Kalabsha Area Research Articles

Subsurface geology and geochemical evaluation of the Middle Jurassic-Lower Cretaceous organic-rich intervals, West Kalabsha area, Western Desert, Egypt

The West Kalabsha (WKAL) area is a western extreme exploratory area of the Faghur Basin in the Western Desert of Egypt. The study of four wells (WKAL; A-1 X, K-1 X, P-1X, and C-1 X), interpreted with twenty seismic lines, shows that the area is dissected by a series of normal faults with an irregular, E–W strike direction. The general trend of the throw is toward the south–southeast. The most prospective area for hydrocarbon (HC) migration is toward the north (upthrown side) of an E-W striking normal fault north of the WKAl-K-1 X and A-1 X wells. The WKAL-P-1 X and WKAL-K-1 X wells in the Faghur Basin were selected for both geochemical evaluation of possible source rock intervals and burial history modelling within the basin. Integration of the wire-line logs with geochemical analysis identified six organic matter-rich intervals (OMRIs) within the Middle Jurassic-Lower Cretaceous sequence. Four intervals are in the Alam El-Bueib-3C (AEB-3C) member with a cumulative vertical thickness of 530ft. The other OMRIs are 110ft in thickness recorded within the AEB-6 (10ft) and Upper Safa (100ft) members. The studied organic matter (OM) reveals type III, IIIC, and IV kerogens (mainly gas-prone) with a terrestrial origin. They have reached a maturity level consistent with the late oil window. The expulsion threshold depth detected in the WKAL-P-1 X well is 12000ft in the AEB-3C member, whereas the active source depth limit (ASDL) is 15000ft in the Safa Member. The present study suggests a paleo-geothermal gradient range between 1.13oF/100ft and 1.39oF/100ft with an estimated regional erosion of 5500 to 7000ft of strata mainly between the Paleozoic-Jurassic and Cretaceous-Tertiary boundaries. The present-day geothermal gradient based on bottom-hole temperatures shows a geothermal gradient of 1.4oF/100ft (WKAL-P-1 X), that increases to the north to 1.65oF/100ft (WKAL-K-1 X). Burial history modelling reveals that sedimentary strata entered the mature oil zone in the Early Cretaceous (110–115Ma) at depths of 7500–8000ft in the deepest part of WKAL-P-1 X and WKAL-K-1 X wells (Paleozoic strata). Maturation continued to present, resulting in Jurassic and Lower Cretaceous strata currently falling into the late oil window.

Provenance studies of Kalabsha kaolin deposits, Egypt: a petrographical and geochemical approach

The present study focuses on the kaolin deposit in Kalabsha area south Western Desert of Egypt in an attempt to determine its possible source, tectonic setting, and weathering history by means of integrated petrographical and geochemical approaches. The petrographical study was worked by microscopic investigation and supported by X-ray diffraction analysis. X-ray fluorescence and inductively coupled plasma-mass spectrophotometry methods were used for the determination of the bulk elemental composition. Mineralogical analysis revealed that kaolinite is the main clay mineral component indicating a severe chemical weathering of Al-rich source rocks and complete leaching under warm, semiarid climatic conditions. The nonclay minerals are represented by quartz, iron oxides and hydroxides, Ti-bearing minerals, and zircon. Geochemical data show a prevalence of SiO2 and Al2O3 and enrichment of Hf, Nb, Ta, Th, U, and Zr that support the kaolinitic nature of the deposits and their derivation from a felsic granitic terrain. The high values of the chemical index of alteration and the lower values of the index of compositional variability also suggest an intensive weathered source area and the geochemical maturity of the sediments. Other relevant geochemical discriminant functions and plots reveal felsic igneous parent rock for the kaolin deposits. Q-mode hierarchical cluster analysis combined with the normalized rare earth element patterns played a crucial role in unraveling the origin of the studied deposits. The results show that the most probable source rock of the Kalabsha kaolin deposits is the intense weathering of relatively proximal Adara Adatalob granites and their similar rock types in the Arabian-Nubian Shield from the south Eastern Desert of Egypt.

