Post on 26-Mar-2015
A
FIELD RFEPORT
ON
THE INDEPENDENT FIELD MAPPING EXERCISE
TO ILUDUN-EKITI, ILEJEMEJE LOCAL GOVERNMENT AREA,
EKITI STATE
BY
MAGBAGBEOLA FIYINFOLUWA ADEOLU
AGY/07/0830
SUBMITTED TO
THE DEPARTMENT OF APPLIED GEOLOGY,
THE FEDERAL UNIVERSITY OF TECHNOLOGY AKURE,
ONDO STATE.
IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE
AWARD OF BACHELOR OF TECHNOLOGY (B.TECH) IN APPLIED GEOLOGY.
MAY 2010
CERTIFICATION
I hereby certify that Magbagbeola Fiyinfoluwa Adeolu with the matriculation number
AGY/07/0830 carried out the independent geological field mapping at Iludun in Ekiti State and
submitted to the department of Applied Geology, School of Earths and Mineral Sciences (SEMS) Federal
University of Technology, Akure Ondo State.
...................................... ……………………………………..
DR.C.T OKONKWO MR ADETUNJI
(H.O.D APPLIED GEOLOGY (FIELD CO-ORDINATOR)
DATE DATE
DEDICATION
This report is dedicated to the Lord Almighty, the provider of wisdom and knowledge. The
report is also dedicated to my parents for their immense support and encouragement financially and
spiritually.
ACKNOWLEDGEMENT I give the Almighty God all my gratitude. I appreciate my loving parents, Mr. and Mrs.
Magbagbeola for their endless support towards the success of my chosen field. A big thank you goes to
my siblings for their thoughtful gestures towards the success of my career. To the Dean of the School of
Earth and Mineral Sciences, Prof. J.A. Adekoya,the Head of Department of Applied Geology, DR C.T
Okonkwo, Dr Asiwaju Bello, Dr Anifowose, Dr Ashidi, Dr Opeloye, Mr Adetunji, Mrs Bamisaye, Mr
Owoseni ,Mr Adepoju and all technologists,may God reward you bountifully.
Many thanks goes to my efficient group members, Olofinyo Olabode, Ayeni Ademola and
Ayodele Adeyemi . To all other groups in the surrounding villages, thank you for the love shown.
TABLE OF CONTENT
TITLE PAGE
CERTIFICATION
DEDICATION
ACKNOWLEDGEMENT
TABLE OF CONTENT
LIST OF FIGURES
LIST OF TABLES
LIST OF PLATES
ABSTRACT
CHAPTER ONE
1.0 Introduction
1.1 Aims and Objectives
1.2 Location
1.3 Topography
1.4 Drainage System
1.5 Vegetation
1.6 Soil and Weathering Condition
1.7 Method of Study
1.8 Previous Work
CHAPTER TWO
2.0 DETAILED PETROLOGY
2.1 Gneisses
2.2 Migmatite - Gneiss
2.3 Charnockite
2.4 Modal analysis
CHAPTER THREE
3.0 STRUCTURAL GEOLOGY
3.1 Foliations
3.2 Faults
3.3 Folds
3.4 Joints
3.5 Veins
3.6 Dykes
CHAPTER FOUR
4.0 ECONOMIC GEOLOGY
4.1 Migmatite-Gneiss
4.2 Gneisses
4.3 Charnockites
CHAPTER FIVE
5.0 Geologic History of Study Area
CHAPTER SIX
6.0 Conclusion and Recommendation
References
LIST OF FIGURES
Fig: 1 Map of Nigeria
Fig: 2 Geological Map of Nigeria
Fig: 3 Map of Ekiti State
Fig: 4 Topographic map of Iludun Ekiti
Fig: 5 Drainage pattern of Iludun- Ekiti
Fig: 6 Photomicrograph of Rocks
Fig: 7 Foliation
Fig: 8 Folds
Fig: 9 Faults
Fig:10 Joints
Fig:11 Veins
Fig:12 Dyke
Fig:13 Rose diagram
Fig:14 Beta Diagram of Rock attitude
Fig:15 Geologic map of Iludun
Fig: 16 Geologic Section of Mapped area.
