Mysen Progress in Earth and Planetary Science 2014, 1:4
http://www.progearthplanetsci.com/content/1/1/4

REVIEW

Open Access

Water-melt interaction in hydrous magmatic
systems at high temperature and pressure
Bjorn Mysen
Abstract
Experimental data on the structure and properties of melts and fluids relevant to water-melt interaction in hydrous
magmatic systems in the Earth's interior have been reviewed. Complex relationships between water solubility inmelts and their bulk composition [Al/Si-ratio, metal oxide/(Al + Si) and electron properties of metal cations] explain
why water solubility in felsic magmas such as those of rhyolite and andesite composition is significantly greaterthan the water solubility in basalt melts. The silicate solubility in aqueous fluid is also significantly dependent oncomposition with metal oxide/(Al + Si) and electron properties of the metal cations, the dominant variables.
Hydrogen bonding is not important in hydrous fluids and melts at temperatures above 500°C to 550°C and does
not, therefore, play a role in hydrous magmatic systems. The properties of hydrous melts and aqueous solutions aregoverned by how the silicate speciation (Qn species, where n is the number of bridging oxygen in an individual
species) varies with bulk composition, silicate composition, temperature, and pressure. The reactions that describe
the interactions are similar in melts, fluids, and supercritical fluids. The degree of melt polymerization caused bydissolved water varies with melt composition and total water content. Silicate- and alkali-rich felsic magmatic melts
are more sensitive to water content than more mafic magmas. Transport and configurational properties of hydrous
magmatic melts can be modeled with the aid of the Qn speciation variations. Liquidus and melting phase relationsof hydrous systems also can be described in such terms, as can minor and trace element partition coefficients.
Stable isotope fractionation (e.g., D/H) can also be rationalized in this manner. Critical to these latter observations is
the high silicate concentration in aqueous fluids. These components can enhance solubility of minor and traceelements by orders of magnitude and change the speciation of H and D complexes so that their fractionation
factors change quite significantly. Data from pure silicate-H2O systems cannot be employed for these purposes.
Keywords: Hydrous magma; Aqueous fluid; Melt structure; Viscosity; Isotope partitioning; Partial melting; Water
solubility; Silicate solubility; Glass transition; Solution mechanism

Review
Introduction

The principal mass and energy transport agents in the
Earth are magmatic melts and water-rich fluids. Theirtransport properties are sensitive to their water and silicate
content. Experimental characterization of solubility andsolution mechanisms of water and silicate components is,therefore, central to our understanding of magmatic andmetasomatic processes in the Earth’s interior.
Properties of magmatic melts are sensitive to their watercontent as first noted by Spallanzani (1798). Perhaps themost well-known among these effects is a several hundred
Correspondence: bmysen@ciw.edu
Geophysical Laboratory, Carnegie Institution of Washington, 5151 Broad
Branch Rd., NW, Washington DC 20015, USA

degree centigrade temperature depression at high pressureof solidii and liquidii of silicate phase assemblages (including natural mineral assemblages) (e.g., Kushiro et al.
1968a, b; Grove et al. 2012). Liquidus phase relations (including partial melt compositions), transport, and volume
properties of hydrous melts also vary in important ways
with variations in water content (Kushiro 1972; Richet
et al. 1996; Ochs and Lange 1999; Grove et al. 2003).
Aqueous solutions in the Earth's interior are efficientsolvents of oxide components (Zhang and Frantz 2000;
Manning 2004). Several mol% of silicate components
dissolve under conditions corresponding to those of the
deep continental crust and upper mantle. In the upper
mantle, there can be complete miscibility between H2O
and silicate (Bureau and Keppler 1999; Mibe et al. 2007).

© 2014 Mysen; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction
in any medium, provided the original work is properly credited.

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Major element solutes in aqueous fluids (silicate components) can also enhance the solubility of other components by up to orders of magnitude (Pascal and Anderson
1989; Antignano and Manning 2008; Mysen 2012a, b;
Ayers and Watson 1993). Transport, volume, and mixing
properties of silicate-rich aqueous fluids differ in important ways from those of pure H2O (Audetat and Keppler
2004; Hunt and Manning 2012; Hack and Thompson
2012; Foustoukos and Mysen 2013).
The property behavior of melts and fluids in hydrous
silicate systems at the high temperatures and pressures
can be traced to the relationships between fluid and melt
structure and their properties. Most experimental andtheoretical studies have focused on the behavior inchemically simpler systems in order to isolate the effects
of individual intensive and extensive variables. With theinformation from chemically simpler systems, we canmodel melt and fluid behavior in systems relevant to natural processes. In this review, these relationships will bepresented and their applications to natural systems will be
discussed.
Water and properties of hydrous magma
Melting phase relations

The solidus temperature depression of mantle peridotite
caused by H2O ranges between approximately 1200°C andapproximately 1600°C at the upper mantle pressures(Figure 1A). The water solubility in partial melts from aperidotite parent in this pressure range is 20 to 40 wt%(Hamilton et al. 1964; Holloway and Jakobsson 1986).
Furthermore, the extent of the solidus temperature

0.0
hy

O

O

2

2

e-H
tatit
ens

Pressure, GPa

ydrtatiteanhousPressure, GPa

s ens

alite

tob

e

1.0

per
ido
tit e

te-H 2O

5

drou

nit

peridoti

4

cris

gra

3

anhy

us

0.5

2

ous
ydr

dro

-H 2O
granite

1

B

anh

an

A

quartz-H0

depression depends on silicate composition and increases,
for example, with increasing silica content (Figure 1B). In
natural systems, this effect helps explain why the liquidus
depression caused by H2O of a felsic composition (e.g.,granitic composition) is greater than that of peridotite(Figure 1A). An implication of these observations is thatin a subduction zone water has a greater effect on solidus
temperature of descending crustal material near the slab/
peridotite interface than in an overlying peridotite wedge
or in an underlying depleted oceanic lithosphere (200°C to
300°C temperature difference; Kushiro et al. 1968b; Groveet al. 2012).
The composition of a melt in equilibrium with silicate
mineral assemblages at high pressure is affected by H2O(Figure 2). For example, at 2 to 3 GPa, in equilibriumwith enstatite + diopside + forsterite in the CaMg2O6Mg2SiO4-SiO2 system, the melt is quartz normative in thepresence of H2O and olivine normative under volatile-free
conditions (Kushiro 1969). In natural peridotite systems,
this difference persists so that partial melting of hydrous
peridotite at least to 2 GPa is quartz normative (andesite
or quartz tholeiite), whereas anhydrous peridotite melting
under these conditions results in olivine tholeliite (Kushiro1990). The silica content of partial melts is not, however,
the only compositional variable affected by H2O at highpressure and temperature. This is evident in the system
NaAlSi3O8-KAlSi3O8-SiO2 system (Figure 2B). Here, increasing water pressure (which means increasing concentration of H2O in the melt) leads to a rapid expansion of
the quartz liquidus volume relative to that of feldspar
components. This evolution means increasing alumina/

