University of Nigeria Research Publications

ANIKE, Okechukwu Luke

Aut

hor

PG/M.Sc/83/1912

Title

The Geology and Economic Mineral Deposits of Areas Around Muro Hill,

Nigeria

Facu

lty

Physical Sciences

Dep

artm

ent

Geology

Dat

e

February, 1987

Sign

atur

e

A Dissertation presented to the Department of Geology, Un5versity of Nigeria, Nsukka in partial fulfilment of the requirements for the award of degree of MASTER

017 SCIENCE (M.sc) IN GEOWSY

UNIVERSITY OF NIGERIA, NSW.IG1

To My Brother,

Patrick. . . .-

CERTIFICATION

Mr. hike, Olcechulcwu Luke, a postgraduate student in

the Department of Geology, University of Nigeria, Nsukka, has

satisfactorily completed the requirements for course work and

research project for the degree of Master of Science (M.SC

Economic Geology and Geochemistry) in Geology.

The work embodied in this dissertation is original and

has not been submitted in part or in full for any other diploma

or degree of this or any other university.

Dr. A.C. Umeji (Supervisor ) Department of Geology University of Nigeria Nsukka.

Dr. A.C. Onyeagocha (supervisor) Department of Geology University of Nigeria Nsukka.

Mr. IK. N. Ogbukagu Head Department of Geology University of Nigeria Nsukka .

CONTENT

Abstract .. . . . . . . L i s t of Tables . . . . L i s t of Figures . . . . Aclcrlowledgement . . . .

CHAPTER

ONE INTRODUCTION 0 0

. . .. iii

1.1 Background t o problem. ob jec t ives and scope of s tudy . . . . . . . .

1.2 Location and Access ib i l i ty .. . . 1.3 L i t e r a t u r e review .. . . . . . . 1.4 G e o l o g i c s e t t i n g .. . . . . . .

TWO DESCRIPTION OF ROCK UNITS I N TI-E MURO SCHIST BELT . . 0 - 0 0 0

2.1 F i e l d r e l a t i o n s h i p s and l i tho logy

2.2 Petrography . . . . 2.3 St ruc tu res . . . .

THEZEE MINERAL DEPOSITS .. . . 3.1 I ron formation . . 3.1.1 Mode of occurrence

3.1.2 Mineralogical types

3.1.3 Geochemistry . . 3.2 Marble deposi t . . 3.2.1 Mode of occurrence

3.2.2 Types of marble and mineralogy

3.2.3 Geochemistry . . . . . . 3.3 Environment of deposi t ion . . 3.4 Economic evaluat ion . . . .

FOUR SUMMARY AND CONCLUSIONS . . . . REFEIZENCES - 0 . 0 0

APPENDICES . . .

Abstract

0 0 The study area (longitude 7 15' 1311E to 7 20' 55"E and

latitude 8O 151N to 8O 26' 0611~), contains/ granite gneiss, mica

schist, calcite marble, quartzite and banded iron formation (BIF).

Granite gneiss, mica schist and marble occupy the lowlands while

quartzite and BIF form elongate ridges 75 to 250 m above the

surrounding terrains. Contact relationships between rock types

are gradational, and a stratigraphic sequence comprising;

1. granite gneiss (~asement), 2. basal mica schist, 3. marble

4. foliated quartzite, 5. BIF, 6. non-foliated quartzite and

7. upper mica schist, from bottom to top, is established.

The original sediments laid down in a shallow, restricted

continental basin, comprised of both clastics (pelitic and semi-

pelitic sediments) and chemical precipitates. The sediments

were metamorphosed and deformed dbring the Pan-African (600 4 150

~ 7 a ) thermotectonic event. The metamorphism ranges from chlorite

zone to the lower part of the garnet zone, in the greenschist

facies.

' The economic mineral deposits in the area are the BIF

and the calcite marble. The BIF occurs as three ore bodies;

M-1, M-2, and S-1. The ores have iron content varying from 29.59 6

to 36.72%. They are slightly impure, containing both sulphur and

phosphorous impurities. The inferred ore reserve is nbou-L

9 3.18 x 10 tons. Calcite marble is more exte11s.l .~t. aj~:.l iia:; ; , ! I

ii.

11 inferred reserve of about 1.49 x 10 tons. It is relatively

pure and has CaCO content ranging from 84.41 to 88.27%. Its 3

MgO content varies between 2.12 and 2.20%. It has colours

which vary from white, greenish or pinkish white to grey.

iii

LIST OF TAI3LES Page

Summary of mineral assemblages in rocks studied 24

Average modal composition (vol. %) for rocks studied .. . . . . . . . . . . . . . . 25

Stain characteristics (in Lemberg solution) of some carbonate rocks from study area . . 32

Chemical analysis of iron ores from Muro hills, Nigeria .. . . . . . . . . . . . . . . 41

Chemical analysis of Itakpe hill iron ores, Nigeria .. . . . . . . . . . . . . . . 43

Chemical analysis of Pisolitic ironstones from Agbaja Plateau, Nigeria . . .. . . . . 44

Chemical analysis of Enugu ironstones, Nigeria 45

Chemical analyses of selected BIF from United States of America, Western Australia, Southern Africa and MIXS-IF (~etazoan-poor, extensive, cnemical sediment-rich, shallow sea iron formation) . . . . . . .. . . . . . . 4.6

Chemical analysis of marble from Muro area, Nigeria . . . . . . . . . . . . . . . . 61

Average chemical analysig of some marble deposits

LIST OF FIGURES Page

1. Map of Nigeria showing study area and distribution of metasedimentary belts .. . . . . . . . . 4.

2. Map of Muro area showing distribution of ridges and the drainage system .. . . . . . . . . 5

3. Geological map of areas around Muro hill .. . . 16

4. Granite gneiss outcrop showing banding and foliation with a NE-SW trend which is also the general orientation of the quartzite lenses (Q) 18

5. Folding in mica-rich BIF, West of Muro Kasa . . 21

6. 'Massive' BIF with dense fracturing, East of Chekugwari . . . . . . . . . . . . . . 2 1

7. Microbanding in Quartz + haematite (4 magnetite) schist: defined by irregular masses of haematite ( 2 magnetite) - dark bands, and quartz-rich matrices - light bands . . .... . . . . . . . . 2 9

8. Rose diagram indicating trends of foliation in rocks of study area .... .. . . .. . . 35

9. ~l-Si-~e(+ ~ n ) relationships in iron ore samples from Muro, Itakpe, and Agbaja iron mineral deposits in Nigeria .. . . . . . . . . . . . . . . 48

10. Distribution of rock sample locations . . . . 92

I am most grateful to my supervisors: Dr. A.C. Umeji

and Dr. A.C. Onyeagocha for their guidance at the various stages

of this work. My indebtedness also goes to other workers in

the Department of Geology, University of Nigeria, Nsukka (uNN),

especially: Dr. C.O. Okagbue, Dr. L.I. Mamah, and Mr. Stan. hi.

I acknowledge the assistance of the following persons: the Head,

Department of Biochemistry, UNN, Messrs. B.1. Nnagha, A.E. Edu,

H. Okoli and Eo Nwankwo of Associated Ores Mining Company

(A.o.M.~) field camp, Gadabuke, Mr. Emeka Okafor of National

Steel Council, Jos, and Dr. Ogomegbunam Emehelu of the Department

of Veterinary Medicine, UNN. I am grateful to Professor M.A.

Olade of the Department of Geology, University of Ibada, Nigeria,

for his suggestions. My sincere gratitude also goes to all other

persons who contributed to the completion of this work.

ANIKE, 0.L.

November, 1986.

CHAPTER ONE

INTRODUCTION

1.1 Background to Problem, Objectives and Scope of Study -

'The development of steel complexes in Nigeria has generated

the problem of locating sources of iron ores in the country Lo feed

the complexes. Available records indicate the presence of

sedimentary ironstones around the Agbaja plateau in Middle Niger

basin ones, l955), and Udi hills near Enugu (Simpeon, 1954,

Hazel, 1955). These ironstone occurrences were not well assessed;

their total reserves and chemical qualities were not studied in

detail. Hence their' viability 'as sources of iron ores for the

Nigerian steel industry was not emphasized.

Recently, a metamorphosed iron ore deposit was discovered

at the Itakpe hill, near Okene in 1975;, by the National Steel

Council (N.S.C). The N.S.C assessed this deposit in detail, and

the general features of the iron ores have been described by

Olade (1978) and Fadare (1982). The deposit is presently being

developed by the Associated Ores Mining Company. It is envisaged

to be the main source of iron ore to the steel complexes, but its

proven.,reserve of about 2.5 x lo8 tons lade, 1978) is considered

inadequate to sustain the complexes for a long period. In view

of this, efforts are being made to locate other iron ore deposits.

b

In 1979, the Geological Survey of Nigeria (GSN) reported the

presence of banded iron formation (BIF) deposit at the Muro hill

2

in Plateau state, while mapping the GSN degree sheet 228: Katalcwa

sheet. A preliminary description of the BIF was made by Mogbo

et a1 (1981), but the detailed geology of the deposit and the

chemical quality of the iron minerals were not given. Therefore,

further work was required on the deposit to assess the suitability

of the BIF for the steel complexes.

One main feature of the Nigerian steel industry is that the

plants in the steel complexes are designed to use direct reduction

blast furnaces. This type of blast furnace uses fluxing agents

such as flouspar and bauxite (Sharp, 1966) and lime (CaO) for the

reduction of iron ores. The lime is often obtained from marbles.

Records available show that marble deposits have been located in

Jakura, Igbetti, Elebu, Itobe, Burum, Ukpilla, Iuwa and Igarra

areas of Nigeria (~ogbe and' Obialo, 1976, Okezie, 1982). Some

other deposits are known to occur near the Ubo river in Kwara

state (Kayode and Enu, 1976). These marbles have not been well

studied, and except for those of Ukpilla and Jakura with lime

contents 51.29%, 54.054'0, respectiyely, others have very low lime

content ranging from 26.40 to 39.5096 (GSN Report 1192, 1963).

This indicates that majority of the known marble deposits in

Nigeria may not be suitable for the supply of lime in the Nigerian

$tee1 complexes. A new marble deposit, the Obugu marble (~ogbo

and Nnolim, 1985), was recently discovered near the B I F deposit.

This marble was however not analysed and ; t a cm~l )~) . : i t. i . . s r : I.J~ILI~(>WII.

3

-The presen t s tudy i n v e s t i g a t e s the geology of t h e B I F and

the Obugu marble, and presents a geological map of the a r e a i n

which these deposi t s occur. The chemical composition of t h e BIF

and t h e marble a r e a l s o determined and described. An attempt is

a l s o made t o reconst ruct t h e environment i n which these deposi t s were

formed.

1.2 Location and Access ib i l i ty

The Muro a r e a l i e s about 100 km northeast of the confluence

between Rivers Niger and Benue, i n t h e c e n t r a l p a r t of Nigeria

F i g 1 The a r e a s tudied extends from the southwestern p a r t of

t h e N a s a r a w a D i s t r i c t i n Plateau S t a t e t o t h e southeastern margin

of the f ede ra l c a p i t a l t e r r i t o r y of Nigeria. The a r e a i s appro-

2 x i n ~ a t e l y 208.59 k m , running from Gadabuke t o Di t iko on t h e north-

south a x i s , and Chekugwari t o Kudu on t h e east-west axis . It is

bounded by longitudes 7'151 13"E and 7O201 55%, and l a t i t u d e s

8 O 1 5 ' ~ and 8 O 26' O G ~ I N . The a r e a occupies t h e nor theas tern

quadrant of t h e GSN sheet 228-Katakwa shee t ; and forms the

southern t i p of t h e Basement Complex i n northern Nigeria.

The geomorphic na ture of the a r e a c o n s i s t s of undulating

lowlands, broken i n p laces by long, north-south trending r idges

and escarpments ( ~ i ~ . 2). The length of the r idges and escarpments

, ranges from 2 t o 5 km, and t h e i r he ights vary from 75 t o 25Om above

t h e surrounding surface. The r idges have s t eep s i d e s , while t h e

FIG. 1 . Mop o f Nigeria showing study area and distribur~on of rnet .?s:di~~-vr , ! . r )

FIG. 2 . Map o f Muro areas showlng dlsrrlbutron of Ridges and dralnage system.

escorptnents have very steep scarps and dip slopes which grade

gently into open valleys. The escarpment which occurs immediately

south of Muro and disappears southwards, often referred to as the

Wuro hill" contains this BIF. This escarpment was especially

investigated in the study. The escarpments and ridges are usual.ly

separated from one another by wide, shallow valleys. Deep valleys,

gorges and minor cataracts are sometimes developed at the foot or

some of the ridges and escarpments, especially in the southern

parts of the study area, near Obugu. The valleys are covered by

streams. The main streams develop dense tributaries and form

good dendritic drainage patterns (Fig. 2). A few of the main

streams are perennial. The tributaries contain water only during

the wet season. They form dry valleys during dry seasons. These

seasonal dry valleys have excellent exposures because of the deep

cut they have made across different lithologic units. Some of the

ones encountered during the field survey are shallow and expose

only one type of lithology. These valleys also act as routes for

the rural population as they connect farmlands and settlements.

Farmlands and settlements are also connected by foot paths

especially along the wide valleys.

Apart from the footpaths and stream courses, accessibility

to theb study area is poor. The main rou-te to the area is a single-

carriage way which runs from Keffi through Gadabuke to Abaji in the

federal capital territory. Muro village is situated about 10 km

east o f t h i s Abaj i -Keff i road. T h i s v i l l a g e and o t h e r r u r a l

s e t t l e m e n t s i n t h e a r e a such as Obugu, are connected t o t h e road

by narrow f o o t p a t h s and minor roads which are motorable on ly

dur ing t h e dry season. These minor r o a d s are impassable dur ing

the weL seasot1 as t h e y become s l i p p e r y , and some o f t h e strcans

rumling a c r o s s them are no t bridged. A c c e s s i b i l i t y i s f u r t h e r

reduced by t h e presence of numerous s t e e p s lopes .

1.3 L i t e r a t u r e Review

There is genera l ly a few desc r ip t ions of t h e geology and

economic p o t e n t i a l of t h e i r o n mineral and marble depos i t s i n

Nigeria. A b r i e f review of the work done on these deposi t s i s

presented below.

Iron Mineral Deposits

A survey of a v a i l a b l e records shows t h a t two main groups of

i r o n mineral depos i t s occur i n Nigeria. These are: t h e sedimentary

i rons tones found i n t h e sedimentary bas ins of the country, and i r o n

mineral depos i t s a s soc ia ted with t h e Precambrian basement complex.

More work has been done on t h e i rons tones than on t h e depos i t s of

t h e basement complex. Two main i rons tone deposi t s ; t h e Agbaja

i rons tone i n t h e middle Niger bas in and t h e Enugu i rons tone i n tlic

Allambra bas in , have been well described. Jones (1955), and

Adeleye (1973, 1976) described t h e Agbaja i ronstones. Adeleye

(1976) showed t h a t t h e i rons tone deposi t i s well developed 011 t he

Agbaja p la teau , and extends from Lokoja on t h e Niger/IJenue con-

f luence t o areas nor th of Bida i n Niger state. The deposi t

co~uprises an upper and a lower i rons tone beds, separated by an

a rg i l l aceous l a y e r of mainly s i l t s t o n e deleye ye, 1973). These

u$per and lower beds a r e c a l l e d Sakpe i r o n formation and Ba ta t i

i r o n formation respec t ive ly , around Bida areas. The beds lhave

l~~aximurn th ickness of about 15m. The i rons tone is g e o t h i t i c and

9

l imoni t i c i n composition and o o l i t i c and p i s o l i t i c i n texture .

