The geology of Magaoni area is associated with the presence of heavy minerals [1]. Magaoni’s neighbours Maumba and Nguluku where ilmenite was discovered by Tiomin Resource Inc. in 1996, using drilling and chemical analysis [2]. Ilmenite mineral is known to be magnetically weak, but provides observable magnetic response [3]. In this study, ground magnetic survey method was carried out to map magnetic anomalies of established stations, associated with ilmenite bearing formations. The magnetic contour map plotted showed weak and shallow magnetic signatures spread throughout the study area. 2D Euler deconvolution solutions revealed presence of magnetised formations from near surface to a maximum depth of about 450 m at some points. The weak magnetic formations of near surface indicated presence of ilmenite. Energy dispersive X-ray spectroscopy was done on soil samples collected randomly from the study area to determine the percentage of iron and titanium oxides. The results showed elevated values of titanium dioxide, ranging from 1.5% to 13% which is way above the global average of about 0.7% [4]. The percentage of iron oxide was low, ranging from 1.5% to 4%, this being the reason for weak magnetisation of the study area.
Mineral potential of Kwale County has been previously studied using methods such as aeromagnetic survey, satellite imaging and Shuttle Radar Topography Mission. The studies revealed the presence of dune-like structure in the north-eastern part of the county and ferrous magnetic elements along the valley in between Kiruku and Mrima. The aeromagnetic data showed that the area is magnetically noisy on the eastern side, indicating shallow source anomalies. Ilmenite is known to be mineral sand that is weakly magnetic [
Magaoni is located about 50 km south of Mombasa, off Ukunda-Lunga road, the area lies within the coordinates 4˚22'S 39˚20'E and 4˚25'S 39˚20'E. The study area is 7 kilometres from where mining of ilmenite is being done (
Magaoni is found within the Magarini sand grit. The mineralisation of the area is made up of stratified Aeolian sands of the Magarini formation and consists mainly mineral sand deposited in dunes, as shown in
The series is divided into three broad lithological units with coarse sandstones and grits at the top and bottom of the succession, and a finer sandstones and shales in the middle. Igneous and pyroclastic are confined to Jombo Hill, an alkaline intrusion, and associated satellite vent agglomerates and dykes [
The ground magnetic study of Magaoni, covered an area of about 25 Km2, and consisted of 20 profiles spaced 250 m apart. A total of 800 magnetic intensity stations were measured with spacing of 100 m intervals along each line. Each profile had a total length of 4000 m and 40 magnetic intensity stations with a bearing normal to the regional structure. The magnetic intensity measurements were recorded using a Fluxgate magnetometer manufactured by Stefan Mayer Instruments. It measures the earth’s vertical magnetic intensity component. Stations were established using Garmin GPS receiver (Global Positioning System) device from Garmin International, to give their exact positions on the earth in terms of northing and easting coordinates. A Base Station was also established to monitor and remove diurnal variation [
The anomaly obtained was used to plot a magnetic contour map and profiles of the survey area using Surfer 11 as displayed in
The magnetic anomaly contour map shows that the whole area has weak and shallow magnetisation; this indicates that the area is covered by sedimentary deposits of magnetically weak minerals or materials [
The profiles were drawn to cut across the most anomalous sections of the study area. This was done to enable further analysis such as trend removal, vertical and horizontal derivatives and Euler deconvolution (
Qualitative interpretation of the magnetic field intensity shows higher magnetic values to the north-east direction running through to the south-west. The probable cause of this high magnetic signature could be due to the presence of iron ores which have high magnetic susceptibility. This is in agreement with the geologic description of the orientation of ferrous deposits in Kwale region. The probable location of ilmenite deposit is characterized by weak magnetic anomaly.
The deposits on the northern part of the region and that on the southern part lie on the relatively low magnetic intensity regions, that is, 530 nT and 550 nT respectively.
In the North-West and South-West orientation are regions of low magnetic intensities indicating the presence of ilmenite deposits with the same orientation. Thus, low magnetic intensities in the North-West and South-West orientation as evidenced in the anomaly maps are due to weak magnetic minerals.
Euler deconvolution is an imaging technique. It gives the vertical and horizontal distribution of the anomaly
along the profile. Euler deconvolution was done to the data of the five profiles.
Along profile AA’ (
There is a strong magnetic anomaly around (0 m - 100 m), (800 m - 1200 m) and (1500 m - 2400 m) which is an indication of highly magnetic materials near the surface, along profile BB’ (
In profile CC’ (
Euler solution for profile DD’ (
Euler solution for profile EE’ shows magnetisation at a depth of about 450 m from 0 m to 500 m along the profile (
In this study, Energy Dispersive X-ray Fluorescence Spectrometer was used to analyze for titanium and iron oxides. The equipment used is known as EDX machine.
Sample SS01 was obtained from the surface at station N9516376, E0551360; SS02 was obtained from a depth of 0.5 m at N9519776, E0551610 and SS03 from a depth of about 1 m at N9518276, E0553610. The samples were subjected to Energy Dispersive X-ray Fluorescence spectroscopy (EDX-F), to determine for iron and titanium oxides. The type of machine used was EDX800HS2 manufactured by Jiangsu Skyray Instrument Co., Ltd. All the samples showed elevated values of titanium dioxide, values exceeding the global average of about 0.7% [
Atmosphere: Air.
