Department of GeologyDepartment of Geology
POTENTIAL OCCUPATIONAL
RADIATION EXPOSURE DUE
TO NORM ARISING FROM
EXPLOITATION OF RARE-
METAL PEGMATITES OF
OLODE, IBADAN,
SOUTHWESTERN NIGERIA.
BY
FATAI OLABANJI BALOGUN
Nigeria
OUTLINE
• INTRODUCTION
• MINING GEOLOGY
• MINING IN NIGERIA
• RADIOACTIVITY IN MINING
• CASE STUDY
• METHODOLOGY
• RESULTS
• CONCLUSION
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INTRODUCTION
What are NORMS?• Norms are terms used to describe materials that contain radionuclides that are
present in the natural environment.
•Radiation of Natural origin consists of two components ( cosmic radiation and
terrestrial radiation). Examples of cosmic and terrestrial radionuclides are 14C, 7Be
and 238U and 40K respectively.
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INTRODUCTION contd’The Biological effects of radiation are;
• Deterministic effects: These effects have a definite threshold and do not manifest
until this threshold is reached. It usually manifests in form of radiation skin burning
and cataracts.
• Stochastic effects: These effects do not have a definite threshold. It usually
manifests in form of cellular changes (DNA mutation). Cancer is the only clinical
manifestation of radiation-induced stochastic effect
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MINING GEOLOGYWhat is a Mineral?• A mineral is a naturally occurring compound with definite chemical composition
Examples are;
Quartz - SiO2
Beryl - Be3Al2(SiO3)6
Magnetite - Fe3O4
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How are these minerals formed?• As magma cools, more abundant metals (silicon, aluminum) deposit first
•Solidification of magma releases water - a hydrothermal solution
•Minerals precipitate from hydrothermal solution and deposit in cracks or veins in
rock.
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MINING IN NIGERIA• Nigeria is blessed with up to 34 different mineral resources, which includes; Tin,
Columbite, Tantalite, kaolin, beryl, e.t.c
•Mining is generally administered through the ministry of solid minerals and
development.
•Illegal artisanal miners and private sector mining companies have made the most
significant discoveries of deposits of economic minerals in the country
• These bodies are usually driven by the prices these minerals command in the
market
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RADIOACTIVITY IN MINING • Norms are produced and can cause significant health hazard when they are
concentrated by anthropogenic activities such as mineral mining, oil and gas
production.
• The three major sources of natural radioactivity are K-40, the decay product in the
U-238 decay series and the decay products in the Th-232 decay series.
• Radioactivity in mining is of great concern because minerals such as Monazite,
Zircon and Xenotine, contain reasonable amounts Uranium and Thorium, which are
dangerous to the human health.
The decay series of 238U (Adapted from Lamarsh and Baratta, 2001)
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Isotope Half-life Radiation Gamma-ray
energy(MeV)
232Th 1.4 x 1010yrs α,γ 0.059
228Ra 6.7 yrs β,γ 0.03
228Ac 6.1 yrs α,γ 0.96—0.97
226Th 1.91 yrs α,γ 0.085—0.214
224Ra 3.64 days α,γ 0.24, 0.29
220Rn 51 s α,γ 0.54
216Po 0.16 s α -
212Pb 10.6 hrs β,γ 0.11—0.41
212Bi 60.0 min β,α,γ 0.04—0.22
212Po 0.3 x 10-6 s α -
208Tl 3.1 min β,γ 0.28—2.62
208Pb Stable
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Important Radiation Units
Measure ofAmount ofradioactive material Ionization in air
Absorbed energy per mass
Absorbed dose weighted by type of radiation
QuantityActivity
Exposure
Absorbed Dose
Dose Equivalent
UnitBecquerel
(Bq)
Roentgen (R)
gray(Gy)
sievert (Sv)
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CASE STUDY- Gbayo mines, Olode, Ibadan.
• Olode lies between latitudes N7º10ˈ and N7º13ˈ and longitudes E3º55ˈand E3º58ˈ
and it’s underlain by rocks of the Precambrian basement complex.
• The Gbayo mines were accidentally discovered by Femi Falegan in 1995.
• Beryl is the economic mineral being currently mined at the gbayo mines.
• Olode and its environs have some of the largest reserves of beryl in Nigeria.
• Tantalite mining have been reported to have taken in the early days of mining
activities at these mines.
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CASE STUDY- Gbayo mines, Olode, Ibadan.
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CASE STUDY- Gbayo mines, Olode, Ibadan.