Ool i t e s vary from lmm t o 2mm and a r e sometimes k a o l i n i t i c

deleye ye, 1976). Preliminary chemical analyses of the i rons tone

repor ted by Jones (1955) i n d i c a t e t h a t it has i r o n oxide content

of between 68% and 73%. The phosphorus content a s P 0 ranges 2 5

from 1.9% t o 3.04, while sulphur v a r i e s from 0.08% t o 0.15'$. Its

9 est imated reserve i n Lokoja a r e a only i s 7.0 x 10 tons deleye ye,

1976) and t h e deposi t is covered by t h i c k mantle of l a t e r i t e s

with an average th ickness of about 9.3m. Hazel (1955) described

t h e occurrence of a s i m i l a r g e o t h i t i c i rons tone deposi t - t he

Ihiugu i rons tone - i n Enugu a r e a of e a s t e r n Nigeria. Ile rioLcd

t h a t t h e deposi t extends from w e s t of Enugu escarpment t o

hnansiodo i n Oghe. The i rons tone occurs a s angular blocks

embedded i n loose sandy matrix. The matr ices a r e sometimes

cemented i n t o compact rocks. Simpson (1954) recognised t h a t

'hard pans' of ferruginous s i l t s t o n e s and sandstones sometimes

occur above coal s e a s i n Enugu area. Chemical a n a l y s i s shows

t h a t the Enugu i rons tone is poorer i n i r o n oxides than the Agba;ja

i ronstone. The i r o n oxide content v a r i e s between 61% and 63%

(llazel, 1955) and t h e est imated o re reserve i s about 6.0 x 10 7

tons. Ironstone occurrences i n o the r Nigerian sedimentary bas ins

ha& not been reported. Occurrences of t h i c k l a t e r i t i c depos i t s

a r e mentioned by Okezie (1982).

The study of the second group of i r o n mineral depos i t s i n

10

Nigeria - those associated with the basement complex - had bean given little attention until recently. The work of Truswell and

Cope. (1963), Ajibade (1976) on the schist belt of northwestern

Nigeria, indicated the presence of phyllites and mica schists studded

wi Lli octahedral magnetite in the Birnin Gwari formation. A,j ibade

(lc)7()) also recognised the presence of ironstones with a1 ter.iinljt~g

Lmtlcls of iron ore and pure quartzite in the Koriga ferr-uginous

quartzite member of the Kushaka schist formation. These iron

mineralizations were considered scanty and attracted no attention.

Intensive search for iron mineral deposit in the basement complex

of Nigeria bcgan with the establishment of the National Steel

Ilevelopment Authority (now National Steel Council (N.s.C.)) in

1971. In 1975, the NSC discovered the iron ore deposit at the

Itakpe hill, near Okene in Kwara state. This deposit has been

described by Olade (1978) as a metamorphosed iron-rich sediment,

occurring in a gneiss-migmatite-quartzite suite of the Basement

Cotuplex. Its ore minerals comprise: massive magnetite, banded-

granular haematite-magnetite, and schistose haematite. The ore

reserve of the deposit has been evaluated by the NSC and the

chemical composition of the ores described by Olade (1978) and

Fadare (1982). Fadare (1982) also noted the presence of otl.ier

nietam&phosed iron ores such as Chokochoko, Aybado-Okudu, Ozenyi

and Udiarehu deposits. These are mainly bands and lenses of

ferruginous quartzites, hosted by gneisses and amphibolites.

11

The U I F deposit discovered near Muro, occurs within a belt of

mica schists ( ~ o ~ b o et al, 1981, Nnagha et al, 1984).

i'larbl e Deposits

Okezie (1982) noted that the first marble deposit discovered

in Nigeria is the Jakura marble. It was discovered by the Mineral

Survey of Northern Nigeria in 1908, and was further investigated

between 1949 and 1951. The exploitation of this deposit did not

start until 1963 when the Nigerian Marble Industry produced about

40 tons of marble from the deposit ( ~ o ~ b e and Obialo, 1976). The

marble produced was essentially used as chips for terrazzo. The

Iybetti marble in Oyo state, was later discovered by the Geological

Survey Department in 1955 (~kezie, 1982). It was exploited and

used as terrazzo chips. Between 1956 and 1964, other marble

deposits such as, the Burum dolomitic marble, and the Ubo marble

were discovered. Subsequently, marble deposits have been found

in Itobe, Iuwa, Elebu, Taka-Lafia in Kwara state and Ukpilla in

Uendel state. All these marble deposits except that at Ukpilla

are mainly used for production of terrazzo chips. The Ukpilla

marble is mainly used for cement production. Some of these marble

deposits; especially those at Burum, Elebu, Igbetti, Jakura and

ukpi\la have been described and analysed for major oxides (GSN

Report 1192, 1963). Kayode and Enu (1976) noted that the marble

deposit near the Ubo river - the Ubo marble - has been affected

I 2

I I \ I I I : L ~ ~ I ~ ~ : ~ ( i~itrusioli resultiny in formation of para-wollastonite

arltl wvllast,o~iite in the marble. They also described the chemical

composition of the parawollastonite and wollastonite-rich zones

of the Ubo marble. The Obugu marble has been described as

dolomitic marble (~kezie, 1982, Nnagha et al., 1984, Mogbo and

Nnolim, 1985), but the present work indicates that the marble

is calcic and only a few grains of dolomite occur in some

samples.

1.4 Geologic Setting

Fig. 1 shows that almost one half of Nigeria is covered

by Basement Complex rocks. The other half is covered by sedi-

mentary rocks. The Basement Complex contains three major groups

of rocks, namely; the 'older metasediments', the 'younger meta-

sediments' (~yawoye, 1964, 1972), and the 'older granites'

(~alconer, 1911).

The older metasediments consist of crystalline gneisses

and migmatites of amphibolite facies metamorphism (~jibade, 1976).

~he~contain units of migmatites, granite gneiss, banded gneiss,

augen gneiss and biotite gneiss. These rocks, especially the

granite gneiss, have ages between 1900 2 250 M.a and 2200 M.a

(&ant, 1971, Burke et al. , 1972; Hubbard, 1975). Granite gneiss

etnplaced in a banded gneiss-quartzite complex near Ibadan gave

Rb-Sr isochron age of 2205 70 M.a hu rant, 1970) and indicates

13

t h a t tile rocks a r e a s s o c i a t e d w i th t h e Eburnean orogeny (Raharnan

1976a, FlcCurry 1976). Gran i t e g n e i s s from I l e - I f e gave Rb-Sr

isochron age o f about 1150 2 140 M . a , and is a s s o c i a t e d wi th t h e

Kibaran orogeny rant, 1978). The rocks o f t h e o l d e r metasedi-

n ~ e n t s are sometimes g r a n i t i z e d (odeyemi, 1976, Rahaman, 1976a) and

show polyphase deformation. I n p a r t s o f t h e nor thwes te rn and

southwestern areas o f N ige r i a , t h e o l d e r metasediments are o v e r l a i n

by t h e younger metasediments.

The younger metasediments comprise l i n e a r b e l t s of meta-

sedimentary and metaigneous rocks ; c o n s i s t i n g mainly of mica

s c h i s t s , q u a r t z i t e s , c a l c - s i l i c a t e s , and marbles. The metamorphic

grade of t h e s e rocks ranges from g r e e n s c h i s t t o lower amphibol i te

f a c i e s metamorphism (Cooray, 1974; Ajibade, 1976, Rahaman, 1976b).

These r o c k s are a s s o c i a t e d w i th t h e Pan-African orogeny (600 2

150 M . a , Hubbard, 1975, Klemrn e t a l , 1984). A l a r g e p a r t o f West

Af r i ca , i nc lud ing t h e whole o f N ige r i a , was a f f e c t e d by t h e

a c t i v i t i e s o f t h e Pan-African orogeny ( ~ u r n e r , 1983). Th i s

orogeny e s s e n t i a l l y r e a c t i v a t e d t h e o l d e r c r u s t o r Basement

( ~ l a c k ' a n d Girod, 1970; Olade, 1980; Turner , 1983) and meta-

morpliosed sediments ove r ly ing t h e c r u s t i n t o s c h i s t b e l t s . These

s c h i s t b e l t s a r e o f t e n r e f e r r e d t o a s Pan-African s c h i s t b e l t s

( ' r rus twel l and Cope, 1963; Kennedy, 1964; Grant , 1978) o r upper

I '1~oterozoic s c h i s t b e l t s ( ~ u r n e r , 1983). I n N ige r i a t h e s e s c h i s t

b c l t s are conunon i n t h e northwestern and southwestern s e c t i o n s of

the country (~uss, 1957; Oyawoye, 1964; Turner, 1983). Similar

schists are also found in the southeastern parts of the country

(~aeburn, 1927; Rahaman et al., 1981; Ekwueme and Onyeagocha

1985, 1986). Those described by Ekwueme and Onyeagocha (1985,

1986) are Pan-African in age. They range from middle green-

schist facies to uppermost amphibolite facies metamorphism. The

schists are folded together with the older metasediments into

tight isoclinal folds, exhibiting a generally N-S axial trend

(~jibade, 1976). The Muro schist belt which occurs in the

southeastern margin of the Basement Complex in north central

part of Nigeria (~ig 1) is described in this work.

The third group of rocks in the Basement Complex comprises

of porphyritic biotite granites, fine grained biotite granites,

biotite-muscovite granites, granodiorites, diorites, yabbros,

quartz-syenites and charnockites. These constitute the older

granite suites, which intruded into the older and younger meta-

sediments during the Pan-African oroyeny.

CHAP'lXR TWO

DESCRIPTION OF ROCK UNITS I N T W MURO SCHIST BEL'L'

The fo l lowing rock u n i t s ; g r a n i t e g n e i s s , m i c a s c h i s t s ,

marble , q u a r t z i t e and BIF occur i n t h e Muro s c h i s t b e l t . The

g r a n i t e g n e i s s forms t h e basement, and is o v e r l a i n by t h e o t h e r

u n i t s . Below is a summary o f t h e sequence of t h e rock u n i t s :

Upper mica s c h i s t ;

/

non- fo l i a t ed q u a r t z i t e ;

BIF

f o l i a t e d q u a r t z i t e

marble

b a s a l mica s c h i s t

g r a n i t e gneiss .

A d e s c r i p t i o n of t h e f i e l d r e l a t i o n s h i p s , l i t h o l o g y , pe.trography

and s t r u c t u r e s o f t h e rock u n i t s is given below.

2.1 F i e l d Re la t i onsh ips and Li thology

The d i s t r i b u t i o n of t h e seven major rock u n i t s and minor

i n t r u s i v e s t h a t c rop ou t i n t h e s tudy area is shown i n Fig. 3.

Gran i t e g n e i s s , t h e o l d e s t u n i t and t h e lowest i n t h e sequence,

c rops o u t on ly i n t h e e a s t e r n p a r t o f t h e area. Its ou tc rop are

ex tens ive sou th of Kudu and sometimes t r a c e a b l e f o r more than a

ki lometre . Around Tamako i n t h e no r th , t h e ou tc rops are i n t h e

.forel o f s m a l l patches.

L E G E N D

Muscovite sch~st

@ Doierite

a Dip & str ike Strooms

@ Spot height

' 1 a Settlement

a Inferred geologic boundary

I/ Geologic boundary

Sectton A - A 1 looo 500

7. Upper n l c o schist 6. Non-foliated quartzite 5 . Banded iron forniat~on ( BlF 4. Foliated quartzite 3, hlarble 2. Basal mica schlst

B , ,, 1 . Granite gneiss (Bosenient)

F i G . 3 . G~yiuglcai m o p o f areas around Muro H i l l .

--

The granite gneiss is pinkish in colour due to abundance

of pink microcline feldspar. The pink masses are sandwiched

by small dark bands or streaks rich in greenish mica, in some

of the samples. This type is called 'banded granite gneiss' and

consists of alternating pink and dark grey bands. Banding and

foliation in the gneiss have a general NE-S'W trend (pig. 4 ) . The

ones which consist of a uniform matrix of pink feldspar and

greenish mica are called 'massive granite gneiss'. The massive

and banded granite gneiss varieties occur together in outcrops

and do not form separate mappable units. In weathered outcrops,

they appear greyish, with flaky and lustrous micas or mica bands.

The banded or massive gneisscontains numerous whitish to grey

quartzite lenses, with sizes varying from a few millimetres to

tens of centimetres and oriented in NE-SW, NW-SE or E-W directions

(Fig. 4). These lenses have short, regular and elongated,

irregular forms. North of Kudu, about four kilometres on the

Kudu-Soka road, the gneiss is intruded by a dark green dolerite

which is highly weathered. The granite gneiss is overlain by the

basal mica schist.

The basal mica schist occupies most of the lowlands

separating ridges and escarpments in the study area. On the

eastern section, near Soka, the schist becomes garnetiferous and

is described as biotite-garnet schist. Outcrops of the 1)asal

mica schist are poorly exposed, except ~:!.oII!, w-i c!le r- i vet v , * ' i l I?\;..:

Fig. 4. Granite gneiss outcrop showing banding and foliation with a NE-SW trend which is also the general orientation of the quartzite lenses (Q)

J 9

a r ~ d dl-y stream channe l s . I ( e s i s t a n t s c h i s t masses son~cLinres

~ ) ~ - o j c c t above s u r r o u n d i n g s u r f a c e s a round kluro, s o u t h of iioit.3

n ~ l d cask of Solca. The b a s a l m i c a is c h a r a c k e r i s e d by irre!lr~l;r~

I ::m i tiac.

Overlying t h e b a s a l mica s c h i s t is a l h i c k bcrl o I' I I I X L L jJ I,

wl~ic l i c r o p s o u l e x t e n s i v e l y a round bluro Kasa i l l l h c 11orLl1 a110

O l ~ ~ t g u in t h e sou th . The s c h i s t - m a r b l e c o n - t a c t is t r a ~ i s i l i o ~ m l

a ~ ~ c l i s marked by p a t c h e s o f y e l l o w i s h brown calc-silicates.

The marb le h a s w h i t e , s t r e a k e d o r banded and g r e y v a r i e t i e s .

T11e w h i t e marb le is dominant i n t h e sout11er1-I p a r t o f t h e s t u d y

a.rea, a r o u n d Obugu, J i m b a s e r e , a n d even e x t e n d s . lo T i d i k e Leyo~lcl

t h e map area, where it is being q u a r r i e d . Grey arid s t r e a k e d

marb le are cornmon a round Muro K a s a . O u t c r o p s o f ~ n a r b l e are

found a t t h e f o o t o f r i d g e s a n d a l o n g stream c h a n n e l s . The

s u r f a c e s are dei lse ly f r a c t u r e d , and most o f t h e f r . ac1~r r . e~ arc

widened by s o l u t i o n e r o s i o n . The upper s t r a t i g r a p h i c h o r i z o r ~ s

o f soule o f t h e marb le o u t c r o p s are q u a r t z - r i c h , f r i a b l e and

g r a d e i n t o q u a r t z i t e . I

Q u a r t z i t e c r o p s o u t o v e r rnosL o f t l ~ e r i d g e s occurr-i11r1 i 11

1 1 1 ~ s l u d y area. I t c o n s i s t s o f a lower rol inl.etl ; i t i t l all Ilpljcbr

. I I I V 'L'o~~clo h i l l , o n l y f o l i a t e d q u a r t z i lc crops o r ~ L ; u l ~ i l c , : :O I I I I I

(*;r-;I oC I 'csi~l it is d i r e c t l y o v e r l a i l l 11y t.hc rloll-fol i c ~ l ( s l l

2()

quai-Lzi te . Except on Lhe h i l l s o u t h e a s t o f l J e s i n , w1ic1-c i t C J ol)c7

o u t as Lliin y e l l o w i s h brown l a y e r , t h e n o n - f o l i a t e d q r~nr t , i s i t c arc.

I o ~ u i d as small p a t c h e s i n most o u t c r o p s . The So l i aLr t l qunrL;.,i Lc

is t h e most widespread and w e l l developed u n i t o f t h e q ~ ~ a r t z i t e .

I t is f o u r ~ d a t t h e s l o p e s o f r i d g e s around bluro, Obugu and Pesir i .

'I'he f o l i a t e d q u a r t z i t e i s sometimes f c r r u g i n o h s ; i t is u s u a l l y

f o l d e d b u t t h e s e f o l d s are n o t e a s i l y d i s c e r n e d i n t h e f i e l d o r

i r i liand specimen i f t h e r e i s no consp icuous c o l o u r v a r i a t i o n s

betweell bands.

