-

University of Nigeria Research Publications

AGWUNOBI, Ohams Ethelbert

Aut

hor

PG/M.Sc./81/1188

Title

Resistivity and Magnetic Surveys for Groundwater in Fobour in the Jos Area of

Plateau State

Facu

lty

Physical Sciences

Dep

artm

ent

Geology

Dat

e

January, 1984

Sign

atur

e

RESISTIVITY AND NY\lsNEcIC SURUEYC FOR GROWATER IN FOBOCJR IN THE

JCE AREA OF PLATEAU STATE.

OF G E O E Y IN THE F W Y OF PPrYSZCAt

SCIENCES IN PNITIAL FULFIUENT OF

THE RKlUIfEMM'S RYI T k DSfGE OF MASTER OF SCIENCE

UNIVEEITY OF NIGERIA, H S W .

JANVMYv 1%

Mr. Agwunobi Ohms EtheIbert , a postgraduate stuclont

i n the Depar.tmcnt of Geology, University of Nigeria, Nsukka

has satisfactorily completed the requirements for courme

and project works for the degree of Master of Science ( E c

Applied ~ e o ~ h ~ s i c s ) i n Geology.

The wrk embodied in his Project Report is original and

has not been submitted i n part or f u l l for any other diploma

or degree of t h i s or any other University.

W R Dr, K,M, Onuoha Supervisor Gaology Department University of Nigeria Nsukka ,

irg

Dr. A X , Onyeagocha Acting Head Department of Geology University of Nigeria Nsukka.

L,DI(X'C ION ------

T h i s vork is dedicated to my wife

C O N T E N T S

L i s t of F igu re s i L i s t of Tables i i ~lcknovrlcdgemcnt i v Abs t r ac t v

PAGE

CHAPTER 3.

Ih!RODUCTION Id!! PREVIOUS !'YOiXS

I n t r o ~ l u c t i o n . . 6

Previous works i n t h e Arca a

GEFIEIUIL GEOLCGY OF THE AREA . . Gcncra l Gcology . Younger G r a n i t e s . C r y s t a l l i n e Basement . . F o l i a t i o n . . . . J o i n t s and F a u l t s . . .

P l a n and Ob jcc t ivcs of t h c survey .. 14 Ins t rwncn ta t i on and F i e l d Prcccdurcs ., 15 R e s u l t s of t h e E l e c t r i c a l R e s i s t i v i t y P~leasuremcnts . . .. . 23 hlaqnctic ~ s t i g s t i o n s . . . . . 59 Discuss ion - < f t h e R e s u l t s . . . 80

Topographic

Outline map

i

LIST OF FIGURES

T i t l e - P a m

map of Fobour and environs 3

of Nigeria, showing tho study area 4

Geologic map of the area 10

Map of t h e area showing layout/locations of of soundings and pro f i l e s 22

Extcxnal features of the Resistivity equipment 16

Extcrnal features of the Magnctomcter 19

Geo2lcct~ic dcpth section for sounding curves ES1- 41 ES *6

Resistivity c ~ r v e of ES.1 25

Resistivity curvc ~f €3.2 28

Resistivity curvc of ES,3 31

Cosistivity curve of ES.4 34

Resistivity curve of ES,5 36

Resistivity curve of ES.6 39

Resistivity curve of EF.l 44

fiesistivity curve of EP.2 47

Resistivity curve of EP.3 48

flesistivity curve of EP.4 51

Rasistivity curve of EP.5 53

Resistivity curve of EP.6 56

R~sistivity curve of EP.7 55

Magnetic anomaly curve of bP. 1 62

FAaynotic anomaly curve of FP.2 65

LIST OF FIGURE3 Cont,

Magnctic ancaaly curvc of MP .3

Magnetic anomaly c u m of MP,4

Magnc.tic anomaly curvc of MP .5

Magnetic anomaly curve of MP.6

Magnctic anomaly c u m c of EQ.7

Magnotic anomaly cuwo of MP.8

CoxrclaCion of Rcsistivity curves of EP.2, 3 and 7

Correlation cf ncsistivity curves of EP.4, 5 and 6

Corrclation of Magnctic anomaly curvcs of LP.3, 4 and 5

Corrclation of Magnetic anomaly curves of MP.5, 6, 7 and 8

Resis t ivi ty map of t h e area

Magnctic map of t h a area

Locations of recomncled sites

Tablc - 1 .

&ST OF TABLES

Title - Data of Elcctrical Resistivity Sounding

Data of Eloctrical Resistivity Sounding

Data of Electrical ncsistivity Sounding

Data of Elcctrical Resistivity Sounding

Data of Eloctrical Resistivity Sounding

Data of Eloctrical Resistivity Sounding

Results of Elcctrical Resistivity Soundings

Data of Eloctrical Nosietivity Profiling

Data of Electrical Resistivity Profiling

Data of Eloctrical Resistivity Profiling

Data of Electrical Rcsistivity Profiling

Data of Electrical Resistivity Profiling

Data of Elcctrical Rosistivity Profiling

Data of Elcctrical Resistivity Profiling

Data of Magmtic Profile

Data of Magnctic Profilo

Data of Magnetic Profilo

Data of Magnetic Profilo

Datl of Magnetic Profilo

Data of Magnetic Profilc

Data of Maghotic Profilc

Data of Magnotic Pro f i l e

I am highly grateful t o Dr, K. M. Onuoha whose advice,

cfiticisms and sllggestions immensely contributed i n making

ti is work succcssf ul,

My gratitucle also go$= to Abam, Amke Adfndu, Madu, Mbonu,

Wuka, Bob, Foetsr, Paul and especially my wife Chinela who

helped in one w7.y or the other during the period of the project.

Encouragements fran Augoc Law and 3key are gratefully

acknowledged,

v

msTW\CT

Resistivity and magnetic measurements were carried out to investi-

gate tho groundwabr occurrence i n F o b o u r m a o f Plateau State of

Eligeria, The area is underlain by Pre-Cambrian basement complex

in t rudsd by the Younger Granites, the Older Basalts and Newer Basalts,

Eight pzofil4:s of magnetic measurements were carried out with

Ja landm flux-gate typo of magnetometer, Seven e lectz ica l profilings

and five ~Iec t l - i ca l s o u ~ d i n g s were done with an ABEM T'CSAS 300 terrameter.

A s i x t ! ~ electrical sounding was carried out near a bore-hole a t Jengere,

The r e s u l t s showed two probable locat ions of potential aquifers.

'The aquifgr depths and thicknesses show variations from place t o place.

Maximum thicl:nsss of overburden of 107 meters is registered a t electrica;

sounding s ta t ion numbor I (=,I) . A minimum thickness of 4'7 meters is

recorded a t electrical sounding s ta t ion nwnber 5 ( S . 5 ) . ~ h i k r q of the h

aquffer is rrspectod southwa~ l s . Subsurface resistivity and magnetic

veriations suspected t o be structurally controlled were also observed.

The area af intercst has no bed sock exposura on t h e surface,

L;~te.rpmtation (by partial curve matching) showed maximum depth to t h ~

probable unfractured awl um3athered basement to be about 110 meters,

.:he ceoph-qsical r e s u l t s showed a resistive in situ or transported

hard dw top soil.. The thickmsses of this tog soil vary from Dn to

about 7 meters i n places. The resistivity values vary from m f i m to

over M 3 0 d ? m m . Unclmlying the top s o i l is the weathsred and aquiferous

medium of low resistivity values of 42i?-.rn t o 257$cCm, Tho aquifer

thicknasses vary from 35 meters to over 90 meters; This aquiferous horizon

gradually grades t o unf ractumd and unweatk'bd resist f ve b a s m n t .

The sixth sounding at Jengere was used as a control for

accxa.te f n t o r p r e t a t i o n of results f r a a relatively virgin area of

F o b u r , From the analysis of the electrical soundings, the electrical

profilings anc! magnetic measurements two sites for bore-hole wre

recornmended f o r drilling, O n e of the sites i s located about 350m

south aa s t of Iyam - Fobour Junction and t h e other abouf; 900m t o

the w u t h c

Explo~ation geophysics has not played as imyj';rtant a part in

groundwater investigations as it has in petroleum exploration in the

C O U ~ ~ T Y ~ This situation has resulted mainly from economic considerations

t h a t have rsstricted the f inancial support to develope and apply geophy-

sical methods t o groundwater problems,

U n t i l mcen63y noli; much at.tent,ion was given to the solution of

g r ~ ~ w a t e x problms of some areas located i n t h e hard-rock terrain

(klasorncnt soinplex) of the country, With the exception of a few undetailed

I~ydrogeophysical surveys carried out by some companies like Mecon Services.

Alotis, Geocoi-mlt and others for their clients, most bore-holes are

s i t d and dri l led on ' @ h i t or miss basis",

In most of these works, ~nuch attention was paid t o tho *athered

horizon only, Ths repoz-2s lack information on the groundwater potential

of t!?e f r a s t~ roc l zon*s, Information capable of ai.dir.g t h e identif ic tio on

of geophysical :;ignatures a id hydrogeological parameters which can lead

!;CJ a stl.ccessfal location of sui table aquifers i n comparable d i f f i c u l t

t e ~ r a i n s are a lso lacking,

The present project was geared towards locating water bearing

horizons i n such hard rock terrains. The survey involved location of

such structures as buried l iver channels, fau l t s , highly .fractured and

j o i n ted horizons as well as weathered part of the bed sock capable of

hosting and t ransmit int ; water exploitable i n economic quantdties~

l e l r l Location and Axesrih4 1 i t ~

The survey area covers Fobour and environs i n the Jos,Plateau

Stake of Nigoria ard is bounded by longitudes 9°00'~ and WE; and l a t l t y d ~ s 9 ' 5 ~ ~ ~ and 9 '55#~ . Fobour is located about 23 Km

soutI+eas-t of Jos, An untamed lateritic road from Jos through larninga,

Jf rg in Sama and Iyam connects Fobour, (see figs, 1 and la) ,

L ,I . 3, phvsj:pgra~h.[

Fobour 5.5 oc n ~elatively f l a t and low lying area of approximately

13X3 meters Sove insan sea ievctl. The perimeters of the town axe defined

by chains of I~ilLs, To the North of Fobour is Shere h i l l s , t o the

South is the Fusa h i l l s and the Eastern perimeter is the Jarawa h i l l s .