1.5

6
300

600

900
1200
Temperature, ˚C

1500

1800

2.0
1000

1200

1400
1600
Temperature, ˚C

1800

Figure 1 Pressure/temperature trajectories. (A) Granite with and without H2O (granite-H2O and anhydrous granite) and peridotite with andwithout H2O (peridotite-H2O and anhydrous peridotite) solidi (Stern et al. 1975; Kushiro et al. 1968a ) and (B) silica polymorphs and enstatite withand without H2O (cristobalite-H2O, enstatite-H2O, anhydrous cristobalite, and anhydrous enstatite) (Boyd et al. 1964; Kushiro et al. 1968a; Jackson
1976; Boettcher 1984).

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A

Page 3 of 18

SiO2

B

CaMgSi2O6
P=2 GPa
diopside

anhy

PH

2O

drou
s
hydrousquartzMg2SiO4

enstatite

MgSiO3

forsterite

0.1

0.5 G
Pa
1.0 GPaNa-feldspar

SiO2

GPa

K-feldspar

NaAlSi3O8

KAlSi3O8

Figure 2 Liquidus phase relations in hydrous and anhydrous silicate and aluminosilicate systems. (A) Pyroxene/olivine liquidus boundary
at 2 GPa in the Mg2SiO4-CaMgSi2O6-SiO2 system with and without H2O from Kushiro (1969). (B) Evolution of feldspar/quartz liquidus boundaries
in the NaAlSi3O8-KalSi3O8-SiO2 system with increasing H2O pressure compared with anhydrous 0.1 MPa liquidus boundaries H2O (data from Tuttle
and Bowen 1958; Luth et al. 1964).

silica ratio in hydrous melts derived from partial meltingof pelagic sediments compared with melting products ofhydrous oceanic basaltic crust in the upper portion of
subducting plates the higher the water content (see, forexample, Poli and Schmidt 2002).
Properties of hydrous silicate melts

Transport properties of silicate melts (e.g., viscosity, diffusion, conductivity) are quite sensitive to their watercontent. For example, melt viscosity decreases by several
orders of magnitude by a solution of as little as 1 wt%
H2O (Richet et al. 1996). This effect, however, is strongly
non-linear and diminishes with increasing water content(Figure 3A). Furthermore, deviation of melt viscosity
from Ahrrenian behavior is increasingly pronounced thehigher the water content (Figure 3B). Water effects on
viscosity are more pronounced the more felsic the melt.
Water effects also are more pronounced the higher thealkali/alkaline earth ratio. This means that the viscosityof rhyolitic melts is more sensitive to water content thanbasalt and that alkali basalt is more sensitive to watercontent than olivine tholeiite.
Most other physical properties of silicate melts show
analogous relations with water content and silicate composition. Examples include cation and water diffusion inmelts (Watson 1994; Behrens and Nowak 1997), effectsof water on glass transition temperature (Richet et al.
1996, 1997; Whittington et al. 2000), and electrical conductivity (e.g., Takata et al. 1981; Satherley and Smedley
1985). These effects exist because of the functional

relationships that exist between these transport properties(Nernst 1888; Einstein 1905; Eyring 1935a, b).

Water solubility in magmatic melts

In order to understand better the solubility behavior of
H2O in silicate melts and the silicate solubility in aqueous
solutions, examination of schematic phase relations insilicate-H2O systems can be helpful (Figure 4). Thereexists a range of pressures and temperatures where
H2O-saturated silicate melts and silicate-saturated aqueous fluids coexist (‘melt + fluid’ field in Figure 4). Thisboundary defines the water solubility in the silicate melts.
The boundary between ‘aqueous fluid’ and ‘silicate melt +aqueous fluid’ describes the silicate solubility in aqueous
fluid. At temperatures above the solvus (above the criticalpoint (c.p.) in Figure 4), there is complete miscibility between silicate melt and aqueous fluid. The temperature/pressure coordinates of the critical point ranges fromabout 1 GPa near 1,200°C for granitic compositions tonearly 4 GPa near 1,200°C for peridotite-H2O (Bureau andKeppler 1999; Mibe et al. 2007). The slope of the phaseboundaries at lower temperatures depends on pressure
and temperature itself (Holtz et al. 1995).
It follows that water solubility in magmatic melts istemperature, pressure, and silicate composition dependent.
The water solubility in melts in the simplest of silicate systems, SiO2-H2O, at low pressures is a linear function of thesquare root of water fugacity, √f H2 O (Moulson and Roberts
1961; see Figure 5A). However, with increasing pressureMysen Progress in Earth and Planetary Science 2014, 1:4
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B

1600

600

log viscosity (Pas)

14

10

H2
8

anh
y

11

wt
%

dro

18

log viscosity (Pas)

Temperature, K
1000
800

us

13

1200

O

A

9

7

5

6

1000 K3

21800 K1
0

2

4
6
H2O concentration, wt%

8

4

8

12
1/T•104 (K-1)

16

Figure 3 Viscosity of silicate melts as a function of their total H2O content and temperature. (A) Hydrous andesite melt viscosity from Richet
et al. (1996) recorded at ambient pressure by using a sample synthesized at 400 MPa and 1400˚C before viscosity measurement at ambient pressure
and temperatures indicated. (B) Temperature-dependence of melt viscosity of granite composition with (8 wt%) and without H2O as indicated on
curves from Hess and Dingwell (1996).

P1>P2

supercritical fluid
c.p.

P2
P1

fluid
melt+fluid)l(ssta ltcry +meTemperature

melt

crystal(s)+fluid
Silicate

H 2O

Figure 4 Schematic and simplified phase relations in silicate-H2O
systems at two different pressures, P1 and P2, where P1 > P2.

