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1.
The geothermal regime beneath the Barramiya-Red Sea coast area of the Central Eastern Desert of Egypt has been determined by using the Curie point depth, which is temperature dependent. This study is based on the analysis of aeromagnetic data. The depth to the tops and centroid of the magnetic anomalies are calculated by power spectrum method for the whole area. The result of this investigation indicates, two new maps of the Curie point depth (CPD) and the surface heat flow (q) maps of the study area. The coastal regions are characterized by high heat flow (83.6 mW/m2), due to the geothermic nature of the region, and shallow Curie depth (22.5 km), where (CPD) depends on the tectonic regime and morphology in the eastern part of the area. The western portion of the studied area has a lower heat flow (<50 mW/m2) and deeper Curie depth (∼40 km), due to the existence of a large areal extent of negative Bouguer anomaly in the NE-SW direction. In addition to its bordering to the Red Sea margin, such high heat flow anomaly is associated with the increased earthquake swarms activity in the Abu Dabbab area.  相似文献   

2.
Spectral analysis method was applied to aeromagnetic data obtained for Ikogosi warm spring (IWS) area of southwestern Nigeria. This was done with the objective of determining the bottom of the magnetized crust called Curie point depth (CDP) and understand the nature and extent of the local geothermal system at depth beneath IWS. The depth to the centroid, Z o, of the deepest distribution of the magnetic dipoles was obtained by computing least-squares fit to the lowest-frequency segment of the azimuthally averaged log power spectrum. The average depth to the top of the deepest crustal block was computed as the depth to the top, Z t, of the second lowest-frequency segment of the spectrum. The depth to the bottom of the deepest magnetic dipoles, the inferred Curie point depth, was then calculated from Z b?=?2Z o???Z t. The Curie depth estimates for IWS range between 4.68 and 11.38 km (below sea level). We also estimate the heat flow and Curie temperature using a one-dimensional conductive heat transport model. The average heat flow, 42 mW m?2, and geothermal gradient, 32°C/km, obtained suggest a low enthalpy thermal regime. The Curie temperature for the region varies between 153°C and 350°C. Also, an inverse linear relationship between heat flow and Curie depths was determined. Good agreement between the Curie point depths derived from heat flow data and magnetic data suggests that the Curie point depth analysis is useful to estimate the regional thermal structure and the tectonic settings.  相似文献   

3.
The Curie point depth map of Eastern Iran was constituted from spectral analysis of the aeromagnetic data. The reduction to pole (RTP) was applied to the magnetic anomaly data. The Curie point depth values from 165 overlapping blocks, 100 × 100 km in size, have been estimated. The Curie point depth method provides a relationship between the 2-D FFT power spectrum of the magnetic anomalies and the depth of magnetic sources by transforming the spatial data into the frequency domain. The centroid and top depth of the magnetic sources (respectively Z0 and Zt) is calculated from radially averaged log power spectrum for each block. Finally, the Curie point depth of Eastern Iran is obtained by Zb = 2Z0–Zt. The highest value of 24 km is located in eastern and western boundaries of the Lut block, and the lowest value of 12 km is located at north of study area. The shallow depths in the Curie-point depth map are well correlated with the young volcanic areas and geothermal potential fields. Geothermal gradient ranging from 24 to 45°C/km. The deduced thermal structure in eastern Iran has a relationship with orogenic collapse associated with delamination of thickened lithospheric root between the Lut and Afghan continental blocks.  相似文献   

4.
南海西北部重磁场及深部构造特征   总被引：9，自引：3，他引：9  
通过对南海重磁数据的重新处理,得到南海西北部自由空间重力异常图、布格重力异常图、磁异常图和化极磁异常图,并对所反映的地球物理场特征加以分析。根据重力场资料对研究区的地壳结构进行了反演计算,结果表明地壳厚度在10～38km之间,总的趋势由陆向洋逐渐减薄,对应于地壳类型从陆壳、过渡壳到洋壳的分布特征。根据磁力资料计算了居里面深度,其埋深变化于11～27km之间,在陆区居里面是下地壳顶界面和莫霍面之间的另一个物性界面,而在海区则接近于莫霍面埋深。  相似文献   

