INTRODUCTION
1. Necessity of the research
Kaolinite clays in East Nam Bo region are of wide distribution area, from
medium to high quality, were formed in various geological conditions. They are
an important source of mineral raw material in ceramic production industry and
have been exploited and used since a long time. At present the demand in kaolin
clay raw material for ever growing local ceramic industry. Therefore,
investigation and exact assessment of the potential of this raw material resource
in East Nam Bo region in particular and in Vietnam in general is an urgent
practical requirement.
So far many studies have been conducted on kaolinite clays minerals in
East Nam Bo region, but these studies were not comprehensive, so the
assessment of the use of kaolinite clays minerals has been only of a general
character. For this very reason, a study on the forming conditions and material
composition characteristics as well as prerequisites and signs for their
prospecting is a very urgent requirement. Doing well these studies will assist to
evaluate correctly their quality, to select appropriate processing procedures and
to orient properly the use of this potential raw material resource of the region.
To contribute to the solution of the above mentioned problems and to
meet the requirements in the practice of geological investigation and
exploration of kaolinite clays in East Nam Bo region, the post graduate student
has selected the theme "Forming conditions and material composition
characteristics of kaolinite clays in east Nam Bo region" for the Thesis.
2. Scope and object of research
2.1. Scope of research: The scope of research of the Thesis is the East
Nam Bo region, limited by the following coordinates:
10048’30”-11040’30” North latitude;
106017’30”-107027’30” East longitude.
This region is covered by the following 1: 200,000 map sheets: Ho Chi
Minh city (Saigon) (C-48-VI); Cong Pong Cham-Loc Ninh (C-48-IV and C-48V) with the topographic base in HN-72 coordinate system.
It covers ≈ 6795 km2 and administratively it belongs to the jurisdiction of
Ho Chi Minh city and parts of Binh Duong, Binh Phuoc, Dong Nai provinces.
2.2. Object of research: Kaolinite clays in East Nam Bo region.
3. Objectives and tasks of the Thesis
3.1 Objective
The objective of the Thesis is to clarify the forming conditions and material
composition characteristics of kaolinite clays in the East Nam Bo region.
3.2 Tasks
To achieve the objective of the Thesis it was necessary to carry out the
following tasks:
Collecting all geological data on clay minerals in East Nam Bo region (65
deposits and occurrences), systematizing, analyzing and synthesizing the data to
clarify the forming conditions and distribution characteristics of kaolinite clays
in the region.
Studying the material composition (mineral composition, chemical
composition), structural and textural characteristics, technical properties of
kaolinite clays occurring in the study area and thence proposing the orientation
for using this kind of mineral raw material in East Nam Bo region.
Determining the prerequisites and signs for prospecting of kaolinite clays,
factors controlling them; evaluating their prospectiveness and proposing the
directions for further study.
4. Methods of research
The Thesis was prepared based on the use of the following traditional and
modern methods of research:
Collection and synthesis of data;
Field investigation;
Laboratory analysis and test for determining the material composition and
technical properties of kaolinite clays (SEM, DTA, XRD, chemical analysis,
particle size analysis, processing test);
IT method;
Data analysis, processing and synthesis.
5. New achievements of scientific significance of the Thesis
Full and comprehensive research on the genesis and forming conditions
of kaolinite clay deposits in East Nam Bo region: Minh Hung, Suoi Nuoc Vang;
Ap 3; Minh Long; Tan Quy; Thai My..
Detailed research on material composition of the above clay deposits
based on the results of laboratory analysis of clay samples.
Evaluation of quality and technical properties of clay minerals, proposed
directions for their exploitation and use.
6. Scientific and practical significances of the Thesis
The research results of the Thesis have contributed to the clarification of
the nature, composition, forming mechanism of kaolinite clays in East Nam Bo
region and their relationship with geological factors.
On the basis of studying the material composition kaolinite clays in Nam
Bo region, the Thesis will help the producers to select optimal schemes for
processing, recovery and use of kaolinite clay minerals.
The Thesis has contributed to the clarification of the distribution law
kaolinite clay minerals in the region, proposed the future investigations for
planning and overall assessment of this kind of mineral resource.
7. Arguments to be defended
Argument 1: The kaolinite clay deposits in East Nam Bo region are
concentrated in the basin of Saigon river, forming a strip extending from Thu
Duc to Dau Tieng lake, belonging to 2 genetic types :
Residual weathering type on lower-middle Jurassic sediments (J1-2): Minh
Hung deposit; on Cretaceous granodiorite (K): Suoi Nuoc Vang deposit.
Sedimentary type in Ba Mieu formation: Ap 3 deposit; in Dat Cuoc
formation: Minh Long deposit; in Thu Duc formation: Tan Quy deposit; in Cu
Chi formation: Thai My deposit.
Argument 2: The clay deposits in the study area are of good quality with
the contents of kaolinite 20 - 75%, illite 5 - 15%, montmorillonite 0 - 5%, quite
useable as skeletal raw material for ceramic industry.
8. Composition of the Thesis
The Thesis is presented in 142 pages typed in A4 format including
appendices, with 19 photos, 23 drawings, 46 tables and 91 biographic reference
items. Besides the Introduction and the Conclusion, the Thesis consists of 5
chapters as follows:
Chapter 1. Geological and mineral resource characteristics of East Nam
Bo region;
Chapter 2. Theoretical basis and methods of research;
Chapter 3. Forming conditions and distribution characteristics of kaolinite
clays in East Nam Bo region;
Chapter 4. Material composition characteristics of kaolinite clays in East
Nam Bo region;
Chapter 5. Technical properties and possible uses of kaolinite clays in
East Nam Bo region.
9. Data basis of the Thesis
The Thesis was prepared on the basis of the data collected by the post
graduate student and obtained by him during the field survey, laboratory
analysis and data processing from clay deposits in East Nam Bo region from
2005 to present in the process of his working in the Southern Geological
Mapping Division.
The post graduate student has collected and processed the analytical data
of 1076 particle size distribution samples, 162 comprehensive chemical samples
195 DTA samples; 195 XRD samples; 6 SEM samples; 86 kaolin recovery test
samples; 36 post-recovery kaolin chemical samples; 47 post-recovery kaolin
DTA and XRD samples; 17 kaolin technical property samples.
Besides, the post graduate student also consulted a series of research
works on methodology, regional geology, published works, even archived
documents on clays (see the references).
All of the above data sources are reliable basis for the post graduate
student to use in the process of formulating the Thesis.
Chapter 1. GEOLOGICAL AND MINERAL RESOURCE
CHARACTERISTICS OF EAST NAM BO REGION
1.1. Structural position of the study area in the regional structural plan
In the regional structural plan, the study area is Bien Hoa sub-zone of Da
Lat zone, which is a superimposed basin filled by terrigenous sediments of Ban
Don series aged early - middle Jurassic, which is of regional scale, covering the
South Trung Bo and East Nam Bo as a whole.
1.2. History of studies
The history of geologic and mineral studies in East Nam Bo region is
divided into two periods :
1.2.1. Period before 1975
In this period studies were carried out mainly by foreign authors,
typically: E. Saurin (1935); J. Fromaget (1941); H. Fontaine and Hoang Thi
Than (1971, 1975).
1.2.2. Period after 1975
In this period, many geological survey and mineral prospecting works
have been carried out at various scales: 1: 500,000 (Tran Duc Luong, Nguyen
Xuan Bao et al., 1981); 1: 200,000 (Hoang Ngoc Ky, Nguyen Ngoc Hoa et al.,
1980-1991) and 1: 50,000 (Ma Cong Co, Ha Quang Hai, Le Minh Thuy et al.,
1988 - 2003).