(and f H2 O ), the solubility is a non-linear function of √f H2 O
(Figure 5) and where the pressure dependence itself ispressure dependent (Kennedy et al. 1962; see Figure 5B).
The features in Figure 5 notwithstanding, the pressure
dependence of water solubility in more complex melts,
including natural basalt and other aluminosilicate compositions, shows no simple solubility relationship withpressure (or f H2 O ) (Figure 5C). These complex relations
likely reflect several effects on the solubility of H2O of individual silicate components. For example, in ternary
metal oxide aluminosilicate systems, water solubility iscorrelated with metal/Si and Al/Si ratios and electronic
properties of the metal cation (Kurkjian and Russell 1958;
Behrens et al. 2001; Mysen and Cody 2004; see also
Figure 6). At high metal oxide/silica ratio, the water solubility decreases as this ratio increases, but this relationshipreverses near composition where alkali metal/Si ratio isnear 1 (Kurkjian and Russell 1958). Furthermore, whereas
water solubility in peralkaline silicate melts decreases withincreasing Al/Si ratio (Figure 6B), the reverse relationships
have been observed for melts along SiO2-NaAlO2 (metaaluminosilicate) joins (McMillan and Holloway 1987).
Given the complex relationships between melt composition and water solubility, it is not surprising that

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4
3
SiO2-H2O

0.15

16
12
8

SiO2-H2O

15 20

0.25
fH2O , MPa

25 30

35

iO
aA

lS

4

PH2O~0.2-1.2 GPa

20
15

NaA

KAlSi3O8

10
5

O8
lSi 3

N

PH2O~0.2-1.2 GPa

bia
ba R.
sa
lt

5

20

lum

PH2O~0.01-0.1 MPa

Co

6

C
H2O solubility, mol %B
H2O solubility, mol %H2O solubility, mol %•103

A

Page 5 of 18

0

15

30

fH2O , MPa

fH2O , MPa

Figure 5 H2O solubility in silicate melts at low and high pressures as a function of fugacity of H2O, f H2 O . (A) Solubility in SiO2 melt at andbelow ambient pressure from Moulson and Roberts (1961). (B) Solubility in SiO2 melt at high pressure as a function of f H2 O from Kennedy et al.
(1962). (C) Solubility in various silicate melts as a function of f H2 O as compiled by McMillan (1994).

the solubility varies significantly in different magmatic
systems. In general, water solubility in felsic magmas
such as those of rhyolite and andesite composition issignificantly greater than the solubility in basalt melts(Hamilton et al. 1964; Dixon and Stolper 1995; Behrens
and Jantos 2001; Zhang 1999). This would be expected
because of the higher alkali/alkaline earth and Si/Al ratios in rhyolite and andesite melt compared with meltsof basaltic composition. These solubility relationships
have been modeled with a variety of empirical models(e.g., Spera 1974; Burnham 1975; Dixon and Stolper
1995; Behrens and Jantos 2001). However, quantitative
linkage between solubility behavior in chemically simple
melts and more complex natural magma compositions
await detailed structural characterization of the water
solution mechanisms in simple and complex magmatic
melts.

solubility in the fluid above and below the solidus of thesystem. The solubility of SiO2 in H2O has been the subject of more extensive experimental study than otherchemically more complex silicates. From a compilationof available high-pressure/high-temperature solubility
data, an effective way to describe solubility is in termsof temperature and the density of pure H2O at thetemperature (and pressure) of interest (Manning 1994;
see also Figure 7). It must be emphasized, however, thatthe empirical relationship used for this purpose,
Log mSiO2 ðmol=kgÞ ¼ 4:262−ð5764:2=TðKÞþ 1:7513•106 =T2
− 2:2868•108 =T3
þ½2:8454−ð1006:9=TÞþ 3:5689•105 =T2 • log ρH 2 O ;ð1ÞSilicate solubility in aqueous fluids

In the schematic phase diagram in Figure 4, the boundaries silicate melt + aqueous fluid/aqueous fluid and silicate
crystals + aqueous fluid/aqueous fluid define the silicate

A

B
Na2O-SiO2

34
H2O solubility, mol%24
H2O solubility, mol%uses the density of pure H2O to describe the silica
solubility, and it is known that silicate components in

22
20
18
16
14
12
0.0

Na2O•4SiO2

32
30
28 CaO•4SiO2
26

0.2

0.4 0.6
Na/Si

0.8

1.0

0

1
2
3
4
5
6
Al2O3 concentration, mol %Figure 6 H2O solubility in silicate and aluminosilicate melts with silicate composition. (A) Solubility at 1,200°C and 0.8 GPa as a function of
Na/Si of the melt from Mysen (2002). (B) Solubility at 1,200°C and 2 GPa as a function of Al2O3 content in Na2O·4SiO2 and CaO·4SiO2 melts as afunction of added Al2O3 from Mysen and Wheeler (2000).

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2000000.06
corundum

20000
2000

0.05
900
700
500
300˚C

200
20

1 GPa
-0.4

-0.3
log

-0.2
H2O

-0.1

0

0.1

(g/cm3)Pa

the solution affects the density of the solution (Mysen
2010a, b).
Additional components affect the silicate solubility
in aqueous fluid. For example, addition of MgO to SiO2
reduces the SiO2 solubility (Zhang and Frantz 2000; Kawamoto et al. 2004; see also Figure 8). The Mg/Si ratio of thefluid increases with pressure (Kawamoto et al. 2004).
Below about 3 GPa, MgO cannot be detected in the fluid(Zhang and Frantz 2000; Kawamoto et al. 2004). The decreased Mg/Si ratio of fluid with increasing pressure likely

6±

0.

2

G

2

Pa

3.

mSiO2, mol/kg

0.04

XNaCl=0.3

corundum+quartz
corundum+albite+melt

XNaCl=0.1

XNaCl=0.03

0.03
0.02
XNaCl=0.005

0.01

Figure 7 Silica solubility in fluid in equilibrium with quartz. Asa function of the density of pure H2O at 1 GPa and temperaturesindicated calculated with the algorithm of Manning (1994)(Equation 1).

2

.
±0

G

7

1.

Pa

9G

.0
±0

7

0.9

1

Pa

7G

0.0

9±
0.4

0
700

Al2O3 solubility, mol/kg

SiO2 solubility, ppm

800˚C/1 GPa

750 800 850 900
Temperature, ˚C

950

Figure 8 Solubility of silica (SiO2) in fluid. Coexisting withenstatite + forsterite (0.49 to 1.7 GPa pressure, closed symbols) andwith enstatite (3.6 GPa pressure, closed symbols) in MgO-SiO2-H2O
fluid calculated with the algorithm of Newton and Manning (2002)(results from Mysen et al. 2013).