LIST OF TABLES
Table 1 Modal analysis of charnockite at location 25
Table 2 Modal analysis of migmatite gneiss at location 10
Table 3 Modal analysis of migmatite gneiss at location 13
Table 4 Modal analysis of gneiss at location 36
Table 5 Modal analysis of gneiss at location 18
Table 6 Orientation of joints
Table 7 Orientation of veins
LIST OF PLATES
PHOTOMICROGRAPH OF MIGMATITE GNEISS (L10) UNDER CROSS NICOL: PLATE A
PHOTOMICROGRAPH OF MIGMATITE GNEISS (L10) UNDER PLANE POLARIZED LIGHT: PLATE A1
PHOTOMICROGRAPH OF MIGMATITE GNEISS (L13) UNDER CROSS NICOL: PLATE B
PHOTOMICROGRAPH OF MIGMATITE GNEISS (L13) UNDER PLANE POLARIZED LIGHT: PLATE B1
PHOTOMICROGRAPH OF GNEISS (L18) UNDER CROSS NICOL: PLATE C
PHOTOMICROGRAPH OF GNEISS (L18) UNDER PLANE POLARIZED LIGHT: PLATE C1
PHOTOMICROGRAPH OF CHARNOCKITE (L25 UNDER CROSS NICOL: PLATE D
PHOTOMICROGRAPH OF CHARNOCKITE (L25) UNDER PLANE POLARIZED LIGHT: PLATE D1
PHOTOMICROGRAPH OF GNEISS (L36) UNDER CROSS NICOL: PLATE E
PHOTOMICROGRAPH OF GNEISS (L36) UNDER PLANE POLARIZED LIGHT: PLATE E1
ABSTRACT
The mapping exercise was carried out in Iludun-Ekiti and its surrounding villages; Iye-Ekiti,
Eda-Oniyo, all within Ilejemeje Local Government Area, Ekiti State, South Western Nigeria. The
area mapped is part of the Nigerian basement complex.
The main purpose of the mapping exercise is to prepare a geologic map out of the
topographic map provided which served as a guide to the outcrops in the mapped area.
Properties observed on the outcrops encountered in the field include its extent, lithology,
structural features, attitude and mineral composition. In the laboratory, the rocks were
analyzed as thin sections using the polarizing microscope.
CHAPTER ONE
1.0 INTRODUCTION
Nigeria can be divide into two based on its lithology;
1. Sedimentary Basins
2. The Basement Complex
The area mapped is in the South Western part of the Nigerian basement Complex. The Basement
Complex is made up of crystalline rocks, both igneous and metamorphic. The rocks in this part of the
crystalline complex are charnockite, migmatite gneiss and gneiss. The mapped are covers an area of
33Km2.
Charnockites are the most dominant rocks in the mapped area covering about half of the map.
The charnockites occur as massive, rounded and distinct bodies with a few found to be extensive. The
migmatites and gneisses are highly deformed with joints and faults on their surfaces orienting in all
directions. Their mineral lineation are folded and are covered with quartzitic and in some places,
quartzofeldspathic veins. Exfoliation surfaces as well as biological weathering are the most dominant
forms of weathering encountered. The soil in this area is loamy and is used for agricultural purposes.
Figure 1: Map of Nigeria
1.1 Aims and Objectives
The main purpose for this mapping exercise is to create a geological map and its
cross section out of the topographic map provided and this was achieved by locating the
outcrops in the area. This helps in delineating the contact between the various rock types in the
area and correlating the rock units. Mapping techniques taught in the school premises and in
Igarra, Edo State during AGY 318 were applied.
Figure 2: Geologic Map of Nigeria
1.2 LOCATION
The area mapped; Iludun Ekiti is located in Ilejemeje Local Government area of Ekiti
State, south western Nigeria. The mapped area covers an area of 33Km2 and is located between
latitude 7049IN and 7050IN and longitude 5013IE and 5014IE.
