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UNIVERSITI TEKNOLOGI MARAFAKULTI KEJURUTERAAN KIMIA

GEOLOGY AND DRILLING LABORATORY(CGE 558)

NAME : MOHAMMAD FAIZUAN BIN ISMAIL 2013252638 EXPERIMENT :THIN SECTION AND PETROGRAPHYDATE PERFORMED :4 NOVEMBER 2014 SEMESTER :3 PROGRAMME/CODE : CGE 558 GROUP : EH223 3A

No. Title Allocated marks % Marks %1 Abstract/Summary 5

2 Introduction 53 Aims/Objectives 54 Theory 55 Apparatus 56 Procedure 107 Results 108 Calculations 109 Discussion 2010 Conclusions 1011 Recommendation 512 References 513 Appendices 5

Total 100

Remarks: Checked by:

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1.0 ABSTRACT

Thin section and petrography can serve a number of functions in studies of cultural object.

This experiment is a way of method which the physical characteristic and texture of the rockand minerals can be observed under the microscope for study purposes. By observing therock sample under the microscope, the rock and minerals features can be identified such ascolor, reflectance, cleavage, and shape. The experiment was conducted by carefully cuttingthe provided rock into a smaller sample using the cutting machine. The desired sample withthe cross-sectional area of 4mm are then polished using a piece of sandpaper in order toremove the bubble layers on the rocks surface. The desired rock sample was glued to theglass slide by using thermoplastic cement. The thin section lapping was set up and then thesample was placed in order to minimize the thickness to 30m. The sample was thenobserved by using the microscope by using 4x, 10x, 20x, and 40x magnification. The rocksample was interpreted based on its characteristic observed under the microscope.

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2.0 INTRODUCTION

Thin sections facilitate microscopic study under bright field or polarized transmitted lightto determine the characteristic, texture, and structure of the sample rock. There are threetypes of rock that can be identified which is igneous, metamorphic and sedimentary rocks. Italso study the interpretation of the environment in which they are formed. This study willfurther completed with the polarizing microscope. Polarizing microscope is a important toolwhich are used to study the thin section rocks minerals and a method of learning tocharacterize, recognize and identify the type of observed rock. Basically, there are manytypes of physical features that can be observed to identify the minerals, which are shaping,grain size, colour, refractive index and cleavage. But the special features of the polarizing

microscope are covered extinction, birefringence and pleochrosim.

Recognizing minerals and understanding their structure is the basis for recognizing rocksand interpreting micro textures to learn how they were formed. Evidence gathered by deepstudy of minerals in thin sections is a important part of the interpretation of igneous,metamorphic and sedimentary rocks. While modern Earth Sciences departments useexpensive and sophisticated electronic equipment which to study the minerals and the typesof rocks, the polarizing microscope remains an important tool in petrology which is to studyof rocks. By identifying minerals and examining their interrelationships, petrographicevidence can be used to identify rocks and figure out how they formed.

There are three major groups of rocks which is sedimentary, igneous, and metamorphicrocks. Sedimentary rocks are those that have formed when eroded particles of other rockshave been deposited (on the ocean floor, stream/lake beds, etc) and compacted, or by the

precipitation of minerals / mineraloids from water. Igneous rocks are those that have formed by the cooling and crystallisation of magma, either at the Earth's surface or within the crust. Metamorphic rocks are those that have formed when existing rocks have undergone pressureand / or temperature changes so that their original mineralogy has been changed.

For each of these rock groups consists many different types of rock, and each has its own

physical features. Important information regarding the nature of rocks is communicatedthrough concise, accurate descriptions. This information allows the geologist to identify therock, and in the process, to learn about its history and the geological environment in which itwas formed.

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3.0 OBJECTIVE

1. To determine the provided rock sample by identifying minerals physical feature in across section of rock sample under a microscope.

4.0 THEORY

Thin sections are made from small slabs of a rock sample glued to a glass slide (~1 inch by 2

inches), and then ground to a specified thickness of 0.03mm (30 microns). At this thickness

most minerals become more or less transparent and can then be studied by a microscope

using transmitted light. Thin sections are time consuming and costly to prepare.

The environment of formation produces characteristic textures in igneous rocks which aid in

their identification. These textures are:

Eutaxitic (applies only to welded ignimbrites) - This texture describes a rock with a

planar fabric in which flattened pumice clasts are surrounded by a fine grained

groundmass of sintered ash. The flattened pumice clasts are lenticular (lens-shaped) in

cross-section and are called fiamme (Italian for flame). An eutaxitic texture is

developed when hot, pumice-rich material is erupted explosively and is then

compressed by overlying material while still in a hot, plastic state.