The UIF which i s h o s t e d i n t h e q u a r t z i t e i s o f ecoriou~ic

iroportance a i d h a s o u t c r o p t h i c k n e s s between 1.0 m e t r e s and 20

nlutres. Its t h i c l c e s l o u t c r o p is observccl abor~L 500 rnetres e a s i

o f Clrekugi~ari v i l l a g e . Th ick bands of q u a r t z i t e a l l ~ r v ~ i t l c w i I I \

i l l i l l d a r k i r o ~ i - r i c h bands. West o f Huro l i a sa , t h e il.011 i ic.11

l i d ~ ~ t l s a r e ciii-iched i n ~ i i i c a a ~ l d t h e bands are f o l d e d ( 1 , i ( 1 . T i ) .

1i1i.s n ~ i c a r i c h v a r i e t y is moLtled i n c o l o u r , w h i l e t l ic mir-;) I)or)J

~ I I I ( . . . v a r y IIWII~ b l u i s h g r e y t o ~ ~ ~ e t a l l i c g rey . 1 la l l c . 1 i l l c,

I I I I ~ Lo ~ n c d i u ~ r ~ g r a i n e d and w e l l banded. 'the bands a r c ' . Y I I ~ ) I - ~ ,

U L c l o~icjaLecl, have t h i c l a ~ e s s e s betwee11 10 IIIII I arid 5 C H I , a l r c l . t ~ ( '

1 ) : ~ t a l l e l t o s u b p a r a l l e l . The b l u i s h g r e y var ieLy h a s very S ' i l l t ~

I n ~ ~ ~ i l ~ a e t h a t a r e oILeil i n d i s L inc t a t ~ d i s soli~e Limes 111assi VP.

'1'11; tm~idcd a ~ l d r~ iass ive Lypes o c c u r t o g e t h e r i n outcr-o[).; ~ : ~ p v c i , ~ l l \

so11L1i o f blui-o. They a r e l u s Liwus, t l c~ i sc l y I r ac tu i -c t l ( b ' i ( 1 . 0) . a11t1 oILeri wenLlicred Lo b o u l d e r s wiLh s h a r p edges .

F i g . 5. F o l d i n g i n m i c a - r i c h DIP', west of Muro ICasa. l i g h t bands: q u a r t z i t e , d a r k bands: haema-tite ( - t - r n a y n e t i t e ) 4- mica.

b F i g . 6 . 'Massive' D I P w i t h dense fracturing, east o f Chekuywari.

'I'lic? sequence i s capped by a l a y e r uC' the ul,pc?r 111ii:n :-:i:lhi::( ,

vat-io11sl.y r e f e r r e d .to as p h y l l i t e ( ~ o ~ b o e t a%. , 101) 1 ) o l 1111:; 1 . 1 ; 1 i :

s c h i s t ( ~ n a g i i a e t al., 1984). I t is tile most ros-Lric:~ i . v c i 1 1

occttrrelicc arid c rops ou t on ly i n a narrow v a l l e y a1 I.1ir: L o l ) c ) I

Llre hluro h i l l . It i s t h i n l y laminated, l.igIiL grccli Lo ye1 l . o w i :- : I1

i i i co lou r , and l u s t r o u s where weaLhered. The lam iliac .11 c I'l , l l I i 1 1

atid on ly dcfor~tied by i r r e g u l a r q u a r l x i t e ve ins atid pods. 1 L i::

l i ighly weathered and f r e s h samples are d i f f i c u l t t o ob la in .

Nitlor r h y o l i t e and d o l e r i t e i n t r u s i v e s occur r~iosl ly as

rlyhes. The dykes a r e t h i n , i r r e g u l a r arid h igh ly weal l i~rc t l . T l i t ~ ~

a r e derisc o r p o r p h y r i t i c . A l i g h t grey p o r p h y r i t i c r l iyol j Le d>Lc

j s Iountl abouL 1.5 hn sou th of Ncw Kulo, ntid is alicgt~ccl j i i a

NE-SW d i r e c t i o n . A t Cadabuke, and n o r t h of Kudu, d o l e r i LC dyhrss

in-Lrude i n t o t h e b a s a l m i c a s c h i s t and g r a n i t e giieiss. Tl~cjr .

widths range from 50 crn t o 5 m and they are wealhcred l o l a ~ . r j o

boulders .

2.3 Petrography

For t h e pe t rog raph ic f e a t u r e s , e s p e c i a l l y tile ~r r ic ros l ruc I.c~l-(3s.

mineralogy, and modal compositiori, t h e rock types arc d iv i 11crl i I I L O

mineralogical subc lasses . The i r mineral compos i t io~is a r e rc; i v e r ~

i n Tables 1 and 2.

r1 ,., . 1 (;rnnite yiciss -- Tlijs is essentially quartz-feLdspar-!jar~leL g i ~ c ~ i s s ~ L I I ~ I

c - o~ i l i l i~ i s q inrLz , mic roc l ine , b i o t i t e , p l a g i o c l a s e ti - A i l ) , 11 I '1 7

I I I I I H C O V ~ ~ C , mid ga rne t able 1). It i s meili~ui~ g ra ined , a ~ l d \wl l

i o l i a t e d i l l t h i n secLion. QuarLx, nricroclirie, and placjioc l nsrl arc.

t l ~ c main f e l s i c components c o n s t i t u t i n g 40$, 2&.67/U, arid I9.U,$ ol' I l l ( .

roc:l\ by voliulie able 2 ) , r e s p e c t i v e l y . Tlie quarLa < j r a j i ~ s

c o n s i s t of nm. l i un r grained p o i k i l o b l a s t i c xenob la s t s , and f i l i e ,

su l ) l~ed ra l c r y s t a l s . Microc l ine is p r e s e ~ i t as 111ediu111 grniticcl

p c r l i ~ i t e s o r f i n e g ra ined p r i s n ~ a t i c i d i o b l a s t s . Some of L l ~ e i d i o -

!)I n u t s have wcll formed po lysyn thc t i c twins. Placjioclnse c r y > l a ls

a r e lnaiiil y andes ine ( ~ n - An ) , p o l y s y n t h e t i c a l l y twi rmed arid 4 1 47

c l ~ v c l op sutur.ed o r uneven r e a c t i o n boundaries whcre 111r.y i 11 Lr.1.c 1 1 OIV

wi 111 q u a r t z g ra in s .

U i o L i L e , t h e main rmf i c cooiponent, occurs as su1)llctlr-aL 1)LnLc.:;

c l o s e t o one ano the r i n t h i n f o l i a e , o r are d i s c r e t e l y ali<lried.

Yolne of t h e p l a t e s , e s p e c i a l l y i n t h e I o l i a e o r b i o t i t e (mica)

bards c o n t a i n mamillated opaque mine ra l s (probably i r o n oxide) .

Uio Li te gra i i i s c o n s t i t u t e more t han 9.07h of t h e n ~ i ~ ~ e r a l s p iwsc i~ t

able 2) . A few t h i n p l a t e s of muscovite, aud s o m ~ t i m c s

s e r i c i t i c a l t e r a t i o n a l s o occur c l o s e t o t h e b i o t i t e . Orthoclase

g r a i n s w i t h i r r e g u l a r o u t l i n e s , and subhedral garne t porphyro-

b l a s t s are accessory . The ga rne t po rphyrob la s t s are l i i y l ~ l y

f r a c tu red a i d poikiloblss t ic.

Tnlllc 1: Sulmnry or P1i11cral Assemblages i n Itocks Sludic!cl -- -- - - - - - - - -

(;r-n~ii te G n e i s s

1Jiotit.e S c h i s t

Muscovi t e S c h i s t

Cal .ci te Marble

Banded i r o n

F o l i a t e d Q u a r t z i t e

N ~ I I - f o l i a t e d Q u a r t z i t e

KEY

Qtz = Quartz

B t t = B i o t i t e

Plus = Muscovite

Chl = C h l o r i t e

Ser = S e r i c i t e

= C a l c i t e

Play = P l a g i o c l ~ a s e

Gn = Garnet.

xxx = very a l ) i ~ t ~ c l a ~ ~ t

xx = abundant

x = n~oderate

ac = a c c e s s o r y

- - - a b s e n t .

I & '

N cr Granite O 1 & 2 C V +- \t -F cr \O Gneiss > 1 P 1 . I . I . 4

1 3 r C C C IL‘ 0 Ll 0 E! 0 c j c L1 L.7 c 0 0 0 d '7

- - - -. .- -- _ - P c 0' C- ~ - i Quartz + ID / p i " p I c . N . ? ? I o Biotite + Yus- g I & C 0 4 W 9 \O 0 ( X i N a o G o o o 8 covite schist^ - - -

*--Xuit-2-+- K u- 0 r G 0 Biotite + 0

I I . I I 0 \O

0 i o to N \O w

0 0 0 0 $ ;Garnet schistg i o 0 0 0

Qiiartz + II: W

O U C3 CJ Muscovite +

I I I . . I I \Biotite + I-. 8 0 0 t3

o G o o (Chlorite 2 - ----- -- ~ ~ c c S i s L . -

h

! g -J P Kon-foliated + N . I I . I I I I I Q~artzite r C

0 % c' c' 3 ' .a u c.

-- . - - -- - - - - - -. - - V

LI

C CI c h o N C C- LJ u o 2 ' Foliated

I * e I I I I ' C J L wi -J o * I Quartzite 3 I G =: z 3 L n bl -- -- -- -- O i - F

+ I r ~ - Quartz + 9 u rd c c C haemat i t e a

I I I I b i b : b +- u o 'f! schist ili C +- G C Ul 4

?

-- - - -- -- --- - - - --- c - , p Q ~ a r ~ z A c

i C. G b r - r .: LI w k' haematite D +

I 9 I - C I I I 0 r:

s C? C .s b r

C mica schist Ll b b \= -.I - C

---- -- -- -- - - - - --- - - - -- -- - - Calc-

( < I ) Iliot i te s c h i s t

'I'l~c. L)iot.j.te s c h i s t , c o i ~ s i s t s o f two p e t r o g r a p h i c sul )c lasse : - ,

~ r ; t r u t ~ l y ; 1. q u a r t z t b i o t i t e + muscov i t e s c l l i s t a n d , 2. q u a r l a I

L i i o l i t e i- gar i l c t s c h i s t . I n q u a r t z + bioLiLe -t- ~ i i u s c o v i l e , n~lcl

q11a1-lz + b i o t i l e -k g a r n e t s c h i s t s , t h e doniinaril m i n e r a l s are

1 l 1 1 a l . i ~ c l ~ i c l b i o t i t e (?!able 1). Q u a r t z i s bimodal , c o ~ n p r - i s i i ~ q

I I I P ~ ~ I I ~ I I graixied mosaic arid f i n e g r a i n e d r e c r y s t a l l i . z e d m o r t a r s .

'I'trc ~ u o r t a r s sui-1-ourid t h e nicdiurn g r a i n e d mosaics . U i o L i i c i s

p l a t y , co r r~pr i s ing o f m a t t e d f l a k e s a n d f i ~ ~ e s u b i d i o b l n s l i c pl-atc?:~.

7 '11~ 1) Lakes are u n i f o r ~ r l y a l i g n e d , d e f i n i n g a good lep%clol ) l :~s l ; ic

I cs tu t -c . O t h e r m i n e r a l s s u c h as ~ n i c r o c l i n e , p l a g i o c l nse ( ~ n - 7

1\11 ) , ~rruscovi Le and c h l o r i t e , a r e minor co r i s t i -Luer~ t s ( ' l h l , l e s , 1 I 0

a i d 3). P l i c r o c l i n e o c c u r s as s u b h e d r a l p io lc i l o b l a s t s wh ic-h Ilavc?

i ~ l c l ~ r s i o ~ i s o f f i n e q u a r t z , mica c r y s t a l s a ~ i d opaque nrillcr.als.

l ' l r ig ioclase is a l b i t i c ( ~ n - At1 ) and h a s p o o r l y tlevelopctl 7 10

p o l y s y ~ l t h e t i c t w i l l s . Pluscovite and c h l o r j t e f l a k e s occrlj' w i L l i

b i o t i t e i n t h e m i c a bands. b

The p r e s e n c e o f c o a r s e t o r~iediuu~ gi.ai11ed y a r n e l c r y s L o l s

i n the q u a r t z + b i o t i t e + g a r n e t s c h i s t , a11t1 .ils s t r - o ~ l y e r f o l . i a L i o n

2'7

111a1\e i t d i f f e r e n t from t h e q u a r t z + b i o k i t e i ~ ~ ~ u s c o v i Le s c l i i s l .

Ttic y n r ~ ~ e t c r y s t a l s are f r a c t u r e d , p o i k i l o b l a s t i c and e~~~l~cc l t l e t l i l l

111aLrix o f q u a r t z a n d micas.

( I , ) , \ luscovi t c s c l l i s t

T h i s is main ly a q u a r t z + muscov i t e + b i o t i t e + c h l o r i t e

s c l l i s t . 1 L c o n s i s t s essentially o f q t ~ n r t z and muscovi L c . c r y s t a l s .

The rnuscovite c o n s t i t u t e s an a v e r a g e o f 38'6 o f t h e m i n e r a l co l i t en t

and c o m p r i s e s of t h i n f l a k e s which are n o t s t r o n g l y f o l i a t e d . A

f e w secondary muscov i t e c r y s t a l s o c c u r as s u b h e d r a l p r i s m s a ~ l d

nr-e d i s p e r s e d w i t h c h l o r i t e i n q u a r t z r i c h zones . Q u a r t z ex i s1 . s

as e q u i g r a i i u l a r nlosaic o r a n h e d r a l g r a i n s i n a m a t r i x o f q u a r t ;., ,

c l r l o r i te , atid s e c o u d a r y nluscovite. Accessory b i o L i Le, s ~ ~ l ) l ~ o t l l - a l

mid reediiua y r a i n e d c h l o r i t e c r y s t a l s are found i l l s o ~ ~ ~ c s i m l ) l e s .

Sl. t .n~lds o f opaque m i n e r a l s ( ~ r o b a b l ~ o c c u r i l l Lllo

clt~;rrt..r.-mica n ~ a t r i x o r a l o n g muscov i t e bands.

Two main v a r i e t i e s , r ian~ely ; f o l i a t e d arid nor i - fo l i a t c d

q u a i 7 L z i t e s o c c u r i n t h e s t u d y area.

F o l i a t e d q u a r t z i t e (a) ------..---

T h i s c o ~ i s i s t s e s s e n t i a l l y o f q u a r t z a n d c h l o r i t e . I L i.s

I I I C ~ ~ I I I I I t o f i n e g r a i n e d arid s t r o n g l y f o l i a t e d . It conl:n.i.~is

28

y r a t ~ o b l a s l i c q u a r t z mosaics s e p a r a t e d by t h i n Lmnds o f c h l o r i l e

and n ~ u s c o v i t e . The q u a r t z g r a i n s a r e h i g h l y f r a c t u r e d atrd Lurl)icl,

bu t do n o t c o n t a i n d u s t t r a i l s o r secondary growth s t r u c t u r e s .

C h l o r i t e i s abundant and c o n s t i t u t e s abou t 13.57: o f t h e

m i n e r a l c o u t e n t able, 2) . It is f i n e g r a i n e d , p l a t y arid l e p i -

c l o l ~ l a s t i c . The l e p i d o b l a s t s are c l o s e t o one a n o t h e r i l l L11 i11

T o J i a e o r are d i s p e r s e d i n q u a r t z mat r ix . T h i n rl~uscov iLc r r - y s l n I-;

are also round i n t h e c h l o r i t e f o l i a e .

(1,) Noti- FoliaLed q u a r t z i t e

T h i s a p p e a r s c r y p t o c r y s t a l l i n e m a c r o s c o p i c a l l y a i ~ d Iinvv

c.c,r~choitlal I r a c t u r e . I n t h i n s e c t i o n , i t c o n s i s L s o C arcrl i u 1 1 1 ,

1 ~ ~ 1 y g o ~ i a l q u a r t z g r a i n s t h a t have e q u i g r a n u l a r g r n n o l ~ l a s l i c

t e x t u r e and c o n s t i t u t e a n average modal c o n t e n t o f 8S).2':0 ('l'abl e , 2 ) .