Figure 3: Map of Ekiti Showing Ilejemeje Local Government Area
1.3 TOPOGRAPHY
The mapped area is generally highland rising about 1600m above sea level on the
average. Few shrubs and light forests are scattered around the area.The topography of the
mapped area is shown in figure 4.
Figure 4: Topographic map of Iludun
SCALE: 5cm represents 2 Km
1.4 Drainage Pattern
The mapped area is well drained having a dendritic pattern and flowing towards
the western part of the map. The direction of flow is mainly controlled by the underlying
crystalline rocks. The rivers are not down cutting because of the hardness of the
underlying rocks which are highly resistant to fluvial weathering. The drainage is shown
in figure 5
Figure 5: Drainage parrern of Iludun area
1.5 Vegetation
The mapped area is located within the rain forest belt with slightly thick forests with
scrubs and scattered cultivation. Most of the land is used is used for agricultural purposes with
food crops being cultivated.
1.6 SOIL AND WEATHERING
The soil encountered in the mapped area is dark, loamy soil which is very good for
agricultural purposes because it is rich in organic matter. The weathering type present in
the area are biotic and exfoliation.
1.7 Method of Study
Traversing was applied during this mapping exercise. This involves moving from
one outcrop to the other in a systematic pattern following major roads as well as
through bush paths. The traversing was carried out on foot. The lithology, mineral
composition and visible structures on the encountered outcrops were noted on the
field.
Locating outcrops were carried out using the compass clinometers and distances
were measured using our pace lengths. Hand specimens were chipped off using a sledge
hammer before further chipping was carried out in the laboratory using the cutting
machine. The process of converting to thin sections involved cutting, lapping (using
Carborundum of 200,400 and 600 grit), grinding and then mounting. The slides are then
analyzed under the polarizing microscope for mineral identification.
1.8 Previous Works
Detailed studies has been carried out on the south western part of the basement
complex in which Iludun, Ekiti is part of. These studies were used as reference materials
for the completion of this report. Notable among these studies were those of Rahaman,
M.A (1976), Odeyemi, I.B (1993) and Hockey et al (1964).
CHAPTER TWO
2.0 DETAILED PETROLOGY OF THE MAPPED AREA
This is the systematic study of rocks as hand specimens collected directly from the field
and as thin sections studied under the polarizing microscope. The rocks encountered during
mapping exercise in Iludun Ekiti are
2.1 GNEISS
This is a rock consisting of light and dark mineral layers alternating each other. High
temperature and pressure have altered the texture of the initial rock (granite) so that the
minerals have separated into layers. The platy minerals which make up the dark layers are
composed of amphiboles, chlorite, biotite and some muscovite while the light layers are made
up of coarse grained quartz and feldspars (plagioclase, orthoclase). Some garnets are also
present .The rocks is similar in composition to granite but is distinguishable by its foliation.
The rock is generally light coloured with a characteristic gneissic texture. The outcrops
are extensive with orientation of its trend in the NW-SE direction.
2.2 MIGMATITE GNEISS
Migmatite gneiss is the second most dominant rock type in mapped area. Migmatite is
a rock at the boundary between igneous and metamorphic rocks. They probably formed under
extreme conditions of regional metamorphism (Pan-African Orogeny, 600±250 m.y.) where
partial melting occurs in the previously existing rocks. They resulted from tectonic activities
arising from the injection of igneous material into the pre existing rock.
Migmatite gneiss contains feldspars (microcline, plagioclase), amphibole, garnet,
biotite, and some muscovite. The rock is highly deformed and fairly extensive and low lying
with a large number of folds and veins cutting across its surface in different directions.
2.3 CHARNOCKITE
These are hypersthene bearing rocks. They are orthopyroxene bearing granites
composed of hypersthenes (pyroxene) and are of magmatic origin emplaced during the
Eburnean Orogeny (1950±250 m.y.) and the Pan African Orogeny (600±150 m.y.). In the
outcrops encountered, there is the presence of strongly pleochroic reddish or green
hypersthenes when observed under the polarizing microscope.