Also, project proposals and reports on exploration of kaolinite clay
deposits at various scales from 1: 2,000 to 1: 10,000 such as: Linh Xuan kaolin
deposit, Dat Cuoc kaolin deposit, Tan Uyen, Ap 2, Ap 3,…kaolin deposits were
prepared by Hoang Trong Mai, Doan Sinh Huy, Nguyen Van Mai, etc., (19961999).
In 2001, a monograph on geology and mineral resources of Ho Chi Minh
city was published under the editorship by Vu Van Vinh.
In 2004, a project on stratigraphic subdivision of Neogene-Quaternary
(N-Q) and studying the geologic structures of Nam Bo region was carried out
with editorship by Nguyen Huy Dung.
In 2005, the project "Evaluation of the actual status of solid mineral
resources of Ho Chi Minh city and preparation of a master plan for their
exploitation and use to the year 2020” was carried out with editorship by
Nguyen Ngoc Hoa.
In summary : The above research works have clarified the stratigraphy
and structure of the sediments, the related mineral resources, especially clay
minerals in general and kaolinite clays in particular. They are rich and valuable
sources of data used by the post graduate student in this Thesis.
1.3. Geological settings
Participating in the geological settings of the study area are sedimentary,
extrusive and intrusive formations aged from late Permian (P2) to Quaternary
(Q). They were formed in various stages with different tectonic and
geodynamic circumstances.
1.3.1. Stratigraphy
The stratigraphy of East Nam Bo region, which occupies the main part of
the study area, consists of the following formations :
PALEOZOIC GROUP, PERMIAN SYSTEM
1.3.1.1. Upper Permian, Ta Not formation (P2tn)
This formation is composed of conglomerate, sandstone, siltstone,
claystone, with a thickness of 300m.
1.3.1.2. Upper Permian, Ta Thiet formation (P2tt)
This formation is composed of: conglomerate, sandstone, siltstone,
claystone, few layers of coaly shale; gray, black gray, thin to medium bedded,
weakly recrystallized limestone, intercalated with layers of claystone,
calcareous clay, siltstone, with a thickness of about 500 m.
MESOZOIC GROUP, TRIASSIC SYSTEM
1.3.1.3. Lower Triassic, Song Saigon formation (T1sg)
This formation is composed of: calcareous clay, calcareous siltstone,
siltstone, sandstone and shale of deep gray color, with a thickness of 700m.
1.3.1.4. Middle Triassic. Chau Thoi formation (T2ct)
This formation is composed of: cobble and pebble conglomerate with mixed
composition and particle size, polymictic tuffaceous sandstone, calcareous siltstone,
calcareous clay of gray color, with a thickness of over 450 m.
1.3.1.5. Upper Triassic, Dau Tieng formation (T3dt)
This formation is composed mainly of polymictic sandstone of gray,
white, red brown color, siltstone of red color and chert of white color, with a
thickness of over 230m.
JURASSIC SYSTEM
1.3.1.6. Lower Jurassic, Dray Linh formation (J1dl)
This formation is composed of: layers of calcareous sandstone and
siltstone intercalated with shale, siltstone; solid, strongly compressed calcareous
schist of black color, intercalated by thick-bedded calcareous sandstone with
black gray color, with a thickness of 150m.
1.3.1.7. Middle Jurassic, Chiu Riu formation (J2cr)
This formation is mainly composed of: sandstone, mudstone, siltstone of
greenish gray color, with thick bedding alternated with oblique undulation bedding,
containing silicified wood remains, with a thickness of 300m.
1.3.1.8. Upper Jurassic, Long Binh formation (J3lb)
This formation is composed of: andesitobasalt, laval tuff, agglomeratic
tuff of andesitobasalt, andesite, dacite, rhyodacite, passing upwards into
sedimentary layers of calcareous clay, thinly banded coaly shale, with a
thickness of 420m.
NEOGENE SYSTEM
1.3.1.9. Upper Miocene, Binh Trung formation (N13bt)
This formation is composed of : sand, gravel, pebbles with rubble weakly
cemented by silty clay of greenish gray color; silty sandstone of gray color,
thin-bedded mudstone of gray color, with a thickness of 119.4m.
1.3.1.10. Lower Pliocene, Nha Be formation (N2 nb)
This formation is composed of: conglomerate, quartz sandstone, rubbles,
debris as a result of weathering from the bedrock, sandstone, siltstone of deep gray
color containing carbonized plant remains (lignite), with a thickness
of 37m.
2
1.3.1.11.Upper Pliocene, Ba Mieu formation (N2 bm)
This formation is composed in the lower part of polymictic sand, pebble,
passing upwards into sand, silt, kaolin clay containing some intact pieces of
tektite, with a thickness of 4-10m.
QUATERNARY SYSTEM
1.3.1.12. Lower Pleistocene, alluvial sediments of Dat Cuoc formation
1
(aQ1 dc)
This formation is composed in the lower part of polymictic sand, pebbles,
passing upwards into sand, silt, kaolin clay with some intact pieces of tektite,
with a thickness of 4-10m.
1.3.1.13. Middle Pleistocene, Xuan Loc formation (Q12xl)
This formation is composed of: olivine basalt with massive structure
intercalated with porous basalt of black gray color, olivine dolerite of black
gray, brownish gray color, massive structure intercalated with porous basalt,
with a thickness of 89.7m.
1.3.1.14. Middle-Upper Pleistocene, alluvial sediments, Thu Duc
formation (aQ12-3)
In the lower part this formation is composed of sand, pebbles (including
rounded tektite pebbles), polymictic pebbles with kaolin. In the upper part it is
composed mainly of sand, silty clay, strongly lateritized to have motley color,
in many places forming lateritic clods and boulders, with a thickness of 4-50m.
1.3.1.15. Upper Pleistocene, Phuoc Tan formation (Q13pt)
This formation is composed of: alkaline olivine basalt of massive
structure alternating with porous one, with a thickness of 5-25m.
1.3.1.16. Middle-upper Pleistocene, alluvial-marine sediments, Cu
Chi formation (amQ13cc)
In the lower part this formation is composed of : sand, pebble, kaolin clay
(pebble and kaolin clay in some places are concentrated in lenticular deposits
with high grade, of significance in terms of mineral resource). In the upper part
it is changed to lateritized silt and clay, in some places clotted in the form of
pebble and gravel, with a thickness of 2-25m.
1.3.1.17. Lower - middle Holocene. alluvial-marine sediments, Binh
Chanh formation (amQ21-2bc)
This formation is composed of : fine sand, clay with greenish grey color,
silty sand with motley yellow gray color, with a thickness of 3-8m.
1.3.1.18. Middle-upper Holocene, alluvial-paludal sediments, Can Gio
formation (abQ22-3cg)
This formation is composed of sand, silty clay, clay, in some places
mixed with organic humus of deep gray color, with a thickness of 2-3m.
1.3.1.19. Upper Holocene sediments (aQ23)
These sediments occur along modern rivers and channels in the form of
low flood plains, composed of pebble, sand, silt, clay, with a thickness of 3-4m.
1.3.2. Magmatic intrusions
In the study area, magmatic intrusions consist of two complexes:
1.3.2.1. Tay Ninh complex (J3tn)
This complex is composed of: gabbro, pyroxene gabbro, pyroxenite of
medium grain size, bluish black gray color. The rocks are of massive structure,
subhedral granular to gabbroic, in some places weakly porphyritic texture.
1.3.2.2. Dinh Quan complex phase 2 (K1dq2)
The rocks of phase 2 of this complex are mainly composed of biotitehornblende granodiorite with pyroxene, of medium to medium-fine grain size.