The area is within the light Guinea Savana type 09 vegetationc

Light bushes alonc stream channels and s o w major joints on the vani t .?

hills dot t h c vegetation., The average monthly temperature is about

78% ( ~ 5 ~ 6 % ) ,

The rsirri season is nonnaly short a:~d lasts fo r about f o w months,

The rainfall. is Ilght w i - 3 1 moan annual precipitation of 110 - 150cm

(,F~~kins and Str~rnis:~_.:iacja 2906)~ The r a in f a l l i s characteriscd by a

high surfam run--off that %ed the seasonal streams, These stream

co.mses follow t h z j 0 9 1 C s i n t h c area,

1,'L Previog5VLo~ks ii.1 t h e fma_

The first recoxhd survey of tho N i g e ~ i a n tin fields dates back to

1919 under the direction of J.D. Fa:coner (Macbod e t al, 1971) b The

maj 3r results of the investigations by these earlier workers (eg Falconer,

R x l s u r ! ~ and grain; h a w been summarized by !lr!'xlsod e t al. (1971) s

Tho reports indicate t h a t the earlier survey of reconnaissance status

done maii:iy reveal the essential geological features of the region.

The fasc4.1ating rmdts of these surveys revealed the importance of the

Yotlnger Gra~itc Cmplex as a source of abundant tin mineralization,

T k J s Xed to t h e subsequent need -to establish the boundaries of the

Ycungor Granite Complcx.

The importance of tin mineralization i n the area was reflectsd by

t h e fmquert slirv~ys carr ied out in later years, Between i945 and 1948

a new s u ~ ~ e y carzied out by Mackay, G r e e i m d and Rockingham resulted

i n t h z cs lab2 i skmnt of a more priclse and w l l defined boundaq of t h e

Younger Grmite Complex. It also led to the location of several ring

structures and t h e recognition and study of t h e distribution of alluvial

t s n and colmbitP.

In TYriew of t h e i n c r e a s i ~ g indus tr ia l importance cf colmbite and

N!gerfafs prominent position i n the world columbite production then,

another surv2y 6:' the area began i n 1351 till l(359 under W,N, Macleod,

Ey 1%0-lW t h e manping was extended t o the crystalline basement

hy a k a m of geologists under the supervision of E,P, Wright,

VJrighS (1976) ;:eporkei t h e presence of basalt ic ash deposits of

over 7 meqers underlying lava flows in Jos area,

Turner (1976) showcl tha-t the Younger Granite iniruded the Pre-

Cambrian - L o w r Pa!.~ozoic Oascment of Northern Nigeria i n a N-S

direction and continued northwards into the Niger Republic. He also

pointed out that this direction of intrusion ran parallel t o the main

Pan-African trends i n the basement intlicating control by earlier

s*,ruc=tures.

Horley (1975) and Bowden (1976) carried out studies on the

rrlneralogical conposition of the rocks of the Younger Granites.

A j n h i y e ( l ~ 6 a & bj reported average densities of 2062 g c ~ 3

f o r Younger Granite and 2.68 for t h e Bascrnent complex, The

dansity d~termina t ions shoted higher values f o r the rock types of

Pro-Canbriai? - Lower Paleozoic age w e r t h e i r Younger Granite

comtmpaz ts , This is d d e r t in the mgatlve Bouguer anomalies over

the Yowg6-r Granite stt-ies,

Ras.l'is of some ear l ier yeophysLca!. investlyatiorls (as reviewd

by A:akaiye (1976a) 1, revealed t h e presence of buried channels along

which thz placer deposits from t h e Younger Granites viere deposited.

In the receni; Federai Govermnt of Nigeria 'b?ratsr Dorohole

P r o g r m , soma companies were contracted t o carry out geophysical

work for water bor+.holes in Jos area2 Hmdly any tangible

scientific result has emerged frm t h i s contracts,

Because of r ich mineral resources of the Jos Plateau a x a ,

most geological and geophysical works have been sentred on mineral

exploration, Very I l t t le has been done in the m e of geophysical

methods in the s eaxh of gyound water resources,

GENERTLL G E O L E Y OF THE ARM

2.1 Gen~cal Gee! ow

The area is situated i n the central part of +he 30s Plateau of

Northern Nigeria, covered by h i j u j u sheet number 169 in 1: 100,000 scale

of Geological Survey of Nigeria (GSN),

The area is underlain by rocks of the Pre-Gambrian~Lmr PaLoozoic

Easement Complex mainly mignatitcs, gneisses, Older Granites and tho

Younger Granites of Jurassic age, The Younger Granite Complexes are

donninantly granite porphyries and rhyol ites, S e d i m n t s are restricted

t o valley alluvium, Drainage 5s radial , the head waters of the Jarawa

and Federe rivers r i s e from Jarawa and Shere hills.

Geologically tho area has a daminance of Younger Granites, a

series of not+orogenic intrusives and associated acid volcanics. The

30s Plateau forms the focal area of the Younger Granites province and i s

the principal ccnf.re of t h e associated tin and columbite mineralization.

The early menlber; of Younger Granites typified by volcanic rock Cype?,

largely rhyolites and acid +-.uffa are presorvc3cl i n deeply eroded v d a c

., lhese are succeeded by granitic ring-dykes and plutons composed of

hornbler?cte - b i o t i t e - riebeck2te - granite (~acleod and Turner, 1971).

Minor basic ai~d intermediate rocks are alsc present ( ~ u r n e r , i971),

Macleod et al . (19'71) are of the the upinion t ha t a period of

sroston foll~wed the cmplac mntof the Younger Granites. This erosional

phase =sulted i n the formation of the major morphological units of Jos

Piatcau and surrounding plains. Alluvim then deposited by the Plateau

rivors in some places becam, covered probably in Early Tertiary times

Sv exkrlsive lava flov~s of basalt. Turner (1971) pointed out that these

hxalts have been largely w~athered to clays capped by laterite and

d i s ~ c t e d Ly scbsequcnt erosions. These deposits of alluvia are the

source; of nost of Nigeria Cassiterite productiv and ground water i n t h ~

area.

On tho bas i s of previous works by Bertidge (1971) , Wright (1971)

Masleod and Turner (1971) and Turner (1971)~ the generalised succession

shows a g ~ o i q i c a l sequence of rocks belonging t o f i ve main age groups

of:

(1) Quaternary New Basalts of lava flows and Volcanic cones,

2 Tertiary - Q u $ ~ r n a r y alluvium materials.

2 ) Lover Tertiary 0lde.r Basalts of Lava flows that is now largely

decomposed and overlain by the Tertiary Quaternary alluvia.

(4:f The Jurassic Younger Granites (mainly granite porphyries and

rhyolitvs - all strongly alkaline).

5 The P~c-Cenbrian Lo Scwirler Paleozoic: c~ystallino Basemnt comprisin.,-

of mignatitcs, gmisses and t h e Older Granites (of Pan-African Age! .

2= 2 L - ~ c ~ Y ~ o ~ _ n ~ r + + n$tee_&mp&

-r r~ t h d Younger Granite Complex belongs the Shere Cmplex. Wacleod

and Turner (19?1> dzscribed tho R'iere complex as a small ring-struc ture

superimposed upon thc North-east part of the 30s-Bukuru Yocnger Granite,

Ths Shere cmplex constitutes over f i f t y percent of the rock exposure in

the project, area, It forms a prcminent hill mass, Tho early intrusions

of Shem Complex were gabbrois* But Granitic intrusions dominate the

iater phases of igneous activities. These granitic intrusions show

peralkaline character,

The sequence of magmatic emplacement i n the part of Shere Complex

:si thin t ! ~ project area as shown i n Geological map sheet 169 1:100,00C

of Ge~IogZcaS Survey of Niger5.a (GSN) are as shown below-

! il Raf in Jakin grarite - porphyry (5) (2: 25ot i -k granite and microgranite (%) ( 3 Riekkite - aegirine - granite (W3)

(4j BiotLt? - aegirirle - gramite (Mt3)

( 5 ) Hori-dA~ild~ .- Ppilxcne - Fayalite - granite and microgranite ( M ~ ~ )

( 6 ) Qu~rbz - Olivine - gabbro (M'~) The luca'sions and distribut.ions of these ro:k types am shown i n

figure 2. A detailed description and ?.nalyses of the Shere Cumplex

a ! d its s i u n i t s are contained in Berridge (1971).

Another big unft of the Younger Granite Complex in the project area

is the ;'araqwa Complex, This complex is represented in the area by

larawa .- E o t i t e -, granite ( v ? ~ ) figure 2, This roek unit is located on

the eastern bourdary of the area. The occurence of three pmdaninant

jiihoiogical type5 wi th in the Jarawa biotite - qranftod has been

yeported by Berridge < iT7l). These llthologf ca: t y p s are:-

f . -. ?'' 2 morleratelj: c ~ s r s e inquigranular facies

(2; a mdimn-graj.ned equigranular f acies and

(3) a porphy~; t i c f ine-grained f acies,

The coarse ineqciqxnular facies is located at the central part of the

ccinplsx. To the nor th of the complex is found the m e d i ~ g r a i m d

facies while the porphyritic f i r e g r a i n e d f a c i e ~ OCCJWS the southerrl

ma?:gj.na

Undifferentiated migmatites including viened banded porphyroblastic gneiss. Some schist, amphibolite etc.

Porphyritic biotite and Biotite - Honblendc - granite Quartz olivine - gabbro Neils Valley granite - porphyry Biotite - granite and micro granite of Biotite-Granite Group f I (mdium grained)

Biotite Granite - Group I (coarse grained) 30s Biotite-granite

Rafin Jaki granite-porphyry

Gabbro

Hornblende - Pyroxene - Fayalite - granite and microgranite of Hornblende - Fayalite - Granite Naraguta quartz-pyroxene-fayalite porphyry of Hornblende- Fayalite-Porphyries

Fine a d medimgraincd biotite and biotite - muscovite granite of the Pro-Cambrian basement Cmplex.

Rock types M, OGP and E belong to the Pre-Cambrian - Lower

Paleozoic Crystalline basemnt while tho rest belong t o tho Jurassic

Younger Graqitc Complcxos.

