الفهرس 
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Abstract
The present study area at Wadi El-Regeita is situated at the intersection of Lat. 28° 37 29N and Long. 34° 5 15E, to the northeast of the well-known Saint Katherine mountain. Generally, rocks of this area are belonging to Precambrian basement and represented mainly by younger granites encloses irregular masses in the form of roof pendants and other enclaves of granodiorites, pertaining to an older granitic phase. The younger granites are also intersected by different Cu-mineralized and non-mineralized post-granitic andesite dykes, followed by pegmatite veins. The area - under study - is of considerable geological interest, since the discovery of copper mineralization, in the hosting granites. Besides, it acquired its importance from the later discovery of some radioactive anomalies, related to U mineralization. These copper deposits consist of copper carbonates filling fracture zones, striking NW-SE, in Precambrian igneous rocks. Most of these deposits were mobilized through later hydrothermal activities since they were first deposited. Few geophysical investigations of Cu-mineralization are known. Besides, there is very limited data on the possible association of radioactive minerals, especially U ones, with Cu. For this reason, Wadi El Regeita area was selected for this study, on the basis of known copper mineralization and possibility of an associated uranium one. The specific aims of this study comprise:
(a) Studying the magnetic properties of rocks through the use of magnetic fabric and paleomagnetic methods, in order to shed more light on the origin and possible mode of formation, and identify the effect of alteration on the magnetic properties of these rocks.
(b) Identifying the concentrations of radioactive elements: uranium (U), thorium (Th) and potassium (K), using ground gamma-ray spectrometric method and delineating any possible spatial relation with the observed Cu mineralization.
(c) Following the exposed surface Cu-U mineralization at deeper depths and obtain information about the probable lateral and vertical extensions through the application of the Self-Potential (SP) method.
(d) Use of ground magnetic survey to provide subsurface structural framework, establish the residual and regional (shallow and deep) sources governing the two mineralizations, and interpret the significant trends that affected the study area.
The main results of this study can be summarized as follow: I. LABORATORY MAGNETIC INVESTIGATIONS I.1. Unaltered Younger Granites
AMS results show that these granite are considered as magnetic rocks, reflecting the presence of magnetite as the main ferromagnetic mineral with lesser contents of hematite. AMS was found to be originated through the shape alignment of magnetite grains in younger granites. The magnetic fabric was not obtained after pluton emplacement (primary fabric). AMS results exhibit a well-developed normal „flow‟ magnetic fabric, with steep foliation planes striking in the NE-SW direction and dipping to the NE. The magnetic lineation, on the other hand, is also well-developed, with the maximum susceptibility axes (K1) trending in the NE-SW, with an average plunge of ~46. The average P3 parameter (magnetic foliation) of the younger granites is more than 1.04, which is consistent with that of intrusive rocks. The observed consistent direction of chrM, within and between sites, was considered as a good reason to believe that the magnetization was stable, since time of formation of these granites. This magnetization was acquired over a time period of normal polarity. The relatively high unblocking temperatures of the chrM, with the high stability during demagnetization treatments, indicate that the chrM is most probably of primary origin. Magnetite was regarded as the principal carrier for this magnetization. The corresponding paleomagnetic pole of this magnetization (component-CI) lies at Lat. 6.2N and Long. 314.9E, with A95 = 7.7. This pole seems to be very close to the Precambrian pole. The magnetization of the unaltered younger granites of Wadi El-Regeita area could be interpreted as a primary thermal remanent magnetization (TRM). Thus, the calculated paleomagnetic pole is considered reliable and the present younger granites are still able to record the Precambrian geomagnetic field. I.2. Andesite Dyke As a result of AMS measurements, the andesite dyke is considered as a magnetic rock, reflecting the presence of magnetite as the main ferromagnetic mineral. The AMS was found to be originated through shape alignment of magnetite grains in the andesite dyke. AMS results exhibit a well-developed normal „flow‟ fabrics, with nearly vertical foliation planes, striking in the NW-SE direction. The magnetic lineation, on the other hand, is also well-developed, with the maximum susceptibility axes (K1) tending in the NW-SE and dipping to the SW with an angle ~75. The average P3 parameter (magnetic foliation) of the andesite dyke is more than 1.04, which is consistent with that of rocks of intrusive origin. The magnetic fabric of the mineralized andesite dyke could be interpreted as being primary, related to the original emplacement process through magma flow with subsequent cooling and crystallization under relatively static conditions.
