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Ground follow-up of the airborne gamma-ray spectrometric survey data, ramlet HOMAYYER area, east abu-zeneima, southwestern Sinai, Egypt
Applied Radiation and Isotopes 151 (2019) 129–139
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Ground follow-up of the airborne gamma-ray spectrometric survey data, ramlet HOMAYYER area, east abu-zeneima, southwestern Sinai, Egypt
T
Sayed A. Alkhateeb, Adly A. Hossny, Abdallah S. Ashami, Mostafa A.M. Zaeimah∗ Nuclear Materials Authority, Cairo, Egypt
HIGHLIGHTS
total-count (T.C.) values vary widely from 3.4 Ur to 101.3 Ur. • The equivalent thorium (eTh) content value reaching about 68.9 ppm. • The equivalent uranium (eU) content attains its maximum value reaching about 84.0 ppm. • The • Some elements as: Y, Cr, W, Sr and Ag, which gives 6819,768,314,561 and15 ppm respectively. ABSTRACT
Ramlet Homayyer area is located in the southwestern part of Sinai Peninsula, Egypt, to the east of Abu-Zeneima city, located on the eastern coast of Gulf of Suez, Red Sea. The Paleozoic succession in the study area (up to 300 m thick) overlies the basement complex and is covered by basaltic sheets. The lithologic nature of the Paleozoic rocks played a very important role in the localization of various mineralizations (e.g. Mn, Fe, Cu, REEs, Th … etc.) In the present study of Ramlet Homayyer area, ground spectral gamma-ray survey was conducted along N-S profiles, equally-spaced, with lengths of about 2.5 km, and the total area equals about 10 km2. The measurements were conducted using a portable gamma-ray spectrometer, model GS-512. The examination of the totalcount (T.C.) radiometric contour map shows that the radioactivity values vary widely from 3.4 Ur to 101.3 Ur. The potassium (K) content in Ramlet Homayyer area ranges from 1.2% to 16.0%. The equivalent thorium (eTh) content in the study area has a maximum value reaching about 68.9 ppm. The equivalent uranium (eU) content attains its maximum value reaching about 84.0 ppm. Factor analysis technique, which provides a way of thinking about radiospectrometric elements and ratio interrelationships alltogether was carried out. The application of factor analysis technique, helped to delineate the zones of high concentrations of eU, eTh and K separately, where the first factor (F1) can delineate high eU zones, (F2) high eTh zones and (F3) high K zones. The radiometric lithologic mapping was conducted for the whole area, by testing the homogeneity of all measurements recorded indicates that the distribution of the radioactivity all over the area is not homogeneous. This indicates that the lithological cover of the study area cannot be considered as one lithologic unit, but contains different types of rock units. Each Interpreted radiometric lithologic units (IRLU) is corresponding to one geomorphological mass or features. As a result of the ground radiometric survey of the study area, chemical analyses for some selected samples were taken and conducted from the anomalous zones at G. Homayyer, G. Ghorabi and Khameila areas. These analyses showed presence of concentrations of uranium up to 147 ppm, 58 ppm, 52 ppm in addition to trace elements with high concentrations of some elements as: Y, Cr, W, Sr and Ag, which gives 6819,768,314,561 and15 ppm respectively.
1. Inroduction The Sinai Peninsula of Egypt covers an area of about 61,000 km2. It has a triangular shape and is bounded the Suez Canal and Gulf of Suez from the west, Gulf of Aqaba from the east, Mediterranean Sea from the north and Red Sea from the south. Ramlet Homayyer area is located in the southwestern part of Sinai Peninsula, to the east of Abu-Zeneima town on the eastern coast of Gulf of Suez, Egypt (Fig. 1). The study area is mainly covered by sedimentary rocks of Phanerozoic Eon. The Paleozoic rocks in Southwestern Sinai attracted the attention of many
∗
authors, since the Pharaohs time by exploiting copper, discovery of manganese-iron ore, and finding of radioactive anomalies, till the identification of secondary uranium mineralization. An airborne geophysical survey for Southwestern Sinai were carried out by Nuclear Materials Authority (NMA) of Egypt in 1966 and 1998 respectively. They involved total count radiometric and gamma-ray spectrometric surveys, which led to the discovery of some important occurrences of radioactive mineralizations. The processing of these data identified many zones, which needed further verification and ground geophysical follow-up (Fig. 2). Accordingly, Ramlet Homayyer area was
Corresponding author. E-mail address: [email protected] (M.A.M. Zaeimah).
https://doi.org/10.1016/j.apradiso.2019.05.036 Received 12 March 2019; Received in revised form 13 May 2019; Accepted 26 May 2019 Available online 01 June 2019 0969-8043/ © 2019 Published by Elsevier Ltd.
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Fig. 1. Location map of the Ramlet Homayyer area, and the Geomorhological features of the region according to Earth Google East Abu-Zeneima city, Southwestern Sinai, Egypt.
This may be done in a systematic manner on a grid pattern for both prospecting and mapping purposes (IAEA, 1979).
selected as a promising target for uranium potentiality. Hence, ground geophysical follow-up survey was applied to this area. This survey includes ground gamma-ray spectrometry and others.
3. Instrumentation
1.1. Regional geology
Spectral gamma-ray measurements were conducted using a portable gamma-ray spectrometer, model GS-512, manufactured by Geofyzika Brno, Czeck Republic. The spectrometer was calibrated using the locally-constructed transportable concrete calibration pads of the Nuclear Materials Authority of Egypt.
The exposures of Ramlet Homayyer area and its surroundings range from Precambrian to Quaternary (Fig. 3). The Precambrian comprises granodiorites and granites. The Paleozoic rocks comprise seven formations from top to base Abu-Zarab, Magharet El-Maiah, El-Hashash, Um-Bogma, Adedia, Abu-Hamata and Sarabit El Khadim. The Mesozoic rocks are represented by Triassic and Jurassic basaltic sheets and dykes. Besides, Upper Cretaceous and Eocene rocks are exposed near the study area. The unconformity surfaces were recorded between Um-Bogma formation and other lower and upper formations (Soliman and Abu ElFetouh, 1969, Alshami, 2003). The exposed rock types in Ramlet Homayyer area (Fig. 4) are related to the Paleozoic, except Farsh Elazrag volcanic which are related to Triassic-Early Jurassic. The main rock types are sandstones, siltstones, shales, conglomerates and basalt (Fig. 4). In this area, the basement rocks are mainly covered by El-Adedia Formation in its northwestern part, at Ramlet Homayyer. In some other localities, Adedia Formation are overlain by black shales equivalent to Um-Bogma Formation, as well as Abu-Thora Formation e.g. at Ramlet Homayyer and Gabal Ghorabi.
4. Field procedure In the present study, ground spectral gamma-ray survey was conducted along 100 profiles, directed N-S, with an average length of 2.5 km, to cover a surface area reaching nearly 10 km2. The distances between the survey profiles ranged from 20 m to 50 m, according to the importance and topography of the area, while the interval between the stations were 20 m perpendicular to the strike of the general geologic trend of the area. The obtained data were reduced and represented as coloured contour maps. 5. Interpretation of the results 5.1. Qualitative interpretation
2. Ground radiospectrometric survey
The surface concentrations of the radioelements: potassium, uranium and thorium, can be qualified by measurements of the intensities of gamma radiation emitted by their respective radioisotopes 40K, 214Bi and 208Tl. Ground gamma-ray spectrometry is commonly used to make such measurements, which can be related to surface concentrations by appropriate calibration procedures. Such data are then used to compile maps showing the surficial distributions of these three radioelements and their binary ratios. The relationship between the average surface radiometric concentrations and the radioelement concentrations in subsurface bedrock depends on the surface area of the outcrop, the relation between overburden and bedrock radioelement concentrations, the percentage of marshland or surface ware in the area, soil moisture and density of vegetation (Charbonneau et al., 1976). Data of the measured gamma-ray spectrometric parameters (T.C., K, eU and eTh) were finally displayed in the form of coloured contour maps (Figs. 5–11).
All common rock types and their related soils contain significant amounts of radioactive elements (radioelements). The presence of these radioelements is apparent in any gamma-ray survey, irrespective of whether or not the purpose of the survey to map their distribution in the natural environment. In practice, at least in the early stages of exploration, it is usually advisable to map the radioactivity data, because small abnormalities may provide the first clue pointing towards an enrichment of radioactive elements, such as uranium and thorium (IAEA, 1979). The main objectives of gamma-ray spectrometric survey are to locate anomalous gamma radiation fields and determine the nature and concentration of the radioisotopes, which give rise to them. The gamma-ray spectrometric survey technique is simply to move the appropriate spectrometer system across (or through) the area of interest. 130
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Fig. 2. Total-Count radiometric map of Abu-Zeneima/Al-Tur area, Southwestern Sinai, Egypt (NMA, 1999).