Mineralogy and geochemistry of clay fractions from different saprolites, Egypt: implications for the source of sedimentary kaolin deposits

The clay fractions of saprolites from granites, basalt, and schists in Egypt were subjected to mineralogical and geochemical investigations to examine the effect of source rock on the composition of the saprolites and the possibilities of these saprolites as a source of the nearby sedimentary kaolin deposits. The clay fractions of the studied saprolites show mineralogical and geochemical variations. Saprolites from the granites consist of kaolinite, while saprolites from the basalts are composed entirely of smectite. Schists-derived saprolites are composed of kaolinite in some cases and of a mixture of kaolinite, illite, and chlorite in the other. Saprolite from the basalt is characterized by relatively higher contents of TiO2 and Ni compared to the saprolites from granites. Saprolites from granites have higher contents of Ba, Li, Pb, Sr, Th, Y, and Zr compared to those of the saprolites from the basalts and schists. Saprolites from different schists show variations in the distributions of many constituents, such as TiO2, Cr, Ni, Ba, Y, and Zr. Although chondrite-normalized rare earth elements (REE) patterns are characterized by relative enrichments in the light rare earth elements (LREE) compared to the heavy rare earth elements (HREE) in all saprolites, granitic saprolites show negative Eu anomalies, while saprolite from basalt has no Eu anomaly. REE patterns of the saprolites from schists exhibit slight positive Ce anomalies and slight to moderate negative Eu anomalies. Weathering of saprolites from the basalt and metasediments is classified as the bisiallitization type, while weathering of saprolite from the granite is allitization type. Saprolites from schists vary from the bisiallitization (Aswan and Abu Natash) and allitization (Khaboba) types. Saprolites from the Khaboba schist can be considered the possible source of the Carboniferous kaolin deposits in the Hasber and Khaboba areas of Sinai, based on the similarity in the mineralogy and geochemistry of major, trace, and REE between the saprolites and the deposits. On the other hand, Carboniferous sedimentary kaolin deposits in the Abu Natash area, as well as the Cretaceous kaolin deposits in all areas of Sinai, might have been derived from the nearby schist saprolites, based on the similarity in the mineralogy and geochemistry between the saprolites and the kaolin deposits. Granites from the Arabian-Nubian Shield (ANS) and East Sahara Craton (ESC) are the possible sources of the pisolitic and plastic kaolin deposits in the Kalabsha area (Aswan), as indicated by the similarity in the mineralogy and geochemistry of the granitic saprolites and the kaolin deposits.

Pre- and post-seismic displacements associated with the Aswan 2011 earthquake (M = 4.2) derived from recent geodetic GPS data

Due to the importance of Aswan area, Egypt, it has been selected for the present study. Since 1982, after the main shock of November 14, 1981 with M = 5.6, several study programmes were initiated for monitoring seismicity and crustal movements at Aswan area (Tealeb 1996). Starting from 1997, GPS geodetic networks were established and observed many times in different campaigns. The observations are repeated twice a year. At the beginning of 2012, a moderate earthquake has occurred in the Aswan region with magnitude of 4.2 located at the southwest of the High Dam along Kalabsha fault. Before and after this event, these local geodetic networks were measured using GPS. Regional, Kalabsha-Sayal and Kalabsha networks were used in the present work. GPS data were processed using Bernese 5.0. The collected data before and after this event have shown that the area southwest of the High Dam and Kalabsha area suffered from stress and strain. The behaviour of the areas has changed after earthquake for pre-earthquake.

