ch 21 intro to met.ppt

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Metamorphic Petrology

Fresh basalt

weathered basalt



The Limits of Metamorphism

• Low-temperature limit grades into diagenesis

• Diagenesis is a change in form that occurs in sedimentary

rocks. In geology, however, we restrict diagenetic

processes to those which occur at temperatures below

200o

C and pressures below about 300 MPa (MPa stands for Mega Pascals), this is equivalent to about 3,000

atmospheres of pressure.

Processes are indistinguishable

Metamorphism begins in the range of 100-150oC for the

more unstable types of protolith

Some zeolites are considered diagenetic and others

metamorphic – pretty arbitrary



• Metamorphism, therefore occurs at temperatures

and pressures higher than 200oC and 300

MPa. Rocks can be subjected to these higher

temperatures and pressures as they become

buried deeper in the Earth. Such burial usually

takes place as a result of tectonic processes such

as continental collisions or subduction.

• The upper limit of metamorphism occurs at the

pressure and temperature of wet partial meltingof the rock in question. Once melting begins,

the process changes to an igneous process rather

than a metamorphic process.



Metamorphic Agents and Changes

• Temperature: typically the

most important factor in

metamorphism

Figure 1-9. Estimated ranges of oceanic and

continental steady-state geotherms to a depth of

100 km using upper and lower limits based on heat

flows measured near the surface. After Sclater etal. (1980), Earth. Rev. Geophys. Space Sci., 18,

269-311.




Increasing temperature has several effects Promotes recrystallization increased grain size

Larger surface/volume ratio of a mineral lower

stability Increasing temperature eventually overcomes kinetic

barriers to recrystallization, and fine aggregates coalesce

to larger grains

• Especially for fine-grained and unstable materials in a

static environment (shear stresses often reduce grain size)



2) Drive reactions (endothermic)

Heating to conditions outside the stability

range of some mineral(s) may cause a reaction to take place that consumes the unstable

mineral(s) and produces new minerals that are

stable under the new conditions 3) Overcomes kinetic barriers

Disequilibrium is relatively common in sediments and

diagenesis

Mineral assemblages are usually simpler at higher

grades and the phase rule is applicable




• Pressure

“Normal” gradients may be perturbed in several

ways, typically:

High T/P geotherms in areas of plutonicactivity or rifting

Low T/P geotherms in subduction zones



Figure 21-1. Metamorphic field gradients (estimated P-T conditions along surface traverses directly up metamorphic grade) forseveral metamorphic areas. After Turner (1981). Metamorphic Petrology: Mineralogical, Field, and Tectonic Aspects. McGraw-

Hill.




• Metamorphic grade:

• As the temperature and/or pressure increases on a body

of rock we say that the rock undergoes progrademetamorphismor that the grade of metamorphism

increases. Metamorphic gradeis a general term for

describing the relative temperature and pressure

conditions under which metamorphic rocks form, such asthose depicted in metamorphic field gradients.



Four Divisions of Grade are recognized:

Very low gradeLow grade

Medium grade

High grade

The boundaries between the four divisions of grade are

marked by significant changes of mineral assemblages in

common rocks, corresponding with specific mineral reactions.



Examples of hydrous minerals that occur in low

grade metamorphic rocks:

Clay MineralsSerpentine

Chlorite

High-grade metamorphism takes place at

temperatures greater than 320oC and relatively high

pressure. As grade of metamorphism increases,

hydrous minerals become less hydrous, by losing

H2O and non-hydrous minerals become morecommon.

Examples of less hydrous minerals and non-hydrous

minerals that characterize high grade metamorphic

rocks:



Muscovite - hydrous mineral that eventually disappears at

the highest grade of metamorphism

Biotite - a hydrous mineral that is stable to very high

grades of metamorphism.

Pyroxene - a non hydrous mineral.

Garnet - a non hydrous mineral.

• Retrograde Metamorphism

• As temperature and pressure fall due to erosion

of overlying rock or due to tectonic uplift, one

might expect metamorphism to a follow a

reverse path and eventually return the rocks totheir original unmetamorphosed state. Such a

process is referred to as retrograde

metamorphism.