The qualitative interpretation of the ground γ-ray radiometric survey data is mainly concerned with the visual examination of the colour contour maps of the measured radioelement concentrations as well as the total-count radioactivity. This examination aims to classify
the study area into zones, based on the contrasts in their spectral γ-ray emission response levels. Visual examination of the gamma-ray spectrometric filled-colour contour maps indicates three outlined radio-spectrometric zones: low, 131
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Fig. 3. Regional geological map of Ramlet Homayyer area, Southwestern Sinai, Egypt.
intermediate and high.
(lowest T.C.) to light violet (highest T.C.) to help data interpretation. These three relative zones of radioactivity could be described in the following. The low radioactivity level is encountered at the northwestern part of the study area, and coincides with Wadi Khameila, which has a northwest trend. This level is discrimenated by false blue colour (Fig. 5), and varies in T.C. radiometric intensity from 1.0 to 10.0 Ur. The intermediate radioactivity level is recorded over Adadia Fm. It has false green, yellow and orange colours (Fig. 5), and ranges in T.C. radioactivity from 10 Ur to 20 Ur. The high radioactivity level extends over some parts of Adadia, Um-Bugma., Magharet Elmiah. and AbuZarab formations. It is represented by an elongated and rouned anomalous zones located in the southern, centeral and northeastern parts of the study area. These anomalous zones, as a whole, are elongated in the NW, NE and N-S directions. It has false red and violet colours (Fig. 5), and ranges in radioactivity from 20 Ur to mor than 58 Ur. There are some very high spots representing real anomalies, that are shown on (Fig. 5) and reached 140.2, 177.5, 183.4, 198.5, 374.8 Ur.
5.2. Total-count (T.C.) radiometric data The examination of the false-colour total-count (T.C.) radiometric contour map (Fig. 5) shows that the radioactivity values vary widely from 1.0 Ur to 58.6 Ur. Some of the delineated high radiometric anomalies are circular in shape and others are elongated in various directions. They are roughly parallel to the Gulf of Suez (NNW), Gulf of Aqaba (N-S) and Red Sea (NW) trends. The very high levels of radioactivity are nearly associated with Um-Bogma Fm. The high levels are associated with Adadia and Um-Bugma formations. The lowest T.C. radiometric levels are connected with Wadi Ghamela. The intermediate T.C. radioactivity level is common through the remaining surface of the study area. The Total-Count (T.C.) radiometric filled colour contour map (Fig. 5) was classified into three main relative zones, ranging from blue
Fig. 4. Detailed geological map of Ramlet Homayyer area, Southwestern Sinai, Egypt. 132
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Fig. 5. Ground filled-colour total-count contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
5.3. Potassium (K) radiospectrometric data
5.4. Equivalent thorium (eTh) data
The potassium (K) content in ramlet Homayyer area ranges from 1.0% to 16.0%. The false-colour potassium (K) contour map (Fig. 6) was divided into three main relative zones that change in false colour from blue (low intensity), green, yellow and orange (intermediate intensity) to red and violet (high intensity). The low K level has a false blue colour and is encountered as scattered spots allover Ramlet Homayyer area. It ranges in K intensity from 1.0% to 2%. The intermediate K level has vast areal extent on the entire Ramlet Homayyer area, and is elongated in NW and NE directions. This level was false coloured in green, yellow and orange. It varies in K intensity from 2% to 4%. The high K level is mainly associated with Adadia Formation. The contours of this level are mainly elongated, and extend in both the NW and NE directions. This level was false coloured in red and violet and varies in K intensity from 4% to more than 7.0%.
The equivalent thorium (eTh) content in the study area has a maximum value reaching about 57.3 ppm. Some of the delineated high eTh anomalies are circular in shape and others are elongated in the NW and NNW directions (Fig. 7). The minimum eTh values reach 1.0 ppm and are corelated with Wadi Ghamela. The false-coloured eTh contour map could be classified into three remarkable and relative zones ranging in intensity from less than 10.0 ppm to more than 40.0 ppm, and in false colour from blue (low intensity) to violet (high intensity). The low eTh zone is encountered at the southwestern part of the study area, coinciding with Wadi Ghamela, and the northwestern parts of the study area. This level is distinguished by false blue colour (Fig. 7), and varies in eTh intensity from 9.2 ppm to 15 ppm. The intermediate eTh zone is observed at scatered parts along the study area. This zone is false-coloured by green, dark and light yellow (Fig. 7) and varies in eTh
Fig. 6. Ground filled-colour potassium (K) contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) 133
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Fig. 7. Ground filled-colour equivalent thorium (eTh) contour map of Ramlet Homayyer area Southwestern Sinai, Egypt. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
intensity from 15 ppm to 20 ppm. The high eTh zone extends over some parts of Adadia Fm., Um-Bugma Fm. and Magharet Elmiah Fm. It is represented by elongated and rounded anomalous zones, located in the southern, centeral and northeastern parts of the study area. These zones have NW, NE and N-S directions. They are false-coloured by red and violet (Fig. 7), and range in intensity from 20 ppm to mor than 68.9 ppm.
three remarkable and relative levels ranging in intensity from 1.0 ppm eU to more than 80 ppm eU and in false-colour from blue (low intensity) to violet (high intensity). This division helped much in the interpretation of the eU radiospectrometric survey data. The low eU zone is encountered as an elongated shape, coincides with Wadi Ghamela and the northwestern part of the area under study. This level is false-coloured by blue (Fig. 8), and varies in eU intensity from 1.0 ppm to 5.0 ppm. The intermediate eU zone appears along great parts, mainly at the eastern side of the area under investigation. This zone is false-coloured by green, dark and light yellow (Fig. 8) and varies in eU intensity from 5.0 ppm to 15.0 ppm. The high eU zone extends over a small portion of Ramlet Homayyer area. It is represented by an elongated zone located in the northeastern part of the study area, beside another smaller one to its south. These two zones concide with Um-Bugma, Magharet Elmiah
5.5. Equivalent uranium (eU) data The equivalent uranium (eU) content attains its maximum value reaching about 51.0 ppm at the central southern part of the study area (Fig. 8). The minimum eU value, reaching 1.0 ppm is situated at Wadi Ghamela. The average value of eU in the study area attains about 3.4 ppm. The eU false-coloured contour map can be distinguished into
Fig. 8. Ground filled-colour equivalent uranium (eU) contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) 134
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Fig. 9. Ground filled-colour eU/eTh ratio contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. . (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
Fig. 10. Ground filled-colour eTh/K ratio contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. . (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
and Abuzarab Fms. They are false-coloured by red to violet (Fig. 8) and vary in their eU intensity from 15.0 ppm to more than 85.0 ppm. There are some other point anomalies shown on (Fig. 8), reaching 129.9167.2, 172.5, 184.8, 346.4 ppm.
anomalous zones of this ratio are concentrated at Um-Bugma Fm., where their values range from 1.0 ppm to 5.2 ppm and the highest anomaly of eU/eTh ratio is recorded over Um-Bugma Fm. The lowest anomaly of eU/eTh ratio is recorded over Adadia Fm. at Gabal El-sania. The relatively low eU/eTh ratio zone is encountered at Adadia Fm. This level is false-coloured by blue and green (Fig. 9), and varies in eU/eTh ratio intensity from 0.2 to 0.8. The intermediate eU/eTh zone is encountered at Wadi Ghamela and the northwestern parts of Ramlet Homayyer loose sands. This zone is false-coloured by dark and light yellow (Fig. 9) and varies in eU/eTh ratio intensity from 0.8 to 1.0. The high eU/eTh ratio zone extends over small part of Ramlet Homayyer area. They are represented by elongated zones located in the northeastern part of the area, beside a small one to its south. This zone reflects the outcrop of Um-Bugma, Magharet Elmiah and Abuzarab Fms.
5.6. eU/eTh ratio The eU/eTh ratio is important for uranium exploration, because it determines the uranium-enriched areas. The eU/eTh contour map (Fig. 9) confirms the presence of very high eU/eTh ratio zones, reflecting increased eU superimposed on eTh intensity values. These anomalies may have been produced by solutions, highly enriched in uranium, which have permitted the mobilization and the concentration of uranium. The eU/eTh ratio contour map (Fig. 9) shows that the 135
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They are false-coloured by red to violet (Fig. 9) and vary in intensity from 1.0 to mor than 4.0.
0.3 to 3. The intermediate eU/K ratio zone is false-coloured by dark and light yellow (Fig. 11). The high eU/K zone extends over a small portion of Ramlet Homayyer area. It is represented by an elongated zone, located in the northeastern part of the study area, beside a small one to its south. This zone extends over Um-Bugma, Magharet Elmiah and Abuzarab formations. It is false-coloured by red to violet (Fig. 11) and varies in eU/K ratio intensity from 6.0 to more than 29.0.