Pisolitic flint kaolin from Kalabsha, Egypt: A laterite-derived facies

Nodular, pisolitic, and plastic kaolins from Kalabsha area, Egypt were investigated for their textural, mineralogical, and geochemical compositions to examine their source and origin. The three kaolins are composed of kaolinite, quartz, anatase, and traces of hematite and rutile. Clay fractions have relatively high Nb (56–189 ppm) and Zr (480–1260 ppm) contents. Heavy minerals from the sand fractions are composed of zircon, high Cr rutile, and leucoxene. Detrital quartz occurs as either monocrystalline or polycrystalline grains with worm-like corrosion features. Two types of quartz were distinguished based on their cathodoluminescence (CL) analysis; bright and dark luminescence quartz. Rare earth elements (REEs) patterns show enrichment of light REEs relative to heavy REEs ((La/Yb) N = 1.6–10) and negative Eu anomaly (Eu*/Eu = 0.6–0.7). Nodular and pisolitic kaolins show distinct positive Ce anomaly (Ce*/Ce = 1.2–3.4) and a variable LREE depletion. The pisolitic kaolin is considered here as flint kaolin based on its unique characteristics such as hardness, massiveness, conchoidal fracture, high density, very fine-grained nature, resistance to slacking in water, high crystallinity, and homogeneous compositions. Abundance of high Cr rutile, polycrystalline, and dark luminescent quartz suggest a contribution of medium to high grade metamorphic mafic rocks to the source of Kalabsha kaolins, while presence of zircon, bright luminescence monocrystalline quartz, and REEs pattern indicate a contribution of granitic rocks. The unusual high Nb contents attest to a contribution of alkaline rocks in the source area of the deposits. Lithostratigraphic succession, pisolitic texture, corroded quartz, depletion of many trace elements including LREE, distinct positive Ce anomaly, unusual grain size distribution, and compositional homogeneity suggest a lateritic precursor of the pisolitic flint kaolin. The lateritic precursor sediments have been deferrated and resilicified in the sedimentary basin to form the whitish flint clays with their unique physical and mineralogical characteristics as a result of volume increase associated to the transformation of Al-hydroxide minerals to kaolinite. Textural and geochemical variations unambiguously show that the overlying plastic clays are not derived by reworking from the pisolitic kaolins, but are derived from the saprolites underlying the lateritic crusts in the source region (sequential stripping).

Surface and subsurface structures of Kalabsha area, southern Egypt, from remote sensing, aeromagnetic and gravity data

Kalabsha area is known to be the most seismo-active zone at the southwestern region of the Aswan High Dam, in southern Egypt. The main purpose of this work is the analysis and interpretation of satellite imagery, aeromagnetic and ground gravity data of Kalabsha area in order to reveal the subsurface lithology and structure. The Landsat ETM+ data were produced in a false-color composite image (bands 1, 2 and 3 in RGB) at the same scale as the geological map in order to reveal some extra geological and structural features. An attempt has been made to analyse the complex nature of gravity and magnetic anomalies over the Kalabsha area to reveal their relationship with surface geology, structure and tectonics setting. These analyses include isolation of anomalies into regional and residual components using the band-pass filter, second vertical derivatives (SVD), upward continuation, and shadowgrams technique. It was noticed that, there is close correlation between gravity, magnetic and many of the major surface geological features of the region. The basement structural map of Kalabsha area has been prepared from the integration of SVD of regional component maps of both gravity and magnetic. The interpretation of the basement tectonic map of the area indicated the presence of two sets of faults NNW–SSE to N–S which is dissected by an E–W to WNW–ESE fault system. These two sets of fault systems as deduced from the gravity and aeromagnetic data were found to match well with that obtained from the Landsat image and geological map.