1.3.3. Tectonics and structure
1.3.3.1. Tectonic position
In the structure of the study area participate 2 structural levels: PreCenozoic basement structural level and Upper Miocene - Quaternary volcanosedimentary structural level (N13 – Q) with maximum thickness 330m (BH 812A-TP, Binh Chanh, HCM City).
1.3.3.2. Deep structures
According to the results of research on Moho surface for the whole
territory of Vietnam by Cao Dinh Trieu (1996, 2001, 2003) (shown on the
structural map of Vietnam at 1: 500,000 scale), the study area (East Nam Bo
region) is located in the Northwest differential uplift area of the Moho surface
which tends to be deeper in Northwest and NE directions reaching 36 km in
Thu Dau Mot – Tay Ninh area.
1.3.3.3. Litho-tectonic assemblages
In the East Nam Bo region, 4 litho-tectonic assemblages are
differentiated, characterizing the 4 stages with different geodynamic regimes:
Permian - early Triassic mid-arc basin litho-tectonic assemblage (P- T1); middle
- late Triassic post-collision thermal reworking litho-tectonic assemblage (T2-3);
early-middle Jurassic post-collision basin litho-tectonic assemblage (J1-2);
Terrace litho-tectonic assemblage of middle Miocene - Quaternary passive
continental margin (N13-Q).
1.3.3.4. Structural blocks
According to the characteristics and thickness of the sediments in the
terrace litho-tectonic assemblage of Middle Miocene - Quaternary passive
continental margin (N13-Q) this period can be divided into two depositional
stages: late Miocene - Pliocene depositional stage (N13 - N2) and Pleistocene
depositional stage (Q1).
1.3.3.4.1. Structural blocks in upper Miocene - Pliocene (N13 - N2)
Considering the distribution law of N13-N2 formations, the exposure of
Pre-Cenozoic basement rocks (when the Quaternary sediments are removed) as
well as the thickness of N12 – Q sediments, we can differentiate the following
uplifted and subsided areas with different shapes and sizes: Loc Ninh stable
uplifted area accompanying with basalt extrusions; Tay Ninh weakly
differentiated subsided area.
1.3.3.4.2. Structural blocks in Pleistocene volcano-sedimentary formations (Q1)
Based on the current thickness presented by isopachs and the relationship
between sedimentary layers, the following structural units have been recorded:
An Loc - Dong Xoa stable uplifted area; Tay Ninh – Bien Hoa differentiated
uplifted area; Dong Nai river channel subsidence area.
1.3.3.5. Faults
In the study area there are three main faults: Vam Co Dong river fault
(F1), Saigon river fault (F2) and Chon Thanh – Phu Giao fault (F3). The
common characteristics of these three faults are that they were strongly active
in early Cenozoic with right strike-slip character, inactive in N12 – N2 and
reactivated in Quaternary.
1.3.4. Mineral resources n
In the study area the main minerals are clay, sand and gravel. Besides
there are also building stone, pozzolan, laterite…
Chapter 2. THEORETICAL BASIS AND METHODS OF
RESEARCH
2.1. Theoretical basis
2.1.1. Overview on clay
2.1.1.1. Definition of clay
Clay is a product of chemical weathering and chemical deposition
processes, formed by colloidal precipitation.
2.1.1.2. Classification of clay
So far the concept of clay minerals is still not unified and there are still
many different views, therefore there are still many different classifications of
clay minerals in literatures on clays world wide.
2.1.1.2.1. Some views on clay classification world wide
Some former Soviet mineralogists (Lazarenko, Milovsky...) classified
clay minerals into 4 families: kaolin clay family; halloysite clay family;
hydromica clay family; montmorillonite clay family;
Some Western mineralogists have other classifications:
Keit Frye (1981) classified clay minerals into the following main groups:
kaolinite group; fine mica clay group (called illite); smectite group; vermiculite
and chlorite group; group of clay minerals with nearly amorphous structure.
William Ness (1991), Deer et al. (1993) classified natural clay minerals
into the following main families based on the chemical composition
characteristics and crystal lattice structure: kaolinite clay family; illite clay
family; smectite clay family; vermiculite clay family; palygorskite clay family.
2.1.2.2- Clay classification in Vietnam
Currently in Vietnam some clay classifications as follows are used :
According to forming conditions: Based on the forming conditions.
clays can be divided into the following genetic types:
Clays with weathering genesis: are the clays formed in the process of
chemical weathering from pelitic sedimentary rocks or metamorphic, intrusive and
volcanic rocks rich in alumosilicates and are usually formed in weathering crust.
Clays of sedimentary genesis: are clays formed in the process of
eluviating clay from the weathering crust, where the clay is carried away by
temporary water currents and then deposits in the places with favorable
geological and physico-chemical conditions. Depending on the location and
depositional environment, clays are divided into different genetic types:
Proluvial clay; deluvial clay; alluvial clay; lacustrine clay; marine clay.
Besides, there are also mixed clay types between the above types: deluvialalluvial, alluvial-lacustrine, alluvial-marine,…
According to the dominant mineral components: based on this
criterion the clays can be divided into the following types: Kaolin clay – if
kaolinite is the dominant mineral; hydromica clay – if hydromica is dominant;
bentonite clay – if the minerals of montmorillonite group are dominant; clay
with mixed composition (polymictic clay).
According chemical composition: clays are divided into the following
types: basic clay: with Al2O3 content < 15%; subacidic clay: with Al2O3 content
15 - 30%; acidic clay: with Al2O3 content 30 - 39%.
According physico-mechanical properties: clays are divided into: non
plastic clay: with plasticity < 1%; low plasticity clay: plasticity index 1 - 7%;
medium plasticity clay: plasticity index 7 - 15%; Plastic clay: plasticity index >
15%.
According the fire resistance temperature: Clays are divided into: lowmelting clay: with fire resistance temperature 1050 - 1350°C; high-melting
clay: with fire resistance temperature 1350 – 1580 °C; refractory clay: with fire
resistance temperature > 1580°C.
According the utility of clay: brick clay; cement clay; ceramic clay,
refractory clay, etc.
In this Thesis, the post graduate student used a clay classification table
based on the combination of two criteria: Dominant mineral component and
forming genesis, which give the most comprehensive information on clay
minerals.
2.2. Basic concepts used in the Thesis
In the Thesis, the post graduate student used the following concepts:
2.2.1. Mineral deposit: According to A.E. Kariakin (1967), "Mineral
deposit is an accumulation of minerals which can be mined at present (deposit
having industrial value) or in a near future (deposit not yet having industrial
value) in the profitable economic and permissible technical conditions”.
2.2.2- Ore prospect: is a natural accumulation of mineral which is small
in size, but in quality meets the industrial requirement (it can be considered as a
mineral occurrence).
2.2.3. Ore occurrence: is a natural accumulation of mineral material which
has not been evaluated in size and ore quality and in the present condition still
cannot be considered as an object of mining (it can be considered as a
mineralization occurrence".
2.2.4. Material composition: Material composition comprises mineral
composition and chemical composition characterizing the mineral raw material.
Mineral composition: Mineral composition is assemblage of minerals
forming the ore or mineral raw material. It consists of assemblage of useful
minerals and that of associating harmful minerals.
Chemical composition: The chemical composition of a mineral raw
material consists of useful and harmful components of the raw material. The
higher the content of useful components and the lower the contents of harmful
component the better the quality of the raw material.
2.2.5. Original material and mineral raw material
Original material: Material in the natural state, not yet beneficiated after mining.
Mineral raw material: is the run of mine material which has been beneficiated
after mining to meet the technical requirements to be used in production.
2.2.6. Kaolin clay and kaolinite clays
Kaolin clay: Is polymictic clay of white, grayish white, pinkish white,
etc., color, plastic, soft, consisting of various groups of clay minerals: kaolinite
group, hydromica (illite) group, montmorillonite, etc., group.
