eastern Mediterranean Sea extends at least as far south as 29 • N (Morgan et al., 1977;Čermák and Hurtig, 1977;Riad et al., 1989). Boulos (1990), Morgan et al. (1980Morgan et al. ( , 1983Morgan et al. ( , 1985, Feinstein et al. (1996), Hosney and Morgan (2000), Hosney (2000) and Saleh et al. (2013) studied the heat flow values along the Gulf of Suez and Red Sea. ...
... These sources were discovered and interpreted by several authors (Makris and Ginzburg, 1987;Saleh et al., 2006;Abdel Zaher et al., 2011;Salem et al., 2014) with gravity, magnetics and seismics. Morgan et al. (1985) indicated a pattern of low to normal heat flow (35-55 mW m −2 ) inland with high heat flow (75-100 mW m −2 ) in a zone within 30 to 40 km of the coast of the Red Sea. They pointed out a moderately high heat flow (around 70 mW m −2 ) for the Gulf of Suez. ...
In the present study, we have attempted to map the plate boundary between Arabia and Africa at the Northern Red Sea rift region including the Suez rift, Gulf of Aqaba-Dead Sea transform and southeastern Mediterranean region by using gravity data analysis. In the boundary analysis method which was used; low-pass filtered gravity anomalies of the Northern Red Sea rift region were computed. Different crustal types and thicknesses, sediment thicknesses and different heat flow anomalies were evaluated. According to the results, there are six subzones (crustal blocks) separated from each other by tectonic plate boundaries and/or lineaments. It seems that these tectonic boundaries reveal complex structural lineaments, which are mostly influenced by a predominant set of NNW–SSE to NW–SE trending lineaments bordering the Red Sea and Suez rift regions. On the other side, the E–W and N–S to NNE–SSW trended lineaments bordering the South-eastern Mediterranean, Northern Sinai and Aqaba-Dead Sea transform regions, respectively. The analysis of the low pass filtered Bouguer anomaly maps reveals that the positive regional anomaly over both the Red Sea rift and South-eastern Mediterranean basin subzones are considered to be caused by the high density of the oceanic crust and/or the anomalous upper mantle structures beneath these regions whereas, the broad medium anomalies along the western half of Central Sinai with the Suez rift and the Eastern Desert subzones are attributed to low-density sediments of the Suez rift and/or the thick upper continental crustal thickness below these zones. There are observable negative anomalies over the Northern Arabia subzone, particularly in the areas covered by Cenozoic volcanics. These negative anomalies may be attributed to both the low densities of the surface volcanics and/or to a very thick upper continental crust. On the contrary, the negative anomaly which belongs to the Gulf of Aqaba-Dead Sea transform zone is due to crustal thickening (with limited heat flow values) below this region. Additionally in this study, the crustal thinning was investigated with heat flow, magnetic and free air gravity anomalies in the Northern Red Sea rift region. In fact, the crustal thinning of the study area was also proportional to the regions of observable high heat flow values. Finally, our results were found to be well correlated with the topography, free air, aeromagnetic and heat flow dataset profiles crossing most of the study area.
... Heat flow measurements from boreholes on either side of Suez Gulf and in the eastern desert regions have been reported by several authors (Evans and Tammemagi 1974;Girdler 1970Girdler , 1977Gettings 1982;Gettings and Showail 1982;Morgan et al. 1977Morgan et al. , 1981Morgan et al. , 1983Morgan et al. , 1985. The heat flow values measured over the sediments and granites and gneisses along the eastern desert are shown in Fig. 9 and the heat flow profile across the eastern desert extending from the Red Sea coast over a distance of about 200 km is also shown in Fig. 10. ...
... The heat flow values measured over the sediments and granites and gneisses along the eastern desert are shown in Fig. 9 and the heat flow profile across the eastern desert extending from the Red Sea coast over a distance of about 200 km is also shown in Fig. 10. The heat flow values reported by Morgan et al. (1985) are low for the eastern desert region due to lack of large number of observation boreholes. For Giggenbach (1988) showing the chemical variation in the thermal waters, cold and Nile River waters example, the heat generated by the El Hidi granites, east of Aswan City, is about 107 mW/m 2 (Table 1) and high value is not reflected in the data published by the earlier authors while assessing the heat flow values of areas away from the Red Sea coast. ...
... But now, the country has a safe option to generate freshwater through EGS Fig. 10 Heat flow profile across the eastern desert (south of 26°l atitude, Fig. 9), Egypt. Stars (granites) and triangles (sediments) were reported by Morgan et al. (1985). The heat flow values of El Hudi and El Missikat granites ( Fig. 9; Table 2) are included to show the wide heat flow values across the desert Fig. 11 Subsurface temperature at 2 ad 3 km depth, eastern desert Egypt source to meet the freshwater demand from domestic, agricultural and industrial sectors. ...
Future energy security and CO2 emissions investigation models indicate that the best option for Egypt is to adopt a mitigation strategy by using geothermal energy as an energy source mix and implement energy efficiency policy. The hydrothermal potential is estimated to be of the order of 158 × 106 kWh while El Faliq high heat-generating granite has the potential to generate billion kWh of electricity. Through these two geothermal energy sources, the country can mitigate CO2 reduction to the order of 20 million tones and provide sustained freshwater to domestic, agricultural and industrial sectors. Egypt in future may have to address two important issues such as guaranteed future electricity supply and freshwater supply to meet the growing population and agriculture demand. The current situation indicates that the Nile River may not be able to sustain the demand due to uncertainties in the monsoon pattern and reduction in storage capacity. A renewable energy (geothermal) source mix and implementing a sound energy efficient policy in agricultural, transport and domestic sectors will help the country to meet the future food and water demand of the country.
... To account for the presence of radioactive geothermal sources, the thermal conductivity of the study area was determined by calculating the average value from previous measurements taken along the region. Previous studies by Morgan et al. (1983), Morgan et al. (1985), reported an average thermal conductivity value of 2.9 W/m°C for the study area. The computed CDP, thermal gradient (TG), and heat flow (HF) maps of the study area, obtained using the spectral method applied to reduced-to-pole (RTP) maps, are shown in Fig. 6. ...
... The previously published data was divided into two types: well data and radioactive sample analysis, as illustrated in Fig. 10. The first type is well data, which was gathered along the research area and was previously reported by Morgan et al. in 1985. The wells are listed in Table 1, which provides a range of TG values from 8 °C/km to 55 °C/km and HF values from 21 to 179 mW/m 2 , with varying total depths. ...
This research paper presents a comprehensive investigation into the untapped geothermal potential of Egypt’s Central Eastern Desert, highlighting its viability as a promising contender in the pursuit of sustainable energy resources. Through a rigorous multi-disciplinary approach, we systematically assess the feasibility of deploying geothermal energy in the region, supported by meticulous analysis of diverse data sources, including aeromagnetic and radiometric datasets. Our study identifies two primary sources of heat flow energy: granitic rocks enriched with radioactive minerals and dynamic geological motions. By using techniques such as derivative analysis, power spectra analysis, and heat flow calculations, we evaluate the geothermal potential using aeromagnetic data. The tilted derivative operator enables the detection of geological structures, while Curie depth points (CDPs) provide insights into the geothermal gradient and heat flow maps, revealing the distribution of subsurface heat. Surface heat flow calculations further assess the energy generation potential. Additionally, our analysis incorporates methods to estimate radioactive heat production within geological formations, considering uranium, thorium, and potassium isotopes. The ratios of potassium to thorium and uranium to thorium serve as indicators of hydrothermal alteration zones. The research findings reveal a wide range of heat flow values within the depths of the Curie depth point (CDP), ranging from 200 to 700 W/m2. At the surface, observed heat flow values range from 6 to 22 mW/m2, although relatively lower in magnitude, still hold significant potential for energy production. It is important to acknowledge the contribution of radioactive minerals, as the heat production from these sources ranges from 0 to 35 W/m3. Collectively, these heat sources present viable opportunities for energy extraction, particularly in the area between Safaga and Qusier and the area south of Qusier to Marsa Allam. Surface heat flow and radioactive heat production offer promising prospects for sustainable energy generation.
... Cooling, exhumation rates, and episodic rock uplift were inferred by extraction from t-T models, assuming ca. 20°C surface temperature, and 25°C/km and 50°C/km geothermal gradients (Morgan et al., 1985;Omar et al., 1987;Vermeesch et al., 2009). Here, "rock uplift" is used to interpret the vertical movement of rocks during a specific cooling/exhumation event, and "surface uplift" is equal to total rock uplift minus erosion (Lisker et al., 2009). ...
... The obtained thermochronologic data yields no AFT age resetting, and the distribution of HCTLs supports uplift from the AFT PAZ (110°C-60°C), while the t-T models restrict this temperature to ca. 60°C ( Figure 5). The recent geothermal gradient is 25°C (Morgan et al., 1985;Feinstein et al., 1996), and its doubling is expected during the rifting active period (Omar et al., 1989;Kohn et al., 1992), which suggests rift flank uplift at the studied area from depths of ca. 1.2 ± 0.4 km. ...
The Neoproterozoic Arabian-Nubian Shield (ANS) in the Eastern Desert of Egypt encloses the regional thermal-tectonic history from its development till the Oligo-Miocene when the Red Sea rift system was initiated. The application of multi-thermochronometry techniques has proven to be a successful approach to revealing the influence and extent of each regional tectonic event and the recreation of the tectono-thermal development of the studied region through time. Therefore, characteristic samples from the ANS different rock suits of the Gabal Loman area at the western flank of the northern Red Sea were collected. The Zircon fission-track data reveals the Carboniferous cooling ages, while the apatite fission-track cooling ages present two differential time spans of Cretaceous and Eocene-Oligocene. The time-temperature history modeling is integrated with fission-track data to reveal three differentiated cooling events developed in response to regional tectonic events: 1) the Hercynian (Variscan) tectonic event that influenced the ANS vicinity with rock uplifts of ca. 4 km through the Devonian-Carboniferous time, 2) the Gondwana disintegration event which influenced the region with differential rock exhumations, and 3) the northern Red Sea rifting through the Oligo-Miocene which caused a regional ca. 1 km of rift flanks exhumation. This modest rift flank uplift suggests a passive rift of the northern Red Sea rifting in the region of study.
... The eastern edge of the crystalline Sinai massif, on the other hand, has the highest heat flow values, exceeding 90 mW/m 2 (Fig. 5). The heat flow along the western margin of the Gulf of Suez was predicted to be 60-80 mW/m 2 and may reach to 100 mW/m 2 , assuming a thermal conductivity of 2.3 W/mK as a minimum value (Morgan et al., 1985;Boulos, 1990). These values must be doubled due to the presence of a thick evaporates layer with high conductivity in the Gulf of Suez portion. ...
... In the Hammam Faraun hot spring, a large temperature gradient was observed (48 mKm −1 ). Locations of the boreholes where temperature logs were measured by Morgan et al. (1985). The table on the right refers to the depth and temperature gradient for each well High heat flow values of up to 175 mW/m 2 , roughly three times average, have been reported in eastern Egypt, according to Morgan and Swanberg (1979), and the heat flow appears to increase toward the Red Sea coast. ...
Egypt seeks to diversify in exploiting new energy resources that can be obtained at competitive rates in order to continue sustainable development processes. Whereas due to limited water and fossil fuel supplies, as well as growing environmental concerns, Egypt’s demand for clean and renewable alternative energy is increasing. Unexploited geothermal resources may contribute with additional forms of renewable energy to meet domestic energy requirements while also allowing electricity exports to increase. In this chapter, we review the state-of-the-art geothermal potentialities and resources in Egypt as well as current geothermal energy uses and future developments. Generally, almost all prior studies agree that the highest geothermal prospective sites are located in the eastern part of Egypt near the Red Sea, the Gulfs of Suez and Aqaba. However, some areas in the Nile Delta and Western Desert have normal to low-temperature geothermal resources that can be utilized in many direct applications.KeywordsRenewable energyGeothermal potentialityGeothermal resourcesRed SeaGulf of Suez
... The temperature, thermal conductivity, heat flow and heat capacity profiles versus depth of Hammam Faraun field are presented in Figure 2 (Lashin A. 2015). However, the formation temperature and thermal conductivity versus depth of Ras Budran field are shown in Figure 3 (Morgan et al., 1985). The analysis of the temperature profiles assigns medium geothermal gradient for the two fields (geothermal gradient of 45°C/km for Hammam Faraun field and 32°C/km Ras Budran field). ...
... Formation temperature and thermal conductivity of Ras Budran field (AfterMorgan et al., 1985). ...
Egypt depends on oil and gas for electricity generation (about 90%). The remaining small percentage comes from the hydropower of the High Dam (about 8%), the wind energy, and the solar cells. Therefore, it is important to adjust this unbalanced energy mix in Egypt. The continuous scientific research is the best way to try to solve this problem by studying the feasibility of using available renewable energy sources. Among these energies is the geothermal potential energy. However, it has not been exploited as a renewable source for power generation in Egypt yet. This study aims to determine the locations of reservoirs, which have high temperature gradient that can be suitable for implementing geothermal energy projects in Egypt. The study is executed using data of deep wells that are located in different regions to investigate the technical possibility of utilizing subsurface reservoirs for geothermal power generation pilot projects. The results indicate that the best reservoirs with high temperature gradient are located in the Western Desert and around the Gulf of Suez especially at Hammam Faraun and Ras Budran fields. These two locations have recorded reservoir temperatures of 100°C and 146°C at depths of 1150 m and 3800 m, respectively. Simulation studies are conducted, and the results show that these formations can feed a power plant by 21,000 bbl/day of hot water at well head temperature ranging between 94°C and 105°C from a pilot project of two producers and one injector in Ras Budran (or four producers and two injectors in Hammam Faraun). Each pilot will be able to generate annual amount of electricity equal to 4,977 MWh through a binary cycle power plant. This proposed pilot project can be scaled up to generate additional electricity. Accordingly, application of this unfunded research recommendations can save hard currency and increase the national income.
... Nevertheless, few attempts have been made to interpret the Red Sea coastal zone thermal anomaly. For example, Morgan et al. (1985) studied the basic mechanisms by which the high observed heat flow in the Red Sea coastal zone could be produced. Morgan and Swanberg (1979) indicated that there is little or no deep circulation of the surface water which means dry geothermal resources rather Responsible Editor: Domenico M. Doronzo than fluid-dominated systems from the eastern desert of Egypt. ...
