keywords: petrographic, pegmatite, metasomatic, quartz

International Journal of Basic & Applied Sciences IJBAS-IJENS Vol: 11 No: 04 57

118404-7676 IJBAS-IJENS © August 2011 IJENS I J E N S

Petrographic and Geochemical Evaluations of Rare –

Metal (Ta-Nb) Potentials of Precambrian Pegmatities

of AWO Area Southwestern, Nigeria.

1Akintola, A. I.,

1 Omosanya, K. O.,

1Ajibade O. M.,

2Okunlola, O. A &

1 Kehinde-Philips, O. O

1, Department of Earth Sciences, Olabisi Onabanjo University, Ago-Iwoye, Nigeria.

2 Department of Geology, University of Ibadan, Ibadan, Nigeria.

E-Mail: [email protected]

Abstract-- The Petrographic and geochemical evaluations of

pegmatite bodies around Awo in Southwestern Nigeria were

carried out with a view to characterising them and determining

their genesis and rare metal potentials that may be related to Ta-

Nb mineralization.

Fifteen (15) whole rock pegmatite samples and five (5) muscovite

samples extracted from the pegmatites were analyzed for major

and trace elements using the Inductively Coupled Plasma

Emission Spectrometer (ICP-AES) analytical method.

The petrography revealed preponderance of Microcline and

albite with subordinate muscovite and anhedral quartz,

accessory minerals found include tourmaline, garnet, beryl, and

spodumene.

The whole rock pegmatites are highly siliceous having SiO2 mean

value to be (54.95%) while the muscovite extract has a mean

value of (44.61%); Al2O3 contents are fairly high in the muscovite

extracts than in the whole rock pegmatite samples with very low

mean values of MnO, MgO, CaO, Na2O, TiO2, and P2O5. Other

than these, the pegmatites are enriched in Rb, Cs, Zr, Ga, Ba, Be,

Y, W, and the rare metals Ta and Nb.

The variation diagram plot of Na2O/Al2O3 versus K2O/Al2O3

reveals igneous ancestry for the pegmatites with the Rb/Sr plot

suggesting a 30km crustal thickness during emplacement of this

pegmatite. There is low to moderately high albitisation,

progressive rare alkali fractionation, and controlled Ta-Nb

enrichment in the Awo fields with the sample plotting in the Rare

Metal Pegmatite Zone “RMP”. The recorded negative Ce

anomaly is an indication of oxidation due to the influence of fluid

– rock metasomatic processes in their genesis.

The enrichment pattern revealed by other geochemical variation

plots shows that the pegmatites have moderate to high Ta-Nb

mineralization.

Index Term-- Petrographic, Pegmatite, Metasomatic, Quartz,

Muscovite, Feldspars.

I. INTRODUCTION

The study area lies within longitude 4o 23

1 E

to 4

o 25

1 E

and

latitude 7o 45

1N to 7

o 47

1 N of Iwo Sheet 242 N.E. (Fig. 1). It

is accessible by complex road network of major and minor

roads as well as foot path linking one sampling point to the

other. In recent times there has been renewed interest in the

study of pegmatites globally because of its attractive

economic potentials. Earlier study of Pegmatites in Nigeria

include the work of Jacobs and Webb (1946) which identified

that the pegmatites are restricted within a confine of 400km

NE-SE trending belt. This point of view was refuted by the

work of Garba, (2003) and Okunlola, (2005). The occurrences

in the Southeastern part of the Nigeria, notably around Obudu

hills were presumed to extend into Northeast Brazil (Garba,

2003; Ekwueme, 2004). The Nigerian pegmatites evolved

during the time span of 600+530Ma, (Matheis and Caen

Vachete, 1983), which indicates formation (Orogeny) during

the periods of Pan African magmatism.

Precambrian pegmatites of Nigeria are known to host a variety

of rare metals, tantalum, niobium, tin, tungsten, columbite as

well as lithium which found use in the production of

microchips and microprocessors for computers and

electronics, aircraft construction, casting, galvanizing,

production of containers, metal wears. More importantly, the

tantalum and niobium contained in this specialty metals are

used for heat and corrosion resistant steels and alloys applied

in space ships and gas turbines. (Okunlola,1998., Adekoya et

al., 2003., Garba, 2003., Okunlola and Ogedengbe, 2003.,

Akintola, 2004., Okunlola, 2005., Okunlola and Jimba, 2006.,

Okunlola and Somorin, 2005., Okunlola and Akintola, 2007.,

Okunlola and Akintola, 2008 ).

Matheis, 1981, Matheis et al., 1982., Kuster, 1990., Garba,

2003, Okunlola, 2005 classified the metallogeny of the rare

metal Ta-Nb pegmatites of Nigeria, outlining 7 broad fields

namely Kabba - Isanlu, ljero - Aramoko, Keffi- Nasarrawa,

Lema -Ndeji, Oke Ogun, Ibadan -Osogbo and Kushaka -

B/Gwari. The Awo Pegmatites occurrence which is part of the

Precambrian pegmatites in Ibadan-Osogbo field was studied

with the aim of elucidating their petrography and geochemical

features and thus characterizing them, and understanding their

genesis and rare metal potentials.

II. GEOLOGICAL SETTING, FIELD DESCRIPTION

AND PETROGRAPHY OF ROCKS

mailto:[email protected]



Nigeria is underlain by Precambrian basement complex rocks,

younger granites of Jurassic age and Cretaceous to Recent

sediments. The basement rocks occupy about half of the land

mass of the country, and is a part of the Pan-African mobile

belt lying between the West African and Congo cratons

(Black,1980). There are however contrasting documentation

of the evolution of the basement rocks. However loosely, the

basement is grouped into three major groups

lithostratigraphically viz: the Migmatite- Gneiss Quartzite

Complex: comprising biotite and biotite hornblende gneisses,

quartzites and quartz schist. Schist Belts, comprising

paraschists and meta igneous rocks, which include schists,

amphibolites, amphibole schists, talcose rocks, epidote rocks,

marble and calc-silicate rocks. They are mainly N-S to NNE-

SSW trending belts of low grade supracrustal (and minor

volcanic) assemblages. Other secondary rocks used in

delineating them are carbonates, calc gneiss and banded iron

formation (BIF) and Older granites, which include granite,

granodiorite, diorite charnockite, pegmatites and aplites.

