Silicate Polymerization In

Igneous Processes

By Ahmed Tarek Mohamed Mahmoud

gmailcom887275ahmedtarek mail-E

Geology department

Under supervision

prof Amal Abd El-Maboud

Professor of physical chemistry of macromolecules

Introduction

Magma is very hot liquid of molten rocks (often mantle derived melt) and contain other constituents like gases volatiles and solid suspended crystals where magma exist into deep plutinic huge chambers

While Lava is a magma but extruded onto the earth by (volcanic eruption) or from (earth fissure)

Magma composition

Magma essentially composed of eight major elements (Fe Mg Ca Al Si O2 Na K) minor elements (Ti Mn P and others) and other traces

These elements ordered in many crystalline structures to form minerals during solidification of the magmatic melt by decreasing of itrsquos temperature

Silica is the most abundant molecule and affects the properties of magma and play important role in formation of these minerals where most of them are silicate minerals

Physical properties of magma

1 Temperature

2 Density

3 Viscosity

4 Gas solubility

These essential properties

control magma behavior and

mainly affected by siliceous

content in the melt

Highly Viscous Lava

Structure of silicates in the melt Silicate structure composed of many silica units SiO4

In structural terms the SiO4 tetrahedron is the basic building brick

from which all silicate crystals and melts are constructed

Each unit charged with 4 negative charges due to the silicon atom

itself can satisfy only half of the bonding capacity of its four

oxygen neighbors (four bonds out of a total of eight)

The remnant 4 negative charges neutralized during crystallization

of silicate minerals by ionic bonding with any other

electropositive element like (Mg Fe Ca) which coexist into the

melt with oxygen in silicate structure

Silicate melt polymerization

When there are no more electropositive cations or by decreasing

temperature of the melt where the melt continuously raised from

the plutonic chamber to the surface due to difference in densities

between melt and surrounded dense solid rocks

So the continuous decreasing in temperature is conjugated by

increasing in degree of silica polymerization and complexity

This can lead to every oxygen atom being shared between

neighboring tetrahedra and extending of the SindashO bonding

Whereas familiar organic polymers consist of chains and rings of

carbon atoms linked directly to each other (ndashCndashCndashC) the linkage

in silicate polymers is always through oxygen atoms (ndashSindashOndashSindash

OndashSindash)

Silicate melt polymerization Polymerisation is a process by which molecules increase in

size by the repeated addition of smaller molecules Silicate

magmas are polymerized liquids consisting of a network of

SiO4 tetrahedra units linked by sharing oxygen atoms with

neighboring tetrahedra

Silica is capable of polymerisation since the covalent bonds

between Si and O within the molecule leave bonding

electrons available on each oxygen atom Oxygen can

therefore covalently bond with two Si atoms linking

together tetrahedra

Dimer silicates

Silicate melt polymerization

The most complex

Poly

mer

izati

on

in

crea

sed

(a) Single chain

(b) Double chain

(c) Sheet silicates

Polymerization affected by water

content into magma Water decreases polymerisation by reacting with bridging

oxygen to form non-bridging oxygen and hydroxyl

molecules The solubility of water in silica-rich magmas is

therefore much higher than silica-poor due to high degree

of polymerisation Water decreases the viscosity of magmas

by decreasing the degree of polymerisation

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Magma composition

Magma essentially composed of eight major elements (Fe Mg Ca Al Si O2 Na K) minor elements (Ti Mn P and others) and other traces

These elements ordered in many crystalline structures to form minerals during solidification of the magmatic melt by decreasing of itrsquos temperature

Silica is the most abundant molecule and affects the properties of magma and play important role in formation of these minerals where most of them are silicate minerals

Physical properties of magma

1 Temperature

2 Density

3 Viscosity

4 Gas solubility

These essential properties

control magma behavior and

mainly affected by siliceous

content in the melt

Highly Viscous Lava

Structure of silicates in the melt Silicate structure composed of many silica units SiO4