Porphyritic - This texture describes a rock that has well-formed crystals visible to the

naked eye, called phenocrysts, set in a very fine grained or glassy matrix, called the

groundmass. A porphyritic texture is developed when magma that has been slowly

cooling and crystallizing within the Earth's crust is suddenly erupted at the surface,

causing the remaining uncrystallized magma to cool rapidly. This texture is

characteristic of most volcanic rocks.

Phaneritic - This texture describes a rock with large, easily visible, interlocking

crystals of several minerals. The crystals are randomly distributed and not aligned in

any consistent direction. A phaneritic texture is developed by the slow cooling and

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crystallization of magma trapped within the Earth's crust and is characteristic of

plutonic rocks.

Aphanitic - This texture describes very fine grained rock where individual crystals can

be seen only with the aid of a microscope, i.e. the rock is mostly groundmass. An

aphanitic texture is developed when magma is erupted at the Earth's surface and cools

too quickly for large crystals to grow. This texture is exhibited by some volcanic

rocks.

The chemical composition of the magma determines which minerals will form and in what

proportions they will occur. Therefore, identification of the minerals present in the rock is an

important step in being able to correctly identify the rock. Magmas that are relatively low in

silica (SiO2) crystallize olivine, pyroxene (augite) and calcium-rich plagioclase, while

magmas that are high in SiO2 crystallize quartz, sodium-rich plagioclase, orthoclase, biotite

and hornblende. As with minerals, igneous rocks can be broadly divided into mafic and felsic

types. Mafic rocks are generally darker, and have higher abundances of mafic minerals.

Felsic rocks are generally lighter in color, having a higher concentration of felsic minerals.

There are two major groupings of sedimentary rocks:

Clastic sedimentary rocks

The fragments of pre-existing rocks or minerals that make up a sedimentary rock are

called clasts. Sedimentary rocks made up of clasts are called clastic (clastic indicates

that particles have been broken and transported). Clastic sedimentary rocks are

primarily classified on the size of their clasts.

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Table 2.1 : Clast size in clastic rocks

Name Grade Size range (mm) Comments

Boulder > 200

Clasts should be identifiable.Gravel

Very coarse 60 200

Coarse 20 60

Medium 6 20

Fine 2 6

Sand

Coarse 0.6 2Clasts visible to the naked eye.

Grains often identifiable.Medium 0.2 0.6

Fine 0.06 0.2

Mud < 0.002 0.06Clasts not visible to the naked eye.

Feels smooth.

Clast shape, or the degree of rounding of clasts, is important in differentiating some

sedimentary rocks. Clasts vary in shape from rounded to angular, depending on the

distance they have been transported and / or the environment of deposition, e.g.

rounded clasts are generally the product of long transportation distances and / or

deposition in high energy environments (beaches, rivers).

The degree of sorting of clasts can be an important indicator of depositional

environment. In water, larger clasts are generally not transported great distances, and

they settle faster. For example, in a mixture of mud and sand being transported in a

river to the sea, the sand (larger clast size, heavier) would begin to deposit as soon as

the river's energy dissipated, while the mud (fine, light-weight) would be transported

far off shore. Therefore, a well sorted (clasts of approximately the same size); coarse

sandstone indicates deposition in a reasonably high energy environment (near-shore)

probably close to the source of the sand. Conversely, a mudstone generally indicates

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deep water deposition (low energy environment, far off shore). Structures produced

during deposition, e.g. bedding and cross-bedding, can give clues as to depositional

environment. So can structures produced by re-working by tidal or storm-generated

currents, e.g. ripple marks, rip-up clasts.

Non-clastic sedimentary rocks

These sedimentary rocks occur when minerals / mineraloids are precipitated directly

from water, or are concentrated by organic matter / life. Components have not been

transported prior to deposition. No clasts are present.

The two distinctive metamorphic textures are:

Foliation - This represents a distinct plane of weakness in the rock. Foliationis caused by the re-alignment of minerals when they are subjected to high pressure and

temperature. Individual minerals align themselves perpendicular to the stress field

such that their long axes are in the direction of these planes (which may look like the

cleavage planes of minerals). Usually, a series of foliation planes can be seen parallelto each other in the rock. Well developed foliation is characteristic of most

metamorphic rocks. Metamorphic rocks often break easily along foliation planes.

Granular - This describes a metamorphic rock consisting of interlocking equantcrystals (granules), almost entirely of one mineral. A granular texture is developed if a

rock's chemical composition is close to that of a particular mineral. This mineral will

crystallise if the rock is subjected to high pressure and temperature. A granular texture

is characteristic of some metamorphic rocks.