The Awo study area is generally underlain by granite, banded

gneiss, quartzite and quartz schist, with pegmatite trending in

the NNW-SSE direction occurring as near vertical intrusions

into the older rocks. (Fig. 2)

The granite occurs mostly in the northwestern portion of the

map, the granites which are often coarse grained to porphyritic

in texture are mainly composed of biotite, microcline and

quartz.

The banded gneiss occurs as a massive rock consisting of

alternating bands of felsic minerals notably plagioclase

feldspars and quartz, and the dark bands consisting of biotite

and hornblende.

The quartzite samples are mostly white in color but some

ferruginized varieties display reddish bands. They consist

mainly of quartz which occurs as irregular fine to medium

grained crystals with interlocking grains of muscovite.

Fig. 1. The location map of Awo with the sampling points

The quartz schist occurs as low-lying outcrops, they are fine

to medium – grained, display incipient schistocity and contain

quartz, microcline, and muscovite with accessory haematite.

The pegmatites of Awo occur as near vertical intrusions

covering the study area, they are coarse grained rock with a



general milky white appearance. The main mineral

assemblages are microcline, quarzt, biotite, and tourmaline

(black and green) while the secondary associated minerals

include kaolinite, tantalocolumbite and cassiterite.

Petrographical studies of the Awo pegmatite show that they

contain mainly plagioclase, muscovite, quartz, microcline,

biotite, and accessory opaque minerals such as garnet,

tourmaline, cassiterite and tantalocolumbite (Table I).

Plagioclase ranges from (15 - 60 %), it exhibits characteristic

albite twinning and it is well distributed in all the samples.

Muscovite occurs as tiny elongated plates with high relief and

perfect cleavage in one direction with strong birefringence, it

ranges between (5-20%)

Quartz ranges between (25-35%), it occurs as cloudy anhedral

grains with wavy extinction and characteristic weak

birefringence.

Microcline often intergrown graphically, they are sometimes

perthitic with albite occurring as patchy perthite. It however

displays characteristic cross hatch twinning it ranges between

(1-50%).

Biotite ranges from (1-5%), it however occurs as fine dark

brown platy grains. Figures:3a(i.),b(i),c(i),d(i)

&3a(ii),b(ii),c(ii),d(ii)

Fig. 2. Geological map of Awo area southwestern Nigeria.

III. METHODS

Systematic geological mapping followed by thin sectioning of

fresh whole rock samples was carried out. The whole rock and

muscovite extracts of the pegmatite samples were then

analyzed for major, minor, trace, and rare earth elements using

inductively-coupled plasma atomic emission

spectrophotometry (ICP-AES), at Activation Laboratories ltd.

(ACTLAB) Ancaster, Ontario Canada.

The geochemical analytical procedure involves addition of

5ml of Perchloric acid (HClO4), Trioxonitrate (V) HN03 and

15ml Hydrofluoric acid (Hf) to 0.5gm of sample.

The solution was stirred properly and allowed to evaporate to

dryness after it was warmed at a low temperature for some

hours. 4ml hydrochloric acid (HCl) was then added to the

cooled solution and warmed to dissolve the salts. The solution

was cooled; and then diluted to 50ml with distilled water. The

solution is then introduced into the ICP torch as aqueous -

GG

G

G

Bgn

Bgn

Bgn

Bgn

Bgn

Q

Q

Q



aerosol. The emitted light by the ions in the ICP was

converted to an electrical signal by a photo multiplier in the

spectrometer, the intensity of the electrical signal produced by

emitted light from the ions were compared to a standard (a

previously measured intensity of a known concentration of the

elements) and the concentration then computed.

Table I

Average modal composition (%) of minerals in Awo pegmatites

Minerals P1 (%) P2 (%) P3 (%) P4 (%)

Plagioclase (PL) 45 15 50 60

Muscovite (Mu) 5 5 20 - Quartz (Q) 35 25 25 30 Biotite (B) 5 - - -

Garnet (G) 5 - - - Microcline (M) - 50 - - Accessories (A) 5 5 5 10

PI-P4 Represent Photomicrographs of Pegmatites from Awo study area

IV. RESULTS AND DISCUSSION

The geochemical data of major and trace element analysis

which are presented in (Table II) show that the Awo pegmatite

have SiO2 values ranges from 44.79-70.37% with a mean

value of 54.95% in the Awo whole rock pegmatite, while it

ranges from 44.27-44.89% with a mean value of 44.61% in

the muscovite extracts. The SiO2 values of the Awo whole

rock and muscovite extracts compares with the values of rare

metal Ta-Nb mineralized pegmatites across Nigeria

(Okunlola, 2005; Okunlola and Akintola, 2007; Akintola and

Adekeye, 2008). Al2O3 ranges from 14.70-33.51% with an

average of 25.77% in the Awo whole rock samples, while it

ranges from 33.20 to 34.20% with a mean value of 33.83% in

the muscovite extracts. There is a sharp contrast in the values

of some of the whole rock and muscovite extracts sample of

the alumina content in addition with other rare metal

characteristics for the pegmatites of this study area which

simply confirms the complexity of the Awo pegmatites. Fe2O3

ranges from 0.25-7.22% with an average of 2.44% in the

whole rock pegmatite, while the muscovite extract gives a

range of 4.36-4.52% with an average value of 4.46%. Mean

contents of major oxides MnO (1.61%, 0.12%), MgO (0.06%,

0.36%), CaO (0.30%, 0.01%), Na2O (1.28%, 0.58%), K2O

(3.74%, 10.05%),TiO2 ( 0.06%, 0.07%), P2O5 (0.14%, 0.03%),

for the whole rock and muscovite extract samples of Awo

pegmatites respectively, compare favourably with the rare

metal bearing pegmatites of Lema-Ndeji, Igbeti and Isanlu-

Egbe areas (Okunlola, 2005 ; Okunlola and Akintola, 2008 ;

Okunlola and Oyedokun, 2009).