5.
The Gulf of Suez is characterized by the presence of many hot springs and deep thermal wells scattered around its coastal areas. So it is considered one of the promised geothermal areas in Egypt. In this study, the main emphasis is to investigate the geothermal potential around the Gulf of Suez using the available logging and geothermometer datasets. The temperature profiles and well logging data of some hot springs and deep wells around or within the coastal area of the Gulf of Suez are used in this study. The temperature profiles are analyzed and some important thermophysical properties are estimated (geothermal gradient, thermal conductivity, heat flow, and specific heat capacity). Such analysis revealed that a medium to high geothermal gradient (22.0–30°C/Km) is given for the Gulf of Suez as a whole, with some spots of much higher gradient in the order of 35.0–44°C/Km (Ras Fanar and Hammam Faraun areas). The compiled thermal plots show that the thick evaporites and rock salt lithology, which is a major constituent in this area, attain the highest thermal conductivity (>3.10 W/m/K) and heat flow (>90 mW/m2) and the lowest specific heat capacity (<0.30 J/kg/K). The available gamma ray and the natural gamma ray spectroscopy logs are used to conduct a radioactive-based heat generation study using the characteristic radioactive nature of some elements like; 238U, 235U, 232Th, and of the isotope of 40K. A good linearity is observed between the heat production (A in microwatt per cubic meter) and the gamma ray (API) along a wide range of datasets (0–150 API) in all wells. The heat production factor increases in the carbonate lithology (up to 3.20?μW/m3) and is proportional to the shale volume. A geothermometer-based study is used to estimate the subsurface formation temperature and heat flow from the geochemical analysis of some water samples collected from the studied hot springs. The estimated thermal parameters are in harmony with the regional thermal regime concluded form logging data. A thermal basin growth study, in relation to the clay diagenesis is conducted concerning the thermal effects that take place with depth giving rise to another clay mineral (illite). Furthermore, a number of 2D thermal–burial history diagrams are constructed for the complied sections of some of the studied areas to show the vertical distribution of the estimated petrothermal properties. A reserve evaluation study is carried out to estimate the economic geothermal capacity of these hot springs to be used as alternative clean source for possible energy production (electricity) and other low-temperature purposes.  相似文献   

6.
An updated analysis of geothermal data from the highland area of eastern Brazil has been carried out and the characteristics of regional variations in geothermal gradients and heat flow examined. The database employed includes results of geothermal measurements at 45 localities. The results indicate that the Salvador craton and the adjacent metamorphic fold belts northeastern parts of the study area are characterized by geothermal gradients in the range of 6–17°C/km. The estimated heat flow values fall in the range of 28–53 mW/m2, with low values in the cratonic area relative to the fold belts. On the other hand, the São Francisco craton and the intracratonic São Francisco sedimentary basin in the southwestern parts are characterized by relatively higher gradient values, in the range of 14–42°C/km, with the corresponding heat flow values falling in the range of 36–89 mW/m2. Maps of regional variations indicate that high heat flow anomaly in the São Francisco craton is limited to areas of sedimentary cover, to the west of the Espinhaço mountain belt. Crustal thermal models have been developed to examine the implications of the observed intracratonic variations in heat flow. The thermal models take into consideration variation of thermal conductivity with temperature as well as change of radiogenic heat generation with depth. Vertical distributions of seismic velocities were used in obtaining estimates of radiogenic heat production in crustal layers. Crustal temperatures are calculated based on a procedure that makes simultaneous use of the Kirchoff and Generalized Integral Transforms, providing thereby analytical solutions in 2D and 3D geometry. The results point to temperature variations of up to 300°C at the Moho depth, between the northern Salvador and southern São Francisco cratons. There are indications that differences in rheological properties, related to thermal field, are responsible for the contrasting styles of deformation patterns in the adjacent metamorphic fold belts.  相似文献   