XNaCl=0

0.00
0.0

0.4
0.8
1.2
SiO2 solubility, mol/kg

1.6

Figure 9 Solubility of Al2O3 in aqueous fluid in the system
Na2O-Al2O3-SiO2-H2O-NaCl. As a function of silica solubility and
NaCl mol fraction in fluid. Symbols indicate the coexisting solid
phases. Data from Newton and Manning (2008).

reflects the interaction between dissolved silica and MgO- perhaps similar to the solubility behavior of Al2O3 in
fluids in the system SiO2-Al2O3-H2O-NaCl where increasing SiO2 content in the fluid enhances the Al2O3 solubility(Figure 9). In the latter system, there is also a pronounced
positive effect of increasing NaCl in the fluid (Newton andManning 2008).
Oxides that are essentially insoluble in pure H2O also
can be affected quite strongly by other solutes such as
silicate and aluminosilicate components. As an example,
the solubility if Ti4+ in fluid in equilibrium with melt in
the Na2O-Al2O3-SiO2-TiO2-H2O is a strong positive
function of concentration of aluminosilicate component
in addition to temperature and pressure (Antignano andManning 2008; Mysen 2012a; see Figure 10). This is avery different solution behavior than that of TiO2 in thesimple system, TiO2-H2O; here, the Ti solubility is in theparts per million range (Audetat and Keppler 2005;
Antignano and Manning 2008). Similar effects have been
observed for P5+ and other high field strength cations(Mysen 2011; Bernini et al. 2013). It follows, therefore,that during dehydration of subducting slabs where thefluid is quite silicate rich, it will likely carry significantly
greater proportions of nominally refractory oxides thanthat expected from solubility measurements with pure
H2O as the solute (see also Manning 2004).
Melt and glass
Glass transition

Most of the experimental data on solubility and solution
behavior of water in silicate melts at high temperature

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1200
900˚C/1 GPa

NBO
BO

400

200

fluid+corundum
fluid+corundum+paragonite

0
0

5

10

15
20
25
30
Silicate in solution, wt%

35

40

Figure 10 TiO2 solubility in fluids in equilibrium. With rutile inthe system TiO2-Al-silicate (NaAlSi3O8 starting composition) as afunction of SiO2 in solution. Data from Antignano and Manning(2008).

have been obtained by analysis of the glass formed bytemperature quenching from a high-temperature/highpressure hydrous melt. Temperature-dependent structure
may change during such a cooling process and eventuallygets frozen in at the temperature of the glass transition(Dingwell and Webb 1990). By definition, the glass transition temperature (actually a small temperature range),
therefore, is that below which the material is not relaxedon the time scale of a measurement (glass), whereas
above that temperature, the material is relaxed (liquid).
In the temperature interval between a liquidus and glasstransition temperature, the material is a supercooled
liquid with the same property behavior as that of themelt above the melting temperature. These distinctions
are important when a property measured on a glass isapplied to the property behavior of its melt.

Principles of silicate melt structure

Characterization of water solution mechanisms in silicate melts, including magmatic melts, requires understanding of the principles of silicate melt structure. A
basic structure concept is a degree of polymerization of
the silicate network of oxygen tetrahedra with their centrally located tetrahedrally coordinated cation (T-cation)(Figure 11). The dominant T-cations in magmatic melts
and glasses are Si4+ and Al3+ provided that the pressure
is less than that where these cations may undergo coordination transformations (coordination transformations
begin to take place ≥5 to 6 GPa depending on whether it
is Al3+ or Si4+ and depending on the overall melt

NBO
NBO

M

BO

600

NBO

T

NBO

BO

800

NBO

Ti solubility, ppm

1000

Figure 11 Schematic representation of the concept of bridging(BO) and nonbridging (NBO) oxygen.

composition; see, for example, Ohtani et al. 1985; Leeet al. 2004). There are two types of oxygen forming thecorners of these tetrahedra. An oxygen shared by neighboring tetrahedra is termed a bridging oxygen (BO), andthe one shared between a tetrahedron and a neighboring
polyhedron that does not form tetrahedral network istermed nonbridging oxygen (NBO) (see Figure 11).
The degree of melt polymerization is defined as the proportion of nonbridging oxygen per tetrahedrally coordinated cations, NBO/T. The NBO/T of a silicate melt andglass can be calculated from its bulk composition provided
that the type and proportion of T-cations are known. Thiscan be done by keeping in mind that electrical neutrality
requires T-cations to be assigned a formal charge of 4+
and oxygen 2− so that
NBO=T ¼ ð4•XT −2•XO Þ=XT ;ð2Þ

where XT and XO are the atomic proportions of tetrahedrally coordinated cations and oxygen, respectively.
The distribution of NBO/T of major rock-forming magmatic melts suggests a general correlation between aluminosilicate concentration in the magma and their degreeof polymerization, NBO/T (Figure 12). The NBO/T ofcommon magmatic melts is the 0 to 1 range (Figure 12). It
is for this reason that most studies of simple system melt
structure have focused on melt compositions in this NBO/
T range.
Silicate glasses and melts, including those of natural
magma and many commercial glasses, can be described interms of a small number of discrete silicate polymers withinteger values for their average NBO and BO (BO = 4 −NBO) between 0 and 4 (Virgo et al. 1980; Stebbins 1987;
Maekawa et al. 1991; Buckermann et al. 1992). These entities sometimes have been described in terms of their silicate stoichiometries (TO4, T2O7, TO3, T2O5, and TO2)

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The behavior of an aqueous fluid in equilibrium withmolten or crystalline silicates at high temperature and pressure may not be addressed by examination of quenchedmaterials because most, perhaps all, of their properties (including the structure itself) cannot be determined byexamination of the high-temperature/high-pressure fluid
after quenching to ambient conditions. Fluid structurestudies require, therefore, examination while the sample
is at the temperature and pressure of interest. However,before addressing such experimental environments,
structural data from quenched melts will be discussed.

0.8
0.7
0.6

rhyolite

0.1
65

0
0.0

70

75

80

85

SiO2+Al2O3, mol %

0.2

0.4

tholeiite

10

0.4

0.2

andesite

20

0.5

0.3

phonolite

Percent

NBO/T

30

0.6

0.8

Hydrous melts quenched from high temperature at highpressure
1.0

1.2

1.4

NBO/T
Figure 12 Distribution of NBO/T values for melts of somecommon igneous rocks. The inset shows the relationship between
average values of SiO2 + Al2O3 of rhyolite (SiO2 + Al2O3 = 85.4 wt%),
phonolite (SiO2 + Al2O3 = 79.5 wt%), dacite (SiO2 + Al2O3 = 80.8 wt%), andesite (SiO2 + Al2O3 = 74.4 wt%), and tholeiite (SiO2 + Al2O3 =65.1 wt%) melts (rock composition data from http://Earthchem.org
used as described by Mysen and Richet 2005, ch. 17).

