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.