geological cycle rock formation and types of rock-2 ( sedimentary &metamorphic rocks )

7/25/2019 Geological Cycle Rock Formation And Types of Rock-2 ( Sedimentary &Metamorphic Rocks )

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Geological Cycle Rock Formation And Types of Rock-2

( Sedimentary &Metamorphic Rocks

!nstr"ctor#

$r% Atta"llah Shah

Lecture # 5

$epartment of Ciil 'ngineering

Swedish College of Engineering and Technology-Wah Cantt.
http://en.wikipedia.org/wiki/File:Rockcycle.jpg


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1. Classification of sedientary !oc"

2. escri$tion of coon sedientary roc"

3. Ty$es of etaor$his

%. escri$tion of coon etaor$hic roc"

"tlines of the )resentation"tlines of the )resentation
http://upload.wikimedia.org/wikipedia/commons/0/08/Triassic_Utah.JPGhttp://upload.wikimedia.org/wikipedia/commons/0/08/Triassic_Utah.JPG


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Sedimentary rock is a ty$e of roc" that is fored &y

sedientation of aterial at the Earth's surface and within &odies

of water.

Sedientation is the collecti(e nae for $rocesses that cause

ineral and)or organic $articles *detritus+ to settle and accuulate

or inerals to $reci$itate fro a solution.

,articles that for a sedientary roc" &y accuulating are called

sedient. efore &eing de$osited sedient was fored &y

weathering and erosion in a source area and then trans$orted to

the $lace of de$osition &y water wind ass o(eent or

glaciers.

Classification of Sedimentary RocksClassification of Sedimentary Rocks


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Sedientary roc" is fored &y de$osition and consolidation of inerals and

organic aterials and fro $reci$itation of inerals fro solution. The

$rocesses that for sedientary roc" occur at the surface of the earth and

within &odies of water.

!oc" fored fro sedients co(ers /0-0 of the earths land area and

includes coon ty$es such as liestone chal" sandstone congloerate and

shale.

Sedientary roc"s are only a thin (eneer o(er a crust consisting ainly of

igneous and etaor$hic roc"s and constitute a total of 5 of the earth crust

(olue.

Sedientary roc"s are de$osited in layers as strata foring a structure called

&edding. The study of sedientary roc"s and roc" strata $ro(ides inforation

a&out the su&surface that is useful for ci(il engineering for e4a$le in the

construction of roads houses tunnels canals or other constructions.

Sedientary roc"s are also i$ortant sources of natural resources li"e coal

fossil fuels drin"ing water or ores.



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The scientific disci$line that studies the $ro$erties and origin of sedientary

roc"s is called sedientology.

Sedientology is &oth $art of geology and $hysical geogra$hy and o(erla$s

$artly with other disci$lines in the Earth sciences such as $enology

geoor$hology geocheistry or structural geology.

The study of the se6uence of sedientary roc" strata is the ain source forscientific "nowledge a&out the Earth's history including $alaeogeogra$hy

$aleocliatology and the history of life.



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Mechanically formed7 consisting of aterials *gra(els sand silt and clay+

sus$ended in flowing water. The sus$ended aterials are then de$osited and

consolidated.

Water $ercolates into crac"s and fissures within the roc" free8es and

e4$ands. The force e4erted &y the e4$ansion is sufficient to widen crac"s and

&rea" off $ieces of roc". 9eating and cooling of the roc" and the resulting

e4$ansion and contraction also aids the $rocess. :echanical weathering

contri&utes further to the &rea"down of roc" &y increasing the surface area

e4$osed to cheical agents.

The echanically fored sedientary roc"s are of three ty$es7

1. !udaceous roc"s which is the ceenting together of &oulders for e4a$le

congloerate.

2. ;renaceous roc"s for e4a$le sandstone

3. ;rgillaceous roc"s which is clay roc"s for e4a$le shale

http://upload.wikimedia.org/wikipedia/commons/e/e3/OilShaleEstonia.jpghttp://upload.wikimedia.org/wikipedia/en/5/59/GLMsed.jpg


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Clay stone de$osited in


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rganically formed# Consisting of acc"m"lated animals and plants

remains%

rganic sedimentary rocks contain materials generated *y liing

organisms+ and incl"de car*onate minerals created *y organisms+ s"ch as

corals+ moll"sks (Snail+ sl"g+ ctop"s + and foraminifera (sea,ater

rganism + ,hich coer the ocean floor ,ith layers of calci"m car*onate+

,hich can later form limestone% ther eamples incl"de stromatolites+ the

flint nod"les fo"nd in chalk (,hich is itself a *iochemical sedimentary

rock+ a form of limestone+ and coal and oil shale (deried from the

remains of tropical plants and s"*.ected to heat%

They are#

/% Calcareo"s rocks+ lime stone

2% Car*onaceo"s rocks+ coal



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Cheically fored7 this ty$e of roc"s is fored &y $reci$itation and

accuulation of solu&le constituents.