In structural terms the SiO4 tetrahedron is the basic building brick

from which all silicate crystals and melts are constructed

Each unit charged with 4 negative charges due to the silicon atom

itself can satisfy only half of the bonding capacity of its four

oxygen neighbors (four bonds out of a total of eight)

The remnant 4 negative charges neutralized during crystallization

of silicate minerals by ionic bonding with any other

electropositive element like (Mg Fe Ca) which coexist into the

melt with oxygen in silicate structure

Silicate melt polymerization

When there are no more electropositive cations or by decreasing

temperature of the melt where the melt continuously raised from

the plutonic chamber to the surface due to difference in densities

between melt and surrounded dense solid rocks

So the continuous decreasing in temperature is conjugated by

increasing in degree of silica polymerization and complexity

This can lead to every oxygen atom being shared between

neighboring tetrahedra and extending of the SindashO bonding

Whereas familiar organic polymers consist of chains and rings of

carbon atoms linked directly to each other (ndashCndashCndashC) the linkage

in silicate polymers is always through oxygen atoms (ndashSindashOndashSindash

OndashSindash)

Silicate melt polymerization Polymerisation is a process by which molecules increase in

size by the repeated addition of smaller molecules Silicate

magmas are polymerized liquids consisting of a network of

SiO4 tetrahedra units linked by sharing oxygen atoms with

neighboring tetrahedra

Silica is capable of polymerisation since the covalent bonds

between Si and O within the molecule leave bonding

electrons available on each oxygen atom Oxygen can

therefore covalently bond with two Si atoms linking

together tetrahedra

Dimer silicates

Silicate melt polymerization

The most complex

Poly

mer

izati

on

in

crea

sed

(a) Single chain

(b) Double chain

(c) Sheet silicates

Polymerization affected by water

content into magma Water decreases polymerisation by reacting with bridging

oxygen to form non-bridging oxygen and hydroxyl

molecules The solubility of water in silica-rich magmas is

therefore much higher than silica-poor due to high degree

of polymerisation Water decreases the viscosity of magmas

by decreasing the degree of polymerisation

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Physical properties of magma

1 Temperature

2 Density

3 Viscosity

4 Gas solubility

These essential properties

control magma behavior and

mainly affected by siliceous

content in the melt

Highly Viscous Lava

Structure of silicates in the melt Silicate structure composed of many silica units SiO4

In structural terms the SiO4 tetrahedron is the basic building brick

from which all silicate crystals and melts are constructed

Each unit charged with 4 negative charges due to the silicon atom

itself can satisfy only half of the bonding capacity of its four

oxygen neighbors (four bonds out of a total of eight)

The remnant 4 negative charges neutralized during crystallization

of silicate minerals by ionic bonding with any other

electropositive element like (Mg Fe Ca) which coexist into the

melt with oxygen in silicate structure

Silicate melt polymerization

When there are no more electropositive cations or by decreasing

temperature of the melt where the melt continuously raised from

the plutonic chamber to the surface due to difference in densities

between melt and surrounded dense solid rocks

So the continuous decreasing in temperature is conjugated by

increasing in degree of silica polymerization and complexity

This can lead to every oxygen atom being shared between

neighboring tetrahedra and extending of the SindashO bonding

Whereas familiar organic polymers consist of chains and rings of

carbon atoms linked directly to each other (ndashCndashCndashC) the linkage

in silicate polymers is always through oxygen atoms (ndashSindashOndashSindash

OndashSindash)

Silicate melt polymerization Polymerisation is a process by which molecules increase in

size by the repeated addition of smaller molecules Silicate

magmas are polymerized liquids consisting of a network of

SiO4 tetrahedra units linked by sharing oxygen atoms with

neighboring tetrahedra

Silica is capable of polymerisation since the covalent bonds

between Si and O within the molecule leave bonding

electrons available on each oxygen atom Oxygen can

therefore covalently bond with two Si atoms linking

together tetrahedra

Dimer silicates

Silicate melt polymerization

The most complex

Poly

mer

izati

on

in

crea

sed

(a) Single chain

(b) Double chain

(c) Sheet silicates

Polymerization affected by water

content into magma Water decreases polymerisation by reacting with bridging

oxygen to form non-bridging oxygen and hydroxyl

molecules The solubility of water in silica-rich magmas is

therefore much higher than silica-poor due to high degree

of polymerisation Water decreases the viscosity of magmas

by decreasing the degree of polymerisation

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Structure of silicates in the melt Silicate structure composed of many silica units SiO4