Fig. 3a(i). Photomicrograph of Pegmatite in transmitted light showing Plagioclase (PL),Biotite (B), Muscovite (MU), Quartz (Q) and Garnet (G). b(i):

Photomicrograph of Pegmatite in transmitted light showing Microcline (M), Plagioclase (PL) Muscovite (MU) and Quartz (Q). c(i): Photomicrograph of Pegmatite in transmitted light showing Plagioclase (PL), Quartz (Q) and Muscovite (MU). d(i): Photomicrograph of Pegmatite in transmitted light showing

Plagioclase (PL) and Quartz (Q).a(ii), b(ii), c(ii) and d(ii)Modal distributions of estimated minerals in Awo pegmatites.



Fig. 4(a). Plot of K/Rb vs Cs for Awo Pegmatite (After Cerny, 1982);( b) K/Rb vs Rb distribution pattern in the Muscovite extracts of Awo Pegmatites; Arrow

indicate normal differentiation trend after Staurov et al., (1969); (c) K/Rb vs Rb distribution pattern in the whole rock Pegmatites of Awo study; Area, arrow

indicate normal differentiation trend after Staurov et al., (1969);(d) Plot of Na2O/Al2O3 vs K2O/Al2O3 (Wt%) showing variation diagram for the Field Of Igneous

and Meta sedimentary rocks of Awo Pegmatites. (After Garrels and Mackenzie, 1971); (e) Plot of Ta vs Cs for the pegmatites of Awo study area; (After Moller and Morteani, 1987); (f) Plot of Ta vs Rb for the pegmatites of Awo study area; (After Moller and Morteani, 1987); (g) Plot of Ta vs Cs+Rb for the pegmatites

of Awo study area. (After Gaupp et al., 1984);(h) Plot of Ta vs Nb for the pegmatites of Awo study area.(i.) Plot of Ta vs K/Cs ratio for the pegmatites of Awo

study area. (After Gordiyenko, 1971 and Beus, 1966 ). (j): Plot of Ta/W ratio vs. Cs for the pegmatites of Awo study area.The Ta/W ratio increases with increasing elements fractionation as indicated by Cs. (After Moller and Morteani, 1987);(k): Rb vs (Y+Nb) discriminant diagram for the whole rock sample

pegmatites of Awo=AO compared to those of Olode = OD, Komu= IK, and Ago-Iwoye AOI (After Pearce et al., 1984). VAG- VOLCANIC ARC GRANITE;

ORG- OCEANIC RIDGE GRANITE; WPG- WITHIN-PLATE GRANITE; SCG- SYN-COLLISIONAL GRANITE ;(l): Zr-Sio2 Plots of the pegmatites of Awo= AO compared to those of Olode=OD, Komu=Ik, and Ago-Iwoye =AOI pegmatites; (m): Sr-Rb Plots of the Awo =AO compared to those of Olode=OD,

Komu=Ik,and Ago-Iwoye =AOI pegmatites.(n): Plot of Rb-Sr for the pegmatites of Awo study area. (After Condie, 1976). (o) Plot of Ta/(Ta+Nb) vs Mn/(Mn+Fe) variation plots of the Awo Pegmatites



Trace and rare earth element data (Table III) show that the

pegmatites are enriched in rare metals with moderately high

values of Cs, Nb, Sn, Rb, and Ta. With Cesium ranging from

(2.5-526ppm; 160.2-210.8ppm), Niobium (4-390ppm; 370.5-

383.1ppm), Tin (2-244ppm; 1050-1104ppm), Rubidium (58.0-

1000ppm; 2936-3136ppm) and Tantalum (1.0-365ppm; 35.3-

41.9ppm), for the whole rock and muscovite extracts samples

of Awo pegmatites respectively. The Ta and Nb values in the

whole rock and mica extracts in the same vein with the Komu

pegmatites are comparable with those of the richer Nasarawa-

Keffi and Kushaka Ta-Nb fields of Nigeria respectively

(Okunlola, 2005). The mean values of Be (34.2ppm,

24.80ppm), Ga (54.52ppm, 257.32ppm), W (4.79ppm,

9.18ppm), Sr (45.93ppm, 0.58ppm), Zr (49.04ppm, 7.36ppm),

Ba (79.67ppm, 1.4ppm) and Y (5.16ppm, 0.2ppm) are as

shown for the Awo whole rock and muscovite extract

pegmatite samples respectively. These values compare

favourably with the mineralized pegmatites of Noumas South

Africa, Silver leaf, Canada and Homestead Canada. (Moller

and Morteani, 1987). However the level of mineralization in

Awo pegmatites is lower than that of the highly mineralized

Tanco Ta-Nb (Cerny, 1982; Moller and Morteani, 1987).

Average elemental ratio Rb/Sr is expectedly high compared

with most of the other rare metal pegmatites Of Nigeria.

However, average K/Rb values are low and this value suggest

and indicate late stage progressive fractionational

crystallisation and probable mineralization (Kuster, 1990).