-

FIG2 Geologic. mop o f the oreo shwing rock Vp? C;;iribution ( :cab '1 : 6667

2$3 The Cvctal l i@~asemen.t ;_

The Pre-Cambrian t o Lower Paleozoic crystalline basement had been

greatly ilrirudad a t various times by the Younger-granite rocks, the ch!72

E n s a l t s and Never Basalts, The less affected part of the basement

complex in fie area runs in ME-SW direction, It covers an appreciable

size of t h e arm. Like t h e Younger Granites, t h e c rys ta l l ine bassmonk

t13s various iithological types; both t h e basic and acid rock type are

present,

The najor units of the crystalline ks~men-t include the undiffere*

t i a t e d rnigmatites including vaired, banded and porphyroblastic gneisses,

Schist is a lso present, These uni t s are represented in figure 2 as M.

Ct%r rock t j ~ s are the porphyrit ic biotite and b i o t i t e hornblende - g a n f t e represented by O!P, The porphyritic - b i o t i t e and b io t i t e

hornblende-granite Is located a t t he central portion cf t h e NE - end of the undiffermtiatcd migina-tites. A fine and medim grainsd b i o t i t e and

bio kite - musr;oviP~ granite of t h e Pre-Cambrian Basement Cmplex

dxipnsted as 01T is lozated on the southern fringe of t h e mapped area

~ n d teminatcs i n the east by the bounrlav w i t h the Jarawa - granite complex,

AC the centrs: portion of the migrnatites and porphyroblastic gneiss

is a gabbro rock represented as E i n f igure 2,

To t h e North-most par t of t h e Basement complex i s the Federe

Granbts , a member of t h e Older Granite, It is located between

Shore and Jarawa h i l l s , The Federe Gran i t e forms a nunbcr of masses of

fine t o medim-greined granite within % h ~ ~?:r,eti+.cs,

Foliation 2 e a ----- This 5s a laminated structure resul-ting from segregation of

different minerals into layers parallel to schistosity, Foiiatod rocks

break app~oximately along the fol iat ion planes,

Deformational episodes are represented in the study area by

fo?iations, Foliateon is praninently displayed by all *he lithologic

unl.ts in the area i n varying degree. The rocks of t h e Pre-Cambrian base-

mm*, arrci the Older Granite9 show high degree of foliation which is

expr?ss~d by the pnrallei alliarnnent of micas, amphiboles, xenclitl~s

and quark ve ins , G n ~ r a l l y vertical foliations donginate,

Foliations i n the Fodere Granite are not usually so wll marked as

:.n latter granites, Tna foliations are mostly vertical and trend N S

parallel t o t h e gn?atest elongation of the granite masSss. They are

confoIlFdble with thc folia'iions i n the surroundirg migmatitos. The

nor them part of t ! ~ e Federe Granite shows shallowdipping to horizonial

foliationso

Som off-seto of %heso foliations are observed in places. This

iid!-ratm !.&era1 movement :.-2sultir.g frcm i aa l t ing , Most of thsse

0 0 iollations trend 1~30 -!40 aztmuth, k second set of foliation of less

pronilnetxe t r ~ n d marly N-S direction,

ToSwta and Faults 5 , -- .Jojnts are c m o n and the most affected are the hills. Two sots of

.joints, ~ s a r l y orthogonal a r e recognised i n the area. The major .joir,ts

t~ecd N &i1° \A!. The other set runs North-South. Both sets of j o i rhs are

f-..m near ~ r e r - L i c d to verticalc The rives channels, streai IS and i i ~ h t

f o ~ x t a t i o n in the area follow the joints, Most j o i r t s in the lowlying

are1 a m f i i h d wi th recrys-tallized quariiz. Some recrysta l l ized quartz

veins m a s a m 11p t c 30sm i n width,

The existcnco of f a u l t s have been represented i n the area by t h e off-

s5;ting and displacemen-k of some quartz veins. Some displacements are

upto 4.3crn. The analysis of both t h e magnetic and resistivity CtlCmal fe5

lend +thevselves t o thc bnterpretation t h a t t h e area must have suffered

some faulting, These f a u l t s are not observed on the ground surface, but

t h e i r presence cannot b ruled out,

3,l CbJe_c,t:>~ of the survey

Tho incessant problems of domestic, industrial and agricultural

water sl?ppl:r In areas of hard rock i n the coun+::y req:liro !,mediate

soluklon, Most boreholes found so far i n these areas were drilled

without an;r pre-g~ologlca?. or geophysical investigation, The result is

a ~ e r y low success r a t i o with a great loss in "man-hour" and fund,

Ti12 project was aimed a t using geophysical m t h o d s to locate,

delineate and assess the groundwater resources of Fobour areao This

cbZective was t o h? bshicved using e l e c t r i c a l resistivity and magnetic

ui-ospecting methods,

The clects ical roslst ivity and magnetic signatures of structures

and envisonnents vhich are favourable to hourlng and transmition of

wz.ter exploitable in economic quantity are easily recognizable, The

di : : tinct resist!.v!-ti contrast. betwen mter saturated overburden and

k d r o c k makes .msi st i - i i t y m t h w a prt ncipal exploration method for

tla'v2re LOW resistivity values i n electrical profiling and low rnag:e-tic

r a d i n g s across an area are directly related t o the extent of w a t h m i n g

?nd w!ater satmat<-on of the place. The small size, the ease i r l

handling and the low labour requirements of electrical resistivity and

magnetic in s t rwnJ- , s are other added advcintages to methods used.

Groundwster exploration and exploitation are mostly limited to shaihw

depth. Resistivity sounccing has a better resolution than other

geophysical methods for shallow depth investigation* These factors

have made elec t r ica l res5stivity method the most prominent geophyqical

r ~ t h c d for gzoundwater exploration.

Unlike t h e e l e c t r i c a l method, mag;~et.ic method is s-till a t t h e

t2infazt ' ' s t age a s a geophysical method f o r water explora t iono Outside

t h e use i n mineral explora-kion, i ts use i n o i l explora t ion is l imi ted

t o reconnc5ssance s t a t u s f o r de l inea t ing and es t imat ing t h e th ickness of

sedimontaqr p i l e over t h e basement. I n magnetic . mcthod of s V m e y

areas of t h i c k sedimentazy p i l e appear a s magnetic lows, This magnetic

p rcper ty is used t o d e l i n e a t e a reas of t h i c k overburden f n hard rock

t e r r a i n , Thick r e g o i i t h , buried channels, f a u l t s , highly jo in ted and

fractured zones are t h e poss ib le aqu i fe r s s o r t f o r i n hard ~ o c k t e r r a i n ,

Thcse poss ib le water Scar ing s t r u c t u r e s appear a s magnetic anomaly

low, The a b i l i t y of magnetic method t o o u t l i r e these s t r u c t u r e s makes

magretics a usuful yeophysica'. method in water explora,tion.

It i s hoped t h a t in teg ra ted r e s i s t i v i t y and magnetic methods as

used i n t h e study would produce b e t t e r r e s u l t .

3e2 Jxt.~_n_&aJ-.ion arid f i e l d procedures

Two bas ic instruments used were

( i) 1\11 MEM t x r m c t e i - W

Ii13 A J a l a n d e r Fiuxgate magnetonleter,

3 a ' L o l E~r-yxnetey

The t a r r a m t c r used fo? t h e survey was an IJEM Terrmter (SAS 3m

model, f igure 4a). The SI'S s tands f o r S igna l Averaging System a method

whereby consscutivo readings a r e taken automatical ly and the r e s u l t s are

a v ~ r a g e d continouslye The terrameter SIS 30C contains thme matn U\ ti. ts;

t h e t r a n s m i t t e r , t h e r e c i c v e r and microprocessor, These t h r e e main

u n i t s a r e housed i n a s i n g l e cas!ng.

I n t h e r e s i s t iv i - iy survey mode, i t comprises a b a t t e r y - powered

deep pene t ra t ion r e s i s t i v i t y meter with an out put s u f f i c i e n t f o r a

current electrode separation of 2003 meters, With discrimination

c i r cu i t ry and programming incorporated i n t h e system the reciever

separates IX voltage, se l f potent ia ls and noise from t h e incoming

signal and measrzos voltags correlated with t h e transmitted signal I

current*

The microprocessor monitors and controls operation, calculates

v e l e c t r i c a l resistance (T) autcnnatically, and displays the r e s u l t in

d i g i t a l form i n ohms or milliohms. The range extends fran 0 3 m a

t o 1999 k%nd can be extended down to 0.02 II&L with a booster,

Measurements were taken with the cycles selector switched f o r four I

automatically averaged readings. ~ I

For data r e l i a b f l i t y , safety of t h e equipmen+ cer ta in precautionary

measures wra taken. Some of tho precautions included:-

(1) Hamwring t h e electrodes deep i n t o t he ground t o ensure good

contact;

(2) Ensuring tha t t h e reels of the wires were always positioned

with t h e axi.5 of symnetry perpendicular t o the traverse

t o minimise coupling and induction;

(3) A l l o w i n g the wires not t o cross o r touch one another;

(4) Taking measurements i n four automatically averaged readings

(occassional ly sixteen automatically averaged readings were

taken) ;

( 5 ) Running the traverses In straigh-; lines;

( 6 ) Keeping the reco-ding im*rmnk and the potent ia l cable

reel a t l ea s t 5 meters away from the l i n e of traverse;

(7) Looping the current cables t o firm objects t o prevent pull ing

down t h e recorder while moving with the cable qr generating

high stress o r tension a t the point of cable contact with the

3n2.2 y=netometer

The magnetic instrument used was a portable Jalander Magnetmeter of

a f l w g a t e -- type with type nz 6661 and i n s t r m n t no 7447 (figure 4) ,,

Some of the important compommts of the instrument show i n f igure 4

include: - push bottom whish controls the on and off of the instr~xnent when

taking rneasurcrnents,

po lar i ty knob which 1s used in determining the magnetic pota i iky

of t ho z>.a t ion I %nsi-ttvity s e l e c t i o n knob which ranges from 1 to 5 and used to

within keep the pointer d e f l e c t i o n A ' the scale and the ranges used

i n converting the f i e l d readings t o gamnas. i The bubble or bullqs eye which has to be centred during each

reading. I Measurement t a k i n g involves s e l e c t i n g t h e right poiarity which is

indicsted by tk po:nt?rs def l ec t ion towards the right into the calibca-t im I

region rthen the push bufton is. pressed i n t o polarity knob. S e n s i t i v i t y

selwLion knob is sa adjustai that the pointer does not go off the scale.