Detection of the seismic quiescence along the seismic active faults in Kalabsha area, west of Lake Nasser, Aswan, Egypt

The spatial and temporal distribution of seismicity around the northern part of Lake Nasser in Aswan has been continuously monitored by a short-period seismograph network since 1982. Data of this network, which consists of 13 field stations distributed around the Kalabsha fault, has demonstrated occurrences of three swarm sequences during the past 26 years. The first swarm occurred in June 1987 on a fault segment about 8 km in length beneath the lake water. The largest magnitude of this swarm was 3.7. Its hypocenters were located within the shallow depth’s interval (i.e., 2 to 5 km from the ground surface). The estimated b-value for this swarm was 0.63. The second swarm sequence took place at the intersection of the Seiyal fault with Kurkur fault about 10 km to the north of the June 1987 sequence. This swarm occurred during the period from August to December 2004 with largest magnitude of 4.1. The focal depths of this swarm also ranged from 2 to 5 km. The b-value of this swarm was found to be 0.69. The third swarm occurred recently in April 2007 with largest magnitude of 4.2 at the same location of 1987 sequence but its focal depths ranged from 6 to 8 km and has the b-value of 0.58. The composite focal mechanism study of these three swarm sequences revealed right-lateral strike slip faults with horizontal stress axes pattern. The relationship between the lake water level and the swarm sequences showed that both 1987 swarm and 2007 swarm occurred during the decreasing of water level, whereas the 2004 swarm occurred during the increasing of the water level. The study of these three swarm sequences illustrates an interesting phenomena, that there is a seismic quiescence preceding each swarm sequence. The duration period of the seismic quiescence ranges from 3 to 5 months.

A Study of Seismicity and Earthquake Hazard at the Proposed Kalabsha Dam Site, Aswan, Egypt

High and Aswan Dams Authority (HADA) proposed a plan aiming at constructing a rockfill dam in the Kalabsha area, about 60 km south of Aswan High Dam. The aim of this dam is to restrain the overflow of water to the Kalabsha Valley for keeping one billion cubic meters from being lost due to seepage and evaporation. The safety of dams during earthquakes is extremely important because failure of such a structure may have disastrous consequences on life and property. Therefore, different factors were considered as part of a site assessment. Five seismic source zones, close enough to the site to give rise to potentially damaging earthquake ground motions, were identified. Seven active faults that have the potential for producing significant earthquakes and that pass through or near the dam site were also identified. The earthquake loading represented by ground motions at the site was evaluated. Probabilistic seismic hazard procedures were used for assessing the earthquake loading at six individual sites using Area-and Line-Source Models (ASM & LSM). The ASM is based on current observed seismicity, whereas the LSM is based on geological slip rates. The output represents the expected acceleration amplitude with 90 percent probability of not being exceeded in exposure times of 20, 50, and 100 years. The results from the two models appear to be different, the expected ground motions from ASM were twice as high as expected from LSM. This difference is due to the load of the Aswan reservoir (Nasser Lake) triggering earthquakes on those parts of the faults that lie under the lake at Kalabsha area. The hazard at the selected sites is given by “the hazard curve” that is represented by the relationship between the peak ground acceleration and its annual exceedance probability. By comparing the curves for the six individual sites for the same source model, it can be concluded that the potential ground acceleration level for all the sites is almost the same. Considering the mean results from the two models, the annual exceedance probability of the expected ground acceleration from ASM is approximately ten times higher than the annual exceedance probability from LSM.

Focal mechanism determination based on the polarity and SV-P amplitude ratio in the Kalabsha area, Aswan, Egypt

Focal orientations are presented for small earth-quakes of the four different local seismic zones (zone A, zone B, zone C and zone D) in the Kalabsha area, Aswan, Egypt. These earthquakes (1.2≤M<3, and depth 1.5-23km) were monitored by the Aswan Telemetered Network between November 1995 and November 1997. Three or four single-event focal mechanisms and one composite event focal mechanism were determined for each zone. One composite focal mechanism for all events of the zones A, B, and C (10 earthquakes) was obtained. Both P-wave polarities and SV/P amplitude ratios were used to determine the focal mechanisms in the study area. The focal mechanism solutions in the four seismic zones show that they are almost characterized by strike-slip faults with two types of motion, right lateral along ENE-WSW faults and left lateral motion along NNW-SSE faults. The orientations of the compressional and tensional stresses prevailing in the area have the directions of ESE-WNW and NNE-SSW, respectively. It is found that there is no significant change in either the direction of prevailing stresses or the senses of motion along the preexisting faults in the area.