7.
Geothermal gradients and present day heat flow values were evaluated for about seventy one wells in parts of the eastern Niger delta, using reservoir and corrected bottom–hole temperatures data and other data collected from the wells. The results showed that the geothermal gradients in the shallow/continental sections in the Niger delta vary between 10 - 18° C/km onshore, increasing to about 24° C/km seawards, southwards and eastwards. In the deeper (marine/paralic) section, geothermal gradients vary between 18 - 45° C/km. Heat flow values computed using Petromod 1–D modeling software and calibrated against corrected BHT and reservoir temperatures suggests that heat flow variations in this part of the Niger delta range from 29–55 mW/m2 (0.69–1.31 HFU) with an average value of 42.5 mW/m2 (1.00 HFU). Heat flow variations in the eastern Niger delta correspond closely to variations in geothermal gradients. Geothermal gradients increase eastwards, northwards and seawards from the coastal swamp. Vertically, thermal gradients in the Niger delta show a continuous and non-linear relationship with depth, increasing with diminishing sand percentages. As sand percentages decrease eastwards and seawards, thermal gradient increases. Lower heat flow values (< 40 mW/m2) occur in the western and north central parts of the study area. Higher heat flow values (40 - 55 mW/m2) occur in the eastern and northwestern parts of the study area. A significant regional trend of eastward increase in heat flow is observed in the area. Other regional heat flow trends includes; an eastwards and westwards increase in heat flow from the central parts of the central swamp and an increase in heat flow from the western parts of the coastal swamp to the shallow offshore. Vertical and lateral variations in thermal gradients and heat flow values in parts of the eastern Niger delta are influenced by certain mechanisms and geological factors which include lithological variations, variations in basement heat flow, temporal changes in thermal gradients and heat flow, related to thicker sedmentary sequence, prior to erosion and evidenced by unconformities, fluid redistribution by migration of fluids and different scales of fluid migration in the sub-surface and overpressures.  相似文献   

8.
The tectonic position of Egypt in the northeastern corner of the African continent suggests that it may possess significant geothermal resources, especially along its eastern margin. The most of the thermal springs in Egypt are located along the shores of Gulf of Suez and Red Sea. These springs are probably tectonic or nonvolcanic origin associated with the opening of the Red Sea—Gulf of Suez rifts, where the eastern shore of the Gulf of Suez is characterized by superficial thermal manifestations including a cluster of hot springs with varied temperatures. Hammam Faraun area consists of the hottest spring in Egypt where the water temperature is 70°C. Conceptual as well as numerical models were made on the Hammam Faraun hot spring based on geological, geochemical, and geophysical data. The models show that the heat source of the hot spring is probably derived from high heat flow and deep water circulation controlled by faults associated with the opening of the Red Sea and Gulf of Suez rifts.  相似文献   

9.
The Hammam Faroun has a particular importance due to its geothermal activity which constitutes the main geothermal resource of Egypt. The area is located on the Sinai Peninsula, a subplate bounded by two seismically active structural zones along the Gulf of Suez and Gulf of Aqaba. High-resolution ground-based gravity and magnetic data are available for the entire Hammam Faroun area, acquired as part of a national project to explore for mineral, geothermal, and hydrocarbon resources. Gravity and magnetic data were analyzed using Source Edge Detection and Source Parameter Imaging (SPI) techniques to image subsurface structures. These analyses show that the area is characterized by a set of northwest-striking faults lying parallel to the Gulf of Suez. Orthogonal patterns are also present, possibly related to rifting of the Gulf of Suez. Depth analysis using the SPI method indicates that surface faults extend to 5-km depth. Analysis of potential-field data elucidates the structurally complex subsurface structure of the Hammam Faroun area.  相似文献   