- i h ~ n the mxtsuremrit is taken with "f3ull-eye" bubble centred,

Csr ta i n precautions as ( i) centring thz "Bull-.eye" bubble,

(2) t ak ing up t o three readings for one s t a t i o n and the meav taken,

(3) avoiding c b j e ~ t s t n a t could affect t h e i n s t r m e n t reading in t h e

vicin:i.ty are o b s e s ~ e d during measurementsh

Precision of the readirqs frm this instrument ranges from 0 3 g m a z

Lo 12,5 g m a s w i t h most types being close to 5 ganmas, Dobrin (1976)

p509,

Figurc 4a illustrate how t h e f i o l d is measured by elements of t h e

flux-gate magnetometer, Two p a r a l l e l cores, each with a magnetization

curve of t h e type shown a t t h e upper left , are a l l igned with t h e i r axes

i n the d i rec t i f in of the ea r th ' s f i e l d . Primary c o i l s i n series

mzgmtizc t h e two c o r e s wi th the sane f lux density but i n opposite

d i rec t ions , s ince they arc wound opposi te ly around t h e rcspect iva

corcs. The e a r t h ' s f i e l d r e in fo rces t h e f ield set up by one of tho

c o i l s and opposes t h e f i e l d of t h e other . Each c o i l has, i n addi t ion ,

a secondary winding, the two secondarias being connoctcd t o a voltmeter

t h a t reads t h e d i f f e rence of t h e two outputs.

For t h e magnetization of a s i n g l e core i n the absence of an ambient f i e l d as when tho core ' s axis i s nonnal to t h e earth f i c l d ,

thc sinusofdal exc i t ing f i e l d H (curve a of fig 4b) d r i v e s t h c core

past saturation at thc t o p am1 bottom of each cyclo (as shown i n c u m

b) . The secondary voltage is proport ional t o t h e r a t e of magnetic

f l u x *

If an ambient f i o l d is introduced which aids t h e magnetization

frm thc e x c i t i n g current , t h e sa tu ra t ion point is reached e a r l i e r i n thc cyclo than it would be in the presence of an ambient f i e l d apposing

t h e e x c i t i n g f i e ld (curves d and e). I f the vol tage ou tpu t s of both

coil8 are connected i n op;iosition, t h c r e s u l t a n t output (curve f)

consists of p a i r s of pips which arc proport ional t o t h e ambient magnetic

f i e ld .

This pip is registered as field reading. The f i e l d reading is

convorkccl t o appropriate value i n gammcs using a conversion table based

on the range used during mcasurc:i7cntr

3.2.3 Fie ld procedures

The f i o l d work was covered i n two phases, The first phase was of a

reconnaissance s t a t u s . This w?s done i n March, 1983 and lasted for a

per id of one we&. A t this s4age of t h c work, c l e c t r i c a l sounding

s t a t i o n s and l i n e s of p r o f i l e e f o r t h e e l e c t r i c a l 2nd magnetic

measurements wrc selected and areas of interest delimited from

appzrently unrewarding area,

The second phase which constituted the actual survey, was done i n

September, 1*3+ In Fobour, five electrical soundings were carried out

using t h e Schlumberger symme'trical spread with maximum A 0 separation

of 1,4W mters. The spreads were oriented obliquely t o t h e general

t r e n d of fractures and j o i n t s observed in the area. From a pre?.iminary

f i e ld i n t c - r g ~ s t ~ b i o n of some of these souildinps, an eiectzode spacing

of 5 h 'or Ihe Wenner configuration was considered appropriate for

a f o l l o w u p eiectrical profiling. Magnetic mea~urements were also

taken along the lines of the electrical profiles at 50 m intervals ,

Kith this arrangement common station points were established f o r the

elcctr ical and magnetic readings,

A to ta l of t w n t y one traverses wre taken, s i x electrical soundings

of spread :angthc 300 meters to a maximum of 1,400 mtcrs, Seven

e?ec t r ica l p r o f i l j ngs of lengths 603 meters t o 1,400 m and eight

m,zgr.~t i r ; t~air~xscs of lengths 400 meters t o 2,550 meters were also

t;lksn, The t o t a l length of the traverses amounted t o a-er 23,033 meterst.

Majority of t h ~ traverses run in NE-SW direction and additional

traverses wre l a id to cross these, The f i e l d orierrtation and exact

posi t ions of these traverses are shown in figure 3 0 The electrode

separation of 50 m was kept cons*,ant while the electrodes wera moved

along a straight line i n one direction during the resistivity profil ing

mc3asuremen"ts. In addition t o these M%SW traverses, two magnetic

traverses cut these magnetic and electrical prof i l es , h,!easurerner.ts

along these ' e re taken at 100 mters intervals, The NE-Slil orierrtation

Urctticol sounding stations (EW

- Line of e l e c t r ; c d ~ c f i l ; ; . ~ EP I ,

- - - Cine nwe~ t r o w s ? ( M W ,

HC - Heo!th centre.

Sch -!%hod. ,- a Recommended s i t ~ .

waz chosen t o h a w a t ransverse r e l a t i o n s h i p wi th tha strike of j o i n t s

and fractures in tho area,

O m e l e c t r f z s l sounding was done very close to a water bore-hole zt

Jerigere near Jos. !4ith the known s t r a t i g r a p h i c sequeqce i n t h e area,

it was hoped that the interpretation of the sounding should o f f e r some

contro l arid guid? fox t h e correct in te rpre ta t ion of the measurements

taken around F o b ~ u r , ~

The &ect r lca l soundings curves wre intswreted by par t i a l cume

- matching. he ceoe?ectric sestion of the soundings arc! shown i n table

7 and f i g u r e 52.

3.361 E I _ e ~ t ~ ~ ~ ~ ~ i ~ ! i n g .(BE?)

The spread i? oriented 230' azimuth and located XXm from Iyanb

Fohour junctio?, F:;.g. 3.

-- lhe maximum cursenC electrode separation is XWh. The f i e l d

appzren-i; resis.i;lvii;;- ~ead2ngs a w shown i n t ab l e 1, and apparent

r a s i s t l v i ' y versus nai f current electroda apread lograthrnic p l o t is

cho-m i n figure 5, The geeelectric para~eter as determined from

g x p h of f igure 5 by partial curve matching shows three layars overlying

the basemerl-t, This is also shown in tab?: 7,

The in te rpre-k3on shows an overbus. ,:en of about 10% t h i c k ovc?lyi;lg

t h e Ixd rock , From the rllrface, it shows a top layer of about 4m 'chick

and resistivity 82Q;k m which i s t h e dry l a t e r i t i c t o p sof 1. Underlying

it nra the se:;ilnd and third layers 15m and 8th thick respect.ive:v and o f

the water sa tura ted zone. Water level in n near by l i n e d open well

measures about 301m from the ground surface. This water is believed to

h3ve come frm t h a va:dose zone with thickness 1% and r e s i s t i v i t y of

about 1 4 5 c ~ ~ t .

Between t he lower boundary of t h e third layer and the underlying

be&-rock is marked by a high resistivity contras t , The underlying

msbtive lzyer of the order of 558am from depth of 157m is

i n t e r p r ~ t a C e d as %ha unweathered and possibly unfractured b~sement.

3.3 *2 g,l;eek.cal S mcli nq (@A)

The sounding s t a t i o n is located about 800 mctezs south of iyaw

Fobour junct ion a t a cross-road, It is oriented in a N-S direction with

an azimuth of 20'.

A maximwn spread length of 1,400 meters via$ covered. The apparent

resistivity readings are shown i n table 2 w h i l e t h e sounding curve is

shown in f i g w e 6 , The geoelestric sec t ion shows three layers of total

t9ickness 4? m.',qrs unclsr la in by the basement. This is shown in table 7 ,

A tc'p layer (dry l?'ceritic soil) 7 meters thick with a resistivity :-f

24OiIr5t.m is under le in by another layer 7 meters thick and having a

rosis'iiviJ~:r of 8~'3-?;_ril, The second layer is t h i n n e r than its l a t e ra l

equivalent in EZ,l arld probably contains l i t t l e o r no water as revealed by

its relatively high resistivity* From 1 4 i ~ e t e r s t o 49 meters is a very

lcw resistive medium with a thickness of 35 meters and an av:?rage

resistivtky of 42.. ':. T 5 ~ s horizon is believed to be a coiitinuation

>f the t h i r d laye: of ES.1 but thins southward i n t h e m:,pped a~rea.

3t3 low resistlvzty a: i n t h e case of t h e t h i r d layer of ES.1 prob?blq1

0 7 - 7 - , I I I I I I I I -- T I I , , ,

I-

3 A 3 ,Electrical soundinq (€,S,3)

It is located 1,300 meters from Iym-Fobour junction towards

Fobour siesion. The spread is oriented 205' azimuth (see figure 3).

A maximwn current electrode separation of 4N meter? was attained,

The resistivity readings are shown i n table 3, while the sounding

cu-rve is shown i n figure 7.

The fnterprsta.l.,ion of the graph shows a geoelettric section of

t h r e ~ layers underlain by the basement, Their respective thicknesses

and corresponding resist ivit ies are shown in table 7 , The layefs

above the bed rock have total thf ckness of about 56.1 rwters.

The sequence from top shows the top soil 1, l meters thick with

a resistivity of 4501crn. The secortd layer has thickness of 5.0

meters a d i s charactaised by high resistivity of m. Then

c m s a third la;rcr 50 meters thick with a resistivity 257JLrn.

T h i s third laye: i s underlain by the bed-rock of high resistivity o f

over 50(nrtrn, i3ls h!gh resistive bed-rock corresponds t o the

unwatheced and possibly unfractured basement.

