The present study deals with the analysis and interpretation of the results of field geophysical survey and laboratory geophysical measurements. The study of the magnetic and electrical methods was selected because the beach sands contain many minerals that have magnetic and electric properties. Analysis and interpretation of the field and laboratory magnetic and geoelectric maps demonstrated that the investigated beach-alluvial deposits can be subdivided according to their magnetic and geoelectric properties into three main zones striking nearly parallel to the shoreline of the Mediterranean Sea at the study area. The northern zone is more enriched in black sands than the central or southern zones. Field and laboratory magnetic susceptibility measurements provided very useful maps for the concentration of heavy minerals. The deep-seated magnetic response was calculated at an average depth of 239.6？m, while the near-surface magnetic responses were computed at average depths of 9.1, 57.9, and 81.8？m, respectively. The correlation between the geophysical features, recorded on the total magnetic field intensity, the electric resistivity, the IP chargeability, and the calculated metal factor, was found to agree to a great extent. The heavymineral concentration was found to decrease with depth. However, the heavyminerals show parallel zones below the surface, suggesting similar sedimentation environments. 1. Introduction The alluvial-beach placer deposits, East Rosetta, Mediterranean Sea Coast, Northern Egypt, are known for their enhanced natural radiation environment, due to the presence of radiogenic heavy minerals, such as monazite and zircon, which contain Th and U in their chemical composition [1]. The placer deposits are well known as sources for economic heavy minerals and nuclear raw materials, in addition to their importance in many of the strategic, metallurgical, and engineering industries. The mineralogical analyses identified six main heavy mineral sands accompanied by traces of cassiterite and gold as well as some minerals of rare earth elements (REEs). According to their relative frequencies, the six heavy minerals include ilmenite, magnetite, zircon, monazite, garnet, and rutile. The study area (30°32′10′′E and 30°34′08′′E long.; 31°26′59′′N and 31°27′59′′N lat.) extends over a length of 3.0？km, trending in an E-W direction along the Mediterranean Sea Coast, with an average width of more than 1.8？km (Figure 1). Figure 1: Map of Northern Egypt showing the location of the study area. The main objectives of the present study are(1)evaluation of
References
[1]
A. A. Ammar, A. S. Sharaaky, A. N. Shahein, M. A. El-Sadek, and S. A. Elkhateeb, “Radiolithologic studies on beach and alluvial black-sand deposits, Koam Mashaal area, Egypt, using ground radiospectrometry,” in Proceedings of the 1st International Conference on the Geology of Tethys, vol. 1, pp. 125–136, Cairo University, 2005.
[2]
J. B. Hedrick and L. Waked, “Heavy minerals, including monazite, in Egypt's black sand deposits,” Journal of The Less-Common Metals, vol. 148, no. 1-2, pp. 79–84, 1989.
[3]
A. F. Elhadary, Geological, sedimentological and radiometric studies on the black-sand deposits, west Rosetta beach, with emphasis on the heavy economic minerals, Ph.D. thesis, Faculty of Science, Cairo University, Geiza, Egypt, 1998.
[4]
A. A. Abu-Diab, Sedimentological studies and economic evaluation of the coastal sand dunes between Elgadia and Idko, Rosetta, Egypt, Ph.D. thesis, Faculty of Science, Mansuora University, Mansuora, Egypt, 2001.
[5]
M. A. El-Sadek and S. A. Elkhateeb, “Magnetic susceptibility of black-sand beach deposits,” Koam Mashaal area, east Rosetta, Egypt, Internal Report Series, NMA-IRS-3/2002, Cairo, Egypt, 2002.
[6]
A. F. Bakheit, Mineralogy and concentration of economic heavy minerals, northern Delta, Egypt, Ph.D. thesis, Cairo University, Geiza, Egypt, 2004.
[7]
M. I. Moustafa, “Chemistry and origin of enigmatic monazite and chevkinite/perrierite in the egyptian black beach sand,” Resource Geology, vol. 60, no. 3, pp. 271–287, 2010.