• If retrograde metamorphism were common, we

would not commonly see metamorphic rocks at

the surface of the Earth. Since we do see

metamorphic rocks exposed at the Earth's

surface retrograde metamorphism does not

appear to be common. The reasons for this

include:• chemical reactions take place more slowly as

temperature is decreased

• during prograde metamorphism, fluids such asH2O and CO2 are driven off, and these fluids are

necessary to form the hydrous minerals that are

stable at the Earth's surface.




• Stress • Strain deformation

• Deviatoric stress affects the textures and

structures, but not the equilibrium mineralassemblage

• Strain energy may overcome kinetic barriers to

reactions



• Metamorphic Agents and Changes

• Metamorphism occurs because some minerals are stableonly under certain conditions of pressure and

temperature. When pressure and temperature change,

chemical reactions occur to cause the minerals in the rock

to change to an assemblage that is stable at the new pressure and temperature conditions. But, the process is

complicated by such things as how the pressure is applied,

the time over which the rock is subjected to the higher

pressure and temperature, and whether or not there is afluid phase present during metamorphism.



• TemperatureTemperature increases with depth in the Earth along

the Geothermal Gradient. Thus higher temperature can

occur by burial of rock.

• Temperature can also increase due to igneous intrusion.

• Pressure increases with depth of burial, thus, both

pressure and temperature will vary with depth in the

Earth. Pressure is defined as a force acting equally

from all directions.

• Lithostatic pressure is uniform stress (hydrostatic)

• Deviatoric stress = unequal pressure in different

directions



• Resolved into three mutually perpendicular stress

(s) components:

s1 is the maximum principal stresss2 is an intermediate principal stress

s3 is the minimum principal stress

• In hydrostatic situations all three are equal



• If differential stress is present during

metamorphism, it can have a profound effect

on the texture of the rock.

• rounded grains can become flattened in the

direction of maximum stress.

• minerals that crystallize or grow in the

differential stress field can have a preferred

orientation. This is especially true of the sheet

silicate minerals (the micas: biotite and

muscovite, chlorite, talc, and serpentine).



• In Tension s1 is negative, and the resultant strain is

extension, or pulling apart.

• In Compression one stress direction(s1 ) is dominant,

which may cause folding or a more homogeneous deformation

called flattening. The general term for a planar texture or

structure is called Foliation. Lineation is the non-genetic term

that refers to such a parallel alignment of elongated features.

• Shear is an alternative response to compression in whichmotion occurs along a set of planes at an angle to s1 , like

pushing the top of a deck of cards.



• Foliation is a common result, which allows us to

estimate the orientation of s1

s

1

> s2

= s3

foliation and no lineation

s1 = s2 > s3 lineation and no foliation

s1 > s2 > s3 both foliation and lineation

Figure 21-3. Flattening of a ductile homogeneous sphere (a) containing randomly oriented flat disks or flakes. In (b), the matrix

flows with progressive flattening, and the flakes are rotated toward parallelism normal to the predominant stress. Winter

(2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

s1




Shear motion occurs along planes at an angle to s1

Figure 21-2. The three main types of deviatoric stress with an example of possible resulting structures. b. Shear, causing slip

along parallel planes and rotation. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

s1



• Fluid Phase - Any existing open space between

mineral grains in a rocks can potentially contain a

fluid. This fluid is mostly H2O, but contains dissolvedmineral matter. The fluid phase is important because

chemical reactions that involve one solid mineral

changing into another solid mineral can be greatly

speeded up by having dissolved ions transported by thefluid. Within increasing pressure of metamorphism,

the pore spaces in which the fluid resides is reduced,

and thus the fluid is driven off. Thus, no fluid will be

present when pressure and temperature decrease and, asdiscussed earlier, retrograde metamorphism will be

inhibited.




FluidsEvidence for the existence of a metamorphic fluid:

Fluid inclusions

Fluids are required for hydrous or carbonate phases

Volatile-involving reactions occur at

temperatures and pressures that require finitefluid pressures



• Time - The chemical reactions involved in

metamorphism, along with recrystallization, and

growth of new minerals are extremely slow

processes. Laboratory experiments suggest that

the longer the time available for metamorphism,

the larger are the sizes of the mineral grains produced. Thus, coarse grained metamorphic

rocks involve long times of

metamorphism. Experiments suggest that thetime involved is millions of years.