'l'iliy c l i l o r i l e g r a i n s and opaque m i n e r a l s a r e Touncl i l l Ll~e q u a r l z

2 . 2 lhildcd I r o n Format ioli

T h i s r o c k group is d i v i d e d i n t o two p e t r o y r a p h i c ~ t 1 1 ) c l u : i ~ c . q ~

11;111icl y ; (a) banded q u a r t z + h a e m a t i t e ( j ~ n n g r ~ e L i t c ) scli i s L E o ~ ~ l ~ c ~ t l

114. Ll~c t l~ass ive a ~ ~ d mica-poor 131F aurl ( b ) ba~ided riunr-Lx I 11;rrwal i l ( s !

11111,qcovitc s c h i s t forrr~ed by t h e mica- r i ch H I F '

, ( 0 1 l ln~ided Quartz + i i a m l a t i t c (2 ningrreti te) schist - - - - -- -

Tliis c o n s i s t s o f e q u i g r a n u l a r q~ra r l s s sepnraletl 1)s S L I nrr~l:;

01' tilassivc h a e i m t i t e arid r a r e l y mayneti tc? ( P i g . 7 ) . Tlie c111n1-LA

F i g . 7. F l ic robanding i n Q u a r t z + h a e m a t i t e (i t ~ i ~ y i ~ e i , i ~ e ) s c , l ~ i s I : d e f i n e d by i r r e g u l a r n~asses of h a e m a t i t e ( 2 magnc t i t e ) - d a r k bands and q u a r t z - r i c h matrices - l i g h t b a ~ l d s .

30

matrix occasionally contain thin plates of biotite and muscovite.

(b) Banded Quartz + haematite + muscovite schist

This is similar to the banded quartz + haematite (5 magnetite)

schist except that the former is less well foliated, and the hae-

matite strands are richer in muscovite flakes. The quartz grains

are cloudy and fractured.

2.2.5 Marble

The marble units in the map area vary from calcite + mica

marble to calcite marble. The calcite + mica marble commonly

referred to as calc-silicate (odeyemi, 1976, Rahaman 1976a)

consists of prismatic calcite, quartz, and lepidoblastic biotite,

muscovite and chlorite crystals. It is medium grained and strongly

foliated. The calcite grains are medium grained and vary between

0.1 mm and 0.5 mm. Quartz is fine to medium grained, but coarser

ones often wedging apart mica bands, have secondary enlargement

and represent quartz pods.

The calcite marble is medium to fine grained, and contain

predominantly calcite crystals. Calcite is bimodal comprising;

fine, equigranular mortars enclosing coarse-grained mosaics. These

mosaics also contain medium grained anhedral quartz crystals.

Biotite, muscovite and chlorite are accessory p able, 2 ) a n d

31.

are dispersed in quartz-calcite matrix. Mineralogic analysis

able, 3) shows that only a few dolomite crystals occur in the

marble.

2.2.6 Intrusives

The light grey porphyritic rhyolite consists of a few

plagioclase ( ~ n - An ) and orthoclase phenocrysts embedded 35 37

in a groundmass of plagioclase crystallites and fine grained

quartz crystals. The phenocrysts constitute about 5% of the rock.

The dark green dense dolerite consists of a matrix of fine

plagioclase ( ~ n - k n ) , pyroxene, hornblende with sizes 42 47

LO.l mrn and a few coarse crystals of pyroxene. Anhedral grains

of magnetite are also found scattered in the matrix.

2.3 Structures

Structural elements such as folds, faults, joints or

fractures, lineation and foliation are well developed and preserved

in the rocks studied. They are briefly described below.

2.3.1 Folds

The occurrence of rock units in the study area (Pig. 3)

indicates major folding. The folds are mainly isoclinal with the L

0 fold axes in the NF,-SW direction and a plunge at about 15 azimuth.

The NE-SIJ axial trend is similar to those in other parl:s of the

32

Table 3. Stain Characteristics (in Lemberg solution) of Some Carbonate Rocks From Study Area.

Sample

TM-2

TM-5

TM-7

TM- 10

TM- 15

TM-$7

TM-22

TM-23

TM-24

Thin Section

Colourless

Grey

Banded

Colourless

Colourless

Colourless

Colourless

Grey

Banded

Stain Section

--

Inner part brownish

Unstained

Partly stained

Yellowish brown

Yellowish brown

Yellowish brown

light brown

Yellowish brown

Deep brown

-- - Rock Group

Calcite marble

dolomite marble

dolomitic marble

calcite marble

calcite marble

calcite marble

calcite marble

calcite marble

calcite marble

33

Nigerian Basement Complex. Rahaman (1976a), McCurry (1976)~ and

Odeyemi (1976) suggested that this general N-S fold trends is

related to the second folding phase of the Pan-African orogeny.

The structures of the first folding phase they observed are

essentially E-W directed. The isoclinal folds have westerly - 0

dip whose angles range from 20 to 81°.

Minor or microfolds ( ~ i ~ . 5) are well developed in the

mica-rich BIF and in mica schists. They are simpl.e, open or

tight m~crocrenulations similar to classes IB or IC buckle folds

described by Rast (1964) and Boit (1965).

2.3.2 Faults

Fault zones are identified on the limbs of the major folds

as shown in Fig. 3. Earlier workers, for example, Nnagha et al.

(1984) recognised three sets of faults, comprising; (a) NE-SW

strike slip faults, (b) NW-SE cross-cutting faults perpendicular or

nearly so to the limb strikes and (c) E-W fault planes. The NW-SE

faults are well developed and have displacements of more than

15 m, especially in BXF. The other types of faults are less well

developed.

2.3.3 Joints

b

The joints consist of regular and irregular openings.

They occur in sets which are concordant or discortlnnt wj I h Imnding

3 '1

o r f o l i a t i o n i n t h e r o c k s ; a n d sonletilnes con , juyate . Sortw arc? lw111 ,

i r i -cv ju lnr o r wavy am1 are similar t o prec leforn la t i olml c.rxcks

tle.;cribed b y Ilead arid Watson (1968) a ~ i d l l i l l s ( I yp ) . ' I ' l~ase it1 (.

t orr~~~loii i n t h e g r a n i t e g n e i s s a n d mica s c h i s t atid arr J'i I Ii.[1 wi l 1 1

( l i ~ I ; i / s e g 1 ~ g a 1 i o n . s arid v e i n s . O t h e r s liave r eg r t l a r ctl~lcv:, t l ~ l i -

c I c.11 t i r r qtlal-lx v e i n s a n d r e s e m b l e pos tde Io r~mat io i rn1 i r lc . i j t i cbtr 1

>lic.nr k a c t u r e s d e s c r i b e d by U o i t (1961). T h e s e arc pr (:tlolei~r,rlll

i l l ~ u a r b l e , DIP a n d some m i c a s c h i s t s .

The c o n j u g a t e j o i n t s are formed by i ~ ~ t c r s e c t i r ~ g co~~coi- t lal i l .

aiitl d i s c o r d a r i t j o i n t sets and are w e l l d e v e l o p e d i r~ t h e 11IlL 'l'hle

n u ~ n c r o u s c o n j u g a t e j o i n t s e t s i n t h e O I F enhance bLock d i s i n t . c -

51'-atinn and r o r t n a t i o n o f l a r g e b o u l d e r s on t h e r o c k .

In ~ i i i c a s c h i s t , f o l i a t e d q u a r t z i t e , c a l c - s i l i c a l e and 1JIF

pln1.p e l i n e r a l s s u c h as b i o t i t e , m u s c o v i t e , a n d c h l o r i l;e a r e

n l ig l ied , g c i i e r a l l y i n a NE-SW direcl ; i .on (F ig . 8 ) . A f e w of Ch~sr?

wicn p l a t e s d e v i a t e , c r o s s - c u t t i n g t h e o t h e r s aiid lor-rrrinij ilhtar-

l o c k illg rlleshes.

2.3.5 F o l i a t i o n

' Pli i ier*alogic s e g r e g a t i o n i s collinlori i n t h e mica ~ c l i i s t . ,

ca l c - a i l i c a l e , barided g r a n i t e g n e i s s , a n d 111 1p. P a r a l l e l a l ~ ~ I I I I I ( ~ I I ~

oS b i o t i t e , m u s c o v i t e a n d c h l o r i t e p l a L c s i l l d a r k ba~~c l r ; o r f o l i a e

FIG. 8. Rose diagrams showlng t ren foliation in the study area

s(.l),~l'nLcd I)y l i g h t bands o f q u a r t z , m i c r o c l i n e , pi , ~ y i o c . l nqr: n ~ ~ r l

oLllc.r I e l s i c ~ n i u e r a l s i s f a i r l y w e l l developed. In c~ua~- i , z I

I lnP~nnti lc (k m a g n e t i t e ) s c h i s t , t h e da rk bands a r e made ui) of

hao111aLit.e a i d m a g n e t i t e , and t h e l i g h t ones o f e s s e l l l i a l l y q ~ m r l z

i 7 The bands o r f o l i a e t r e n d NE-SW and have A Z ~ I I I ~ I ( l i

0 0 v n l u c s bcLweeli 5 and 110 1 8) A few are however dirc.ctctl

0 t o llle Nhr-SE and have azimuth v a l u e s between 345 and 3 ~ 0 ~ . ' l ' l ~ i s

l a t t e r group is more conmori i n t h e q u a r t z + ~r luscov i te I- c h l o r i l e

s c l l i s t . Some o f t h e f o l i a e a r e f o l d e d i n t o NW-Sli; K i ~ i k - I o l d s

c l x l o s e d i n NNE-SSW S - f o l d s ,

CHAPTER THREE

MINERAL DEPOSITS

The mineral deposits of the study area are iron formation

and marble.

3.1 Iron Formation

The iron formation in the study area is represented by the

BIF. The mode of occurrence of the deposit is described based on

data obtained during field surveys. Only the major element

geochemistry is discussed.

3.3.1 Mode of occurrence

BIF occurs as a middle layer between an upper non-foliated,

and a lower foliated quartzite on the slopes of the Muro hill and

west of Soka. It occurs as extensive, slightly continuous and

discontinuous layers or lenses embedded in either the foliated or

the non-foliated quartzite.

Three main occurrences crop out on the western, eastern

slopes of the Muro hill, and at the centre of a low-lying ridge

west of Soka village. These occurrences will be referred to as

M-1, M-2 and S-1 ore bodies respectively in subsequent description.

. The M-1 ore body is a relatively thick layer extending

from south of Muro to Chekugwari. It extends for more than 5 l a 1

0 0 al.ong the strike and dips at 40 to 5 4 W. The ;tpl~n ,-en? i l\i c:!:lle.;:;

along the dip varies from 15 m near Muro to)150 m in Chekugwari

area. The ore body is highly fractured especially in the south

and forms variously sized boulders which cover the surface of

most of its outcrops.

The M-2 ore body is a discontinuous, irregular bed cropping

out on the eastern slope of the Muro hill, with a N-S strike. It

extends for about 10 km and the thickness is betweenL4m and 10m,

It is thickest in the north, near Muro Kasa, where it is mica-

rich and complexly folded. It disappears southwards, reappearing

near Obugu as thin mica-deficient banded ore. The bed is

disrupted in places by the NW-SE trending cross-cutting faults

(cf. section 2.3.2) which have displacements up to 15m. The ore

0 body dips westerly at about 32O to 43 , and is generally steeper

southwards,

The S-1 ore body which occurs at the northern edge of Tondo

hill, west of Soka is the smallest of the ore bodies. It is

branched at the centre, and traceable for more than 500m along

the strike. The ore body has a width between 0.75111 and 1.2m, and

0 dips westerly at about 36 .

The three ore bodies are suspected to be connected, and

probably form a single iron-rich bed folded into series of homo- a

clines. Each of the bodies could be a surface expression of an

eroded fold limb as indicated in Fig. 3.

3.1.2 Mineralogical types

Two main mineralogical types occur in the BIF deposit.

They are haeinatite-rich ores and magnetite-rich ores. The

haematite-rich ores are dominant in M-1 and S-1 ore bodies.

In these ores, haematite occurs as irregular strands in thin

or thick iron-rich bands and constitute between 46 and 59 volume

per cent(vol.O/o) of the ores. The gangue minerals, essentially

quartz make up the remaining 41 to 56vo1.%. The haematite-rich

ores yield an average total iron content of about 30% and

average sIlice content of nearly 5096. These ores are commonly

fine to medium grained.

The magnetite-rich ores predominate in the M-2 ore body.

Magnetite occurs aa fine grains or grey patches in the ores.

Mineralogical analyses show that magnetite constitute only a

small proportion of the ores, mostly between 6 and 7 vol.%

Haematite occurs in some of these samples and may reach up to

45vol%, but in others it is entirely absent. The gangue minerals

determined as quartz vary between -48~01.96 in those containing

haematite to more than 90vol.% in the ores containing mainly

magnetite. The magnetite-rich ores yield average total iron

content of about 33% and average silica, approximately 5 1%. b

3.1.3 Geochemistry --

oxides. Sulphur was also determined.

(a) Analytical methods

Whole-rock chemical analyses were conducted on the samples.

SiO A1 0 2' 237P205

, and Fe 0 were determined by ultraviolet 2 3

spectrophotometry. Atomic absorption spectrophotometry was used

for Ti0 and MnO. Na 0 and K 0 were determined by fl.ame photo- 2 2 2

metric method. CaO and MgO were obtained using EDTA complexo-

metry. Ferrous iron ores was determined by potassium dichromate

titrimetry, while total sulphur was obtained by the gravimetric

method. Loss on ignition (LOI) was determined by direct

0 combustion at a temperature of 1000 C. The details of sample

preparation and analytical procedures are given in appendices

I and 11, respectively.

(b) Results of Analysis of BIF

The results of the chemical analysis of M u m BIF is given

in Table 4. A total. of s i x samples; four of the M-1 ores and

two of the M-2 ores were analysed. Samples TM-lA, TM-2A, TM-3A

and TM-6A represent the M-1, whereas TM-&A, TM-7A are samples of

the M-2 ore. The total weight percentages obtained range from

97.75 to 100.06. The values of LO1 represent the volatile

components, essentially H 0 and CO The ratio of the oxidation 2 2

2 + state of iron (l?e3+/J?e I,, ~n/J?e total, and P/Fe .Lotal ratios,

were calcul.a.ted to the nearest two place.'; o-T ilccit~~al. f ~ ~ i p c ~ l ( l i . x 1"T-r) ,

4 1

Table k. Chemical Analysis ol Tidorr Ores 1'1-om Pluro I1.i 118, Nigeria.

I

Ox i tle i TM-1A

Analysis carried out at Metallurgical Testing Laboratory, National Steel Council, Jos.

*Conducted at Project Developinen t Institute (1'1101)~) , Enugir.

Tor L l ~ e Fluro UlIz (1-6) , o t h e r Nigerian i r o n o r e s ( t h c 1 Lukpc?

1 1 i 1 1 o r e s (7-16) , Agbaja (17-21) and Enugu (22-25) i rw t~s lo~~e : ; )

and some s e l e c t e d DIF d e p o s i t s (26-601, us ing a UHC niini-con~prltct.

1111 I L x v a j l a l ~ l c a t t h e Cer~Lre f o r Energy ! , fcsenrcl~ niitl I)c:vn l olullc.rl l ,

1111 LVCI-si Ly 01' Nige r i a , Nsuklta.

'She r e ~ u l t s o b t a i l ~ e d from t h e Fluro 1311; a r e con~pnrc?d wj ( 1 1

11ul?lislrcd d a t a on I t akpe h i 1 1 o r e s lade, 2078) , Acjlm,i;i i r x ~ ~ ~ -

stor~es ones, 1955) and Enugu i r o n s t o n e s (l lazel , 1057) , ?'al,lc.::

5 , 6 and 7 , r e s p e c t i v e l y . They a r e a l s o co~nparecl w i t 1 1 sollle

o t k ~ e r known l3IF d e p o s i t s from t h e U ~ ~ i t e d S l a t e s o f America,

Western A u s t r a l i a , SouLhern Af r i ca and o t h e r p a r t s 01 t h e world

able, 8). The composi t ional v a r i a t i o n s between t h e Muro

HI17 and some o f t h e o t h e r Niger ian i r o n o r e s are compared

g r a p h i c a l l y by t h e James' (lcj54X ~ l - S i - b ' e ( I Mli) dinyrarn (rig. 9 ) .