Thr, unusually high resist ivity of t : ~ e second lager is interpreted

as resulting possibly from faulting and or mineralizatlm of

resistive materials such as quartz along t h e faul t plane. The

hf i l l ings of quartz veins as observed .long fractures and joints

plams i n the area and arourx! minitic, sites tend t o support suct. a

possibility.

Resistance R

(+I

303,4 Eefir-cal soundina (E S ,4)

' The sounding s ta t ion i8 located 6% West of ES.3, The spread

i s oriented 200' azimuth with a maximum separation of 6Xh. The

apparent resistivity values are shown i n table 4 and the graph of

resistivity versus the separation i n figure 8. Thicknesses and

resistivities of t h e various layers are shown in table 7. The

geo-electric section shows alternating high and low r e s i s t i v e

layers stndlar t o that of ES.3,

Frm the ground surface are tho followingz

1 2,311 top soil of resistivity 830am

(2) a sacond layer 8+05m thick and r e s i s t i v i t y 1245fi.m

(3) a third layer of interest of thickmss 0Qn and resistivity

415.5;; m.

F m a depth of about 91 meters is the bed rock believed to be

unweathered resistive part of the basement. The resistive

second layor is suspected to b a continuation of the second layer

i n ES,3 ar.d p o x f b i l y marks the trace of the inferred fault.

The sounding station is located behind Fobour Primary School

and oricrrted 230' azimuth. It has a maximum length of 6COn, f he

exact iocation and orientation is shown in figure 3.

The apparent r e s i s t i v i t y measuremnts are shown i n table 5 and

the graph of apparon resistivity versus half the spread length i s

in figuxe 9,

The interpr- tation reveals a serries of thin layers of 1-41,

1&, d,%, and 40.% overlying the infinitely t h i z k basement with

Resistance I:

(a)

Apparent Rss+istlvit~ (i iJ- m)

970.75

770.32

7945i

853,73

1071 ,?8

1031.12

620,15

485.90

379-61

405,265

me845

c169,14

487-73

E E a R I C A L SOUNDING 5 (ES.5) DATA

LXATIt7hl: EEHIN3 FOBOUR PRlh4ARY SCHOOL

res;stFvitLs of ? 8 O ~ - ~ r n , 109,<js, 3220 d - n, 1093)-*m and 20719- n

respestivtliy.,

Fron table 7, it is apparent t h a t the area has a l a t e r i t i c top

soil of ? t c ~ %I or more underlain by 5 t o 1% +I;ick udersaturated zone,

These tw layers are separated from the bed rock by an exploitable water

Sdaring horizon with mai<imm thickness of lOCLn at sounding station ES.1,

This exp?o5:hb:e horizon thins down towards ES .2 and ES ,5+

3-3,6 j3;,i&.~Lval sounding (ES #6)

T h i s soundir~g w3s done off the project area but in c? similar

geologic setting, It wa9 located cf ose t o a bore-hole of known strati-

araphic soq1.lence to act as a control.

The z~sistivity maclings are shown here i n Table 6 ; the graph of

resistivity versus half current electlode separation is shown in.

F5gwrs 10,

The ii~i:erpr,:tation of the resistivity curve shows a thzee layer

strttct.are. F:mi t h e surface are layers of thickrtesses 1.2Ckn, 9,h,

1313 2nd t h e basemeat of i n f i n i t e thickness with resistivf ties l l 2 - ~ ~ r n 9

163.f5, rn, 137~2 m, and 2749n-rn xespectively. The gebelectric section

.:mp~as satisfactorily with observed stratigraphic sect ion during

drj.llingm

The sequence of layers as observed during drilling obtained from

bore-hole records F,D.W,R Jos is shown below

0 - an = topsoil

2 - 10,5111 = sand

10,s - l?-c5m = weathered granite

l l c5 - 14m = w a t k x e d granite and sand

!?EtTLiCAL SOUNDL-ffi 6 (ES.5) DATA

LOCATYON: 1% FRCM F,D.W,R. BORE-HOLE AT JENGERE (The soreact was alligned parallel to the road)

TABLE 7 -- PZSUIITS OF ELE(JTR1CAL SOUNDINGS ES1-6

SOUN!lIEi STA i Thickness of rious layers I Resistivit~ of various lay~rs I L- , an$\ I - .--

bedrack Resistivi of Tapable Horizon

107 558 nz 2 8 3 layers

49 800 nz 3 layer

56.1 5140 n; 3 layer -. . . -

1 - 90.9 375+.. not attractive

47 2071 I no 3 8 4 layers 1

.A . .

23.2 2749 1 no 2 8 3 layers. 1

14 - l7m = fractured gran i te and weathered

17 - 18Jm = micacsous sand

18,:5 - 2:m = fractured gran i te

21 - 46m = very hard fresh gran i te with very few fractures. . From t h ~ f i e i d curve interpreta t ion and the lighologic log, the f i r s t

Zayei- from the sounding corresponds t o t he top s o i l , the second layer

i s reprcsent.ed by 8,5x th ick sand. The wathered grani te from depth of

10'3 meters t o 21 m t e r s corresponcls t o the t h i rd layer of f ie ld c u m .

3,3,7 Fieci;qica.Palrof jj 1 9 na i EP .I)

The profile is oriented 115' azimuth and runs transverse t o other

e:lsctrical p rof i ies i n f igure 30 I t covers a length of 8%. The

r e s i s t i v i t y and the corresponding centre of spread distdnce values are

shown i n tab le 8 while the graph of the r e s i s t i v i t i e s versus centre of

spread is shown i n f igure 11.

A look a t t h e EP.1 graph from NW end shows a r e s i r t i v i t y low frm

the beginiag of the p ro f i l e t o 40C)m. It's minimum is regis tered around

l m The resis-L?.irj.ty increases gradually t o a maximum a t 75Ckn witti a

sharp drop a t 70(Xn, The r e s i s t i v i t y low i n the region of 0 t o 4Cam

is interpreted t o indicate a water bearing horizon i n an area of deep

wea.tharing o r buzied r i v e r channel f i l l e d with water saturated a l l w i a l

matezial, The broad f lanks of the curve rnhy indicate a wide river channel.

ELECTRICAL PROFILE 1 (EP,~) DATA

LZATIO!L': THE SAVE IS MT.2 3 ~ ~ 3 1 hr; : 115'

Distance (m) Apparent Resistivity

p+h) 0 iDI-end 254, 47

50 242.85

. ',@!I 4634

150 88.54

200 m, 12

250 166 650

300 261.37

350 294.37

400 301 m59

450 372659

500 454e90

530 552.29

600 1 551.66

650 I 647 17

700 433e54

750 731 a99

800 414.06

SE-end. 306.95

I I I - 1 I -- I N o!? a60 L 00 b o o i 800

cent re , o f s p r m distance !m)

FIG11 Res is t iv i ty curve of E P i

3,3,8 Eiectl-ical Prof i l im (EP.2)

This p m f i l e EP.2 shown in figure 3 is oriented 245' azimuth and is

6 0 h long. Table 9 has t h e s tat ion distance and resistivity values,

?he graph of the resistivity vezsus centre of spread distance is shown

i n figicra 12.

From the SW of th5 profile, tbre i s no abrupt change i n the

resistivity betwen 5Qn and !XKh except some minor fluetwtior'ls that

show gradual incrcase in apparent res is t iv i ty , B s t ' e n 500 avid 5%

an abrupt, s:i,ange in resistivity to a very low value appears. Th i s to

resfst ivi ty anomaly appears related t h e obsemd a ~ m a l y i n C~400m A

of P,l of figure 11.

3-3.9 Electrical Profilinq (EpC3)

The profile is oriented paralled t o EP,2, located a t 20rh south of

9.7 . The apparent resistivity and centxe of spread distances a r e

showi I n table 10 arid figure 13 shows the graph of apparent resistivity

A SVdcNE clescri;?tfon of EP.3 shows a rt31atively M g h res is t iv i ty value

from 0 to 13Q-n. Betwen 15U and 20an shows an abrupt change I n

a.p~arent resistivity w!-~ich continues with gradual decrease -from 'LOOm

t o across 800ms 1:n~nl

The consistency in thentrend of the resistivity ananally low as

Ind?.sated i n EP.1, 2, and 3 lends itself to a structurally corrtrollod

anom ly source,

TABLE 9 ---.--

ELECRICAL PROFILE 2 ( E P . ~ ) DATA

LOCATION - rJJl BEARING THE SAME AS IN W.3

>q-- Distance (n) Apparent Resistivity

sL,

EXCTRICAT, PROFILE 3 (EP, 3) DATA

LKATIOIJ P,ND BEARING - THE SAME AS IN W . 4

Distance (m) Apparent Resistivity

--- OSW-End

' 50

100

150

200

250

300

350

400

450

500

550

600

55c

700

750

m0 IP End,

I n s t . i : w n t Reading (Resistance <-R>j

3A10 ,Flectrical Prof i l im (~p.4)

The NF end of EP,4 is located 1% east of tho NE terminus of

8?,3. The trend of the traverse ( E P , ~ ) is d~v ia ted to a bearing of

210' to avoid scme obstacles, but a general SW-M trmd is still

maintained, The traverse is 10Xh long.