Remanent magnetization, from the andesite dyke, is reasonably well-defined. The observed consistent directions of chrM within and between sites, which indicate the high stability of this magnetization, with the high unblocking temperatures, signify the primary origin. Magnetite was regarded as the principal carrier for this magnetization. The corresponding paleomagnetic pole of this magnetization (component-CII) lies at Lat. 16.3N and Long. 355.9E, with A95 = 2.4. This pole seems to be very close to the Precambrian pole. The magnetization of the mineralized andesite dyke of Wadi El-Regeita area could be interpreted as a primary thermal remanent magnetization (TRM) that was acquired during initial cooling of the rocks. I.3. Altered Granites AMS results show that the mean magnitude of magnetic susceptibility is fairly moderate, which indicate the predominance of hematite as the main magnetic mineral. The degree of anisotropy values decreases with an average of 1.064 due to hydrothermal alterations. The AMS was originated through the crystalline alignment of hematite with the contribution of some paramagnetic minerals (e.g. biotite). The altered granite samples were collected from the granitic walls adjacent to the mineralized andesite dyke, therefore, they were subjected to subsequent wallrock alterations as a result of hydrothermal alterations, which led to partial replacement of magnetite by hematite. This, in turn, led to the absence or lack of AMS regular pattern , which could be summarized and explained. Some sites still retain the original direction of AMS, while other sites were overprinted. The shape of anisotropy, on other hand, oscillates between oblate and prolate. The direction of overall site-mean directions of the principal magnetic susceptibility axes for all sites are scattered, with no preferred orientation. Accordingly, the magnetic fabric of the altered granites could be interpreted as being secondary, related to the effect of NW-SE shear zone and the subsequent alterations due to the effects of repeated hydrothermal solutions.
The chrM (component-CIII) direction is characterized by its high stability and high internal consistency in its respective sites. This magnetization was acquired over a time of normal polarity. Hematite was regarded as the principal carrier for this magnetization. The corresponding paleomagnetic pole lies at Lat. -46.5N and Long. 61.7E, with A95 = 7.4. This pole seems to be very close to the Permo-Triassic pole. This age, most likely, are corresponding to the beginning of alteration processes as a result of hydrothermal solutions and, therefore, the magnetization could also be interpreted as a secondary chemical remanent magnetization (CRM). II. GAMMA-RAY SPECTROMETRY SURVEY The study area possesses a fairly wide range for radiospectrometric measurements both in TC (12 – 149 Ur) and eU (0.3 – 130 ppm). The highest values were spatially associated the Cu mineralization and wall-rock alterations, and mainly along the NW–SE Cu-mineralized shear zone. Away from the area of alteration and Cu-mineralization, the rocks showed relatively low radioactivity levels, where the recorded values for TC and eU fall of to the range of about 0.13 – 35 Ur and 0.3 – 13 ppm, respectively. Consequently, there is a good correlation between TC and eU maps, as concerning the highest and lowest radiospectrometric levels and the distribution of radioactive anomalies, which indicates that the radioactivity in the study area is mainly related to U.
Regarding eTh, the recorded measurements exhibit a relatively wide range (3.0 - 54.0 ppm). The lower eTh values are generally associated with the Wadi sediments, and along the NW–SE andesite dyke, located within the Cu-mineralized shear zone. In terms of the higher eTh values, they are associated, to some extent, with the anomalously high eU parts in the eastern side of the study area and along the Cu-mineralized shear zone. The recorded K concentration values showed a narrow range (0.5 – 9.8%) allover the surveyed area. Away from the relatively high K concentrations related to the mineralized shear zone, which could connected to rock alterations, the recorded values fall within the normal range of granitic. The eU/eTh ratio values range from 0.02 to 10.5. The anomalous parts, with eU/eTh maximum values of 10.5, occur mainly along the NW-SE Cu-mineralized fault zone. The calculated eU/K ratios confirm most of the anomalous eU/eTh parts in the study area and show very high values (up to 30) along the Cu-mineralized shear zone. These observations confirm a strong post-magmatic hydrothermal activities and mobilization in favour of excessive U. The eU-composite image map illustrates that the white light portions (high U anomalies) are mainly associated with Cu-mineralized shear zone. This zone can be interpreted as reflecting good geochemical environment favorable for the formation of U deposits and can, therefore, be used as exploration guides to search for additional surface and subsurface U mineralizations in the surrounding area.