5.7. eTh/K ratio The eTh/K ratio in the study area attains its maximum value reaching about 25, which is associated with Magaret Elmiah Fm. Some of the delineated high radiometric anomalies are circular in shape and others are elongated. They are roughly parallel to the Gulf of Suze, Gulf of Aqba and Red Sea trends NW - SE, and N-S direction (Fig. 10). The minimum eTh/K ratio value reaching 1.4 is situated in Wadi Ghamela and Ramlet Homayyer loose sands. The eTh/K ratio contour map (Fig. 10) could be classified into three remarkable and relative zones, ranging in intensity from less than 0.6 to more than 25.0, and in false-colour from blue (low intensity) to violet (high intensity). The low eTh/K ratio elongated zone is encountered at the southwestern part of the study area, and coincides with Wadi Khameila and its north western part and, Ramlet Homayyer loose sands. This level is false-coloured by blue and green (Fig. 10), and varies in eTh/K ratio intensities from 1.4 to 3.0. The intermediate eTh/K zone is false-coloured by dark and light yellow (Fig. 10) and varies in eTh/K ratio intensities from 3.0 to 4.0. The high eTh/K ratio zone extends over some parts of Adadia, Um-Bugma, and Magaret Elmiah formations. They are represented by elongated and rounded anomaly zones, located in the southern and central parts of the study area. These anomalies as a whole are arranged in NW, NE and N-S directional trends. They are false-coloured by red to violet (Fig. 10) and vary in eTh/K intensities from 3.0 to more than 25.0.
5.9. Quantitative interpretation The results of the gamma-ray spectrometric survey data acquired over the investigated area were quantified through the application of some appropriate statistical analysis techniques. These techniques include conventional standard statistics as well as factor analysis. Detailed gamma-ray spectrometric data (T.C., K, eU and eTh) were plotted for the detailed-survey area. The three ratios eU/eTh, eU/K and eTh/K were calculated on the basis that null values are inserted in places where K is less than 0.01%. A composite data file was prepared to include the 7 variables (T.C., K, eU, eTh, eU/eTh, eU/K and eTh/K). The number of valid calculated data points per variable was 11229 points. Conventional standard statistics were applied to the data to compute their arithmetic means ( X ) and standard deviations (S) for each variable (Table 1) for the whole study area. The correlation coefficient (r) matrix (Table 2) shows positive (direct) correlations between T.C. and five variables (K, eU, eTh, eU/K, and eTh/K), which attain values of 0.10, 0.82, 0.76, 0.72 and 0.68 respectively. Meanwhile, there is no correlation between T.C. and eU/ eTh, where the critical correlation coefficient (rc) attains 0.06 at the 95% level of confidence. The correlation between K and the other five variables (eU, eTh, eU/ eTh, eU/K and eTh/K) are all negative (indirect) except eTh (direct) with values of −0.13, 0.08, −0.22, −0.34 and −0.30 respectively (Table 2). The correlation between eU and the other four variables are all positive (direct) and significant with values of 0.52, 0.42, 0.96 and 0.56 respectively (Table 2). Meanwhile, the correlation between eTh and the other two ratios (eU/K and eTh/K) are positive (direct) with values of 0.46 and 0.90 respectively, but it is negative (indirect) with eU/eTh and reaches −0.39 in value (Table .2). The eU/eTh ratio shows direct correlation with the eU/K ratio (0.44) and indirect correlation with the eTh/K (−0.27). Finally, the correlation between eU/K and
5.8. eU/K ratio The eU/K ratio attains its maximum value reaching about 29.0 at the central southern part of the study area (Fig. 11). The minimum eU/ K value, reaching 0.7 is situated at Wadi Ghamela.The eU/K ratio contour map can be separated into three remarkable and relative zones ranging in intensity from 0.3 to more than 29.0 and in false-colour from blue (low intensity) to violet (high intensity). The low eU/K ratio zone is encountered as an elongated shape that coincides with Wadi Ghamela and the northwestern parts of the area under study. This level is coloured by blue and green (Fig. 11), and varies in eU/K intensity from
Fig. 11. Ground filled-colour eU/K ratio contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. . (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) 136
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Table 1 Descriptive statistics of the ground gamma-ray spectrometric survey data of Ramlet Homayyer area, East Abu-Zeneima, Southwestern Sinai, Egypt. Variable
N
Min. value
Max. value
Range
Mean ( X¯ )
Std. Dev. (S)
T.C. (Ur) K (%) eU (ppm) eTh (ppm) eU/eTh eTh/K eU/K
11229 11229 11229 11229 11229 11229 11229
1.0 1.0 1.0 1.0 0.1 0.6 0.3
58.6 16.1 51.9 57.3 5.2 30.2 34.6
57.6 15.1 50.9 56.3 5.1 29.6 34.3
7.534 1.983 3.447 6.636 0.587 3.623 1.932
3.842 0.754 2.233 3.907 0.292 2.443 1.515
Table 3 Unrotated factor matrix of the seven variables of ground gamma-ray spectrometric survey data, Ramlet Homayyer area, East Abu-Zeneima, Southwestern Sinai, Egypt. Variables
Eigen value % of total variance Cumulative % T.C. (Ur) K (%) eU (ppm) eTh (ppm) eU/eTh eU/K eTh/K
eTh/K is direct reaching 0.61, where the critical correlation coefficient (rc) attains 0.06 at the 95% level of confidence. Factor analysis is a multivariate statistical technique, whereby the number of variables is reduced to the minimum number of independent variables, which will describe the data. Various methods of factor analysis were derived, by which the relationships, between variables and the relationships between samples could be determined (Duval, 1976). Instead of discussing the correlations between these seven variables in detail, factor analysis technique which provides a way of thinking about these interrelationships alltogether was carried out. The matrix shown on (Table 2) was used to get the “Unrotated matrix” indicated on Table (3), coupled with extracting Eigen values and their cumulative percent. Factor loadings of the variables are effective on the first three at the 95% level of confidence unrotated factors F1, F2 and F3, while they are not effective on the four remaining factors (F4 to F7) (Table 3). The highest factor is F1 in sense that the weight of the factor loading reaches 54.70, while the squint factors (F2 and F3) become progressively smaller attaining 25.41 and 15.20 respectively (Table 3). These unrotated factors are rarely useful in scientific work, so it is possible to “rotate” this unrotated factor matrix into another form that is mathematically equivalent to the original unrotated matrix using varimax method (Comery, 1967). The 7-dimensional factor space can be reduced without significant loss of information into three dimensions of space (principal factors). These three principal factors are quite interpretable and represent 95% of the total system of information, which is sufficient to interpret the available data. Table (4) shows the three principal factors F1, F2, and F3 as extracted from (Table 3). They are rotated using varimax method. It can be concluded, from Table 4 that the first factor (F1) shows appreciably high positive loadings with four variables T.C., eU, eU/K and eU/eTh reaching 80%, 97%, 93% and 57%, respectively and low positive loadings with eTh and eTh/K with values of 42% and 46%, respectively. F1 exhibits an inverse low loading with K as a negative value of (−8%). The F1 factor for these reasons is very identical with the total-count radiometric and uranium maps. Therefore, this can be mainly used for uranium exploration. Consequently, F1 can be identified as the factor of integrated radioactivity or uranium exploration factor (Moustafa et al., 1990) (see Table 5). The second factor (F2) is high and positively (directly) loaded with
Factor F1
F2
F3
F4
F5
F6
F7
3.83 54.70 54.70 0.90 −0.19 0.90 0.80 0.12 0.89 0.85
1.78 25.41 80.11 −0.11 −0.43 0.33 −0.57 0.93 0.41 −0.35
1.06 15.20 95.31 0.29 0.87 0.21 −0.02 0.23 −0.01 −0.35
0.16 2.24 97.55
0.14 1.93 99.48
0.03 0.41 99.89
0.01 0.11 100.00