and sometimes by using the Qn species notation, Q0, Q1,
Q2, Q3, and Q4, where the superscript indicates the number of BO. Consequently, Q0 = TO4, Q1 = 0.5T2O7, Q2 =TO3, Q3 = 0.5T2O5, and Q4 = TO2. The proportion ofthese species, but not their stoichiometry, varies as a function of melt composition (metal oxide/Si and Si/Al ratios).
For any melt composition, its degree of polymerization,
NBO/T, can be calculated from the proportion of theQn species:
NBO=T ¼n¼4Xð4−nÞ•X Qn

ð3Þ

n¼0

where n is the number of bridging oxygen and X Qn mol
fraction of individual Qn species. However, Qn species
abundance obviously cannot be calculated from NBO/T
values alone.
Solution mechanisms of silicate and water in fluids andmelts in hydrous magmatic systems

Most structural data from hydrous silicate melts havebeen obtained from analysis of samples quenched fromhigh temperature and pressure to ambient conditions
prior to chemical and structural analysis. These data
reflect, therefore, the melt structural environment near
the glass transition temperature. Temperature-dependent
structural features cannot be captured in such studies.
That notwithstanding, many important principles havebeen derived from studies of quenched melt.

Water is dissolved in silicate melts in the form of watermolecules, H2O0, and structurally bound hydroxyl groups,
OH. The OH groups can form bonds with Si4+ and Al3+
as well as with other metal cations (Mysen and Virgo
1986; Xue and Kanzaki 2004; Cody et al. 2005). In either
case, water dissolved in the form of OH groups in silicate
melts affects their structure.
In the simplest of silicates, SiO2, the OH formation is
via breakage of bridging oxygen bonds (Wasserburg 1957;
Farnan et al. 1987):
Si−O−Si þ H2 O ¼ 2Si−OH;ð4Þ

where Si-O-Si represents an oxygen bridge and Si-OH a
broken bridge terminated with H+. Formulated in terms of
Qn species and supported by 29Si and 1H-29Si CP MAS
NMR (cross-polarization magic angle spinning nuclear
magnetic resonance) data for SiO2-H2O (Farnan et al. 1987;
Cody et al. 2005), this reaction can be written as
2Q4 þ nH2 O ¼ 2Q4−n ðHÞ;ð5ÞIn chemically more complex systems, the OH-forming
process also is more complex as will be discussed further
below.
From the experimental studies of temperature-quenchedhydrous glasses, the proportion, X OH =X H2 O0 , varies withtotal water concentration and with bulk chemical composition of the melt (Stolper 1982; Dixon and Stolper 1995;
Zotov and Keppler 1998; see also Figure 13). Above theglass transition temperature, the X OH =X H2 O0 is positively
correlated with temperature so that a simple water speciation reaction,
H2 O0 þ O2− ¼ 2OH− ;ð6Þshifts to the right with temperature (Nowak and Behrens
1995; see also Figure 13B). From the temperaturedependent equilibrium, an enthalpy change, ΔH, of about
30 kJ/mol has often been reported (Nowak and Behrens
1995).

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Page 9 of 18

O8

6
lSi

3

9

aA

4

Si

4

a2

O

:N

2

H

O

OH: Na2

Si4O9

OH: NaAlSi3O8

2

0
0

2

4

6

8

10

OH, H2O concentration as wt% H2O

B

H2
O:
N

OH, H2O concentration as wt% H2O

A

10
8
6

OH

4
H 2O
2
0
0

200

Concentration, H2O, wt%

400

600

800

1000

Temperature, ˚CFigure 13 Abundance of OH groups and molecular H2O as a function of water concentration and temperature. (A) Evolution of abundanceof OH groups and molecular H2O as a function of total water concentration in quenched melts (quenched from 1,100°C at 200 MPa pressure) ofcompositions indicated (data from Zotov and Keppler 1998). (B) Abundance of OH groups and molecular H2O in haplogranite composition glass andmelt as a function of temperature from Nowak and Behrens (1995) recorded in situ while the sample was at the temperature of interest as shown withthe pressure constant at 150 MPa.

Data such as those in Figure 13 do not provide information about how the OH groups form bonding
with the silicate melt structure. In the simple form ofEquation 4 whereby Si-OH bonding is formed, there isdepolymerization of the melt (NBO/T increases). By
adding one or more alkali metal or alkaline earth to
SiO2, bridging oxygen bond breakage also takes place
and an increase in NBO/Si as water is dissolved. The rateof NBO/Si change at constant total water concentration
decreases with increasing metal oxide/silicon ratio (Na/Si
in the case of the data in Figure 14; see also Cody et al.
2005). The rate of change also decreases with increasing
total water content (Figure 15).

The NBO/Si decrease caused by increasing metal/
silicon ratio (Figure 14) could occur either because the
X OH =X H2 O0 decreases with increasing metal/Si or it is because some of the OH groups form bonding with a
network-modifying metal cation instead of breaking oxygen bridges to form Si-OH bonds. A simple example iswhat might be expected in an Na2O-SiO2 melt, where Na+
in the anhydrous melt forms bonding with nonbridging
oxygen. Here, in addition to a reaction such as shown
schematically in Equation 4, a structural interaction with
Na+ can be written as

200

150

100

melt polymerization, NBO/T

100 •(NBO / Si)hydrous (NBO / Si)anhydrous,%(NBO / Si)anhydrous

1.2
14 mol % H2O

1.0

Alkali aluminosilicate melt
1.5 GPa/1400˚C

0.13

Si)=

l+
l/(A

A

=0.06

Al/(Al+Si)
0.8

0.6

0.4

50
0.2

0.4

0.6
Na/Si

0.8

1.0

Figure 14 Effect of composition of Na2O-SiO2 melt on the change
of NBO/Si caused by dissolved water. Samples were quenched at
100°C/s from 1,400°C at 1.5 GPa. In this system, the Na/Si ratio is equal
to the NBO/Si of the anhydrous melt (data from Cody et al. 2005).

10
20
30
0
H2O concentration in melt, mol %40

Figure 15 Relationship between degree of polymerization,
NBO/T (T = Al + Si), of aluminosilicate melts. As a function of thetotal water content for different values of the Al/(Al + Si) of the melt
at 1.5 GPa and 1,400°C. Data from Mysen (2007).