10.
The geothermal structure beneath of the Barramiya?CRed Sea coast area of the Central Eastern Desert of Egypt has been determined using Curie point depth (CPD), which is temperature-dependent. The CPD and the surface heat flow (q) maps of such area are estimated by analyzing aeromagnetic data. Such data are low-pass-filtered and analyzed to estimate the magnetic bottom using the centroid method. The heat flow map reflects the geothermic nature of the region. However, it is suggested that the shallow Curie point temperature depth pattern depends on the tectonic regime and morphology, which continues eastwards through the Red Sea. Particularly, the coastal regions are characterized by high heat flow (83.6?mW/m2) and shallow Curie depth (22.5?km), whereas the western portion of the studied area has a lower heat flow (<50?mW/m2) and deeper Curie depth (~40?km). In addition to its bordering to the Red Sea margin, such high heat flow anomaly is associated with the increased earthquake swarms activity in the Abu Dabbab area. El-Hady (1993) attributed the swarm activity to the geothermal evolution. Also, the heat flow pattern is correlatable by the numerous results of shallow borehole temperature measurements as reported by Morgan and Swanberg (1979). A significant low heat flow extending in the northeast?Csouthwest direction, which is associated with NE?CSW large areal extent negative Bouguer gravity anomaly and NE/SW-trending belt of the deep CPD region, seems to be directly related to the surface outcrops of Precambrian older granitoids of the mountainous range of that trend.  相似文献   

11.
《Applied Geochemistry》1996,11(3):471-479
Thermal waters with discharge temperatures ranging from 32 to 70°C are being discharged along the Gulf of Suez (Egypt) from springs and shallow artesian wells. A comprehensive chemical and isotopic study of these waters supports previous suggestions that the waters are paleometeoric waters from the Nubian sandstone aquifer. The chemical and isotopic compositions of solutes indicate possible contributions from Tertiary sedimentary aquifer rocks and windblown deposits (marine aerosols and/or evaporite dust) in the recharge area. There is no chemical or isotopic evidence for mixing with Red Sea water. Gas effervescence from the Hammam Faraoun thermal water contains about 4% CH4 (δ13C = −32.6‰) and 0.03% He having an isotopic ratio consistent with a mixture of crustal and magmatic He (3He/4He = 0.26 Re). Geothermometers for the thermal waters indicate maximum equilibration temperatures near 100°C. The waters could have been heated by percolation to a depth of several km along the regional geothermal gradient.  相似文献   

12.
Heat has a close relation to cratonic stability. We reconstructed the thermal history of the eastern North China, Wyoming, and Siberian cratons by using xenolith and thermal indicator data, and then the thermal lithospheric thickness in geological time was calculated by combining the crustal structural and thermal parameters. Researches from three cratons demonstrate that heat-flow values of the eastern North China Craton (eNCC) and Wyoming Craton (WC) have increased exceeding 20 mW/m2 in the Meso-Cenozoic and the thermal lithospheric thickness has decreased by >100 km because of the cratonic destabilization. However, the thermal history variation of the Siberian Craton (SC) is small, ~5 mW/m2, the lithosphere has remained stable and it has experienced relatively little lithospheric thinning <100 km. The differences of the cratonic thermal regime are related to the breakup of the Pangea supercontinent. Destabilized cratons on active continental margin are directly affected by plate subduction. Stable cratons in the interior of the supercontinents are directly affected by the upwelling of superplumes and that may result in lithospheric thinning. Differences in the thermal evolutions of cratons provide new geothermal evidence for the different thermal regimes associated with the breakup of the Pangea supercontinent.  相似文献   

13.
Understanding the thermal distribution within the crust and rheology of the earth’s lithosphere requires the knowledge of the Depth to the Bottom of Magnetic Sources (DBMS). This depth is an important parameter in this regard, which can be derived from aeromagnetic data and can be used as a representation for temperature at depth where heat flow values can be evaluated. In this work, high-resolution aeromagnetic (HRAM) data of part of Chad Basin (covering about 80% of the entire basin), an area bounded by eastings 769,000 and 1,049,900 mE and northings 1,200,000 and 1,500,000 mN, were divided into 25 overlapping blocks and each block was analyzed using spectral fractal analysis method. The spectral analysis method was used to obtain the Depth to the Top of Magnetic Source (DTMS), centroid depth, and DBMS. From the calculated DBMS, the geothermal gradient and heat flow parameters were evaluated and the result obtained shows that DBMS varies between 18.18 and 43.64 km. Also the geothermal gradient was found to be varying between 13.29 and 31.90 °C/km and heat flow parameters vary between 33.23 and 79.76 mW/m2, respectively. The heat distribution of this area is one of the key parameters responsible for various geodynamic processes; therefore, this work is important for numerically understanding the thermal distribution in Chad Basin, Nigeria since rock rheologies depend on temperature, which is a function of depth.  相似文献   