Table 4 Loadings of factors (varimax rotated) of the ground gamma-ray spectrometric survey data, Ramlet Homayyer area, East Abu-Zeneima, Southern Sinai, Egypt. Variable
T.C. (Ur) K (%) eU (ppm) eTh (ppm) eU/eTh eU/K eTh/K
Rotated Factor F1
F2
F3
0.80 −0.08 0.97 0.42 0.57 0.93 0.46
0.48 0.02 0.14 0.88 −0.75 0.13 0.82
0.19 0.99 −0.05 0.09 −0.17 −0.29 −0.30
eTh and eTh/K reaching 88% and 82%, respectively. Meanwhile, it is positive and weakly loaded with T.C., eU and eU/K reaching 48%, 14% and 13%, respectively (Table 4). In the same time, it is very weakly loaded with K attaining only 2%. Meanwhile, it is highly and inversely (indirect) loading with eU/eTh ratio attaining −75%, (Table 4). The third factor (F3) shows high and positive (direct) loading with K only, attaining 99%. It displays positive and low loadings with T.C. and eTh reaching 19%, and 9%, respectively. Meanwhile, it is inversely (indirectly) and weakly loaded with four variables (eU, eU/K, eTh/K and eU/eTh) reaching −5%, −29%, −30% and −17%, respectively. These standard factor scores can characterize different radiolithologic units in the study area. The results obtained from the application of factor analysis technique show that, it is possible to delineate the zones of high concentrations of eU, eTh and K separately, where F1 can delineate high eU values, F2 high eTh values and F3 high K values. 5.10. Interpreted radiometric lithologic units (IRLU) The radiometric lithologic mapping was conducted for the whole area, by testing the homogeneity of measurements recorded over the
Table 2 Matrix of correlation coefficients, conducted between the seven radiospectrometric data variables, Ramlet Homayyer area, East Abu-Zeneima, Southwestern Sinai, Egypt. Variables
T.C. (Ur)
K (%)
eU (ppm)
eTh (ppm)
eU/eTh
eU/K
eTh/K
T.C. (Ur) K (%) eU (ppm) eTh (ppm) eU/eTh eU/K eTh/K
1.00 0.10 0.82 0.76 0.06 0.72 0.68
1.00 −0.13 0.08 −0.22 −0.34 −0.30
1.00 0.52 0.42 0.96 0.56
1.00 −0.39 0.46 0.90
1.00 0.44 −0.27
1.00 0.61
1.00
Critical correlation coefficient (rc) = 0.06 95% level of confidence. 137
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Wadi deposits by 3 IRLU units (4, 5 and 6), Abu- Zarab Formation by one IRLU units (No.11), upper sandstone Magaret Elmiah Formation by IRLU (12, 12–1, 12–2, 12–3 and 12–4), middle carbonate Um- Bogma Formation by 3 IRLU units (1, 2, and 3), lower sandstone Adedia Formation by four IRLU (7, 8, 9 and 10). As a result of the ground spectrometric survey of the study area, chemical analyses were carried out for some selected samples that were collected from the anomalous zones at G. Homayyer, G. Ghorabi and Khameila areas. These analyses showed presence of concentrations of uranium up to 147 ppm, 58 ppm, 52 ppm in addition to the existence of trace elements with high concentrations in some elements as: Y, W, Sr and Ag, which yielded 6819,314,561 and15 ppm respectively (Alshami, 2018 b, in press).
Table 5 Chemical composition of representative samples at Gabal Homayyer, Ghorabi, Khameila localities of the study area. Oxides
Km
Gh-1
Gh-2
SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 H2O S Cl V Co Ni Cu Zn Pb Ag As Sb W Sr Ba Y Zr Nb Th U
79.25 1.10 7.20 6.45 0.06 0.49 2.61 0.06 0.01 0.95 0.50 0.1593 171 151 120 255 30 0 57 15 71 4 314 561 342 6819 618 216 10 147
84.37 0.27 8.27 4.69 0.01 0.45 0.67 0.10 0.03 0.31 0.45 0.0559 487 60 27 58 21 0 73 10 30 7 85 281 32 1402 180 44 4 58
84.69 0.27 8.13 4.65 0.01 0.45 0.68 0.08 0.01 0.31 0.31 0.0465 464 48 40 60 21 0 78 4 28 10 53 282 27 1407 187 45 4 52
6. Summary and conclusions In the present study of Ramlet Homayyer area, ground spectral gamma-ray survey was conducted along N-S parallel, equally-spaced profiles, with lengths of about 2.5 km, and a total surface area equal about 10 km2. The measurements were conducted using a portable gamma-ray spectrometer, model GS-512. The examination of the total-count (T.C.) radiometric contour map shows that the radioactivity values vary widely from 3.4 Ur to 101.3 Ur. The potassium content ranges from 1.2% to more than 7.0%. The equivalent thorium content has a maximum value reaching about 68.9 ppm. The equivalent uranium content attains its maximum value reaching about 84.0 ppm. Factor analysis technique which provides a way of thinking about radiospectrometric elements and ratio interrelationships, all together was carried out. The application of factor analysis technique, helped to delineate zones of high concentrations of eU, eTh and K separately, where the first factor (F1) can delineate high eU zones, (F2) high eTh zones and (F3) high K zones. The radiospectrometric lithologic mapping was conducted for the whole area, by testing the homogeneity of measurements recorded over the study area as a whole. This indicates that the distribution of the radioactivity all over the area is not homogeneous. This indicates that the lithological cover of the study area cannot be considered as one lithologic unit, but contains different types of rock units. Each IRLU is corresponding to one geomorphological mass or feature. As a result of the ground spectrometric survey of the study area chemical analyses were conducted for some selected samples that were collected from the anomalous zones at G. Homayyer, G. Ghorabi and Khameila areas. These analyses showed the presence of concentrations of uranium up to 147 ppm, 58 ppm, 52 ppm in addition to presence of
study area as a whole which indicates that the distribution of the radioactivity all over the area is not homogeneous. This indicates that the lithological cover of the study area cannot be considered as one lithologic unit, but contains different types of rock units. Each IRLU is corresponding to one geomorphological mass or features. Fig. 12 indicates that the study area is covered by interpreted radio-lithologic (IRLU) units, in addition to the values which were deviated from normal distributions (coloured points). Fig. 13 shows the correlation diagram of the computed (T.C.) statistical parameters of (IRLU). The detailed geological map (Fig. 4) of the study area contains five lithological units: Wadi deposits, Abu-Zarab Formation, upper sandstone Magaret Elmiah Formation, middle carbonate Um- Bogma Formation, and lower sandstone Adedia Formation, arranged from top to bottom. Each of these rock types are represented by one or more IRLU units.
Fig. 12. Interpreted radiometric lithologic unit (IRLU) map of, Ramlet Homayyer area, Southwestern Sinai, Egypt. 138
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Fig. 13. The correlation diagram of the computed (T.C.) statistical parameters of (IRLU), Ramlet Homayyer area, Southwestern Sinai, Egypt.
trace elements with high concentrations of some elements such as: Y, Cr, W, Sr and Ag, which yielded 6819,768,314,561 and15 ppm respectively. On the other hand, the study area needs more detailed geophysical studies (electric tools) to follow the shape of anomalous lenses and horizons at the subsurface.
Gamma-Ray Spectrometer Measurements over the Canadian Shield. IAEA Symposium on Exploration for Uranium Ore Deposits, Vienna, Austria, 1976. STI/PUB/434, pp. 35–53 IAEA-SM-208/3. Comery, A.L., 1967. A First Course in Factor Analysis. Academic Press, New York, pp. 316p. Duval, J.S., 1976. Statistical interpretation of airborne gamma ray spectrometric data using factor analysis. In: Proceedings of a Symposium on Exploration of Uranium Ore Deposits, Vienna, IAEA. SM. 208/12. GS-512, Manufactured by Geofyzika Brno, Czeck Republic. International Atomic Energy Agency "IAEA", 1979. Gamma-ray Surveys in Uranium Exploration. IAEA Technical Report Series No. 186. pp. 90 Vienna, Austria. Moustafa, M.E., Rabie, S.I., Elrakaiby, M.L., 1990. Rock Unit Mapping Using Factorial Analysis Applied to Airborne Gamma-Ray Spectrometric Data, West G. Gattar Area, Eastern Desert of Egypt. Annals of the Egypt, Geol. Survey and Mining Authority (EGSMA). (Cairo, Egypt). NMA Internal Scientific Report, 1999. Study of Abu Zinima rea, South Sinai, Egypt. Soliman, M.S., Abu El-Fetouh, M.A., 1969. Petrology of carboniferous sandstone in west central Sinai. J. Geol. UAR 13, 61 43.