Mysen Progress in Earth and Planetary Science 2014, 1:4
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ð7Þ

In this example, the network-modifying Na+ bonding
with nonbridging oxygen in a Q3 species (with NBO/Si = 1)
in an anhydrous melt reacts with H2O to form NaOH
complexes in hydrous Na2O-SiO2 melts. This interaction
causes the nonbridging oxygens bonded to Na+ in anhydrous Q3 to be transformed to bridging oxygens resulting
in the formation of the more polymerized Q4 species.
Silicon-29 MAS NMR data from melts quenched from1,400°C along the Na2O-SiO2 join show that this is exactly
the situation and that the abundance of NaOH complexes
increases with increasing Na/Si (Cody et al. 2005). Similar
conclusions have been reported for alkaline earth silicate
glasses wherein Ca..OH and Mg..OH groups were formedin CaO-MgO-SiO2 melts (Xue and Kanzaki 2004).
From a compositional perspective, aluminosilicate melts
are more akin to natural magmatic melts than metal oxide
silicate melts. At pressures less than 5 to 6 GPa, Al3+ is in
tetrahedral coordination where it is charge-balanced withalkalis or alkaline earths in a manner conceptually similar
to that observed in crystalline aluminosilicates such as
feldspars (see Lee et al. 2004; for high-pressure structuraldata). The aluminate groups (AlO2−) in aluminosilicate
melts can interact with dissolved water to form either AlOH or metal-OH bonding (metal can be alkali metal or alkaline earth), or both, in addition to Si-OH bonding(Mysen and Virgo 1986; Schmidt et al. 2001). The extent
to which aluminate interaction takes place is correlatedwith the Si/Al ratio of the melt (Mysen and Virgo 1986).
The nature of the Al3+ charge balance probably also affects the solution mechanism because the Al-O bondstrength depends on the electronic properties of thecharge-balancing cation (Roy and Navrotsky 1984).
The formation of Al-OH bonding can be illustrated
schematically by using aluminate complexes, denoted as
Mm +1/mAlmO2m, to describe the silicate speciation, andAl(OH)3 as a representation of Al-OH formation in the
melt:

3
n
2
2M mþ
1=m Al m O2m þ =m H2 O þ 2Q ⇌ m AlðOHÞ3
þ2Qn−1 ð1=mM mþ Þ;
ð8Þ
Additional complexity may exist because in melts with
mixed Mm+ cations and H+, the H+, because of its size forsteric reasons, exhibits preference for forming OH groups
in the silicate portion of the network by reacting with thenonbridging oxygen in Qn species with the largest numberof nonbridging oxygens (Cody et al. 2005).
Transformation of tetrahedrally coordinated Al3+ OHbearing complexes, therefore, results in silicate depolymerization wherein the rate of depolymerization with H2O
increases the more aluminous the melt (Figure 15). This

Al/(Al+Si)=0.13
Qn-species abundance change, %2Q3 ðNaÞ þ H2 O ¼ Q4 þ 2NaOH:

Page 10 of 18

Q2

100

50

Q3
0

Q4
-50
0

10
20
H2O concentration in melt, mol %30

Figure 16 Evolution of Qn species abundance. In quenched(at 100°C/s from 1,400°C at 1.5 GPa) hydrous Na-aluminosilicate melts asa function of H2O content at fixed Al/(Al + Si) (data from Mysen 2007).

depolymerization (increasing NBO/T) takes place because
as the tetrahedrally coordinated Al3+ interacts with H2O
to form Al-OH bonds, an equivalent proportion of thecharge-balancing cation becomes a network-modifier, or
charge-balancing Na+ for Na-OH bonds leading to
network-modifying Al3+, or both. This depolymerization is
also reflected in water concentration-dependent Qn abundance as a function of total water content (Figure 16)
where the abundance of individual Qn species at a given
total water content also varies with the Al/(Al + Si) of themelt (Mysen 2007). The example from the Na2O-Al2O3SiO2-H2O system shows how depolymerized species, Q3
and Q2, become more important as more polymerized
species, Q4, abundance decreases (Figure 16).
The decreasing ∂(NBO/T)/∂X H2 O with increasing watercontent, X H2 O, reflects the decreasing rate of change ofthe abundance ratio, X OH =X H2 O0, as the total watercontent increases. This evolution, in turn, reflects thediminishing rate by which the Qn species changes with increasing concentration of water in the melt (Figure 16).
These composition-dependent solution mechanisms ofwater in aluminosilicate melts also explain why the solubility of water in silicate melt at any temperature and pressure is significantly dependent on the bulk chemicalcomposition of the melt itself.

Hydrous melts and aqueous fluids at high temperature andpressure

Experimental protocols have recently been implemented
for examination of fluids and melts in hydrous silicate
systems at deep crustal and mantle pressures and temperatures in situ while the sample is at the desiredMysen Progress in Earth and Planetary Science 2014, 1:4
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Figure 17 Evolution of ratio of hydrogen bonded to isolated OH
bonds. In hydrous Na-aluminosilicate melts and in silicate-saturated
aqueous fluids as a function of temperature (and pressure) (datafrom Mysen 2012a, b.)

40

800

Melt

35
30
Fluid

25

c.p

20
Supercritical
fluid

Concetration of molecular H2O, mol%Pressure, MPa
200
400
600

Concetration of OH groups
calculated as H2O, mol%pressure and temperature conditions. Structural data obtained under such conditions are, therefore, increasingly
available from all regions of silicate-H2O phase diagrams(Figure 4). In considering such data, commonly obtainedin so-called hydrothermal diamond anvil cells (e.g., Bassett
et al. 1994), the experiments usually are conducted in sucha manner that pressure is a variable dependent on
temperature. This means that increasing temperature normally is associated with increasing pressure. In the following discussion, this is the case unless otherwise indicated.
High-temperature/high-pressure in situ examinationof hydrous silicate systems includes characterization ofpure H2O, characterization of the silicate components,and mixtures between the two. For the H2O component
itself, the diminishing extent of hydrogen bonding withtemperature is the only structure observable. There are,however, differences between hydrogen bonding of water
dissolved in melts (typically supercooled liquids), of
silicate-saturated aqueous fluid, and pure H2O. The ΔH
for hydrogen bond formation in such melts is near 10
and about 22 kJ/mol for silicate-saturated aqueous
fluid (Figure 17). The ΔH for pure H2O is slightly
above 25 kJ/mol (Walrafen et al. 1986). Hydrogen bonding
cannot be detected spectroscopically at temperatures
above 500°C to 550°C (Foustoukos and Mysen 2012;
Mysen 2013).
In hydrous silicate systems, the ratio of mol fraction ofwater species, X OH =X H2 O0, in fluid, melt, and supercritical fluid varies with temperature (Mysen 2010b; see also
Figure 18). The X OH =X H2 O0 ratio of water in fluid andPage 11 of 18