43

' 5. Cl~clhicnl Analysis of I t d c p e llill It-011 O r e s , N i ( j c ' t . i a (from Olade, 1978).

L

T i 0 2

"',3

I,'e?O Y 3

MnO

blgO

CaO

Na 0 2

K20

P 0 2 5

TOTAL

h5

Table 7. Chernical Analysis of Enugu Ironstones, N. iyer in (from Hazel, 1955)

Oxide

SiOq LI

Ti0 2

A1 0 2 3

"e203

PlnO

[ ) 0 2 5

m1

loo. 14 roo. 4.2 - - - - I --

N 2 , N 5 , N ~ u = Samples from boreholes No. 2 , 5 , and 8 U i n Nsude-Obio~aa area.

' A 9 = Sample from borehole No. 9 at Aboh.

J b i , ln111p f ! . Cl1e111ico1 A~rolysee of Selected U1F from U n i t e d S t a l e s of hllctaico ( A & c ) ,

1Jestcr.rl Australia ( u ) , Southern Africa (1)) and MKS-IF {E)

:s

tG.82 45.84

0.08 0.04

2.00 0.83

11.3k 20.24

20.47 18.91

0.59 0.69

3.00 2.713

2.78 1.99

0.06 0.05

0.27 0.14

0.15 0.07

2.54 1.71

9.49 6.67

2.33 1.63

rid rid

, -. -- - - 19-30 99-78 --

A.12 28.60

0.50 0.N I

0.02j 0.05

- . . A ( I I I C I I I ~ ~ composi . -

Lower ' lover 'upper c ler ty I s l a t y chert

14.52 -21.20 i 0.12 lld

0.54 0.08

1.83 16.15

(4.92 34.82

1.86 1.43

2-13 7.97

0.55 0.69

0.02 0.04

0.20 0.01

0.20 0.37

0.13 2.12

32.05 15.50

- - 0.72 0.03

0.54

2.49

1.66

0.04

0.10

0.07

1.50

5-67

1.50

rid

- 19.60 - -.

r9.77 1.14

0.01

Table 8 C o n t d . 'I ;

- .-

~ L O ,

Ti0

A! o 2 3

Fc 0 2 3

FcO

!In0

CaO

s0,o K 0

'z05 1i20*

C02 LIO

S

Sources: ( A ) Lepp. 11. 1966. (D) C o l e . H.J. 1981, ( C ) O a y l e y . R.W. and Jwwu, H.L. 1973, (u) Lleukes, N.J. 1973, (E) K i m b e r l s y , H.H. 1979.

f 0 \ 0 Muro - / o Itakpe \ n Agbaja

BIF ores

iron ore

iron ores

FIG. 9 . A1 - Si - Fe (t Mn) relationship In iron ore samples from Muro, Itakpe and Agbaja iron mineral deposits

in Nigeria :

Table 4 shows t h a t t h e bulk of t h e Muro UIF corr~priscs iro11

, ~ [ 1 1 1 s i l i c a (43.12 t o 55.78yh). These c o n s t i t u t e more t h n ~ i 30'$

01' Llie ores . The i r o n oxides abundances a r e consiclcral~ I. y 11ig11

ai~t l { j i v e 1;otal i r o n con ten t s of between 29.59 and 36.72'$ (l'at>l.e, 1 1 ) .

Thcse a r e w i t h i n t h e ranges 15 t o /k2$1 Fe (0' rourke 1963 ; TrcndaLI ,

19G8), and 25 t o 3 5 0 e (park and Mcdiarmid, 2975), c h a r a c t e r i s t i c

of BIZ: d e p o s i t s i n most p a r t s of t h e world. They a r e a l s o c l o s e

Lo t h e average of 30 t o 35% Fe f o r oxide f a c i e s , and higlier t h a ~ r

t h e 25 t o 303/0 Fe suggested f o r i r o n formation belonging t o t h e

carbonate o r s i l i c a t e f a c i e s (James and Sirns, 1973).

The i r o n oxides a r e h igher i n t h e f e r r o u s s t a t e than t h e

f e r r i c s t a t e . Th i s would suggest an abundance of magnet i te

( r e 0 ) over haernatite ( ~ e 0 ) i n t h e oxide f a c i e s , and c o n t r a s t 3 4 2 3

wi th t h e poor t o non-magnetic c h a r a c t e r of t h e o r e s , a s wel.1

a s t h e preponderance o f h a e ~ n a t i t e observed i n thi.11 .recLiot~s.

Also t h e .Low grade of metaniorpliism, ranging from c h l o r i t c ~ t o

Lowel.. y a r ~ l e L zones i n t h e g reensch i s t f a c i e s , ~ O I I I ~ I I : ~ I I L i.11 l l i ~

I i grade I I E tcunorphism and c h a r a c t c r i s e d by greaLer v o l call i : 111

liae~iia t i t e magnet i te

sr~g!rested by lluber (1958). Tlie more dominant of t h e r e a c t i o n s

would depend on t h e mobile phase ( 1 1 o r CO) which is p reva l en t 2

du1.i iiy ri~etcuiiorphisin, Sollie workers, such a s Cuniberl i d g e a ~ i d

SLoiie (19G4) disagreed w i t h t h i s nietairiorpliic o r i y i ~ i of IiliylieliLc,

s t a t i n g t h a t r eg iona l metamorphism does riot a l ter tlie oxi dat i ~ I I

s t a t e of o r i g i n a l minerals . Th i s a s s e r t i o n does ~ i o t oil i ts own

ho ld as i t has been shown t h a t te inperature dependelit reac t io r i s

a r f c c t t h e o x i d a t i o n state of mine ra l s , e s p e c i a l l y irori ~iiilier-als.

Ulindley and Youell (1953) showed t h a t i n chamosi t ic rocks ,

2.1- 34- p a r t i a l ox ida t ion o f Fe t o Fe is accompanied by dehydra t ion

0 upon hea t ing t o 300 C. Again, F r o s t (1979) showed Lhat i n oxygen

bu f f e r ed Fe-Si-0-H system, which is H 0 f r e e , t h e fol lowing 2

r e a c t i o n s are important at high tempera ture ,

( a ) 4 Fe 0 3 4 .+ O2 > 6 F e O 2 3

magnet i te vapour haemat i t e

F a y a l i t e vapour magnet i te quar.tz.

Tiit-se r e c l c t i o ~ i s show Lhat botli ~ u a g l i e t i l e n11d t ~ a e m a t i i e c o ~ ~ l t l

r e s u l t fro111 t e m p e r a t u r e d e p e t ~ d e t ~ t react i o n s . The p r e s e n c e o r

a b s e n c e o f m a g n e t i t e i n 13IF d e p o s i l s is r a l h e r more deper ldet~t on

tlie c o m p o s i t i o n o f s o u r c e materials lllnn oli nioLal~lorphic trnns-

J 'or~nat ion . $lost Archean BlF, a s s o c iat .ed w i t h I ow yrntlc rnc. La-

nkorpliisl~~ as i l l t h e Y i l g a r n b l o c k o f Wester11 A u s t r a l i a ( C o l e , 19110,

1C)tJ I ) , tlie 11ru.eiersley r e g i o n o f Western A u s l r a l i a ('L'reritla l 1 illid

IJlocltcy, lc)70), t h e G u n f l i n t a r e a of Ca~iarla (Iclorarl a ~ l d I ' n p i l w ,

IO;'<) niid t h e M r b e t o n g r e e n s t o n e b e l t , s o f S o ~ ~ t h c ? r ~ ~ 111 r ic-n

( l h * ~ t l \ c > s , 1973) , c o n t a i n i n g l a r g e q u a ~ l t i t i e s o r volcatiic- I I I ~ ( c.r i a l ,.,

. \ I < \ Iiiglily cl l r ic l led i n niagiiet i le . I n sucll c l c p o s i t s , I I I ; I ( J I I < > ~ i ('

I cc:isociaLcd w i t h s i l i c a t e ~ n i r i e r a l s sucli as greerlaJ iLr1, - I i 11)-

I I O I I I C ' I a11c a11d ( ] r u n e r i t e . These 111i l le ra l s a1.e n o t present i ik I

~luro-I1[I;' d e p o s i t . The a s s o c i a t i o n i n t h e Iluro-DIF i s sin~i l n ~ ,

Lo I lwse found i n l a t e P r e c a r l ~ b r i a t ~ i ro r i for -mat ions of l j i l g r o u p ,

I l e g \ ~ i l m t s h i e l d , M a u r i t a n i a , d e s c r i b e d by 13ronner and Cliarivcl

( 3979) , a n d t h e Solcornan i r o n f o r w i t i o n i n C e n t r a l I,al~raclor 11 O I I < J ~ I ,

C . I I I ~ ~ ~ , I , d e s c r i b e d by Dimroth a n d Chauvel (1973). These h a v e r l l j t 11 - I a lo-

( 1 i c a 1 , a s s e ~ l ~ l ) l a y e s compr i s ing q u a r t z , haemat i Le, s i d e r i t e , a f e w

5 2

contents similar to that of the Muro-BIF. Although magnetite

may be present in some of these, haematite and siderite are more

important. Owen (1965) noted that magnetite occurs in sideritic

layer in some of the iron formations. Huber (1958) and James

(1966), suggested that siderite is an important primary mineral

in most iron formations. In metamorphosed deposits such as the

Dales gorge iron formation of Western Australia, described by

Ewers and Morris (1981), the Biwabik iron formation of Minnesota

Lepp, (19661, and other cherty iron formations described by Melnik and

Siroshtan, (i973), abundant siderite are in equilibrium with

magnetite and haematite. In these deposits, where haematite,

magnetite and siderite occur, siderite accounts for much of the

2+ Fe ions. Sideritic structures like pisolite, oolites, and

colliform structures have not been found in the Muro-BIF samples.

Suppose the initial iron mineral assemblage was rich in siderites,

some of these could have been converted to haematite and magnetite

as shown by the following reactions (Huber 1958):

(a) 2FeCO + H20 2. F e O +CO + 3 ---. 7 2 3 2

siderite water haematite

(b) 3 h2O3 + 2~' + 2e 1 2 Fe 0 + H20 - 7 3 4 haematite magnetite

.The loss of CO in equation (a), could explain the 2

+ 2H + 2e,

low values

obtained for LOI, as i.t was perhaps lost to the adjacent area where

5 3

larcje deposits of calcite occur. The water produced in equation

(b), may have formed the main fluid phase and was used for further

oxidation of siderite. The alteration of siderite to haematite

is likely to be increasing inwards from the surface, and thus

msking sideritic structures on surface samples. Also the haematite

produced may have shielded the magnetite occurring in the ores

and hence render most of the samples non-magnetic. Core samples

which would penetrate the deeper and fresher zones of the ores are

required for more conclusive evidence.

The silica content of the Muro-BIF, mostly 51%, is high.

It is comparable to 40 to 56% range for the MECS-IF, but much

greater than 40 to 5176, and 26 to 4% ranges for Montana region

iron formation of United States of America (Table, 8) and Itakpe

hill iron ores (Table 5), respectively. It is also far more

than the silica content of the Nigerian ironstones (~ables 6,

and 7). The relationship between the silica content of Muro-BIF

and the Nigerian ironstones is similar to that between MECS-IF

and SOCS-IF (sandy, clay, and oolitic, shallow inland sea iron

formation) described by Kimberley (1979). He noted that the

silica in the SOCS-IF never exceeds the ferriferoua minerals

(haematite, magnetite, siderite) unlike in the MECS-IF. This is

true for the Agbaja and Enugu ironstones which contain both sand and

clays (cf. Adeleye, 1976; Hazel, 19551, and possibly belong to the

54

SOCS-IF. The general lack of silica in ironstones has not been

well explained but it is believed that since most of them are

deposited as terminal clastics their silica were carried away and

deposited in environments that do not allow precipitation of iron.

The high content of silica in the Muro-BIF and most other BIF

deposits, suggests that their source materials were rich in both

silica and iron, and that both co-precipitated in their environment.

CaO is another important oxide in the Muro-BIF. Its content

ranges from 2.42 to 5.56%. This is comparatively higher than the

0.00 to 2.71%, O.B9 to 2.78% and 0.06 to 1.37% contents in the

MECS-IF, Biwabik iron famation, and Itakpe hill iron ores,

respectively. The high CaO content in the BIF contrasts with only

minor calcite crystals observed in the quartz matrices of the

samples studied. A large part of the CaO may have been contributed

by CaO substituting in the structures of iron carbonates (mostly

siderite) which may have been .present in the ores. This is further

substantiated by a similar abundance (1.41 to 3.64%) for the MgO,

contrary to only a minor dolomite -content in the adjacent marble

2+ Z+ deposit, and suggesting that both Ca and Mg occurred in the

precursors, but were mainly attached to the siderite structures.

The two ions have similar facilities to enter into crystal structures.

2+ 2 + Mason, (1966) shows that Ca and Mg , having atomic radii, 0.99,

0.66 and electronegativity1.0, 1.2, respectively could r r p l n c c

2 + F'e with atcrnic radius, 0.74, easily in its cl.ysl :,is.

'rhe nlnnga1lese c o n t e n t s , ob t a ined as MIIU are ! j c ~ c r . n L 1 y I trw ,

; i i ~ r l do I I O ~ exceed 0.070/0 except f o r sample T P I - ~ A whiclr has El110

tip Lo 0.4976. The manganese con ten t of t h e IIuro-llll? arc fa]- Icss

t l i a i ~ Lllose f o r most o t h e r UIFs cons idered (Table 8 ) ; Imt sii11.i ldl

t o t l ~ e r a l q c s 0.07 t o 0.17, 0.04 t o 0.076 and 0.03 Lo 0.0!l'j(1 1'1110,

1.ot111cl i n t h e I t akpe h i l l o r e s , Agbaja and Etiugu i r o n s t o ~ i e s ,

I-c:qwctivcly. They are a l s o comparable t o 0.05 t o 0.0tl"/:, El110

obta ined f o r lybo-Ora o l d e r g r a n i t e s S.W. Niger ia ( ~ a y o d c , 1976)

and 0.04 t o 0.1776 HnO f o r t h e Bauchi area o l d e r graniLcs - Uauchi LC...:

(L',i)orall, 1976). The s i n i i l a r i t y i n FlnO c o n t e n t s f o r both tlic

lrnseli~elit Co~r~plex rocks - t h e o l d e r g r a n i t e s and t h e U l F , a~ l t l Ll~c

yorlllger sediments - t h e i r o n s t o n e s , sugges t s t h a t t h e two I-oclc

gl 'ot~ps a r e r e l a t e d . The i r o n s t o n e s , as we l l as o t l~c i - ~ O I I I I I J s c \ t l i -

111c1lts i n Niger ia w e r e probably weathered from t h e Uasea~et~i: Cor11i)l e x

rocks a s suggested by Okeke (1983). The ~ n / l ~ e r a t i o s , vary.i..rlg

between 0.00 and 0.01 (Appendix 111) f o r t h e Muro-UIF a r e very

low. They are much less than t h e 0.025 average f o r t h e I'IECS-111'

( l~ imber ley , l 979 ) , and c o n t r a s t w i th high Mn contel i ts c h a r a c t c r i . ~ l. i c

of i r o n carbonate , s i l i c a t e and su lph ide f a c i e s of e a r l y Pro te ro-

z o i c I3IF (F rye r , 1977) and niost s i d e r i - t e s o f t h e PlECS-IF ( ~ i o i b e r l e ~ ,

1979). T h i s sugges t s t h a t t h e p recu r so r was riot de r ived frotn

P h i r i c h source such as bottom sea sediments which are not i n c o ~ ~ t a c t

wi th aimospheric oxygen during t h e Pro te rozoic .