In structural terms the SiO4 tetrahedron is the basic building brick

from which all silicate crystals and melts are constructed

Each unit charged with 4 negative charges due to the silicon atom

itself can satisfy only half of the bonding capacity of its four

oxygen neighbors (four bonds out of a total of eight)

The remnant 4 negative charges neutralized during crystallization

of silicate minerals by ionic bonding with any other

electropositive element like (Mg Fe Ca) which coexist into the

melt with oxygen in silicate structure

Silicate melt polymerization

When there are no more electropositive cations or by decreasing

temperature of the melt where the melt continuously raised from

the plutonic chamber to the surface due to difference in densities

between melt and surrounded dense solid rocks

So the continuous decreasing in temperature is conjugated by

increasing in degree of silica polymerization and complexity

This can lead to every oxygen atom being shared between

neighboring tetrahedra and extending of the SindashO bonding

Whereas familiar organic polymers consist of chains and rings of

carbon atoms linked directly to each other (ndashCndashCndashC) the linkage

in silicate polymers is always through oxygen atoms (ndashSindashOndashSindash

OndashSindash)

Silicate melt polymerization Polymerisation is a process by which molecules increase in

size by the repeated addition of smaller molecules Silicate

magmas are polymerized liquids consisting of a network of

SiO4 tetrahedra units linked by sharing oxygen atoms with

neighboring tetrahedra

Silica is capable of polymerisation since the covalent bonds

between Si and O within the molecule leave bonding

electrons available on each oxygen atom Oxygen can

therefore covalently bond with two Si atoms linking

together tetrahedra

Dimer silicates

Silicate melt polymerization

The most complex

Poly

mer

izati

on

in

crea

sed

(a) Single chain

(b) Double chain

(c) Sheet silicates

Polymerization affected by water

content into magma Water decreases polymerisation by reacting with bridging

oxygen to form non-bridging oxygen and hydroxyl

molecules The solubility of water in silica-rich magmas is

therefore much higher than silica-poor due to high degree

of polymerisation Water decreases the viscosity of magmas

by decreasing the degree of polymerisation

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Silicate melt polymerization

When there are no more electropositive cations or by decreasing

temperature of the melt where the melt continuously raised from

the plutonic chamber to the surface due to difference in densities

between melt and surrounded dense solid rocks

So the continuous decreasing in temperature is conjugated by

increasing in degree of silica polymerization and complexity

This can lead to every oxygen atom being shared between

neighboring tetrahedra and extending of the SindashO bonding

Whereas familiar organic polymers consist of chains and rings of

carbon atoms linked directly to each other (ndashCndashCndashC) the linkage

in silicate polymers is always through oxygen atoms (ndashSindashOndashSindash

OndashSindash)

Silicate melt polymerization Polymerisation is a process by which molecules increase in

size by the repeated addition of smaller molecules Silicate

magmas are polymerized liquids consisting of a network of

SiO4 tetrahedra units linked by sharing oxygen atoms with

neighboring tetrahedra

Silica is capable of polymerisation since the covalent bonds

between Si and O within the molecule leave bonding

electrons available on each oxygen atom Oxygen can

therefore covalently bond with two Si atoms linking

together tetrahedra

Dimer silicates

Silicate melt polymerization

The most complex

Poly

mer

izati

on

in

crea

sed

(a) Single chain

(b) Double chain

(c) Sheet silicates

Polymerization affected by water

content into magma Water decreases polymerisation by reacting with bridging

oxygen to form non-bridging oxygen and hydroxyl

molecules The solubility of water in silica-rich magmas is

therefore much higher than silica-poor due to high degree

of polymerisation Water decreases the viscosity of magmas

by decreasing the degree of polymerisation

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Silicate melt polymerization Polymerisation is a process by which molecules increase in