[8]
M. A. El Askary and O. E. Frihy, “Depositional phases of rosetta and damietta promontories on the Nile Delta coast,” Journal of African Earth Sciences, vol. 5, no. 6, pp. 627–633, 1986.
[9]
A. F. Elhadary, Geologic and radiometric investigations on Abu-Khashaba deposits, east Rosetta, Egypt, Ph.D. thesis, Geology Department, Faculty of Science, Cairo University, Geiza, Egypt, 1988.
[10]
GM. SYS. Program, “Definitive International Geomagnetic Reference Field, Version 1.5,” Computation Routines by Mike Gemperle and Rowland B. French, Interface by Pierre Doguin, Northwest Geophysical Associates Inc., 1997.
[11]
F. O. Badokhon, Geophysical exploration for oolitic iron deposit extensions in the northern part of Wadi Ash-Shumaysi, Saudi Arabia, Ph.D. thesis, King Abdulazeiz University, Jeddah, Saudi Arabia, 1998.
[12]
G. Brno, Instruction Manual of Kappa Meter KT6, Geofyzika Brno, Brno, Czech Republic, 1998.
R. Thompson and F. Oldfield, Environmental Magnetism, Allen and Unwin, London, UK, 1986.
[15]
B. A. Maher, R. Thompson, and M. W. Hounslow, “Introduction,” in Quaternary Climates, Environments and Magnetism, B. A. Maher and R. Thompson, Eds., pp. 1–48, Cambridge University Press, Cambridge, UK, 1999.
[16]
M. E. Evans and F. Heller, Environmental Magnetism: Principles and Applications of Enviromagnetics, Academic Press, London, UK, 2003.
[17]
J. Lees, “Evaluating magnetic parameters for use in source identification, classification and modelling for natural and environmental materials,” in Environmental Magnetism: A Practical Guide, J. Walden, F. Oldfield, and J. P. Smith, Eds., pp. 113–138, Quaternary Research Association, Cambridge, UK, 1999.
[18]
J. A. Dearing, “Natural magnetic tracers in fluvial geomorphology,” in Tracers in Geomorphology, I. D. L. Foster, Ed., pp. 57–82, John Wiley & Sons, London, UK, 2000.
[19]
P. Kearey and M. Brooks, An Introduction to Geophysical Exploration. Geoscience Texts, Blackwell Science, London, UK, 2nd edition, 1998.
[20]
S. Treitle, W. C. Clement, and R. K. Kaul, “Specteral determination of depth to buried magnetic basement rocks,” Geophysical Journal of the Royal Astronomical Society, vol. 24, no. 4, pp. 415–428, 1971.
[21]
M. Muniruzzaman and R. J. Banks, “Basement magnetization estimates by wavenumber domain analysis of magnetic and gravity maps,” Geophysical Journal, vol. 97, no. 1, pp. 103–117, 1989.
[22]
A. Spector and F. S. Grant, “Statistical models for interpreting aeromagnetic data,” Geophysics, vol. 34, no. 1, pp. 193–302, 1970.
[23]
H. S. Sadek, “Profile frequency analysis of potential field data using filon fourier transform, with basic software,” in Proceedings of the 5th International Seminar on Model optimization in Exploration Geophysics, Free University of Berlin, 1987.
[24]
H. R. Burger, Exploration Geophysics of the Shallow Subsurface, Prentice Hall International, London, UK, 1992.
[25]
D. H. Griffiths and R. F. King, Applied Geophysics for Geologists and Engineers. The Elements of Geophysical Prospecting, Pergamon Press Ltd., Headington Hill Hall, Oxford OX30BW, England, UK, 1981.
[26]
W. Lowrie, Fundamentals of Geophysics, Cambridge University press, 1997.
[27]
D. S. Parasnis, Principles of Applied Geophysics, Chapman and Hall, A Halsted Press Book, London, UK, 3rd edition, 1979.