The Pluro UIF has a r e l a t i v e l y low pl~osphorus conten t . Its

1 , range, beLwcen 0.17 and 0.37')&, is s i l r i i lar t o Llic 0.OI j - 5 t o 0.92): ralige f o r t h e l t a k p e h i l l o r e s (Olade, 1978: 'mbJ e 5)

al~t l l e s s than 1.3 t o 1-83;, 1.7 t o 3.07'& ranges f o r Agbajn

( Jo~lcs , 1955 ; Table 6 ) and Enugu i ro r~s to r i e s (Ilazel , 1955 ; T a l ~ l c

7 ) , ~ , e s p c c Lively. It i s , howevcr , r i c l ~ e r - tllali t11c 13 i w , i l , i l \ at~tl

~uost bKCS-21: cons idered (Table 8) . The d i f f e r e n c e s I)ctwecr~ Llir

plitrspliorous c o n t e n t s of t h e UIF d c p o s i l s and t h e ir-orrs(o~rc.:;

a1.c c l i a r a c t e r i s t i c and a g r e e w i th James I (1966) observa l::ior~ Llia 1.

t h e a b u ~ ~ d a n c e of P 0 i l l t h e i rons tones is due t o presct1c.e 01 2 5

p e l l e t a l col lophane i n such depos i t s . Collophane i s absenk il l

t h e l3IF depos i t s . Sulphur ( t o g e t h e r wi th phosphorous, tile 111osL

common i m p u r i t i e s i n i r o n o r e s ) , v a r i e s between 0.11 a t ~ d 0.20');': i n

t l ie bluro-BIT*'. Th i s is cons iderab ly high and i n d i c a t e s t h a t irort

sulphicle rnlrierals could be preserit i n t h e ores . It a l s o sugges t s

t11at t h e o r e s w e r e depos i ted i n a n environn~e~rl; where reclucLior~

of i r o n could have beer) important .

Another i l~ ipu r i t y i s alumina. 'It i s , however, low and r a r e l y

exceeds 0.576 i n Muro-UIF ores . Th i s r e l a t i v e l ack of alumina i n

t h e o r e s r e f l e c t s t h e absence o f aluminous minera l s such as

c o r d i e r i t e and s i l l i m a n i t e i n b t h t h e o r e s and t h e i r hos t rocks.

It a l s o sugges t s a dominance o f chemical p r e c i p i t a t i o ~ i over claslic

b

d o p o s i t i o ~ ~ during t h e forniatiotr 01 t h e ores . l ' l i i . .c is I ' t11 I I I { * J .

nrc h i g h e r i n UTIC o n l y whel~ t h e r e is a g r e a t e r j r ~ f J ux o l c last ic-x:

c l r ~ r i ~ i g i r o n formation.

Tlle suniliiary of chcnlical variations trcl ween the Mura 11 1. I:,

t h e I t a k p e h i l l o r e s , and t h e Agbaja i r o n s t o n e s , rcpresell t i l icj

tile main i r o n d e p o s i t s i n N i g e r i a , i s shown g r a p l ~ i c a l l y i n

1 . 9. The i r o n s t o n e s a r e f a r s e p a r a t e d from t h e I t a k p e h i l l ,

allti Eli~ro UIF o r e s , and c l u s t e r a t the Fe ( + ~ l n ) apex. T l ~ i s

r e f l e c t s h i g h e r i r o n ox ide c o n t e n t s o f t h e i r o n s t o n e s w l ~ i c h

c o r r e l a t e w i t h low s i l i ca c o n t e n t . The Muro UlIp o r e s c l u s t e r

f a r t h e s t from t h e Fe ( + ~ n ) apex and c l o s e r t o t h e Si-apex. T h i s

r e f l e c t s t h e dominance o f s i l ica i n t h e Muro BIb . The I t a k p e

h i l l o r e s have a n i n t e r m e d i a t e Fe compos i t ion , bu t are c l o s e r

to the BLP. Compared t o t h e o t h e r N i g e r i a n i r o n o r e d e p o s i t s ,

t h e Muro UIF has the lowest A 1 c o n t e n t .

3.2 blarble Ueposi t -- -- blarble is t h e other importanl; depos i l; i n t h e s-Lurly ill't';l-

I ' i ~ e l i ~ ~ ~ i n a t - y i n v e s , l ; i y a t i o n s i n d i c a t e t h a t it is moi-c n l ~ r ~ ~ l r l o ~ i l l.l1;1.11

1.11(.1 11 11;'.

3.2.1 i\lotle of Occurrence

b

Marble o c c u r s as e l o n g a t e d N-S d e p o s i t s on Lhe r n s l c r t ~ a r ~ d

w c s l e r ~ i s c c t i o n s o f t h e Muro h i l l (F ig . 3) . The delmsi 1,s c . x . I . o I I ( I

flwre l t ~ c Loltonl of t h e h i l l s i n t o t h e v a l l e y s alid cover n ? J ~ - C V I ~ . I L I

1 - of 4 1 v l l s The e a s l e r n depnai 1 [ r~~arl l kc ctwppil~rl 0 1 1 1

ill I l ~ e val l e y c a s t 01 t h e Iluro h i l l ) is wel l developed nlld r- i~ns

fro111 south o f Huro v i l l a g e t o beyond D i t i k o i l l t h e s o u L l ~ e r ~ l

t)ounclaries of t h e s tudy a r ea . I n t h e western s ec t i o l i , lhe depos i t

is covered by t h i n l a y e r s of grey nol l - f r iable s o i l wliich suppor t s

o ~ i l y s p a r s e growth o f g r a s s e s and trees. The depos i t occurs as

a LhicIi bed on t h e e a s t e r n s e c t i o n , exLending f o r more tIlan 15 kr~ .

The exac t n a t u r e of t h e bed is not wel l e s t a b l i s h e d as i ts

oulcrops are very shallow. It appa ren t ly t h i c k e n s southwards and

has a s l i g h t w e s t e r l y d i p s i m i l a r t o t h e o t h e r rock types. T h i n

bands, e s p e c i a l l y i n t h e c a l c - s i l i c a t e v a r i e t i e s have clip va lues

0 ranging from 30 t o 32 W. The outc rops are v a r i a b l e and may occur

as ex t ens ive rock masses, o r as t h i n lenses . The forlncr is

widespread around Iluro Kasa and Obugu, and a r e found alolig s t r e a i ~

l e d . 111 t h e v a l l e y s it is covered by grey t o dark g r e y s o i l s .

The s o i l cover is very t h i n s ~ h t h a t t h e marble c rops 0111 eve11

,~lurlcl 1'001 patlis.

I. 2.2 'l'vpcs of lilarble and Mit~eraZoyy - - --- --- -- - . - -

( a ) 't'ypes of marble -

011 L l i ~ i r dorninant c o l o u r s ) a r e colll~non i n ttie depos i t s , Thc whi le

1nal.ble is e s s e n t i a l l y whi te co loured , but sonle t imes i t is d is -

coloured t o p ink i sh o r g r een i sh wtli.te. Tlle p ink i sh and g r e c ~ ~ i s l i

5 9

d i s c o l o u r a t i o n are probably as a result of haematite nrrd c h l o r i t e

e n r i c l m e n t i n t h e m a r b l e as s u g g e s t e d by Rates ( 3 9 6 0 ) . The w h i t e

~ n a r b l e i s g e ~ l e r a l l y more abundan t i l l t h e s o u t t ~ e r t i p a r 1 o f t11e

slucly area. The d i s c o l o u r e d v a r i a n t s are predomit~anL ; i ~ . o ~ ~ r ~ c l

0 1 Sout11 o f Obugu, n e a r U i t i k o , L l~e l aa rb l e i s ~ O I I I ~ I ~ ~ I I I ~ J y

w l ~ i 11. w i l l 1 a few g r e y p a t c h e s , b u t t h e s a m p l e s c o l J ec l v d 1 r ~ I I I

'l'itlilic. arc b r i l l i a n t l y w h i t e . The w h i t e n ~ n r b l e is l i . t r r a i t1c.11,

1lni.d a l l c l s l i g h t l y r e s i s t a n t t o w e a t h e r i n g (where ex l )oscd ) . Lt

j s also h i g h l y f r a c t u r e d a n d b l o c k y i n n a l u r e .

The g r e y m a r b l e c o n s i s t s o f ' banded ' o r s t r e a k e d and n~ass i -vc

v a l - i c l i e a . It is w i d e s p r e a d a r o u n d Muro K a s a a n d soul11 o f Iluro.

The Lmnded v a r i e t y c o m p r i s e s o f masses w i t h a l t e r n a t i n g w11i Le

a ~ r d g r e y o r d a r k bands. The d a r k bands are e l o n g a t e , s h o r t o r

i I - r e g t ~ l a r s h a p e d , b u t t h e w h i t e b a n d s are f a i r l y u ~ l i f o r m a n d

elo11gaLed. Tlle bands are t h i n , v a r y i n g fi.om 1 cm t o 5 ern. Tllc

Im~~clet l 1nar1,lc i s similar t o a n d p r o b a b l y t h e same as t l loso

d e s c r i b e d as l i t - p a r - l i t m a r b l e by Moybo a n d Nnolirn (1985). T t ~ e

is t h e l i g h t g r e y o r dark c a l c i t e - r i c h rock w h i c l ~

It is sor~re t imes l a y e r e d and f r a c t u r e s i 1 1 1 o I l ~ i t ~

lates. Other 's are nol i - layered arid f rnt:Cur.e i 1 1 1 o

which are f oulid c l o s e t o t h e d e p o s i 1. ' L ' l i c b IIILIS* I \

yrey.ll~arl,le i s w e l l d e v e l o p e d a t t h e f o o t o f t h e h i 1 1 s o t ~ l l ~ e a s l

of P111ro. I n most p l a c e s i t o c c u r s t o g e t h e r w i t h t h e s l r c n k e d

v a r i e t i e s .

I-cgr11 ar I la t p

la1 (JL' b o u l d e r s

( 1 8 ) F l i ~ ~ c r i l l o g y

Tlie ~ n n r b l e d o e s n o t v a r y i n m.ineraloyy as i t doc:; i 11 c . 0 I OII I .

7'0c csscratinl n ~ i n e r a l s are ca lc i te a n d q u a r t z which co~lsLi . l . r~ lc

more than 95';: o l t h e m i n e r a l c o n t e n t o f t h e rock . Opoqr~e

~ n i l i e r a l s ( p r o b a b l y i r o n o x i d e s ) are a c c e s s o r y i n some of t h e

s n w p l e s , b u t i n a few o t h e r s , m o s t l y t h e g r e y m a r b l e , t h e y n~aicc

t ~ p t o I'$ o f t h e m i n e r a l c o n t e n t . A l e w d o l o ~ ~ i i t e r~riiiils are l'o~~tltl

i l l g r e y m a r b l e s a m p l e s c o l l e c t e d a l o n g a m a j o r strean v a l l e y

s o t ~ t h of M u m ksa . M i n e r a l s s u c h as t r e r n o l i t e , w o l l a s t o t i i Le, n ~ ~ t l

d i o l ~ s i d s folttlrl i n some o t h e r N i g e r i a n ~ n a r b l e d e p o s k t s s u c h as l l ~ c

I J l m m n r b l e s , d e s c r i b e d by Kayode a n d Er~u ( 1 9 7 6 ) , d o iwL o c c u r

i n Llie o n e s t u d i e d . The Ubo m a r b l e is c o a r s e r g r a i n e d a i d h a s t~cc:tl

af Cectod by i g n e o u s i n t r u s i o n s .

3.3.3 Geochea~istry

( a ) I l e s u l t s of Analysis o f Marble

The r e s u l t s o f the c h e m i c a l a n a l y s i s o f m a r b l e are give11

i l l T a b l e 9. F o u r s a m p l e s ( two g r e y ~ n a r b l e ; TM-10, TP1-35, a ~ ~ d

two w h i t e m a r b l e ; Tkl-2, TM-22) w e r e anc l lysed f o r n ~ a j o r o x i d e s .

LOT w a s a l s o d e t e r m i n e d a n d r e p r e s e ~ ~ t s m a i n l y CO . The rest11 La 2

were c a l c u l a t e d o n w e i g h t p e r c e n t and t o t a l v a l u e s o b t a i r ~ e t l r a n g e

b

f ro111 99.97 t o 100.65. The chemica 1 a n a l y s e s were c o n ~ y a r e d wj. L h

p u b l i s I i e d d a t a able 1 0 ) on t h e Ubo m a r b l e , t h e Ja lcura , t h e

l g b e t t i , t h e U k p i l l a a n d t h e Durum m a r b l e s wllich a l s o o c c u r i t 1

CnO

TOTAL

0 3

Chcniical Analys i s o f Marble 17ro111 Muro A r c a , N iger ia .

loo. 65 I

I

Analys i s conducted i n Departments o f Geology and Uioche~nis try , U n i v e r s i t y of N i g e r i a , Nsukka.

*Car?-ied out at P r o j e c t Developn~enL Ins-LiCuLe ( P R O ~ ) A ) , E~luyu.

T I I Average Chemical Analyses o f Some blarb1.e Deposits i n N i g e r i a

I ulm Oxi 11c

I Marble

- B

Uurum Marble

-- 4-07

-

0.26

0.28

-

31.02

20.76

-

-

-

0.03

T r

11.3 . %5

- ---

loo. 17 - -

C

I g b e t t i Flarb1.e

S o u r c e s ; A : Kayode and Enu, 1976

1 1 P T) 1,'. n I q 9 .tnf,q

( 1 ) ) 1)i.scussion of R e s u l t s - -- - -- - -

Table 9 shows t h a t t h e marble has l ime c o r ~ t e r ~ t be1wee11 51.011

a n d 53.12$1, wi th t h e whi te marble r i c h e r t han t h e grey ones.

'l'l~e r n a y ~ ~ e s i a ( ~ ~ 0 ) con ten t is low, and vary between 2.12 and

2.20$. MgO conterit of 1.41 t o 3.62% able, 4 ) is o b t a i t ~ e d f o r

tile Muro ElIF which occurs near i h e marble depos i t . Th i s low

magnesia con ten t corresponds t o tlie r e l a t i v e l y l a c k o f dolomite

c r y s t a l s (Table , 3 ) i n t h e marble and sugges t s t h a t t h e Muro

(Obugu) rnarble belongs t o t h e low magnesium marble i n Sclunalz arld

Chave 's (19631, FlacKenziels e t al. (1983) c l a s s i f i c a t i o ~ i s . l'he

low niaynesiuai n a t u r e of t h e marble, c o n t r a s t s wi th abur~dilr~ce o f

dolontites p a r t i c u l a r l y i n a s s o c i a t i o n w i th DIP as desc r ibed by

0 ' rourke ( 1961), Gross ( 1973) , Bayley and James ( 1973 ) , Morris

m~rl Ilorwitz (1983), and g e n e r a l l y i n Precambrian terrai . r ts (Pi.:l.lic?v,

i972; lloliov and Yaroshcvsky, 1972). llowcver , low mng~re~ . iu~~ i

is foi:~~iaLio~i under a cond i t i on which does riot a l low co-p~.er.il)j L i l t ic111

2 I- o r , a ~ l d Ng2+ions. Chal inyer arid Uissel (1963) oilset wad L l l : ~ l

! l o I o111i Le p r e c i p i t a t i o n w a s p o s s i b l e under a P r e c a ~ n l ~ r i a ~ ~ cotldi L j O I I

b

w i l l 1 low ca/l\lg r a t i o arid a high PC0 Siege1 (1965) i~~vest ignl ;c :d 2 '

n ~ i d observed t h a t primary d o l o n ~ i t e foruis o n l y i n waters o.f high

1'11 co t~d i Liori between pl-1 8.9 and 10, and t h a t al: pII ) 9.0, Ca 2 I

2 + and Mg co-precipitate to form dolomites. The work of Chalinger

and Bissel (1965) shows, however, that in a marine water with

0 (a) pH 8.0, (b) high Mg/Ca ratio, (c) temperature 30 C, and

(dl high salinity, dolomite could form. The above investigations

indicate that both pH and M ~ / C ~ ratio are important in determining

2 + the concentration of Mg in carbonate rocks, but M ~ / C ~ ratio

appears to be more critical. If the conditions necessary for

dolomite formation are not satisfied in an environment, what may

result is a low-magnesium marble. The M ~ / C ~ ratio ranging from

0.034 to 0.035 (Table, 9) is very low and could not have supported

the precipitation of many dolomite crystals. This would account

for the low-magnesium nature of the Muro marble.