The mineralized fault zone area revealed very high U-Index values, which attain about 32, reflecting intense alteration and mineralization processes. Thus, this zone is considered of high potential and favorable for U exploration. The study Wadi El-Regeita area recorded significant radiospectrometric levels, which were, to a large extent, spatially associated with some Cu-mineralizations along the NW-SE shear zone, located in the eastern part of the study area. Abundance of radioactive elements were independent on differentiation processes, but related to favorable combination of structural conditions and post-magmatic hydrothermal processes, which have clearly altered the rocks and modified their radioactive element concentrations, especially uranium. Therefore, the study area could be considered significant and promising, in view of Cu-U mineralization. III. SELF-POTENTIAL SURVEY The SP measurements exhibit a wide range of amplitudes (-106.7-55.4 mV), with the highest negative values along the Cu-mineralized shear zone. Quantitative interpretation of the SP data, revealed shallow depths to the centers of nine selected anomalies, ranging from 3.3 m to 21.0 m and averaging 11.2 m, while the half-widths of the anomalous bodies range from 8.4 m to 61 m, with a mean value of about 19.2 m. All the anomalies have moderate dips to the SW.
There was a very good agreement in spatial association between the determined eU anomalies (above 37.5 ppm) and the SP anomalies (> - 60 mV), which is directly related to the intensity of Cu mineralization and relevant alterations in the study area. Therefore, spectral gamma-ray measurements can be considered as an effective tool for copper exploration when associated with U mineralization. Based on the results of gamma-ray spectrometry and SP surveys, the study area is of considerable significance, in view of the Cu-U mineralizations, and can be considered as a promising target for exploration in the surrounding areas of comparable geological situation. IV. GROUND MAGNETIC SURVEY The inspection of the power spectrum curve of the study area revealed that the estimated average depths for the deep and shallow magnetic sources attain 44m. and 15m. respectively. The surveyed area could be divided into four zones, depending on their magnetic characters. Two magnetic zones (Z1 and Z4) are located in the western and northeastern parts and represented by high to moderate negative magnetic anomalies, reflecting their acidic sources. The other two magnetic zones (Z2, Z3) are occupy the extreme western and central parts of the study area. They are represented mostly by high positive magnetic anomalies, suggesting that their causative sources possess deep roots and resting over zones of relatively basic composition. The sources of the andesite dykes may be principally related to these zones.
The AS and SPI results revealed that the depths of the mineralized fault zone ranging from 8 m to less than 2 m. The two maps show that the deepest part of the study area are located at western part, with depths reaching to 62m. The general results, as deduced from the rose diagrams, for the interpreted structural lineaments of the three maps (RTP, residual and regional) revealed that two trends are encountered as strong trends (NNE-SSW and NNW-SSE) along all magnetic maps. This means that these trends are represented as shallow and deep ones in the prospect area. Correlating all structural lineament trends, as deduced from radiometric (TC) and magnetic dataset, four significant trends were recorded as major trends (NNW-SSE, NNE-SSW, NE-SW and NW-SE). Therefore, these trends are considered the most significant trends in the study area, from the radiometric and magnetic points of view. Based on the results of present study, the study area is of considerable significance, in view of the Cu-U mineralization. Therefore, it is recommended that other geophysical techniques of deep penetration (as electromagnetic and/or induced polarization methods) are conducted in the locations of the strong negative SP anomalies, and to the SW of the Cu-mineralized shear zone. These methods will, in turn, confirm the presence of mineralization source, explore the mineralization extensions in deeper depths, and perform adequate information for the drilling processes in the future.