الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
During May 2003, the Airborne Geophysics Department of the Nuclear Materials Authority (NMA) of Egypt conducted high resolution magnetic and multi-channel gamma-ray survey covering 1,900 km2 over the G. Gharamul and its surrounding. The gamma-ray spectrometric data was acquired along flight-lines directed at 51o or 231o azimuth degrees and spaced at 250 m. The tie lines spaced at 400 m, acquired along 141o or 321o, orthogonal to the flight lines. The magnetic data was acquired along flight lines spaced at 1000 m and along control lines spaced at 4000 m. Nominal flying elevation was about 100 m (330 ft.) terrain clearance. This mission has been accomplished using the NMA geophysical survey twin-engine Beechcraft King-Air C90 (Turbine engines). This aircraft was equipped with a multi-sensor airborne geophysical survey system. This comprises a Picodas (PDAS-1000) high sensitivity 256-channel gamma-ray spectrometer system and a high resolution Scintrex airborne Cesium-vapour magnetometer.
In this study a correlation between the ground and airborne gamma-ray data has been generated to standardize the airborne gamma ray spectrometric data in the surveyed area. These will provide a mathematical form that can be used to convert the airborne data to the ground data. Also, the
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evaluation and interpretation of the aerial radio spectrometric after standardization and magnetometric survey data acquired over G. Gharamul area and its surrounding is one of targets.
Between 7th October 2012 to 11th October 2012 the field trip was conducted. The ground gamma ray spectrometric survey was carried out along three distributed profiles in the study area. Two of them are traverse lines trending 51º and one tie line trending 141º.
Using the global positioning system was necessary to determine the ground points accurately with the same aircraft coordinate. The time of the measurement at each point was 30 sec to get the reading of potassium, uranium, thorium and total count. GS-512 gamma-ray spectrometer is used during measurements.
By using the airborne and ground spectrometric data along the four profiles a linear relation with zero intercept of the airborne count rates against the ground concentrations has been generated. These relations can be expressed as follows:
K (Ground) =1.8041*K (Airborne)
eU (Ground) =0.4216*eU (Airborne)
eTh (Ground) =0.4521* eTh (Airborne).
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Application of the image display and enhancement techniques available on image processing systems to the gridded geophysical data sets- offered an extremely powerful tool that enabled to overcome the defects of the conventional contour maps. Conversion of the digital multi-channel gamma-ray spectrometric and magnetic survey data to a common image format offered the possibility to combine these data in different ways and to produce some colour composite geophysical images. These images provided extremely useful synthesis of the data. Such images facilitated the spatial correlation of the features in the various data sets, and at the same time displayed variations, which are difficult to be determined on the images of the individual geophysical variables. Four colour composite images for the area under study were produced as follows:
1. Radioelements (K, eU & eTh) composite colour image map (Fig. 40).
2. Equivalent uranium (eU, eU/K & eU/eTh) composite colour image map (Fig. 42).
3. Equivalent Thorium (eTh, eTh/K & eTh/eU) composite colour image map (Fig. 44).
4. Potassium (K, K/eU & K/eTh) composite colour image map (Fig. 46).
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According to the qualitative interpretation of the composite colour image maps, the TC and the absolute three radioactive elements (K, eU, eTh) maps, thirteen Interpreted aerial gamma-ray spectrometric zones are clearly visible (Fig. 41). The studying of the uranium composite image map provides identical five uranium leads, which showed spatial correlation with some of the mapped lithologies in the
Surveyed area as follow:
(i) Uranium Leads No.1a and 1b: are geologically characterized by undifferentiated Quaternary deposits, raised beaches, alluvial fans wadi deposits, sand and gravel.
(ii) Uranium Leads No.2a and 2b: are geologically characterized by crystalline carbonate, algal and reefal limestone and Alkali feldspar granitic rocks.
(iii) Uranium Lead No.3: is geologically characterized by phosphate beds alternating with black shale, marl oyster beds and sandstone.
The interpreted five uranium leads have been evaluated with simple statistics by calculations of the arithmetic mean (X) and the standard deviation (S). The way followed for defining significant eU, eTh and K anomalies is based on identifying
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those areas where eU, eTh and K values are equal or exceed three standard deviations above the mean for single points together with a local enrichment of their ratios (in terms of statistically high eU/eTh, eU/K, eTh/eU, eTh/K, K/eU and K/eTh ratio values).
The total aeromagnetic map was reduced to the north magnetic pole of the earth by applying spectral analysis technique. The reduced to pole (RTP) magnetic map was separated into two magnetic components named the regional and residual magnetic components. The regional magnetic-component map resembles -to a great extent- the aerial RTP magnetic map (Fig. 52). The residual magnetic-component map shows the same general features as the aerial magnetic RTP and regional-component maps. Nevertheless, it can demonstrate more about the magnetic-rock types, their contacts and their over-all relationships including faults, foldings, etc., particularly that located at the near-surface level. The second vertical derivative (SVD) is used in the study area to locate edges of magnetic bodies and to emphasize sources of shallow depths. The estimated mean depths of both the regional and residual magnetic sources were found to be 3800 and 1800 m respectively.
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Two techniques of depth calculations were applied to the aeromagnetic data of the study area. The results of source parameter imaging (SPI) (Thurston and Smith, 1997) and analytical signal (AS) (Roset et al., 1992 & Macloed., 1993) are very closed to each other. At the two depth maps (Figs. 57&58), the central eastern part representing (Umm Ghieg and Shagra formations) and south western part representing (Gabal Zeit) show more shallow depths. The depths of this trend ranging from 970 m to less than 380 m as some of the basaltic sheet appears on the surface as shown on the surface geologic map. The two maps show that the western part and central southern of the area are very deep and has depths ranges from 2000 m to 6000 m which is evidence for a basin. This basin is covered by quaternary deposits.
The Interpreted Magnetic Basement Tectonic Map of G. Gharamul and its surrounding area (Fig. 61) shows that most of deep major faults with trend NW-SE in the majority of the study area except in some areas in the central west and east have trend NE-SW, Part of them supported by surface geological map and extended to surface have trend NW-SE. Additionally, Shallow lineaments have minor trends for lineation at all direction which may be indication that the area is highly dissected. Shallow faults displayed on basement tectonic
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map supported by surface geological map. Correlative study of the interpreted magnetic basement structural maps shows that, the major faults which are demonstrated on the regional map are also well-developed on the residual map.