Ratios of K/Cs, K/Ba, and Th/U are also low, typical of rare

metal mineralization (Garba, 2003). Following after the

classification criteria of pegmatites based on bulk chemistry

signatures (Cerny, 1991a; 1991b), and the Ta/ (Ta+Nb) versus

Mn/ (Mn+Fe) plot (Fig. 4(o.)). The Awo pegmatites are of the

rare element class, complex pegmatite. They are of the LCT

petrogenetic family (Li, Rb, Cs, Be, Ga, Sn, Ta < > N (BPF)

and of the Beryl sub type. The pegmatites are of per

aluminous bulk composition {A/CNK>1} (where A: Al2O3,

CNK: CaO+ Na2O+K2O). Cerny, (1992) has observed that the

LCT family has a mild to extremely Per aluminous parent

granitic composition. Using the K/Rb versus Cs plots, the

pegmatites in Awo area are also rare metal bearing because all

the samples plot in the field of rare metal pegmatite “RMP”.

(Fig.4a).

The low values of Mg, Ti, Ba and Zr with attendant high Rb,

and Cs composition indicate high fractionation of the

pegmatites, while the moderately high Cs values of the Awo

pegmatites indicate moderately high alkali metal fractionation.

(Cerny, 1982a; 1982b; 1989). There is a clear enrichment of

Nb, Ta, Rb, Sn, Cs, Rb and depletion of Sc, Co which also

suggest mineralization of the rare metal columbo-tantalite

(Moller and Morteani, 1987). The samples are also relatively

higher In Ta content in the whole rock samples than in the

mica extracts showing that the pegmatites in Awo area are

adequately enriched in Tantalite.

The Ta-Nb mineralization potential trend as shown from plots

of K/Rb versus Cs (Fig.4a), and K/Rb versus Rb (Fig4(b) &

(c)) revealed a consistent trend as all the samples plot in the

mineralized field which is similar to those of Noumas deposits

in South Africa (Moller and Morteani, 1987). Some samples

also plot close to those of the highly evolved Tanco

pegmatites (Cerny, 1989).

The degree of albitization is revealed by the Triangular Ti-Sn-

(Nb+Ta) discriminant plot in the zone of albitization (Fig. 5)

for the Awo pegmatites. This plot also reveals a high degree

of albitization and it indicates a significant difference between

the mineralized and unmineralized pegmatite samples

(Matheis and Emofurieta, 1990; Okunlola and King, 2003;

Okunlola and Somorin, 2005; De Kun, 1965; Jacobson and

Webb, 1946). However these values are still low when

compared to those of the economically viable bodies like

Tanco Canada (Moller and Morteani, 1987), but they compare

favourably with those of other richer mineralized pegmatite

areas like Lema-Ndeji Central Nigeria, Egbe and Igbeti areas

southwestern Nigeria (Okunlola and Akintola, 2008; Matheis,

1987; Okunlola and Oyedokun, 2009). This is also indicative

of the degree of fractionation. In addition, the variation plots

of Ta versus Cs (Fig.4(e)), Ta versus Rb (Fig.4(f)), Ta versus

Cs + Rb (Fig.(g)), Ta versus Nb (Fig.4(h)), Ta versus K/Cs

(Fig.4(i)) and Ta/W versus Cs (Fig.4(j)) confirm their rare

metal mineralization potentials. These plots also show the

Awo pegmatite samples occurring over the mineralized lines

of Beus, (1966) and Gordiyenko, (1971).

The variation diagram plot (Fig.4(d.)) of Na2O/Al2O3 versus

K2O/Al2O3 reveals the igneous ancestry of the pegmatite

which plot in the granite-igneous field of Garrells and

Mackenzie, thus indicating and suggesting a granitic-igneous

ancestry for the Awo pegmatites. Samples also plot in the field

of volcanic arc granites on the Rb versus Y+Nb diagram

(Fig.4(k)), while crustal thickness during emplacement of

these pegmatite bodies (Fig.4(n)) reached about 30km as

shown from the Rb/Sr plot of Condie, (1976).

The plots of Zr/SiO2 (Fig.4(l)) and Sr/Rb plots (Fig.4(m)),

reveals their mixed ancestry with some samples plotting

completely out of the magmatic “M” field, in the after

magmatic field “AM” hence suggesting Awo pegmatites to be

a mixed basement plus supracrustal protoliths having

homogenous chemistry.

In the pegmatites of this study area; Rare earth elements

(REE) abundance as presented in (Table III) reveals the

chondrite normalized plot (Fig.6) which shows high light

(REE) LREE (La, Ce, Pr) values and lower heavy (REE)

HREE (Er, Lu, Yb) values. There is a negative Europium (Eu)

anomaly which according to Taylor et al., (1986) suggests

fractionation and indicates a late metasomatic effect. The

weak negative Ce anomaly observed in Awo pegmatites may

also suggest their rare metal mineralization. However, Taylor

et al., (1986) had suggested earlier that where there is a weak

negative Ce anomaly and a negative Eu anomaly as in this

case of Awo pegmatite samples it is an evidence of

considerable fractionation and metasomatism. Similarly,



Piper, (1974) and Garba, (2003) believe that Negative Ce

anomaly of rare metal pegmatite is taken to indicate oxidizing

condition during mineralization and interaction between, melt

fluids and host rocks sometimes over long distance.

Fig. 5. Triangular Ti-Sn-(Nb+Ta) Plot for Awo Pegmatite’s (After Kuster, 1990)

REE Chondrite normalized plots

Fig. 6. Chondrite normalized plots of Awo Pegmatite.



V. CONCLUSION

Results of this study show that the Precambrian pegmatites of

Awo which intruded the granite, banded gneiss, quartzite and

quartz schist, are rare-metal pegmatites. Average length of

each body is about 650m with variable width but usually not

less than 7 m. They are usually complex albitized pegmatites.

Microcline and albite are the dominant feldspars with

subordinate muscovites and quartz. Following after the

classification criteria of pegmatites based on bulk chemistry

signatures (Cerny, 1991a; 1991b), and Ta/ (Ta+Nb) versus

Mn/ (Mn+Fe) plot for the Awo whole rocks and muscovite

extracts pegmatites respectively, the Awo pegmatites are of

the rare element class, complex pegmatite type. They are of

the LCT petrogenetic family (Rb, Cs, Be, Li, Ga, Sn, Ta < > N

(BPF) and of the Beryl sub type. The pegmatites are of per

aluminous bulk composition {A/CNK>1} (where A: Al2O3,

CNK: CaO+ Na2O+K2O). Cerny (1992) has observed that this

LCT family has a mild, to extremely Peraluminous parent

granitic composition.

