ORIGIN OF CLAY AND CASE STUDY..

1
A RESEARCH CARRIED OUT
BY
AGBAJE TITUS MAYOWA
AT THE UNIVERSITY OF ILORIN, KWARA STATE, NIGERIA
ORIGIN OF CLAY
AND
CASE STUDY

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TABLE OF CONTENTS
INTRODUCTION………………………………………………………………………………………………………. 3
CHAPTER ONE: OCCURRENCE OF CLAY……………………………………………………………………. 4
CHAPTER TWO: TYPES OF CLAY BASED ON ORIGIN …………………………………………………… 6
CHAPTER THREE: MECHANISM OF CLAY MINERAL FORMATION……………………………….. 9
CHAPTER FOUR: CLAY ENVIRONMENT OF FORMATION……………………………………………… 11
CHAPTER FIVE: CASE STUDY…………………………………………………………………………………….. 14
REFERENCES……………………………………………………………………………………………………………. 22

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INTRODUCTION
The term Clay refers to a naturally occurring material composed primarily of fine-grained
minerals, which is generally plastic at appropriate water contents and will harden when dried or
fired. Clay usually contains phyllosilicates; it may contain other materials that impart plasticity
and harden when dried or fired. Associated phases in clay may include materials that may not
impart plasticity and organic matter. Depending on the content of the soil, clay can appear in
various colors, from white to dull gray or brown to a deep orange-red.
Clay and sand both indicate a specific grain size; however, it is often used to refer to a specific
mineralogical composition of sediments. They are distinguished from other fine-grained soils by
differences in size and mineralogy. Clays are hydrous aluminum silicates, ordinarily containing
impurities e.g., potassium, sodium, calcium, magnesium, or iron, in small amounts.
clay is applied both to materials having a particle size of less than 2 micrometers(0.002mm)
and to the family of minerals that has similar chemical compositions and common crystal
structural characteristics.

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CHAPTER ONE
OCCURRENCE OF CLAY
Sedimentary rocks only make up 5% of the Earth's crust, but cover about 80% of the surface of
the earth in which clays (including shales) form well over 40% of the sedimentary rocks. The
raw material for sedimentary rocks comes from weathering. If we look at the volume of
material at the earth's surface (Fig. 1), we see that clay minerals constitute about 16% of its
total. 20 km is considered the surface of the earth because it is the region from which we
extract natural resources (and dump our waste). Clay sediments are collected by the agencies
of water (e.g. marine clays, alluvial clays, lacustrine clays), wind (Aeolian clays), or ice (e.g.
glacial clay, till or boulder clay). The majority of the common sedimentary clays, however, are
the marine deposits typically comprising mixtures of coarser material with clay in which the clay
mineral illite are usually predominant.
Clay mineral-rich deposits can be formed in two other principle ways:
• By weathering of parent minerals in situ to form a clay rich residual soil in which the clay
mineral kaolinite frequently predominates, especially common in landscapes undergoing
tropical weathering, and
• By ascending fluids, i.e. by hydrothermal alteration of the host rock. Cornish china clay is a
good example, the feldspar of the local granite having been converted mainly into clay minerals
of the kaolinite group.

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Figure 1 the volume of material at the Earth’s surface. (Thair and olli 2008)

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CHAPTER TWO
TYPES OF CLAY BASED ON ORIGIN
There are two types of clay based on origin namely:
1. PRIMARY CLAY: Residual clays are found in the place of origin (not far from parent
rock). They are also known as residual clay. They are non plastic and are white. Example
includes Kaolin. They are Most commonly formed by surface weathering, which gives
rise to clay in three ways:
 By the chemical decomposition of rocks, such as granite, containing silica and
alumina.
 By the solution of rocks, such as limestone, containing clayey impurities, which,
being insoluble, are deposited as clay
 By the disintegration and solution of shale. One of the commonest processes of
clay formation is the chemical decomposition of Feldspar. Example of Residual
clay
Figure 2 showing an example of Residual clay: Kaolin and a finished product

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2. SECONDARY CLAY: Secondary clays are far from parent material. They are also known
as sedimentary clay which is removed from the place of origin by an agent of erosion
and deposited in a new and possibly distant position. They are plastic, grey and darker.
Many secondary clays contain organic (carbonaceous) and other impurities (iron, quartz,
mica, etc.) Examples of secondary clay include: Ball clay, Stoneware clay, Fireclay,
Earthenware clay, Slip clay, Volcanic clay.
Figure 3 showing an example of Sedimentary clay: Ball clay and finished product of
Stoneware (3i) and Earthenware clay (3ii).
3i 3ii