• Pfluid

is the sum of the partial pressures of

each component (Pfluid = pH2O + pCO2 + …)

• Mole fractions of the components, which

must sum to 1.0 (XH2O + XCO2 + … = 1.0) • Gradients in T, P, Xfluid

• Zonation in mineral assemblages



The Types of Metamorphism

Different approaches to classification

1. Based on principal process or agent

Dynamic Metamorphism

Thermal Metamorphism Dynamo-thermal Metamorphism



The Types of Metamorphism Different approaches to classification

2. Based on setting Contact Metamorphism

Pyrometamorphism

Regional Metamorphism Orogenic Metamorphism

Burial Metamorphism

Ocean Floor Metamorphism Hydrothermal Metamorphism

Fault-Zone Metamorphism

Impact or Shock Metamorphism



Contact Metamorphism

• Adjacent to igneous intrusions• Thermal (± metasomatic) effects of hot magma

intruding cooler shallow rocks

• Occurs over a wide range of pressures, including

very low

• Contact aureole





The size and shape of an aureole is controlled by:

The nature of the pluton

The nature of the country rocks

Size

Shape

Orientation

Temperature

Composition

Composition Depth and metamorphic grade prior to intrusion

Permeability





Most easily recognized where a pluton is introduced into

shallow rocks in a static environment

Hornfelses (granofelses) commonly with relict

textures and structures





Polymetamorphic rocks are common, usually

representing an orogenic event followed by a

contact one

• Spotted phyllite (or slate)

• Overprint may be due to:

Lag time for magma migration

A separate phase of post-orogenic collapse

magmatism




Pyrometamorphism

Very high temperatures at very low pressures,

generated by a volcanic or subvolcanic body

Also developed in xenoliths




Regional Metamorphism sensu lato: metamorphism

that affects a large body of rock, and thus covers agreat lateral extent

Three principal types:

Orogenic metamorphism

Burial metamorphism

Ocean-floor metamorphism




Orogenic Metamorphism is the type of metamorphism

associated with convergent plate margins

• Dynamo-thermal: one or more episodes of

orogeny with combined elevated geothermal

gradients and deformation (deviatoric stress)• Foliated rocks are a characteristic product




Orogenic

Metamorphism

Figure 21-6. Schematic model for

the sequential (a c) development

of a “Cordilleran-type” or active

continental margin orogen. The

dashed and black layers on the

right represent the basaltic and

gabbroic layers of the oceanic

crust. From Dewey and Bird (1970)

J . Geophys. Res., 75, 2625-2647;

and Miyashiro et al. (1979)

Orogeny. John Wiley & Sons.




Orogenic Metamorphism




Orogenic Metamorphism

• Polymetamorphic patterns

• Continental collision

• Batholiths are usually present in the highest grade areas

• If plentiful and closely spaced, may be called regional

contact metamorphism




Burial metamorphism

• Southland Syncline in New Zealand: thick pile (> 10 km)

of Mesozoic volcaniclastics

• Mild deformation, no igneous intrusions discovered

• Fine-grained, high-temperature phases, glassy ash: very

susceptible to metamorphic alteration

• Metamorphic effects attributed to increased temperatureand pressure due to burial

• Diagenesis to the formation of zeolites, prehnite,

pumpellyite, laumontite, etc.




Hydrothermal metamorphism • Hot H2O-rich fluids

• Usually involves metasomatism

• Difficult type to constrain: hydrothermal effectsoften play some role in most of the other types of

metamorphism




Burial metamorphism occurs in areas that have not

experienced significant deformation or orogeny

• Restricted to large, relatively undisturbed

sedimentary piles away from active plate margins

The Gulf of Mexico?

Bengal Fan?




Ocean-Floor Metamorphism affects the oceanic

crust at ocean ridge spreading centers

• Considerable metasomatic alteration, notably loss

of Ca and Si and gain of Mg and Na

• Highly altered chlorite-quartz rocks- distinctive

high-Mg, low-Ca composition

• Exchange between basalt and hot seawater • Another example of hydrothermal metamorphism




Impact metamorphism at meteorite (or other

bolide) impact craters

Both correlate with dynamic metamorphism,

based on process

Fault-Zone and Impact Metamorphism

High rates of deformation and strain with only

minor recrystallization

• If the strain is high enough and the temperature



If the strain is high enough, and the temperature

low enough, minerals may be broken, bent or

crushed without much accompanying

recrystallization. This processes is known as“Cataclasis” , and occurs at impacts and in the

very shallow portions of the fault zones where

rocks behave in a very brittle fashion.