Schmalz (l972), stated that low-magnesium marble could also

result from accumulation of low-Mg shells, while Chave (1954) and

24- Goldsmith (1960) suggest that it could result from loss of Mg with

age, from previously Mg-rich carbpnate deposit. The marble under

study in this work does not contain fossils which could suggest

organic origin, but the absence of fossils could be as a result of

its metamorphism. Schmalz (1972) noted that metamorphism of marble

b

. . is usually accompanied by crystal growth and destruction of primary

structures such as fossils, bedding and pisolites. MacKenzie et

al. (1983) observed that molluscs have clacareous shells with

up to 596 MgC03, echinoderms 8 to 15% and algae, over 20%. They

are of the opinion that carbonate rocks formed by, say echinoderms

in the tropics, have magnesium content between 8 and Ilk%. This

range is far greater than the values obtained for the marble being

studied, and could suggest that the marble was inorganically

formed. Inorganic origin for the marble is also supported by the

predominantly fine grained texture it exhibits. Chave (1962)

and Schala (1972) observed that inorganically precipitated calcite

is fine grained and lack organic debris. It may have precipi-

tated hitially as fine grained aragonite crystals which are more stable

in slightly low pH solutions (Schmalz and Chave, 1963), and then

converted to calcite under normal conditions. Simmons and Bell

(19631, have shown that fine grained aragonite quickly inverts

to calcite under natural condition. Initial aragonitic form is

favoured because Goldsmith (1960) had noted that even marine

organic aragonites do not containaabundant magnesium.

' Silica and alumina are other important oxides in the marble.

The silica content is similar to those of the Ukpilla marble,

the Jakura marble, the Burum marble and much lower than that of

the Ubo marble (~ables, 9 and 10). The higher silica content of

the I h o marble is perhaps due to the presence of silicate rni.rwro1.s

s l ~ c l ~ a s w o l l a s l o n i t e , and c l inopyroxenes i n a d d i t i o n t o qr~ar'Lx.

S11cl1 ~ n i ~ ~ e r a l s a r e n o t p r e s e n t i n t h e Muro marble. Olhcr uxit los;

exceed 0.k$ each.

LOT r a n g e s from 31-88 t o 36-34?;, it is similar t o t h e

clvcrnge LO C c o n t e n t s o f t h e o t h e r N i y e r i a n nlarble depoai ts cxt:cal)l

Ll~e Ubo marble (Tab le , 1 0 ) and is c o n s i d e r e d t o r e p r e s e l i l tlle

CO . Following t h i s assumption (based on t h e fact ; tha-L CO is 2 2

t h e most doll~inant v o l a t i l e component i n c a r b o n a t e s ) , t h e CaCO 3

c o n t e n t o f t h e Muro marble would be between 84.41 and 88.27%-

T h i s f a r exceeds t h e 41.01 a v e r a g e CaCO c o n t e n t f o r t h e l y b e t t i 3

d o l o m i t i c marble o r 74.3096 CaCO f o r t h e d o l o m i t i c marble depos i - t 3

a t Uururn. The CaCO c o n t e n t o f t h e Muro marble is however cl .ose 3

t o t h e 92.82% and 96.71% average CaCO c o n t e n t s f o r t h e marble 3

d e p o s i t s a t U k p i l l a and J a k u r a r e s p e c t i v e l y . The CaCO c o n t e n t o f 3

t h e bluro marble and t h o s e o f U k p i l l a and J a k u r a d e p o s i t s , a r e c l o s e

t o t h e approx imate ly 99% CaCO c o n t e n t f o r t h e h i g h e s t g r a d e 3

s t a t u a r y s t o n e d e s c r i b e d by n a t e s ( (1960) .

' . ' 191viro1iine1i-t o f Depos i t ion - T l ~ e d e s c r i p t i o n o f t h e environment o f d e p o s i t io11 i ,c: 1 1 i c l l ~ l L

l t i v e The two main environmerlts f o r UI'V tlcpos i l ..: alx, :

. ( ; I ) c o l i t i ~ i c n L a l e~ iv i ronrnen t , i n which i r o n n ~ i d s j Lica a1.c. t l ( > l i sc 1 1

Lepp and Goldich, 1964); (b) Marina environment, where weathered

or organically secreted sediments supply Iron and silica (~rubb,

191; Holland, 1973; Cloud, 1973; LaBerge, 1973; Drever, 1974;

Towe, 1983; Morris and Horwitz, 1983). In shoreline basins and

inland basins partially open to sea water, marine and continental

conditions interplay (Eugster and Chou, 1973).

The association of mica schist, marble and quartzite with

banda of iron oxides suggests that both marine and continental

conditions occurred in the Muro schist belt. The mica schists

were probably derived from pelitic marine sediments and deposited

in a shallow continental basin partly open to sea water. The

sequence of carbonate bed (marble) overlain by silica layer

(quartalte) and silica with bands of iron oxides (BIF) indicates

perhaps that fluctuations in the environment of the basin ranged

from slightly alkaline to moderately acidic conditions. An

initial alkaline and fairly high PC4 condition favoured the precipitation of carbonates (mainly

calcite) in the basin. The very low iron content (as Fe 0 and 2 3

EeO, Table, 9) for the marble formed by the precipitation of

calcite suggests that the environment was initially anaerobic

and warm. Drever (1974) had noted that in warm, anaerobic surface

water condition, calcite solubility becomes miriimurn and is pre-

cipitated, while iron in form of siderite and other carhonaics

remain in solution. The busi~i conditi 011 p r o h l l l y IJC:CLIIII ( : 5 l I !I!){, I y

acidic at the later part of carbonate precipitation, and allowed

the precipitation of silica which formed the quartzite bed.

The deposition of the basal pel.itic sediments, carbonate,

and silica partly filled up the basin and brought the remaining

basin water to the surface to interact with the atmospheric

oxygen. The basin condition probably became oxidizing and slightly

alkaline and allowed co-precipitation

of silica and iron oxides. The co-precipitation of silica and

iron oxides would result in deposition of iron-rich layer in the

quartizite. A reversal of the basin condition to acidic would

stop the precipitation of iron oxides and allow only silica to

precipitate. This would cause the deposition of silica-rich

layer. Alternations of alkaline, oxidizing condition and acidic

conditions would produce alternating iron-rich and silica-rich

bands in rocks, in basins where iron is being deposited. Alter-

nation of iron-rich and silica-rich bands occurs in the Muro BIF,

and probably indicates that cyclic changes in the pH conditions

occurred in Muro area. Cyclic chgnges in pH conditions of basins

in which sediments are deposited could be as a result of periodic

flooding of such basins ( ~ o u ~ h , 1958, Eugster and Chou, 19731,

or due to variation in the rates of evaporation-concentration

of the basins1 water (~u~ster and Surdam, 1973, Eligster arid Chou,

1973). Alternation of iron-rich and silic,-,-rich bands i l l i l T F

1 ) 1 - o r l l l c - . ~ . aild Cllauvel, 1979). The banding of the Muro BIP ape IS

prol~ably no t due to me1;amorphic differentiation as the n~etamorphic

grade of the rocks in Muro schist belt is low and ranges from

the chlorite zone to the lower part of garnet zone in the green-

schist facies metamorphism.

3.4 Economic Evaluation

A full scale economic evaluation of the BIF and marble

deposits, which would involve: the dressing and refining of the

ores and marble samples, the determination of applicable mining

methods and cost of mining, the calculation of the reserves of

the deposits, is beyond the scope of this work. However, data

obtained from field work, and analyses of samples collected

allow the following speculations:

Ore Reserve -- .- - Extrapolation of dips and strike of the beds indicate that

8 the possible reserves of 6.52 x 10 tons could be present in the

9 M-1 pre body, whereas about 2.53 x 10 tons occur in M-2 ore body.

The deposit of marble in the eastern part of the Muro hill has a

possible reserve of 1.49 x 10" tons (cf. Appendix IV, for cal-

cuiations 1 .

Tenor -- Chemical analyses indicate that M-1 ores have total iron

corlLc~~C i - a l g i r ~ g W c i n 2').59';/0 to 30.')1')/0, which is lrlclinly haernatite.

The 11-2 orcv have total iron content between 30.58 and 36.72%.

These ores have gangue of mainly silica which constitute 750~01. %.

Applicable Mining Methods - The M-1, M-2 and S-1 ore bodies have overburden thicknesses

which are generally less tian 15m. This overburden is made up of

compact, non-foliated quartzite and loose, friable soil materials.

0 The ore bodies also dip at high angles ranging from 35 to 5k0 W.

These ore bodies would most likely be exploited by subsurface

method; up-dip shafts and strike aligned trenches. The marble

deposit has very low dip, is very extensive, and has little or no

overburden. It will most likely be exploited by surface method,

using furrow-pits. A small scale quarrying of part of the marble

is in progress at Tidike where the marble crops out in a river

valley.

Refining of Iron Ores

The BIF ores are essentially haematitic and could be refined

byrblast furnace method, and converted to steel by Bessemer

conversion method. Conversion of the ores to steel may be slightly

problematic as they have a little more phosphorous than those b

easily treated with Bessemer converters. The BIF ores could also

' be extracted by floatation method. Recent studies by Uwadiale

and Nwoke (1985) indicates that BIF ores are highly extractable

by reverse anionic floatation method. With this method between

84.4 and 92.7'/0 recovery of concentrates having Fe grades of 69.4

to 70.4% has been achieved. This method is even more significant

as locally produced cassava starch was used as depressant.

Local Use of Iron Ores and Marble

The BIP ores are likely usable in Nigeria steel plants.

The ores are slightly poorer in iron content than the Itakpe hill

ores. The purity of the BIF (with respect to phosphorous and

sulphur content) and that of the Itakpe hill. ores are about the

same. It is therefore probable that the BIF is the most likely

supplement to the Itakpe hill ores as the main supply base of ores

to the Nigerian steel complexes. The marble, with very high lime

content would easily be useful in the Nigerian steel complexes

as slag former. It could also be used in cement production since

it is calcitic and generally pure. As slag-former in the steel

complex, it is most likely to help in development of the local

fertilizer industry. Slag, derived from steel plants are useful

in .production of fertilizers. The marble would also be of

architectural significance. The presence of various col.ours of

marble in the deposit will produce good terrazzo chips.

b

CHAPTER FOUIt

SWPlARY AND CONC JLJS TON

The I luro-schis t b e l t c o n s i s t s of t h e f o l lowing rock u r ~ i

g r a n i t e gneiss, m i c a s c h i s t s , marble, q u a r t z i t e , and IIIIi . h l c r i t c

i l i l r u s i v c s a l s o occur. The mica s c h i s t s comprises: a lower Iiorizoti

c o ~ r s i s t i n g quar tz -b io t i t e -muscovi te s c h i s t , quar tz-biol i te-gar ' r ie t

s c h i s t , and an upper horizou o f quartz-n~uscovite-chlori te schisL

and quartz-muscovite-garnet s c h i s t . Q u a r t z i t e a l s o c o n s i s t s

of a lower f o l i a t e d u n i t and a n upper non- fo l ia ted u n i t . The

sequence of t h e rock u n i t s from bottom t o t o p is, (1) g r a n i t e

g n e i s s , ( 2 ) ba sa l mica s c h i s t , (3) marble, ( 4 ) f o l i a t e d q u a r t z i t e ,

( 5 ) BIF, ( 6 ) non- fo l ia ted q u a r t z i t e and ( 7 ) upper mica s c h i s t .

TIie rock u ~ i i ts: marble , f o l i a t e d q u a r t z i t e , DIF, and noti-J'oJ i a l c d

q u a r t z i t e , o r i g i n a t e d as chemical p r e c i p i t a t e s , whi le the lmsaL

and upper mica s c h i s t s r e p r e s e n t p e l i t i c c l a s t i c scdis~elil s.

l'hcsc sediments w e r e depos i ted i n a sha l low, c o n t i n r i ~ l a l lal\o

L),isin and metan~orphosed t o c h l o r i t e zone and lower cjn1.11c:L zol~c'

i l l t h e g reensch i s t f a c i e s . The rocks were a l s o dcior.111ctl t o

i s o c l i r ~ a l .Colds wi th NE-SW a x i a l t r e n d atid wcstcr.l y t l i 1 ) \ ~ r l ~ c ) ~ r .

0 m~gLcs range from 20 t o 81 . The NE-SW a x i a l t r e ~ l d i.s s i l ~ l i l a ~ .

l o t l ~ e NNU t r e n d ('Turner, 1983) o r N - S t r e ~ ~ r l (~,j ibadc., 3970)

obla ined i n o t h e r Niger ian s c h i s t b e l t s . The rock associaLiot l

01' t h e Nuro s c h i s t b e l t : - chemical p r e c i p i l a t e s with a Tnw

t: 1 n s t i c scc l i~~icr~ t s o f low grade metamorphisiu, and 11ii11o1' ( 1 0 1 ~ ~ - i I PP .

i s s i m i l a r t o t h e rock a s s o c i a t i o n co~apr i s ing qunrl,xi Le, t)larI<

shales, conglomerates, dolomites, massive chert, argillites and minor

volcanics that characterise most Superior type-BIF deposits

described by Gross (1973, 1980).

BIF and marble are presently considered the most important

economic mineral deposits in the schist belt. The BIF has iron

content ranging between 29.59 and 36.72%. The iron minerals

in the BIF are mainly haematite, and a few magnetite. Compared

with other known iron mineral deposits in Nigeria, the Muro BIF

ores contain the least iron, Al, and the highest silica percentages.

The BIF is however less deleterious than the Nigerian ironstones,

and is as impure as the Itakpe hill ores. Its average P/Fe ratio

of 0.0034 is slightly higher than the 0.002 upper limit (Percival,

1972) for steel making iron ores. The high sulphur content of

the ores shows that they may not be extractable with Bessemer

converters. The BIF would however be cheaply extracted by dis-

persion, using newly developed local starch depressant capable of

extracting between 84 and 93% of the total iron in the Muro-BIF

9 ores. The inferred ore reserve of about 3.18 x 10 tons of the

Muro-BIF is speculative and more investigations especially sub-

surface exploration would be conducted on the deposit to prove

i. t s reserve.

The marble deposit in the Muro schist belt is large. A n

11 inferred reserve of 1-49 x 3 0 tons is suggested. The marl,lc

and 2.20. Its calcium carbonate is high ranging from 84.41 t o

88.27% of which CO may be between 31.88 and 36.34%. This high 2

CO content and s imi la r ly high CaO content (51.64 t o 53.12%) 2

ind ica te t h a t t h e marble is a potential source of l i m e material

t h a t would be required i n b l a s t furnaces of t h e Nigerian s t e e l

complexes. The marble deposit is a v iab le source of good t e r razzo

chips, Surface mining is recommended f o r the marble deposi t ,

while subsurface methods would be used t o exp lo i t t h e BIF.

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Sar~iple P r e p n r a t i on Procedures

'rl~i-ee ruajor s t e p s were involved i n rock sample p r c p a r a t j o l ~ .

'J'lwse a r e :

(a) s e l e c t ion;

( b ) c lean ing and r educ t ion , and

( c ) (jl.illding arid d iges t i on .

Pclect iol l :

S e l e c t i o n of samples was based on t h e i r f i e l d ~wl.alionsl~ips

( I i 0 - 'No samples each 01 t h e t h r e e subtypes of Lhe ba~~tlct l

iron forrerrt ioi~ w e r e s e l ec t ed . TM-A a ~ l d TM-2A represcnl, tlle luassj vc.

s11l)type. TI!-3A and TM-6h r e p r e s e n t t h e banded subtype. The

mica-r ich sublype i s repl-escnted by the s an~p le s ~ 1 1 - 4 ~ allrl 'JTI-7A.

