High resolution airborne radiometric and magnetic studies of ilesha and its environs, southwestern Nigeria

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The study of the nature of distribution of natural radioelements in Ilesha and its environs with its geological structure has been studied using aeroradiometric data. Aeromagnetic data have also been subjected to three automated gradient techniques to delineate the sub-surface structure of the study area. From the study, it can be found that maximum values of “eU” (ppm) and “eTh” (ppm) fall within the branded gneiss, whereas the maximum value of K (%) falls within porphyritic granite regions. eTh had the highest radioactive content. The environmental dose rate of Ilesha was between 0.1817 and 3.9296 msv/yr. Although there were extreme values, but the mean dose rate was 0.522 ± 0.310 msv/yr (within acceptable safe limit of 1.0 msv/yr). eU/K, eU/eTh and eTh/K ratios were analysed for enrichment or depletion of radioisotopes. eU/eTh >1 showed uranium depletion, while eTh >2 showed eTh enrichment. The magnetic intensity values ranged from -79.41 to 140.93 nT. The horizontal gradient method (HGM) and analytic signal amplitude (ASA) revealed that depth to magnetic sources ranged from 0.478 to 4.112 km and 0.348 to 2.551 km, respectively, whereas local wavenumber (LWN) depth ranged from 0.478 to 5.48 km, which overestimated those compared using HGM and ASA functions. The apparent susceptibility ranged from -0.00325 to 0.00323 SI, showing that ferromagnetic and diamagnetic mineral ranges control apparent susceptibility in Ilesha.

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  • [1] El-Sadek M.A. Ammar A.A. Sabry A.R. (2002): Aeroradiospectrometry in the Lithological Mapping and Environmental Monitoring of Wadi Araba Area. The Arabian Journal for Science and Engineering 27(2A) pp. 131–148.

  • [2] Grasty R.L. Carson J.M. Charbonneau B.W. Holman P.B (1984): Natural Background Radiation in Canada. Geological Survey of Canada Bulletin 360 pp. 39–60.

  • [3] Linden A. Melander A. (1986): Airborne Measurement in Sweden of the Radioactive Fallout After the Nuclear Reactor Accident in Chernobyl USSR Preliminary Report SGAB TFRAP 8606 1986.

  • [4] Akerblom G. (1987): Investigation and Mapping of Radon Risk Areas. In: Proceedings of the International Symposium Geological Mapping in Service of Environmental Planning 6–9 August 1986 F.C. Wolff (ed.) 1987.

  • [5] Wilford J. Minty B. (2006): The use of Airborne Gamma Ray Imagery for Mapping Soils and Understanding Landscape Processes. Developments in Soil Science 31 pp. 207–218.

  • [6] Gun P.J. (1975): Linear transformation of gravity and magnetic fields. Geophysical Prospecting 23(2) pp. 300–312.

  • [7] Dobrin M.B. (1976): Introduction to geophysical prospecting. New York: McGraw-Hill Book Company 630 p.

  • [8] Thurston J.B. Smith R.S. (1997): Automatic conversion of magnetic data to depth dip and susceptibility contrast using the SPITm method. Geophysics 62(3) pp. 807–813.

  • [9] Coetzee H. Larkin K. (2011): Airborne Radiometric Surveying for the Management of Health Safety and the Environment in the Uranium Mining Industry: Potential Applications and Limitations. B. Merkel M. Schipek The New Uranium Mining Boom 483–492.

  • [10] De Swardt A.J. (1953): The geology of the country around Ilesa. Geological Survey of Nigeria Bulletin 23 55 p.

  • [11] Rahaman M.A. (1976): Review of the basement geology of south western Nigeria. In: Geology of Nigeria Kogbe C.A (ed.). Elizabethan: Publishing Lagos.

  • [12] DeSwardt A.M.J. (1947): The Ife-Ilesa goldfield (Interim report number 2). Geology of Survey of Nigeria annual report pp. 14–19.

  • [13] Russ P. (1957): Airborne electromagnetics in review. Geophysics 22 pp. 691–713.

  • [14] Hurley S. (1970): Radar propagation in rock salt. Geophysical Prospecting 18(2) pp. 312–328.

  • [15] Ajayi T.R. (1981). On the geochemistry and origin of the amphibolites of Ife Ilesha area south west Nigeria. Journal of Mining and Geolology 17 pp. 176–179.

  • [16] Folami S.L. (1992): Interpretation of aeromagnetic anomalies in Iwaraja area south western Nigeria. Journal of Mining and Geology 28(2) pp. 391–396.

  • [17] Elueze A.A. (1986): Geology of the Precambranian Nigeria. Geological Survey of Nigeria pp. 77–82.

  • [18] Kayode J.S. (2009): Vertical component of the ground magnetic study of Ijebu-Ijesa southwestern Nigeria. A paper presented at the International Association of Seismologist and Physics of the Earth Interior (IASPEI) conference at Cape Town South Africa; Jan 10th-16th 2009.

  • [19] Helmy S.O.A. Monsour A. Al Garni (2015): Airborne Gamma-ray Spectrometric and Magnetic Studies of Wadi Um Gehig-Wadi Abu Eligam area Central Eastern Desert Egypt. Arabian Journal of Geoscience 8(10) pp. 8811–8833.