... These properties are displayed in Table 2. The values of physical rock properties are assumed in the present study according to the previous studies carried by Morgan et al. (1983Morgan et al. ( , 1985, Meneisy (1990), and El-Nouby and Ahmed (2007). The estimation of fracture porosity and permeability values as absolute values is difficult. ...
The study area is located in the Quseir–Safaga area of the Egyptian Red Sea Coast. This location considered one of the most promising areas for touristic villages depending on groundwater domestic uses as well as geothermal energy. The geothermal energy is considered one of the promising sources in the studied area. Nevertheless, few attempts have been carried out to evaluate the geothermal setting of the area. The present study aims to throw more light on studying the predominant structures in the area and their relation with geothermal manifestations, as well as defining the hydrothermal system type at the study area. Achieving this goal is dependent on using aeromagnetic data in the form of reduced to northern Pole (RTP) anomalies. These data were subjected to different techniques of processing and interpretation through both qualitative and quantitative analyses. Two-dimensional (2D) modeling of aeromagnetic data has been used to simulate the subsurface structure configuration along some selected profiles trending in NW-SE and E-W directions. In addition, a conceptual model of the hydrothermal system was built based on geophysical results of the aeromagnetic data analysis and processed numerically to obtain a 2D hydrothermal model that contains all simplifications and assumptions made on the conceptual model. The HYDROTHERM Interactive (HTI) program version 3 was used for two-dimensional simulation in the study area to study the temperature and pressure distributions beneath the study area. The results of the study showed that the depth to basement from the ground surface ranges from 20 to 1200 m. The hydrothermal simulation in the area indicated that the origin of thermal water is due to high heat flow and deep groundwater circulation controlled by structures in the subsurface reservoir. Under the thermal water, the water speeds up and flows through the fractures and faults. In general, the high heat flow in the Eastern Desert is associated with shallow basement depths. Thus, the modeled hydrothermal system is considered a dynamic type.
... We searched for a possible thermal anomaly, caused by past hotspot heating. We performed a heat-flow study on the Arabian plate, using temperature data from 399 boreholes, complemented by 123 other heat-flow data (Morgan et al., 1985;Rolandone et al., 2013) (Fig. 5.a). We estimated the heat-flow for each borehole, according to Fourier's law (Fig. 5.a). ...
... (a.) Map of Arabian plate heat-flow. Diamonds -heat-flow data fromMorgan et al. (1985) andRolandone et al. (2013). Dots -heat-flow data estimated from borehole data (TOTAL database). ...
Rifts are often associated with ancient traces of hotspots, which are supposed to participate to the weakening of the lithosphere. We investigated the expected past trajectories followed by three hotspots (Afar, East-Africa and Lake-Victoria) located around the Red Sea. We used a hotspot reference frame to compute their location with respect to time, which is then compared to mantle tomography interpretations and geological features. Their tracks are frequently situated under continental crust, which is known to strongly filter plume activity. We looked for surface markers of their putative ancient existence, such as volcanism typology, doming, and heat-flow data from petroleum wells. Surface activity of the East-Africa hotspot is supported at 110 Ma, 90 Ma and 30 Ma by uplift, volcanic activity and rare gas isotopic signatures, reminiscent of a deep plume origin. The analysis of heat-flow data from petroleum wells under the Arabian plate shows a thermal anomaly that may correspond to the past impact of the Afar hotspot. According to derived hotspot trajectories, the Afar hotspot, situated (at 32 Ma) 1000 km north-east of the Ethiopian–Yemen traps, was probably too far away to be accountable for them. The trigger of the flood basalts would likely be linked to the East-Africa hotspot. The Lake-Victoria hotspot activity appears to have been more recent, attested only by Cenozoic volcanism in an uplifted area. Structural and thermal weakening of the lithosphere may have played a major role in the location of the rift systems. The Gulf of Aden is located on inherited Mesozoic extensional basins between two weak zones, the extremity of the Carlsberg Ridge and the present Afar triangle, previously impacted by the East-Africa hotspot. The Red Sea may have opened in the context of extension linked to Neo-Tethys slab-pull, along the track followed by the East Africa hotspot, suggesting an inherited thermal weakening.
... 18.9 (3) 18.8 (5) 19.1 (2) 16.7 (1) 12 Table 1 Existing temperature gradient and depth data from boreholes, especially drilled regional temperature gradient boreholes, in Egypt (from the work by Morgan et al. (1983Morgan et al. ( , 1985). * Numbers refer to numbers in Fig. 4. Values in parentheses after gradients are the numbers of boreholes used in the site gradient calculation. ...
... Temperature measurements made by Morgan et al. (1985) in the study area show that the temperature in the Hammam Faraun area increases with depth by 48 mKm -1 . From previous geological, geochemical, and geophysical information, we try to construct an initial conceptual model for the Hammam Faraun hot spring (Fig. 10). ...
Although Egypt is not characterized by abundant Cenozoic igneous activity, its location in the northeastern corner of the African plate suggests that it may possess geothermal resources, especially along its eastern margin. The Eastern Desert of Egypt characterizes by some geothermal potential fields particularly adjacent to the Red Sea. Although the western part of Egypt (Western Desert) has low regional temperature gradients, there are many wells with deep artesian aquifers which represent a low-temperature geothermal resource (35-40°C). In addition, the eastern shore of the Gulf of Suez consists of the hottest springs, including Ain Sokhna, Ayun Musa, Ain Hammam Faraun and Hammam Musa. These areas along both shores of the Gulf of Suez are the most promising for geothermal development. Many geothermal explorations were carried out in Egypt using geophysical and geochemical techniques. Recently obtained data indicates a temperature of 120°C or higher may be found in the reservoir located adjacent to the Gulf of Suez and Red Sea coastal zone. A conceptual model was constructed for the Hammam Faraun hot spring on the eastern side of the Gulf of Suez, which is the hottest spring in Egypt. The model shows the heat source of the hot spring is probably derived from high terrestrial heat flow and deep fluid circulation controlled by faults associated with the opening of the Red Sea and Gulf of Suez rifts.
... The cooling and exhumation rates as well as the rock uplift (vertical rock uplift corresponding to a single event) were calculated from the t-T modelling, assuming an average geothermal gradient (30 (10) °C/km) ( Table 6 -4). Considering the recent geothermal gradient is ~20 ºC/km (Morgan et al., 1985). It is expected to be doubled in active tectonic conditions in the Gulf of Suez (Moore et al., 1986;Omar et al., 1987;Vermeesch et al., 2009). ...
... The exhumation rates were calculated from the cooling rates, a geothermal gradients of 20, 30 and 40 °C/km and surface temperature which was calculated from the recent average 20 °C. The recent geothermal gradient in near area is 20 °C/km (Morgan et al., 1985). Hereafter, the cooling pattern changed to rapid cooling and exhumation rates of ~2. ...
The African lithospheric continent has an extended history over 3.8 Ga and is tectonically active since more than 2.9 Ga. Ever since the topography of that continent was changing under influences of a series of endogenic (tectonic) and exogenic (surface) processes. Generally the earth’s topography has major influences on the planet, examples include but are not limited to species distribution, forest succession, erosion, sedimentation, fluvial systems and climate. The topographic changes are accompanied by rock exhumations in either way of endogenic forces or as response to exogenic processes. These exhumation events could be traced by low temperature thermochronology (LTT) techniques. The LTT techniques date the rock passing through a certain isotherm (closure temperature) and are used to quantify the cooling rates. The closure temperature is function of the applied LTT technique and mineral type. Combining these cooling ages and LTT data with the time-temperature (t-T) modelling enables visualizing and quantifying the rock movement through the upper crust. Therefore, these combinations were used to compare and reconstruct the topographic changes in key areas dominated by various geologic environments as response to different magnitudes from multiple landscaping processes in the African continent. Furthermore, the ability of LTT to answer difficult questions related to landscaping processes (e.g., landslide detection and quantifying and the endogenic-exogenic processes relationship) was also tested.
Comparing and reconstructing rift flanks uplifted areas (the Albertine Rift; the Rwenzori Mountains and the Gulf of Suez; the Samra Mountain area) on an old craton revealed a relatively long cycle of life. The non-uniform uplift through fault-bounded blocks was the dominant mechanism of response for all the induced far-field continental scale tectonics and surface processes. Only a uniform uplift was demonstrative during the rifting event. The thermochronological record of the Samra area has started earlier with the East African Orogeny (EAO) plutonism and accretion. Afterwards, both areas (the Rwenzoris and the Samra) were affected by the post orogenic erosional event. Shortly after, each area of them was affected differentially by a series of far-field tectonic events. Then, the rift started to activate affecting the whole areas with corresponding uplift. While the Gulf of Suez was nearly deactivated by the movement along the Dead Sea transform fault at mid-Miocene. The movement along
the footwall of Bwamba fault caused additional
uplift to the Rwenzoris at the Pliocene.
On the other hand, comparing and reconstructing
volcanic islands (Fuerteventura
and La Gomera; Canary Islands) on passive
margin revealed a relatively short cycle
of life. That cycle started by emerging, followed
by formation of the shield stage with
adding a huge amount of magmatic materials
forming a highly topographic island
(Fuerteventura; ~20 Ma, La Gomera; ~10
Ma). Afterwards, the topography destruction
starts with landsliding (Fuerteventura;
≤20 Ma, La Gomera; ~7 Ma) when suitable
topographic and climatic conditions, among
others, were dominated. Then the volcanic
island experience other cycle, starting with
constructing high topography by feeding with
new magmatic materials till the hot spot related
magmatic activities transfer to other
regions. That activity shift was recorded by
a lateral movement of the Canary plume
materials beneath northwest Africa to west
the Mediterranean Sea produced a track
of intraplate volcanism through its course.
Furthermore, LTT techniques were
able to detect, differentiate, and quantify
different landscaping events (including
landslides) with various magnitudes
in different geologic environments.
- In rifted regions; the Rwenzori Mountains
have experienced 4 rapid cooling/exhumation
events. 1) the Silurian-Devonian (420-
390 Ma) event associated with ~3.5 (1.5) km
of rock uplift as response to the post Pan-African
orogeny deep erosional event. 2) The
Triassic (240-220 Ma) event that caused ~3.0
km of rock uplift associated with rapid cooling
and a major erosional event at the end of the
Karoo sedimentary regime. 3) The Eocene-
Miocene (52-10 Ma) event resulted in an average
rock uplift of ~3.0 (0.2) km, the Early
Eocene tectonic events were associated
with India drifting afterwards the Eastern Rift
activity was started. 4) The Pliocene-Pleistocene
event (3-2.5 Ma) caused ~≤2.0 km of
rock uplift along the footwall of Bwamba fault.
The last two exhumation events with
~5 km of corresponding rock uplift produced
the exceptionally high Rwenzori
Mountains in the EARS extensional regime
as a rift flank within two stages. The
latter movement caused the tilt uplifting
in the western flank of the mountains.
While, the Samra Mountain area has
experienced 5 rapid cooling/exhumation
events. 1) The Neoproterozoic (775-640 Ma)
event caused ~5.8 (0.1) km of rock uplift as
a response to the accretion and plutonism
during the EAO. 2) The Cambrian-Devonian
(507-457 Ma) event causing ~5.6 (0.2) km of rock uplift as response to the post-EAO erosional event. 3) The Carboniferous-Permian (390-230 Ma) event resulted in ~4.2 (1.6) km of rock uplift as response to the Hercynian tectonic event. 4) The Jurassic-Cretaceous (170-70 Ma) event resulted in ~2.9 (0.5) km of rock uplift as a response to the Gondwana breakup. 5) The Oligocene-Miocene (27-22 Ma) event causing rock uplift of ~1.3 (0.3) km as response to the rift initiation. Additional reheating event was reported in the time span extending between the uplift associated with the Gulf of Suez and the prior cooling event causing an average subsidence of ~0.6 (0.3) km.
- The Albertine rift flanks uplift is double the Gulf of Suez related flanks uplift which suggests an additional heat component during the Albertine rift formation. That heat component resulted from being the corresponding mantle plume directly beneath the EARS and more than 2000 Km away from the Gulf of Suez (Afar plume).
- In volcanic islands; Fuerteventura Island has experienced two rapid cooling/exhumation events; one has started ~20 Ma with ~2.7 (0.5) km of corresponding rock uplift that caused the onset of the Fuerteventura landslide. The other has been initiated ~7 Ma with ~2.3 (0.2) km of corresponding rock uplift forming the doming stage on the western part of Fuerteventura ~5 Ma. Finally, these domes were eroded to nowadays surfaces. La Gomera Island also has experienced two rapid cooling/exhumation events; the first event has started between ~10 and 7 Ma with corresponding ~2.7 (0.2) km of rock uplift causing the onset of the La Gomera landslide. The second rapid cooling event occurred by ~4 Ma resulting in ~2 km of rock uplift. Finally, this topography was eroded to reduce elevation to nowadays surfaces
... The thermomechanics process controlling the tectonic evolution of the Gulf of Suez is still enigmatic. However, the anomalously large size of the rift flank for the amount of extension at the Gulf of Suez suggests a thermal uplift component (Stickler, 1985;Feinstein et al., 1996) Girdler and Evans, 1977Feinstein et al.1996Morgan et al. 1985 ...
... Temperature-depth plot for Ayun Musa BH-1 well (Modified afterMorgan et al., 1985). ...
Geothermal Reconnaissance Study for Sinai Peninsula, Egypt
... A very good example of the thermal waters, which come from deep wells, are those located in the Western Desert (Kharga and Baharyia oases) (Lashin, 2013). (Morgan, 1983;1985). ...
... The geothermal activity of Egypt has received the attention of many researches from the mid of 1970 till now (Al Ramly, 1969;Issar et al. 1971;Morgan and Swanberg, 1979;Morgan et al. 1977Morgan et al. , 1983Morgan et al. and 1985Swanberg et al. 1983;Riad et al. 1989;Boulus, 1989 and1990;Zaghloul et al. 1995;Feinstein et al. 1996;Hosney and Dahroug 1999;Hosney, 2000;Hosney and Morgan, 2000;and Abdelzaher and Ehara, 2009;Lashin and Al Arifi, 2010;Abdelzaher et al. 2011 andLashin, 2013). The actual work was done by . ...