References Alshami, A.S., 2003. Structural and Lithologic Controls of Uranium and Copper Mineralization in Um Bogma Environs, South Western Sinai, Egypt. Ph.D. Thesis. Faculty of Science, Mansoura University, Egypt, pp. 148p. Alshami, A.S., 2018 b b. INFRA-CAMBRIAN PLACER GOLD-URANIFEROUS PALEOZOIC SEDIMENTS, SOUTHWESTERN SINAI. EGYPTScientific Society of Nuclear Materials Authority (in press). Charbonneau, B.W., Killeen, P.G., Carson, J.M., Cameron, G.W., Richardson, K.A., 1976. In: The Significance of Radioelements Concentration Measurements Made by
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Ground follow-up of the airborne gamma-ray spectrometric survey data, ramlet HOMAYYER area, east abu-zeneima, southwestern Sinai, Egypt
T
Sayed A. Alkhateeb, Adly A. Hossny, Abdallah S. Ashami, Mostafa A.M. Zaeimah∗ Nuclear Materials Authority, Cairo, Egypt
HIGHLIGHTS
total-count (T.C.) values vary widely from 3.4 Ur to 101.3 Ur. • The equivalent thorium (eTh) content value reaching about 68.9 ppm. • The equivalent uranium (eU) content attains its maximum value reaching about 84.0 ppm. • The • Some elements as: Y, Cr, W, Sr and Ag, which gives 6819,768,314,561 and15 ppm respectively. ABSTRACT
Ramlet Homayyer area is located in the southwestern part of Sinai Peninsula, Egypt, to the east of Abu-Zeneima city, located on the eastern coast of Gulf of Suez, Red Sea. The Paleozoic succession in the study area (up to 300 m thick) overlies the basement complex and is covered by basaltic sheets. The lithologic nature of the Paleozoic rocks played a very important role in the localization of various mineralizations (e.g. Mn, Fe, Cu, REEs, Th … etc.) In the present study of Ramlet Homayyer area, ground spectral gamma-ray survey was conducted along N-S profiles, equally-spaced, with lengths of about 2.5 km, and the total area equals about 10 km2. The measurements were conducted using a portable gamma-ray spectrometer, model GS-512. The examination of the totalcount (T.C.) radiometric contour map shows that the radioactivity values vary widely from 3.4 Ur to 101.3 Ur. The potassium (K) content in Ramlet Homayyer area ranges from 1.2% to 16.0%. The equivalent thorium (eTh) content in the study area has a maximum value reaching about 68.9 ppm. The equivalent uranium (eU) content attains its maximum value reaching about 84.0 ppm. Factor analysis technique, which provides a way of thinking about radiospectrometric elements and ratio interrelationships alltogether was carried out. The application of factor analysis technique, helped to delineate the zones of high concentrations of eU, eTh and K separately, where the first factor (F1) can delineate high eU zones, (F2) high eTh zones and (F3) high K zones. The radiometric lithologic mapping was conducted for the whole area, by testing the homogeneity of all measurements recorded indicates that the distribution of the radioactivity all over the area is not homogeneous. This indicates that the lithological cover of the study area cannot be considered as one lithologic unit, but contains different types of rock units. Each Interpreted radiometric lithologic units (IRLU) is corresponding to one geomorphological mass or features. As a result of the ground radiometric survey of the study area, chemical analyses for some selected samples were taken and conducted from the anomalous zones at G. Homayyer, G. Ghorabi and Khameila areas. These analyses showed presence of concentrations of uranium up to 147 ppm, 58 ppm, 52 ppm in addition to trace elements with high concentrations of some elements as: Y, Cr, W, Sr and Ag, which gives 6819,768,314,561 and15 ppm respectively.
1. Inroduction The Sinai Peninsula of Egypt covers an area of about 61,000 km2. It has a triangular shape and is bounded the Suez Canal and Gulf of Suez from the west, Gulf of Aqaba from the east, Mediterranean Sea from the north and Red Sea from the south. Ramlet Homayyer area is located in the southwestern part of Sinai Peninsula, to the east of Abu-Zeneima town on the eastern coast of Gulf of Suez, Egypt (Fig. 1). The study area is mainly covered by sedimentary rocks of Phanerozoic Eon. The Paleozoic rocks in Southwestern Sinai attracted the attention of many
∗
authors, since the Pharaohs time by exploiting copper, discovery of manganese-iron ore, and finding of radioactive anomalies, till the identification of secondary uranium mineralization. An airborne geophysical survey for Southwestern Sinai were carried out by Nuclear Materials Authority (NMA) of Egypt in 1966 and 1998 respectively. They involved total count radiometric and gamma-ray spectrometric surveys, which led to the discovery of some important occurrences of radioactive mineralizations. The processing of these data identified many zones, which needed further verification and ground geophysical follow-up (Fig. 2). Accordingly, Ramlet Homayyer area was
Corresponding author. E-mail address: [email protected] (M.A.M. Zaeimah).
https://doi.org/10.1016/j.apradiso.2019.05.036 Received 12 March 2019; Received in revised form 13 May 2019; Accepted 26 May 2019 Available online 01 June 2019 0969-8043/ © 2019 Published by Elsevier Ltd.
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Fig. 1. Location map of the Ramlet Homayyer area, and the Geomorhological features of the region according to Earth Google East Abu-Zeneima city, Southwestern Sinai, Egypt.
This may be done in a systematic manner on a grid pattern for both prospecting and mapping purposes (IAEA, 1979).
selected as a promising target for uranium potentiality. Hence, ground geophysical follow-up survey was applied to this area. This survey includes ground gamma-ray spectrometry and others.
3. Instrumentation
1.1. Regional geology
Spectral gamma-ray measurements were conducted using a portable gamma-ray spectrometer, model GS-512, manufactured by Geofyzika Brno, Czeck Republic. The spectrometer was calibrated using the locally-constructed transportable concrete calibration pads of the Nuclear Materials Authority of Egypt.
The exposures of Ramlet Homayyer area and its surroundings range from Precambrian to Quaternary (Fig. 3). The Precambrian comprises granodiorites and granites. The Paleozoic rocks comprise seven formations from top to base Abu-Zarab, Magharet El-Maiah, El-Hashash, Um-Bogma, Adedia, Abu-Hamata and Sarabit El Khadim. The Mesozoic rocks are represented by Triassic and Jurassic basaltic sheets and dykes. Besides, Upper Cretaceous and Eocene rocks are exposed near the study area. The unconformity surfaces were recorded between Um-Bogma formation and other lower and upper formations (Soliman and Abu ElFetouh, 1969, Alshami, 2003). The exposed rock types in Ramlet Homayyer area (Fig. 4) are related to the Paleozoic, except Farsh Elazrag volcanic which are related to Triassic-Early Jurassic. The main rock types are sandstones, siltstones, shales, conglomerates and basalt (Fig. 4). In this area, the basement rocks are mainly covered by El-Adedia Formation in its northwestern part, at Ramlet Homayyer. In some other localities, Adedia Formation are overlain by black shales equivalent to Um-Bogma Formation, as well as Abu-Thora Formation e.g. at Ramlet Homayyer and Gabal Ghorabi.
4. Field procedure In the present study, ground spectral gamma-ray survey was conducted along 100 profiles, directed N-S, with an average length of 2.5 km, to cover a surface area reaching nearly 10 km2. The distances between the survey profiles ranged from 20 m to 50 m, according to the importance and topography of the area, while the interval between the stations were 20 m perpendicular to the strike of the general geologic trend of the area. The obtained data were reduced and represented as coloured contour maps. 5. Interpretation of the results 5.1. Qualitative interpretation
2. Ground radiospectrometric survey
The surface concentrations of the radioelements: potassium, uranium and thorium, can be qualified by measurements of the intensities of gamma radiation emitted by their respective radioisotopes 40K, 214Bi and 208Tl. Ground gamma-ray spectrometry is commonly used to make such measurements, which can be related to surface concentrations by appropriate calibration procedures. Such data are then used to compile maps showing the surficial distributions of these three radioelements and their binary ratios. The relationship between the average surface radiometric concentrations and the radioelement concentrations in subsurface bedrock depends on the surface area of the outcrop, the relation between overburden and bedrock radioelement concentrations, the percentage of marshland or surface ware in the area, soil moisture and density of vegetation (Charbonneau et al., 1976). Data of the measured gamma-ray spectrometric parameters (T.C., K, eU and eTh) were finally displayed in the form of coloured contour maps (Figs. 5–11).
All common rock types and their related soils contain significant amounts of radioactive elements (radioelements). The presence of these radioelements is apparent in any gamma-ray survey, irrespective of whether or not the purpose of the survey to map their distribution in the natural environment. In practice, at least in the early stages of exploration, it is usually advisable to map the radioactivity data, because small abnormalities may provide the first clue pointing towards an enrichment of radioactive elements, such as uranium and thorium (IAEA, 1979). The main objectives of gamma-ray spectrometric survey are to locate anomalous gamma radiation fields and determine the nature and concentration of the radioisotopes, which give rise to them. The gamma-ray spectrometric survey technique is simply to move the appropriate spectrometer system across (or through) the area of interest. 130
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Fig. 2. Total-Count radiometric map of Abu-Zeneima/Al-Tur area, Southwestern Sinai, Egypt (NMA, 1999).