The charnockites are dark green to black in colour with some appearing whitish to
reddish impacted by the orthopyroxene present which is the most abundant mineral. The
outcrops are rounded and weathered, having exfoliated surfaces with a coarse grained in
texture. Joints and veins as well as faults are present on its surface. A dolerite dyke is observed
on one of the charnockite outcrops.
Plate A: Migmatite Gneiss at location 10 under cross nicol
Plate A1: Migmatite Gneiss at location 10 under plane polarized light
Figure 6
Plate B: Migmatite Gneiss at location 13 under cross nicol
Plate B1: Migmatite Gneiss at location 13 under plane polarized light
Figure 6
PlateC: Gneiss at location 18 under cross nicol
Plate C1: Gneiss at location 18 under plane polarized light
Figure 6
Plate D: Charrnockite at location 25 under cross nicol
Plate D1: Charrnockite at location 25 under plane polarized light
Figure 6
Plate E: Gneiss at location 36 under cross nicol
Plate E1: Gneiss at location 36 under plane polarized light
Figure 6
2.4 Modal analysis
Location 25- Charnockite
Mineral 1st count 2nd count 3rd count 4th count Total Percentage
Composition
Feldspar 2 1 2 ------- 5 5.3
Quartz 3 2 3 2 10 10.5
Biotite 5 6 6 5 22 23
Amphibole 3 2 4 3 12 12.6
Opaque
mineral
14 12 9 11 46 48.4
Grand
Total
95
Table 1
Location 10-Migmatite Gneiss
Mineral 1st count 2nd count 3rd count 4th count Total Percentage
composition
Quartz 8 9 8 9 34 30
Feldspar 6 6 5 6 23 20
Biotite 10 12 10 10 42 39
Opaque 4 3 4 4 15 13
Grand
Total
114
Table 2
Location 13-Migmatite Gneiss
Mineral 1st count 2nd count 3rd count 4th count Total Percentage
Composition
Quartz 5 4 5 3 17 20.9
Feldspar 9 10 10 13 42 51.8
Biotite 4 4 4 3 15 18.5
Opaque 3 2 0 2 7 8.6
Grand
Total
Table 3
Location 36- Gneiss
Mineral 1st count 2nd count 3rd count 4th count Total Percentage
Composition
Quartz 10 9 11 10 40 32
Biotite 14 12 8 13 47 37.6
Feldspar 7 7 5 7 26 20.8
Opaque 4 2 4 2 12 9.6
Grand
Total
125
Table 4
Location 18-Gneiss
Mineral 1st count 2nd count 3rd count 4th count Total Percentage
Composition
Quartz 12 13 14 12 51 36
Feldspar 9 8 10 9 36 25.5
Biotite 9 9 7 8 33 23.4
Opaque
Minerals
4 4 1 3 12 8.5
Total 141
Table 5
CHAPTER THREE
3.0 STRUCTURAL GEOLOGY
This refers to structures developed as a result of deformation forces acting on rocks
due to orogenic activities. The first set structures developed as a result of the first orogenic
event are the bands and mineral lineation. This was followed by deformation of the bands
which of the bands which resulted in the formation of folds and are associated with joints,
fractures and faults.
3.1 FOLIATION
The foliations are most common in the gneisses made distinct by the parallel layers
consisting of alternating dark and light minerals. The foliations are of tectonic origin as
indicated by the presence of small, tight, minor folds on the straight limbs of the folded bands.
The foliations are defined as repetitive or penetrative planar features in a rock which
may be defined by compositional layering. They define the trend of the rock in the mapped
area with most of them in the NW-SE direction with very few in the NE-SW direction.These are
observed in figure 7.