Egypt present energy strategy aims at increasing the share of renewable energy to 20 percent of Egypt’s energy mix by 2020. Egypt demand for electricity is growing rapidly (an annual rate of increase from 1,500 to 2,000MW) and with time an alternative sources of power supply become more urgent. Some aspects of utilization of renewable energy is already made from wind and solar resources. Despite scares direct utilization, the geothermal potential "till now" is not included in the renewable energy map of Egypt.
Majority of the geothermal resources of Egypt are mainly located along the Gulf of Suez and Red Sea with a surface temperature range of 40 - 76oC. Some other spots are found in the Western Desert of Egypt, close to the Oasis (Baharia and Dakhla). Regarding the Gulf of Suez, the previous studies and analyses of temperature profiles, logging data from deep oil wells and geo-thermometric parameters referred to spots of good geothermal potentials, i.e. good geothermal gradient (45 oC /Km) and heat flow (120 mW/m2). The fracture and faulting systems associated with the tectonic activity of the Red Sea and Gulf of Suez provide a continuous supply of heat energy to the deep circulated fluids. Geothermal assessment and reserve estimation studies assigned good figures of geothermal power energy that can be used for installing binary power plants. Hammam Faraun geothermal spring is the best location for such investment where an estimate of geothermal reserve of 12.4 MWt is already made. Away from Gulf of Suez, some other thermal springs (up to 35 oC) enriched with sulphur are located 25 km south of Cairo close to Helwan city. In the Western Desert of Egypt, hot water is produced from some deep artesian wells. the temperature range is in the range from 35-45 oC. These resources can be used for low and direct geothermal applications (district heating "especially in winter", swimming pools, medical therapy, green houses, etc.
A detailed field mapping, geochemical and geophysical exploratory work is needed in future to better define the potentiality of the geothermal resources in Egypt.
... Temperature measurements including thermal gradient/heat flow studies remain the most direct and reliable methods for exploring regional geothermal phenomena. Multiparameter methods such as geophysical, geochemical, and remote sensing techniques can also be used for these investigations, but geothermal measured temperatures are the ultimate approach [7][8][9][10][11][12][13]. Based on these methods, most of Egypt's geothermal resources Remote Sens. 2023, 15, 5094 3 of 19 are located along the Gulf of Suez and the eastern side of the Red Sea. ...
Environmental degradation is reducing crop productivity in many regions of Egypt. Moreover, unsustainable surface water drainage contributes to salinized soil conditions, which negatively impact crops. Egypt is seeking solutions to mitigate the problem of surface water drawdown and its consequences by exploring renewable and sustainable sources of energy. Geothermal energy and the desalination of saline water represent the only solutions to overcoming the fresh water shortage in agricultural industry and to providing sustainable fresh water and electricity to villages and the Bedouin livelihood. In Egypt, the Siwa Oasis contains a cluster of thermal springs, making the area an ideal location for geothermal exploration. Some of these thermal springs are characterized by high surface temperatures reaching 20 °C to 40 °C, and the bottom-hole temperatures (BHT) range from 21 °C to 121.7 °C. Pre-Cambrian basement rocks are usually more than 440 m deep, ranging from 440 m to 4724.4 m deep. It is this feature that makes the Siwa Oasis locality sufficient for geothermal power production and industrial processes. This study utilized both the Horner and the Gulf of Mexico correction methods to determine the formation temperatures from BHT data acquired from 27 deep oil wells. The present study revealed a geothermal gradient ranging from 18 to 42 °C/km, a heat flux of 24.7–111.3 mW/m2, and a thermal conductivity of 1.3–2.65 W/m/k. The derived geothermal, geophysical, and geological layers were combined together with space data and the topographic layer to map relevant physiographic variables including land surface elevation, depth to basement, lineament density, land surface temperature, and geologic rock units. The ten produced variables were integrated in GIS to model the geothermal potential map (GTP) for the Siwa Oasis region. According to the model, both the eastern side and north and northeastern portions of the study region contain high and very high geothermal potential energy. Combining bottom-hole temperature measurements with satellite remote sensing and geospatial analysis can considerably enhance geothermal prospecting in Egypt and other East African areas that have geologically and tectonically similar settings. In addition to identifying sustainable resources needed for food production, this research has implications for renewable energy resources as well.
... Temperature measurements including thermal gradient/heat flow studies remain the most direct and reliable methods for exploring regional geothermal phenomena. Multiparameter methods such as geophysical, geochemical, and remote sensing techniques can also be used for these investigations, but geothermal measured temperatures are the ultimate approach [7][8][9][10][11][12][13]. Based on these methods, most of Egypt's geothermal resources Remote Sens. 2023, 15, 5094 3 of 19 are located along the Gulf of Suez and the eastern side of the Red Sea. ...
Environmental degradation is reducing crop productivity in many regions of Egypt. Moreover, unsustainable surface water drainage contributes to salinized soil conditions, which negatively impact crops. Egypt is seeking solutions to mitigate the problem of surface water drawdown and its consequences by exploring renewable and sustainable sources of energy. Geothermal energy and the desalination of saline water represent the only solutions to overcoming the fresh water shortage in agricultural industry and to providing sustainable fresh water and electricity to villages and the Bedouin livelihood. In Egypt, the Siwa Oasis contains a cluster of thermal springs, making the area an ideal location for geothermal exploration. Some of these thermal springs are characterized by high surface temperatures reaching 20 °C to 40 °C, and the bottom-hole temperatures (BHT) range from 21 °C to 121.7 °C. Pre-Cambrian basement rocks are usually more than 440 m deep, ranging from 440 m to 4724.4 m deep. It is this feature that makes the Siwa Oasis locality sufficient for geothermal power production and industrial processes. This study utilized both the Horner and the Gulf of Mexico correction methods to determine the formation temperatures from BHT data acquired from 27 deep oil wells. The present study revealed a geothermal gradient ranging from 18 to 42 °C/km, a heat flux of 24.7–111.3 mW/m2, and a thermal conductivity of 1.3–2.65 W/m/k. The derived geothermal, geophysical, and geological layers were combined together with space data and the topographic layer to map relevant physiographic variables including land surface elevation, depth to basement, lineament density, land surface temperature, and geologic rock units. The ten produced variables were integrated in GIS to model the geothermal potential map (GTP) for the Siwa Oasis region. According to the model, both the eastern side and north and northeastern portions of the study region contain high and very high geothermal potential energy. Combining bottom-hole temperature measurements with satellite remote sensing and geospatial analysis can considerably enhance geothermal prospecting in Egypt and other East African areas that have geologically and tectonically similar settings. In addition to identifying sustainable resources needed for food production, this research has implications for renewable energy resources as well.
... °C/m, with a mean value of roughly 31 °C/km, which is similar to the global average near-surface geothermal gradient (0.30 °C/m). Similarly, Egypt's heat flow map was made by gridding and contouring heat flow dataset (Figure 2), which was derived from a combination of thermal conductivity obtained from Morgan et al. (1983Morgan et al. ( , 1985 and temperature gradient values. The computed heat flow map displays a range of values from ~43-104 mW/m 2 , with a mean heat of 73.5 mW/m 2 . ...
This study presents a comprehensive analysis integrated with an efficient GIS national site screening process to create a preliminary geothermal atlas of Egypt, which will support the government and Egypt's private geothermal energy industry sector in selecting the best locations for prospective geothermal power plants. Our preliminary findings indicate that the best prospective geothermal regions are located along the Red Sea and Gulf of Suez coastlines, where the northern extremity of the East Africa Rift (EAR) is situted. The area of El-Gouna (southern part of Gulf of Suez), is identified as the optimal site for further geothermal exploration and development.
... The Arabian-Nubian Shield (ANS) has a crust with a thickness 25-45 km (Al-Damegh et al., 2005;Hansen et al., 2007;Hosny and Nyblade, 2016;Mooney et al., 1985;Sobh et al., 2019;Tang et al., 2016;Yao et al., 2017), which is underlain by lithospheric mantle with a thickness of 50-120 km (Stern and Johnson, 2010). The current heat flow in the Arabian-Nubian shield is 35-70 mWm −2 (Morgan et al., 1985;Rolandone et al., 2013). In the ANS of northeastern Africa (Egypt, Sudan, and Ethiopia), more than 130 ring complexes have been emplaced in the period extending from the final stage of the Pan-African orogeny to the Red Sea rift opening (650-30 Ma; Vail, 1989). ...
We examined an alkaline ring complex in the Eastern Desert of Egypt, Wadi Dib ring complex (WDRC), to understand formation mechanisms of the intimately related ring structure and chemical diversity. The WDRC consists of multiple circular rings of the oldest volcanic units, the middle-stage plutonic unit, and the youngest dike unit, and these units show overlapping whole-rock major element compositions. The compositional variation of the volcanic and plutonic units can be accounted for by a stepwise fractional crystallization starting with trachyte, without significant magma replenishment or crustal contamination. From the margin to the center and oldest to youngest, the plutonic unit consists of an outer ring (syenite), inner rings 1 (quartz-bearing syenite) and 2 (quartz syenite), and a granitic core (syenogranite). The whole-rock chemical composition of the plutonic unit is progressively more fractionated inwards from the outer ring to the granitic core through the inner rings. Syenites from the innermost outer ring show high degree of deformation, which gradually decreases outwards in the outer ring and abruptly decreases inwards in the outermost inner ring 1. The deformed syenites show microstructures suggesting reactive melt transportation. The country rocks neighboring the ring complex and equivalent blocks present in the periphery of the outer ring, the overlying volcanic unit and equivalent blocks present in the inner rings all show microstructures indicative of pyrometamorphism. Spatial variations in the microstructures in the plutonic unit indicate an increase in cooling rate from the outer ring to the granitic core and thus with time. These geological, chemical, and microstructural features of the WDRC suggest that the ring complex represents an evolving roof zone of a subvolcanic magma body located at a depth of a few km. Intimate coupling of growing roof and sidewall mushy boundary layers and later collapse of the roof boundary layer with occasional involvement of the overlying volcanic piles induced segregation of interstitial fractionated melt from the wall boundary layer to the collapse space driven by a pressure gradient induced by the collapse. The ascended fractionated melt started to crystallize to form a roof boundary layer of the next generation by increasing cooling efficiency, which thickened until the next collapse on a smaller horizontal scale inducing melt segregation from the wall boundary layer towards the roof zone. Repetition of the sequence with shallowing and decreasing the horizontal scale produced the ring structure and chemical diversity of the WDRC.
... Thermal gradients of 46 • C/km and 76 • C/km are typical for continental and oceanic crusts, respectively. These gradients place the Curie isotherms at depths of around 12 km and 8 km (Morgan et al., 1985;Schutz, 1994). As the cause for the high frequency magnetic anomaly is shallow in origin, most of the geometrical modifications done to the model were on the igneous crust and partly on the upper crust-sedimentary interface. ...
... Isotropic permeabilities were assumed in this work, and rock parameters (i.e., porosity, density, specific heat and thermal conductivity) were utilized as inputs to the model, as indicated in Table 1. The parameter values were assumed based on typical values for the Western Desert and all of Egypt, as gathered from prior research and literature, such as that of El Ramly (1969), Morgan et al. (1985) and El-Nouby et al. (2007). ...
Nonrenewable hydrocarbon energy sources provide the bulk of Egypt’s energy. However, the nation needs to
diversify its energy portfolio and use conventional and renewable energy in tandem to ensure its long-term
economic growth; therefore, harvesting untapped geothermal resources might help Egypt meet its energy
needs in a sustainable and effective manner. The Farafra Oasis is located in the midst of Egypt’s Western Desert
and has been selected as the focal point for sustainable long-term development in the Western Desert.
Using a magnetotelluric (MT) survey, a deep exploration of the Farafra region has been conducted to explore
the underlying geological state and, as a result, explain the origin of several thermal wells around the oasis. None
of the prior studies reached the necessary depths to offer information on the surface of deep igneous rocks, which
may be the source of heat in the study area. Two field excursions were conducted to measure 19 stations along a
line crossing the Farafra Oasis and extending more than 130 km. The MT instrument measured periods greater
than 1000 s to gather low-frequency data with great efficiency.
On the basis of 2D inversion of MT data, a mathematical model of the Farafra region’s geothermal system was
built to visualize and characterize the heat sources underneath the Farafra Oasis. It was shown that the existence
of a high-temperature pluton at considerable depth is the primary cause of the temperature rise in the aquifer
under the Farafra Oasis, as the water mass builds up on top of plutonic rocks and flows upwards via fractures and
faults.
... Moreover, heat flow is associated with arc volcanism, hot lavas, back-arc basins, and continental rifting. The authors have done previous heat flow studies along the Suez and the Red Sea rifts [37][38][39][40][41][42][43]. Figure 1 shows the location map of the study area with the seismicity and heat flow locations. The local sources of heat flow include frictional heating along earthquake faults. ...
On the 16th June, 2020, a moderate earthquake (Mw 5.2) hit the Northern Red Sea region, Egypt, that was felt throughout the Hurghada and Sharm El-Sheikh cities and the surrounding areas without any damages. The thermal anomaly before the earthquakes was widely studied with satellite data, such as NOAA/AVHRR and MODIS. The case study aims to monitor and demonstrate the possibility of any variation of the thermal anomaly of sea surface temperature (SST) before and after the 16th June 2020 earthquake and to correlate the results with the previous heat flow study (deep thermal action). The Daytime/Nighttime (SST) data are retrieved from the OBPG serves as a Distributed Active Archive Center (OB. DAAC). The outputs indicated a thermal anomaly on the June 12th, 2020 a few days before the earthquake, covered a large area around the epicenter 60 km impact area, and reached a high value on the 15th June 2020, one day before the earthquake. For the deep thermal action of the entire crust, the earthquake frequency distributions presumed from the reviewed catalogue indicated that the peak of the seismicity is concentrated close to the center of the rift axis in the Northern Red Sea. The heat flow measurements are increased toward the center of the Red Sea rift and decreased toward both sides, generating some partial melt of the rocks and producing crustal subsidence at the center of the Red Sea rift. These results are compatible with the pattern of the seismic activity and heat flow effect around the epicenter. It could be considered as a short-term precursor of the earthquake.
... Galanis et al. (1986) measured low heat flow near the Red Sea suggesting ( Figure 1) that values north of 30°N are reasonable to include in our analysis. Moreover, off fault heat flow values in southern Israel and measurements taken in the Red Sea and eastern Egypt (Girdler & Evans, 1977;Morgan et al., 1985) indicate that the Red Sea rifting anomaly is not prominent in the region of our analysis ( Figure S1 in Supporting Information S1). ...