• Common products in shallow fault zones are

“Fault Breccia (a broken and crushed filling infault zones)” and “Fault Gouge (a clayey alteration

of breccia resulting from interaction with

groundwater that permeates down along the

”



• With increased depth, faults gradually change

from brittle fractures to wider shear zones

involving a combination of catalysis and

recrystallization. Intense localized shear

produces a fine-grained foliated flint-like rock

called “Mylonite”.

• At deeper level yet, shear movement is

distributed more evenly throughout the zone,and the rocks are almost entirely ductile.

( ) Sh ll f l



(a) Shallow fault

zone with fault

breccia

(b) Slightly deeper

fault zone (exposed

by erosion) with

some ductile flowand fault mylonite

Figure 21-7. Schematic cross

section across fault zones. After

Mason (1978) Petrology of theMetamorphic Rocks. George Allen

& Unwin. London.



Prograde Metamorphism

• Prograde: increase in metamorphic grade with time

as a rock is subjected to gradually more severe

conditions

Prograde metamorphism: changes in a rock that

accompany increasing metamorphic grade

• Retrograde: decreasing grade as rock cools and

recovers from a metamorphic or igneous event

Retrograde metamorphism: any accompanyingchanges



The Progressive Nature of Metamorphism

• A rock at a high metamorphic grade probably progressed through a sequence of mineral

assemblages rather than hopping directly from an

unmetamorphosed rock to the metamorphic rock that we find today



The Progressive Nature of Metamorphism

Retrograde metamorphism typically of minor

significance

• Prograde reactions are endothermic and easily

driven by increasing T

• Devolatilization reactions are easier than

reintroducing the volatiles

• Geothermometry indicates that the mineral

compositions commonly preserve the maximum

temperature



Types of Protolith

Lump the common types of sedimentary and igneous

rocks into six chemically based-groups

1. Ultramafic - very high Mg, Fe, Ni, Cr

2. Mafic - high Fe, Mg, and Ca

3. Shales (pelitic) - high Al, K, Si

4. Carbonates- high Ca, Mg, CO2

5. Quartz - nearly pure SiO2.6. Quartzo-feldspathic - high Si, Na, K, Al



Why Study Metamorphism?

• Interpretation of the conditions and evolution of

metamorphic bodies, mountain belts, and ultimately the

state and evolution of the Earth's crust

• Metamorphic rocks may retain enough inherited

information from their protolith to allow us to interpretmuch of the pre-metamorphic history as well

Orogenic Regional Metamorphism of




the Scottish Highlands

• George Barrow (1893, 1912)

• SE Highlands of Scotland - Caledonian Orogeny

~ 500 Ma

• Nappes

• Granites



Barrow’s

Area

Figure 21-8. Regional metamorphic

map of the Scottish Highlands,

showing the zones of minerals that

develop with increasing

metamorphic grade. From Gillen

(1982) Metamorphic Geology. AnIntroduction to Tectonic andMetamorphic Processes. George

Allen & Unwin. London.





the Scottish Highlands

• Barrow studied the pelitic rocks

• Could subdivide the area into a series of

metamorphic zones, each based on the appearance

of a new mineral as metamorphic grade increased

The sequence of zones now recognized and the typical



The sequence of zones now recognized, and the typical

metamorphic mineral assemblage in each, are:

Chlorite zone. Pelitic rocks are slates or phyllites and typically

contain chlorite, muscovite, quartz and albite

Biotite zone. Slates give way to phyllites and schists, with biotite,

chlorite, muscovite, quartz, and albite

Garnet zone. Schists with conspicuous red almandine garnet,

usually with biotite, chlorite, muscovite, quartz, and albite or oligoclase

Staurolite zone. Schists with staurolite, biotite, muscovite, quartz,

garnet, and plagioclase. Some chlorite may persist

Kyanite zone. Schists with kyanite, biotite, muscovite, quartz,

plagioclase, and usually garnet and staurolite

Sillimanite zone. Schists and gneisses with sillimanite, biotite,

muscovite, quartz, plagioclase, garnet, and perhaps staurolite.