  • [20] Wilford J.R. Bierwirth P.N. Craig M.A. (1997): Application of airborne gamma-ray spectrometry. AGSO Journal Australian Geology and Geophysics 17(2) pp. 201–206.

  • [21] International Atomic Energy Agency (2003): Guidelines for radioelement mapping using gamma ray spectrometry. Vienna: International Atomic Energy Agency 173 p.

  • [22] Grasty R.L. Holman P.B. Blanchard Y.B. (1991): Transportable calibration pads for ground and airborne gamma–rays spectrometers. Geology Survey of Canada 90 pp. 23–24.

  • [23] Clarke S.P. Peterman Z.E. Heier K.S. (1966): Abundances in Uranium Thorium and Potassium. In: Handbook of Physical Constants. Geological Society of America 97: 521–541.

  • [24] Ramadass G. Subbash Babu A. Udaya Laxmi A. (2015): Structural Analysis of Airborne Radiometric. Data for Identification of Kimberlites in Parts of Eastern Dharwar Craton. International Journal of Science and Research 4(4) pp. 2375–2380.

  • [25] Tzortzis M. Tsertos H. (2004): Determination of thorium uranium and potassium elemental concentrations in surface soils in Cyprus. Journal of Environmental Radioactivity 77(3) pp. 325–328.

  • [26] UNSCEAR (2000): Sources and Effects of ionizing radiation. Report to General Assembly With Scientific Annexes New York: United Nations.

  • [27] Farai I.P. Jibiri N.N. (2000): Baseline studies of terrestrial outdoor Gamma Dose Rate level in Nigeria. Radiation Protection Dosimetry 88 pp. 247–254.

  • [28] Okeyode I.C. Rabiu J.A. Alatise O.O. Makinde V. Akinboro F.G. Alhazim D. Mustapha A.O. (2016): Area monitoring ambient dose rate in part of southwestern Nigeria using GPS-Integrated radiation survey meter. Radiation Protection Dosimetery 173(1) pp. 263–267.

  • [29] Blakely R.J. Simpson R.W. (1986): Approximating edges of source bodies from magnetic or gravity anomalies. Geophysics 51(7) pp. 1494–1498.

  • [30] Phillips J.D. (1997): Potential field geophysical software for P.C version 2.2. Open file report 97–725.

  • [31] Roest W.R. Pilkington M. (1993): Identifying remanent magnetization effects in magnetic data. Geophysics 58 (5) pp. 653–659.

  • [32] Nabighian M.N. (1972): The Analytic signal of two dimensional bodies with polygonal cross section-its properties and use for automated anomaly interpretation. Geophysics 37 pp. 507–517.

  • [33] Nabighian M.N. (1974): Addition comment on the analytic signal of two dimensional bodies with polygonal cross section-its properties and use for automated anomaly interpretation. Geophysics 39 pp. 85–92.

  • [34] Purucker M. (2006): Crustal Magnetism: Geophysics 5 Version 2.5

  • [35] Roest W.R. Verhoef J. Pilkington M. (1992): Magnetic interpretation using the 3-D analytic signal. Geophysics 57(1) pp. 116–125.

  • [36] MacLeod I.N. Jones K. Dai T.F. (1993): Analytic signal in the interpretation of total magnetic field data at low magnetic latitudes. Exploration Geophysics 24 pp. 679–688.

  • [37] Miller H.G. Singh V. (1994): Potential field tilt- A new concept for location of potential field sources. Journal of Applied Geophysics 32 pp. 213–217.

  • [38] Fairhead J.D. Green C.M. Verduzco B. MacKenzie C. (2004): A new set of magnetic field derivatives for mapping minerals prospects. SEG 17th Geophysics (2004).

  • [39] Verduzco B. Fairhead J.D. Green C.M. MacKenzie C. (2004): New insights into magnetic derivatives for structural mapping: The Leading Edge 23 pp. 116–119.

  • [40] Bracewell R. (1965): The Fourier transform and its applications. New York: McGraw – Hill Book Co. 474 p.

  • [41] Huang D. Versnel P.A. (2000). Depth estimation algorithm applied to FTG data. Society of Exploration Geophysics. Expanded Abstract pp. 394–397.

  • [42] Poirier J.P. (2000): Introduction to Physics of the earth interior. Cambridge: Cambridge University press 312 p.

  • [43] Phillips J.D. (2010): Locating magnetic contacts; A comparison of the horizontal gradient analytic signal and local wavenumber methods Society of Exploration Geophysics Annual General Meeting Calgary Alberta Expanded Abstracts.

  • [44] Olowofela J.A. Badmus B.S. Ganiyu S.A. Olurin O.T. Babatunde P. (2011): Source location and depth estimation from digitised aeromagnetic data acquired from the basement complex formation. Earth Science India 4 pp. 136–142.

  • [45] Geosoft INC. (2010). Geosoft INC. 85 Richmond Street 8th Floor Toronto Ontario Canada.

  • [46] Frantisek H. Jiri P. Jazek J. Chadina M. (2009): Out – of-Phase Magnetic Susceptibility of rocks and soil rapid tool for magnetic granulometry. Geophysical Journal International 194 pp. 170–181.

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