The strength of faults was vigorously debated for years, but lately a growing number of studies suggest that faults are weaker than originally suggested. Nonetheless, only a handful of natural faults have been studied in detail, and only one, the San Andreas, is a strike-slip fault. Here, we reanalyze 268 surface heat flow measurements taken in the proximity of the southern Dead Sea Transform fault to evaluate its friction. To account for large terrain relief, and the presence of salt diapirs, we apply 3-D terrain and salt diapir corrections. Based on these corrected heat flow values we estimate that the long-term frictional resistance of the Dead
Sea fault is 0.28 ± 0.17. This low value is similar to friction estimates from the San Andreas fault and several subduction zones.
... After the emplacement in the lower crust 599 ± 30 Ma, the granite cooled through the apatite U-Pb isotherm (ca. 550 °C to 450 °C) to reach depths of 22 ± 3 km at 474 ± 9 Ma (geothermal gradients of 21 °C/km; [109]). Assuming a homogeneous uplifting rate and starting at ca. 550 Ma, this event of uplifting was accompanied by ca. ...
Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is classically used in U-Pb dating to measure U and Pb isotopic concentrations. Recently, it has become frequently used in fission-track (FT) chronometry too. As an advantage, the U-Pb and FT double dating will enable efficiently determining the crystallization ages and the thermo-tectonic history concurrently as samples volume, analytical time, efforts, and cost will be greatly reduced. To demonstrate the validity of this approach, a Younger granite (Ediacaran age) sample from North Eastern Desert (NED), Egypt was analyzed for U-Pb and FT double dating. The integration of multiple geochronologic data yielded a zircon U-Pb crystallization age of 599 ± 30 Ma, after emplacement, the rock cooled /uplifted rapidly to depths of 9–14 km as response to the post-Pan African Orogeny erosional event as indicated by apatite U-Pb age of 474 ± 9 Ma. Afterwards, the area experienced a slow cooling/exhumation for a short period, most-likely as response to denudation effect. During the Devonian, the area was rapidly exhumed to reach depths of 1.5–3 km as response to the Hercynian tectonic event, as indicated by a zircon FT age of 347 ± 16 Ma. Then the studied sample has experienced a relatively long period of thermal stability between the Carboniferous and the Eocene. During the Oligocene-Miocene, the Gulf of Suez opening event affected the area by crustal uplift to its current elevation. This integration of Orogenic and thermo-tectonic information reveals the validity, efficiency, and importance of double dating of U-Pb and FT techniques using LA-ICP-MS methodology.
... Of importance in defining the origin and crustal structure of the RSR is determining both the geothermal gradient (GG) and heat flow (HF) along the RSR. Previous studies using both direct HF measurements and HF values determined from magnetic studies (e.g., Girdler and Evans, 1977;Morgan et al., 1985;Boulos, 1990;Saleh et al., 2013;Saada, 2016;Saada and Kharbish, 2019) have shown that the mean HF value within the RSR (116 mW/m 2 ) is higher than 90% of the mean HF values Saada et al. Marine and Petroleum Geology xxx (xxxx) 105253 Fig. 2. Composite stratigraphic column of the northern and southern RSR (adapted after Bosworth and Burke, 2005;Bosworth, 2015). ...
Global topography, bathymetry, magnetic, and gravity data were analyzed to study the nature of the Red Sea crust to infer its tectonic regime. The Red Sea is a classic example of incipient ocean basin formation after the breakup of a continent. We used spectral analysis of the magnetic and gravity data and two-dimensional (2D) forward modelling of the gravity data to image crustal sources within the Red Sea. The magnetic data were also analyzed to determine the Curie point depth, which was then used to estimate heat flow values within the Red Sea. Profiles of bathymetry, gravity, magnetic, and heat flow data were constructed across the southern, central and northern portions of the Red Sea to determine crustal structural differences between these regions. Residual and regional gravity anomaly maps determined from the spectral analysis and 2D gravity forward models indicate that there is a large amplitude gravity maxima over the main axial trough within the central and southern Red Sea caused by a combination of partially molten material intruding into the crust and the formation of a new oceanic crust. However, the central portion of the Red Sea based on the residual gravity anomaly map is a transition zone where the oceanic crust is discontinuous and is separated by inter-trough zones. In the northern portion of the Red Sea, the discontinuous residual gravity maxima and high frequency magnetic anomalies can be correlated with isolated deeps implying the last stage of the continental rifting and beginning of seafloor spreading.
... This is evidenced by petrophysical analysis of these geothermal reservoirs in some offshore wells (Shawky 2020). Previous studies assigned the high heat flow associated with crustal thinning that accompanied the rifting process and the radiogenic heat produced from basement rocks underneath HF area as sole source of heating (e.g., Morgan et al. 1985;El-Qady et al. 2000;Abdel Zaher et al. 2012). However, an important heat source which has not received adequate attention is the presence of basaltic magma storages at a depth of about 15-20 and 25-30 km bounded at the base of the lithosphere as reported by Shallaly et al. (2013). ...
Geothermal activities are often associated with hydrothermal deposits and hydrothermal features that could aid in geothermal exploration. As a case study, this paper is concerned mainly with the factors controlling the hydrothermal activities and deposits in the Hammam Faraun (HF) area, Gulf of Suez rift, Egypt. In addition to dolomites, hot spring travertine deposits recorded for the first time in this area are emphasized. The proposed conceptual models illustrated that these deposits are confined to the damage zone of the Hammam Faraun fault (HFF). The main factors controlling the hydrothermal activities through time are: syn-rift volcanic activities related to shallow magma chamber bounded to the lithosphere, variable fluid conditions and nature of hydrothermal circulation through HF fault system. At rift initiation, sea water percolated along the CLB fault (a clysmic fault parallel to HFF), reached the Nubian Sandstone and Eocene Carbonate aquifers, mixed with their water, heated and arose along the HFF. The hydrothermal deposits related to fluid circulation at this time are represented by stratabound dolomite. At rift climax, the massive dolostone was formed from coastal lakes mixed water. These dolomitizing lakes occupied the topographically low area at the flank of HF relay ramp. With the beginning of post rifting time, travertine deposits were developed from fluids inside spring lakes during the Pleistocene pluvial period. This sequential development of dolomitization, travertine, and hot fluid flow in HF area would suggest continuity of geothermal activities since the rift initiation until present. Therefore, this study may be considered as a guiding model for further proper evaluation of geothermal energy resources of HF area in particular and geothermal systems in rift basins in general.
... To the east, Egypt borders the Red Sea. This adjacency to the Red Sea Rift, a scientifically classified divergent plate boundary with a spreading center between the African and Arabian plates [13], provides a distinct tectonic setting which positions Egypt to have substantial geothermal resources [14]. The eastern and western coasts of the Gulf of Suez within the northwest Red Sea include a cluster of hot springs with a range of characteristic temperature variations (e.g., Hammam Musa, Hammam Faraun, Sudr, Ayn Musa and Ain Sokhna). ...
The Gulf of Suez area is one of the most favorable regions in Egypt for geothermal exploitation since it hosts an evident cluster of superficial thermal springs. Some of these thermal springs include Hammam Musa, Hammam Faraun, Sudr, Ayn Musa and Ain Sokhna, which are characterized by high temperatures ranging between 35 °C to 86.66 °C. It is this feature that makes the Gulf of Suez locality sufficient for geothermal power production. Corrected bottom hole temperature (BHT) data from 197 oil wells situated onshore and offshore of the Gulf of Suez were utilized for the present research. The results indicated that the study area has a geothermal gradient ranging from 24.9 to 86.66 °C/km, a heat flow ranging from 31 to 127.2 m W k−1, a thermal conductivity of 2.6–3.2 W m−1 k−1, and an amplitude temperature varying from 49.48 °C to 157.8 °C. The derived geothermal and geological layers were used together with the remote sensing thermal infrared and topographic data, to map relevant physiographic variables including surface elevation, fractures density, drainage density, nighttime land surface temperature and major lithological units. The nine produced variables were integrated in GIS to model the geothermal potential map (GTP) for the Gulf of Suez region. The model identifies the northeastern and the southwestern areas as equally two sites for high geothermal potential. Findings of this study demonstrate that integration of well logging and space data with the adopted geospatial techniques is a practical method for geothermal prospecting in similarly geologic and tectonic setting in Egypt and East Africa.
... El Dayel (1988) Exploration and evaluation of geothermal resources of Egypt has received the attention of many researches from the mid of 1970 till now. Extensive geological, geochemical, and geophysical investigations are carried out for the geothermal systems in Egypt through the course of the last decades, including geothermal reserve estimation and cost analysis studies (Morgan and Swanberg, 1979;Morgan et al. 1977Morgan et al. , 1983Morgan et al. and 1985Boulus, 1989a,b and1990;Zaghloul et al. 1995;Feinstein et al. 1996;Hosney and Morgan, 2000;and Abdelzaher and Ehara, 2009;Lashin and Al Arifi, 2010;Abdelzaher et al. 2011and Lashin, 2007, 2013, 2015Chandrasekharam, et al. 2016 andAbdel Zaher et al. 2018). ...
According to the announced Egyptian renewable energy plan for 2035, a sort of 67 GW representing about 45% of total generated electricity, will be added to the grid from PV, wind and other renewable resources. In the near future (end of the year 2022), Egypt intends to supply 20% of generated electricity from renewable sources (wind, solar and Hydro power). Till now the geothermal resources of Egypt are not scheduled, in the future plans of renewable energy, as a potential energy source. The promised geothermal resources of Egypt are mainly located along the Gulf of Suez and the Red Sea and in some locations at the Western Desert of Egypt. The tectonic activity of the Gulf of Suez and the whole province of the Red Sea play an important role in controlling the thermal water. Other low enthalpy thermal springs, enriched with sulphur, are recognized away from the Gulf region, near Helwan city. In general the identified geothermal resources of Egypt can be categorized as low to medium enthalpy, however some high enthalpy spots are located in deep water associated with the rift of the Red Sea forming what called 'Red Sea Hot brines'. Although this is the status of the geothermal resources of Egypt, these resources could be utilized for many direct purposes as well as some low scales of power generation. This paper represents a review and update of the geothermal activities of Egypt within the last five years.
... The temperature of the thermal wasters is high, varying from 76°C (Suez springs) to 40°C (West Nile springs). Exploratory boreholes were drilled around these springs and the bottom hole temperatures recorded in these boreholes at 2 km depth is 260°C Table 2. Energy requirement, capital and generation cost and CO2 emissions for different desalination technologies (adapted from Ghaffour et al. 2014a, Gude, Nirmalakhandan, and Deng 2010Fiorenza, Sharma, and Braccio 2003 Coal Oil Gas Nuclear Solar Wind Geothermal Energy input kWh/m 3 6.09 6.09 6.09 6.09 6.09 6.09 6.09 CO 2 emissions kg/m 3 5. Morgan et al. 1985;Swanberg, Morgan, and Boulos 1983;Zaher et al. 2011;Zaher, Saibi, and Ehara 2012). The geothermal reservoir temperatures calculated using Silica and cation geothermometers vary between 80°C and 112°C. ...
With ever-increasing population and steep declining freshwater supply, the future concern of MENA and Sub-Saharan countries is food security. Egypt is more vulnerable to food security due to the increased water rights being exercised by the countries sharing the Nile River. Assuming that Egypt by 2025 will achieve 1000 m 3 /y per capita consumption of water, with the population growing beyond 109 millions, the water available by 2025 would be around 106 billion m 3 /y. With increasing pressure from the Nile River basin riparian countries, Egypt may not be able to manage with the current 58 billion m 3 of water from the Aswan dam to achieve per capita goal. To maintain the current per capita water consumption of 636 m 3 /y Egypt may need about 1200 desalination plants and 200 × 10 6 kWh electricity is required to operate these plants and the CO 2 emissions due to this process will be around 80-160 million tones. Electricity generated from hydrothermal sources can supply 659 × 10 9 m 3 /year of desalinated water while the EGS can generate 58,400 × 10 9 m 3 /y of desalinated water from the Red Sea. This will help the country to meet the current fresh water deficit of 48 × 10 9 m 3 /y. By the year 2025, the demand for fresh water will be of the order of 106 × 10 9 m 3 /y to maintain 1000 m 3 /y per capita water consumption. Egypt can set an example to MENA and Sub-Saharan countries by using geothermal energy for sustainable development and future water and food security. ARTICLE HISTORY
... In Egypt, There are many hot springs surrounding the coast of the Gulf of Suez accompanying to the tectonic action of the Red Sea area and Gulf of Suez rift (Lashin and Al Arifi, 2010;Lashin, 2013;Lashin and El Din, 2013).Hammam Pharaon is advised the hottest sulfuric hot spring in Egypt with temperature ability to 70ºC, (Morgan et al., 1983;Morgan et al., 1985).Environmental conditions and the nutritional status available in Hammam Pharaonrepresent a selective media toward a particular group of microbial population that are not sufficiently studied. This study aims to study and identify the potential thermophilic bacteria mainly isolated for Hammam Pharaon and screening their potentialities to be used as a source of several thermostable enzymes. ...
... Numerous regional geothermal investigations were conducted in Egypt using thermal gradient/heat flow and groundwater temperature/ chemistry methods as well as geophysical tools [5][6][7][8][9][10][11]. These methods proposed that most of the geothermal resources of Egypt are mainly arranged along its eastern parts at the Gulf of Suez and Red Sea [6]. ...
Siwa Oasis is a part of the greatest northern depression in the Egyptian Western Desert, located just 50km east of the Libyan border. It represents one of the most interesting potential candidates for the development of the Northern Western Desert of Egypt. Temperature data from deep wells in the Western Desert of Egypt indicate low geothermal resources. Here, we present the contribution of airborne gravity and magnetic geophysical data for the preliminary exploration of geothermal potential in Siwa Oasis. To achieve this objective, a 3D inversion of aerogravity data was used to delineate the depths to basement rocks, while spectral analysis of the aeromagnetic data was used to estimate the Curie Point Depth (CPD) and provide geothermal gradient and heat flow maps for the Siwa Oasis. The depth to the Precambrian basement rock is commonly greater than 2km, ranging from 2km to 5km, whereas the CPDs range from 21km to 28km. Our results imply an inverse relationship between these two depths, in which the deeper basement regions are associated with shallow Curie depths. The derived geothermal gradients range from 21 to 27°C/km and the heat-flow values range from 49 to 64mW/m² for the study area.