Fig, 3 shows tne location of the traverse on the surface. The

centre of spread distances and station readings are shown in table 11,

Figure 14 shows the graphs of the apparent resistivity versus the

centre of spread distance*

The SW--hE graph of tho apparent resistivity shows an anomaly

b2twoen 13Qn ami POO~IL betteen 350 meters ancl 650 mters there is

no appreciable variation in resistivity. A resistivity h'lgh is

observed bo-kwecn 790 r,,eters and 900 meters with its peak at €03

meters, ?ran 95C meters t o the NE end of the profile another

resistivity Losv shows up, Field observations show that these

resintiv~.l.f M ~ h s correspond t o areas of th in regolith and areas of

exposad basecent,

3+,3.,11 i;'J1ectricalL.-?~f~7.i:w (EP.5)

kF,5 is separakd from D.4 by 280 meters ancl runs paraliel t o

EP.4, It is 1200 mtess long, Figures 3, 15 and table 12 show the

Zo.:ation, qraph of tl~e apparent resistivity versus the centre of

spread, and centre of spread distance and corresponding resistivil;{

Z G S ~ ~ C ~ ~ V O ~ Y ~

The SW-NE graph of the measurements shows minor distortions

batwen 50 meters ar.J 200 meters and an abrupt resistivity low

DLstance (m) 1 Apparent Resistivity I n s t r m n i . Reading I ( a m ) (Rcsistanc:e)<n>

.C.?&LE - 1 -- ----A:':

S?2ECTRIC.4.L PROFILE - 5 (EP.5) DATA

'~.OC:J-~~:!:!Y A I D FEARTFG - THE SMIE AS IN kP,..6

Apparent Resistivity ~irtanse (m) 1 - 4- - CccZw) -

Instrument Reading (Resistance <5)

- . - ---.- - -

betwen 250 meters and 500 meters, uniform r e s i s t i v i Q with mi.nor

f h ~ ~ c i e a t i o n s from 600 meters t o 900 meters, then a rise a t 950 meters

wIlich f a l l s gradnally with minor d i s t o r t i o n s from 950 meters Y O 1050 meters

dis-Lame,,

303812 . Electr ical --------- Prof i le ( E P , ~

The bE-end of t h e prof i le is located 300m after Fobur P:rimary

School on t h e road t o Kudedu, It is or iented par3 l le l t o EP,5 and

co-iers a distance of 70C)m (see figr3) , The centre of spread distance

and c o r r e s p o d h g apparent resistivity values are shown i n t a b l e 13,

The graph of resistivity versus the centre of spread distance i s shown i n

f Zgure 15.

The length of the p r o f i l e is characterised low and i-elativel~/

unifonn resistivity valuec. This low and cons i s t en t ly uniform resistivity

of the p r o f i l e probably r e f l e c t t h e hydrogeological condition of the valley

along which t h e profile runs paral le l to i t s axis , Since water table

Eol1v;ss p a r a l l e l t o the topography of an area, t he a x i s of t k i s valley

mo:.;t pzobably corn-?.sponds t o a zone saturated with water, Iiclwever t h e

I h a a r i t y of t h e vailey and ?.ow values of t k i resistivity could be

con",olled by a ~ ~ h s u r f ace strucYLure.

3@3,13 S!.ectric;i! Prof j. 1 im (EP,7)

5P.7 is iocated 15On south of kT.3, or;ented parallcl t o EP-3 and 75011

long, The centre of spread distance and t h e corresponding apparent

r e s i s t i v i t y values are show. in t a b l e 14. The graph of t h e :.-xi stfvity

versus centre of spread distance is shown in figure 17,

: 3 f ~ . Distance (m) Apparent Resistivity I n s t r m n t Reacting (AM) .- -I- (Resptance JL j

I c -0-, I 0'- 0- I- /

- 0 - . \ ** - '9 I

_ - - - * * - 0-

I I I I

\,oL# - *- - O.- -0-- 1 P 1 , -F-*-,

200 4 00 6'00 , NE centm d spread distance (m)

FILCXRICAL PROFILE - 7 (EP.7) DATA

L~K;ETIOii -- ?,%I from Iyarn - Fobour Junction REARIN3 - 245'

The 3J-NE graph of t h e resistivity versus spread distance data

shows very high r e s i s t iv i ty values from 0 t o 250111, From 25011 to 300m,

t lwm i s an abrupt drop i n t h e r e s i s t i v i t y value to about 5 Q h r

--_. A-LW 3OCkn t o 7o&f1 shows lots of f luctuat ion I n t h e r e s i s t i v i t y values,

and from 7 0 h to 750m a sharp drop i n the r e s i s t i v i t y is noticad,

3t4 ------ Mametic Inves t i aa t ions

In addition t o t h e magnetic traverses ruq on the same lines and

bearings as t h o electrical . resistivity p r o f i l e s , magnetic measurements

of P@,1 were carried out along the road t o Fobour mission. Thoir

lengths ranged from 400 meters t o a s much as 2,500 meters, k t o t a l

length of about 900Ckn was covered i n magnetics. The orientaA;ians of the

profiles axe shown in figure 3,

Except fo r FJG'al and W,2 where magnetic measurerrents were t aken

a t intervals of IOC mneters, measurements were at 50 meters intervals

along the re:.? of ",he profiles. (ie MP3-MP.8jm

The swvey area is i:ot of regional extent a ~ c l vertical magnetic

In.F.cnslty nomral. coxec' t io;x were consf dered unnecessary, Rase stac ions

WE r.e-ocxvpied evt3x-y two !?ours and measwements takm* From these

n~asmments conl~cnsation f act.or fo? ef f ~ c t of diurnal v a r i a t i o : ~ was

deternine and the necessary correstion applied to t h e f i e l d measurements

wh~re necessaryt The regional vert ical mqnet ic in tens i ty was obtained

5y fi~?dir;g t h e average of the whole f i e l d measured values, A man ~ ' . I ~ u H

of 1500 gammas obtained a . regional was suhstracted from each and every

one of t h e obse rwd f i e l d values t o obtain the magnetic anmaly, The

reduced values are shown i n tables 15 t o 23,

The values of the observed vertical magnetic f ntensity (4a and

verti ca? nagnet i c in tens i ty anomaly (4 2-4-2) )1 &who ~Eirepresents

%ha regional, are ploted respectively against the distances f o r each

of t h e magnetic p rof i les (see figures 18 to 25).

The verHcal magnetic intensity fo r the area varies f r m as low

a s 6C5 gammas to over 3000 g m a s with a mean value of aboui: 1500 gaminas,

The graphs of tha anmalies show no dif ference i n shape wit'? t h s

graphs of .the:lr corresponding observed f i e l d values. The o-?ly notlceab?e

differencc 1:; t h e apparance of negative and posit ive anomalies a t some

points along the profile.

Satpathy and Kanurqo (1976) noted t h a t hard rock terra. lns show l c ~ w

total magnetic inter.siVky over th ick weathered overburden, llenkel and

Suman (3.377) a t t r ibu ted l inear magnetic m i n i m u m to l i nea r ,Fracture zones - ti,

a i ~ d sa id t h a t t h e s e l i nea r magnetic minima could be resul.; of oxidation A

and hydra%lon along the linear fracture zones, Similar magnetic

sigmtures obsesed i t ; t h e f i e l d measurements combined with results

froa t h e rssisb'.vi ti- ?u.rvqr i s l ike ly t o give a x l i a b l e in-:erpretation,

T h i s traverse, 1300in long, was carr ied out along Fobou.:: Rcad f r a

-. L-/an -- Fobour juw+,ion, Values of the v e r t i c a l magnetic in1;ensiti

..L (&z) and tha mx~ne'iic anmaly in tens i ty (Qx-/Jz) are s h o m i n

t ab l e 150 The g r t p b of vertical magnet3.- in tens i ty and t he resicit14

anonaly versus distances are shown in ffgute 18,

A West-East description of t he residual anomaly pro f i l c shows tvm

n2gative anomalies from 3903 to 7OOm and from 1250~1 to the end of the

prof i le . It is wo?thy of note t h a t the negative anomaly from 3CCm to

Instrument '

Range Reading

Readin< i n G m a s

1210

605

21 17

2016

1411

1411

1411

1210

141 1

1.814

1813

1G13

10 13

GC'4);n coincides with the very low resistivities recorded i n EP.1, EP.2

3rd E P 3 , Betwen lOOm and 20h, and from 8 0 h to 1200m show positive

rnagnetlc ananaly,

.7,4,2 Maqnetic profile (MP,,2)

The profile transverses the other magnetic profiles. It. i s over

20Ohn long and oriented 115' azimuth. Readings were taken al: lOGm

intsrvals, Table 16 shows the values of f i e l d vertical magm?tic

Intensities (A2 ] and their corresponding magnetic anma'iies

4 - : y ) The graphs of tho vertical magnetic intenrsity and *s, 4.

residuals agains t dishnces are shown i n figure i9,

The vertical rnagnetlc intensity graph shows a relatively uniform

value with some minor distortions. 7 t t a i s also ref lected on the anomaly

graph i n which a unifo:m negative anomaly appears from 5mn on i t s W c n d

through tho length of the profile except some minor distort ions a t

700;n point and fey: others a t 11'XXn and between 190Ckn and 22COm. To

the hrlid of 400171 i s =1 posit ive anomaly, The posi+;fve a n m a l i e s a t the

Western end of !P,L and NW-end of MP.2 p~obably zorrespond t o the

bomdaxy between the Younger Granite Cmplcx and the Pre-Carbrian

basement

The bearing arid location of this profile are the s a m as that of

E P a 2 a It is a 700m long profile and measurements wre taken a t SOL.

irr'iervai.

The position and orientation of the p r o f i l e are shown in figure 3 n

The values of t h e vei%ical magnetic i~ensity and the residual anoaaly are

shown in table i7. The graphs of the rnagmtic i n t e n s i ~ v and the magnetic

- .,.- Distance

1 . \ --\.:2!- - - -

0 Base

100

2co

300

400 503

690

700

800

900

1000

1 loo 1200

i300

1400

1500

1600

190i)

l3Od

1909

20CO

2190

2390

2300

24.30

2500

r! Base -,.-- -

Value i n Gammas ----.--

605

1764

2866

1764

1764

1260

1260

1814

1411

1210

1213

1411

1210

1210

1210

1213

1210

12io

- -* Residua,?. - x ---.-.-. -995

254

560

264

264

-240

-243

340

-85

-290

-a7

-85

-290

-290

-4290

-287

-290

-290

-290

-4w

-895

-391

- 1097 6 ;ow -240 - 1097 0.883

--

" I - I

momaly are also s h m i n figure 20.

The profile's magnetic intenqity values are generally Icrw. The

residual magnetic anomaly is negatlve Wtroughout the profile but has

several minor distortions. The distortion is interpreted as magnetic

signature of the subsurf ace topogf aphy of the wmerthered bar,enaent

3,4.4 Mametic profile (MP.4)

This 95Ch1 lonq profile has the sane bearing and location as EP.3,

The vctitica? magnetic intensity readings and the residual a~omaly are

shorn in table 18* Figure 21 shows the graphs of tho verticai anama1.y

against distances,

The profile snows a set of uniform and low vertical magnetic

5.ntensity ramly greater than 1000 gamnas, The residual anrmaly is

negative throughout the length of the profile. Like the vertical magnetic

intensity, the residual anomaly is uniform throughout with rome minor

distortions,

3,4.5 Maeilntisprof i?:2 (MP.5)

The measured magnet1 c (vertical) intensity and the red iduals ;re

shown in table 19, the location and orientation of the traverse is shown

i n figure 3. The graphs of the residual a m l y and the w!lrJ,ical magnetic

intensity are shown i n figure 22.