Kaolinite clay: Is kaolin clay with mineral kaolinite being dominant
(kaolinite from 20 to 75% ) over other minerals.
2.3. Methods of research
The Thesis was prepared on the basis of using the following traditional
and modern methods of research:
2.3.1. Collection and synthesis of data:
The data collected range from original data such as boreholes, standard
outcrops, results of laboratory analysis of various samples …, to final data such
as report, maps, cross sections, etc.
2.3. Field investigation
Based on the results of data collection and synthesis, the post graduate
student carried out field investigations to verify the regional geological settings,
as well as the forming conditions and material composition characteristics of
kaolinite clays for each deposit.
2.3.1. Laboratory analysis
Laboratory analysis ware conducted to study the material composition of
the kaolinite clay materials, including their comprehensive mineral and
chemical compositions.
Mineralogical analysis: Mineralogical analysis was conducted to
determine the main mineral composition of mineral raw materials, as well as the
contents of useful and harmful components in the mineral raw materials.
Laboratory methods for determining the mineral composition include:
Scanning electron microscopy (SEM), differential thermal analysis (DTA) and
X-ray diffractometry (XRD).
Scanning electron microscopy: In scanning electron microscopy (SEM) a
beam of electrons sweeps over the specimen, the intensity of the secondary electrons
generated at the point of impact of the beam on the specimen forms an image of the
strength of the material. The result gives us the 3D image of the material.
Differential thermal analysis(DTA) : is an irreplaceable auxiliary method
allowing to determine structural and phase changes of minerals in the process of
heating the samples from the laboratory temperature to 1000°C.
X-ray diffractometry: is used for analyzing the composition of minerals
quantitatively or semi-quantitatively, in some cases in combination with other
methods one can determine quantitatively the relationship of minerals present in
the samples.
Chemical analysis: Aims at determining the chemical composition of
mineral raw materials and determining the contents of useful and harmful
components in mineral raw materials.
2.3.2. Technological research methods
Technological researches includes: studying the particle size distribution,
recovery,… and other technical properties of mineral raw materials.
Particle size: Studying the particle size distribution is determining the
particle size and determining the content (%) of each particle size fraction. The
particle size fractions include: sand: 2-0.05mm; silt: 0.05-0.005mm; clay
<0,005mm, of which the clay fraction plays an important role in identifying the
mineral raw material.
Recovery of kaolinite clays: The amount of kaolinite clay recovered through
the 0.1mm mesh sieve is dried and weighed to calculate its recovery (according the
sample preparation scheme).
Semi-quantitative spectral analysis: was carried out on composite
samples formed by extracting from the comprehensive chemical samples to
determine the contents of ore elements in the deposit.
Other technical indicators: plasticity index, shrinkage, water absorption,
whiteness, etc. are used for each production purpose.
Ceramic production test: Samples were collected from excavations, covering
the whole thickness of the kaolinite clay body with the weight of 500kg. The test
included making the product from the raw material of the deposit itself or mixture
with other materials.
2.3.4. Information technology method
The information technology method was used effectively in the
preparation of the Thesis: In this Thesis, the post graduate student used the
following editing and specialized software: Microsoft Word, Excel, Igpetwin,
CorelDraw, MapInfo. Besides, the post graduate student also used the particle
size distribution sample processing software of the Geomorphologic Center
developed in Pascal programming language.
2.3.5. Data processing and synthesis
Data processing: All data collected for studying the geological settings
of the area or of each deposit, such as the results of particle size distribution
analysis, results of sediment genesis and age determination, kaolin clay material
composition analysis, etc. were processed in a uniform manner.
Data synthesis: Data synthesis included: compilation of geological
sections of the study area and deposits, compilation of geological maps of the
study area and the deposits.
Chapter 3. FORMING CONDITIONS AND DISTRIBUTION
CHARACTERISTICS OF KAOLINITE CLAYS IN EAST NAM BO
REGION
3.1. Forming conditions
The genesis of clay minerals is a controversial issue. There are still many
different views on this issue but in general all scientists consider that there are
two genetic groups: endogenous and exogenous.
Endogenous group: Clay is formed by the action of the low temperature
hydrothermal flow on the country rocks. Almost all researchers agree with this
view.
Exogenous group: this group consists of kaolinite clay deposits of
residual weathering genesis and those of sedimentary genesis formed in
Cenozoic era.
Clay deposits of residual weathering genesis are usually met on the bed
rocks rich in alumosilicates.
Clay deposits of sedimentary genesis formed in the Cenozoic era are
found in sediments of various geneses and ages.
3.1.1. Forming conditions of kaolinite clay deposits of residual
weathering genesis
3.1.1.1. Concept of weathering
Weathering: is the process of destruction of the bedrock under the action
of physical and chemical factors and activities of living organisms in the normal
conditions on the Earth surface. Weathering is divided into three types based on
the acting factor and the way of alteration of the bedrocks: physical weathering,
chemical weathering and biological weathering.
3.1.1.2. Forming conditions of kaolinite clay deposits in East Nam Bo
region
3.1.1.2.1. Residual weathering genesis
In East Nam Bo region, kaolinite clay deposits are usually met in the
lithomarge zone of the weathering crust where clay is developed on
sedimentary rocks such as claystone, mudstone aged lower - middle Jurassic
and the granitoids aged Cretaceous (K). They are of the following forming
conditions in terms of topography, bedrock composition and climate:
In terms of topography: These deposits are usually met on the surface of
accumulation-erosion plains with elevation 50-80m aged early Pleistocene
(Q11). The clay minerals are usually exposed along erosional slope with slope
angle 15-35o incising into the planation surface.
In terms of bedrock composition: The bedrocks are rich in alumosilicates;
In terms of climate: The weathering process takes place in the humid
tropical conditions.
The process of weathering of different minerals of the bedrock in
different periods form different new products (new minerals). The results are
shown in Table 3-1
Table 3-1: Change of mineral composition in the weathering process
Original
Alkaline
Acidic
In humid tropical
mineral
sialite stage
sialite stage
area
components
(bedrock)
Potassium
Kaolinite +
Hydromica
Kaolinite + Opal
feldspar
Laterite (Fe+Al)
Kaolinite +
Plagioclase
Hydromica
Kaolinite + Opal
Laterite (Fe+Al)
Nontronite (pH=7Hydromica +
Amphibole
Kaolinite +Al2O3
Chlorite
7.5)
Hydromica +
Hematite,
Kaolinite
Biotite
Hydrobiotite
Limonite +
+ Mica
Kaolinite
(Glauconite)
Hydromica +
Small scales,
Kaolinite +
Muscovite
Kaolinite +
Hydromica
Al2O3+SiO2
Halloysite
3.1.2.2.2. Infiltration weathering
Concept of infiltration weathering crust: is the weathering crust where the
products are transported by groundwater and accumulated when the
environment changes, especially from reduction environment to strong
oxidation environment. Multi-valence elements such as iron, manganese play
the main role in the process of forming the infiltration weathering crust.
Mechanism of forming the infiltration weathering crust: Sedimentary
formations, especially those composed of sand, sand with pebbles contain a
large amount of kaolinite but their iron content is very high making the
kaolinite clay not meet the industrial criteria. The natural process can make the
iron content decrease, making the kaolinite many times whiter and cleaner
("bleaching" process ).
The "bleaching" process on kaolinite-bearing sedimentary formations is
related to the seasonal fluctuation of the groundwater level. This is due to the
hydrolysis of iron hydroxide II in the condition of lack of oxygen as follows:
Fe(OH)2→Fe2+ + 2OHIn rainy season the static water level in the sediments rises, the Fe2+ ions
move by capillary action to the zone rich in active oxygen and the reaction
occurs as follows:
Fe(OH)2→Fe(OH)3→Fe(OH)3.nH2O(limonite,
goethite)→Fe2O3(hematite).
