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Order differences to enhance the delineation of rock units boundaries by using aerospectrometric data of Wadi Al Mushash area, Central Eastern Desert, Egypt: A new approach
Applied Radiation and Isotopes 155 (2020) 108938
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: http://www.elsevier.com/locate/apradiso
Order differences to enhance the delineation of rock units boundaries by using aerospectrometric data of Wadi Al Mushash area, Central Eastern Desert, Egypt: A new approach Mohamed A.S. Youssef Nuclear Materials Authority, Exploration Division, Po. Box 530, Maadi, Cairo, Egypt
A R T I C L E I N F O
A B S T R A C T
Keywords: Aerospectrometric data Composite image Differences technique
The present work utilizes airborne gamma-ray spectrometric data, in a trial to refine the surface geological mapping of sedimentary rocks at Wadi Al Mushash, Central Eastern Desert of Egypt. The acquired aerospec trometric data were supported by the surface geology concerning the study area. This area is mainly covered by sedimentary rocks of Tertiary to upper Cretaceous as Nubian Sandstone Formations (Quseir Clastics and Tarif Sandstone), Duwi Phosphates Formation, Dakhla Shale Formation, Esna Shale Formation, Tarawan Formation, Thebes Formation, and Quaternary deposits. High-resolution airborne gamma-ray spectrometry can be very helpful in mapping the surface geology. The method provides estimation of the apparent surface concentrations of the most common naturally occurring radioactive elements, such as potassium (K), equivalent uranium (eU) and equivalent thorium (eTh). This work is based on the assumption that, the absolute and relative concentra tions of these radioelements vary measurably and significantly with lithology. The composite image technique is used to display and simulate three parameters of the radioelements concentrations. The technique offered much in terms of lithologic discrimination, based on color differences and showed efficiency in defining areas, where different lithofacies occur within areas mapped as one continuous lithology. The Differences technique is used to delineate contacts of the rock units and the mainly structures of the study area. It is based mainly on varying in change of concentration of successive total count measurements within each line in the study area. Then, a suitable difference order is selected and matched to original measured line. Moreover, plotting the suitable order as grid and applied grid peaks on this grid. Then, these ridge grid peaks are symbolized over surface geological information and prepared radioelement composite map. This provides more detail about the surface geology, and addition more contacts occurred within original rock units. These subdivisions of rock units may be related to one formation that consists of more than one member having a different composition.
1. Introduction The study area is located on the eastern part of the Nile Valley, Central Eastern Desert that bounded by latitudes 25� 350 and 25� 470 N and longitudes 33� 000 and 33� 230 E (Fig. 1). Airborne gamma-ray spectrometric data can be used for surface geological mapping (Gra ham and Bonham-carter, 1993; Andrson and Nash, 1997; Jaques et al., 1997; Charbonneau et al., 1997; Youssef and Elkhodary, 2013). Gamma-ray spectrometric data have been applied, with variable degrees of success, for mapping lithological units and enhancing radioelement patterns within the individual units (IAEA, 2003). Darnley and Ford (1989) showed that, in many situations, gamma-ray spectrometry is probably more useful than any other single airborne geophysical method
in providing information directly interpretable in terms of surface ge ology. Elawadi et al. (2004) stated “the interpretation of radioelements distribution for mapping the surface geology is based on the assumption that, different rock types are composed of certain amounts of rock-forming minerals, which comprise specific quantities of radioactive elements.” The relationship between the radioelement content of the surficial material and the composition of the bedrock must be inferred by considering complementary evidence, provided by geological maps, satellite imagery, or ground inspection (see Fig. 2). The present study aims to recognize and identify the contact zones between various rocks and to remap the surface geology in the area. Moreover, it sheds light on the radio-spectrometric anomalies that may be related to these geologic contacts or associated geologic units.
E-mail address: [email protected]. https://doi.org/10.1016/j.apradiso.2019.108938 Received 29 July 2018; Received in revised form 10 October 2019; Accepted 11 October 2019 Available online 13 October 2019 0969-8043/© 2019 Elsevier Ltd. All rights reserved.
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Applied Radiation and Isotopes 155 (2020) 108938
the study area (Fig. 2) has been published by the Geological Survey of Egypt (1992). The Quseir Formation is composed of fine-grained variegated shale with minor bioclastic limestone and phosphate beds of shallow marine origin. It occupies the northeastern part of the area. The Tarif Formation is composed of fine-to medium-grained sandstone with interbedded channel and soil deposits. The Upper Cretaceous Duwi Phosphate For mation is composed of a sequence of alternating beds of claystone, sandstone, calcareous mudstone, siltstone, siliceous mudstone. It has gained special importance because of its high contents of uranium mineralization related to the phosphates of this Formation. The Dakhla Formation is composed of dark gray shallow marine marl and shale with limestone intercalations. The Tertiary sedimentary rocks are repre sented in the study area by Esna Formation, Tarawan Formation, Thebes Formation, and conglomerates. The Esna Formation is a sequence of greenish gray open marine shale that is calcareous. The Tarawan For mation is composed of white chalk limestone containing beds of marl. The Thebes Formation consists of thinly bedded outer shelf chalk and chalky limestone rich in chert band. The conglomerates form a thick sequence of well-rounded pebbles and boulders. They are highly weathered, fractured and faulted and widely distributed in the western part of the studied area. The Quaternary deposits and recent sediments fill the main wadies in the surveyed area. They are composed of allu vium and the Nile terrace series (Sadek, 1972). The wadi deposits filling the wadies include sands, pebbles, and boulders as a result of the weathering and denudation processes for the surrounding hills.
Fig. 1. Map of Egypt showing the location of the study area.
Consequently, the surface geological setting of these different rock units could be remapped by integrating spectrometry maps of the three ra dioelements and composite images as well as the geologic map of the study area. The topography of the area is not highly rugged and is formed of a moderate hilly country that rises gradually in altitude eastwards. The geomorphology is closely connected with the geological structures and lithology of the study area. The trends of most wadis are generally controlled by structural elements and rock contacts.