Some kyanite may also be present (although kyanite and

sillimanite are both polymorphs of Al2SiO5)

• Sequence = “Barrovian zones”



• Sequence = Barrovian zones

• The P-T conditions referred to as “Barrovian-type”

metamorphism (fairly typical of many belts)

• Now extended to a much larger area of the Highlands

• Isograd = line that separates the zones (a line in the field

of constant metamorphic grade)



Figure 21-8. Regional

metamorphic map of the

Scottish Highlands, showing

the zones of minerals that

develop with increasingmetamorphic grade. From

Gillen (1982) MetamorphicGeology. An Introduction to

Tectonic and MetamorphicProcesses. George Allen &

Unwin. London.

To summarize:



To summarize:

• An isograd represents the first appearance of a particular

metamorphic index mineral in the field as one progressesup metamorphic grade

• When one crosses an isograd, such as the biotite isograd,

one enters the biotite zone

• Zones thus have the same name as the isograd that forms

the low-grade boundary of that zone

• Because classic isograds are based on the first appearanceof a mineral, and not its disappearance, an index mineral

may still be stable in higher grade zones

A variation occurs in the area just to the north of



A variation occurs in the area just to the north of

Barrow’s, in the Banff and Buchan district

• Pelitic compositions are similar, but the sequenceof isograds is:

chlorite

biotite cordierite

andalusite

sillimanite

The stability field of andalusite occurs at pressures less than



0.37 GPa (~ 10 km), while kyanite sillimanite at the

sillimanite isograd only above this pressure

Figure 21-9. The P-T phase diagram for the system Al2SiO5 showing the stability fields for the three polymorphs andalusite, kyanite, and

sillimanite. Also shown is the hydration of Al2SiO5 to pyrophyllite, which limits the occurrence of an Al2SiO5 polymorph at low grades inthe presence of excess silica and water. The diagram was calculated using the program TWQ (Berman, 1988, 1990, 1991).

Regional Burial Metamorphism




Otago, New Zealand

• Jurassic graywackes, tuffs, and volcanics in a deeptrough metamorphosed in the Cretaceous

• Fine grain size and immature material is highly

susceptible to alteration (even at low grades)




g p

Otago, New Zealand Section X-Y shows more detail

Figure 21-10. Geologic sketch map of the South Island of

New Zealand showing the Mesozoic metamorphic rocks east

of the older Tasman Belt and the Alpine Fault. The Torlese

Group is metamorphosed predominantly in the prehnite-

pumpellyite zone, and the Otago Schist in higher grade

zones. X-Y is the Haast River Section of Figure 21-11. From

Turner (1981) Metamorphic Petrology: Mineralogical, Field,and Tectonic Aspects. McGraw-Hill.





Otago, New Zealand

Isograds mapped at the lower grades:1) Zeolite

2) Prehnite-Pumpellyite

3) Pumpellyite (-actinolite)4) Chlorite (-clinozoisite)

5) Biotite

6) Almandine (garnet)7) Oligoclase (albite at lower grades is replaced by a

more calcic plagioclase)




Regional Burial Metamorphism Figure 21-11. Metamorphic zones of the Haast

Group (along section X-Y in Figure 21-10).

After Cooper and Lovering (1970) Contrib.

Mineral. Petrol., 27, 11-24.

Paired Metamorphic Belts of Japan




Figure 21-12. The Sanbagawa and Ryoke

metamorphic belts of Japan. From Turner

(1981) Metamorphic Petrology:Mineralogical, F ield, and Tectonic Aspects.McGraw-Hill and Miyashiro (1994)

Metamorphic Petrology. Oxford University

Press.

P i d M t hi B lt f J



Figure 21-13. Some of the

paired metamorphic belts

in the circum-Pacific

region. From Miyashiro

(1994) MetamorphicPetrology. Oxford

University Press.

Contact Metamorphism of Pelitic Rocks




in the Skiddaw Aureole, UK

• Ordovician Skiddaw Slates (English Lake District)

intruded by several granitic bodies

• Intrusions are shallow

• Contact effects overprinted on an earlier low-grade

regional orogenic metamorphism






• The aureole around the Skiddaw granite was sub-

divided into three zones, principally on the basis of

textures:

Unaltered slates

Outer zone of spotted slates

Middle zone of andalusite slates

Inner zone of hornfels

Skiddaw granite

Increasing

Metamorphic

Grade

Contact



Figure 21-14. Geologic

Map and cross-section of

the area around theSkiddaw granite, Lake

District, UK. After

Eastwood et al (1968).

