Abstract - Akamai University

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the presence of magnetic anomalous zones along four out of the six traverses established over the surveyed site (Figure 1) (Eluyemi et al., 2012). These anomalous zones display typical magnetic anomaly of a dyke-like body in low magnetic latitude (I < 3°) characterized by a magnetic low (negative polarity) flanked on both sides by low amplitude positive peaks. Such anomalous zones were delineated at the extreme north (NW and NE) and south central part and identified in rectangular blocks (Figure 1). The south central negative magnetic closure, identified across traverses 3 and 4, is located on a slag mound (along traverse 4) characteristic of an ancient ore smelting site. Similar anomalies, suspected to be iron ore smelting sites, observed along traverses 5 and 6, have no surface expression of slag mound. This study involved soil sampling from five suspected iron ore smelting sites and two from non-anomalous magnetic zones serving as control (Figure 1), for elemental analysis with Energy Dispersive X-Ray Fluorescence (XRF). The study is predicated on the assumption that soil samples from an ancient iron ore smelting site will be characterized by relatively high concentration of iron (Fe) than the surrounding environment due to decomposed iron-fillings and other decomposable objects made of metal. Iron decomposes or corrodes when it is left or abandoned for a long period of time in the presence of moisture, oxygen, and elevated temperature. The process of the decomposition can be expressed with the equation: 4 Fe +3O2 H 2 2 2 3 O Fe . O → However, the same process holds for copper, zinc, and other metallic objects, but the rate of the decomposition may be a bit slower than in iron. The decomposed metal is found saturated within the environment where it might have been employed in the past thereby changing the natural geochemical composition of that particular environment. MATERIAL AND METHODS Geographic coordinates of the centers of the magnetic anomalous zones were read on the residual magnetic map and the locations along the respective traverses were re-occupied using Etrex Garmin GPS (Figure 1). Eight (8) soil samples were collected with 6 of the samples (A-F) taken from the magnetic anomalous zones while the remaining 2 samples (G &H) were collected from the non-anomalous magnetic zones and used as control (Table 1). The soil samples were collected at a depth of 20 cm and placed inside a sterilized plastic container. The samples were prepared into thick pellets of 13 mm diameter in a Spec-caps (Obiajunwa, 2001) without binder. A pellet of International Atomic Energy Agency (IAEA) Soil 7 Soil Standard was prepared. Both the soil samples and the standard were then irradiated for 1000 seconds with X-ray, using Energy Dispersive X-ray Fluorescence (EDXRF) spectrometer with a Ag anode. The equipment model is PX 2CR Power Supply and Amplifier for XR-100CR Si Detector, with facilities for spectral acquisition for qualitative and quantitative interpretation (Obiajunwa, 2001). Irradiation of samples was done in irradiation chamber and samples were irradiated for 1000 seconds under X-Ray tube operation condition of 25 Kv and 50 A. The Pacific Journal of Science and Technology –429– http://www.akamaiuniversity.us/PJST.htm Volume 13. Number 2. November 2012 (Fall) µ Qualitative interpretation of the sample spectra was carried out using PMCA Spectral acquisition software. The X-rays energy elements were detected on either the K-lines or the L-lines respectively (Figures 2 and 3). Quantitative interpretation was done with the aid of the XRS- FP analytical software under the Fundamental Parameter analytical method. RESULTS AND DISCUSSION Table 2 shows the results obtained from the analysis of standard (soil 7) ran with the samples as a measure of the accuracy of the experimental values and the corresponding certified values. Table 3 displays the analyzed values for the soil samples collected from the anomalous and nonanomalous magnetic closures. The results of the major heavy metals (Fe, Cu and Zn) within the sampled areas were used to generate a bar chart which shows the concentration of each metal along their respective traverses and stations as well as the concentrations in weight percentage (Wt%) (Figures 4-6).
891400 891350 891300 891250 891200 891150 891100 Traverse Line G D C E H TR 1 TR 2 632600 632650 632700 632750 632800 632850 Magnetic Anomalous Zone. Non Anomalous Magnetic Zone A B 0 50 100 150 200 TR 6 TR 5 TR 4 TR 3 Traverse (TR) Line Figure 1: Residual Magnetic Anomaly Map of Orile-Oje Archaeological Site Showing Marked Anomaly Magnetic Closures and Non Anomalous Control Site (Modified after Eluyemi et al., 2012) The Pacific Journal of Science and Technology –430– http://www.akamaiuniversity.us/PJST.htm Volume 13. Number 2. November 2012 (Fall) F N 200 180 160 140 120 100 80 60 40 20 0 -20 -40 -60 -80 -100 -120 -140 -160 -180 -200
Page 1: X-Ray Fluorescence (XRF) Characteri
Page 5 and 6: Count 100000 10000 1000 100 10 1 Ca
Page 7 and 8: Figure 5: Concentrations of Copper
Page 9: Geophysics) of the University of Bi

Abstract - Akamai University

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