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CASE STUDY- cont’d
1km
0
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NAUGEN_GNEISSBIOTITE GARNET_SCHIST
META_GABBRO
PEGMATITEQUARTZITE
FaultRiverRoad
LEGEND
596000
596000
598000
598000
600000
600000
602000
602000
604000
604000
606000
606000
608000
608000
788000 788000
790000 790000
792000 792000
794000 794000
796000 796000
0 1 2 KM
GEOLOGIC MAP OF A PORTION OF IBADAN SOUTHEAST
OLODE
# ###
#
#
#
#
#
OLODE
# SAMPLING POINT
GBAJE ASO
%
%
%
%
VILLAGE
3
(A D A P T E D F R O M I W O S H E E T 60)
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METHODOLOGY• A total of fifteen (15) samples were collected from three open pit mines in the
study area. 9 slurry soil, 3 water, 3 rock samples (including 2 gemstone-bearing
pegmatite rock).
• A control sample of dark topsoil was obtained at a distance of 2km from the mine
site.
• The slurry samples were dried for a period of 5 weeks
• Each sample was sieved using a 2mm sieve, and weighed into a plastic container
with an average weight of 40grams. Each sample weighed an average of 200grams.
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METHODOLOGY - cont’d• The gamma ray spectrometry analysis was carried out using a HPGe detector
• The energy calibration of the detector was done using 241Am, 22Na, 137Cs, 60Co in
which the gamma ray energies range between 59.6 keV and 1334 keV
• Each sample was counted for a period of 18000 seconds (5hours)
• The gamma spectra were carefully studied for radionuclide photo peaks
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HVPS MODEL
3106D
HPGe
Detector
Pre
Am
p
Am
plifier
ADC MCA
Electronic instrumentation of the gamma of the spectrometry system.
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RESULTSSample number
40K 238U(Bi) 232Th
S1 230.68± 12.85 8.23±4.07 8.22± 1.41
S2 195.20± 10.61 7.71±3.87 6.13± 1.57
PM1 2200.7± 92.04 ND 6.43± 1.24
BS 486.95± 14.05 9.71± 4.25 10.93±1.73
S3 158± 9.40 7.64± 3.84 9.43± 1.48
S4 140.98± 9.05 13.11± 5.81 6.09± 1.10
S5 206.31± 10.82 3.10± 1.85 6.14± 1.05
S6 214.21±11.92 4.24±2.79 6.30± 1.83
Activity in (Bq/kg)
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RESULTSample number
40K 238U(Bi) 232Th
S7 102.4± 7.12 5.74± 2.80 6.27± 1.09
S8 86.42± 6.67 4.85± 2.41 7.47± 1.19
PM3 227.2± 13.58 6.43± 4.67 11.01± 1.24
S9 195.22± 10.78 6.43± 3.13 7.48± 1.21
S10- Control 211.61± 12.81 3.00± 2.05 11.95± 1.97
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Sample number
40K 238U(Bi) 232Th
W1 0.044±0.003 0.032±0.001 0.066± 0.001
W2 0.046±0.003 0.034±0.001 0.095±0.001
W3 0.051± 0.005 0.037±0.002 0.082±0.001
Activity in (Bq/l)
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A bar chart showing activity concentration of the samples
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RESULTS - cont’d• The activity concentrations of 40K, 238U and 232Th have an average value of 296.2 ±
14.66 Bq/kg, 6.23 ± 3.16 Bq/kg and 8.04 ± 1.38 Bq/kg respectively.
• The Absorbed Dose (D) for all the samples ranges between 8.996 to 112.976
nGy/hr with an average of 22.944 nGy/hr. This value is 0.4times the world average
value of 60 nGy/yr by United Nations Security Council on the Effect of Atomic
Radiation (UNSCEAR, 2000).
• The Dose Equivalent ranges between 0.055 to 0.692 mSv/yr. These values are
well below the thresholds of 1 mSv/yr and 20 mSv/yr which has been set for the
general public and occupational exposure respectively, according to the
International commission for Radiation Protection (ICRP, 2000)
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Conclusion and Recommendation• From the results of the analysis, the health impact assessment of the study area
shows that it is safe to carry out and continue mining operations in the study area,
but prolonged exposure can lead to some health hazards.
• It is recommended that further detailed research works should be carried out on
other mines within the Ibadan-Oshogbo rare metal pegmatite fields.
• Geochemical mapping should also be carried out to detect dispersion haloes which
may lead to the discovery of more deposits of beryl.
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