14.
The geothermal field is mainly controlled by the regional tectonic framework characterized by alternationsof uplifted and depressed basement. and exhibits a similar zoned distribution of temperatures. In the upliftedarea the geothermal gradient (G) and terrestrial heat flow value(q) of the Cenozoic sedimentary cover are rela-tively high, with G=3.5-5.0℃/100m and q=63-84mW/m~2; whereas in the depressions they are rela-tively low, with G=2.7-3.5℃/100m and q=46-59mW/m~2. In the whole region, G=3.58℃/100m and q=61.5±13.4nW/m~2, indicating a comparatively high geothermal background and the presence of localgeothermal anomalies. A comparison of the results of mathematical simulation of the geothermal field with themeasured values shows a good agrecment between them. The geothermal difference between various tectonicunits is caused chiefly by the lateral and vertical variation of thermal properties of shallow crustal rocks. Thisphenomenon can be regarded as the result of redistribution of relatively uniform heat flows from the deep crustin the surficial part of the crust in the process of their upward conduction.  相似文献   

15.
This work deals with 2D thermal modeling in order to delineate the crustal thermal structure of central India along two Deep Seismic Sounding (DSS) profiles, namely Khajuriakalan–Pulgaon and Ujjan–Mahan, traversing the Narmada-Son-Lineament (NSL) in an almost north–south direction. Knowledge of the crustal structure and P-wave velocity distribution up to the Moho, obtained from DSS studies, has been used for the development of the thermal model. Numerical results reveal that the Moho temperature in this region of central India varies between 500 and 580 °C. The estimated heat flow density value is found to vary between 46 and 49 mW/m2. The Curie depth varies between 40 and 42 km and is in close agreement with the Curie depth (40±4 km) estimated from the analysis of MAGSAT data. Based on the present work and previous work, it is suggested that the major part of peninsular India consisting of the Wardha–Pranhita Godavari graben/basin, Bastar craton and the adjoining region of the Narmada Son Lineament between profiles I and III towards the north and northwest of the Bastar craton are characterized with a similar mantle heat flow density value equal to ∼23 mW/m2. Variation in surface heat flow density values in these regions are caused by variation in the radioactive heat production and fluid circulation in the upper crustal layer.  相似文献   

16.
This study focuses on the water and gas chemistry of the northeastern Algerian thermal waters. The helium gas was used to detect the origin of the geothermal fluid. In the Guelma Basin, the heat flow map shows an anomaly of 120 ± 20 mW/m2 linked to the highly conductive Triassic extrusion. The chemical database reveals the existence of three water types, Ca-SO4/Na-Cl, which are related to evaporites and rich in halite and gypsum minerals. The third type is Ca (Na)-HCO3, which mostly characterizes the carbonated Tellian sector. The origin of thermal waters using a gas-mixing model indicates a meteoric origin, except for the El Biban hot spring (W10), which shows a He/Ar ratio of 0.213, thus suggesting the presence of batholith. The helium distribution map indicates a lower 3He/4He ratio between 0 Ra and 0.04 Ra in the W10 and W15 samples, which is compatible with the crustal ratio. Reservoir temperatures estimated by silica geothermometers give temperatures less than 133 °C. The geothermal conceptual model suggests that a geothermal system was developed by the deep penetration of infiltrated cold waters to a depth of 2.5 km and then heated by a conductive heat source (batholith for El Biban case). The thermal waters rise up to the surface through the deep-seated fractures. During their ascension, they are mixed with shallow cold groundwater, which increase the Mg content and cause the immature classification of the water samples.  相似文献   