This field is clearly enriched in Ta-Nb rare – metal

mineralization. The lower K/Rb ratio, lower K/Cs, K/Ba,

Th/U ratios and higher Rb/Sr ratio for the Awo Ta-Nb rare-

metal pegmatites suggest that these pegmatites have benefited

from fluids that have been derived from late but highly

differentiation processes suggesting probable mineralization.

The rare-metal content Ta, Nb is moderately high when

compared with other mineralized pegmatites of Nigeria.

K/Rb versus Rb and plots of Ta versus Cs, Ta versus Rb also

confirm the moderate-high level of Ta-Nb mineralization

potentials comparable with other pegmatites across the world

such as those of Noumas (South Africa), Silver Leaf and Odd

West (Canada).

Acknowledgement

The authors acknowledged Dr Oshin O.O, Mr R.O Egbeyemi,

Mr Oyebolu Olalekan of Earth Sciences Department Olabisi

Onabanjo University Ago-Iwoye, Ogun State, Nigeria for their

considerable support. Mrs Akintola Omolara Olufunke was

exceptionally supportive.

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element distribution in Tin Bearing pegmatites of Southwestern

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[27] Moller, P and Morteani, G. (1987). Geochemical exploration guide

for Tantalum pegmatites. Economic Geology, Vol.42, pp. 1885-1897.



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RMZ- Materials And Geoenvironment, Vol.56, No.1, pp. 38-53. [29] Okunlola, O.A. (1998). Specialty metal potentials of Nigeria:

Proceedings of 1st Mining in Nigeria Conference. Fed. Ministry of

Solid Minerals, Abuja. Nigeria. pp. 67-72. [30] Okunlola, O.A. (2005). Metallogeny of Tantalite-Niobium

Mineralization of Precambrian Pegmatites of Nigeria. Mineral

Wealth; 104/2005, pp. 38-50. [31] Okunlola, O.A. and Akintola, A.I. (2007). Geochemical features

and rare metal Ta-Nb potentials Of Precambrian pegmatites of

Sepeteri area, southwestern Nigeria. [32] Okunlola, O.A. and Akintola, A.I. (2008). Compositional features

and rare metal (Ta-Nb) Potentials of Precambrian pegmatites of

Lema-Ndeji area central Nigeria. Mineral Wealth 149/2008, pp. 43-53.

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[34] Okunlola, O.A. and King, P.A. (2003). Process test work for the recovery of Tantalite-Columbite Concentrates from rare metal

pegmatites of Nasarawa area, central Nigeria. Global Jour.

Geological Sci, 1 (1) pp. 85-103 [35] Okunlola, O.A. and Ogedengbe, O. (2003). Investment potentials

of gemstone occurrences in Southwestern Nigeria In: Elueze, A.A

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[36] Okunlola, O.A. and Somorin, E.B. (2005). Compositional features

of Precambrian pegmatites of Itakpe area, central Nigeria. Global Journal Of Geological Sciences Vol.4 (2), pp. 221-230.

[37] Pearce, J.A. Harris, N.B.W. and Tindle, A.G. (1984). Trace

element discriminant diagrams for the tectonic interpretation of granitic rocks. Jour.Petrol. Vol.25, pp. 956-983

[38] Piper, D.Z. (1974). Rare earth elements in sedimentary cycle: A

summary. Chem.Geol. Vol.14 pp. 285-304. [39] Staurove, O.D., Stolyarov, L.S. and Isochewa, E.I. (1969).

Geochemistry and Origin of Verkh Iset Granitoid massif in central

Ural. Geochem. Intern. Vol.6, pp. 1138-1146. [40] Taylor, S.R., Rudnick, R.L., Mc Lennan, S.C and Eriksson, K.A.

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ABOUT THE AUTHORS

Akintola, A.I., MSc Mineral Exploration with option in Economic and Mining Geology (Ibadan) and BSc Geology (Ogun). He is a Lecturer in the

Department of Earth Sciences Olabisi Onabanjo University. His research

interests include Mineral exploration and environmental geology. He is a specialist in the study of granitic intrusions especially pegmatites.

Omosanya, K.O., MSc Structural Geology with Geophysics (Leeds), BSc Geology (Ogun). He is a Lecturer in the Department of Earth Sciences Olabisi

Onabanjo University. His research interests include Basin analysis, Seismic

interpretation, Structural geology and Environmental Geophysics.

Ajibade, O.M., M.sc. Applied Geochemistry (Ibada), B.Tech Applied

Geology (FUTA). He is a Lecturer in the Department of Earth Sciences Olabisi Onabanjo University. His research interest covers Petrology and

Environmental Geochemistry.

Okunlola,O.A., B.Sc (Ilorin), M.Sc (Zaria), PhD, (Ibadan). A senior lecturer

with the Department of Geology University of Ibadan. His research interest

covers mineral exploration and environmental Geology. He is a specialist in the study of petrology, Geochemistry and granitic intrusions especially

pegmatites.

Kehinde-Phillips, O.O., B.Sc (Ibadan), M.Sc (Laurentian Canada), Ph.D (Ibadan). A Professor of Economic Geology and Environmental

Geochemistry. Presently the Head of Department of Earth Sciences Olabisi

Onabanjo University.



Appendix Table II

Major element oxide composition of Awo Pegmatites (Wt %).