In dry season the groundwater level returns to the original position
leaving behind the mineral assemblage: limonite, goethite, hematite in the
fluctuation zone, forming a gossan with thickness up to 4-5m, releasing a large
amount of iron from the kaolinite bearing sediments and making the kaolinite
clay whiter and cleaner.
3.1.2. Forming conditions of kaolinite deposits of sedimentary genesis
3.1.2.1.Some views on the formation of sedimentary clays in the world
The researchers of clays of sedimentary genesis are divided into 4 main
groups with different views as follows:
The sedimentary-chemical genesis view developed by Millot and E.E.
Sabaev: These authors consider that the formation of clay is decided mainly by
the pH of the environment.
The view developed by Grim, Pauerxa, M.I. Viculov is opposite to that of
Millot. They consider that the most important factor in the process of forming
clay in sedimentary basins is the nature of the material source.
The view developed by Uiver, M.A. Rataev and Strakhov: According to
this view, clays are mainly of allogenic genesis, decided by natural geophysical
factor, climatic conditions as well as geological and lithologic and tectonic
factors.
V.P. Petrov considers that clays are of both sedimentary and chemical
geneses according the view of Millot and allogenic genesis according to the
view of Strakhov.
In the mineral research aspect, the post graduate student considers that the
view of V.P. Petrov is the most reasonable as it allows to explain the
paragenetic association of minerals with mixed composition from kaolinite to
montmorillonite.
3.1.2.2. Forming conditions of sedimentary kaolinite clays in East
Nam Bo region
The forming process of kaolinite clay deposits of good quality in East
Nam Bo region usually occurs in 2 stages: sedimentation and weathering
(bleaching ).
3.1.2.2.1. Sedimentation stage
Sedimentary clay deposits are product of chemical weathering from rocks
rich in feldspar or alumosilicate, transported and redeposited in places of favorable
geological and physico-chemical conditions.
To determine the forming conditions of kaolinite clays of sedimentary
genesis in East Nam Bo region, the post graduate student carried out the
following researches: Research on the composition and sorting of rock
fragments, research on the morphology of the mineral kaolinite in different
geologic formations, hence to infer the genesis of the sediments.
Research on the composition and sorting of rock fragments: To determine
the composition and sorting of rock fragment in the kaolinite bearing sediments
the author used the results of particle size distribution test of samples from
kaolinite clay deposits or from boreholes near the deposit.
To classify the clastic sedimentary rocks, the student used a ternary plot
for Quartz (Q)-Feldspar (F)-Rock fragments (R) developed by Pettijohn F.J
(1972). On this plot five areas corresponding with 5 different stages of
sedimentation :
1. Quartz sand - Deposition in plain area;
2. Arkosic sand - Deposition in midland area with the ratio F/R >1;
3. Greywacke sand - Deposition in midland area with the ratio F/R<1;
4. Arkosic sand - Deposition in mountain area near magmatic intrusive
massifs, with the ratio F/R>1;
5. Greywacke sand - Deposition in mountain area near volcanic
formations and metasedimentary rocks, with the ratio: F/R<1;
According sorting coefficient (So) the sediments are classified according
to Rukhin (1947):
So=1-1.58 well sorted - usually related to undisturbed depositional
environment (marine, lacustrine);
So = 1.58-2.12, medium sorted - related with disturbed dispositional
environment (surf zone, river mouths emptying to the sea or lake);
So > 2.12, poorly sorted - related with strongly disturbed depositional
environment (river bed, flood plain, terrace, eluvial, proluvial sediments).
Morphology of the mineral kaolinite: The morphology of the mineral
kaolinite in the sediments is determined by SEM method. As a result of
comparison between the kaolinite of weathering genesis and that in sediments
some remarks have been made as follows:
1. The kaolinite in sediments is similar to that of residual weathering
genesis in morphology so it can be considered as of weathering genesis.
2. The kaolinite in sediments still contain residual feldspar, so it con be
confirmed to be of chemical weathering genesis from rocks rich in
alumosilicates transported and deposited mechanically.
3.2. Distribution characteristics
3.2.1. Overview on distribution
In East Nam Bo region there are about 65 deposits and occurrences of
kaolinite clays and brick clays, of which 48 deposits and occurrences are of
kaolinite clays with 7 being of residual weathering genesis and 41 of
sedimentary genesis. Of the kaolinite clay deposits 12 are of big size, 11 of
medium size, 6 of small size, together with occurrences.
Due to their different forming conditions, each genetic type of kaolinite
clays in East Nam Bo region is of specific distribution characteristics.
Following are the main distribution characteristics of kaolinite clays East Nam
Bo region.
3.2.2. Differentiation of genetic types of kaolinite clays in East Nam
Bo region
Kaolinite clays in East Nam Bo region consist of 2 genetic types: residual
weathering and sedimentary.
3.2.2.1. Distribution characteristics of kaolinite clays of residual
weathering genesis
Kaolinite clays of residual weathering genesis in East Nam Bo region
originate from bed rocks aged Pre-Cenozoic, which include: sedimentary rocks
of claystone, mudstone and intrusive rock of granitoid.
3.2.2.1.1. Kaolinite clay of weathering genesis from claystone,
mudstone in lower - middle Jurassic(J1-2)
Of this type in East Nam Bo region there are deposits of big size and
occurrences (Table 3-6). Of these, the typical deposit is Minh Hung kaolinite
clay deposit. The geological section of Minh Hung kaolinite clay deposit
consists of two parts from top downwards as follows:
Upper part (the sediments of Ba Mieu formation) consists of 2 layers in
downward sequence:
Layer 1: Silty medium grained sand of gray, shallow gray color, where
sand accounts for 70 -80%, silt 20 -30%, with thickness 1.2-2m.
Layer 2: Silty sand, kaolin clay silt of grey white color, with high content
of rounded quartz gravel and pebble the size 0.5 -2cm, with a thickness 0.6 7.5m and in average 2.87m.
Lower part: Weathering crust of claystone, mudstone, in downward
sequence consisting of the following weathered zones:
Lithomarge zone: Kaolinite clay of white, white gray color, fine and
plastic, in some places with yellow mottles (weathering product layer), with a
thickness of 0.7 -7m and in average 2.56m
Saprolite layer: Incompletely weathered claystone, mudstone, with a
thickness of >1m.
Bedrocks: Claystone, mudstone.
3.2.2.1.2. Kaolinite clay of weathering genesis from Cretaceous
granodiorite (K)
Of this type in East Nam Bo region there are deposits of big size and
occurrences (Table 3-6), of which the typical one being described is the Suoi
Nuoc Vang kaolinite clay deposit. The geologic section of Suoi Nuoc Vang
kaolinite clay deposit in downward sequence consists of 2 parts as follows:
Upper part: is the sedimentary cover (Ba Mieu formation) consisting of
2 layers as follows:
Layer 1: Sandy silt of gray color, with a thickness of 0.0 -4.0m.
Layer 2: Silty sand containing kaolin with small amount of quartz grit,
gravel and pebble, with a thickness of 4.0 - 4.8m.
Lower part: is the weathering crust from intrusive rock of granodiorite,
in downward sequence consisting of the following zones:
Lithomarge zone: Sand of white grey color, passing into silty sand
containing kaolinite of white grey color (kaolinite clay product layer), with a
thickness of 1-2.6m.
Saprolite zone: Weathered silty sand of yellow gray color with white
spots, still bearing traces of incompletely weathered mineral of feldspar, with a
thickness of > 1m.
Bedrocks: Biotite-hornblende granodiorite of black gray color, massive
structure, medium grained, subhedral texture.