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The interpretation of the origin of clay minerals is one of the most interesting aspects of clay
mineralogy. Clays and clay minerals occur under a fairly limited range of geologic conditions.
The environments of formation include soil horizons, continental and marine sediments,
geothermal fields, volcanic deposits, and weathering rock formations. Most clay minerals form
where rocks are in contact with water, air, or steam.
Recall that the nature of clay formed during the weathering process depends upon three
factors:
1. The mineralogical and textural composition of the parent rock.
2. The composition of the aqueous solution.
3. The nature of the fluid flow (i.e., rate of water flow and pore network)
The contact of rocks and water produces clays, either at or near the surface of the earth” (from
Velde, 1985)
Rock +Water → Clay
For example, the CO2 gas can dissolve in water and form carbonic acid, which will become
hydrogen ions H+ and bicarbonate ions, and make water slightly acidic.
CO2+H2O → H2CO3 →H+ +HCO3-
The acidic water will react with the rock surfaces and tend to dissolve the K ion and silica from
the feldspar. Finally, the feldspar is transformed into kaolinite. The rock mineral weathering is
one of the main natural sources of clay minerals and metal concentrations in the soil. The soils
are open system. Accordingly, the faster the flow rate, the shorter the contact time of solution
with the primary minerals. Clay minerals are stable under conditions near the surface.

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CHAPTER THREE
MECHANISM OF CLAY MINERAL FORMATION
There are three mechanisms of clay mineral formation namely:
1. INHERITANCE
Origin by inheritance simply means that a clay mineral found in a natural deposit
originated from reactions that occurred in another area during a previous stage in the
rock cycle and that the clay is stable enough to remain inert in its present environment.
Clay minerals are detritally inherited from pre-existing parent rock or weathered
materials. Its stability may result either from slow reaction rates or from being in
chemical equilibrium.
2. NEOFORMATION
Origin by Neoformation means that the clay has precipitated from solution or has
formed from reaction of amorphous material. The formation of Neoformation clearly
depends upon the appropriate physicochemical conditions of the immediate weathering
environment, such as the pH, composition and concentration of the soil solutions as
well as nature of the starting material and factors relating to the external environment
like Temperature, rainfall and percolation rate.
3. TRANSFORMATION
During Transformation, the essential silicate structure of the clay mineral is maintained
to a large extent but with major change in the interlayer region of the structure. Origin
by transformation requires that the clay has kept some of its inherited structure intact
while undergoing chemical reaction. This reaction may take two forms:
I. Ion exchange, in which loosely bound ions are exchanged with those of the
environment.
II. Layer transformation, in which the arrangements of tightly bound octahedral,
tetrahedral, of fixed interlayer cations are modified.

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It is important to determine which mechanism give rise to clays in a natural deposit. Clays that
have inherited their crystal structures are indicators of provenance and provide information
about environmental conditions in the sediment source area.
Neoformed clays have precipitated in response to in situ conditions, past or present.
Transformed clays carry both types of information, having inherited characteristics from the
source area and having reacted in response to in situ changes in environment.

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CHAPTER FOUR
CLAY ENVIRONMENT OF FORMATION
This environment can be described in terms of Temperature, pressure, chemical
composition and reaction time. In order to generalize, these variables are condensed
into three geological situations, the conditions within each of which vary over a limited
range. The situations, again based on the ideas of Esquevin (1958) and Millot (1970),
are:
I. The Weathering Environment,
II. The Sedimentary Environment
III. The Diagenetic-Hydrothermal Environment.
The Weathering Environment Is the upper zone of the Earth’s crust that is at or near the
atmospheric interface, where temperature and pressure vary over the relatively narrow range
of Earth surface conditions. Reaction times are therefore relatively short, usually of the order of
thousands of years because the upper layers of a soil undergo continuous erosion and solution
composition is variable depending mainly on original rock type, rainfall, evaporation and
drainage.
The Sedimentary Environment is most often found near or below sea level or lake level, in
depressed areas of the crust and refers to the zone near the sediment-water interface. In the
most common sedimentary environment for clays, the ocean floor, temperatures are generally
lower and restricted to a narrower range than those found in the weathering environment,
pressures may range to more than 1 Kilobar + (1 Kilobar= 105
Pa) in the deepest part of the
ocean and the composition is that of sea water or related pore water. Reaction time generally
measured in millions of years, depends on rates of sedimentation and subsidence, and on rates
of sea floor subduction, processes that move clays into higher temperature environments.
The Diagenetic-Hydrothermal Environment includes all zones that have been in contact with
hot water. Clays in this situation may experience a wide range of environmental conditions.