... (1) depth-dependent extension (Royden & Keen 1980;Hellinger & Sclater 1983;Watts & Thorne 1984;Morgan et al. 1985); (2) lateral heat flow (Steckler 1981;Cochran 1983;Alvarez et al. 1984;Buck et al. 1988); and (3) secondary convection under rift shoulders (Keen 1985;Steckler 1985;Buck 1986). In addition, representing permanent uplift mechanisms, they are driven by: ...
This paper provides an overview of the existing knowledge of transform margins including their dynamic development, kinematic development, structural architecture and thermal regime, together with the factors controlling these. This systematic knowledge is used for describing predictive models of various petroleum system concept elements such as source rock, seal rock and reservoir rock distribution, expulsion timing, trapping style and timing, and migration patterns. The paper then introduces individual contributions to this volume and their focus.
... However, low geothermal gradients (\20°C/km) were observed in certain parts of basins with thick sedimentary cover, such as the Abu Gharadig Basin (which is more than 4 km thick) and the Matruh, Ghazalat, and Shoushan Basins (see locations in Fig. 3). Many authors have correlated the geothermal anomalies with structures in the basement rocks in northern Egypt and the Gulf of Suez (MORGAN et al. 1980(MORGAN et al. , 1985SWANBERG et al. 1983;HOSNEY and MORGAN 2000;HOSNEY 2001;ABDEL ZAHER et al. 2012). Clearly, the correlation between the high geothermal gradients and low-gravity anomalies in certain localities in the northern Western Deserte.g., the Bahariya and Siwa Oases-indicate promising geothermal potential (i.e., geothermal gradients of 30-35°C/km). ...
... kb at 900°C-1100°C. Considering these estimates, the Natash peridotites plot along or close to the continental 90 mW m − 2 geotherm of Pollack and Chapman (1977), well above the continental shield geotherms (Fig. 6) and the present-day surface heat flow in the Arabian-Nubian Shield (35-50 mW m − 2 , Morgan et al., 1985;McGuire and Bohannon, 1989), implying heating of the lithosphere mantle prior its sampling by ascending Natash volcanics at~90 Ma (Ressetar et al., 1981). Given the steep gradient of the positive correlation between estimated equilibrium temperatures and pressures (Fig. 7a) a prolonged upwelling of deep mantle material, resulting in lithosphere thinning prior to eruption of the Natash volcanics, seems unlikely because thermal Heinrich and Besch, 1992;Luhr and Aranda-Gomez, 1997); Lesser Antilles island arc (data from Parkinson et al., 2003); Iraya volcano, in the Luzon arc (data from Arai et al., 2004); Harrat Ash Shamah in north Arabian Shield (N-AS) (data from Nasir and Safarjalani, 2000;Krienitz and Haase, 2011) and Abyssal peridotites (data from Hellebrand et al., 2005;Workman and Hart, 2005, and references therein). ...
Major and trace element compositions were determined for well-preserved diopside relics in highly altered mantle xenoliths from Natash volcanic province, south Eastern Desert of Egypt, to unravel the major magmatic processes that occurred within the lithospheric mantle long time before the Red Sea rift. The diopside shows a limited compositional range as for mg# (0.89–0.92), Al2O3 (3.52–5.60 wt%), andTiO2 (0.15–0.35 wt%), whereas it is characterised by a larger variability as for Na2O (0.23–1.83 wt%) and, in particular the trace elements. The latter identify two main diopside types: 1) CPX-I has low abundances of incompatible elements, spoon-like REE patterns, small negative anomalies in Ti and Zr and a positive anomaly in Sr; and 2) CPX-II has high abundances in incompatible elements, REE patterns with steady enrichment from HREE to LREE patterns and marked negative anomalies in Ti and Zr. The range of REE patterns in the mantle section can be explained by 7–22% batch melting of the primitive mantle followed by varying degrees of trace element chromatographic exchange. CPX-I underwent only small-scale reactive porous flow metasomatism at the percolation front, whereas CPX-II resulted from large-scale rock–melt interaction close to the melt source. Trace element abundances of CPX-II suggest equilibration with carbonatite-like melts that bear close similarities with the carbonatites that enriched the lithosphere in the southern part of the Arabian plate. The similarity of the P-T gradients recorded by the Natash and southern part of Arabian lithospheres, as well as their re-fertilisation by similar, carbonatite-like agents, is consistent with the presence of a mantle plume at the base of the lithosphere after accretion of the Arabian-Nubian Shield in Late Precambrian. The plume material was fossilized due to secular cooling and became part of the lithospheric mantle before the eruption of the Natash volcanic in Late Cretaceous.
... (1) depth-dependent extension (Royden & Keen 1980;Hellinger & Sclater 1983;Watts & Thorne 1984;Morgan et al. 1985); (2) lateral heat flow (Steckler 1981;Cochran 1983;Alvarez et al. 1984;Buck et al. 1988); and (3) secondary convection under rift shoulders (Keen 1985;Steckler 1985;Buck 1986). In addition, representing permanent uplift mechanisms, they are driven by: ...
This paper provides an overview of the existing knowledge of transform margins including their dynamic development, kinematic development, structural architecture and thermal regime, together with the factors controlling these. This systematic knowledge is used for describing predictive models of various petroleum system concept elements such as source rock, seal rock and reservoir rock distribution, expulsion timing, trapping style and timing, and migration patterns. The paper then introduces individual contributions to this volume and their focus.
Supplementary material: Location table and map of specific transform examples, structural elements of the Romanche transform margin and glossary of terms used in this article is available at https://doi.org/10.6084/m9.figshare.c.3276407
... Previous refraction work (Hosney, 1986) (Morgan et al., 1985), in the Gulf of Suez at the latitude of our profiles, it is possible to compute with a simple steady-state model the temperature at the Moho. We assume the following conductivities: Some other mechanisms must be considered to explain this velocity, such as the possible presence of partial melt in the upper mantle or a pyroxenite composition for this 7.5 km/s layer, .-elated to some underplating event. ...
... Many authors had studied the geothermal activity in Egypt with special emphasis on the Gulf of Suez region. The most important of those are the work of; Morgan and Swanberg, (1979), Swanberg et al. (1983), Morgan et al. (1985), Boulus, (1989and 1990), Zaghloul et al. (1995 and Hosney and Morgan (2000). ...
The geothermal potential of Egypt is mainly located around the costal parts of the Gulf of Suez and in some scattered localities in the Western Desert. This study aims to shed light over the geothermal potential of Egypt by applying on the Gulf of Suez which is taken as a case study. The analysis of temperature shows that, the geothermal gradient as a whole is medium to high (22°C /Km-30°C /Km), but tends to be much higher in certain areas such as; Ras Fanar and Hammam Faraun areas (35°C /Km to 44°C /Km). The compiled thermal plots show that, the evaporites and the rock salt lithology attain the highest thermal conductivity (>3.10 W/m/K) and heat flow (>90 mW/M^2) and the lowest specific heat capacity (< 0.30 J/kg/K). Studying of heat generation is conducted using the characteristic radioactive nature of some elements like; 238U, 235U, 232Th, and the isotope of 40K and utilizing the gamma ray and gamma spectrometery logs. It is noticed that, the heat production factor increases in the carbonate lithology (>3.20W/ m3) and is proportional to the shale volume. Many silica and Na-K-Ca geothermometers are used to estimate the subsurface temperature and heat flow. A geothermal reserve study is carried out for Hammam Faraun hot spring (selected as example). The estimated geothermal potential is found to be 12.4 MWt.
... Bore holes specially to measure the geothermal gradient have also been drilled and the computed and measured data are in good agreement ). Based on the geothermal gradient measured from such deep wells and calculated geothermal gradient and heat flow values reported (Morgan et al. 1985), temperature distribution with depth has been estimated (Zaher et al. 2011) and the values reported are 210°C at 2.5 km depth and 250°C at 3.5. These thermal anomalies are associated with geothermal provinces near Ayun Musa, Hammam Faraun and Hammam Musa on the east coast and Ain Sokhna on the west coast of the Gulf of Suez (Fig. 9). ...
The current thermal regime around the red Sea was initiated by a mantle plume beneath Ethiopia, Eretria, Yemen and SW of Saudi Arabia at about 31 Ma before the present. The evolution of the geothermal systems around the Red Sea is coeval to the initial onset of volcanism over the separated land masses (Eritrea, Ethiopia, Djibouti, Yemen, Saudi Arabia and Egypt at 14 Ma. The entire tectono-magmatic activities around the Red Sea gave rise to several geothermal provinces over the continents surrounding the Red Sea, represented by thermal springs and fumaroles at several locations in Eretria, Djibouti, Ethiopia, Yemen and Saudi Arabia. These countries have the potential to develop these resources, like Ethiopia, to mitigate CO2 emissions in countries like Saudi Arabia and to enhance the GDP (gross domestic product) of the economically backward countries. The geothermal resources have the potential to make these countries energy independent in future.
In the present work, the geothermal resources of the Gulf of Suez (GOS) were investigated using category of integrated datasets (i.e., well logs, earthquake events, geochemical and biological indicators). The earthquake data show that the focal depth range of 5‒50 km is strongly consistent with the distribution of geothermal anomalies. The temperature profiles show low-to-regular geothermal regimes in many places, ranging from 17.0‒30.0 oC/Km; meanwhile a higher temperature gradient (>42.30 oC/Km) was recorded in geothermally active areas. The estimated heat generation values from the gamma ray and density logs are as low as 1.50 mW/m3, indicating minor contribution of radioactive decay to the geothermal potentiality. The physicochemical and biological parameters clarified that the thermal water conditions were selective. The subsurface conditions in terms of reservoir temperature and heat flow were determined using geo-thermometers, and found to be 96.33, 81.71 and 85.57°C and 123.86, 102.12 and 107.83 mW/m2 for Hammam Faroun, Hammam Musa and Ain Sukhna, respectively. The geothermal reserve results show that the geothermal potential of GOS can be used for low-scale energy production to partially fill the energy gap and meet the future requirements of Egypt.
Abstract: The northern part of Sinai is studied to detect the structural elements controlling it and evaluate the distribution and the thickness of the sedimentary cover, which has an important role in both crude oil and water explorations. Therefore, gravity and magnetic data of the area were analyzed by different techniques. Besides, a structure tectonic map was established depending on the integration of the available data. The trend analysis technique was applied to gravity and magnetic data to detect major tectonic and structural trends. Fast Fourier Transform is used to calculate the regional and residual components. Moreover, the depth estimation of the basement rocks was carried out by applying a spectral analysis technique along 57 gravity and magnetic profiles. The deduced fault trends indicate the obvious effect of the Syrian Arc and the East-African tectonic trends on the area. The constructed structure map shows alternated uplifted and down faulted striped blocks, trending mainly in the NNE-SSW direction. The depth to the basement rocks ranges between 2 and 8 km. The 2D gravity and magnetic modeling indicates low magnetic susceptibility indicating granitic basement rocks. The area contains promising sites for hydrocarbon accumulation due to its thick sedimentary cover, in addition to alternated uplifted and down faulted blocks.
The Egyptian government tends to rely on renewable energy sources in the framework of sustainable development plans, including the geothermal energy. Therefore, this investigation objective to reveal the distribution of the geothermal energy in term of u-pwelling heat flow over the Egyptian Red Sea district from magnetic data by assessing the depth to the bottom of the magnetic bodies. The spectral analysis method was applied to the magnetic data to determine this bottom. This method demonstrates that the area is characterized by an average Curie depth of 9.5 km. The calculated heat flow of this area (151 mW/m2) goes above the common worldwide heat flow. The consequences establish a general increase of the Curie point depth from 7km, close to the axial trough, to 15km at the western coast. The assessed heat flow varies from 92 to about 196 mW/m2. The examination area has a high geothermal gradient and a high heat flow because of the rifting action of the Red Sea that causes an up-welling heat flow from the upper mantle. The results indicate that the area is suitable for hydrocarbon accumulation as a source of non-renewable energy as well as geothermal energy as a source of renewable energy.
This book aims to provide a comprehensive understanding of rifts and passive margins as a whole. The aim is to synthesize existing information devoted to specific aspects of these most important hydrocarbon habitats. The book assembles this information in one volume, in a manner that permits the knowledge to be used to assess the risks of exploring and operating in these settings and development of systematic and predictive hydrocarbon screening tools.
This synthesis is completed from results of personal, long-term research on rifts and passive margins, numeric validations of various concepts, and extensive tables documenting various factors influencing structural styles, thermal regimes, and petroleum systems, as well as rates of various geologic processes. This book should have value to a broad range of readers, spanning from geology students, trough exploration geologists, to exploration managers exploring for hydrocarbons in analogous settings.
The study focuses on Equatorial Atlantic margins and draws from seismic, well, gravimetric, and magnetic data combined with thermo-mechanical numerical modeling.
Our data and numerical modeling indicates that early drift along strike-slip-originated margins is frequently characterized by up to 10-20o spreading vector adjustments. In combination with the warm, thinned crust of the continental margin, these adjustments control localized transpression.
Our observations indicate that early-drift margin slopes are too steep to hold sedimentary cover, which results in their inability to develop a moderately steep slope undergoing cycles of gravitational instability resulting in cyclic gravity gliding. These slopes either never develop such conditions or gain them at very late development stages.
Our modeling suggests that the future continental margin undergoing strike-slip-controlled break-up experiences warming due to thinning along pull-apart basin systems. Pull-apart basins eventually develop sea-floor spreading ridges. Margins bounded by strike-slip faults located among pull-apart basins with these ridges first undergo cooling. However, spreading ridges laterally leaving the break-up trace eventually pass by these cooling margins, warming them again before the final cooling proceeds. As a result, the structural highs surrounded by several source rock kitchens witness a sequential expulsion onset in different kitchens along the trajectory of leaving spreading ridges.