From the above geologic settings and distribution characteristics of
kaolinite clays, it is possible to draw out some prerequisites and signs for their
prospecting as follows:
Geomorphologic prerequisite: These deposits are usually distributed on
the surface of accumulation plains with elevation 50-80m. The minerals are
exposed along erosional slopes with slope angle 15-35o incising into the
planation surfaces.
Weathering crust prerequisite: These deposits are developed in the
residual weathering crust of sedimentary rocks of claystone, mudstone and
intrusive rock of granodiorite. Kaolinite clay minerals are mainly concentrated
in the lithomarge zone of clay weathering crusts.
3.2.2.2. Distribution characteristics of kaolinite clays of sedimentary
genesis in Cenozoic sediments
Kaolinite clays of sedimentary genesis in East Nam Bo region are
distributed in the following geologic formations:
3.2.2.2.1. Kaolinite clays distributed in the sediments of Ba Mieu
formation (N22bm)
Of this type in East Nam Bo region there are deposits of big, medium, small
sizes and occurrences, of which the typical one being described is the Ap 3 kaolinite
clay deposit, Minh Thanh commune, Chon Thanh district, Binh Phuoc province.
The geologic section of Ap 3 kaolinite clay deposit in downward sequence consists
of 3 layers in member 2 of Ba Mieu formation as follows:
Layer 1: Silty sand of gray to shallow grey color, in some places
containing plant detrituses, with a thickness of 1-3.9m and in average 1.9m.
Layer 2: Sand, kaolinite silty clay of gray, white grey, in some places
slightly motley color (kaolinite clay product layer), with a thickness of 0.0-9.5m
and in average 3m.
Layer 3: Sand, silt and clay with grit and pebbles of white grey color. The
pebbles are composed of quartz, well rounded, unevenly distributed, with a
thickness of 0.0-2.4m and in average 0.5m.
From the above geologic settings and distribution characteristics of the
kaolinite clays, it is possible to draw out prerequisites and signs for their
prospecting as follows:
Geomorphologic prerequisite: These kaolinite clay deposits are
distributed on the surface with gentle slope of 3-5o, with elevation
50-70m.
Stratigraphic prerequisite: Kaolinite clay occurs in the sand, silt and
clay in Layer 2 of member 2 of Ba Mieu formation (N22bm).
3.2.2.2.2. Kaolinite clays distributed in the sediments of Dat Cuoc
formation (aQ11dc)
Of this type in East Nam Bo region there are deposits of big size and
occurrences, of which the typical one being described is the Minh Long
kaolinite clay deposit. The geologic section of Minh Long kaolinite clay deposit
in downward sequence consists of 2 layers as follows:
Layer 1: Cloddy sand, silt and clay of motley light gray color, with a
thickness of 6.5 m.
Layer 2: Silty sand with quartz gravel and pebbles, kaolinite clay of grey,
brown and pink color (product layer), with thickness 6.5 m.
On the basis of the above geological settings and distribution
characteristics of kaolinite clays, it is possible to draw out prerequisites and
signs for their prospecting as follows:
Geomorphologic prerequisite: Kaolinite clay deposits occur on the
surface of horizontal landform (accumulation terrace level III), with elevation
35-50m.
Stratigraphic prerequisite: The kaolinite clay bearing stratigraphic unit
is layer 2 of alluvial sediments of Dat Cuoc formation (aQ11đc).
3.2.2.2.3. Kaolinite clay occurring in the sediments of Thu Duc
formation (aQ12-3tđ)
Of this type in East Nam Bo region there are deposits of big, medium,
small sizes and occurrences, of which the typically described is the Tan Quy
kaolinite clay deposit. The geologic section of Tan Quy kaolinite clay deposit in
downward sequence consists of 3 layers as follows:
Layer 1: Silty sand of gray, shallow yellow gray color, with a thickness of
0.5-2.3m and in average 1.0m.
Layer 2: Silty sand of yellow grey color, with laterite of motley red
brown color, in many places forming big, hard clods of red brown color, with a
thickness of 1.8-4.4 m and in average: 3.37m.
Layer 3: Sand, clay, silt with quartz pebbles and kaolinite of white, dirty
yellow colors (the kaolinite clay product layer), with a thickness of 2.3-7.2 m
and in average 5.25m.
From the above geological settings and distribution characteristics of
kaolinite clays, it is possible to draw out prerequisites and signs for their
prospecting as follows:
Geomorphologic prerequisite: Kaolinite clay deposits are exposed on
slope surfaces with slope angle 10-15o, where occurs strong infiltration
weathering process.
Stratigraphic prerequisite: The kaolinite clay bearing stratigraphic unit
is the clayey sand with pebbles (Layer 3) of alluvial sediments aged middle-late
Pleistocene of Thu Duc formation (aQ12-3tđ).
3.2.2.2.4. Kaolinite clays in the sediments of Cu Chi formation
(amQ13cc)
Of this type in East Nam Bo region there are deposits of small size and
occurrences, of which the typical one being described is the Thai My kaolinite
clay deposit. The geologic section of Thai My kaolinite clay deposit in
downward sequence consists of 3 layers as follows :
Layer 1: Silty sand of gray color (gray soil), with a thickness of 0.5-2m.
Layer 2: Laterized silty sand, silty clay of red brown color and laterite
clods, with a thickness of 1.1-4.1m.
Layer 3: Sand, silty clay with kaolinite, of muddy white, in some places
motley color (kaolinite clay product layer), with a thickness of 5.2-5.7m.
From the above geological settings and distribution characteristics of
kaolinite clays, it is possible to draw out prerequisites and signs for their
prospecting as follows:
Geomorphologic prerequisite: Kaolinite clay deposits occur on the
surface of erosion-accumulation depressions, with elevation 5-10m.
Stratigraphic prerequisite: The kaolinite clay bearing stratigraphic unit is layer
3 of alluvial-marine sediments aged late Pleistocene, Cu Chi formation (amQ13cc).
Chapter 4. MATERIAL COMPOSITION CHARACTERISTICS OF
KAOLINITE CLAYS IN EAST NAM BO REGION
4.1. Material composition characteristics kaolinite clays of residual
weathering genesis
Kaolinite clays of residual weathering genesis in East Nam Bo region
consist of two main types: kaolinite clays generated by weathering of lowermiddle Jurassic claystone, mudstone (J1-2) and kaolinite clays generated by
residual weathering of Cretaceous granodiorite (K).
4.1.1. Kaolinite clays generated by weathering of lower-middle
Jurassic claystone, mudstone (J1-2)
The average mineral composition of Minh Hung kaolinite clay deposit
(recovered through the 0.1mm mesh sieve) is: Kaolinite (kl): 40%, hydromica
(hmi): 16%, chlorite (cl): 5%, montmorillonite (mt): 0%, quartz (q): 32%,
feldspar (ft): 5%, goethite (gh): 6%.
The average chemical composition of Minh Hung kaolinite clay deposit
(recovered through the 0.1 mm mesh sieve) is shown in Table 4-2.
Table 4-2: Chemical composition of Minh Hung kaolinite clay deposit
Values
Min
Max
Average
Chemical composition (%)
SiO2
TiO2
Al2O3 Fe2O3 Na2O
K2O
CaO MgO LOI
65.98
0.77
19.1
0.35
0.05
1.57 0.12
0.09
5.52
71.00
0.93
21.4
0.94
0.05
1.68 0.12
0.58
6.87
69.35
0.88
19.85
0.61
0.05
1.63
0.12
0.34
6.09
4.1.2. Kaolinite clays generated by weathering of Cretaceous
granodiorite (K)
The average mineral composition of Suoi Nuoc Vang kaolinite clay
deposit (recovered through the 0.1 mm mesh sieve) is : kaolinite: 74%,
hydromica: 8%, chlorite: 5%, quartz: 3%, feldspar: 7%.