25
c.p

20
15
10

Fluid

5
0

Melt

0

200

400
600
Temperature, ˚C

800

Figure 18 Abundance evolution (mol%) of OH groups andmolecular H2O. In coexisting melts and fluids and in supercriticalfluid as a function of temperature (and pressure) in a hydrous
Na-aluminosilicate system (data from Mysen 2010a).

melt converges at the second c.p. (Figure 18). The existenceof OH groups in all three phases (melt, fluid, supercriticalfluid) implies structural interaction between water and silicate components. In fact, structural data obtained from vibrational spectroscopy indicate that in any silicate systems,
the types of Qn species in fluids, melts, and supercriticalfluids resemble one another (Mysen 2009) although theirconcentration at any temperature and pressure depends
on the silicate composition and whether in fluids or melts.
The latter differences are evident in the NBO/T of the silicate melt being considerably lower (the melt is more polymerized) than coexisting fluid (Figure 19). The NBO/T
values approach each other with increasing temperatureand pressure until they merge at c.p. Interestingly, athigher temperature and pressure above those that define the c.p., the silicate in supercritical aqueous fluids
becomes further depolymerized (NBO/T increases) (seeFigure 19).
The NBO/T variations illustrated in Figure 19 reflect
temperature- and pressure-dependent Qn species influids and melts. Their partition coefficients, KQnfluid/melt,
at any temperature and pressure are sensitive functions

Mysen Progress in Earth and Planetary Science 2014, 1:4
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Page 12 of 18

Na2Si4O9-H2O (NS4)[Na2Si4O9]90•[Na 2(NaAl)4O9]10-H2O (NA10)

800

fluid

300

fluid

me

400

0

1

2
NBO/T

3

600

1600
1300

Pressure (NA10), MPa

c.p

1000

lt

500

1200
Pressure (NS4), MPa

l flu
itica
ercr

sup

itic

c.p
melt

600

sup
erc
r

700
Temperature, ˚C

id

al f
luid

800

1000

700

400
4

Figure 19 Degree of silicate polymerization, NBO/T. In silicate inhydrous melts, silicate-saturated aqueous fluid, and supercritical fluidin a hydrous Na-aluminosilicate system (data from Mysen 2012a, b)of the degree of polymerization of the species (Figure 20).
The KQnfluid/melt of the least polymerized Qn species isthe largest and then decreases systematically as the nvalue increases. Moreover, this effect becomes increasingly pronounced as the temperature and pressure decreases. The latter effect results from two factors. First,
the aluminosilicate solubility in aqueous fluid decreases
with decreasing pressure and temperature. The loweredsilicate concentration leads to increasing abundance ofless polymerized Qn species in the fluid (Mysen 2010a).
Second, the extent to which the silicate species in the hydrous melts are affected by dissolved water is a positive
function of water content (Figure 16) and water solubility
decreases with decreasing pressure (and temperature).

Both effects would cause the KQnfluid/melt partition coefficients to increase.
In the compositionally simple silica-H2O system in the
400°C to 900°C temperature range at pressures at andbelow about 1.4 GPa, only Q0 and Q1 species in thefluid can be detected. The equilibrium constant for thepolymerization equilibrium in fluids is
K ¼ X Q1 =X Qo ;

ð9Þwith ΔH = 13.3 ± 1.5 kJ/mol (Mysen 2010b) if it is assumed that ΔV = 0 for this equilibrium, and, therefore,that the increasing pressure governed by increasing
temperature does not affect the equilibrium. However,the partial molar volume of Q0 species is smaller thanthat of Q1 species (Bottinga and Richet 1995) so thatwith the likelihood of ΔV > 0, the ΔH = 13.3 kJ/mol is aminimum value. At higher pressures (≥1.8 ± 0.2 GPa;see Mysen et al. 2013), the positive pressure- andtemperature-dependent total silica concentration in fluid
leads to further polymerization of the silicate species,

Pa

37 M
7M

0˚C

4

/41

400

˚C/2

6

50

melt
K Qfluid/melt= XQfluidnn / X n
Q

Pa

8

2

17
C/5

a

MP

˚

600

0

Q3

Q2
Q1
n
Q -species

Q0

Figure 20 Qn species partitioning between coexisting fluid andmelt. As a function of type of Qn species, temperature, and pressure
in a hydrous Na-aluminosilicate system (data from Mysen 2012a, b).

Figure 21 Temperature (1/T) vs. ln K relationship for theequilibrium, 2Q1 ⇌ Q0 + Q2, (Equation 10). From the system
SiO2-H2O with aqueous fluid in equilibrium with quartz (lower
pressure) or coesite (higher pressure). Data from Mysen et al. (2013).

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Page 13 of 18

and Q2 species are also observed (Mysen et al. 2013)
with the Qn species equilibrium,
2Q1 ⇌Q0 þ Q2 ;

ð10Þfor which the ΔH clearly is pressure dependent (Figure 21).
The pressure/ΔH relationship reflects the fact the ΔV ofreaction (10) is between −1 and −2 cm3/mol (Mysen et al.
2013).
The system SiO2-H2O is too simple for modeling natural processes because neither Al2O3 nor alkali metals
and alkaline earths are involved. The system Na2OAl2O3-SiO2 is more realistic even though alkaline earths,
in particular, have not yet been addressed. The Na2OAl2O3-SiO2 system is also useful for characterization of
the chemical interaction between nonbridging oxygenand important network-modifying cation (Na+) and protons (H+).
From NMR spectroscopy of quenched melts in thissystem, there is a strong preference of H+ for nonbridging oxygen in the least polymerized of the Qn species(Q0), whereas Na+ forms bonds with nonbridging oxygenin the more polymerized Qn species (Cody et al. 2005;
see also Equation 7). From the in situ structural characterization in alkali aluminosilicate systems, a more complex reaction (Mysen 2010a)
12Q3 ðMÞ þ 13H2 O⇌2Q2 ðMÞ þ 6Q1 ðMÞ þ 4Q0 ðHÞ;ð11Þ
describes the equilibrium. Here, M denotes an alkali
metal and where (M) and (H) indicate where alkali metals
and protons form bonding with the relevant nonbridging
oxygens, respectively. The tetrahedrally coordinatedcations forming the Qn species can be either Al3+ or Si4+.
The ΔH for this equilibrium (350 to 400 kJ/mol) is thesame, within uncertainty for melt fluids and supercriticalfluids (Mysen 2010a). With increasing Al/(Al + Si), equilibrium (11) likely shifts to the left (ΔH decreases) because
Al3+ will preferably occupy the most polymerized ofavailable Qn species (Merzbacher and White 1991). In
Equation 11, that species is Q3, but for other morepolymerization melt compositions, Q4 species likely also
would be involved. The principles outlined in equilibrium(11) may also be applied to alkaline earths, but quantitative information awaits further experiments. These are allconsiderations necessary for the application of the experimental data to hydrous magmatic systems. However, thenecessary experimental data are at present insufficiently
comprehensive for quantitative application.