The qualitative interpretation of the ground γ-ray radiometric survey data is mainly concerned with the visual examination of the colour contour maps of the measured radioelement concentrations as well as the total-count radioactivity. This examination aims to classify
the study area into zones, based on the contrasts in their spectral γ-ray emission response levels. Visual examination of the gamma-ray spectrometric filled-colour contour maps indicates three outlined radio-spectrometric zones: low, 131
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Fig. 3. Regional geological map of Ramlet Homayyer area, Southwestern Sinai, Egypt.
intermediate and high.
(lowest T.C.) to light violet (highest T.C.) to help data interpretation. These three relative zones of radioactivity could be described in the following. The low radioactivity level is encountered at the northwestern part of the study area, and coincides with Wadi Khameila, which has a northwest trend. This level is discrimenated by false blue colour (Fig. 5), and varies in T.C. radiometric intensity from 1.0 to 10.0 Ur. The intermediate radioactivity level is recorded over Adadia Fm. It has false green, yellow and orange colours (Fig. 5), and ranges in T.C. radioactivity from 10 Ur to 20 Ur. The high radioactivity level extends over some parts of Adadia, Um-Bugma., Magharet Elmiah. and AbuZarab formations. It is represented by an elongated and rouned anomalous zones located in the southern, centeral and northeastern parts of the study area. These anomalous zones, as a whole, are elongated in the NW, NE and N-S directions. It has false red and violet colours (Fig. 5), and ranges in radioactivity from 20 Ur to mor than 58 Ur. There are some very high spots representing real anomalies, that are shown on (Fig. 5) and reached 140.2, 177.5, 183.4, 198.5, 374.8 Ur.
5.2. Total-count (T.C.) radiometric data The examination of the false-colour total-count (T.C.) radiometric contour map (Fig. 5) shows that the radioactivity values vary widely from 1.0 Ur to 58.6 Ur. Some of the delineated high radiometric anomalies are circular in shape and others are elongated in various directions. They are roughly parallel to the Gulf of Suez (NNW), Gulf of Aqaba (N-S) and Red Sea (NW) trends. The very high levels of radioactivity are nearly associated with Um-Bogma Fm. The high levels are associated with Adadia and Um-Bugma formations. The lowest T.C. radiometric levels are connected with Wadi Ghamela. The intermediate T.C. radioactivity level is common through the remaining surface of the study area. The Total-Count (T.C.) radiometric filled colour contour map (Fig. 5) was classified into three main relative zones, ranging from blue
Fig. 4. Detailed geological map of Ramlet Homayyer area, Southwestern Sinai, Egypt. 132
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Fig. 5. Ground filled-colour total-count contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
5.3. Potassium (K) radiospectrometric data
5.4. Equivalent thorium (eTh) data
The potassium (K) content in ramlet Homayyer area ranges from 1.0% to 16.0%. The false-colour potassium (K) contour map (Fig. 6) was divided into three main relative zones that change in false colour from blue (low intensity), green, yellow and orange (intermediate intensity) to red and violet (high intensity). The low K level has a false blue colour and is encountered as scattered spots allover Ramlet Homayyer area. It ranges in K intensity from 1.0% to 2%. The intermediate K level has vast areal extent on the entire Ramlet Homayyer area, and is elongated in NW and NE directions. This level was false coloured in green, yellow and orange. It varies in K intensity from 2% to 4%. The high K level is mainly associated with Adadia Formation. The contours of this level are mainly elongated, and extend in both the NW and NE directions. This level was false coloured in red and violet and varies in K intensity from 4% to more than 7.0%.
The equivalent thorium (eTh) content in the study area has a maximum value reaching about 57.3 ppm. Some of the delineated high eTh anomalies are circular in shape and others are elongated in the NW and NNW directions (Fig. 7). The minimum eTh values reach 1.0 ppm and are corelated with Wadi Ghamela. The false-coloured eTh contour map could be classified into three remarkable and relative zones ranging in intensity from less than 10.0 ppm to more than 40.0 ppm, and in false colour from blue (low intensity) to violet (high intensity). The low eTh zone is encountered at the southwestern part of the study area, coinciding with Wadi Ghamela, and the northwestern parts of the study area. This level is distinguished by false blue colour (Fig. 7), and varies in eTh intensity from 9.2 ppm to 15 ppm. The intermediate eTh zone is observed at scatered parts along the study area. This zone is false-coloured by green, dark and light yellow (Fig. 7) and varies in eTh
Fig. 6. Ground filled-colour potassium (K) contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) 133
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Fig. 7. Ground filled-colour equivalent thorium (eTh) contour map of Ramlet Homayyer area Southwestern Sinai, Egypt. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
intensity from 15 ppm to 20 ppm. The high eTh zone extends over some parts of Adadia Fm., Um-Bugma Fm. and Magharet Elmiah Fm. It is represented by elongated and rounded anomalous zones, located in the southern, centeral and northeastern parts of the study area. These zones have NW, NE and N-S directions. They are false-coloured by red and violet (Fig. 7), and range in intensity from 20 ppm to mor than 68.9 ppm.
three remarkable and relative levels ranging in intensity from 1.0 ppm eU to more than 80 ppm eU and in false-colour from blue (low intensity) to violet (high intensity). This division helped much in the interpretation of the eU radiospectrometric survey data. The low eU zone is encountered as an elongated shape, coincides with Wadi Ghamela and the northwestern part of the area under study. This level is false-coloured by blue (Fig. 8), and varies in eU intensity from 1.0 ppm to 5.0 ppm. The intermediate eU zone appears along great parts, mainly at the eastern side of the area under investigation. This zone is false-coloured by green, dark and light yellow (Fig. 8) and varies in eU intensity from 5.0 ppm to 15.0 ppm. The high eU zone extends over a small portion of Ramlet Homayyer area. It is represented by an elongated zone located in the northeastern part of the study area, beside another smaller one to its south. These two zones concide with Um-Bugma, Magharet Elmiah
5.5. Equivalent uranium (eU) data The equivalent uranium (eU) content attains its maximum value reaching about 51.0 ppm at the central southern part of the study area (Fig. 8). The minimum eU value, reaching 1.0 ppm is situated at Wadi Ghamela. The average value of eU in the study area attains about 3.4 ppm. The eU false-coloured contour map can be distinguished into
Fig. 8. Ground filled-colour equivalent uranium (eU) contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) 134
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Fig. 9. Ground filled-colour eU/eTh ratio contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. . (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
Fig. 10. Ground filled-colour eTh/K ratio contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. . (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
and Abuzarab Fms. They are false-coloured by red to violet (Fig. 8) and vary in their eU intensity from 15.0 ppm to more than 85.0 ppm. There are some other point anomalies shown on (Fig. 8), reaching 129.9167.2, 172.5, 184.8, 346.4 ppm.
anomalous zones of this ratio are concentrated at Um-Bugma Fm., where their values range from 1.0 ppm to 5.2 ppm and the highest anomaly of eU/eTh ratio is recorded over Um-Bugma Fm. The lowest anomaly of eU/eTh ratio is recorded over Adadia Fm. at Gabal El-sania. The relatively low eU/eTh ratio zone is encountered at Adadia Fm. This level is false-coloured by blue and green (Fig. 9), and varies in eU/eTh ratio intensity from 0.2 to 0.8. The intermediate eU/eTh zone is encountered at Wadi Ghamela and the northwestern parts of Ramlet Homayyer loose sands. This zone is false-coloured by dark and light yellow (Fig. 9) and varies in eU/eTh ratio intensity from 0.8 to 1.0. The high eU/eTh ratio zone extends over small part of Ramlet Homayyer area. They are represented by elongated zones located in the northeastern part of the area, beside a small one to its south. This zone reflects the outcrop of Um-Bugma, Magharet Elmiah and Abuzarab Fms.
5.6. eU/eTh ratio The eU/eTh ratio is important for uranium exploration, because it determines the uranium-enriched areas. The eU/eTh contour map (Fig. 9) confirms the presence of very high eU/eTh ratio zones, reflecting increased eU superimposed on eTh intensity values. These anomalies may have been produced by solutions, highly enriched in uranium, which have permitted the mobilization and the concentration of uranium. The eU/eTh ratio contour map (Fig. 9) shows that the 135
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They are false-coloured by red to violet (Fig. 9) and vary in intensity from 1.0 to mor than 4.0.
0.3 to 3. The intermediate eU/K ratio zone is false-coloured by dark and light yellow (Fig. 11). The high eU/K zone extends over a small portion of Ramlet Homayyer area. It is represented by an elongated zone, located in the northeastern part of the study area, beside a small one to its south. This zone extends over Um-Bugma, Magharet Elmiah and Abuzarab formations. It is false-coloured by red to violet (Fig. 11) and varies in eU/K ratio intensity from 6.0 to more than 29.0.