The average chemical composition of Suoi Nuoc Vang kaolinite clay
deposit (recovered through the 0.1 mm mesh sieve) is shown in Table 4-6.
Table 4-6: Chemical composition of Suoi Nuoc Vang kaolinite clay deposit
Values
Min
Max
Average
SiO2
46.54
46.68
46.61
TiO2
0.77
1.07
0.92
Chemical composition (%)
Al2O3 Fe2O3 Na2O K2O
35.49
1.02
0.03
0.08
37.70
3.03
0.07
0.27
36.29
2.24
0.05
0.15
MgO
0.03
0.13
0.09
LOI
13.41
13.83
13.56
4.2. Material composition characteristics of kaolinite clays of
sedimentary genesis
In East Nam Bo region kaolinite clays are rather common, forming layers
and seams lying with conformity in the following sediments
4.2.1. Material composition characteristics of kaolinite clays of
sedimentary genesis in Ba Mieu formation (N22bm)
The average mineral composition of Ap 3 kaolinite clay deposit
(recovered through the 0.1 mm mesh sieve) is: kaolinite: 42%, hydromica: 15%,
chlorite: 6%, quartz: 31%, feldspar: 5%.
The average chemical composition of Ap 3 kaolinite clay deposit
(recovered through the 0.1 mm mesh sieve) is shown in Table 4-11.
Table 4- 11: Chemical composition of Ap 3 kaolinite clay deposit
Values
Min
Max
Average
Chemical composition (%)
SiO2 TiO2 Al2O3 Fe2O3 Na2O K2O CaO MgO LOI
61.3 0.55 16.62
0.51 0.05 0.35
0
0
5.0
73.36 1.53 25.71
1.51
0.6
1.6
2.26 0.31
8.3
67.42 0.93 20.96
0.94 0.18 1.22
0.44 0.17 6.84
4.2.2. Material composition characteristics of kaolinite clays of
sedimentary genesis in the sediments of Dat Cuoc formation (aQ11đc)
The average mineral composition of Minh Long kaolinite clay deposit is
(%): kaolinite 33; hydromica 15; quartz 35; feldspar 5.
The average chemical composition of Minh Long kaolinite clay deposit
(recovered through the 0.1mm mesh sieve) is shown in Table 4-16.
Table 4-16: Average chemical composition of Minh Long kaolinite clay
deposit
Values
Min
Max
Average
Chemical composition (%)
SiO2 TiO2 Al2O3 Fe2O3 Na2O K2O MgO CaO LOI
57.18 0.87 17.74 0.47 0.06 0.75 0.04
0
5.93
72.88 1.2 28.09 1.18 0.17 2.41 0.54 0.37 10.74
65.74 1.00 22.86 0.74 0.12 1.19 0.26 0.08 7.59
4.2.3. Material composition characteristics of kaolinite clays of
sedimentary genesis in the sediments of Thu Duc formation (aQ12-3tđ)
The average mineral composition of Tan Quy kaolinite clay deposit
(recovered through the 0.1 mm mesh sieve) is: Kaolinite: 19%, hydromica: 12%,
chlorite: 5%, montmorillonite: 4%, quartz: 52%, feldspar: 5%, goethite: 3%.
The average chemical composition of Tan Quy kaolinite clay deposit
(recovered through the 0.1 mm mesh sieve) is shown in Table 4-20.2.
Table 4-20.2: Chemical composition of Tan Quy kaolinite clay deposit
Values
Min
Max
Average
Chemical composition (%)
SiO2 TiO2 Al2O3 Fe2O3 Na2O K2O MgO
69.14 0.60 15.30 0.34 0.15 0.50 0.17
74.16 1.09 20.11 3.10 0.25 1.33 2.00
72.21 0.79 16.89 1.37 0.20 0.90 0.66
CaO
0.18
0.18
0.18
LOI
5.39
6.66
5.89
4.2.4. Material composition characteristics of kaolinite clays of
sedimentary genesis in the sediments of Cu Chi formation (aQ13cc)
The mineral composition of Thai My kaolinite clay deposit is: kl: 20.023.0%, in average: 22%; Hydromica: 12 - 15%, in average: 14%; chlorite: 4-6%
and in average: 4%; montmorillonite: 3-5%, in average: 4%; q: 34-48%, in
average: 41%; feldspar: 5%, in average: 5%; goethite: 5-13%, in average: 9%.
The chemical composition of Thai My kaolinite clay deposit (recovered through
the 0.1 mm mesh sieve) is shown in Table 4-24.2.
Table 4-24.2: Chemical composition of Thai My kaolinite clay deposit
Chemical composition (%)
Values
SiO2
Al2O3 Fe2O3
K2O MgO LOI
TiO2
Na2O
Min
64.78 0.78 20.28 1.02 0.05 1.17 0.26 6.45
Max
68.5 0.82 22.91 1.4
0.25 1.58 1.0 7.71
Average
66.33 0.80 21.77 1.22 0.16 1.32 0.52 7.27
Chapter 5. TECHNICAL PROPERTIES AND POSSIBLE USES OF
KAOLINITE CLAYS IN EAST NAM BO REGION
5.1. Technical properties
According the material composition characteristics of the kaolinite clays
in East Nam Bo region (Chapter 4), almost all original materials do not meet
the criteria for mineral raw material. Therefore, ion this section the author of the
Thesis examines only the technical properties of the raw materials recovered
through the 0.1mm mesh sieve.
5.1.1. Technical properties of kaolinite clays of residual weathering
genesis
These deposits and occurrences consist of two main types: those
generated by weathering of lower-middle Jurassic claystone, mudstone (J1-2)
and those generated by weathering of Cretaceous granodiorite (K).
5.1.1.1. Technical properties of kaolinite clays of weathering genesis
originating from claystone, mudstone
The technical properties of Minh Hung kaolinite clay deposit are: Particle
size distribution (%): Sand: 46.5-60.5, in average 50.9; silt: 16-42.5, in average
30.4; clay: 39.5-53.5, in average 49.1. Recovery (%): 72.1-99.1, in average
86.3. Thickness (m): 0.7-4.0, in average 2.0.
The results of technical samples test (recovered through the <0.1mm
mesh sieve and burned at temperature of 1250oC) of Minh Hung kaolinite clay
deposit are as follows (%): plasticity: 15.3-17.1, in average 16.2 (of high
plasticity); total shrinkage: 9.8-10.3, in average 10.05; water absorption: 12.412.9, in average 12.65; bending strength (kg/cm2): 170-178, in average 174;
whiteness: 69-68, in average 68.5.
1.1.1.2. Technical properties of kaolinite clays of weathering genesis
from granodiorite aged Cretaceous (K)
Technical properties of Suoi Nuoc Vang kaolinite clay deposit are as
follows: Particle size distribution (%): sand: 16.68-41.7, in average 26.2; silt:
9.7-29.7, in average 18.4; clay: 29.0-44.7, in average 36.7. Recovery (%):
52.95-71.05, in average 63,86. Thickness (m): 0.6-4.7, in average 2.0.
The results of technical tests of kaolinite clay in Suoi Nuoc Vang deposit
(recovered through the 0.1 mm mesh sieve and burned at temperature of
1250oC) are as follows (%): plasticity: 19.8-40.5, in average 29.5; shrinkage after
heating: 5.8-6.9, in average 6.4; after heating: 9.9-11.2, in average 10.6; total:
15.7-18.7, in average 17.0; water absorption 14.1-22.4, in average 16.7; bending
strength (kg/cm2): 51-127, in average 89; whiteness: 54-67, in average 57.