The profile, 10% long, and oriented 210' azimuth hap a consistent

unifonn low negative magnetic anomaly from 550m to 1100m. A marked very

low negative anmally i s observed between 0 and 2OCh with few minor

flutuat-ons, Betwen 250m and 40an shows a positive magrmtic a n m l y *

TABLE 18

MAGNETIC PROFILE 4 ( F P . ~ ) DATA

Distance (m)

Instrument Reading

T irne

10.40

10.38

10.36

10.34

10.31

10B29

10*29

10.26

10.24

10.23

10.22

10.20

10.80

10.17

10.15

10.15

10.11

10.08

10.06

10.04

tve

tve

-

Reading i n Gammas

Residual

-593

-542

-593

-492

-442

-542

-593

-643

-442

-492

-391

-442

-542

-442

-593

-694

-744

-694

-793

-643

I .

. .- station distwe (ml

T.rlFIE 19 - .,.--.-. -- WGNEiIC PZ9FILE 5 - (W,5 DATA

LOOATION;: 10Cm FROM W, 4 -ie 300m FROM f YAM-FOBOUR J U K T I O N

Acading I

- Polarity

-- Svs

-1-vs

station distance ( rn)

F G 22 Magnetic

A s u b s ~ r f a c e s t ruc tu ra l connection bstvreen theas lows ct tile

YZ ends o f tile magnetic p ro f i l e s can not be ruled out,

I 3.46 --- Mxpst ic Profile (MP,~)

0 T h i s is located 15011 south of MP.5 on a bearing 210 . The magnetic

prcfi3.e is 1850m long, The measured magnetic in tens i ty (az, and ths -

Instrument Re acli ng

--- ?20

243

360

240

200

190

:a3

1.6d

210

200

220

?40

243

380

'330

200

280

220

rn 260

185

19C

220

--

- Range

- 3

FIG 2 3 Mags-tic anomaly curve of MP 6

Instrmcnt Reading

180

' 180

1 60

140

140

150

160

i 60

180

220

160

160

160

230

349

130

-

- Range

-

Time Polarity

+ve

Reading in Gammas - 2 ,814

1814

1613

141 1

141 1

1522

1613

1613

1814

2218

1613

1613

16 13

2318

3427

C G Z L Magnetic anomaly c g r v e of MP 7 , i

T.'...RLG 22 --- -<->-

hUiGN.CTiC PROFIE 8 (MP,8) DATA

5 30Qn AFTER FOBOM? PRIPJARY SCHOOL, ON KUDEDU RCAD

Range Tine Polar i ty 1- 1 !

station distance (rn l I

I

anmaly grapho

SbV-.NF description of the anomaly from 0 t o 300 maters shows a

nsgative uniform anomaly which has a l inear re la t ionship with t h e

negative anomalies observed i.7 MP.6 and W.7, There is a sharp rise i n

the magnetic anomaly betwen 300 meter$ and 350 meters t o a value about

25W ganmas, The NE pa r t of the prof i le , marked by high posi t ive

magnetic anmaly coincides with the col separating two in t rusions of

Bumblenda -. Fayali te - Granitee. These intrusions designated a s M2 i n

the southern par t of the mapped area i n f igure 2 is believed t o have

co:ltributed -to the high aagnetic reading a? the vicinity.

3.5 Discussion

A combination of t h e e l ec t r i ca l sounding3, e l ec t r i ca l p rof i l ing and

magnetic measusements 1s i s the case i n t h i s study gives a good idea of

t he subsurface feature i n the area i n three dimensions, Magnetic

signatures of thicker weathered and water saturated overburden over

hard rock t e r r a i n ' h i ch have been reported by earlier workers, i f

i o s ~ r z e d and cornbi,.:d a i t t t h e h e c t r i c a l sounding and profiling results,

shou;J ix able t o confirm t h e presence o r ~ 5 s e n c e of economic exploitable

w a t ~ r i n at-. area,

The tnterprcta t ions of e l ec t r i ca l somdings (ES, 1-5) presenttd i n

tab le 7 shows t h a t the thickness of the overburden varies from place t o

p l a ~ e . A maximan ovarburden thickness of about 107 meters and aquifer

thtclmess of about 103 meters are recorded i n ES,1. The aquifer

r 5 s i s t i v i t y values range botwecn 6s-m and 1- m, Stations ES.2

and E P , 5 located south of Eel have smaller thicknesses of 49 meters

and 47 meters zespectively f o r the overburdenr The aquifer thickrms

$5 a l s o small a t t h e s e s t a t i o n s south of ES,l. S t a t i o n s ES,2 and ES.5

show squil 'er th icknesses of 35 and 50 meters respec t ive ly indicating

th in ing of t h e aquifor .southwards (see Figure 3, 5-9, and t a b l e 7).

The e l e c t r i c a l and magnetic anomalies are a t t r i b u t e d t o the presen~e

o f m r i o u s rock typos and probably s t r u c t u r e s ~ i k e f a u l t s , fractures,

and buried r i v e r channels.

- & h e c lose resemblance of apparent r e s i s t i v i t y measurements of

p r o f i l e s 2, 3 , 4 and 5 as wll as t h e semblance a l s o noticed among are

t h e magnetic p r o f i l e s of 6 , 7, and 8 ' , i n t e rp re ted t o ind ica te a near A

su r face homogeneity i n t h e azea.

The anomaly s o u c e responsib le f o r t h e approximately l i n e a r

r e s i s t i v i t y lows trnnding North-South on the western end of t h e

e l e c t r i c a l measurenlcnts of p r o f i l e s 2, 3, 4 and 5 with broad anomaly

f l anks , appzared as magnetic low in p r o f l l e s 6 , 7 and 8 of t h e magnetic

rreasuremcnts,, Yhe l i n e a r i t y and broad f l anks of t h e anomaly could have

i x . x i t e d from pwbably f a u l t of much l a t e r a l displacement cr a l i n e a r

s t ruc5ura l iy control-icd buried rivex- channel. The presence of a 'ir)

p-obable second fau1.t t rending North-South and located on the easLern

p a r t of the p r o f i l e s has a l s o been in fe r red from t h e ana lys i s of

EP,2-4 (see figs, 25a, 26b, 27a and 27b), Unlike t h e f i r s t irrferrecl

f a u l t , t h e second f a u l t is not very apparent on the magnetic p r o f i l e ,

Stahl (1973, 1974 and 1975) showed t h a t i n s t e e p l y dipping Faults:

t h e r e s i s t i v i t y p r o p e r t i e s may be divided i n t o t h r e e d i s t i n c t parks

namely the r e s i s t i v i t y o: blocks on each s i d e s of the f a u i t and t h e

z s s i s l i v i t y cf t h e f a u l t zone . i t se l f , H e a l s o pointed out t ha t var ious

cornkinations are poss ib le , f o r example

( 1) the r a s i s t i v i t y of t h e t h r e e blocks may be unequd

CIG XJ R n c e i iog~am cl E P 2,3 ?. 7

FIG 27a Fmce diagram OF Y P 3 84

(2) the two fault blocks may be of equal r e s i s t i v i t y , while t he f a u l t

zma ma-? appear as e i t h e r more r e s i s t i v e or more conductive than

the bloclcs,

But whether t h e f a u l t i s more conductive o r more resistfve, t h e electrica

r~cis-Livi ty curves of t h e p r o f i l e s a r e angular a t the point!; where an

elec t rode crosses the f a u l t . Conductive fau l t s appear as mlnimum while

a r e s i s t i v e one manifests i t s e l f a s a maximum, S t a h l (1974:l futher t

sho:rrr?d t h a t a r e s i s t i v i t y anomaly f l a t e n s out with increasi.rq e l ec t rode A

sepe~ztiorl , T h i s i n any case may have contr ibuted t o s m extent t o t he

a ~ p a r e n t broad f l a n k s of the resistivity curves that iridicated t h e

first inferred f a u l t . Satpathy and Kanungo (1976) noted that. hard rock. terrains show

low t o t a l magnetic i n t e n s i t y wer t h i c k weathered overburden. The lower

t h e t o t a l magnetic i n t e n s i t y i n such ai> area (hard rock ten'aj-n) t h e

th icker t h e overburden,

Henkel atic! Gvzman (1977) attribtittld l i n e a r magnetic rniriimum t o

l i n e a r fractum zows o r l inear structurally controlled buried river

c h a n x l . They alzo pointed out that t he magnetic minimum rr!sults

from t h e oxidat ion md hydration along the l i n e a r f r a c t u e >:ones,

The readings and the r e s u l t s of electr ical sounding ES,1 ( t a b l e s 1

and 7!, t h e very low magnetic i n t o n s i t i o s as obsarved i n Fm, 3 ancl F.P.4

of figures 20 and 21, the low resistivity values of EP.3, W.7 of

figures 13, 17 and 28 ind ica te that the overburden is thicker In the

Nortbeastesn part of the surveyed area of interest. That tihe overburder

and t h e probable aquifer t h i n southwards and poss ib i iy less saturated

with water are indica ted by t h e increas ing r e s i s i t i v i t y and rnagnc-tlc

i n t ens i t - f due & x t h , ?!I@ assoc ia t ion of low resistivity and: low

87

magnetic i n t e n s i t y values i r t h o surveyed area agrees well with the

observations of Apparao and Roy (1973), Apparao (1977), Satpathy and

Kanugo ( 1976) . Another t h i c k ovcrburclen apparent on the w s t c r n perimeter

t rending approximately NorthSouth i s also suspected. This can be

a t t r i b u t e d t o l incar s t r u c t u r a l cont ro l ,

The r e s i s t i v i t y may (figure 28a) shows a r e s i s t i v i t y c o n t r a s t

t h a t d iv ides t h e area into two major port ions. The western por t ion

charac ter isad by high r e s i s t i v i t y corresponds t o the Younger Grani te

Complex (Ms of f i g u r e 2). Tho high r e s i s t i v i t y probably i n d i c a t e s

nearness t o the surface of the umathc rcd Younger Granlte . The

1XX) f lm contour l i n e along t h e vestern baundary of t h e survey area

de l inea tes the Younger Granitc with r e g o l i t h from tho unwathered

outcroping portion.