3. Airborne gamma-ray spectrometric survey The study area was considered for the systematic airborne geophysical survey conducted by Aero-Service Division, Western Geophysical Company of America, in 1984. It was conducted along parallel flight lines oriented in the NE-SW direction at approximately 1.5-km line spacing and 120 m ground clearance. A high-sensitivity 256 channel airborne gamma-ray spectrometer was used to carry out the γ-ray spectrometric survey (Aero-Service, 1984a,b). The obtained
2. Geologic setting The study area is generally covered by Nubian Sandstone Formations (Quseir Clastics and Tarif Sandstone), Duwi Phosphate Formation, Dakhla Shale Formation, Esna Shale Formation, Tarawan Formation and Thebes Formation as well as Quaternary deposits. The geologic map of
Fig. 2. Geologic map of the study area (after the Egyptian geological survey, 1992). 2
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Applied Radiation and Isotopes 155 (2020) 108938
Fig. 3. Total count fill colored contour map (in Ur).
Fig. 4. Potassium fill colored contour map (in %).
airborne gamma-ray spectrometric data were compiled and presented in the form of contoured maps of scale 1:50,000. The data were corrected for background radiation resulting from cosmic rays and aircraft contamination, variations caused by changes in aircraft altitude relative to ground, and Compton scattered gamma-rays in potassium and uranium energy windows. The corrected data provide an estimate of the apparent surface concentrations of potassium, ura nium and thorium (K, eU, and eTh), respectively as well as Total count (TC).
2 The difference technique is applied and a suitable order is selected to separate the edges of different rock units and major structures (may be lineaments) of the present study. 3 Statistical analysis is performed for parameters, such as minimum (Min.) and maximum (Maxi.), calculated arithmetic mean (X), and standard deviation (S), as well as checking the normality of distri bution of their measurements by using the coefficient of variability (CV%) were applied for new separated subrock units by symbolized grid peaks of the second-order difference.
4. Data analysis and interpretation 4.1. Qualitative interpretation of the airborne γ-ray spectrometric maps
1 Contour maps of radioelements (K, eU, and eTh), TC contour maps, and radioelement composite image map of (K, eU and eTh) are plotted and prepared using Oasis Montaj Program V.8.3 (2015).
Gamma-ray spectrometric maps (Figs. 3–7) emphasize the nature of the radioelement distributions and are thus better suited to the recog nition of geological features. These maps show a general relation to the rock units and the structural trends prevailing in the study area. 3
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Applied Radiation and Isotopes 155 (2020) 108938
Fig. 5. Equivalent uranium fill colored contour map (in ppm).
Fig. 6. Equivalent thorium fill colored contour map (in ppm).
Radioelement (K, eU and eTh) contour maps were prepared and care fully inspected and composite radioelements image map were inter preted qualitatively. Examination of the aerospectrometric maps reveals the existence of a wide range of variation in the aeroradioactivity levels, which reflects the fact that the area under study is covered by rocks of various compositions. It is evident from the correlation between the different rock units and the recorded levels of gamma radiation over them that, the pattern of aeroradioactivity is closely connected with the surface geology of the area.
relative potassium concentration in the area. It indicates that the eastern parts of wadi sediments, Tarif Formation, Duwi Formation and Quseir Formation have the highest level of potassium contents (more than 0.65%), while the intermediate level of potassium contents, which ranges from 0.4% to 0.65%, is present in some western parts of wadi deposits and some parts of the Duwi Formation. The lowest level (down to 0.4%) is associated to Esna Formation, Dakhla Formation, Thebes Formation and conglomerates in which their boundaries can be detected. The eU map (Fig. 5) classified into three levels: the first level has range of 4.5 to 34 ppm and associated with wadi deposits and the Duwi Formation. The equivalent uranium (eU) content reaches 34 ppm as the maximum value over the Duwi Formation, and diminishes to 0.4 ppm as the minimum value over conglomerates with a mean of 4.5 ppm. The intermediate radioactive levels range from 2 to 4.5 ppm and associated mainly with the Tarif Formation, some parts of wadi deposits, Tarawan Formation and Esna Formation. The low radiometric levels, with values less than 2 ppm, extend over Dakhla Formation, Thebes Formation, and
4.1.1. Radioelement contour maps The TC map (Fig. 3) was classified into three levels: The TC content reaches 33.6 Ur as the maximum value over the Duwi Formation. The intermediate radioactive levels range from 4.5 to 8.5 Ur and associated mainly with the Tarif, Esna and Quseir Formations. The low radiometric levels, with values less than 4.5 Ur, extend over Dakhla, Tarawan and Thebes Formations as well as conglomerates. The K map (Fig. 4) shows the overall spatial distribution of the 4
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Applied Radiation and Isotopes 155 (2020) 108938
Fig. 7. Composite image of radioelements.
conglomerates. In addition, the eTh map (Fig. 6) is divided into three levels: the first one ranges from 4.5 to 13.8 ppm and associated with the Tarif Forma tion, Duwi Formation, Wadi deposits and Quseir Formation. The second level ranges from 3 to 4.5 ppm and restricted to the western part of the Duwi Formation and some parts of conglomerates. The lowest eTh level is less than 3 ppm which is mostly associated with the Conglomerates, Dakhla Formation, Tarawan Formation, and Esna Formation.
represent the K (in %), eU (in ppm) and eTh (in ppm) concentrations. Here, the blue color represents eU, green for eTh, and red for K. At any location, the relative concentrations of the three radioelements are represented by the color hue produced by mixing appropriate amounts of the three ink colors (Broome, 1990; IAEA, 2003; Youssef and Elkho dary, 2013; Nigm et al., 2018). Regions with relatively high concen trations of the three radioelements look white; while those with relatively low concentrations look dark gray. The color index at each corner of the triangular legend (K in red, eU in blue and eTh in green) indicates 100% concentration of the indicated radioelement. Colors at each point inside the triangle represent different ratios of the radioele ments according to their color differences on the absolute composite image of the three radioelements. The Quseir Formation and Tarif Formation are characterized by their strong K and eTh contents that are clearly visible on the ternary radio element map (Fig. 7) by a yellowish color at the eastern part of the study area. The blue areas indicate uranium-rich areas in Duwi Formation. The western part of the studied area shows black areas of weak radioelement contents as indicative to the low radioactive rocks such as Tarawan Formation, Thebes Formation, Esna Formation and conglomerates.
4.1.2. Ternary map A ternary map is a color composite image generated by modulating the red, green and blue phosphors of the display device or yellow, magenta, and cyan dyes of a printer in proportion to the radioelement concentration values of K, eTh, and eU. The ternary map is a useful geological tool and mineral exploration for discriminating zones of consistent lithology and contacts between contrasting lithologies (Duval, 1983). However, composite color image maps are prepared as follows different rock types have different characteristic concentrations of the three main radioelements. Composite image map of the three radioelements (Fig. 7) is produced by using different ink colors to
Fig. 8. Symbols of grid peaks of second-order differences. 5
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Fig. 9. Symbols of grid peaks of second-order differences over the total count map.