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Figure 4 Nine possibilities for the formation of clay minerals in nature after
Esquevin (1958) and Millot (1970)
The three mechanisms for mineral formation operating in three geological
environments yield nine possibilities for the evolution of clay minerals (figure 4).
Generally, inheritance dominates in the sedimentary environment where reaction rates
are slow, whereas layer transformation, a mechanism that can require large inputs of
energy becomes prevalent in the higher temperature Diagenetic-Hydrothermal
environment. Between these extremes is the weathering environment in which
examples of all three mechanisms are common.
Clays Neoformed from crystalline rock in the weathering environment will be traced as
they are transported into the sedimentary environment, buried and heated in the
Diagenetic- hydrothermal environment, and eventually recrystallized during
metamorphism. With uplift and weathering, the cycle begins again.

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Figure 5 A simplified clay cycle on early Mars, indicating: (1) a surficial/sedimentary component,
(2) Diagenetic/burial component, and (3) a hydrothermal component.
To summarize the most important features of the clay cycle include: (1) lack of tectonic
recycling and tectonically-driven basin development, (2) less lithologic diversity of igneous
rocks, (3) a significant impact-hosted hydrothermal source for newly formed clays, (4) a
significant volcanically (and impact) generated pyroclastic source for newly formed clays, (5)
muted burial diagenesis due to limited longterm persistence of liquid water.

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CHAPTER FIVE
CASE STUDY 1
The Geology and Mineralogy of Clay Occurrences around Kutigi Central Bida Basin, Nigeria
*Akhirevbulu O.E. Amadasun C.V.O., Ogunbajo M.I. and Ujuanbi O
The first case study is around Kutigi Central Bida basin a study on Geology and Mineralogy of
Clay occurrences.
STUDY AREA
The study area (Kutigi) is situated in Lavun Local Government Area of Niger State, within Bida
basin. It lies between longitude 5o 351 E and 5o 391 E and latitude 9o 101 N and 9o 131 N and
covers an area of about 39.88km2 .The physical landform of Kutigi area is made up of flat-lying
to gently rolling plains. The ridges ranges from 15m to 50m in height as observed along the
road cutting between Kutigi town and Ruga village. The terrain is mostly covered by laterite and
fairly by sandstone as a result of the weathering activities that have depleted the hills and
ridges. The area is particularly drained by river Toro which run near Kusogi village and flow in
the NE direction of Egbako SW. Many in sequent streams that enters river Toro as tributaries
are seasonal and forms a dentritic drainage pattern which strongly suggest that the terrain is
composed of lithological, structural and topographic homogeneity.

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Figure 6 showing Location map of Kutigi Area within Nigeria and Bida Basin.

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METHODOLOGY
Detailed field mapping was carried out around Kutigi in order to establish the local Geology of
the area. From field observations, all locations within the study area consist of laterite except
near Kutigi town, where two hills suspected to contain clay were identified. To ascertain if the
two hills observed near Kutigi town actually contains clay, a confirmatory test was conducted
which involves the addition of small amount of water to powdered sample and the mixture
uniformly stirred until a plastic stage is attained. The results of the observed experiments were
affirmative. As such, both hills were assigned location A and location B respectively for easy
identification.
Laboratory Analysis
A quantitative determination of the mineralogical property of the clay samples using X-ray
diffraction were carried out at National Steel Raw Material Exploration Agency, in Kaduna,
Nigeria. The powdered sample was weighed and tested using a PW1800 automated powder
diffraction equipped with a Cu -Ka radiation source (30kV, 55mA), inbuilt standards, peak/width
and a detector. The diffraction pattern was obtained with the aid of a computer, while the 2θ,
d-values and peak intensities yielded by the powder patterns were used to identify the
minerals.
RESULT
Two hills (location A and location B) were identified and observed to contain deposits of clay
within the study area, both which are near, and separated by Kutigi town. Location A measures
N 20° W, while location B measures N 39° E of Egbako SW. Other locations within the study
area consist typically of laterite.
Location A was the first hill visited in the study area. It consists of a coarse grained, thin layer of
lateritic overburden of about 2.5 – 9m thick that grade finely upward. It varies from red to
reddish brown in colour. The overburden was underlain by a bed of poorly exposed deposits of
clay, though relatively exposed by an abandoned excavated pit located at the side of the hill.
The clay feels gritty to touch from hand specimen and varies from white to dirty white in
colour. The clay, which is about 3m – 12m in thickness, thins out towards Kusogi village. At the
foot of the hill lies a bed of sandstone of about 1-10m thick.