17.
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18.
The Curie point depth of continental crust can reflect the regional tectonic pattern and geothermal structures. Analysis of magnetism is an efficient way to obtain the Curie point depth on a regional scale. This study systematically investigated the Curie point depth of Sulu (苏鲁) ultrahigh pressure (UHP) metamorphic belt (33°40'N to 36°20'N and 118°E to 120°E, ca. 60 000 km2), eastern China using aeromagnetic data. The results show that the Curie point depth of the Sniu region varies from 18.5 to 27 kin. The shallowest Curie point depth (ca. 18.5 km) is located in Subei (苏北) subsidence, where the estimated temperature gradient value is about 31.35℃/kin, which is comparable with the measured value of 30℃/krn. In addition, a two-dimensional numerical solution of the heat conduction was used to calculate the temperature field to a depth of 30 km along the profile from Tancheng (郯城) to Lianshui (涟水) with a length of 139 km. The steady state model solved using the finite element method shows that the temperature around the Curie point depth is about 585.36℃, which is close to the Curie temperature (580 ℃) of magnetite at atmospheric pressure. These results provide new insights into the tectonic and continuous thermal structures of the Sulu UHP metamorphic belt.  相似文献   

19.
干热岩作为地热资源的重要组成部分,被视为未来的清洁能源,极具开发前景和研究价值。文章以桂东南潜在的干热岩为研究对象,通过基础地质、地球物理和地球化学资料的二次开发和实地考察,对区域构造-岩浆-沉积建造系统、岩石圈结构、现今地热场特征和地震、温泉分布规律等进行综合分析,旨在初步探讨桂东南地区干热型地热资源的潜力。结果表明:桂东南地区岩石圈较薄,分别在25 km之上和6~8 km处存在厚约6 km和2 km的双层低速层/带,指示滑脱型韧性剪切和高温地质体的存在;印支期花岗岩提供稳定的放射性生热物质基础(U含量均值5.41×10-6,Th含量均值18.38×10-6,K2O含量均值4.43%),新生代火山活动(OIB)在补给大量地热能的同时,为深部热物质上涌提供通道;桂东南地区现今地热存在明显异常,大地热流值介于80~100 mW/m2,北海-南宁地温梯度值高于30 ℃/km,钦州、合浦中-新生代断陷盆地因沉积盖层裂隙度、孔隙度和导热率低且圈闭性好而属于干热岩地热资源丰富区。对桂东南干热型地热资源潜力的研究,将为广西能源结构调整、生态环境优化和产业转型升级助力。  相似文献   

20.
The aim of the present work is to evaluate the stress direction and the tectonic trends of the study area using magnetic anisotropy and potential field data interpretations (Bouguer and aeromagnetic). The specific objective of the gravity and aeromagnetic interpretation is to establish the trend and depth of the structural configuration of the basement rocks. Horizontal gradient techniques could to delineate directions of deep sources and enabled tracing several faults, lineaments and tectonic boundaries of basement rocks. The trend analysis shows N40°?C50°W, N10°?C20°W and N10°?C20°E which may be related to the Gulf of Suez, Red Sea and Gulf of Aqaba stresses. However, Euler Deconvolution technique was applied using the aeromagnetic data to provide reliable information about penetrated source depth (100 m and ??10.0 km) and trends of the subsurface sources (principally in NW and NE directions). Moreover, representative 72 oriented rock samples have been collected from seven sites in the study area. The rock magnetic properties and magnetic anisotropy analysis have been determined for all the studied samples. The interpretation clearly defined magnetic lineation at all sites and anisotropy of magnetic susceptibility (AMS) parameters. The stress direction of the studied area has been evaluated using magnetic anisotropy and geophysical analysis. Generally the estimated geophysical data analysis (Bouguer and aeromagnetic) are well consistent with the AMS interpretations of this study. The results indicated that the directions of predominant faults and foliations are NW-SE (related to the Gulf of Suez and Red Sea rifting) which indicate that the main stress and tectonic trend is NE-SW, which is more predominant in southern Sinai region. Moreover, it is clear that, the studied area was affected also by less predominant sources trended in NE-SW direction, which related to the tectonic activity of Gulf of Aqaba. The least predominant is north 40°?C50° east that is probably due to the Syrian Arc system. Finally, our results are extremely coincided with the previous stress directions derived from geological, seismological and tectonic analysis in northern Red Sea rift, Gulf of Suez and Sinai regions.  相似文献   

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