Fig. 10. Symbols of grid peaks of the second-order differences order over the composite map of radioelements.
4.2. Difference technique procedures
D4 (V (i)) ¼ V(iþ2) - 4V(iþ1) þ 6V(i) - 4V(i-1) þ V(i-2) for the fourth-order difference
Use the difference filter using Oasis Montaj version Ver.8.3 to calculate differences between values in a channel. First, TC channel of line within the study area is selecting input. Second, the difference channel is calculated and outputted as the first-order difference, secondorder difference, third-order difference, and so on (number of differ ences > or ¼ 1). Even numbers of differences produce properly located results. Odd numbers of differences will locate the result 1/2 element below the actual location. The difference filter is calculated by the subtraction of the successive data values of the channel, difference database tools within Oasis Montaj program, V. 8.3, 2015:
After applying the first, second, third, and fourth orders for each TC lines within the study area, the second order difference filter is selected as the best order compatible with original total count profiles; then the second order was plotted as the grid without applying any trans formation, followed by applying level of peak detection or grid peak (Blakely and Simpson, 1986) method to find peaks in a grid as normal grid values in all the nearest grid cells are lower from the selected dif ference order. Moreover, symbolized grid peaks compared to previous grid maps, show more for different rock units, and their boundaries and major structures. Fig. 8 shows symbols of grid peaks on a free base map and then plots this grid peaks over the total count map (Fig. 9), over composite map of radioelements (Fig. 10), as well as over geologic map (Fig. 12) to show a good matching and emphasizes delineation symbolized grid peaks for
D1(V (i)) ¼ V(iþ1) - V(i) for the first-order difference D2 (V (i)) ¼ V(iþ1) - 2V(i) þ V(i-1) for the second-order difference D3 (V (i)) ¼ V(iþ2) - 3V(iþ1) þ 3V(i) -V(i-1) for the third-order difference 6
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Fig. 11. Symbols of grid peaks of second-order differences over the new interpreted lithologic unit map.
Fig. 12. Symbols of grid peaks of second-order differences over the geologic map.
each subrock units with geologic map for creating a new interpreted lithologic units map and inferred faults. Figs. 11 and 13 illustrate nine inferred faults (F1–F9) trending in the NW-SE direction parallel to the main structure of the study area. In addition, it distinguished one to several subrock unit contacts then checked, and matched with TC (Fig. 9) and radioelement composite map (Fig. 10). Accordingly, the Duwi Formation subdivided into six subrock units (D1-D6), Wadi deposits subdivided into seven subrock units (W1–W7), Dakhla Formation classified into two subunits, conglomerates subdivided into five subrock units (C1–C5), and Quseir Clastics
subdivided into six subrock units (Q1-Q6). Tarif Sandstone as well as Esna and Tarawan Formation cannot be separated into more than one rock unit because their low radioactivity. Conglomerates, Wadi deposits, Quseir Clastics and Duwi Formation are noticed a good agreement for contacts with their symbols of grid and the NW-SE trend structural. 4.3. Quantitative interpretation In this study, the quantitative interpretation depends principally upon the fact that, the absolute and relative concentrations of the 7
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Fig. 13. Interpreted lithological unit map deduced from grid peaks of the second-order difference technique. Table 1 Statistical analysis of the Total count in the different lithologic units of the study area. Rock units
Age
Sub-rock units
NO.
Min.
Max.
X
S
CV (%)
Wadi deposits (W1–W7)
Quaternary
Conglomerates (C1–C5)
Tertiary
Esna and Tarawan Formation Dakhla Formation (K1–K2)
Upper Cretaceous
W1 W2 W3 W4 W5 W6 W7 C1 C2 C3 C4 C5 E&T K1 K2 D1 D2 D3 D4 D5 D6 Q1 Q2 Q3 Q4 Q5 Q6 Q7 T1
72 47 32 247 40 529 21 74 587 213 874 269 117 170 187 60 487 958 874 296 309 141 570 579 228 197 882 143 297
3.2 3.9 3.2 6.4 1.9 6.1 6.7 2.3 2.7 2.5 1.8 3 3 2.9 2.7 3.3 3.1 2.8 1.8 6.5 2.4 6.6 7.1 6 6.5 6.2 6.4 5.1 5.9
11.1 7.3 5.3 12.5 10.1 11.2 7.6 4.3 10.8 4.9 29.4 5.2 4.9 7.3 14.1 4.3 6.3 14 29.4 9.6 33.1 9.3 12.1 12.4 12.2 20.5 19.2 8.6 9.7
4.5 5.4 4.4 9 4.9 8.6 7.1 3.2 4.4 3.6 11.3 4.1 3.8 4.8 5.6 3.9 4.7 5.2 11.3 7.7 14.8 8.2 9.2 8.6 9.6 9.9 9.6 6.7 7.4
1.3 0.7 0.5 1.1 2.2 086 0.26 0.47 1.2 0.57 6.2 0.46 0.45 1.16 3 0.26 0.59 1.1 6.2 0.7 5.8 0.57 0.96 1 1.4 2.8 1.8 0.89 0.67
20 14 12.4 12.4 44 9.9 3.7 14.5 28 15.7 54.5 11 11.7 24 53.5 6.7 12 22 54.5 9.2 39 7.9 10 11.4 15.4 28 18 13 9
Duwi Formation (D1-D6)
Quseir Formation (Q1-Q7)
Tarif Formation (T1)
Explanation: NO. ¼ Number of samples, Min. ¼ Minimum Value, Max. ¼ Maximum Value, (X) ¼ Mean, (S) ¼ Standard Deviation and CV ¼Coefficient of Variability (%).
radioelements (K%, eU and eTh) vary measurably and significantly with new separated boundaries of lithologic units. Statistical computation was applied to the original spectrometric data without applying any transformation, in accordance with the recommendation given by Sarma and Kock (1980). A composite file was prepared to include four columns (TC, K, eU and eTh) and rows of sample points. Standard statistics were applied to the raw data to compute means, minimums, maximums, range, standard
deviations and homogeneity distribution check for each variable (Table 1). The statistical treatment of the airborne gamma-ray spectrometric data depends mainly on the application of the coefficient of variability (CV) technique for a certain variable value in the study area and check on homogeneity distribution. Statistical analysis was applied on all new separated subrock units for the total count of each rock unit according to the new separating boundaries by the difference technique. Table (1) 8
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gamma ray data in joining collecting materials of this paper. Finally, many thanks to Nuclear materials authority (NMA), Editor and re viewers of applied radiation and isotopes journal.
summarizes the statistical results of the total count over the seven rock units in the study area. The careful examinations of quantitative calcu lations were regarding the degree of homogeneity of the distribution of the total count for the different lithologic rock units. The increase in detailing of the rock constituents can be improved of new subunits for one unit by lower CV% values that mean the higher degree of homogeneity. The careful examinations of quantitative calculations were regarding the degree of homogeneity of the distribution of the TC of radioactivity within each separating subrock units. In the present study, the lower CV % values mean the higher degree of homogeneity that reflects a good agreement for separation of subrock units.
Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.apradiso.2019.108938. References Aero-Service, 1984. Interpretation Report of Airborne Gamma-Ray Spectrometer and Magnetometer Survey of the Eastern Desert of Egypt, 127pp. Aero-Service, 1984. Final Operational Report of Airborne Magnetic/radiation Survey in the Eastern Desert, Egypt for the Egyptian General Petroleum Corporation. AeroService, Houston, Texas. April, 1984, Six vol. s. Andrson, H., Nash, C., 1997. Integrated lithostructural mapping of the Rossing area, Namibia using high resolution aeromagnetic, radiometric, Landsat data and aerial photographs. Explor. Geophys. 28, 185–191. Blakely, R.J., Simpson, R.W., 1986. Approximating edges of source bodies from magnetic or gravity anomalies. Geophysics 51 (7), 1494–1498. Broome, H.J., 1990. Generation and interpretation of geophysical images with examples from the rae provinces, northwestern Canada shield. Geophysics 55 (8), 977–997. Charbonneau, B.W., Holman, P.B., Hetu, R.J., 1997. Airborne gamma spectrometer magnetic-VLF survey of northeastern Alberta. In: Exploring for Minerals in Alberta: Geological Survey of Canada Geoscience Contributions, Edited by Mac Queen, Canada-Alberta Agreement on Mineral Development, vol. 500. Geological Survey of Canada, Bulletin, pp. 107–132. Darnley, A.G., Ford, K.L., 1989. Regional airborne gamma-ray surveys. In: Garland, G.D., Ontario (Eds.), A Review in Proceedings of Exploration, 87: Third Decennial International Conference on Geophysical and Geochemical Exploration for Minerals and Groundwater, vol. 3. Geological Survey of Canada, Special, 960 pp. Duval, J.S., 1983. Composite color images of aerial gamma-ray spectrometry data. Geophysics 48, 722–735. Elawadi, I.A., Ammar, A.A., Elsirafy, A., 2004. Mapping surface geology using airborne gamma-ray spectrometric survey data – a case study. In: Proc.The 7th SEGI International Symposium-Imaging Technology, Sendai, Japan, pp. 349–354. Geological Survey of Egypt, 1992. Geological Map of Wadi Barramiyah Quadrangle, Egypt, Scale 1:250000. EGSMA, Cairo. Graham, D.F., Bonham-carter, G.F., 1993. Airborne radiometric data: a tool for reconnaissance geological mapping using a GIS. Photogramm. Eng. Remote Sens. 58, 1243–1249. IAEA, 2003. Guidelines for Radioelement Mapping Using Gamma-Ray Spectrometry Data. IAEA-TECDOC-1363, VIENNA, 179pp. Jaques, A.I., Wellman, P., Whitaker, A., Wyborn, D., 1997. High resolution geophysics in modern geological mapping. AGSO J. Aust. Geol. Geophys. 17, 159–174. Nigm, A.A., et al., 2018. Airborn gamma-ray spectrometric data as guide for probable hydrocarbon accumulations at Al-Laqitah area, Central Eastern Desert of Egypt. Appl. Radiat. Isot. J. 132, 38–46. https://doi.org/10.1016/j.apradiso.2017.10.053. Oasis Montaj program, 2015. Geosoft Mapping and Application System. Inc, Suit 500, Richmond St. West Toronto, On Canada N5SIV6. Sadek, H.S., 1972. Regional Radiometric Survey of East Luxor Area and its Relation to Stratigraphy and Regional Geology. unpublished M. Sc. Thesis. Faculty of science, Cairo university, Giza, Egypt, 131 pp. Sarma, D.D., Kock, G.S., 1980. A statistical analysis of exploration geochemical data for uranium. Math. Geol. 12 (2), 99–114. Youssef, M.A.S., Elkhodary, sh T., 2013. Utilization of airborne gamma ray spectrometric data for geological mapping, radioactive mineral exploration and environmental monitoring of southeastern Aswan city, South Eastern Desert, Egypt. Geophysics. J. Intell. 195, 1689–1700. Advance Access publication 2013 October 12.
