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

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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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