Abu-Dabbab area is the most active seismic zone in the central Eastern Desert of Egypt, where seismic activities are daily recorded. The reported earthquakes are microearthquakes of local magnitudes (ML < 2.0). A spatial distribution of these microearthquakes shows that the earthquakes of the area follow an ENE–WSW trending pattern, which is nearly perpendicular to the Red Sea Rift. Focal mechanisms of different fault styles were recognized with dominant normal faulting (with a strike-slip component) events characterized by focal depths greater than 7 km and reverse ones of shallower focal depths. Several lines of evidence indicating that the brittle-ductile transition zone underlies the Abu-Dabbab area occurs at a relatively shallow depth (10–12 km) and it is acting as a low-angle normal shear zone (LANF). Field-structural, EMR and seismic data (this study) reveal that the maximum compressive stress (σ1) in the area is perturbed from the regional NW–SE direction to ENE–WSW orientation. This stress rotation is evidently akin to the reactivation of the crustal scale Najd Fault System (NFS), where such reactivation is attributed to the ongoing activity/opening of the Red Sea. Our tectonic model proposes that the continuous activity on the brittle-ductile transition zone including the LANF led to stress localization, which triggering a brittle deformation in the upper crustal-levels and associated shallow dipping thrusts. Such bimodal tectonic model suggests that the deep earthquakes are owing to the tectonic movement on the LANF (transtension), whereas the shallow earthquakes are related to a brittle deformation inside the fault blocks of the upper crust (transpression). Deformation creep along this zone didn’t permit continuous accumulation of strain and hence reduce the possible occurrence of large earthquakes.
Numerical reconstruction of burial, thermal and maturation histories are carried out for eight sedimentary sections along the profile from the Cyrenaica Platform on the eastern coast of the Sirte Basin to the Hun Graben on the western border of the Sirte paleoift. The interval of depths for temperature calculations included the sedimentary. The analysis of variations in the tectonic subsidence of the basin is used to estimate the amplitudes and duration of the events of thermal activation and extension of the lithosphere occurred during evolution of the Sirte Basin. The modeling suggests that thermal activations of the lithosphere in the Albian–Cenomanian and Oligocene–Pleistocene are common for all tectonic structures of the Sirte Basin and the Cyrenaica Platform. A relatively high temperature regime is also typical for modern state of the lithosphere in the Sirte Basin and Cyrenaica Platform. Such a regime is caused mainly by the thermal activation of the lithosphere during the last 10 Ma. The intensity of this activation is highest in the western part of the Basin, where it is accompanied by the highest erosion amplitudes. The analysis of the variations in the basin tectonic subsidence suggests that two intervals of significant extension of the lithosphere in the Upper Cretaceous and Paleocene are common for all areas within the basin. The total amplitude of the crustal extension attains 1.5 in the central part of the Sirte Basin (the Ajdabiya and Maradah troughs and Zelten and Dahra platforms), is equal to 1.3 in the Hameimat and Zallah troughs, and is minimal (1.11–1.17) in the periphery of the basin (within the Hun Graben and Cyrenaica Platform).
Aeromagnetic data of the area between Marsa Alam and Ras Banas were interpreted to estimate the Curie point isotherm, investigate the geothermal gradient and to determine its surface heat flow. Appling spectral analysis and 2-D inverse modelling techniques to aeromagnetic anomalies has provided equitable promising geological results, useful to further geothermal exploration. Spectral analysis indicates that, the area is underlined by an average Curie-point depth of about 10.58 km. This implies an average thermal heat flow (137 mW/m2) greater than the average heat flow of the Red Sea margins (116 mW/m2). The investigated area was divided into three subregions and the average depth to centroid was estimated for each subregion. 2-D inverse modelling technique indicated that the magnetic sources can be interpreted by a set of dykes dipping to the NE and SW. The integration of radially power spectrum and 2-D inverse modelling was used to estimating the depths to the bottom of these magnetic bodies (equivalent to the Curie-point depth). It indicated a general decrease from 24 to 10 km from west to east toward the Red Sea rifting zone. The calculated surface heat flow increases from 55 mW/m2 to >150 mW/m2 in the same direction. Consequently, the offshore area between Ras Banas and Marsa Alam is a promising area for further exploration of geothermal resources.
The main petroleum-bearing belts are confined to the passive margins of continents -recent and ancient. The recent margins form three global belts which can be considered subtypes differing in time and rifting-spreading stages: Indooceanic-Atlantic, Circum-Arctic, and Mediterranean-Persian. Sedimentary basins of the three subtypes are characterized by a high rate of sedimentation, up to 5-10 cm/ka, but differ in recent thermal regime. One subtype has an increased thermal regime with a depth of 100°C isotherm of 2-2.5 km in separate basins. The other two subtypes are characterized by a different thermal regime, with a 100°C isotherm established at depths of 5-7.5 km. In the case of ancient passive margins, large fields are connected with reef massifs. The post-rifting stage of these belts can be finished by thrusting near orogen and accompanied by formation of molasse foredeeps and multilayer nappe structures. The second type of petroleum belts is confined to active margins, mainly to the Circum-Pacific belt and Western Mediterranean region. Associated with different-age zones of subduction, the basins of the Caspian-Black Sea region can be distinguished as a specific subtype. Subsidence at the last stage is accompanied by an avalanche rate of sedimentation, up to 30 cm/ka. The increased thermal regime (except for the basins of the Caspian-Black Sea subtype) with a 100°C isotherm at depths of 1.5 to 2.5 km contributed to quick maturation of organic matter and the most complete realization of petroleum potential. The third is intraplatformal type of petroleum-bearing belts associated with continental platforms. It is subdivided into subtypes - rifting and epirifting. In the first case, thermal regime is rather high, with the depth of 100°C isotherm ranging from 1.5 to 0.5 km; in the second case it is low with the depth of 100°C isotherm of about 5 km. The fourth type includes basins of intermontane troughs of orogens. The basins of this type are rather small but with thick sediments and high sedimentation rate of 3-6 cm/ka at the Cenozoic stage. The thermal regime is characterized by the depth of 100°C isotherm of to 5 km in intermontane basins of young orogens and to 1.5-2.5 km in rejuvenated orogens. The sedimentary fill of active-margin basins and intraplatformal and intermontane troughs of young orogens is subject to tangential stress caused by collision of lithospheric plates and is characterized, especially along the periphery, by fold-thrust deformation, often with decollement of sedimentary units off the basement or along the plastic horizons in the cover. To estimate petroleum potential in each type of basins, it is necessary to take into account some endogenic factors: thermal regime, deep-level fluids, lateral stress, rate of sedimentation, etc.
Mid-plate Cenozoic volcanism is widespread in Africa where it is often associated with uplift and faulting, and is almost completely restricted to non-cratonic areas. There is a clear time correlation between the pause at ca. 45 Ma in the African apparent polar wander path and the out-break of volcanism at ca. 35 Ma. Accepting that sub-lithospheric heat input is regionally variable, geophysical modelling indicates that mid-plate volcanism can be almost entirely explained in terms of plate thickness and velocity. Conductive models that determine the thermal disturbances in the lithosphere explicitly in terms of perturbation strength, plate thickness and plate velocity are quantitatively examined. The thinning of the lithosphere predicted by the theoretical models can be accomplished by deep, strong thermal perturbations or by upward migrating perturbations of lesser strenght. The latter is consistent with configurations for the East African-Ethiopian lithothermal systems derived from geophysical and geochemical data.
The chemical composition of formation waters tapped in oil wells and emerging as hot springs along the Suez coast of Sinai was examined. A scheme is proposed for the geochemical evolution of these waters and their relation to the geological history of the area.The thermal regime in the investigated area is characterized by high gradient foci located in the immediate proximity of major faults. Fe—mineralization, dolomitization and concentrations of heavy metals were observed on the eastern shore of the Gulf of Suez.The Suez formation waters have equivalent ionic ratios similar to those of the hot brines found in the three Deeps of the Red Sea (Degens and Ross, 1969). The thermal and mineralization phenomena also show a resemblance to those of the Deeps.
A bstract
Although Egypt is not characterized by abundant Cenozoic igneous activity, its location in the northeastern corner of the African plate suggests that it may possess geothermal resources, especially along its eastern margin. Regional geothermal exploration has been carried out in Egypt using the thermal gradient/heat flow technique and groundwater temperature/chemistry technique. In the thermal gradient/heat flow study, existing oil‐well bottom‐hole temperature data as well as subsurface temperature measurements in existing boreholes were utilized before special thermal gradient holes were drilled. Groundwater temperature and chemistry data were used to extend the geographic range of the direct subsurface thermal measurements. On a very modest budget, a regional thermal high has been discovered along the eastern margin of Egypt, and a local thermal anomaly has been discovered in this zone. Published geological information suggests that the sandstones of the Nubian Formation may be a suitable reservoir for geothermal fluids. The new data indicate that temperatures of 150°C or higher may be found in this reservoir in the Gulf of Suez and Red Sea coastal zone where it lies at a depth of 4 km and deeper.
For thermal considerations, the lithosphere is defined as the outer layer of the Earth in which heat transfer is dominated by conduction. Low density continental crust caps the continental lithosphere preventing its subduction, and thus it has, in general, a long and complex thermal history. The thermal regime in the near surface zone of the continental lithosphere is commonly complex, and is responsible for much of the scatter in shallow heat flow data, the main data set used to examine the thermal structure and evolution of the continental lithosphere. A review of continental heat flow data shows that while heat flow is commonly high in areas of recent tectonic activity, there is no simple relationship between heat flow and age of tectogenesis. Low heat flow values are found in some areas of recent tectonic activity, and high heat flow values are found in some areas of older tectonism. An analysis of the parameters controlling the thermal structure of stable continental lithosphere shows that for the same heat flux into the base of the lithosphere, the main factors controlling temperatures within the lithosphere and surface heat flow are the quantity and distribution of heat producing elements within the lithosphere. In regions of recent tectonic and/or magmatic activity, perturbations in the thermal structure of the lithosphere are a function of the style and intensity of the tectonothermal disturbance. In hot spot and extensional settings, the lithosphere is thinned and its thermal gradient increased. The thermal effects at strike-slip boundaries are generally only of local importance, but can be significant when lithospheres with different thermal structures are juxtaposed. A variety of thermal phenomena are observed and predicted for zones of convergence, including low heat flow associated with subduction, high heat flow associated with magmatic activity, and thermal inversions associated with underthrusting. In seventeen continental areas, sufficient data are available to estimate the contribution of upper crustal heat production to the surface heat flow. This contribution is highly variable, and does not appear to correlate with crustal age for Proterozoic and Phanerozoic sites, but appears to be generally lower and less variable in Archean sites. In contrast, the component of heat flow from below the upper heat producing layer, the reduced heat flow, is relatively uniform, around 27 mW m−2 for sites which last experienced tectonism or magmatic activity in pre-Mesozoic times, but is highly variable for younger sites. From the uniform reduced heat flow for pre-Mesozoic sites, the stable thickness of the continental lithosphere is estimated to range from 90 to 220 km, thinner lithosphere being associated with higher heat production in the lithosphere. From this thickness, thermal perturbations in the lithosphere associated with tectonothermal activity are predicted to last no more than a few 100 m.y., a prediction consistent with available reduced heat flow data. Some prolongation of thermal relaxation is expected due to post-tectonic sedimentation and erosion, but these effects appear to be negligible at sites of Early Paleozoic age and older. The scatter in surface heat flow values at these sites is primarily the result of crustal heat production variations and near surface effects. Relatively low and uniform heat flow at Archean sites perhaps reflects relatively low and uniform crustal heat production at these sites.
It is noted that in spite of the flood of new data on continental rifts in the last 15 years, there is little consensus about the basic mechanisms and causes of rifting. The remarkable similarities in rift cross sections (shown in a figure), are considered to suggest that the anomalous lithospheric structure of rifts is more dependent on lithosphere properties than the mode of rifting. It is thought that there is a spectrum of rifting processes for which two fundamental mechanisms can be postulated: an active mechanism, whereby thermal energy is transmitted into the lithosphere from the underlying asthenosphere, and a passive mechanism by which mechanical energy is transmitted laterally through the lithosphere as a consequence of plate interactions at a distance. In order to permit the concept of the two fundamentally different mechanisms to be tested, a tentative classification is proposed that divides rifts into two basic categories: active rifting and passive rifting. Here, the magnitude of active rifting will depend on the rate at which lithosphere moves over the thermal source, with rifts being restricted to stationary or slow-moving plates.
During regional heat flow studies a geothermal anomaly was discovered approximately 2 km from the Red Sea coast at Wadi Ghadir, in the Red Sea Hills of Eastern Egypt. A temperature gradient of 55 C/km was measured in a 150 m drillhole at this location, indicating a heat flow of approximately 175 mw/sqm, approximately four times the regional background heat flow for Egypt. Gravity and magnetic data were collected along Wadi Ghadir, and combined with offshore gravity data, to investigate the source of the thermal anomaly. Magnetic anomalies in the profile do not coincide with the thermal anomaly, but were observed to correlate with outcrops of basic rocks. Other regional heat flow and gravity data indicate that the transition from continental to oceanic type lithosphere occurs close to the Red Sea margin, and that the regional thermal anomaly is possibly related to the formation of the Red Sea.
Morgan, P., 1983. Constraints on rift thermal processes from heat flow and uplift. In: P. Morgan and B.H. Baker (Editors), Processes of Continental Rifting. Tectonophysics, 94: 277–298. Heat is of fundamental importance in the genesis of continental rift zones. Heat flow data are available from the Baikal, Basin and Range (North America), East African, Rhine and Rio Grande rift systems, and most of the data indicate high heat flow, with means of 70–125 mW m⁻², from the grabens in the rift systems. Data from the essentially non-volcanic sections of the East African rift system indicate normal to low heat flow, however. With the exception of the Basin and Range system, and parts of the Rio Grande system, the high heat flow appears to be restricted to the grabens, and is not measured on the broad domal or plateau uplifts associated with the rift systems. The uplifts associated with rifts typically are on the order of 1 to 2 km, with diameters of a few hundred kilometers or more, and the duration of the main phase of uplift is on the order of a few tens of million years, or less. These broad uplifts probably result from thermal changes in the lithosphere-asthenosphere system. Two thermal models of the lithosphere are developed for comparison with the heat flow and uplift data. The first model assumes very slow lithospheric thinning so that the lithosphere remains in a state of quasi-equilibrium during the thinning. The second model assumes that thinning occurs at a rate significantly faster than heat can be conducted into the base of the lithosphere, with thermal relaxation of the lithosphere occurring after the cessation of thinning. Comparison of uplift rates with the model results indicates that for uplift purposes in rift genesis, the lithosphere is in a state between the two models, i.e. partial heating of the lithosphere, or close to the rapid thinning state. Some uplift is predicted to continue after thinning has ceased due to thermal relaxation in the lithosphere. With respect to surface heat flow, however, the rapid thinning model is always predicted to apply, and a surface heat flow anomaly is not predicted to develop until after thinning has stopped. Local (graben) heat flow anomalies are thought to be primarily due to convection of heat into the rift zones by ascending magmas. A regional conducted thermal anomaly is not predicted to develop until after uplift is essentially complete. These predictions are compatible with the available heat flow and uplift data.