Geology of the Countryaround Cockermouth andCaldbeck. Explanation

accompanying the 1-inch

Geological Sheet 23, New

Series. Institute of

Geological Sciences.

London.






• Middle zone: slates more thoroughly recrystallized, contain biotite + muscovite + cordierite + andalusite + quartz

Figure 21-15. Cordierite-

andalusite slate from the

middle zone of the

Skiddaw aureole. From

Mason (1978) Petrology of the Metamorphic Rocks.

George Allen & Unwin.

London. 1 mm






Inner zone:

Thoroughly recrystallized

Lose foliation

Figure 21-16. Andalusite-cordierite

schist from the inner zone of the

Skiddaw aureole. Note the chiastolitecross in andalusite (see also Figure 22-

49). From Mason (1978) Petrology of the Metamorphic Rocks. George Allen

& Unwin. London.

1 mm






• The zones determined on a textural basis

• Prefer to use the sequential appearance of

minerals and isograds to define zones

• But low-P isograds converge in P-T

• Skiddaw sequence of mineral development with

grade is difficult to determine accurately

Contact Metamorphism and Skarn




Formation at Crestmore, CA, USA

• Crestmore quarry in the Los Angeles basin

• Quartz monzonite porphry intrudes Mg-bearing

carbonates (either late Paleozoic or Triassic)

• Brunham (1959) mapped the following zones and the

mineral assemblages in each (listed in order of increasing

grade):

Forsterite Zone:



Forsterite Zone:

calcite + brucite + clinohumite + spinel

calcite + clinohumite + forsterite + spinel

calcite + forsterite + spinel + clintonite

Monticellite Zone:

calcite + forsterite + monticellite + clintonite

calcite + monticellite + melilite + clintonite

calcite + monticellite + spurrite (or tilleyite) + clintonite

monticellite + spurrite + merwinite + melilite

Vesuvianite Zone:

vesuvianite + monticellite + spurrite + merwinite +melilite

vesuvianite + monticellite + diopside + wollastonite

Garnet Zone:

grossular + diopside + wollastonite






An idealized cross-section through the aureole

Figure 21-17.

Idealized N-S cross

section (not to scale)

through the quartz

monzonite and the

aureole atCrestmore, CA.

From Burnham

(1959) Geol. Soc.Amer. Bull., 70, 879-

920.






1. The mineral associations in successive zones (in allmetamorphic terranes) vary by the formation of new

minerals as grade increases

This can only occur by a chemical reaction in which some

minerals are consumed and others produced






a) Calcite + brucite + clinohumite + spinel zone to theCalcite + clinohumite + forsterite + spinel sub-zone

involves the reaction:

2 Clinohumite + SiO2 9 Forsterite + 2 H2O

b) Formation of the vesuvianite zone involves the reaction:

Monticellite + 2 Spurrite + 3 Merwinite + 4 Melilite

+ 15 SiO2 + 12 H2O 6 Vesuvianite + 2 CO2




Co c e o p s d S


2) Find a way to display data in simple, yet useful ways

• If we think of the aureole as a chemical system, we note

that most of the minerals consist of the components

CaO-MgO-SiO2-CO2-H2O (with minor Al2O3)

Figure 21-17. CaO-MgO-SiO2 diagram at a fixed

pressure and temperature showing the

compositional relationships among the minerals



Zones are numbered

(from outside inward)

compositional relationships among the minerals

and zones at Crestmore. Numbers correspond to

zones listed in the text. After Burnham (1959) Geol.Soc. Amer. Bull., 70, 879-920; and Best (1982)

Igneous and Metamorphic Petrology. W. H.

Freeman.

Figures not used



g

Figure 21-4. A situation in which

lithostatic pressure (Plith) exerted by the

mineral grains is greater than the

intergranular fluid pressure (Pfluid). At a

depth around 10 km (or T around 300oC)

minerals begin to yield or dissolve at the

contact points and shift toward orprecipitate in the fluid-filled areas,

allowing the rock to compress. The

decreased volume of the pore spaces will

raise Pfluid until it equals Plith. Winter

(2001) An Introduction to Igneous and

Metamorphic Petrology. Prentice Hall.

Figures not used



g

ch 21 intro to met.ppt

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