3.2 FOLDS
A fold is a curved or angular shape of an originally planar surface. They are wave like
undulations formed during deformation of rock layers or planar structures on rocks. Most folds
found in the area occurred on the surface of the migmatite gneisses as a result of folding of
their mineral lineation . Some of the locations have more than one fold generation as observed
in figure 8b. Their fold axis generally tend towards the NE-SW direction. Some folds are
fractured while some occur as parasitic folds on the limbs of larger folds. They are seen in
figure 8a
3.3 FAULTS
A fault is a surface of discontinuity along which there has been displacement of rock
on either sides of the outcrop. It is characterized by a plane along which the rock bodies could
have moved on either of its sides. The faults observed were identified in the discontinuity if
lineation, veins and the dolerite dyke. A reverse fault was encountered as seen in fig 9a
occurring across a quartzofeldspathic vein and in fig 9b across a dolerite dyke within a
charnockite outcrop.
3.4 JOINTS
A joint is a plane of fracture along which there has been no relative displacement of
rocks along either side of the plane. Joints are developed as a result of the brittle nature of the
rocks that are close to the earth surface when they react to tectonic disturbances. A fracture
along which microscopic displacement has occurred but is invisible with the unaided eye might
also be referred. The joints found in the mapped area were oriented in different directions
pointing to the fact that most were formed during tectonic activities. Some joints found in the
outcrops are shown in figure 10. The rose diagram for the joints are shown in figyre 13A
3.5 VEINS
A vein is a tabular discordant body cutting across a rock. It is made up of minerals
that were crystallized out of magmatic fluids during the latter part of crystallization. The
minerals fill the fracture partially or wholly depending on the amount of mineralizing fluids
available after the rock forming minerals have crystallized. The veins encountered were mostly
quartzofeldspathic with a few quartzitic veins. They were mostly encountered on the migmatite
gneisses with a few found on the charnockitic rocks.
The orientations of the veins encountered are shown in the rose diagram in
Figure 13B. Some of the veins are shown in figure II
3.6 DYKES
A dyke is a sheet-like, near vertical minpor igneous intrusion that cuts across
horizontal to gently dipping planar structures in the country rock.
A dolerite dyke was observed on a charnockite outcrop in location 3 and it cuts across
the outcrop. Some part of the charnockitic host rock was found within the dolerite indicating
that the dyke was formed after the charnockite had crystallized. The dolerite is fine grained and
melanocratic. The contact vbetween the dyke and the host rock is distinct as shown in fig 12b
Some part of the dyke is faulted(fig 12c)
a b
Figure 7 a & b: Foliation in Gneissic Rocks
a b
Figure 8 a & b; Folds in Migmatite Gneiss
Figure 9a; Fault in a quartzofeldspathic vein Figure 9b : Fault along a dolerite dyke.
Figure 10: Joint in Charnockite Figure 11: Quartz vein in Charnockite
(a) (b)
(c)
Figure 12 : A dolerite dyke cutting across a charnockite. Note the relics of charnockite within
the dolerite In (b)
INTERVAL 0-20 21-40 41-60 61-80 81-100 101-120 121-140 141-160 161-180
FREQUENCY 2 4 3 4 2 3 1 4 8
Table 6A: Orientation of Joints
Scale: 2cm represents 1 unit
Figure !3A; Rose Diagram for Joint Orientation.
INTERVAL 0-20 21-40 41-60 61-80 81-100 101-120 121-140 141-160 161-180
FREQUENCY 1 4 2 8 2 4 1 3 6
Table 6B : Orientation of Veins
1cm represents 1 unit
Figure 13B: Rose Diagram for Vein Orientation.
Trend 1560
Plunge 100
Figure 14: Beta Diagram for Rock Attitude.
CHAPTER FOUR
4.0 ECONOMIC GEOLOGY
Economic geology is the geological study for the exploration and exploitation of
materials which can be profitably extracted by man. It deals with the usefulness of geological
materials for mankind. The delineation of mineralized deposits are carried out during field
mapping exercises. Rocks and their minerals as well as the accessory minerals they are
associated with are found useful in various industries.
4.1 MIGMATITE GNEISS
They are used as large cabochons for such things as belt buckles, bolo ties and
brooches; diverse decorative and functional pieces such as paperweights and bookends.
Polished migmatite can be used as gemstones and as ornaments in the home. Its polished form
can also be used for flooring it bis also used as foundation materials .