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Location B was the second hill visited in the study area. The hill which is about 30m high, with a
length of about 110m, is a continuous ridge with steepy sides and poor vegetation. The hill
consists of an overburden with mixture of laterite and sandstone with a thickness of about
1.5m. Beneath the overburden lies a bed of poorly exposed clay with a thickness of about 6m
intercalated with a layer of laterite of about 14m. The clay varies from white to brownish white
in colour from hand specimen. The decolouration of the clay was probably as a result of stains
from the laterite overburden. Present at the foot of the hill are deposits of coarse-grained
sandstone of about 8m in thickness.
Results of mineralogical analysis
A sample of the results obtained from the X-ray diffraction analysis is presented in Figure 7
below.
Figure 7 X-ray diffraction result of Kutigi Clay

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The XRD results of the mineralogical analysis showed the mineralogical assemblages of the
sample. The major minerals present have been indicated against the diagnostic peaks as shown
in figure 7. The results of the mineralogical composition of the clay show that the dominant
minerals present are kaolinite and quartz, while illites occur as traces. Of all the mineral
presents, kaolinite alone constitutes about 43.64%, quartz constitutes about 54.55% while illite
constitute about 1.18% in the unprocessed sample. However, result of the investigated clay
deposits differ significantly from those of some well-known kaolin deposits in terms of their
mineralogical compositions. The Kaolinite content of Kutigi clay (43.64%) is by far lower than
that of Ibadan (91%), Oza-Nagogo (86%), Kaduna (96%), China-clay (85%).
Whereas the quartz content of Kutigi clay (54.55%) is far higher than those of Ibadan (6%), Oza-
Nagogo (14%) Kaduna (2%), China-clay (traces. The illite content of Kutigi clay constitutes about
1.18%.
RESULT FINDING
Mineralogical investigation of the clay, revealed the presence of kaolinite, quartz and fairly,
illite. Kaolinite constitutes about 43.64%, quartz about 54.55% and illite about 1.81% in the
unprocessed samples. The high dominance of quartz in the clay deposits clearly explains its
grittiness and also suggests the clay to be of residual origin. Kutigi clay differs significantly from
those of other well known deposits in terms of its mineralogical composition.
The result from the X-ray Diffractogram shows that the clay mineral is predominantly Kaolinitic.
On the basis of the results from the geological mapping and x-ray diffraction analysis, it can be
deduced that the Kutigi clay was deposited as alluvial deposit from braided and meandering
streams, and it is predominantly Kaolinitic in nature. The colour of the clay, which varies from
white to dirty-white, is attributed to stains from the laterite overburden.

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CASE STUDY 2
Distribution and Origin of Clay Minerals in Konya Neogene Sedimentary Basin, Central
Anatolia, Turkey
Selahattün kadür1 & Zehra karakaþ2
The second case study is on distribution and origin of Clay minerals.
GEOLOGY OF THE STUDY AREA
The pre-Neogene basement rocks of the Konya Neogene basin comprise serpentinite, schist,
and crystallized limestones (Ozcan et al. 1990; Hakyemez et al. 1992; Figure 8). These units are
overlain by Neogene fluvial sediments and lacustrine deposits. Fluvial sediments
(conglomerate, sandstone, mudstone and green claystone) are thick at the margin of basin and
thin laterally toward the centre of the basin, where lacustrine units (limestone, clayey
limestone and white claystone) dominate.
On the other hand, in the lowest part of the central section, green claystone is exposed in thin
layers alternating with fine-grained green sandstone; all layers have similar thicknesses. In
contrast, white claystone is observed only in a small part of the Hatunsaray section (at the
margin of the basin) but is dominant in the central part of basin. In places where there are
alternations, white claystone and limestone are generally described as clayey limestone.
Carbonate friability decreases in hard, fractured, and voidy limestone units. The lateral and
vertical characteristics of these latter units can be used to distinguish sandy, clayey Dolomitic
and pure limestones.

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Figure 8 Showing the Geological map of the Konya basin (Simplified from 1:500,000 scale
geological map of Turkey published by the General Directorate of Mineral Research and
Exploration of Turkey).