Although motion between Arabia and Africa is presently occurring along the entire length of the Red Sea, the morphology and tectonics that result from this motion vary greatly along its length. S of 21oN, the main trough is bisected by a deep axial trough which has formed by sea-floor spreading during the past 4Ma and is associated with large amplitude magnetic anomalies and high heat flow. N of 25oN, an axial trough is not present and the floor of the main trough has an irregular faulted appearance. The magnetic field in the N is characterized by smooth low-amplitude anomalies with few isolated higher amplitude magnetic anomalies commonly associated with gravity anomalies and in many places probably due to intrusions. Between these regions, the axial trough is discontinuous with a series of deeps characterized by large-amplitude magnetic anomalies alternating with shallower intertrough zones which lack magnetic anomalies. It is argued that the different regions represent successive phases in the rifting of a continent and the development of a continental margin. An initial period of diffuse extension by rotational faulting and dike injection over an area perhaps 100km (60mi) wide is followed by concentration of extension at a single axis and the initiation of sea-floor spreading. -from Author
New marine geophysical data are used to describe the structure and history of the Gulf of Aden. Magnetic anomaly data shows seafloor spreading magnetic anomalies of Sheba Ridge from the axial anomaly to anomaly 5 (10 m.y. B.P.) between the Owen fracture zone and 45°E and to anomaly 2' (3 m.y. B.P.) or anomaly 3 (4 m.y. B.P.) west of 45°E. The data does not support the two episodes of seafloor spreading recently proposed. Landward of the seafloor spreading magnetic anomalies is a magnetic quiet zone of uncorrelatable anomalies. The magnetic quiet zone boundary is also a structural boundary effectively marking the edge of Sheba Ridge, with deeper basement lacking a significant topographic gradient found on the landward side. A magnetic quiet zone is found not only where Sheba Ridge splits continental lithosphere but also on East Sheba Ridge where the ridge splits the old oceanic lithosphre of the Owen and Somali basins. There the position occupied by the continental margin within the gulf is marked by nonmagnetic ridge complexes that stretch from the continents to the Owen fracture zone. The magnetic quiet zone boundary is not an isochron in either the Gulf of Aden or the Red Sea, suggesting that significant horizontal motions can occur prior to the initiation of seafloor spreading. The offset on the Dead Sea Rift is used to estimate that from 80 to 160 km of opening, amounting to between 65% and 200% extension of the initial rift valley, occurred in the Gulf of Aden and Red Sea prior to the establishment of a mid-ocean ridge. It is suggested that the development of a new ocean basin occurs in two stages. The first involves diffuse extension over an area perhaps 10 km wide in a rift valley environment without an organized spreading center. This is followed by concentration of the extension at a single axis and the beginning of true seafloor spreading.
Modern conceptions of the structure of the earth's crust and of the distribution of radioactivity lead to an expectation of a greater flow of heat to the surface in mountains than in lowlands. An exceptional opportunity for testing this expectation is provided by the data obtained by the geologists of the Bureau of Reclamation during the construction of the Alva B. Adams Tunnel under Rocky Mountain National Park. This tunnel, 13 miles long, at a mean altitude of 8300 feet, passes under the Continental Divide, more than 12,000 feet above sea level. Some 70 observations of temperature have been reduced with the purpose of finding the flow of heat. Corrections have been applied for the topography on several different hypotheses regarding the physiographic history. The corrected vertical gradient of temperature lies between 24°C/km, on the assumption that the present topography has persisted indefinitely, and 20°C/km, on the assumption that the surface features have been derived from an old-age surface by erosion and by uplift of 7000 feet uniformly distributed over the last million years. If the time of evolution is taken as 4 million years, the corrected gradient is 22°C/km. An uncertainty of about 1°C/km results from lack of reliable data concerning the surface temperature. Thermal conductivity has been measured in the laboratory for 123 samples of rock from the tunnel; these rocks are chiefly granites, gneisses, and schists. The variations of conductivity with rock type and with position along the tunnel are found to be insignificant; the mean value of conductivity is 0.008 cal/cm·sec·deg. The heat flow is then computed as between 1.6 and 1.9 microcal/cm2·sec, with a "best value" of 1.7 microcal/cm2·sec. This is believed to differ significantly from the best values for a "normal" sea-level crust, which fall close to 1.1 microcal/cm2·sec. With conventional assumptions as to thickness and density of the layers of the normal crust, the difference of heat flow may be accounted for in terms of mountain roots having a mean radioactivity of the same order as that of granites or intermediate rocks. The observed heat flow is consistent with the doctrine of mountain roots and with an approximately uniform distribution of radioactivity throughout the "granitic" layer. A few of the other possible interpretations are briefly discussed.
A series of measurements indicates that the thermal conductivity of a rock generally can be estimated adequately for geophysical purposes from simple laboratory measurements on fragments of the rock. The solid-rock conductivity is deduced from a divided-bar measurement of the conductivity of a cylindrical cell containing water-saturated rock fragments. All determinations fall within about ten per cent of conventionally measured solid-rock values for a variety of crystalline and sedimentary rocks with conductivities ranging from about 3 to 14 mcal/cm see øC. Good agreement is found between values determined from drill cuttings and solid core from the same depth in deep boreholes. The method is illustrated by the determination of heat flow in a 3-km-deep borehole near Tehran, Iran (35ø40N latitude, 51ø37'E longitude; elevation, 1710 meters). Contrasting gradients are compensated by conductivity variations determined from drill cuttings. Component heat flows show good agree
Reduced heat flow in the Basin and Range province is characteristically greater by 50% to 100% than that in stable regions; in the hotter subprovinces like the Battle Mountain High, it is greater by 300%. Evidence for distributed tectonic extension and magmatism throughout the province suggests that much of the anomalous heat is transferred from the asthenosphere by convection in the lithosphere, in the solid state by stretching, and in the magmatic state by intrusion. Simple steady-state thermomechanical models of these processes yield relations among reduced heat flow, asthenosphere flux, lithosphere thickness, extension rate, and basalt production by the asthenosphere. Thermal effects in an extending lithosphere lead to decreased estimates of temperature and increased estimates of lithosphere thickness in the Basin and Range province. Moderate extension rates can account for high heat flow in the province without calling on anomalous conductive flux from the asthenosphere. The heat and mass budgets of bimodal volcanic centers suggest that they occur at points where the lithosphere is pulling apart rapidly, drawing up basalt to fill the void. Intrusion can probably facilitate lithosphere extension at low stress levels either by brittle “hydrofracturing” by basaltic dikes or by warming and thinning caused by basaltic underplating. Whether lithosphere extension occurs in the distributed mode or in the plate-tectonic mode might depend largely upon whether the lateral divergence of mass can be supplied by asthenosphere basalt, or whether it must be supplied by the ascent of very viscous ultramafic material which requires wide conduits separated by large distances. For a range of plausible models of distributed extension, the anomalous heat flow increases roughly 1 HFU (10⁻⁶ cal cm⁻²·s⁻¹) for every 1% to 2%/m.y. increase in extension rate; the relation suggests extension rates in the Great Basin consistent with estimates from structural evidence. It also suggests much more rapid local extension in the hotter subprovinces, an inference supported by limited evidence from other sources.
Mathematical problems encountered in the measurement of heat flow at the Earth's surface are reviewed. Most of these problems can be solved by simple solutions of the equation of heat conduction. Reduction of observations in drill holes for horizontal layering are given by the methods of Bullard and Gough. Described briefly are: heat production; the methods of Jeffreys and Bullard, Lees, and Birch for topographic correction; perturbations of the temperature gradient caused by the oscillations of surface temperature; past climatic changes; uplift and erosion; igneous intrusion; groundwater circulation; mine ventilation; the process of drilling and circulation of drilling fluid; and the sudden insertion of temperature probes. The theory of transient methods for determining thermal conductivity and the effect of anisotropic thermal conductivity are also discussed.
There are now twelve heat flow measurements in the Red Sea made with
heat flow probes from survey ships and several sets of temperature
measurements made in deep exploration boreholes. The oceanic
measurements are in water depths ranging from 0.94 to 2.70 km and all
but one of these measurements give values significantly higher than the
world mode of 46 mW m-2 (1.1). They include the world record
high oceanic measurement of more than 3307 mW m-2 (79.0) in
the neighbourhood of the hot brine pools. These measurements show that
the deep axial trough of the Red Sea is associated with high heat flow,
the values being similar to those found in the mid-Indian Ocean rift,
the mid-Atlantic rift and over the crest of the East Pacific rise. It is
of considerable interest to see if there is also high heat flow over the
Red Sea margins and the main purpose of this paper is to examine
temperature data from deep exploration boreholes. The boreholes are
drilled mainly in rock salt, sandstones and shales. A discussion is
given of the thermal conductivities assumed for these rocks. The
boreholes have depths of up to 4 km and in some cases the temperature
measurements enable an estimate to be made of the heat flow. These are
also found to be high. The significance of the high heat flow to ideas
concerning the structure and evolution of the Red Sea is discussed.
The analysis of both temperature data and thermal conductivity material from seven deep oil exploration horeholes in northeast Africa has allowed the calculation of a heat flow value in the Somalian Horn (average58 ± 12mW m−2) and one from the coastal plain of northeast Sudan (average96 ± 19mW m−2). Heat production measurements of granites from the Sudanese basement indicate a substantial depletion in the radiogenic heat producing elements.The heat flow results complement previous measurements from the Gulf of Aden and the Red Sea and are consistent with the geological and geophysical consensus that these two regions are young proto-oceans formed by the mechanisms of spreading lithospheric plates. The heat production evidence suggests that the lithospheric plate beneath the Sudan coastal plain is approximately 30–50 km thick and underlain by a zone of partial or complete melt.
The results of an intensive seismic survey in the Red Sea are presented. Analysis of twenty seismic refraction lines leaves no doubt that much more than just the central trough of the Red Sea is underlain by material with a seismic velocity which is characteristic of oceans. In addition, up to 5 km of what we interpret as evaporites were regularly found. The suggestion that the Red Sea crust could be oceanic in character over the major part of its width is examined in conjunction with magnetic and gravity data. We conclude that there is no evidence against sea floor spreading on a substantial scale in the Miocene. The implications of this in terms of neighbouring features is briefly discussed.
Fission track ages of apatites from volcaniclastic sandstones in several deep drill-holes in southern Victoria, Australia, decrease from 120 Myr near the surface to zero near the bottom of the deepest holes. Track fading occurs between 60 and 125°C, a narrower temperature interval than predicted from laboratory annealing studies, but the 50% track-loss temperature (98°C) is very close to earlier predictions for the estimated heating time in the drill-holes of 10 to 40 Myr.Average track lengths, measured on confined tracks (TINTS, etc.), also decrease with increasing down-hole temperature. Track-length reduction relative to fresh, induced tracks was found in apatites from all depths and even outcrop samples which show no reduction in their fission track ages.
A characteristic pattern of normal faults that we have studied in several regions illustrates successive geometries relating to increasing amounts of extension from 10–50% (Gulf of Suez, Egypt) to 50–100% (Western Gulf of California, Mexico) up to 200% (Southern Basin and Range, USA). Tension fractures formed at an early stage of extension have an essential role. The resulting structure is described as a multiple tilted "packs of cards" model in which rotational deformation within the major blocks is accommodated by normal faulting on previously formed tension fractures, thus defining smaller blocks of second and third generation.
Temperature gradients and thermal conductivities were determined for a number of exploration boreholes in South-west England in order to verify and further delineate the anomalously high heat flow which has been reported. A pattern is emerging of an anomalously high geothermal gradient and heat flow of about 40°C Km−1 and 126 mWm−1 respectively over the Hercynian granite batholith, with normal values adjacent to it. A synthesis of related data indicates that the heat flow anomaly is associated with convection of hydrothermal fluids and although the mechanism is not well understood it may be caused by a combination of above average natural radioactive heat generation coupled with deep, permeable fracture systems within the batholith.
Three heat flow values for south-west England are presented. Two of the sites, Geevor and South Crofty, are operating tin mines on the northern contacts of the Land's End and Carnmenellis Granites, respectively, while the third, Wilsey Down, is a stratigraphical borehole 5 km north of the Bodmin Moor Granite. After applying topographic corrections values of 128·6 mW m-2 (3·07 μ cal cm-2 s-1) for Geevor, 128·9 mW m-2 (3·08 (A cal cm-2 s-1) for South Crofty and 67·3 mW cm-2 (1·61 cal cm-2 s-1) for Wilsey Down, were determined. The value at Wilsey Down is shown to be consistent with that for an environment in which the Hercynian orogeny was the last significant thermal event. An additional heat source term must clearly be involved at Geevor and South Crofty to account for the unusually high values at these sites. Radiogenic heat production has been determined on granites from these sites and in spite of the fact that it is high it does not fully account for the measured heat flow. A compilation of underground temperature measurements made in the nineteenth century suggests that high heat flow is a general feature of the mineralized belt. At least part of this can be explained in terms of hot spring activity recorded widely throughout the area but the ultimate cause remains to be evaluated.
Erosion of continental crust has two effects on surface heat flow: a decrease due to the removal of heat-producing elements, and an increase due to the movement of hot rock towards the surface. In an orogenic belt, where erosion may remove tens of kilometres of material, these effects are important over time-spans comparable with the life of the belt as an elevated region.
An expression is derived which relates surface heat flow to time, heat flow through the deep lithosphere, the distribution of heat sources and the amount and time constant of erosion. The variability of crustal processes permits wide ranges of values for these parameters and geologically reasonable parametral combinations can readily be found which satisfy the surface heat flow observations. These combinations can account for the long time-scale of surface heat flow decay, and the influence of erosion on ‘reduced’ heat flow has important consequences. This approach predicts a relationship between reduced heat flow and age which is close to that observed, and a linear relation between surface heat flow and reduced heat flow similar to that reported by Pollack & Chapman. The intercept on q0—A0 plots (the reduced heat flow) has a physical meaning which changes with time and should not be interpreted as, for example, the heat flux across the Moho.