Oxides 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

SiO2 49.73 54 51.5 49.64 46.76 49.9 52.38 45.32 44.79 53.53 60.69 59.53 67.64 68.46 70.37 44.27 44.89 44.42 44.89 44.6

Al2O3 32.19 29.14 28.94 31.67 32.88 28.56 29.5 33.15 33.51 28.96 16.1 16.46 15.89 14.91 14.7 34.2 33.2 34.1 34.08 33.56

Fe2O3 1.24 0.57 1.58 0.88 1.32 2.23 1.32 2.73 2.69 0.25 7.22 6.17 2.43 3.94 2.1 4.42 4.51 4.36 4.48 4.52

MnO 0.026 0.024 0.03 0.042 0.032 0.041 0.025 0.05 0.052 0.008 8.41 7.67 2.44 3.87 1.44 0.12 0.12 0.1 0.12 0.12

MgO 0.09 0.03 0.06 0.04 0.07 0.1 0.06 0.08 0.08 0.14 0.02 <0.01 <0.01 0.06 0.05 0.32 0.37 0.44 0.32 0.36

CaO 0.06 0.03 0.05 0.04 0.05 0.05 0.05 0.09 0.09 0.4 1.74 0.23 0.48 0.63 0.47 <0.01 <0.01 <0.01 <0.01 <0.01

Na2O 0.11 0.25 0.11 0.19 0.1 0.09 0.12 0.16 0.19 0.3 2.93 2.01 4.02 4.82 3.76 0.57 0.58 0.57 0.58 0.58

K2O 1.47 6.05 1.55 4.46 1.89 1.5 2.15 3.18 3.24 5.82 2.05 6.95 6.52 2.96 6.34 9.85 10.17 10.02 10.05 10.18

TiO2 0.062 0.027 0.089 0.035 0.079 0.072 0.08 0.199 0.194 0.017 0.04 0.02 <0.01 0.02 0.01 0.07 0.07 0.07 0.06 0.07

P2O5 0.05 0.11 0.05 0.08 0.05 0.05 0.07 0.06 0.06 0.016 0.34 0.41 0.31 0.19 0.27 0.02 0.03 0.03 0.03 0.03

LOI 14.05 9.7 15.55 12.3 15.9 17.29 14.51 13.69 14.51 10.48 0.3 0.5 0.2 0.1 0.4 6 5.9 5.8 5.3 5.9

Total 99.07 99.94 99.51 99.38 99.13 99.89 100.3 98.72 99.38 100.1 99.87 99.96 99.96 99.97 99.95 99.88 99.89 99.9 99.88 99.89

The numbers 1, 2, 3,….20 represent sample numbers.

1-15: Whole rock Pegmatite samples from Awo

16-20: Muscovite extracts from Awo Pegmatites.



Table III

Trace and Rare earth element data of Awo Pegmatites (ppm).

Elements 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Ta 42.4 113 113 308 96.2 365 101 80.6 53.2 1 27.5 31 15.7 23.3 14.3 41.9 41.9 35.3 43.9 41.4

Cs 149 267 106 219 138 197 215 165 169 526 2.5 18.1 15.4 8.6 15.6 208.5 199.2 160.2 210.8 207.4

Rb 216 1000 267 1000 319 272 748 1000 1000 1000 58 531.9 482.3 177.7 430.4 3316 3295 2936 3304 3265

Sn 17 19 168 28 115 24 129 86 125 2 165 228 84 207 244 1096 1104 1050 1100 1099

Nb 47 80 102 390 121 139 110 95 87 4 20.2 35.4 42.8 70.2 41.7 378.5 383.1 375.4 375.3 370.5

Sr 28 29 31 24 30 29 30 25 22 43 278.9 33.7 35.4 24.5 26.2 0.9 0.5 0.5 0.5 0.5

Y 4 5 10 4 10 4 10 7 6 2 2 1 3.2 6.4 2.8 0.8 0.2 0.2 0.1 0.1

Ba 47 29 60 29 51 46 55 52 47 49 442 76 91 37 84 2 2 1 1 1

Hf 5.4 4.8 8.2 6.3 7.2 3.9 6.6 8.4 8.2 0.2 6.7 3.5 8.1 2.5 2.3 2.5 0.5 0.6 0.5 0.6

Th 4.1 2.9 12.9 1.5 8.6 3.9 11 4.8 3.9 0.2 2.8 0.5 1.5 2.2 2.1 0.4 0.5 0.2 0.2 0.2

W 1 1 1 3 8 1 1 1 1 3 0.5 0.6 1.3 1.4 1.1 8.8 9 9.9 9 9.2

Be 19 28 35 17 37 42 32 49 82 4 2 37 14 38 80 23 26 25 25 25

Zr 29 26 54 39 48 25 44 100 101 4 152.2 20.8 45.8 27.8 19 22.5 4.4 4.8 2.6 2.5

Ga 62 54 51 66 59 60 53 99 117 37 33 35.2 30.6 32.5 28.5 263.6 257.6 253 259.7 252.7

Zn 30 50 30 50 30 40 30 160 210 30 88 96 45 44 63 32 36 29 24 37

U 4.9 2 6.3 5 4.7 4.6 4.6 2.8 2.5 0.5 6.5 10.5 11.5 24.4 12.8 0.6 0.2 0.1 0.1 0.1

Ti 1.4 22.2 1.9 11.5 2.4 2.4 9.3 4.6 6.6 22.6 0.1 0.1 0.1 0.1 0.1 1.2 1.5 1.2 0.9 1.4

Cu 30 10 30 20 30 20 20 20 20 10 17.9 8.3 5.9 3.9 9.7 0.7 0.3 0.1 0.1 0.2

Li 188.3 199.5 22.2 203.6 158.3 191.5 198.7 201.9 202.7 205.8 45.6 145.2 122.5 112.1 123.2 665.3 336.7 399.5 646.2 583.1

Elements 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Co 1 1 1 1 1 1 1 3 3 1 1.2 0.8 0.3 0.9 0.7 0.2 0.2 0.4 0.2 0.2