5.1.2. Technical properties of kaolinite clay deposits of sedimentary
genesis
5.1.2.1. Technical properties kaolinite clay deposits in the sediments
of Ba Mieu formation
Technical properties of Ap 3 deposit: Particle size distribution (%): Sand:
30.5-73.5, in average 59.1; silt: 4.7-40, in average 12.3; clay: 19.5-42.0, in
average 28.6. Recovery (through <0.1mm mesh sieve) (%): 27.5-95.5, in
average 47.8. Thickness (m): 0.5-7.0, in average 2.6.
The results of technical tests of kaolinite clays of Ap 3 deposit (recovered
through the 0.1 mm mesh sieve and burned at temperature of 1250oC) are as
follows : plasticity: 14.7-20.7, in average 16.8; shrinkage: after heating: 3.5-5.6,
in average 4.4; after heating: 0.38-7.9, in average 6.0; total: 4.87-12.55, in
average 10.1; water absorption 7.8-18.8, in average 11.3; bending strength
(kg/cm2): 81-202, in average 135; whiteness: 55-71, in average 67.
5.1.2.2. Technical properties of kaolinite clays in the sediments of Dat Cuoc
formation
Technical properties of the Minh Long kaolinite clay deposit: Particle size
distribution (%): sand: 0.1-80.25, in average 51.72; silt-clay: 19.7-99.9, in
average 47.79. Recovery (%): 21.5-99.95, in average 55.15. Thickness (m): 6.219.6, in average 13.7.
The results of technical tests of kaolinite clays of kaolinite clay deposits
and occurrences of sedimentary genesis in the sediments of Dat Cuoc formation
(recovered through the 0.1 mm mesh sieve and burned at 1250oC): Plasticity
index 7-18.8; shrinkage after heating 0.75; water absorption after heating 18.124.6; whiteness after heating 64-67%.
5.1.2.3. Technical properties of kaolinite clays in Thu Duc formation
Technical properties of Ta Quy kaolinite clay deposit: Particle size
distribution (%): sand: 12.8-73.37, in average 48,1; silt: 5.7-34.83, in average
14.55; clay: 17.64-52.37, in average 37.35. Recovery (%): 37.66-73.75, in
average 58.64. Thickness (m): 3.6-8.2, in average 5.69.
The results of technical tests of kaolinite clays in kaolinite clay deposits
and occurrences of sedimentary genesis in the sediments of Thu Duc formation
(recovered through the 0.1 mm mesh sieve and burned at 1250oC): Plasticity
index 9-30.1; shrinkage after heating 1.0-27.6%; molding moisture 14.9-
30,8%; shrinkage after heating 0.75; water absorption after heating (at 950oC
and 1050oC) 11.86 and 10.89-18.0%; compressive strength (at 950oC and
1050oC) 89-289.7 and 123-321.39 kg/cm2.
5.1.2.4. Technical properties of kaolinite clays in Cu Chi formation
Technical properties of Thai My kaolinite clay deposit are as follows:
Particle size distribution (%): sand: 29.9-57.2, in average 48.9; silt: 10.7-40.2,
in average 25.9; clay: 10.9-58.9, in average 25.0. Recovery (%): 40.2-45, in
average 43. Thickness (m): 4.0-7.0, in average 5.6.
5.2. Possible uses of kaolinite clays in East Nam Bo region
5.2.1. Minimum criteria for mineral quality
The minimum quality criteria for kaolinite clays are as follows: Al2O3
content in kaolin passing 0.21mm mesh sieve: ≥ 17%; total iron oxide content:
≤ 1.7%; Recovery: ≥ 20%; thickness: ≥ 1m.
Based on the results of researches on material composition, technical
properties, the kaolinite clay deposits and occurrences in East Nam Bo region
have met the above minimum quality criteria.
5.2.2. Quality criteria for raw materials according their uses
Depending on the uses and industrial requirements for quality of raw
materials, based on Russian standard GOST 9169-59 and Vietnamese
construction standard TCVN 6300, 6301 in 2006, it is recognized that the
kaolinite clays in East Nam Bo region have met the standards as raw materials
for ceramic and refractory products.
The weathering kaolinite clay raw material originating from granitoid
aged Cretaceous (K) can be used for producing refractory bricks. (It is of basic
composition: Al2O3+TiO2 content: 32.59+1.05= 33.64 > 30% (standard); Fe2O3:
0.34-2.5%; in average 1.58% (standard: not more than 1.5 - 2%).
Thus, the weathering kaolinite clay originating from granitoid aged
Cretaceous can be used as raw material for producing refractory bricks.
CONCLUSION AND RECOMMENDATIONS
CONCLUSION
The research results of the Thesis have allowed the author to make the
following main conclusions:
1- The kaolinite clays in East Nam Bo region are of two genetic types:
Residual weathering genesis and sedimentary genesis.
1.1. The kaolinite clays of residual weathering genesis in East Nam Bo
region were formed in the process of chemical weathering from the rocks rich
in alumosilicates, on erosional surfaces with elevation 50 to 80m with slope
angle 15-35o, in the humid tropical climatic condition.
The kaolinite clays of residual weathering genesis occur in the lithomarge
zone of the argillaceous weathering crust developed on lower-middle Jurassic
terrigenous sedimentary rocks (J1-2) and Cretaceous granodiorites (K).
1.2. The kaolinite clays of sedimentary genesis in Cenozoic sediments
were formed mainly by mechanical deposition process in the continental
environment of river terraces, deltas etc.
The kaolinite clays of sedimentary genesis occur mainly in layers of sand,
silt, clay with quartz gravel and overlain by layers of silt, clay, sand, belonging
to the following sediments :
Upper Pliocene sediments of Ba Mieu formation (N22bm), occurring on
gentle slopes of 3-5o, with elevation 50-70m.
Lower Pleistocene alluvial sediments of Dat Cuoc formation (aQ11dc),
occurring on horizontal surface, (accumulation terrace level III), with elevation
35-50m.
Middle - upper Pleistocene alluvial sediments of Thu Duc formation
2-3
(aQ1 td), exposed on the slopes of 10-15o.
Upper Pleistocene alluvial-marine sediments of Cu Chi formation
(amQ13cc), occurring on the erosion-accumulation depression surface, with
elevation 5-10m.
1.3. The kaolinite clay deposits of sedimentary genesis in Quaternary
sediments (Dat Cuoc, Thu Duc and Cu Chi formations), which are of good
quality, have undergone the infiltration weathering (bleaching) process.
2- The white clays in East Nam Bo region indeed are not kaolin. They are
polymictic clays with rather high kaolinite content (20-75%), so they can be
classified as kaolinite clays.
3- The kaolinite clays in East Nam Bo region are of medium to high
quality, high processability and high recovery, so they can be processed into
raw materials to be used in ceramic and refractory material production
industries.
RECOMMENDATIONS
1- For research work
The kaolinite clays in East Nam Bo region are of great potential and have
been for a long time the main mineral raw materials for ceramic production. In
practice kaolinite clays usually contain many harmful substances such as Fe2O3,
TiO2… making them not meeting the standard for high quality products.
Therefore, research should be carried out to select the appropriate processing
technology for this potential source of raw material.
2- For the investigation and assessment of kaolinite clays in East Nam
Bo region
In East Nam Bo region, investigation and assessment of kaolinite clays
have been carried out by geological mapping divisions under the General
Department of Geology and Minerals of Vietnam in the geological mapping
projects at various scales 1: 500,000, 1: 200,000 and 1: 50,000 or by private
companies in their mining exploration projects.
To serve the planning for appropriate exploitation and use of kaolinite clays in
the region, it is recommended to initiate a project for comprehensive investigation to
evaluate the extent, quality and potential of this type of mineral resource.