5. Conclusions The high-sensitivity airborne spectrometry survey data were useful for the surface geology of the study area by tracing total count map and radioelements composite image map. This technique was applied to the spectrometry data to facilitate the correlation and delineation of litho logic units based on subtle differences in the radioelements concentra tions. The method showed practical success to map various sedimentary contacts, for large exposed area that have heterogeneity composition and affected the main structure. The radio-spectrometric measurements recorded over the study area vary widely from 1.44 to 33.6 Ur for T.C., 0.4–34 ppm eU, 0.8–13.8 ppm eTh and 0.1–0.9 K%. This wide variation reflects the fact that the study area is covered by sedimentary rocks of various compositions. Generally, Duwi Formation possesses the highest radioactivity levels in the study area while conglomerates, Tarawan Formation and Esna Formation have low radioactivity levels in the study area. The study area shows that there is a close relationship between the distribution of the radioelements and the lithology. The main results of the statistical treatment are that the lowest CV% values for TC reflect the high degree of homogeneity of data after separation by grid peaks of the difference technique. In addition, the second order difference technique is applied as a suitable order to delineate various rock unit boundaries and subdivided into analyze in detail subrock units for one formation as shown in the interpreted lithologic rock unit map. The new subrock units reflect highly homogeneity by lower values of CV%. The NW-SE trend seems to be the most important trend, which plays an effective role in the structural framework of the study area, and could be considered valuable as mineralization zones of economic importance. Acknowledgments I would like to thank Prof. Ahmed S. A. Abo El-Ata and Prof. Qadry M. Foad for suggesting a number of improvements in this manuscript. I also would like to extend my thanks to Prof. Atef A. M. Ismail and Prof. Ahmed A. Nigm for his help in discussing the new technique of aerial
9
Contents lists available at ScienceDirect
Applied Radiation and Isotopes journal homepage: http://www.elsevier.com/locate/apradiso
Order differences to enhance the delineation of rock units boundaries by using aerospectrometric data of Wadi Al Mushash area, Central Eastern Desert, Egypt: A new approach Mohamed A.S. Youssef Nuclear Materials Authority, Exploration Division, Po. Box 530, Maadi, Cairo, Egypt
A R T I C L E I N F O
A B S T R A C T
Keywords: Aerospectrometric data Composite image Differences technique
The present work utilizes airborne gamma-ray spectrometric data, in a trial to refine the surface geological mapping of sedimentary rocks at Wadi Al Mushash, Central Eastern Desert of Egypt. The acquired aerospec trometric data were supported by the surface geology concerning the study area. This area is mainly covered by sedimentary rocks of Tertiary to upper Cretaceous as Nubian Sandstone Formations (Quseir Clastics and Tarif Sandstone), Duwi Phosphates Formation, Dakhla Shale Formation, Esna Shale Formation, Tarawan Formation, Thebes Formation, and Quaternary deposits. High-resolution airborne gamma-ray spectrometry can be very helpful in mapping the surface geology. The method provides estimation of the apparent surface concentrations of the most common naturally occurring radioactive elements, such as potassium (K), equivalent uranium (eU) and equivalent thorium (eTh). This work is based on the assumption that, the absolute and relative concentra tions of these radioelements vary measurably and significantly with lithology. The composite image technique is used to display and simulate three parameters of the radioelements concentrations. The technique offered much in terms of lithologic discrimination, based on color differences and showed efficiency in defining areas, where different lithofacies occur within areas mapped as one continuous lithology. The Differences technique is used to delineate contacts of the rock units and the mainly structures of the study area. It is based mainly on varying in change of concentration of successive total count measurements within each line in the study area. Then, a suitable difference order is selected and matched to original measured line. Moreover, plotting the suitable order as grid and applied grid peaks on this grid. Then, these ridge grid peaks are symbolized over surface geological information and prepared radioelement composite map. This provides more detail about the surface geology, and addition more contacts occurred within original rock units. These subdivisions of rock units may be related to one formation that consists of more than one member having a different composition.
1. Introduction The study area is located on the eastern part of the Nile Valley, Central Eastern Desert that bounded by latitudes 25� 350 and 25� 470 N and longitudes 33� 000 and 33� 230 E (Fig. 1). Airborne gamma-ray spectrometric data can be used for surface geological mapping (Gra ham and Bonham-carter, 1993; Andrson and Nash, 1997; Jaques et al., 1997; Charbonneau et al., 1997; Youssef and Elkhodary, 2013). Gamma-ray spectrometric data have been applied, with variable degrees of success, for mapping lithological units and enhancing radioelement patterns within the individual units (IAEA, 2003). Darnley and Ford (1989) showed that, in many situations, gamma-ray spectrometry is probably more useful than any other single airborne geophysical method
in providing information directly interpretable in terms of surface ge ology. Elawadi et al. (2004) stated “the interpretation of radioelements distribution for mapping the surface geology is based on the assumption that, different rock types are composed of certain amounts of rock-forming minerals, which comprise specific quantities of radioactive elements.” The relationship between the radioelement content of the surficial material and the composition of the bedrock must be inferred by considering complementary evidence, provided by geological maps, satellite imagery, or ground inspection (see Fig. 2). The present study aims to recognize and identify the contact zones between various rocks and to remap the surface geology in the area. Moreover, it sheds light on the radio-spectrometric anomalies that may be related to these geologic contacts or associated geologic units.
E-mail address: [email protected]. https://doi.org/10.1016/j.apradiso.2019.108938 Received 29 July 2018; Received in revised form 10 October 2019; Accepted 11 October 2019 Available online 13 October 2019 0969-8043/© 2019 Elsevier Ltd. All rights reserved.
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the study area (Fig. 2) has been published by the Geological Survey of Egypt (1992). The Quseir Formation is composed of fine-grained variegated shale with minor bioclastic limestone and phosphate beds of shallow marine origin. It occupies the northeastern part of the area. The Tarif Formation is composed of fine-to medium-grained sandstone with interbedded channel and soil deposits. The Upper Cretaceous Duwi Phosphate For mation is composed of a sequence of alternating beds of claystone, sandstone, calcareous mudstone, siltstone, siliceous mudstone. It has gained special importance because of its high contents of uranium mineralization related to the phosphates of this Formation. The Dakhla Formation is composed of dark gray shallow marine marl and shale with limestone intercalations. The Tertiary sedimentary rocks are repre sented in the study area by Esna Formation, Tarawan Formation, Thebes Formation, and conglomerates. The Esna Formation is a sequence of greenish gray open marine shale that is calcareous. The Tarawan For mation is composed of white chalk limestone containing beds of marl. The Thebes Formation consists of thinly bedded outer shelf chalk and chalky limestone rich in chert band. The conglomerates form a thick sequence of well-rounded pebbles and boulders. They are highly weathered, fractured and faulted and widely distributed in the western part of the studied area. The Quaternary deposits and recent sediments fill the main wadies in the surveyed area. They are composed of allu vium and the Nile terrace series (Sadek, 1972). The wadi deposits filling the wadies include sands, pebbles, and boulders as a result of the weathering and denudation processes for the surrounding hills.
Fig. 1. Map of Egypt showing the location of the study area.
Consequently, the surface geological setting of these different rock units could be remapped by integrating spectrometry maps of the three ra dioelements and composite images as well as the geologic map of the study area. The topography of the area is not highly rugged and is formed of a moderate hilly country that rises gradually in altitude eastwards. The geomorphology is closely connected with the geological structures and lithology of the study area. The trends of most wadis are generally controlled by structural elements and rock contacts.