V 8 5 15 5 14 12 12 29 30 5 19 8 8 8

8 8 8 8 8

Ni 20 20 20 20 20 20 20 30 20 20 7.7 3.8 3.5 4.3 4 0.6 0.6 0.3 0.3 0.3

Sc 7 3 6 3 7 8 6 6 6 2 1 1 1 2 1 7 8 13 7 8

Pb 14 29 21 19 24 23 35 9 10 39 26.1 24.6 26.8 7.2 21.5 0.8 0.6 0.6 0.3 0.5

Mo 2 2 2 2 2 2 2 2 2 2 1.7 1.6 1 1.2 1 0.2 0.2 0.1 0.1 0.1

La 15.4 6.1 18.5 6.8 17.3 20.8 18.9 21.1 19.7 47.8 4.9 0.3 1 1.3 0.9 0.7 0.3 0.2 0.1 0.1

Ce 27.6 11.5 33.7 12.5 31.6 35.9 34.7 36 31.8 76 8.5 1.2 2.2 3.3 1.8 1.6 1 0.9 0.5 0.4

Pr 4.33 2.09 4.82 2.16 4.53 5.59 5.18 5.34 4.98 13.7 0.99 0.13 0.24 0.4 0.24 0.2 0.1 0.09 0.05 0.05

Nd 15.8 9.3 18.7 9 16.6 20.4 17.4 17.7 16.6 46.2 3.7 0.6 0.4 1.4 0.7 0.8 0.4 0.3 0.4 0.3

Sm 4 2.7 4.7 2.5 4.2 4.9 4.6 3.2 3 7.1 0.72 0.14 0.35 0.54 0.42 0.19 0.11 0.11 0.1 0.09

Eu 0.47 0.66 0.48 0.55 0.44 0.57 0.55 0.62 0.6 1.24 0.45 0.03 0.03 0.03 0.02 0.02 0.02 0.02 0.02 0.02

Gd 3.2 3.1 4.2 2.5 3.7 3.7 3.9 2.4 2.1 3.5 0.58 0.16 0.36 0.57 0.41 0.12 0.06 0.05 0.05 0.05

Tb 0.6 0.5 0.8 0.4 0.7 0.7 0.9 0.4 0.3 0.4 0.08 0.04 0.09 0.17 0.1 0.02 0.01 0.01 0.01 0.01

Dy 2.1 2.3 3.8 1.9 3.3 2.6 3.4 2.1 1.7 1.3 0.36 0.2 0.5 0.98 0.51 0.09 0.05 0.05 0.05 0.05

Ho 0.2 0.3 0.4 0.2 0.4 0.2 0.4 0.3 0.3 0.1 0.06 0.03 0.08 0.15 0.08 0.02 0.02 0.02 0.02 0.02

Er 0.5 0.7 1 0.6 0.9 0.5 0.9 0.9 0.7 0.3 0.2 0.05 0.21 0.49 0.16 0.04 0.03 0.03 0.03 0.03

Tm 0.06 0.08 0.13 0.07 0.12 0.07 0.11 0.12 0.1 0.05 0.04 0.02 0.05 0.1 0.04 0.01 0.01 0.01 0.01 0.01

Yb 0.4 0.5 0.9 0.5 0.8 0.4 0.8 0.8 0.6 0.2 0.26 0.11 0.46 1.01 0.29 0.05 0.05 0.05 0.05 0.05

Lu 0.05 0.06 0.11 0.07 0.11 0.06 0.11 0.11 0.09 0.04 0.05 0.01 0.07 0.16 0.05 0.01 0.01 0.01 0.01 0.01

The numbers 1, 2, 3,….20 represent sample numbers. 1-15: Whole rock Pegmatite samples from Awo

16-20: Muscovite extracts from Awo Pegmatites.



Table Iva

Range and average values of major elements in the whole rock and muscovite extracts of Awo pegmatites in mass fraction (Wt %).

Awo Sample

Whole Rock Muscovite Extracts

Pegmatite

N = 15 N = 5

Range Avr

(%)

Range Avr (%)

Si2O 44.79 - 70.37 54.95 44.27 - 44.89 44.61

Al2O3 14.70 - 33.51 25.77 33.20 - 34.20 33.83

Fe2O3 0.25 - 7.22 2.44 4.36 - 4.52 4.46

MnO 0.008 - 8.41 1.61 0.10 - 0.12 0.12

Mgo 0.01 - 0.14 0.06 0.32 - 0.44 0.36

CaO 0.03 - 1.74 0.30 0.01 - 0.01 0.01

Na2O 0.09 - 4.82 1.28 0.57 - 0.58 0.58

K2O 1.47 - 6.95 3.74 9.85 -10.18 10.05

TiO2 0.01 - 0.199 0.06 0.06 - 0.07 0.07

P2O5 0.016 - 0.41 0.14 0.02 - 0.03 0.03

Table IVb

Range and averages of some of the trace elements in the whole rock and muscovite extracts of Awo pegmatites (ppm).

Awo Sample

Whole Rock Muscovite Extracts

Pegmatite

N = 15 N = 5

Range(ppm)

Avr ppm Range(ppm) Avr ppm

Ta 1.0-365 92.35 35.3-41.9 40.88

Cs 2.5-526 147.41 160.2-210.8 197.22

Rb 58.0-1000 566.82 2936-3136 3223.20

Sn 2-244 109.4 1050-1104 1089.80

Nb 4-390 117.02 370.5-383.1 376.56

Sr 22-278.9 45.93 0.5-0.9 0.58

Y 1.0-10 5.16 0.1-0.4 0.2

Ba 29-442 79.67 1-2 1.4

Hf 0.2-8.4 5.49 0.5-2.5 0.94

Th 0.2-12.9 4.19 0.2-0.5 0.3

W 0.5-8 4.79 8.8-9.9 9.18

Be 2-82 34.2 23-26 24.80

Zr 4-152.2 49.04 2.5-22.5 7.36

Ga 28.5-117 54.52 252.7-263.6 257.32

Zn 30-210 64.13 24-37 31.6

Ti 0.1-22.6 5.69 0.9-1.5 1.24



Table V

Elemental ratios of selected major and trace elements of Pegmatites from Awo study area.