Cheical sedientary roc"s for when inerals in solution &ecoe

su$ersaturated and $reci$itate. An arine en(ironents this is a ethod for

the foration of liestone. ;nother coon en(ironent in which cheical

sedientary roc"s for is a &ody of water that is e(a$orating. E(a$oration

decreases the aount of water without decreasing the aount of dissol(ed

aterial. Therefore the dissol(ed aterial can &ecoe o(ersaturated and

$reci$itate. Sedientary roc"s fro this $rocess can include the e(a$orite

inerals halite *roc" salt+ syl(ite &arite and gy$su.

These are

1. Car&onate roc"s Liestone doloite

2. Sul$hate roc"s


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Consolidation is a process *y ,hich soft and loose sediments are

conerted into hard and firm rocks% Consolidation is of three types#

/% Compaction and $ehydration# The s0"ee1ing o"t of ,ater from the

pores of the sediments and its changing to solid mass *y cohesion

*et,een the particles and press"re from oerlying rock is called

compaction and dehydration%

2% Cementation# Many coarse grained sediments are consolidated *y

cementation+ ,hich is the process of precipitation of some cementing

materials+ for eample+ silica+ calci"m car*onate+ iron oides and clay

minerals%

% Crystalli1ation# Chemically formed sedimentary rocks s"ch as

limestone+ dolomites+ gyps"m etc are consolidated chiefly *y the

crystalli1ation of their constit"ents%

ConsolidationConsolidation


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Str"ct"ral feat"res of sedimentary rocks are of great al"e in

determining their origin% The main str"ct"res are as follo,s#

Stratification# The deposition of sediments into layer or *eds is called

stratification% The thickness of a single *ed may ary from a fe,

centimeters to many meters% The stratification is formed d"e to the

follo,ing%

!% $ifference in the kinds of materials deposited for eample shale and

lime stone

!!% $ifference in the si1e of particles deposited for eample coarse

grained and fine grained sandstone *eds!!!%$ifference in the color of the materials deposited for eample light

grey and dark grey layers of limestone

Str"ct"ral Feat"resStr"ct"ral Feat"res


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3amination# Thin *edding+ less than one centimeter in thickness+

are called lamination% !t is "s"ally fined grained sedimentary

rocks like shales%

Cross-*edding# !t is also called c"rrent *edding or false *edding%

Cross-*edding are the minor *edding or lamination ,hich lieat an angle to the planes of general stratification% This

str"ct"re is fo"nd in shallo, ,ater and ,ind formed deposits%

$iff f di k$iff t t f di t k


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Conglomerate# The pe**les and graels on consolidation and cementation

prod"ce a rock kno,n as conglomerate% Graels are deposited for the most

part *y ,ater% 4ater circ"lating thro"gh grael deposits may precipitate

o"t silica+ calci"m car*onate+ or iron oides+ ,hich act as cements *inding

the graels together into conglomerates%

Sandstones#Most sand is a ,ater deposit% !n arid regions+ ,idespread sands

hae *een laid do,n *y ,ind action% 5olcanic er"ptions+ glacial action+

mechanical and chemical ,eathering+ and organisms prod"ce sands% The

sand particles are deposited and then cemented together *y materials like

silica+ calcite+ iron oide or clay% Sandstones may *e siliceo"s sandstone that

is the cementing materials is silica6 it may *e calcario"s sandstone in ,hich

the cementing materials is calci"m car*onate6 ferr"gino"s sandstone and

argillaceo"s sandstone haing iron oide and clay as cementing materials

$ifferent types of sedimentary rocks$ifferent types of sedimentary rocks


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The thoro"ghly cemented sandstone ,ith 0"art1 are termed as

ortho0"art1ite%

Argillaceo"s rocks# ario"sly called m"dstone+ claystone+ and shale

(compacted or cemented are among the most a*"ndant of sedimentary

rocks% !t is a laminated fine grained sedimentary rock ,hich is mainly

composed of clay minerals and some silt-si1e grains of 0"art1%The claystones+ *eca"se they are characteristically soft and ,eak are not

s"ited to most constr"ction p"rposes% The compacted shale lose strength

,hen ,et and are s"*.ect to plastic deformation% 7nder load they are

s"*.ect to fail"re *y flo,% The cemented shales hae a strength compara*leto concrete *"t hae a relatiely high elasticity% Clay stones "nderlying the

sites of heay str"ct"res sho"ld *e test in *oth ,et and dry conditions% Clay

stone has a limited "se% !t seres as a ra, materials for the ceramic

ind"stry in some places and also "sed as ra, materials for cement



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Car*onate rocks# The car*onate rocks are chiefly the prod"cts of marine

or fresh ,ater sedimentation% They are predominantly chemical sediments

either formed *y meta*olic process of organism or precipitated

inorgainically% Mineralogically+ the car*onate rocks are comparatiely

simple% There are t,o main arieties6 the limestone composed chiefly of the

calcite+ and the dolomite composed chiefly of dolomite%

The car*onate rocks+ partic"larly the limestones+ hae a ery ,ide "se in

modern ind"stry% The largest single "se is as cr"shed stone% 3imestone is

one of the leading dimension stones *eing "tili1ed *oth for internal and

eternal ,ork% Commercial lime is deried from the *"rning of limestone%

http://upload.wikimedia.org/wikipedia/commons/7/7f/Quartzite.jpg


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Buart8ite a for of etaor$hic roc"