Recent Crustal Movements and Seismicity Studies Around Active Faults, Aswan, Egypt

Monitoring of recent crustal movements was carried out in Egypt for the first time in the Aswan region after the occurrence of the November 14,1981 earthquake with a magnitude of 5.5 in the Kalabsha area 60 km southwest from the Aswan High Dam. This earthquake was considered a very important event as it was located not far from the Aswan High Dam. Due to its possible association with the impoundment of the Aswan Lake, especially the water activity in and around this lake. p]The data used in this study consists of the geodetic data and the catalogue of earthquake determined by the Aswan seismic network. In this work, we are trying to give a clear picture about the order of movements and their role in earthquake occurrence in the Aswan region. The analysis of such measurements together with the frequency and intensity of seismic activity and the changes of the water level, can lead to understanding the cause of earthquake occurrence and its origin.

Interrelationship between major, minor and trace elements in Kalabsha wells and in high dam lake waters

Abstract Major, minor, physical (electrical conductivity) & chemical components (HCO‐ 3 ,SO2‐ 4,Cl‐ ,Ca, Mg, Na, K, pH, TDS) and trace elements (Ag, Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, Sr, and Zn) were determined in Kalabsha wells and in the High Dam Lake water. The water characteristics were followed up in the years 1991, 1992, 1993 and 1994. The results showed higher values for Cond. HCO‐ 3 , Cl‐ , SO2‐ 4, Ca, Mg, Na, K, TDS, Ag, Cd, Co, Cu, Cr, Fe, Mn, Ni, Pb, Sr and Zn in the water wells of Kalabsha area than in the Lake water. The pH values of the Lake water were higher than those of the wells water. There is no irregular interrelationship of major, minor and trace elements between the water of Kalabsha wells and the water of the High Dam Lake. However, Lake water is suitable for human consumption. The statistical analysis of the database of wells and Lake water shows positive and significant correlation coefficient values (r=0.665–0.986) between pairs: N: & Co, N. &Zn, Ni&Fe, Mn&Sr,etc.) standard deviation (SD) and coefficient of variance (C.V.%) of the wells and Lake water are in the range 0.19–75 and 0.7–53, respectively.

Gravity map of Kalabsha area, northwest of Aswan Lake, and its structural significance

A detailed gravity survey was carried out in one of the seismo-active areas at the northwestern region of the High Dam Lake (Kalabsha area) to study its subsurface structure. In order to understand the seismicity of the area, the establishment of a geodynamic model from geological and geodetic data is of great importance. After a series of adjustments and corrections of the measured gravity data, free-air and Bouguer anomaly maps were constructed for the Kalabsha area, and several interpretation techniques were applied to analyse these anomalies. The results of the analysis indicate that the Kalabsha area is affected by several faults trending mainly E-W and N-S. The active area located west of Gebel Marawa is bounded by a set of faults striking NE-SW, N-S and E-W. The throws of these faults range from 160 to 370 m. The minimum depth to the basement complex is about 200 m and its maximum depth is around 600 m. The thickness of the sedimentary column (Nubia sandstone) in the Kalabsha area decreases due west and increases toward the southern and eastern parts of the area. The results explain the tectonic framework of the area well.

Seismicity and composite focal mechanism for microearthquakes in Kalabsha area west of Aswan Lake and their tectonic implication