4.2 GNEISS
Polished gneiss has a shiny appearance and can be used as ornaments and for
construction purposes. They are used as building materials such as for flooring, as gravestones
and for work surfaces on furniture and in the kitchen. They are also used as facing stones on
buildings.
4.3 CHARNOCKITE
Charnockite can be crushed into dimension stones for construction purposes.They are
also used as geobarometers due to the presence of plagioclase, pyroxenes and quartz.
4.4 STRUCTURAL FEATURES
Fractures and joints occurring on the surface of rocks serve as conduits for water
movement and also for water accumulation. Partially filled veins also promote water
accumulations.
Open spaces in rocks such as fault planes, joints, cracks or fractures serve as zones
for deposition of economic minerals such as pegmatite which produce gemstones and quartz
which is used in manufacturing time pieces and silicon chips.
4.5 DRAINAGE
The rivers in the area are generally used for agricultural and domestic purposes. Most of
the rivers are perennial in nature realized from the fact that the field exercise was carried out in
the heart of the dry season.
CHAPTER FIVE
5.0 GEOLOGICAL HISTORY OF MAPPED AREA
The mapped area is part of the Nigerian Basement Complex which is divided into five
major groups in the south western part (Rahaman 1976);
1. The Migmatite-Gneiss Group.
2. The Charnockite Group.
3. The slightly migmatized to unmigmatized paraschists and metaigneous group.
4. Older Granite Group.
5. Unmetamorphosed dolerite dykes which are believed to be the youngest occurrences.
Not less than two orogenic episodes have modified the rocks in this area. No actual
age determination technique has been applied on rocks in this area to determine the
absolute ages . From the field studies and geologic section, the oldest rock in the area is
charnockite followed vby migmatite gneiss and then the gneiss as observed in the
geologic section in figure 16
The charnockite is coarse grained and occur as massive bodies. There is a dyke which
intrude one of the charnockite outcrops indicating that it was formed after the host had
crystallized. The charnockite are of magmatic origin, crystallizing at depth and exposed
due to the weathering of the overburden. The intrusion of the charnockite during the
Pan African Orogeny (600±150 m.y.) possibly modified the pre existing rocks to gneissic
rocks. Further intrusion of charnockites gave rise to migmatite gneiss and then gneiss at
the edge of the mapped area with deformation reducing in the western direction. This
further intrusion gave rise to the high deformation found in the migmatite gneisses.
Figure 15: Geologic map of Iludun Ekiti.
LEGEND
Gneiss
Migmatite Gneiss
Charnockite
Figure 16; Geologic cross section between points A & B
CHAPTER SIX
6.0 Conclusion and Recommendation
6.1 CONCLUSION
The mapped area, Iludun Ekiti is part of the Nigerian Basement Complex. Rocks present
in this area are grouped into two;
The Charnockite Group
The Migmatite- Gneiss Group.
The dolerite dyke group is found in only one outcrop and is not extensive. The
charnockitic rocks are the most widespread in the mapped area as indicated by the
geologic section. The intrusion of the charnockites altered the pre existing in to
migmatite gneiss snd gneiss with deformation reducing in the north eastern direction.
The migmatite gneiss dips at680E while the gneiss dips at 640E. The migmatites and
gneiss were probably homogenous before the igneous intrusion. The dolerite dyke
which was found as intrusions is younger than the charnockites and is oriented in the
north western direction.
6.2 RECOMMENDATION
The university should provide G. P. S for all students to make locationing much
easier and the work, less tedious. The university should also provide better welfarepackages
and make adequate accommodation available before sending students out for individual field
work.
The indigenes of the town must always be informed about the mapping exercise
before the arrival of the students to avoid attracting hostile behavior from them.
REFERENCES
RAHAMAN, M.A(1976), Review the Basement Geology of South Western Nigeria in
Geology of Nigeria Edited by C.A Kogbe P 39-53
PLUMBER, C.C,CARDSON D.H,(2008):Physical Geology, twelve Edition.
ROBERT,J.T.(1992): STRUCTURAL Geology.
GHOSH,S.K. (1993): Structural geology,fundermentals and modern development.