3. Airborne gamma-ray spectrometric survey The study area was considered for the systematic airborne geophysical survey conducted by Aero-Service Division, Western Geophysical Company of America, in 1984. It was conducted along parallel flight lines oriented in the NE-SW direction at approximately 1.5-km line spacing and 120 m ground clearance. A high-sensitivity 256 channel airborne gamma-ray spectrometer was used to carry out the γ-ray spectrometric survey (Aero-Service, 1984a,b). The obtained
2. Geologic setting The study area is generally covered by Nubian Sandstone Formations (Quseir Clastics and Tarif Sandstone), Duwi Phosphate Formation, Dakhla Shale Formation, Esna Shale Formation, Tarawan Formation and Thebes Formation as well as Quaternary deposits. The geologic map of
Fig. 2. Geologic map of the study area (after the Egyptian geological survey, 1992). 2
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Fig. 3. Total count fill colored contour map (in Ur).
Fig. 4. Potassium fill colored contour map (in %).
airborne gamma-ray spectrometric data were compiled and presented in the form of contoured maps of scale 1:50,000. The data were corrected for background radiation resulting from cosmic rays and aircraft contamination, variations caused by changes in aircraft altitude relative to ground, and Compton scattered gamma-rays in potassium and uranium energy windows. The corrected data provide an estimate of the apparent surface concentrations of potassium, ura nium and thorium (K, eU, and eTh), respectively as well as Total count (TC).
2 The difference technique is applied and a suitable order is selected to separate the edges of different rock units and major structures (may be lineaments) of the present study. 3 Statistical analysis is performed for parameters, such as minimum (Min.) and maximum (Maxi.), calculated arithmetic mean (X), and standard deviation (S), as well as checking the normality of distri bution of their measurements by using the coefficient of variability (CV%) were applied for new separated subrock units by symbolized grid peaks of the second-order difference.
4. Data analysis and interpretation 4.1. Qualitative interpretation of the airborne γ-ray spectrometric maps
1 Contour maps of radioelements (K, eU, and eTh), TC contour maps, and radioelement composite image map of (K, eU and eTh) are plotted and prepared using Oasis Montaj Program V.8.3 (2015).
Gamma-ray spectrometric maps (Figs. 3–7) emphasize the nature of the radioelement distributions and are thus better suited to the recog nition of geological features. These maps show a general relation to the rock units and the structural trends prevailing in the study area. 3
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Fig. 5. Equivalent uranium fill colored contour map (in ppm).
Fig. 6. Equivalent thorium fill colored contour map (in ppm).
Radioelement (K, eU and eTh) contour maps were prepared and care fully inspected and composite radioelements image map were inter preted qualitatively. Examination of the aerospectrometric maps reveals the existence of a wide range of variation in the aeroradioactivity levels, which reflects the fact that the area under study is covered by rocks of various compositions. It is evident from the correlation between the different rock units and the recorded levels of gamma radiation over them that, the pattern of aeroradioactivity is closely connected with the surface geology of the area.
relative potassium concentration in the area. It indicates that the eastern parts of wadi sediments, Tarif Formation, Duwi Formation and Quseir Formation have the highest level of potassium contents (more than 0.65%), while the intermediate level of potassium contents, which ranges from 0.4% to 0.65%, is present in some western parts of wadi deposits and some parts of the Duwi Formation. The lowest level (down to 0.4%) is associated to Esna Formation, Dakhla Formation, Thebes Formation and conglomerates in which their boundaries can be detected. The eU map (Fig. 5) classified into three levels: the first level has range of 4.5 to 34 ppm and associated with wadi deposits and the Duwi Formation. The equivalent uranium (eU) content reaches 34 ppm as the maximum value over the Duwi Formation, and diminishes to 0.4 ppm as the minimum value over conglomerates with a mean of 4.5 ppm. The intermediate radioactive levels range from 2 to 4.5 ppm and associated mainly with the Tarif Formation, some parts of wadi deposits, Tarawan Formation and Esna Formation. The low radiometric levels, with values less than 2 ppm, extend over Dakhla Formation, Thebes Formation, and
4.1.1. Radioelement contour maps The TC map (Fig. 3) was classified into three levels: The TC content reaches 33.6 Ur as the maximum value over the Duwi Formation. The intermediate radioactive levels range from 4.5 to 8.5 Ur and associated mainly with the Tarif, Esna and Quseir Formations. The low radiometric levels, with values less than 4.5 Ur, extend over Dakhla, Tarawan and Thebes Formations as well as conglomerates. The K map (Fig. 4) shows the overall spatial distribution of the 4
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Fig. 7. Composite image of radioelements.
conglomerates. In addition, the eTh map (Fig. 6) is divided into three levels: the first one ranges from 4.5 to 13.8 ppm and associated with the Tarif Forma tion, Duwi Formation, Wadi deposits and Quseir Formation. The second level ranges from 3 to 4.5 ppm and restricted to the western part of the Duwi Formation and some parts of conglomerates. The lowest eTh level is less than 3 ppm which is mostly associated with the Conglomerates, Dakhla Formation, Tarawan Formation, and Esna Formation.
represent the K (in %), eU (in ppm) and eTh (in ppm) concentrations. Here, the blue color represents eU, green for eTh, and red for K. At any location, the relative concentrations of the three radioelements are represented by the color hue produced by mixing appropriate amounts of the three ink colors (Broome, 1990; IAEA, 2003; Youssef and Elkho dary, 2013; Nigm et al., 2018). Regions with relatively high concen trations of the three radioelements look white; while those with relatively low concentrations look dark gray. The color index at each corner of the triangular legend (K in red, eU in blue and eTh in green) indicates 100% concentration of the indicated radioelement. Colors at each point inside the triangle represent different ratios of the radioele ments according to their color differences on the absolute composite image of the three radioelements. The Quseir Formation and Tarif Formation are characterized by their strong K and eTh contents that are clearly visible on the ternary radio element map (Fig. 7) by a yellowish color at the eastern part of the study area. The blue areas indicate uranium-rich areas in Duwi Formation. The western part of the studied area shows black areas of weak radioelement contents as indicative to the low radioactive rocks such as Tarawan Formation, Thebes Formation, Esna Formation and conglomerates.
4.1.2. Ternary map A ternary map is a color composite image generated by modulating the red, green and blue phosphors of the display device or yellow, magenta, and cyan dyes of a printer in proportion to the radioelement concentration values of K, eTh, and eU. The ternary map is a useful geological tool and mineral exploration for discriminating zones of consistent lithology and contacts between contrasting lithologies (Duval, 1983). However, composite color image maps are prepared as follows different rock types have different characteristic concentrations of the three main radioelements. Composite image map of the three radioelements (Fig. 7) is produced by using different ink colors to
Fig. 8. Symbols of grid peaks of second-order differences. 5
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Fig. 9. Symbols of grid peaks of second-order differences over the total count map.