We conclude that an important part of the observed variation of surface heat flow with age may be explained by the effects of erosion and the variability of crustal processes. In its range of greatest variation surface heat flow mainly reflects these crustal processes and should not be used to infer directly the thermal development of the subcrustal lithosphere.
The ‘magnetic quiet zone’ in the eastern Gulf of Aden is located between the oceanic crust of Sheba Ridge and the continental crust of Arabia and Somalia, and is separated from both by important structural boundaries. The seaward boundary is marked by the end of the seafloor spreading magnetic anomaly sequence and by a basement depth discontinuity. The landward boundary is marked by escarpments made up of a series of normal faults. These escarpments extend from 2–3 km below sea-level to 1500 m above sea-level and are equivalent of the ‘hinge zone’ found at mature continental margins. The magnetic field in the quiet zone is flat in some areas and in others is characterized by anomalies of up to several hundred gammas which are correlatable over distances of up to about 20 km and which appear related to basement topography. The basement lacks the topographic slope characteristic of mid-ocean ridge flanks and is characterized by moderately rough relief. The crustal structure appears quite heterogeneous and where the crustal thicknesses have been determined, they are slightly greater than those of oceanic crust. New heat flow measurements show high values (95.7–123.3 mW m⁻²) in the quiet zone with values decreasing from Sheba Ridge toward the coast.
The unusual structure of the quiet zone and the observations that more opening appears to have occurred between Arabia and Somalia than can be accounted for by the oceanic crust of Sheba Ridge leads to the suggestion that the magnetic quiet zone was generated by diffuse extension of continental crust through a combination of rotational (listric) faulting and dyke injection. This possibility is investigated using both a ‘stretching’ or ‘lithospheric attenuation’ model and a model in which a portion of the extension occurs through dyke injection. It is found that these models can adequately match the observed heat flow and basement depths although very large amounts of extension (β=4–6) are required in the deep seaward portion of the quiet zone. This results in more extension than is compatible with the documented motion between Arabia and Africa.
However, formation of the magnetic quiet zone occurred over a period of 10–15 Myr rather than instantaneously as assumed in the simple models. When the effects of a finite length rifting episode are considered, less extension is required and the observed geophysical data are consistent with a diffuse extension origin for the magnetic quiet zone.
Since 1970, the number of heat flow observations in the Red Sea has increased fivefold. A new heat flow map is presented together with a table of observations. The new data confirm that the whole of the Red Sea is associated with high heat flow. The observations within 5 km distance of the deepest water of the axial trough have a mean of 467 mWm-2 (i.e. about eight times the world mean) and the observations from 50 to 170 km from the axial deep water have a mean of 111 mWm-2 (i.e. about twice the world mean). The heat flow distribution is thus typical of that associated with an active spreading centre. The observations are difficult to assess and interpret in detail because of the complex sedimentary and tectonic environment. The high heat flow extends at least as far as the Red Sea coasts.
Separative motion of tectonic plates that are much thicker than the crust involves important upward movement of hot mantle material between them. It is shown that the loss of heat from this material to the bounding walls is likely to produce structural effects that differ fundamentally from those of purely crustal separation. Notably, the heat loss affects the buoyancy and, through its effect on viscosity, the level of emplacement of the new material. Consequently, support for the crust in the separation zone varies with plate separation rate. This is shown to explain qualitatively the observed variation of axial structures with separation rate. In particular, it yields a mechanism, discussed in detail, that enables oceanic median valleys to be continuously regenerated structures. Buoyancy forces successively elevate the valley floor to form the sides. The model appears consistent with present observations. Some critical tests are proposed.Continental rifting is distinguished by much greater heat transfer to the bounding walls, because separation is very slow (perhaps 0.1–0.5 cm/year) and the plates are probably much thicker (implying hotter source material and initially cooler walls). Crustal support at the axis during the earliest stages of separation is therefore poor, resulting in down-faulted rift valley floors. The heat gained by the plate edges, however, is shown to be of major significance, probably causing the large-scale upwarping of rift margins. Comparisons with the Rhine graben and the rifts of eastern Africa support several evolutionary aspects of this interpretation. Interrupted continental rifting and rifting that is transitional to oceanic conditions are also considered.
Combined radioactivity and heat flow measurements in pluionie rocks at 38 localities in the United States define three heat flow provinces; the eastern United States, the Sierra Nevada, and a zone of high heat flow in the western United States which includes the Basin and Range province. In each of these provinces heat flow (Q) and heat production (A) are related by an equation of the form Q = a + bA. The simplest interpretation of this linear relation is that the radioactivity measured at the surface is constant from the surface to depth b but varies from place to place. Thus the fraction of heat flow from the lower crust and upper mantle, a, remains constant within a heat flow province while the variable upper crustal radioactivity generates the variable heat flow observed at the surface. In the eastern United States b = 7.5 km and a = 0.79 cal/cm2 sec, in the Sierra Nevada b = 10.1 km and a = 0.40 cal/cm2 sec, and in the Basin and Range province b = 9.4 km and a = 1.4 cal/cm2 sec. The line characteristic of the eastern United States may have broad applicability to stable portions of continents and thus be considered the reference curve for normal continental heat flow. The similarity of all the slopes indicates that most local variability of heat flow is due to sources in the uppermost 7–11 km of the earth's crust, and that the contribution from the lower crust and upper mantle is quite uniform over large regions. The intercept values can be used to infer the proportion of heat flow from the mantle and to map provinces with different mantle heat flow. These heat flow provinces correlate closely with surface geological provinces.
Hotspot locations are plotted on a global map of oceanic residual depth anomalies. There is a strong correlation between hotspots and unusually shallow seafloor, indicating that the broad crustal swells surrounding hotspots are the major form of epeirogeny on the ocean floor, besides the normal increase of ocean depth with increasing crustal age. The existing gravity and subsidence data are consistent with the hypothesis that most hotspot swells are caused by lithospheric thinning over a mantle heat source. Several continental swells are associated with intraplate volcanism, and the available data suggest that these are also formed by lithospheric thinning. Approximately 10% of the earth's surface is presently part of a hotspot swell, which implies that hotspot epeirogeny is a process of major tectonic importance. A stochastic model of continental hotspot epeirogeny shows that, for any particular continental area, the mean time between episodes of hotspot uplift is only 600 m.y. The amount of heat delivered to the upper mantle by the lithospheric thinning process is sufficient to explain the background heat flux of about 25 mW m−2 which is observed on the continents.
One hundred and sixty samples of groundwater from nearly all parts of Egypt have been collected and chemically analyzed in order to assess the country's geothermal potential. The samples considered to be thermal include 20 wells (T > 35°C), 4 springs (T > 30°C) and 1 spring not included in the present inventory. The remaining samples, together with data from the literature, establish background chemistry. The hottest springs are located along the east shore of the Gulf of Suez: Uyun Musa (48°C) and 'Ain Hammam Faraoun (70°C). Additional warm springs are located along both shores of the Gulf of Suez and this region is the most promising for geothermal development. The Eastern Desert of Egypt, particularly the coastal area adjacent to the Red Sea has above normal heat flow ( ~ 72.0 < mWm−2) and therefore some geothermal potential although only one thermal well (Umm Kharga: 35.8°C) could be located, In the major oases of the Western Desert (Kharga, Dakhla, Farafra and Bahariya), the regional temperature gradient is low (< 20°C/km), but many of the wells tap deep artesian aquifers and produce large volumes of water in the 35–43°C range. Such wells constitute a low temperature geothermal resource. None of our samples in northern Egypt can be considered thermal including several reported “hot springs.” Application of the silica, NaKCa. and NaKCaMg geothermometers does not indicate the presence of a high temperature geothermal resource at any area we visited.
An active median spreading center has been identified in the Red Sea south of 22°N, but from published reports, the northern Red Sea appears to be essentially aseismic. We have used microearthquake monitoring techniques along the Egyptian Red Sea margin to investigate the active tectonics in the region and have found that the northern Red Sea is not aseismic. Events recorded with epicenters in the Red Sea define an active zone extending south-southeast from the Gulf of Suez into the axial region of the Red Sea down to 25.75°N, with additional microseismicity between 24° and 25°N, suggesting active median spreading in the northern Red Sea. Two areas of intense microearthquake activity have also been identified; the first at the southern end of the Gulf of Suez and the second in the Egyptian Red Sea Hills, clustered at approximately 25.28°N, 34.52°E. The Gulf of Suez seismicity results from the adjustments in motion at the triple junction between the African and Arabian plates and the Sinai subplate. The source of the seismicity in the Egyptian Red Sea Hills is unknown, but a uniform fault plane mechanism is not indicated by first motion studies or the spatial distribution of the hypocenters.
A simple model for the development and evolution of sedimentary basins is proposed. The first event consists of a rapid stretching of continental lithosphere, which produces thinning and passive upwelling of hot asthenosphere. This stage is associated with block faulting and subsidence. The lithosphere then thickens by heat conduction to the surface, and further slow subsidence occurs which is not associated with faulting. The slow subsidence and the heat flow depend only on the amount of stretching, which can be estimated from these quantities and from the change in thickness of the continental crust caused by the extension. The model is therefore easily tested. Preliminary investigations of the Great Basin, the Aegean, the North Sea and the Michigan Basin suggest that the model can account for the major events in their evolution.
The relative motion between the plates on each side of the East African Rift Valley can be obtained from the opening of the Red Sea and the Gulf of Aden. The calculated direction of relative motion agrees well with fault plane solutions for earthquakes north of the equator.
Thesis (Ph. D.)--New Mexico State University, 1983. Microfilm. s
British Library microfilm no. : D18605/77. Thesis (Ph. D.)--University of Newcastle upon Tyne. 1976.
From studies of the global heat flow data set, it has been generalized, with respect to the continental lithosphere, that there is a negative correlation between heat flow and the lithosphere's tectonic edge, and that the lithosphere's thermal evolution is similar to that of the ocean basins, resulting in a 'stable geotherm' in both environments. It is presently noted that a regional study perspective for heat flow data leads to doubts concerning the general applicability of either statement. Rao et al. (1982) have demonstrated that the data are not normally distributed, and that it is not possible to establish a negative correlation between heat flow and age in a rigorous statistical fashion. While some sites of stable continental blocks may have a geotherm that is by chance similar to that for old ocean basins, this need not hold true generally, and many stable continental terranes will be characterized by geotherms very different from those for old ocean basins.
The rate of ascent of the thermal perturbation of eruptive rock types in the Kenya Dome region can be calculated for depths of origin ranging from greater than 170 km to the lower crust (25-30 km) as combined with dated occurrences. An equation is derived and solved iteratively for ascent velocity at 10 km depth intervals from 150-30 km, assuming a thermal diffusivity of 1 sq mm/sec. For radii of 50 and 100 km and constant gradient increases within the range 55-60 C/km over the lithosphere-asthenosphere boundary (LAB) ascent depth range, the calculated rate of upwelling corresponds well with the results of a simple thermal model of lithospheric thinning. A 1 C/km change in gradient results approximately in a 0.55 Myr change in ascent time from 150 to 30 km, due to the increasing differential between the geotherm and the solidus with decreasing depths and the increasing rate of heat loss to the surface. It is suggested by the temporal-spatial-compositional relations of eruptives in the Kenya Dome region that there is a shallowing of magma source regions with time, implying encroachment of a thermal anomaly.
It is suggested that two basic types of rifting-volcanism relative timing might be related to two basic modes of rifting. In one sequence, volcanism and, usually, local doming predate major rift formation, while in the other type, rifts form first and volcanism follows. In the first mode of rifting, the mantle plays an active role and convection 'plumes' dome up and crack the lithosphere, while in the second case, the horizontal movements of plates give rise to extension of the lithosphere and induce rifting, and the mantle is passive. Since numerous local conditions complicate this simple pattern, detailed stratigraphic/structural analysis of individual rifts is recommended.
The implications of heat flow data available from five major Cenozoic continental rift systems for the processes of continental rifting are discussed, and simple thermal models of lithospheric thinning which predict uplift are used to further constrain the thermal processes in the lithosphere during rifting. Compilations of the heat flow data are summarized and the salient results of these compilations are briefly discussed. The uplift predictions of the slow and rapid thinning models, in which thinning is assumed to occur at a respectively slower and faster rate than heat can be conducted into the lithosphere, are presented. Comparison of uplift rates with model results indicates that the lithosphere is in a state between the two models. While uplift is predicted to continue after thinning has ceased due to thermal relaxation of the lithosphere, the rapid thinning model is always predicted to apply to surface heat flow, and an anomaly in this flow is not predicted to develop until after thinning has stopped.
It is thought likely that thermal thinning and/or diapirism can cause the extensional stress required for rifting. The rifting, however, will not occur unless the regional tectonic regime permits the sides of the rift to diverge. Whereas passive plate extension could cause rifting in isolation, the extension and rifting are likely to be localized where the lithosphere is weakest over an existing thermal anomaly. In those cases where asthenospheric diapirism occurs, which is essentially a response to thinning of the lithosphere by thermal thinning or plate extension, the effects of diapirism may completely mask the initiating mechanism. It is believed that anomalous heat transfer into the lithosphere, diapirism, and magmatism must all figure in rifting, along with a deviatoric stress field that will permit extension in a developing rift. Even though the models are useful in permitting idealized processes to be quantified and tested, better knowledge of lithosphere properties is considered necessary, in particular knowledge of mantle viscosity and its temperature dependence.
I WOULD like to comment on some of the assumptions and results of a
recent letter by McKenzie et al.1. They reconstruct the
pre-movement position of Arabia and Africa by fitting the two coast
lines of the Red Sea, assuming that the entire space between the coasts
is occupied by newly formed oceanic crust. This assumption ignores the
existence of the Danakil horst, which consists of continental crust
(Pre-Cambrian, Jurassic) and which is some 80 km wide, in between these
two coast lines in the southern Red Sea depression. It seems impossible
to close the gap of the Red Sea without leaving the space required for
this continental block.
Seismic refraction profile, Kingdom of Saudi Arabia: field operations, instrumentation, and initial results
- H R Blank
- J H Healy
- J Roller
- R Lamson
- F Fisher
- R Mcclearn
- S Allen
Blank, H. R., Healy, J. H., Roller, J., Lamson. R., Fisher, F., McClearn, R. and Allen, S. 1979. Seismic
refraction profile, Kingdom of Saudi Arabia: field operations, instrumentation, and initial results,
U.S. Geol, Surv., Saudi Arabian Project Rept. 259:49 pp. + 21 figs.