Atio 1 2 3 4 5 6 7 8 9 10

K/Rb 0.0056479 0.0050209 0.004817772 0.0037014 0.004917 0.0045767 0.0023854 0.0026391 0.0026889 0.00483

K/Ba 0.0259564 0.1731343 0.021439083 0.1276329 0.0307551 0.027062 0.0324415 0.0507516 0.0572101 0.0985718

Na/K 0.0668862 0.0369356 0.063433993 0.0380785 0.0472933 0.0536306 0.0498889 0.0449732 0.0524167 0.0460744

Rb/Sr 7.7142857 34.482759 8.612903226 41.666667 10.633333 9.3793103 24.933333 40 45.454545 23.255814

Ba/Rb 0.2175926 0.029 0.224719101 0.029 0.1598746 0.1691176 0.0735294 0.052 0.047 0.049

Zr/Hf 5.3703704 5.4166667 6.585365854 6.1904762 6.6666667 6.4102564 6.6666667 11.904762 12.317073 20

Sr/Rb 0.1296296 0.029 0.116104869 0.024 0.0940439 0.1066176 0.040107 0.025 0.022 0.043

Rb/Cs 1.4496644 3.7453184 2.518867925 4.56621 2.3115942 1.3807107 3.4790698 6.0606061 5.9171598 1.9011407

Ta/W 42.4 113 113 102.66667 12.025 365 101 80.6 53.2 0.3333333

K/Cs 0.0081876 0.0188049 0.01213533 0.0169012 0.011366 0.006319 0.008299 0.0159944 0.0159105 0.0091825

Zr/Zn 0.9666667 0.52 1.8 0.78 1.6 0.625 1.4666667 0.625 0.4809524 0.1333333

Th/U 0.0084699 0.0361632 0.00674185 0.0216682 0.0071038 0.0101105 0.0056584 0.0255911 0.0330813 0.0688691

Ta/Nb 0.9021277 1.4125 1.107843137 0.7897436 0.7950413 2.6258993 0.9181818 0.8484211 0.6114943 0.25

Nb/Ta 1.1084906 0.7079646 0.902654867 1.2662338 1.2577963 0.3808219 1.0891089 1.17866 1.6353383 4

K2O/Na2O 13.363636 24.2 14.09090909 23.473684 18.9 16.666667 17.916667 19.875 17.052632 19.4

Na2O/Al2O 0.0034172 0.0085793 0.003800968 0.0059994 0.0030414 0.0031513 0.0040678 0.0048265 0.0056699 0.0103591

K2O/Al2O3 0.0456664 0.2076184 0.053559088 0.1408273 0.0574818 0.052521 0.0728814 0.0959276 0.0966876 0.2009669

Ratio 11 12 13 14 15 16 17 18 19 20

K/Rb 0.0293327 0.0108438 0.0112191 0.0138239 0.0122248 0.0024652 0.0025615 0.0028323 0.0025244 0.0025876

K/Ba 0.0038491 0.0758922 0.059461 0.066392 0.0626377 4.0872575 4.2200415 8.315598 8.340495 8.448382

Na/K 1.2775409 0.258507 0.5511116 1.455514 0.5301023 0.0517249 0.0509763 0.0508473 0.0515849 0.0509262

Rb/Sr 0.2079598 15.783383 13.624294 7.2530612 16.427481 3684.4444 6590 5872 6608 6530

Ba/Rb 7.6206897 0.142884 0.1886792 0.2082161 0.1951673 0.0006031 0.000607 0.0003406 0.0003027 0.0003063

Zr/Hf 22.716418 5.9428571 5.654321 11.12 8.2608696 9 8.8 8 5.2 4.1666667

Sr/Rb 4.8086207 0.0633578 0.0733983 0.1378728 0.0608736 0.0002714 0.0001517 0.0001703 0.0001513 0.0001531

Rb/Cs 23.2 29.38674 31.318182 20.662791 27.589744 15.904077 16.541165 18.327091 15.673624 15.742527

Ta/W 55 51.666667 12.076923 16.642857 13 4.7613636 4.6555556 3.5656566 4.8777778 4.5

K/Cs 0.680518 0.3186633 0.3513603 0.28564 0.3372799 0.0392063 0.0423699 0.0519076 0.0395659 0.0407347

Zr/Zn 1.7295455 0.2166667 1.0177778 0.6318182 0.3015873 0.703125 0.1222222 0.1655172 0.1083333 0.0675676

Th/U 0.3934664 1.4707535 0.345223 0.4520921 1.118349 0.0557601 0.3466628 0.3136084 0.3652238 0.6028739

Ta/Nb 1.3613861 0.8757062 0.3668224 0.3319088 0.3429257 0.1107001 0.1093709 0.094033 0.1169731 0.1117409

Nb/Ta 0.7345455 1.1419355 2.7261146 3.0128755 2.9160839 9.0334129 9.1431981 10.634561 8.5489749 8.9492754

K2O/Na2O 0.6996587 3.4577114 1.6218905 0.6141079 1.6861702 17.280702 17.534483 17.578947 17.327586 17.551724

Na2O/Al2O 0.1819876 0.1221142 0.2529893 0.323273 0.2557823 0.0166667 0.0174699 0.0167155 0.0170188 0.0172825

K2O/Al2O3 0.1273292 0.4222357 0.410321 0.1985245 0.4312925 0.2880117 0.3063253 0.2938416 0.2948944 0.3033373

The numbers 1, 2, 3,…20 represent sample numbers.

1-15: Whole rock Pegmatite samples from Awo

16-20: Muscovite extracts from Awo Pegmatites

keywords: petrographic, pegmatite, metasomatic, quartz

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