Fig. 10. Symbols of grid peaks of the second-order differences order over the composite map of radioelements.
4.2. Difference technique procedures
D4 (V (i)) ¼ V(iþ2) - 4V(iþ1) þ 6V(i) - 4V(i-1) þ V(i-2) for the fourth-order difference
Use the difference filter using Oasis Montaj version Ver.8.3 to calculate differences between values in a channel. First, TC channel of line within the study area is selecting input. Second, the difference channel is calculated and outputted as the first-order difference, secondorder difference, third-order difference, and so on (number of differ ences > or ¼ 1). Even numbers of differences produce properly located results. Odd numbers of differences will locate the result 1/2 element below the actual location. The difference filter is calculated by the subtraction of the successive data values of the channel, difference database tools within Oasis Montaj program, V. 8.3, 2015:
After applying the first, second, third, and fourth orders for each TC lines within the study area, the second order difference filter is selected as the best order compatible with original total count profiles; then the second order was plotted as the grid without applying any trans formation, followed by applying level of peak detection or grid peak (Blakely and Simpson, 1986) method to find peaks in a grid as normal grid values in all the nearest grid cells are lower from the selected dif ference order. Moreover, symbolized grid peaks compared to previous grid maps, show more for different rock units, and their boundaries and major structures. Fig. 8 shows symbols of grid peaks on a free base map and then plots this grid peaks over the total count map (Fig. 9), over composite map of radioelements (Fig. 10), as well as over geologic map (Fig. 12) to show a good matching and emphasizes delineation symbolized grid peaks for
D1(V (i)) ¼ V(iþ1) - V(i) for the first-order difference D2 (V (i)) ¼ V(iþ1) - 2V(i) þ V(i-1) for the second-order difference D3 (V (i)) ¼ V(iþ2) - 3V(iþ1) þ 3V(i) -V(i-1) for the third-order difference 6
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Fig. 11. Symbols of grid peaks of second-order differences over the new interpreted lithologic unit map.
Fig. 12. Symbols of grid peaks of second-order differences over the geologic map.
each subrock units with geologic map for creating a new interpreted lithologic units map and inferred faults. Figs. 11 and 13 illustrate nine inferred faults (F1–F9) trending in the NW-SE direction parallel to the main structure of the study area. In addition, it distinguished one to several subrock unit contacts then checked, and matched with TC (Fig. 9) and radioelement composite map (Fig. 10). Accordingly, the Duwi Formation subdivided into six subrock units (D1-D6), Wadi deposits subdivided into seven subrock units (W1–W7), Dakhla Formation classified into two subunits, conglomerates subdivided into five subrock units (C1–C5), and Quseir Clastics
subdivided into six subrock units (Q1-Q6). Tarif Sandstone as well as Esna and Tarawan Formation cannot be separated into more than one rock unit because their low radioactivity. Conglomerates, Wadi deposits, Quseir Clastics and Duwi Formation are noticed a good agreement for contacts with their symbols of grid and the NW-SE trend structural. 4.3. Quantitative interpretation In this study, the quantitative interpretation depends principally upon the fact that, the absolute and relative concentrations of the 7
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Fig. 13. Interpreted lithological unit map deduced from grid peaks of the second-order difference technique. Table 1 Statistical analysis of the Total count in the different lithologic units of the study area. Rock units
Age
Sub-rock units
NO.
Min.
Max.
X
S
CV (%)
Wadi deposits (W1–W7)
Quaternary
Conglomerates (C1–C5)
Tertiary
Esna and Tarawan Formation Dakhla Formation (K1–K2)
Upper Cretaceous
W1 W2 W3 W4 W5 W6 W7 C1 C2 C3 C4 C5 E&T K1 K2 D1 D2 D3 D4 D5 D6 Q1 Q2 Q3 Q4 Q5 Q6 Q7 T1
72 47 32 247 40 529 21 74 587 213 874 269 117 170 187 60 487 958 874 296 309 141 570 579 228 197 882 143 297
3.2 3.9 3.2 6.4 1.9 6.1 6.7 2.3 2.7 2.5 1.8 3 3 2.9 2.7 3.3 3.1 2.8 1.8 6.5 2.4 6.6 7.1 6 6.5 6.2 6.4 5.1 5.9
11.1 7.3 5.3 12.5 10.1 11.2 7.6 4.3 10.8 4.9 29.4 5.2 4.9 7.3 14.1 4.3 6.3 14 29.4 9.6 33.1 9.3 12.1 12.4 12.2 20.5 19.2 8.6 9.7
4.5 5.4 4.4 9 4.9 8.6 7.1 3.2 4.4 3.6 11.3 4.1 3.8 4.8 5.6 3.9 4.7 5.2 11.3 7.7 14.8 8.2 9.2 8.6 9.6 9.9 9.6 6.7 7.4
1.3 0.7 0.5 1.1 2.2 086 0.26 0.47 1.2 0.57 6.2 0.46 0.45 1.16 3 0.26 0.59 1.1 6.2 0.7 5.8 0.57 0.96 1 1.4 2.8 1.8 0.89 0.67
20 14 12.4 12.4 44 9.9 3.7 14.5 28 15.7 54.5 11 11.7 24 53.5 6.7 12 22 54.5 9.2 39 7.9 10 11.4 15.4 28 18 13 9
Duwi Formation (D1-D6)
Quseir Formation (Q1-Q7)
Tarif Formation (T1)
Explanation: NO. ¼ Number of samples, Min. ¼ Minimum Value, Max. ¼ Maximum Value, (X) ¼ Mean, (S) ¼ Standard Deviation and CV ¼Coefficient of Variability (%).
radioelements (K%, eU and eTh) vary measurably and significantly with new separated boundaries of lithologic units. Statistical computation was applied to the original spectrometric data without applying any transformation, in accordance with the recommendation given by Sarma and Kock (1980). A composite file was prepared to include four columns (TC, K, eU and eTh) and rows of sample points. Standard statistics were applied to the raw data to compute means, minimums, maximums, range, standard
deviations and homogeneity distribution check for each variable (Table 1). The statistical treatment of the airborne gamma-ray spectrometric data depends mainly on the application of the coefficient of variability (CV) technique for a certain variable value in the study area and check on homogeneity distribution. Statistical analysis was applied on all new separated subrock units for the total count of each rock unit according to the new separating boundaries by the difference technique. Table (1) 8
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gamma ray data in joining collecting materials of this paper. Finally, many thanks to Nuclear materials authority (NMA), Editor and re viewers of applied radiation and isotopes journal.
summarizes the statistical results of the total count over the seven rock units in the study area. The careful examinations of quantitative calcu lations were regarding the degree of homogeneity of the distribution of the total count for the different lithologic rock units. The increase in detailing of the rock constituents can be improved of new subunits for one unit by lower CV% values that mean the higher degree of homogeneity. The careful examinations of quantitative calculations were regarding the degree of homogeneity of the distribution of the TC of radioactivity within each separating subrock units. In the present study, the lower CV % values mean the higher degree of homogeneity that reflects a good agreement for separation of subrock units.
Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.apradiso.2019.108938. References Aero-Service, 1984. Interpretation Report of Airborne Gamma-Ray Spectrometer and Magnetometer Survey of the Eastern Desert of Egypt, 127pp. Aero-Service, 1984. Final Operational Report of Airborne Magnetic/radiation Survey in the Eastern Desert, Egypt for the Egyptian General Petroleum Corporation. AeroService, Houston, Texas. April, 1984, Six vol. s. Andrson, H., Nash, C., 1997. Integrated lithostructural mapping of the Rossing area, Namibia using high resolution aeromagnetic, radiometric, Landsat data and aerial photographs. Explor. Geophys. 28, 185–191. Blakely, R.J., Simpson, R.W., 1986. Approximating edges of source bodies from magnetic or gravity anomalies. Geophysics 51 (7), 1494–1498. Broome, H.J., 1990. Generation and interpretation of geophysical images with examples from the rae provinces, northwestern Canada shield. Geophysics 55 (8), 977–997. Charbonneau, B.W., Holman, P.B., Hetu, R.J., 1997. Airborne gamma spectrometer magnetic-VLF survey of northeastern Alberta. In: Exploring for Minerals in Alberta: Geological Survey of Canada Geoscience Contributions, Edited by Mac Queen, Canada-Alberta Agreement on Mineral Development, vol. 500. Geological Survey of Canada, Bulletin, pp. 107–132. Darnley, A.G., Ford, K.L., 1989. Regional airborne gamma-ray surveys. In: Garland, G.D., Ontario (Eds.), A Review in Proceedings of Exploration, 87: Third Decennial International Conference on Geophysical and Geochemical Exploration for Minerals and Groundwater, vol. 3. Geological Survey of Canada, Special, 960 pp. Duval, J.S., 1983. Composite color images of aerial gamma-ray spectrometry data. Geophysics 48, 722–735. Elawadi, I.A., Ammar, A.A., Elsirafy, A., 2004. Mapping surface geology using airborne gamma-ray spectrometric survey data – a case study. In: Proc.The 7th SEGI International Symposium-Imaging Technology, Sendai, Japan, pp. 349–354. Geological Survey of Egypt, 1992. Geological Map of Wadi Barramiyah Quadrangle, Egypt, Scale 1:250000. EGSMA, Cairo. Graham, D.F., Bonham-carter, G.F., 1993. Airborne radiometric data: a tool for reconnaissance geological mapping using a GIS. Photogramm. Eng. Remote Sens. 58, 1243–1249. IAEA, 2003. Guidelines for Radioelement Mapping Using Gamma-Ray Spectrometry Data. IAEA-TECDOC-1363, VIENNA, 179pp. Jaques, A.I., Wellman, P., Whitaker, A., Wyborn, D., 1997. High resolution geophysics in modern geological mapping. AGSO J. Aust. Geol. Geophys. 17, 159–174. Nigm, A.A., et al., 2018. Airborn gamma-ray spectrometric data as guide for probable hydrocarbon accumulations at Al-Laqitah area, Central Eastern Desert of Egypt. Appl. Radiat. Isot. J. 132, 38–46. https://doi.org/10.1016/j.apradiso.2017.10.053. Oasis Montaj program, 2015. Geosoft Mapping and Application System. Inc, Suit 500, Richmond St. West Toronto, On Canada N5SIV6. Sadek, H.S., 1972. Regional Radiometric Survey of East Luxor Area and its Relation to Stratigraphy and Regional Geology. unpublished M. Sc. Thesis. Faculty of science, Cairo university, Giza, Egypt, 131 pp. Sarma, D.D., Kock, G.S., 1980. A statistical analysis of exploration geochemical data for uranium. Math. Geol. 12 (2), 99–114. Youssef, M.A.S., Elkhodary, sh T., 2013. Utilization of airborne gamma ray spectrometric data for geological mapping, radioactive mineral exploration and environmental monitoring of southeastern Aswan city, South Eastern Desert, Egypt. Geophysics. J. Intell. 195, 1689–1700. Advance Access publication 2013 October 12.
5. Conclusions The high-sensitivity airborne spectrometry survey data were useful for the surface geology of the study area by tracing total count map and radioelements composite image map. This technique was applied to the spectrometry data to facilitate the correlation and delineation of litho logic units based on subtle differences in the radioelements concentra tions. The method showed practical success to map various sedimentary contacts, for large exposed area that have heterogeneity composition and affected the main structure. The radio-spectrometric measurements recorded over the study area vary widely from 1.44 to 33.6 Ur for T.C., 0.4–34 ppm eU, 0.8–13.8 ppm eTh and 0.1–0.9 K%. This wide variation reflects the fact that the study area is covered by sedimentary rocks of various compositions. Generally, Duwi Formation possesses the highest radioactivity levels in the study area while conglomerates, Tarawan Formation and Esna Formation have low radioactivity levels in the study area. The study area shows that there is a close relationship between the distribution of the radioelements and the lithology. The main results of the statistical treatment are that the lowest CV% values for TC reflect the high degree of homogeneity of data after separation by grid peaks of the difference technique. In addition, the second order difference technique is applied as a suitable order to delineate various rock unit boundaries and subdivided into analyze in detail subrock units for one formation as shown in the interpreted lithologic rock unit map. The new subrock units reflect highly homogeneity by lower values of CV%. The NW-SE trend seems to be the most important trend, which plays an effective role in the structural framework of the study area, and could be considered valuable as mineralization zones of economic importance. Acknowledgments I would like to thank Prof. Ahmed S. A. Abo El-Ata and Prof. Qadry M. Foad for suggesting a number of improvements in this manuscript. I also would like to extend my thanks to Prof. Atef A. M. Ismail and Prof. Ahmed A. Nigm for his help in discussing the new technique of aerial
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