Seismicity of the Kalabsha area west of the Aswan Lake was examined using microearthquake data recorded by the Aswan Radio Telemetry Network surrounding the northern part of the lake. The seismicity of the Kalabsha area is divided into six seismic zones and composite focal mechanisms for four zones from these six zones were derived using first motions of P-waves. The mechanisms of these zones are characterized by strike-slip faults. According to the seismicity and focal mechanism solutions new linear features could be added to the structural map of Kalabsha area. Each feature corresponds to an active fault. The P (pressure) and T (tension) axes obtained from the focal mechanisms show that the orientation of the compressional stress and the tensional stress prevailing in the Kalabsha area are ESE-WNW and NNE-SSW, respectively. The direction of the compressional stress agrees with the direction of movement in the area reported by Issawi (1968). The direction of this movement is from SE towards NW. The fold axes mapped in the area generally strike NE-SW. This direction of the fold axes is more or less perpendicular to the compression. It is also consistent with the maximum horizontal compression induced from approximately NW and SE due to the north to northwestward drift of the African plate (Schandelmeier et al., 1987). The direction of the tensional stress is consistent with the presence of E-W faults (e.g. Kalabsha, Seiyal faults). The Wadi Kalabsha may be considered the result of down-faulted blocks with E-W normal faults caused by the NNE-SSW tension.

Active fault and water loading are important factors in triggering earthquake activity around Aswan Lake

Aswan Lake started impounding in 1964 and reached the highest water level so far in 1978 with a capacity of 133.8 km 3, thus forming the second largest man-made lake in the world. An earthquake of magnitude 5.3 (Ms) took place on 14 November 1981 along the most active part of the E-W Kalabsha fault beneath the Kalabsha bay (the largest bay of the lake). This earthquake was followed by a tremendous number of smaller events that continue till now. A radio-telemetry network of 13 seismic short period stations and a piezometer network of six wells were established around the northern part of the lake. Epicenters were found to cluster around active faults near the lake. The space-time distribution and the relation of the seismicity with the lake water level fluctuations were studied. Six years after flooding the eastern segment of the Kalabsha fault, strong seismicity began following the main shock of 14 November 1981. It occurred four days after the reservoir had reached its seasonal max level. The effect of the North African drought (1982 to present) is clearly seen in the reservoir water level. As it decreased and left the most active fault segments uncovered, the activity (Gebel Marawa area) decreased sharply. Also, the shallow activity was found to be more sensitive to rapid discharging than to the filling. This study indicates that geology, topography, lineations in seismicity, offsets in the faults, changes in fault trends and focal mechanisms are closely related. No relation was found between earthquake activity and both-ground water table fluctuations and water temperatures measured in wells located around the Kalabsha area.

Present state of geodynamic properties of Kalabsha area, nortwest of Aswan Lake, Egypt

Aswan Lake is the second largest man-made lake in the world. Its filling started 1964 and reached the maximum water level in 1978. An earthquake of magnitude 5.5 took place in 1981 along the most active fault near the lake (Kalabsha fault). This earthquake was follwed by a tremendous number of smaller events that continue till now. Seismicity and the underground water table around the lake are monitored continuously through a radio-telemetered network. A local geodetic network was established around parts of the active faults in the northwestern part of the High Dam Lake, for monitoring vertical and lateral movements. The Kalabsha local geodetic network (the first one) was established around an active part of the Kalabsha fault in 1983. Precise geodetic measurements have benn carried out twice a year since 1984. On the basis of the repeated geodetic measurements, seismicity of the area and geophysical as well as geological data, the present state of the geodynamical properties of the Kalabsha area is studied. Remarkable horizontal movements were detected; they are correlated with the seismicity of the area and are attributed to the differential loading by the lake. The Kalabsha fault is a right-lateral strike-slip motion on an E-W plane. The magnitude of the movements detected along the fault is variable for the different epochs of measurements and is correlated with both seismicity and water loading in the lake.

Earthquake studies at aswan reservoir

A moderate earthquake occurred in the unpopulated area of Kalabsha in the southeastern part of the Western Desert of Egypt on November 14, 1981. The Kalabsha area lies on a large western embayment of the Aswan Reservoir approximately 60 km south of the Aswan High Dam. The earthquake was the first instrumentally located earthquake in the Aswan region. The earthquake was felt strongly along the Nile River valley. Extensive ground cracking occurred in the desert sands in the epicentral area. Observations of continuing activity with a talemetered network show hypocenters extending to depths of more than 20 km.