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METHODOLOGY
Samples were collected from six stratigraphic sections in carbonate and fluvial sediments of the
Konya Basin.
The mineralogical characteristics of the samples were determined by X-ray powder diffraction
(XRD) using CuKa radiation (Rigaku-Geigerflex), and scanning electron microscopy (SEM) (Joel
JSM 6400) for petrographic study. Clay mineralogy was determined on <2 µm clay fractions
prepared by sedimentation followed by centrifugation of the suspension after overnight
soaking in distilled water.
Semi quantitative estimates of both clay fractions and rock forming minerals of the <2 µm
fractions were calculated by the external standard method of Brindley (1980).
Seven representative samples of different facies were chemically analyzed for major oxides by
XRF (Rigaku X-ray Spectrometer RIX 3000).
RESULT AND FINDINGS
These analyses revealed the presence of smectites, chlorite, sepiolite, Palygorskite and illite
(clay minerals), associated with quartz, feldspar and amphibole (Detrital minerals), and
dolomite, calcite and aragonite (carbonate minerals). Smectite and chlorite are abundant in the
marginal facies. Chlorite is abundant in the Bent and Þadiye sections, which are dominated by
fluvial units Smectite (commonly) and chlorite (rarely) are present in the sandstone and
mudstone units in lower part of the sequence of the central part of the basin. These minerals
are accompanied by illite, quartz, feldspar and amphibole. The evolution of Smectite and
chlorite from the marginal facies toward the lower part of stratigraphic sequence in the central
facies indicates that these minerals have a genetic relationship to the Detrital with calcite and
dolomite, while chlorite and Smectite are absent. This shows that sepiolite, Palygorskite and
dolomite are not of Detrital origin but, rather formed by diagenesis. Field observations and
mineralogical determinations indicate that the distribution and origin of clay minerals in the
Konya Neogene sedimentary basin were controlled by physico-chemical environmental
conditions within the sediments. Thus, sepiolite and Palygorskite formed diagenetically in
carbonate units of the central part of the basin, in contrast to Smectite and chlorite occurrences
which are of Detrital origin in the marginal facies of the basin.

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REFERENCES
Akhirevbulu O.E., Amadasun C.V.O., Ogunbajo M.I., and Ujuanbi O., (2010): The Geology and
Mineralogy of Clay Occurrences around Kutigi Central Bida Basin, Nigeria.
Brindley, G.W. 1980. Quantitative X-ray mineral analysis of clays. In: Brindley, G.W. & Brown, G.
(eds), Crystal Structures of Clay Minerals and Their X-ray Identification. Mineralogical Society
Monograph No. 5, London, 411-438.
Esquevin, J. 1958. Les silicates de zinc. Etude de produits de synthese et des mineraux naturals.
Theese Sci. Paris.
Hakyemez, H. Y., Elübol, E., Umut, M., Bakýrhan, B., Kara, U., Daúýstan, H., Metün,T. and
Erdoúan, N. 1992. Konya-.umra-Ak.ren DolayÝnÝn Jeolojisi (Geology of Konya-.umra-Ak.ren
Area). General Directorate of Mineral Research and Exploration of Turkey Report No: 9449 [in
Turkish, unpublished].
Millot, G. 1970. Geology of clays (trans. W.R. Farrand & H.Paquet). New York: Springer-Verlag.
Ozcan, A., Goncuoglu, M.C., Turhan, N., Senturk, K., Uysal, Þ. & Isýk, A. 1990. KONYA-
KadÝnhanÝ-IlgÝn DolayÝnÝn Temel Jeolojisi (Geology of Konya-KadÝnhanÝ-IlgÝn Region).
General Directorate of Mineral Research and Exploration of Turkey Report No: 9535 [in Turkish,
unpublished].
Selahattün, k., Zehra, k., (2002): Distribution and Origin of Clay Minerals in Konya Neogene
Sedimentary Basin, Central Anatolia, Turkey.
Thair and Olli (2008): Clay and Clay Mineralogy, Physical-chemical properties and industrial
uses. Vol. 30.6.
Tosca, N.J., and Hurowitz, J.A., (2011). Neoformation, diagenesis and the clay cycle on early
mars, Dept. of Earth Sciences, University of Cambridge, Cambridge CB2 3EQ, United Kingdom;
Planetary Science Institute, Tucson, AZ 85719, USA; JPL/Caltech, Pasadena, CA 91109, USA.
Velde, B., 1985. Clay Minerals, Developments in Sedimentology, 40, Elsevier, Amsterdam,427 P.

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