Analyte | Target | kV | uA | FI | Acq. (keV) | Anal. (keV) | Time (sec) | DT% |
---|---|---|---|---|---|---|---|---|
Ti ? U | Rh | 50 | 15-Auto | -------- | 0 - 40 | 0.0 - 40.0 | Live 50 | 24 |
Na ? Sc | Rh | 15 | 689-Auto | -------- | 0 - 20 | 0.0 - 4.4 | Live 49 | 25 |
Analyte | Result | Std. Dev. | Proc.-Calc. | Line | Int. (cps/uA) |
---|---|---|---|---|---|
SiO2 | 92.146% | 0.920 | Quan-FP | SiKα | 0.4307 |
TiO2 | 4.411% | 0.106 | Quan-FP | TiKα | 2.9330 |
Fe2O3 | 1.740% | 0.032 | Quan-FP | FeKα | 4.6302 |
SO3 | 1.255% | 0.077 | Quan-FP | S Kα | 0.0295 |
ZrO2 | 0.448% | 0.005 | Quan-FP | ZrKα | 13.4179 |
Analyte | Target | kV | uA | FI | Acq. (keV) | Anal. (keV) | Time (sec) | DT% |
---|---|---|---|---|---|---|---|---|
Ti ? U | Rh | 50 | 14-Auto | -------- | 0 - 40 | 0.0 - 40.0 | Live 49 | 26 |
Na ? Sc | Rh | 15 | 446-Auto | -------- | 0 - 20 | 0.0 - 4.4 | Live 50 | 26 |
Analyte | Result | Std. Dev. | Proc.-Calc. | Line | Int. (cps/uA) |
---|---|---|---|---|---|
SiO2 | 79.852% | 0.610 | Quan-FP | SiKα | 0.7875 |
TiO2 | 13.357% | 0.113 | Quan-FP | TiKα | 19.8165 |
Fe2O3 | 4.338% | 0.037 | Quan-FP | FeKα | 20.9211 |
ZrO2 | 1.712% | 0.008 | Quan-FP | ZrKα | 80.6791 |
SO3 | 0.648% | 0.045 | Quan-FP | S Kα | 0.0354 |
MoO3 | 0.093% | 0.004 | Quan-FP | MoKα | 4.3596 |
Analyte | Target | kV | uA | FI | Acq. (keV) | Anal. (keV) | Time (sec) | DT% |
---|---|---|---|---|---|---|---|---|
Ti ? U | Rh | 50 | 15-Auto | -------- | 0 - 40 | 0.0 - 40.0 | Live 50 | 24 |
Na ? Sc | Rh | 15 | 506-Auto | -------- | 0 - 20 | 0.0 - 4.4 | Live 50 | 24 |
Analyte | Result | Std. Dev. | Proc.-Calc. | Line | Int. (cps/uA) |
---|---|---|---|---|---|
SiO2 | 82.871% | 0.582 | Quan-FP | SiKα | 0.8236 |
Al2O3 | 10.247% | 0.575 | Quan-FP | AlKα | 0.0234 |
TiO2 | 2.8985% | 0.054 | Quan-FP | TiKα | 4.7155 |
Fe2O3 | 2.151% | 0.022 | Quan-FP | FeKα | 14.3774 |
SO3 | 1.253% | 0.047 | Quan-FP | S Kα | 0.0713 |
ZrO2 | 0.329% | 0.003 | Quan-FP | ZrKα | 24.3511 |
MnO | 0.186% | 0.010 | Quan-FP | MnKα | 1.0144 |
V2O5 | 0.065% | 0.023 | Quan-FP | V Kα | 0.1462 |
Core, Section interval (cm) | Depth (mbsl) | SiO2 | TiO2 | Al2O3 | Fe2O3 | MnO | MgO | CaO | Na2O |
---|---|---|---|---|---|---|---|---|---|
115-706C-4R-3, 10-13 | 66.70 | 48.04 | 3.17 | 13.67 | 15.65 | 0.20 | 5.65 | 10.35 | 2.61 |
115-707C-25R-1, 39-43 | 404.90 | 49.60 | 1.38 | 14.90 | 13.49 | 0.16 | 7.10 | 11.99 | 2.15 |
115-707C-25R-3, 44-47 | 407.80 | 49.70 | 1.45 | 15.10 | 13.32 | 0.17 | 7.15 | 11.24 | 2.23 |
115-713A-15R-4, 7-13 | 131.90 | 49.36 | 1.31 | 14.13 | 13.27 | 0.19 | 8.58 | 11.32 | 2.18 |
115-713A-15R-41, 43-146 | 132.63 | 49.07 | 1.52 | 13.58 | 14.71 | 0.25 | 5.64 | 12.11 | 2.29 |
115-715A-25-6, 38-42 | 237.00 | 47.93 | 0.98 | 14.98 | 11.82 | 0.18 | 10.97 | 11.64 | 1.58 |
Collimator: 10 mm.
Spin: Off.
Atmosphere: Air.
Collimator: 10 mm.
Spin: Off.
Atmosphere: Air.
Collimator: 10 mm.
Spin: Off.
Results in
The Euler solutions and quantitative results of the spectroscopic analysis of soil samples revealed that Magaoni area as a whole is generally characterized by weak magnetic anomaly, presence of titanium oxides in large quantities and low values of iron oxides. The average depth for the near surface magnetic anomaly is 40 m, while that of the deepest is about 500 m. The magnetic signatures are more pronounced in the North-East and South-East of Magaoni. All data give clear indication of the presence of mineral sand containing iron and titanium oxides, which could simply be ilmenite.
Much thanks to the entire physics department of Kenyatta University and Donata Nanyukia for the great support during research and writing of this paper.
George OduorOtieno,John GitongaGithiri,Willis JakanyangoAmbusso, (2016) Integration of Ground Magnetics and Energy Dispersive X-Ray Fluorescence Spectroscopy in Ilmenite Prospection in Magaoni, Kenya. Open Journal of Applied Sciences,06,79-88. doi: 10.4236/ojapps.2016.62008