5.7. eTh/K ratio The eTh/K ratio in the study area attains its maximum value reaching about 25, which is associated with Magaret Elmiah Fm. Some of the delineated high radiometric anomalies are circular in shape and others are elongated. They are roughly parallel to the Gulf of Suze, Gulf of Aqba and Red Sea trends NW - SE, and N-S direction (Fig. 10). The minimum eTh/K ratio value reaching 1.4 is situated in Wadi Ghamela and Ramlet Homayyer loose sands. The eTh/K ratio contour map (Fig. 10) could be classified into three remarkable and relative zones, ranging in intensity from less than 0.6 to more than 25.0, and in false-colour from blue (low intensity) to violet (high intensity). The low eTh/K ratio elongated zone is encountered at the southwestern part of the study area, and coincides with Wadi Khameila and its north western part and, Ramlet Homayyer loose sands. This level is false-coloured by blue and green (Fig. 10), and varies in eTh/K ratio intensities from 1.4 to 3.0. The intermediate eTh/K zone is false-coloured by dark and light yellow (Fig. 10) and varies in eTh/K ratio intensities from 3.0 to 4.0. The high eTh/K ratio zone extends over some parts of Adadia, Um-Bugma, and Magaret Elmiah formations. They are represented by elongated and rounded anomaly zones, located in the southern and central parts of the study area. These anomalies as a whole are arranged in NW, NE and N-S directional trends. They are false-coloured by red to violet (Fig. 10) and vary in eTh/K intensities from 3.0 to more than 25.0.
5.9. Quantitative interpretation The results of the gamma-ray spectrometric survey data acquired over the investigated area were quantified through the application of some appropriate statistical analysis techniques. These techniques include conventional standard statistics as well as factor analysis. Detailed gamma-ray spectrometric data (T.C., K, eU and eTh) were plotted for the detailed-survey area. The three ratios eU/eTh, eU/K and eTh/K were calculated on the basis that null values are inserted in places where K is less than 0.01%. A composite data file was prepared to include the 7 variables (T.C., K, eU, eTh, eU/eTh, eU/K and eTh/K). The number of valid calculated data points per variable was 11229 points. Conventional standard statistics were applied to the data to compute their arithmetic means ( X ) and standard deviations (S) for each variable (Table 1) for the whole study area. The correlation coefficient (r) matrix (Table 2) shows positive (direct) correlations between T.C. and five variables (K, eU, eTh, eU/K, and eTh/K), which attain values of 0.10, 0.82, 0.76, 0.72 and 0.68 respectively. Meanwhile, there is no correlation between T.C. and eU/ eTh, where the critical correlation coefficient (rc) attains 0.06 at the 95% level of confidence. The correlation between K and the other five variables (eU, eTh, eU/ eTh, eU/K and eTh/K) are all negative (indirect) except eTh (direct) with values of −0.13, 0.08, −0.22, −0.34 and −0.30 respectively (Table 2). The correlation between eU and the other four variables are all positive (direct) and significant with values of 0.52, 0.42, 0.96 and 0.56 respectively (Table 2). Meanwhile, the correlation between eTh and the other two ratios (eU/K and eTh/K) are positive (direct) with values of 0.46 and 0.90 respectively, but it is negative (indirect) with eU/eTh and reaches −0.39 in value (Table .2). The eU/eTh ratio shows direct correlation with the eU/K ratio (0.44) and indirect correlation with the eTh/K (−0.27). Finally, the correlation between eU/K and
5.8. eU/K ratio The eU/K ratio attains its maximum value reaching about 29.0 at the central southern part of the study area (Fig. 11). The minimum eU/ K value, reaching 0.7 is situated at Wadi Ghamela.The eU/K ratio contour map can be separated into three remarkable and relative zones ranging in intensity from 0.3 to more than 29.0 and in false-colour from blue (low intensity) to violet (high intensity). The low eU/K ratio zone is encountered as an elongated shape that coincides with Wadi Ghamela and the northwestern parts of the area under study. This level is coloured by blue and green (Fig. 11), and varies in eU/K intensity from
Fig. 11. Ground filled-colour eU/K ratio contour map of Ramlet Homayyer area, Southwestern Sinai, Egypt. . (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.) 136
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Table 1 Descriptive statistics of the ground gamma-ray spectrometric survey data of Ramlet Homayyer area, East Abu-Zeneima, Southwestern Sinai, Egypt. Variable
N
Min. value
Max. value
Range
Mean ( X¯ )
Std. Dev. (S)
T.C. (Ur) K (%) eU (ppm) eTh (ppm) eU/eTh eTh/K eU/K
11229 11229 11229 11229 11229 11229 11229
1.0 1.0 1.0 1.0 0.1 0.6 0.3
58.6 16.1 51.9 57.3 5.2 30.2 34.6
57.6 15.1 50.9 56.3 5.1 29.6 34.3
7.534 1.983 3.447 6.636 0.587 3.623 1.932
3.842 0.754 2.233 3.907 0.292 2.443 1.515
Table 3 Unrotated factor matrix of the seven variables of ground gamma-ray spectrometric survey data, Ramlet Homayyer area, East Abu-Zeneima, Southwestern Sinai, Egypt. Variables
Eigen value % of total variance Cumulative % T.C. (Ur) K (%) eU (ppm) eTh (ppm) eU/eTh eU/K eTh/K
eTh/K is direct reaching 0.61, where the critical correlation coefficient (rc) attains 0.06 at the 95% level of confidence. Factor analysis is a multivariate statistical technique, whereby the number of variables is reduced to the minimum number of independent variables, which will describe the data. Various methods of factor analysis were derived, by which the relationships, between variables and the relationships between samples could be determined (Duval, 1976). Instead of discussing the correlations between these seven variables in detail, factor analysis technique which provides a way of thinking about these interrelationships alltogether was carried out. The matrix shown on (Table 2) was used to get the “Unrotated matrix” indicated on Table (3), coupled with extracting Eigen values and their cumulative percent. Factor loadings of the variables are effective on the first three at the 95% level of confidence unrotated factors F1, F2 and F3, while they are not effective on the four remaining factors (F4 to F7) (Table 3). The highest factor is F1 in sense that the weight of the factor loading reaches 54.70, while the squint factors (F2 and F3) become progressively smaller attaining 25.41 and 15.20 respectively (Table 3). These unrotated factors are rarely useful in scientific work, so it is possible to “rotate” this unrotated factor matrix into another form that is mathematically equivalent to the original unrotated matrix using varimax method (Comery, 1967). The 7-dimensional factor space can be reduced without significant loss of information into three dimensions of space (principal factors). These three principal factors are quite interpretable and represent 95% of the total system of information, which is sufficient to interpret the available data. Table (4) shows the three principal factors F1, F2, and F3 as extracted from (Table 3). They are rotated using varimax method. It can be concluded, from Table 4 that the first factor (F1) shows appreciably high positive loadings with four variables T.C., eU, eU/K and eU/eTh reaching 80%, 97%, 93% and 57%, respectively and low positive loadings with eTh and eTh/K with values of 42% and 46%, respectively. F1 exhibits an inverse low loading with K as a negative value of (−8%). The F1 factor for these reasons is very identical with the total-count radiometric and uranium maps. Therefore, this can be mainly used for uranium exploration. Consequently, F1 can be identified as the factor of integrated radioactivity or uranium exploration factor (Moustafa et al., 1990) (see Table 5). The second factor (F2) is high and positively (directly) loaded with
Factor F1
F2
F3
F4
F5
F6
F7
3.83 54.70 54.70 0.90 −0.19 0.90 0.80 0.12 0.89 0.85
1.78 25.41 80.11 −0.11 −0.43 0.33 −0.57 0.93 0.41 −0.35
1.06 15.20 95.31 0.29 0.87 0.21 −0.02 0.23 −0.01 −0.35
0.16 2.24 97.55
0.14 1.93 99.48
0.03 0.41 99.89
0.01 0.11 100.00
Table 4 Loadings of factors (varimax rotated) of the ground gamma-ray spectrometric survey data, Ramlet Homayyer area, East Abu-Zeneima, Southern Sinai, Egypt. Variable
T.C. (Ur) K (%) eU (ppm) eTh (ppm) eU/eTh eU/K eTh/K
Rotated Factor F1
F2
F3
0.80 −0.08 0.97 0.42 0.57 0.93 0.46
0.48 0.02 0.14 0.88 −0.75 0.13 0.82
0.19 0.99 −0.05 0.09 −0.17 −0.29 −0.30