A g r e a t par t of t h e area expccia l ly tk e a s t e r n ard southern

parts g e m r a l l y show low m s i s t i v i t y va lues defined by resistivity

contour lines of 100s m t o 4OOn m, Few isolated spo t s i n t h e

ccntral p a r t of t h e area with r e s i s t i v i t y values of 60C t o 7 W m

are also present. This area belongs t o t he Pre-Cambrian t o Lower

Paleozoic D~scment com~lcx, The low r o s i s t i v i t y probably indicates a

t h i c k water bearing and weathered horizon.

Unlike t h e r e s i s t i v i t y rnTep, the Younger Granite boundary with

t h e Pre-Cambrian Baserncnt is well defined by tho magnetic anmally

c o n t r a s t , The Younger Grani te i s defined by t h e very low magnetic

67

anmalies of -400 t o -700 gammas on t h e western part of t h e area.

The - 200 gamma contour line defines t h e boundary of the Younger

Granite with t h e Basement. The Pre-Cambrian Basemcnt i:s chncrscteris

by high magnetic i n t e n s i t y v s lues except a t the North-wstcrn part,

Two areas within the Pre-Cambrian Basement (along P.P,6 of f igum 28b)

of exceptionally very high msgnetic .values correspond to the out crop

of k i l s Valley granite-por hyry (Y). P

Two bore hole sites have been recmended on the basis of the

magnetic and e lec tr ica l signatures which correspond to ~mcjnetic and

e l e c t r i c a l lows (figures 28 and 29),

FtG 28a Resistivity m a of the survey .. .

CHAPTER FOUR

CONCLUSION

The r e s u l t s of the survey showed two probable loca t ions of

p o t e n t i a l aquifers . The aquifer depths and thicknesses show v a r i a t i o n s

from place t o place. Maximum th ickncss of overburden of 107 meters

is reg i s t e red a t e l e c t r i c a l sounding s t a t i o n number 1 (S .I). A

m i n i m u m thickness of 47 metors is recorded a t e l e c t r i c a l sounding

s t a t i o n number 5 (ES,5). Thininc; of t h e aqu i fe r i s suspected south-

wards. Subsurface r e s i s t i v i t y and magnetic v a r i a t i o n s suspected t o

be s t r u c t u r a l l y cont ro l led were also observed,

The area of i n t e r e s t has no bed rock exposure on t h e surface.

The geophysical r e s u l t s sharacd a r e s i s t i v e i n s i t u 01. t r anspor ted

hard dry t o p l a t e r i t i c s o i l , The th icknesses of t h i s t o p s o i l vary

from lrn t o about 7 meters i n places. The i r r e s i s t i v i t y va lues vary

from 450 m t o over 2000 m. Underlying the t o p !;oil is t h e

weathered and aquiferous medium of low r e s i s t i v i t y va lues of 42 m

t o 257 m and th ickness of 35 mctcrs t o over 90 me.ters. Th i s

aquiferous horizon gradual ly grades t o unfractured 2nd unweathered

r e s i s t i v e basemcnt .

On t h e b a s i s of near surface homogeneity and f i e l d masursmnts

the two sites f o r t h e rccommcnded boreholes ( f i g u r e s 3 and 29) are:-

( 1 ) t h e area enclosed by t h e NortbSouth road t o Iyam, EF',7, EF,4

and t h e road .to Fobour mission and mining camp,

(2) t h e area north of Lenge-Kudedu road, west of EP,5 and vest of

E P m L .

P-A present magnetic me+hod is r m e l y used f o r ground water prespec-

.Ling, Thz r e s u l t ob tn imd i n t h e survey with magnetic method is

encouraging, The use of magnetic method t o outline and delineate

structures capable of housing t h e aquifer required in hard rock

terrain would makes it a potent ia l geophysical prospecting method

fo r water, From these attributes a quick rscogni t lon and wide spread

use of magnetic meti-:eel in water explora t ion i n had rock t e r r a i n i s

anticipatedo

fijakaiye, D,E,, (1976). A Gravity survey over the Nigerian Younger Granite Province Kogbe, C.A, (ed) G?ology of Nigeria. El izah than Pub, Go, Nigeria P207-22Pa

, (19766). Densities of Rocks i n t h e Nigerian Younger Granite Province Kogbe, C.Am (ed) Geology of Nigeria, Elizabethan Pub. Co, Nigeria, P225.232.

Apparao, h; (1971). Resis t ivi ty model experiment 2. Exploration Vol. 2, p

Apparao, A & Roy, A. (1973). F i e l d r e su l t of Direct Current Resis t iv i ty Prof i l ing w i t h two Electrode Array, Geoexploration, Vole 11 ~22-44.

Badejoko, Tart,; (19%). Role of lidiabatic Crystal l izat ion and Progressive molting i n t h e Origin of thouyounger Granites - Sara-Fier Complex &I Kogk, C.A. (ed) Ge logy of Nigeria, Elizabethan Pub. Co. Nigeria, P19!j-2C6. n

. Berridge, N.G.; (1971). The Jarawa Complex & The G e o l m of the J o s Plateau, Bull Geol. Survey of Nigeria, No. 32, Vol. 2 P85-87

; ( 9 7 1 ) . The Shero Cdnplex The Ge logy of the Jos Plateau, Bul l Geol. Survey of Nigeria, No. 38, Vol. 2 P87-97.

. Bowden, P, ; Whit ley, J .E, and Brecmen, V ,O. ; ( 1976) . ilecent Geochemical Studies on the Younger Granites of Northern Nigeria. in Kogbe, Cali. (ed) Geology of Nigeria, Elizabethan Pub, Co. Nigeria, Pl77-194.

Borley, G.D; ( l g 6 ) , Ferromagnesian M i m r a l q y and Temperature of Formation of the Younger Granites of Nigeria 12 Kogbe, CJ,; (ed) Geology of Nigeria, Elizabethan Pub. Co, Nigeria, p159-176.

- Bose, R.N. ; Chatterjee, Dm and Sen, A.K.; ( 1 9 3 ) . Elec t r ica l Res is t iv i ty Survey f o r Groundwater i n Aurangabad Subdivision , Gaya Di s t r i c t , Bihar, India. Geoexploration Vol. I1 P171-181.

. Pobrin, M.B. ( 19%) . lntroctuction t o geophysical prospecting, New York, McGraw-Hill.

. . Flathe, H. ; (1969) Interpreta t ion of geoelectr ical resist ivifiy measurements f o r solving hydrogeological prob:lcms hbrlcy, L.W. (ed) Mining and Groundwater Geophysics, (;Eoloqical Survey of Canada, P580-597.

Henkal, N. 8 Guzman, Me, (1977), Magnetic Features of Frac ture zones, Geoexploration. Vol, 15 P173-181.

Keller, G.V. and Frischknecht, S.C., (l%6). E l e c t r i c a l methods i n Geophysics, Oxford Press.

Keller, G.V,, (1967). Application of R e s i s t i v i t y methods i n mineral and G r undwater explora t ion programme in Morley L,W. (ed) Mining a d Groundwater Geophysics, El -66.

Lcnnox, D.H. and Carlson, V . , (1%9) . f ntegra t ion of Geophysical methods f o r groundwater explora t ion i n the P r a i r i e Province, Canada in Morley , L,VJ. (ed) Groundwater Geop:~ysi cs . P517-535.

Macleod, W.N. and Turner, D.C., (1971). The Younger Granite2 a Geology of 30s Plateau, Geol. Survey of Nigeria, Bul l no 32, Vole 1, P48-90.

Perkin, W.A., and Stembridge, J.H., (1966). NIGEFiIA - /\ desc r ip t ive Geography, Ibadan, Oxford Universi ty Press. Ibadan,

Roy, K.K. and Rao, K.P., (1977) Basement e f fec t on Line Source D.C. kpparent R e s i s t i v i t y p ro f i l e s . Geoexploratioq Vol. 15 P16S172.

Satpathy, B.N. and Kanugo, D.N. (1976). Ground water explora t ion i n Hardrack Ter ra in - A Case History. Geophysical Prospecting, Vol . 24, P725746.

S t a h l , II,L., (1973). Detection and d e l i m a t i o n of f a u l t s by Surface Resia t iv i9y measurements. Gas H i l l Region, Frcmont and Natrona Counxries, Wyo. Bureau of Mines Report of Inves t iga t ion no 7824. U.S. D.1.

, (1974). Detection and de l inea t ion of f a u l t s by surf ace R e s i s t i v i t y measur~rncnts. Schwartzwalcler Wines, J e f f e r s o n County. Colo, Buereau of Mines Reports of Inves t iga t ion no 7975, U.S .D,I.

, (1975). k l c c t i o n and de l inea t ion of f z u l t s by surface R e s i s t i v i t y measurements, Canada Mines. Caribon County, Idaho. Bureau of Mines Report of I n v e s t i g a t i o n 6 8072, U.S,D.I.

Turner, D.C., (1976). S t r u c t u r e and Petrology of t h e Younger Granite R i n g Complrx & Kogbe C.A, (ed) Geology of Nigeria Elizabethan Pub. Co. Nigeria P143..158.

T u r n e r , D.C., (1971). Tertiary and Quaterrialy G e o l o ~ & The G e o l ~ g y of th. Jos Plateau. Geological Sumey crf Nigeria. Bull , n*; 32, Vol. P91-101.

Unz) M,, (1968). Vertical Profil ing over a medium of contimusly Varing Resist iv i ty . Geophysical Prospecting. Vol, 16 Pa-435.

7 Wright, J ,Be, (1976). Volcanic Rocks i n Nigeria 2 Kogbe Cdl, (ed) Geology of Nigeria. Elizabethan Pub. Co, Nigeria. P93- 142

- Wright, P,E. (1971). Basement Complex & The G ~ l o l l y of 30s '

Plateau; Geological S m y of Nigeria, B u l l @ 6 32 Vela 1 P12-47i