The f o u r samples o f t h e marble are widely separa ted . Fresh s~uiiples

w e r e s e l e c t e d t o avo id con tan ina t ion due t o weathering.

Cleaning and Reduction:

Sample c lean ing and r educ t i or1 w e r e done .to remove s u r f ace

i m p u r i t i e s and reduce t h e samples t o n~anayeable s i z e s . Cleaning

was done by t h e u se of s o f t t i s s u e s , b rushes and n~echaniaal. rock

c u t t e r . D i r t due t o d u s t , chalk o r i r k ~l~nrlcing and m o ~ i l ~ l ~ wlijch

nf feet t h e q u a l i t y of t h e r e s u 1 . t ~ were removed. Cleani ng 75 i t11

b

rock c u t t e r was p r e f e r r e d t o bruslles and t i s s u e s , a3 i C c l t s l i r . c s

tlcepnr pene t r a t i on . Jacksaw c u t t e r w a s uscd -to r : t ~ i l , nl ' l ' tlllr.wllli~-~brl

. G I I ~ - T;rccs. T l ~ i s w a s e s p e c i a l l y important where n~otrl tls r! 1.r-w i t ~ t l i

FIG. lo. Dlstrlbutlon of rock sample locations

w l 1 r b 1 . c i l k - i ~ ~ n r l t i l ~ y s pcnctrilLecl t h e r o c k surracc.. 1Jc. l : i . l l l l l ) 1l.s

\ccl-i- d r i e d to remove waLer which c o u l d a f f e c L tlie gi i~ i t l i r~cj

ef E i c i e n c y of samples.

I k d u c t i o n w a s done i l l two ways. Thesc were (a) c l i jpp ing

n l ~ d ( 1 1 ) rough c r u s h i n g . I iand-operated Jacksaw c u t t i n g 111nchitic

arid au1.ornnLcd r o c k c u t l e r w i t 1 1 diamoud bJ.ade w e r e tiset1 t o c u t t i l e

rock chunks i n t o c h i p s . The hand-opera ted r o c k c u t t e r was pr-efc1.mc1

t o automated r o c k c u t t e r b e c a u s e it was more f l e x j b l e . I L was

a l s o easier t o c o n t r o l t h e s u r f a c e b e i n g c u t . S ~ n a l l a n g u l a r c l i i p s

w e r e o b t a i n e d .

The c h i p s were t r a n s f e r r e d t o a Jacksaw r o c k c r u s h e r f o r

t h e i n i t i a l o r rough c r u s h i n g . Each sample w a s t r e a t e d s e p a r a t e l y

o v o i d i ~ i g c o n l a c t s w i t h o t l ~ e r s . l ' k i i ~ wns Lo et is111~3 (t iat I l l < + sa1111)lc&:<

do rmt mix t o a v o i d c o n t a m i n a t i o n or d i l u t i on o f orie snlep l cB b y

nllot.her. I7ough c r u s h i n y produced g r a i n s o f s i z e s I ~ c t w e c ~ r 0.1

a l ~ t l 3.0 I I I ~ I I . C o a r s e r o n e s w e r e r e c r u s h e d .

and laster arid u s e d o n l y f o r t h e marb le samples. The agate I);il I - - *

n ~ i d mr Lar w c r c used f o r t h e i r o n o1.e samples . Gi- i~id i ti!) was ( I O I I P

a't Ltic s p e e d o f between 1.5 a n d 3.0 r p s f o r one 11our. 'I'lic r.oc.lc

powder ground -to ~ 1 8 0 microns are s t o r e d i n p l a s t i c Lot t l e s .

T h i s i s t h e last s t a g e i n sample p repa ra t i on . 'l'wo s o l u t i o ~ ~ s ,

A a r ~ c l 13, w e r e p repared from each sample. Comple-l;e d i g e s t i o n

was ob ta ined by a c t i o n of a c i d o r a c i d mixture on sodium I~yrlr-oxi.de

f u s e d and nor]-fused rock powdor.

Sol r r t io~r A: w a s p repared by fu s ing 1.0 y of sample w i t l i 1. Ti !I 0 1

:otliurn llyciroxide p e l l e t s and d i s s o l v i n g i n 2M IIC L . 'I ' l~i s 50 1 { I I i r j ~ i

w;ls crsed t o dc tennine - / ? i ~ 7 arid /xl O 7. 2- - 2 3-

:!ol r ~ t i on I3 is a s i l i c a d e f i c i e n t s o l u t i o n . It was I ) I t , j m ~ ~d I J \

~lis. . ;olvi~ig a srnnll p o r t i o n of t h e rock powder ill a11 n r i t 1 I I~~ ' : I I I I ,

c . o l ~ t a i n i ~ ~ g 7: 3: 3 1-11?, 1lN0, and 1lC1O4. Th i s tnixturc is c : ; ) l w l ~ L i ~ 3

of' c o t ~ ~ p l c t e l y d i g e s t i n g s i l j ca. So lu t ion U was usctl t o r l r . l i : r . ~ l ) i I ) < *

t l ~ e o t h e r oxides .

'rhe ioll.wing a n a l y t j cal methods w c r c used 1 o tic-~VI-III i ttc

t l ~ e 111ajor oxides .

(a) U l t r a v i o l e t spectrophoto~ne.Lry: SiO A 0 , 0 i ~ r l t l 2 2 3 - 3

( b ) Atomic abso rp t ion spectrophotometry: T i0 a11tl M t 1 0 . 2

( c ) lplanle photometry: Na 0 arid K 0. 2 2

(d) El)?!~i complexometry: CaO and MgO

(e ) Potassium d i ch ro~na te t i t r i m e t r y : Feu.

( f ) Gravime t r i c method: S

( g ) Direc t combuslion: L01.

1'1 occdure : SpcciTic c o l o u r s of a l i q u o t of s o l u l i o n A wc.~-c: clcvv l o l b t , i l

Tor SiO and A 1 0 arid s o l u t i o n B f o r Fe 0 and 1) Or. !Pile 2 2 3' 2 3 2 >

h ~ p e r i a l Col lege Laboratory handouts, (1976). The co Lo11r-s wcrc

s e l e c t i v e l y absorbed by r a d i a n t energy Irorn t h e sl~ectrol)llolo:~~cl~~r-

a t s p e c i f i c wavelengths ( c f . Table X ) . The concen t r a t i on of' L I I P

elernetlt being determined i s measured as j nstrurnoit: absorl)ar~cc.

Pye-Unicarn Sp6-400 spectropbotometer avai:l.able a t the b

department o f Biochemistry, Universi-ty of Nigeria was ur:c:tl.

' k b Le X bclow g i v e s t h e co lou r s of nliquoL and w n v c l o ~ ~ ~ l t t ~ s I ' o t

clr: Lcn~~ in i l l g va r ious oxides .

Tnljlc X. Colours of a l i q u o t and wavelengt l~s f o r spco l.l.ol)lio Lo- inc t r ic a n a l y s i s ( a f t e r I n ~ p c r i a l Co l l cgc , l y ' i0 ) .

- t A 1 0 2 3

Light b lue 1 i 495 I

I'c 0 Orange 2 3 5 10

S i O 2

650

I I' 0 Blue-black

2 5 890 -- ---- -

* l ) i s t i l l e d water was used a s check.

Tire r e s u l t s ob t a ined w e r e t r e a t e d as fo l lows:

'i/o oxide = F x absorbance

Where F = f a c t o r

I? was ob ta ined from

f = volur~ie o f s t anda rd talcen (ml) x 10 ---.-- volume o? sample a l i q u o t x absorbance

U s i n g t h e above, t h e l a b o r a t o r y accuracy f a c t o r ('>o which t a k e s

c a r e o f d e v i a t i o n due t o opertitiolral c o r i d i t i o n i i s found.

o( = 55 oxide f o r s t anda rd used

-. -- - -- - - - .

f

I . ATIRlIC ht3SOWTION SPECTRDI'I IOTOPEl'ItY ( AAS ) . I1rocedure: About 1.0 g of tho samples were cl iseolved i l l 1 : 3 I I N O ,

tr~rtl wnrrnetl on a hok p l a t e . The conterlts were al'lmwcl l o c o i l i 1 1 1 c I

c a r e f u l 1 y t r a n s f e r r e j t o 200 m l f l.aslcs. The s o l u l i o t i s were

rli I.utecl to 100 m l w i t h d i s t i l l e d / d e - i o n i z e d water-. TIIC S ~ I I I I > ~ . P S

*ere then r u n w i t h s t a n d a r d s i n t h e i n s t r u l r ~ c ~ ~ t a t speci fj.c

a ler~ie l r ta l wavelengths - u s i n g s p e c i f i c lanlps. The absoi-lmnce o f

e a c h sample was t h e n r e a d .

The absor'bances were t h e n used i n p l o t t i n g a y a i n s t t h e

c o n c e n t r a t i o n o f e a c h s - t andard i n ppln.

s t d (pprn) absorbance

l k s u l t s w e r e c a l c u l a t e d as

Coric. i n pprn x 25 76 o x i d e = - -. - weigh t o f sample used x 100

0 U are vnpor i sed a t t e m p e r a t u r e s between 3 .000 C and 3OCHl I:. Y ' l k t - V ~ I H I I I 1 .

s c-ontairring excited ions developed c h a r a c t e r i s t i c s p ~ r I 1-a. ' l ' l ~ ~ +

, cpnc tra were f i l t e r e d u s i n g sodiuni a ~ l d potass ium -Tj.lanle~rts w t l

I I ~ r b i ~ l t e n s i t i e s o f each r a d i a t i o n was d e t e c t e d by n gcr lunr l ra~~cl~l . .

A s i ~ l y l e c e l l flame photon~eter (n~odel EEL Mark 11:) w i L l i a i r

coalpressor and propane gas were used. D i r e c t ga lva t~o~nc tc r

tlcSLec t ion were used as lneasures of i n t e n s i t y . The r e s u l t s were t r e a t e d as

2 x s c a l e of deflec-Lion 3Q oxide = - . - . - - - average d e f l e c t i o n per pjhl o f a l k a l i oxide.

U. EVPA C O I \ l P J X X ~ ~ l ' R Y

Procedure: 25.0 m l of solution B o f each sample is t i t r a l e d

a g a i n s t 0.3':/u ED'M i n a 400 r n l beaker a t pH betweell 7 and 11.

Eriocl~rome Ulack 'l' w a s used as i n d i c a t o r . The end-point was

obtained when the s o l u t i o n changed from wine r e d t o deep blue.

rtle r cac t io l l at t h e end p o i n t is rep re sen t ed by

M - L n .r- ELTm PI-EDl'A + I n

\\.lN>l c-

11-111 - Plagnesium - i n d i c a t o r coniplex = w i I I ~ 1 .~311

El-EIYM = Mngncsfum - EDTA complex = no co lou r

111 = 111dicator (Eriochrome Ulack T) - deep b lue

C11tcr-I'erence caused by presence o f Co, Ni , Cu o r Pin w a s 111:rrkctl

by a d d i t i o n of hydroxylamine hydrochlor ide.

T11a r e s u l t s ob ta iued w e r e t r e a t e d as fol.:Lows:

( a ) f o r My0

b

1 n r l 0:Dl ELWA = 2.432 Mg (Voyel, 1961)

B . POTASSIUN DICHROMATE TITRIPLETRY

f'roceclure : S Landard s o l u t i o n s of HE' d i g e s t e d san~p Les 01 Llic

I-ock were t i t r a t e d a g a i n s t s t a n d a r d s o l u t i o n o f Po tns s iuu~

diclrroinate. U a r i u l n diphenylamine s u l p h o r ~ a t e w a s used as i~rtl icnl O I . T l ~ e end p o i n t w a s ob ta ined when t h e gre-green co lou r of acid

~ n i x t u r e and inllicator t u r n s v i o l e t . Tile r e s u l t s ob t a ined w e r - c

treated as Iollowsr

56 l7eO = (vol . ( i n l ) of K Cr 0 (sample) - v o l ( I I I ~ ) o f 2 2 7

b lank) x 1.7963.

A I 1 r e a g e t ~ t s w e r e p repared as s p e c i f i e d by Whipp1.e ( 39';"1) .

1 GlIAVIPE!'rltIC 1 ~ E ' ~ ~ l I N R T I O N OF SULl~IlUII

E'rocedure: 2.0 g of each s a n ~ p l e w a s f u sed w i t h 10 (I of Nn,,CO 3

a ~ ~ d 0.25 g of 1(NO at about 1 0 0 0 ~ ~ f o r 30 minutes. 7'hc me1.l w a s 3

n l lmed to cool, and extracted i n t o a 250 m l beaker w i t h hot w n l c r .

A s n l a l Z qumr t i t y of e thano l was added t o t h e rnixturw n11d

l hen d i l u t e d t a 150 h11. The benlrora wore coverocl nritl t l ~ c mm1,lc.r

llcnlccl i ~ r stcan batli.

The niixlures w e r e f i l t e r e d and t h e r e s i d u e wnsllcrl wi l l1 1101

q o c i i ~ e n carbollate. The f i l t e r a t e s were trar~sferrerl t o 800 l o l

I~c~nltors and d i l u t e d -to 500 n 1 1 . A few drops of r n e t l ~ y l red wcrrb

ntldecl atid t h e n concent ra ted ZEl i n excess a t l ~ e u t r n l lmi t i t . ' l l ~ f ~

a o l u l i o n s wel-e bo i l ed to remove CO and sulplrur prec i l~ i ta tcd 2

by a d d i t i o n o f Harlum Chloride. The p r e c i p i t a t e s were ol~i.aincrl

by f i l l e r i n g , d r i e d and weighed t o o b t a i n q u a n t i t y o f sulphur .

. 1)IRECT COFIUUSTION

1'1-crc.cdu1.e : 1.0 y of sai iples were c a r d u l l y weighed P r ~ l o p l a t i ~ t u ~ l ~

tlislics and re-weighed. The samples w e r e Chen put i n electric

f u r n a c e arid temperature r a i s e d t o 1 0 0 0 ~ ~ for 2 hours. The saruplcs

wet-c rcnioved and rewci ghed u n t i l a cotlslant weig lr t , w a s 01)l.a knot1

l 'or each. The l o s s i n weight from t h e o r i g i n a l weight o f S ~ I I I P ~ C I

was regardecl as l o s s on i g n i t i o n and c a l c u l a t e d i n perccn1o;je.

APPENDIX I f f

3.33 27.61 0,02 3.49 33.23 0.38 2.64 26.95 0.05 4 . 09 ?A. 4 9 1:). 03 42.87 0.00 0.00 44.92 0.00 0.07 4 4 . 4 4 4:). I>(:& I).. +><I 4 1 - 4 9 ir.C~tS C t . 0 5 34. 24 0. 00 I).. OR 37.RO O.i I0 0.05 :32. 5R 0. Ol> 0. OD 34.13 0.00 13-13 7.7 ,>..t. 12 0.00 0.00 3 6 . ~ O.IXI 0.00 4v .9~ n.oo 47.40 0.00 !W.b;f 1i).0(3 S O . 1 1 CI. 1.113

5 1 . 1 8 0. I:)O 42.50 n.OO 4 4 . 1 b 1'1. CU:I

44. 16 (1. 00 4 2. 5 1 0. DO .- "- .. -...

V . V h

O.Ct8 0.07 0. 1 5 1). 07 I). 20 0.37 0.22 0. 1:19 0.05 CI.10 I). 11 0.12

1R. 19 0.56 13.90 0.42 15.71 0.46 1 4 . 7 CI 0 . 53 59.92 1.44 27.07 1.11 IV. 16 0.19 15.~16 0.29 21.66 0.70 22.51 0.19 14.47 13.24 26.67 0.31

LL. L C ) 1 /. W O 3 . .AS

P 'e to ta l

Fe 3+/Fe2+

Mn/Fe t o t a l

P / F e t o t a l

i n f i n i t y

Reserve = Volume sf deaosit x averaae ore arade x saecific

less (width)

losit (2)

2. The vertical thickness was calculated from

3