:etaor$hic !oc"s
http://upload.wikimedia.org/wikipedia/commons/7/7f/Quartzite.jpg


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Metamorphic rock is the res"lt of the transformation of an eisting rock

type+ the protolith+ in a process called metamorphism+ ,hich means 8change

in form8%

4hen the pre-eisting rocks (sedimentary or igneo"s rock are s"*.ected to

increased temperat"re+ press"re and action of chemically actie fl"ids+

metamorphic rocks are formed% $"ring metamorphism re-crystalli1ation of

mineral constit"ent takes place+ as a res"lt ne, minerals and ne, tet"re are

prod"ced%

The metamorphic processes generally improe the engineering *ehaior of

these rocks *y increasing their hardness and strength% 9eertheless+ some

metamorphic rocks still can *e pro*lematic% Some metamorphic rocks are

foliated+ ,hich means they hae oriented grains similar to *edding plains in

sedimentary rocks% These foliation is important *eca"se the shear strength is

less for stresses acting parallel to the foliation%

Metamorphic rocksMetamorphic rocks


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7n-,eathered non-foliated rocks generally proide ecellent s"pport for

engineering ,orks+ and are similar to intr"sie igneo"s rocks in their 0"ality%

:o,eer+ some foliated rocks are prone to slippage along the foliation planes%

Schist is the most nota*le in this regard *eca"se of its strong foliation ad the

presence of mica% The /;2< fail"re St%Fancis $am in California has *een

partially attri*"ted to shearing in schist and the /;=; fail"re of Malpasset

dam in France to shearing in a schistose gneiss%

Metamorphic rocksMetamorphic rocks

olded foliation in a etaor$hic roc"
http://upload.wikimedia.org/wikipedia/commons/6/6a/Migma_ss_2006.jpg


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Contact metamorphism is the name gien to the changes that take place

,hen magma is in.ected into the s"rro"nding solid rock% The changes that

occ"r are greatest ,hereer the magma comes into contact ,ith the rock

*eca"se the temperat"re are highest at this *o"ndary and decrease ,ith

distance from it% Aro"nd the igneo"s rock that forms from the cooling

magma is a metamorphosed 1one called a contact metamorphism a"reole%

Types of MetamorphismTypes of Metamorphism

; contact etaor$hic roc" ade of

inter layered calcite and ser$entine

fro the ,reca&rian of Canada

-shale ay &ecoe a dar" argillaceous hornfels

-Liestone ay change to a grey yellow or greenishlie-silicate-hornfels or siliceous ar&le

T f M t hiT pes of Metamorphism


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Regional metamorphism is the name gien to changes in great masses of

rock oer a ,ide area% Rock can *e metamorphosed simply *y *eing at

great depths *elo, the earth>s s"rface+ s"*.ected to high temperat"res

and the great press"re ca"sed *y the immense ,eight of the rock layers

a*oe% M"ch of the lo,er continental cr"st is metamorphic%

Types of MetamorphismTypes of Metamorphism

:ississi$$ian ar&le in ig Cottonwood


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Mar*le# Mar*les are metamorphosed car*onate rocks+ deried from

limestones and dolomites% The color of mar*le is aria*le+ ho,eer+ if the

rock is p"re calcite or dolomite mar*le it is generally ,hite% 5ario"s

imp"rities gie rise to ario"s shades% Green+ pinks and *"ffs are common

shades%

The principal "ses of mar*le are as c"t stone for *"ilding and ornamental or

decoratie "se%

$ifferent Metamorphic rocks$ifferent Metamorphic rocks


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Slate# Slate is a dense metamorphic rock+ ,ith a strongly deelopedfoliation% !t is prod"ced *y the metamorphism of shale% The rock

cleaage+ or split-a*ility is therefore ecellent and is the o"tstanding

characteristic of slates% The color of slate aries from iron-tinted reds

thro"gh ario"s shades of gray and green% The gray shades are d"e tocar*onaceo"s matter+ the greens to chloritic micas% The tet"re of

slates is ery fine or dense and foliation is good to perfect%

Slate is "sed ,idely in the electrical ind"stries as s,itch*oards%



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)hyllite# )hyllite are strongly foliated metamorphic rocks similar to the

slates *"t of slightly coarser tet"re% )hyllite hae shiny l"ster d"e the

presence of large amo"nt of fine flakes of mica% )hyllite grad"ally pass into

slates ,hich are the first stage in the metaphorphism of shale%

!t has little "se% !t is too soft for cr"shed stone+ and too ,eak for str"ct"ral

"ses%

Schist# Schist are foliated metamorphic rocks of medi"m to coarse tet"re%

They are the prod"ct of the same processes of rock flo, and recrystalli1ation

that prod"ce slates and phyllite% The color of schist ary according to the

mineralogical composition+ as does also the perfection of cleaage%

Schist has of little "se% ?eca"se of the foliation+ they are generally ,eak

rocks% Some schists especially rich in m"scoite are a so"rce of scrap mica%


geological cycle rock formation and types of rock-2 ( sedimentary &metamorphic rocks )

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