size by the repeated addition of smaller molecules Silicate

magmas are polymerized liquids consisting of a network of

SiO4 tetrahedra units linked by sharing oxygen atoms with

neighboring tetrahedra

Silica is capable of polymerisation since the covalent bonds

between Si and O within the molecule leave bonding

electrons available on each oxygen atom Oxygen can

therefore covalently bond with two Si atoms linking

together tetrahedra

Dimer silicates

Silicate melt polymerization

The most complex

Poly

mer

izati

on

in

crea

sed

(a) Single chain

(b) Double chain

(c) Sheet silicates

Polymerization affected by water

content into magma Water decreases polymerisation by reacting with bridging

oxygen to form non-bridging oxygen and hydroxyl

molecules The solubility of water in silica-rich magmas is

therefore much higher than silica-poor due to high degree

of polymerisation Water decreases the viscosity of magmas

by decreasing the degree of polymerisation

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Silicate melt polymerization

The most complex

Poly

mer

izati

on

in

crea

sed

(a) Single chain

(b) Double chain

(c) Sheet silicates

Polymerization affected by water

content into magma Water decreases polymerisation by reacting with bridging

oxygen to form non-bridging oxygen and hydroxyl

molecules The solubility of water in silica-rich magmas is

therefore much higher than silica-poor due to high degree

of polymerisation Water decreases the viscosity of magmas

by decreasing the degree of polymerisation

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Poly

mer

izati

on

in

crea

sed

(a) Single chain

(b) Double chain

(c) Sheet silicates

Polymerization affected by water

content into magma Water decreases polymerisation by reacting with bridging

oxygen to form non-bridging oxygen and hydroxyl

molecules The solubility of water in silica-rich magmas is

therefore much higher than silica-poor due to high degree

of polymerisation Water decreases the viscosity of magmas

by decreasing the degree of polymerisation

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Polymerization affected by water

content into magma Water decreases polymerisation by reacting with bridging

oxygen to form non-bridging oxygen and hydroxyl

molecules The solubility of water in silica-rich magmas is

therefore much higher than silica-poor due to high degree

of polymerisation Water decreases the viscosity of magmas

by decreasing the degree of polymerisation

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Polymerization and magma behavior

1 Polymerization and Eruption Temperature

Polymerized magma which had high silica content is cooler

(lt 800degC) than unpolymerized magma which had low silica

content (~1200degC) where polymerization process occurs at

low temperature

2 Viscosity of the melt

Unpolymerized very hot magma flows fairly rapidly and

has low viscosity (10^2-10^4 poises) on the contrary cold

polymerized silicic magma has much higher viscosity

(10^5-10^15 poises) and has high resistance to flow

(sticky)

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Polymerization and magma behavior

3 Volatile content in the melts

Volatiles are elements that dissolve in magmas but transform to

gas or released and exsolved as magma reaches the surface this

can be catastrophic way to form an explosive eruption

Examples of important volatiles are H2O CO2 F Cl S (as H₂S

or SO2) Viscous polymerized magma has high volatile content

but very hot dry magma hasnrsquot any volatiles

4 Density of the melt

As silicic magma evolve itrsquos density will normally decreased due

to increasing of silica content and settling of all heavy minerals

which concentrated in the early stages of crystallization into

rocks which formed at high temperatures so in case of silicic

magma by decreasing itrsquos density it will be more polymerized

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Running less viscous lava

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

highly viscous lava flow

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Explosive eruption (gases amp dust released)

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

For further reading

This reference is recommended

Chemical Fundamentals of Geology and

Environmental Geoscience by [Robin

Gill 2015] 3rd edition

Reference downloading link

ha9ll3si6httpwwwmediafirecomdownload

Chemical+Fundamentals+of+Geology+62chp2

BRobin5and+Environmental+Geoscience++

-Geo+Pedia+Geo28D+52015C+2+Gill+

pdf29Library

Thank you

amp

Best regards