Note : As the grade of metamorphism increases (more temperature and pressure), both crystal

size and the coarseness of foliation increase. Therefore, gneiss represents more intensemetamorphism (or a higher grade) than does schist. Some fine-grained metamorphic rocks,

http://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/index.htmlhttp://setcookie%28%27mineraloids%27%2C%27../minerals/index.html');http://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/index.htmlhttp://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/gneiss.htmlhttp://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/schist.htmlhttp://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/schist.htmlhttp://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/gneiss.htmlhttp://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/index.htmlhttp://setcookie%28%27mineraloids%27%2C%27../minerals/index.html');http://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/index.html

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e.g. schist, have larger crystals present. These crystals are

called porphyroblasts. Porphyroblasts represent minerals that crystallise at a faster rate than

the matrix minerals. Garnet is a common porphyroblast mineral.

Table 2.2: Guide to the classification of metamorphic rocks by texture

Grain size Fine Medium Coarse

Poorly foliated Hornfels Marble, quartzite Marble, quartziteWell foliated Slate Schist Gneiss

Well foliated and sheared Mylonite Mylonite, schist Augen gneiss

Thin sections are time consuming and costly to prepare. Thin sections are viewed

using a petrographic microscope under two different lighting conditions- plain polarized light

and crossed polarizer. Plane polarized light is light that is constrained to a single plane. The

light wave is a simple sine wave that has the vibration direction lying in the plane of

polarization. When viewing under plane polarized light, a single polarizer (lower polar) is

used. Inserting the upper polarizer is referred to as crossed polarizer (or, crossed nicols), the

name given because the two polarizing lenses are set at right angles to each other. Minerals

can be classified as anisotropic or as isotropic, depending on their light properties. Isotropic

minerals show the same velocity of light in all directions, while anisotropic minerals show

the velocity of light varying in different orientations. The absorption color in plane polarized

light - this is not the same as the color of the mineral in hand specimen. Most minerals are

colorless in thin section. Some are opaque, light cannot pass through them and they appear

black, so we cannot identify them using this type of microscopy. Magnetite, hematite and

pyrite are opaque. Chlorite is green, Biotite is brown.

http://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/schist.htmlhttp://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/garnet.htmlhttp://flexiblelearning.auckland.ac.nz/rocks_minerals/minerals/garnet.htmlhttp://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/schist.html

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5.0 APPARATUS AND MATERIALS

APPARATUS

1. The rock cutting machine2. Sand paper3. The thin section lapping machine4. Glass slide5. Hotplate6. The polarizing microscope

MATERIALS

1. Rock sample2. Thermoplastic cement

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6.0 PROCEDURE

1) A sample rock was chosen to be used in the experiment. The rock was then secured

between the clamps in the rock cutting machine in a way of not too tight and not tooloose.

2) The lid was closed and the machine was switched on. The thickness was set to 4mmand the water pump of the cutting rock machine was switched on for the bladescooling purposes while cutting the rock.

3) The start button was pushed and the blade was lowered until it reaches the rock andslowly cutting through the rock to obtain a clear, smooth rock sample.

4) The rock sample was then cleaned with sand paper to remove the bubble layer on therocks surface so that the sample can be perfectly glued to the glass slide.

5) The glass slide was then placed on the hot plate. The temperature of the hot plate wasincreased so that it can melt down the applied thermoplastic cement.

6) The sample was placed on the glass slide and the temperature was lowered down forthe thermoplastic cement to cool down and bind the sample on the glass slide.

7) The sample was then placed on the thin section lapping machine to minimize thethickness of the rock sample to 30m.

8) Lastly, the sample was then being observed under the microscope. The knob or thefine focus were used to focus the image of the slide, the illumination intensity,

polarizing part, position sample and filter was used to get better image.9) The sample was magnified into 4x, 10x, 20x, and 40x. the result was recorded ad

observed.

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7.0 RESULT

MAGNIFIED 40X

MAGNIFIED 20X

MAGNIFIED 4X

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MAGNIFIED 10X

8.0 DISCUSSION

From the experiment conducted, the sample is examined by using polarizingmicroscope for identification type of rock with four type of magnification which are 4x, 10x20x and 40x. These four type of magnification is used to help students in details ondetermining type of rock on a particular sample.

From the result that has been recorded, it is clearly showed that the sample consistedseveral types of component that related to sandstone characteristics. These characteristicsincluded the grains that is made up of several type of minerals, pores space that can be seenclearly, matrix and also cementation. The colour also white as it indicate sandstone. Thelimitation to this experiment is that the result of sample is not very clearly to be seen as themagnification increase compared with the result source from internet. This make theidentification of rock when it gets closer is not very helpful maybe due to our microscopetechnology is not really advance to be compared with technology used by many researchersthat uploaded their result on internet.