eTh and eTh/K reaching 88% and 82%, respectively. Meanwhile, it is positive and weakly loaded with T.C., eU and eU/K reaching 48%, 14% and 13%, respectively (Table 4). In the same time, it is very weakly loaded with K attaining only 2%. Meanwhile, it is highly and inversely (indirect) loading with eU/eTh ratio attaining −75%, (Table 4). The third factor (F3) shows high and positive (direct) loading with K only, attaining 99%. It displays positive and low loadings with T.C. and eTh reaching 19%, and 9%, respectively. Meanwhile, it is inversely (indirectly) and weakly loaded with four variables (eU, eU/K, eTh/K and eU/eTh) reaching −5%, −29%, −30% and −17%, respectively. These standard factor scores can characterize different radiolithologic units in the study area. The results obtained from the application of factor analysis technique show that, it is possible to delineate the zones of high concentrations of eU, eTh and K separately, where F1 can delineate high eU values, F2 high eTh values and F3 high K values. 5.10. Interpreted radiometric lithologic units (IRLU) The radiometric lithologic mapping was conducted for the whole area, by testing the homogeneity of measurements recorded over the
Table 2 Matrix of correlation coefficients, conducted between the seven radiospectrometric data variables, Ramlet Homayyer area, East Abu-Zeneima, Southwestern Sinai, Egypt. Variables
T.C. (Ur)
K (%)
eU (ppm)
eTh (ppm)
eU/eTh
eU/K
eTh/K
T.C. (Ur) K (%) eU (ppm) eTh (ppm) eU/eTh eU/K eTh/K
1.00 0.10 0.82 0.76 0.06 0.72 0.68
1.00 −0.13 0.08 −0.22 −0.34 −0.30
1.00 0.52 0.42 0.96 0.56
1.00 −0.39 0.46 0.90
1.00 0.44 −0.27
1.00 0.61
1.00
Critical correlation coefficient (rc) = 0.06 95% level of confidence. 137
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Wadi deposits by 3 IRLU units (4, 5 and 6), Abu- Zarab Formation by one IRLU units (No.11), upper sandstone Magaret Elmiah Formation by IRLU (12, 12–1, 12–2, 12–3 and 12–4), middle carbonate Um- Bogma Formation by 3 IRLU units (1, 2, and 3), lower sandstone Adedia Formation by four IRLU (7, 8, 9 and 10). As a result of the ground spectrometric survey of the study area, chemical analyses were carried out for some selected samples that were collected from the anomalous zones at G. Homayyer, G. Ghorabi and Khameila areas. These analyses showed presence of concentrations of uranium up to 147 ppm, 58 ppm, 52 ppm in addition to the existence of trace elements with high concentrations in some elements as: Y, W, Sr and Ag, which yielded 6819,314,561 and15 ppm respectively (Alshami, 2018 b, in press).
Table 5 Chemical composition of representative samples at Gabal Homayyer, Ghorabi, Khameila localities of the study area. Oxides
Km
Gh-1
Gh-2
SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O P2O5 H2O S Cl V Co Ni Cu Zn Pb Ag As Sb W Sr Ba Y Zr Nb Th U
79.25 1.10 7.20 6.45 0.06 0.49 2.61 0.06 0.01 0.95 0.50 0.1593 171 151 120 255 30 0 57 15 71 4 314 561 342 6819 618 216 10 147
84.37 0.27 8.27 4.69 0.01 0.45 0.67 0.10 0.03 0.31 0.45 0.0559 487 60 27 58 21 0 73 10 30 7 85 281 32 1402 180 44 4 58
84.69 0.27 8.13 4.65 0.01 0.45 0.68 0.08 0.01 0.31 0.31 0.0465 464 48 40 60 21 0 78 4 28 10 53 282 27 1407 187 45 4 52
6. Summary and conclusions In the present study of Ramlet Homayyer area, ground spectral gamma-ray survey was conducted along N-S parallel, equally-spaced profiles, with lengths of about 2.5 km, and a total surface area equal about 10 km2. The measurements were conducted using a portable gamma-ray spectrometer, model GS-512. The examination of the total-count (T.C.) radiometric contour map shows that the radioactivity values vary widely from 3.4 Ur to 101.3 Ur. The potassium content ranges from 1.2% to more than 7.0%. The equivalent thorium content has a maximum value reaching about 68.9 ppm. The equivalent uranium content attains its maximum value reaching about 84.0 ppm. Factor analysis technique which provides a way of thinking about radiospectrometric elements and ratio interrelationships, all together was carried out. The application of factor analysis technique, helped to delineate zones of high concentrations of eU, eTh and K separately, where the first factor (F1) can delineate high eU zones, (F2) high eTh zones and (F3) high K zones. The radiospectrometric lithologic mapping was conducted for the whole area, by testing the homogeneity of measurements recorded over the study area as a whole. This indicates that the distribution of the radioactivity all over the area is not homogeneous. This indicates that the lithological cover of the study area cannot be considered as one lithologic unit, but contains different types of rock units. Each IRLU is corresponding to one geomorphological mass or feature. As a result of the ground spectrometric survey of the study area chemical analyses were conducted for some selected samples that were collected from the anomalous zones at G. Homayyer, G. Ghorabi and Khameila areas. These analyses showed the presence of concentrations of uranium up to 147 ppm, 58 ppm, 52 ppm in addition to presence of
study area as a whole which indicates that the distribution of the radioactivity all over the area is not homogeneous. This indicates that the lithological cover of the study area cannot be considered as one lithologic unit, but contains different types of rock units. Each IRLU is corresponding to one geomorphological mass or features. Fig. 12 indicates that the study area is covered by interpreted radio-lithologic (IRLU) units, in addition to the values which were deviated from normal distributions (coloured points). Fig. 13 shows the correlation diagram of the computed (T.C.) statistical parameters of (IRLU). The detailed geological map (Fig. 4) of the study area contains five lithological units: Wadi deposits, Abu-Zarab Formation, upper sandstone Magaret Elmiah Formation, middle carbonate Um- Bogma Formation, and lower sandstone Adedia Formation, arranged from top to bottom. Each of these rock types are represented by one or more IRLU units.
Fig. 12. Interpreted radiometric lithologic unit (IRLU) map of, Ramlet Homayyer area, Southwestern Sinai, Egypt. 138
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S.A. Alkhateeb, et al.
Fig. 13. The correlation diagram of the computed (T.C.) statistical parameters of (IRLU), Ramlet Homayyer area, Southwestern Sinai, Egypt.
trace elements with high concentrations of some elements such as: Y, Cr, W, Sr and Ag, which yielded 6819,768,314,561 and15 ppm respectively. On the other hand, the study area needs more detailed geophysical studies (electric tools) to follow the shape of anomalous lenses and horizons at the subsurface.
Gamma-Ray Spectrometer Measurements over the Canadian Shield. IAEA Symposium on Exploration for Uranium Ore Deposits, Vienna, Austria, 1976. STI/PUB/434, pp. 35–53 IAEA-SM-208/3. Comery, A.L., 1967. A First Course in Factor Analysis. Academic Press, New York, pp. 316p. Duval, J.S., 1976. Statistical interpretation of airborne gamma ray spectrometric data using factor analysis. In: Proceedings of a Symposium on Exploration of Uranium Ore Deposits, Vienna, IAEA. SM. 208/12. GS-512, Manufactured by Geofyzika Brno, Czeck Republic. International Atomic Energy Agency "IAEA", 1979. Gamma-ray Surveys in Uranium Exploration. IAEA Technical Report Series No. 186. pp. 90 Vienna, Austria. Moustafa, M.E., Rabie, S.I., Elrakaiby, M.L., 1990. Rock Unit Mapping Using Factorial Analysis Applied to Airborne Gamma-Ray Spectrometric Data, West G. Gattar Area, Eastern Desert of Egypt. Annals of the Egypt, Geol. Survey and Mining Authority (EGSMA). (Cairo, Egypt). NMA Internal Scientific Report, 1999. Study of Abu Zinima rea, South Sinai, Egypt. Soliman, M.S., Abu El-Fetouh, M.A., 1969. Petrology of carboniferous sandstone in west central Sinai. J. Geol. UAR 13, 61 43.
References Alshami, A.S., 2003. Structural and Lithologic Controls of Uranium and Copper Mineralization in Um Bogma Environs, South Western Sinai, Egypt. Ph.D. Thesis. Faculty of Science, Mansoura University, Egypt, pp. 148p. Alshami, A.S., 2018 b b. INFRA-CAMBRIAN PLACER GOLD-URANIFEROUS PALEOZOIC SEDIMENTS, SOUTHWESTERN SINAI. EGYPTScientific Society of Nuclear Materials Authority (in press). Charbonneau, B.W., Killeen, P.G., Carson, J.M., Cameron, G.W., Richardson, K.A., 1976. In: The Significance of Radioelements Concentration Measurements Made by
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