But when the image capture at 10x magnification is compared with the image captured by geoscientist via internet source, the differences between our image, grains, matrices andcements could not be distinguished and the colour quietly similarly to the grains. Only porecan distinguished clearly. The microphotograph was also compared shows that the it was ametamorphic quartz . pink and brownish colored show the calcite cement.

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9.0 CONCLUSION

In conclusion, the study of rocks and minerals using a microscope and cross section are

useful for identification of rocks, minerals to achieved. Rock minerals can be identifieddepends on its color, hardness, shape, weights, cleavage, fracture, taste and etc. Microscopeare used to reflect the color of minerals in rocks. Its also can be identified all of the typeminerals content in reservoir and also can be observed to know if it is good porosity or

permeability to be a good reservoir

10.0 RECOMMENDATION

1) While cutting the rock sample using the rock cutting tool, lower the blade slow andcarefully so that the rock will not break into pieces.

2) Make sure the not to clamp the rock sample either too tight or too loose in the cuttingrock machine to avoid from cutting failure.

3) Clean the rock sample evenly with sand paper to completely remove the bubble layerson the rocks surfaces.

4) Reduce the thickness to the range where light is able to go through the minerals to

assist in observation of the rock sample under the microscope.5) Spread the thermoplastic cement evenly on the glass slide so that it covers the whole

rock surface and it would not wears off during thinning process by using the thinsection lapping machine.

6) Wear gloves to hold the glass slide after it is heated onto the hot plate and make surethere is no bubble between the glued area.

7) Adjust the light intensity to get a clearer image while doing the observation under the polarized light microscope.

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11.0 REFERENCES

1. http://wiki.answers.com/Q/What_are_the_texture_characteristics_and_formation_

of_basalt

2. http://geology.isu.edu/geostac/Field_Exercise/Cassia_mtns/thinsect.html

3. http://earth.s.kanazawa-u.ac.jp/ishiwata/min_ide.htm

4 http://www.open.edu/openlearn/science-maths-technology/science/introduction-

minerals-and-rocks-under-the-microscope/content-section-2.1

5 http://geology.utah.gov/surveynotes/gladasked/gladrocks.htm

http://wiki.answers.com/Q/What_are_the_texture_characteristics_and_formation_of_basalthttp://wiki.answers.com/Q/What_are_the_texture_characteristics_and_formation_of_basalthttp://wiki.answers.com/Q/What_are_the_texture_characteristics_and_formation_of_basalthttp://wiki.answers.com/Q/What_are_the_texture_characteristics_and_formation_of_basalthttp://wiki.answers.com/Q/What_are_the_texture_characteristics_and_formation_of_basalthttp://geology.isu.edu/geostac/Field_Exercise/Cassia_mtns/thinsect.htmlhttp://geology.isu.edu/geostac/Field_Exercise/Cassia_mtns/thinsect.htmlhttp://earth.s.kanazawa-u.ac.jp/ishiwata/min_ide.htmhttp://earth.s.kanazawa-u.ac.jp/ishiwata/min_ide.htmhttp://www.open.edu/openlearn/science-maths-technology/science/introduction-minerals-and-rocks-under-the-microscope/content-section-2.1http://www.open.edu/openlearn/science-maths-technology/science/introduction-minerals-and-rocks-under-the-microscope/content-section-2.1http://www.open.edu/openlearn/science-maths-technology/science/introduction-minerals-and-rocks-under-the-microscope/content-section-2.1http://www.open.edu/openlearn/science-maths-technology/science/introduction-minerals-and-rocks-under-the-microscope/content-section-2.1http://www.open.edu/openlearn/science-maths-technology/science/introduction-minerals-and-rocks-under-the-microscope/content-section-2.1http://geology.utah.gov/surveynotes/gladasked/gladrocks.htmhttp://geology.utah.gov/surveynotes/gladasked/gladrocks.htmhttp://geology.utah.gov/surveynotes/gladasked/gladrocks.htmhttp://www.open.edu/openlearn/science-maths-technology/science/introduction-minerals-and-rocks-under-the-microscope/content-section-2.1http://www.open.edu/openlearn/science-maths-technology/science/introduction-minerals-and-rocks-under-the-microscope/content-section-2.1http://earth.s.kanazawa-u.ac.jp/ishiwata/min_ide.htmhttp://geology.isu.edu/geostac/Field_Exercise/Cassia_mtns/thinsect.htmlhttp://wiki.answers.com/Q/What_are_the_texture_characteristics_and_formation_of_basalthttp://wiki.answers.com/Q/What_are_the_texture_characteristics_and_formation_of_basalt

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Polarized Light Microscope with its part

Polarized Light Microscope in lab

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