Discussion
Dissolved water and melt properties

The evolution of Qn species abundance of a melt withwater content can be used to characterize how dissolved

water governs phase relations and mixing properties ofmelts. For example, the rapid abundance increase ofdepolymerized species at the expense of polymerized
species with water content of the melt enhances the stability of depolymerized relative to more polymerized
liquidus phases. An example of this effect can be seen in
the silica/pyroxene liquidus boundary of the Mg2SiO4CaMgSi2O6-SiO2 system where the silica polymorph ismore polymerized than pyroxene (their NBO/Si are
0 and 2, respectively) (Figure 2A). The magnitude ofliquidus boundary shifts will reflect the size of the
NBO/Si difference between the minerals coexistingalong a liquidus boundary. The greater the NBO/Si difference, the greater is the effect of water on the shift ofthe boundary as illustrated, for example, by the different
shifts of olivine/pyroxene and pyroxene/silica liquidus
boundaries (Kushiro 1969). Effects such as these also explain why hydrous melts in equilibrium with peridotite
mineral assemblages is more silica rich (quartz normative andesitic melts) than under anhydrous conditions(olivine normative tholeiitic melts) during melting andcrystallization in the upper mantle.
Configurational properties of melts can be linked totransport and thermodynamic properties of melts (Adamand Gibbs 1965; Richet 1984; Lee and Stebbins 1999).
For example, melt viscosity, η, is a function of configurational entropy:η ¼ Ae exp Be =T S conf

ð12Þ

where Ae and Be are constants, T is temperature, andSconf is configurational entropy. The Sconf is described interms of configurational heat capacity:

S

conf

ðT Þ ¼h

C confpi 
T g =T g þ

ZT C confp =T dT ;Tg

ð13Þ
where Tg is glass transition temperature, T is thetemperature of interest (T > Tg), and Cpconf(Tg) is theconfigurational heat capacity at the glass transition
temperature. This configurational heat capacity of hydrous magmatic melts is a systematic function of thewater content of the melt (Richet et al. 1996; Bouhifd
et al. 2006).
Changes in configurational heat capacity resulting
from H2O dissolved in the melt can be calculated fromthe experimental data on Qn species abundance in hydrous melts combined with the knowledge of the partial
molar heat capacity of individual species (Richet and
Neuville 1992; see also Mysen 2007). For example, withsuch information, the effects of water on the heat capacity change across the glass transition measured for aMysen Progress in Earth and Planetary Science 2014, 1:4
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Page 14 of 18

Water and fluid-melt equilibria

Trace and minor element partitioning is also sensitive tomelt polymerization (Mysen and Virgo 1980; Kohn and
Schofield 1994; Jaeger and Drake 2000; Toplis and Corgne
2002). From the relationship between NBO/T and watercontents of such melts

100 •Cpconf (hydr) Cpconf (anhydr),%
Cpconf (anhydr)

25

20

15

NBO=T ¼ 1:10−0:57•e−0:068X H2 O ;10

5

Na2Si4O9-Na2(NaAl)4O9-H2O
Al/Al+Si=0.189
phonolite

0
0

10
20
30
40
H2O oncentration in melt, mol %Figure 22 Calculated and observed change of configuration
heat capacity. Comparison of calculated and observed change ofconfiguration heat capacity, Cpconf
across the glass transition for a,hydrous phonolite melt as a function of water content of the melt.
Experimental data for phonolite from Bouhifd et al. (2006). Structuraland thermodynamic data used to derive partial molar configurational
entropy of Qn species are from Mysen (2010a) and Richet and
Neuville (1992), respectively. This calculation was originally reported
in Mysen (2007).

phonolite melt can be modeled quite precisely from ahydrous haplophonolitic composition in the Na2O-Al2O3SiO2 system (Figure 22). The NBO/T and Al/(Al + Si) of
this haplophonolite melt resemble that of the natural
phonolite melt composition. The good match between
calculated and observed configurational heat capacitychanges with water content illustrates how those compositional parameters are central to characterization ofconfigurational properties of melts.

A

and NBO/T and KMgol-melt (Kushiro and Mysen 2002;
see also Figure 23A), changes in the olivine/melt partition coefficient with water content can be calculated(Figure 23B). In the calculation in Figure 23, it is assumed that there is no structural interaction between
the silicate components and the element in question(Mg). Under such circumstances, the NBO/T changes inmelt have effects on partition coefficients in ways analogous to NBO/T changes affected by adding other oxide
components. The 25% change in the Mg partition, whichreached with near 20 mol% H2O, is not an unreasonablesituation during island arc melting and crystallization(see, for example, Grove et al. 2012, for review of data).
Stable isotope fractionation

Vibrational spectroscopy has also been used to determine
D/H ratios in fluids and melts in equilibrium during experiments in diamond anvil cells at the high temperaturesand pressures of interest (Foustoukos and Mysen 2012;
Mysen 2013). In silicate-saturated fluids and hydrous silicate melts, D+ and H+ forms bonding with nonbridging
oxygen in the Qn species. From deuterium and proton
MAS NMR of silicate melts, a D/H fractionation between
the different structural positions has been found (Wanget al. 2011). This means that if the proportion and/or typeof Qn species vary with temperature and/or pressure sothat the D/H fractionation within and between fluids andB
0l melt-change with H2O, %KMg

0l melt
KMg

-3.4

.75e

8+9

=2.6

6

elt

7

0

ol-m

K Mg

8

ð14Þ

3NB
O/T

5
4
3

-5

-1 0
-1 5

-2 0
-2 5

0. 5

1. 0

1. 5
NBO/T

2. 0

2. 5

0

5

10

15

20

H2O concentration in melt, mol %Figure 23 Olivine-melt partition coefficients for Mg. As a function of the NBO/T of the melt from experimental data in the Na2O-K2O-CaOMgO-FeO-Al2O3-SiO2 system (Kushiro and Mysen 2002) coupled with the effect of dissolved H2O on NBO/T (Mysen 2007) of melts to derive effectof dissolved water in melt on the partition coefficient as discussed by Mysen 2012a, b. (A) The KMgol-melt data fitted to the equation shown in thisfigure. (B) Resulting calculated change in Mg partition coefficients as a function of water content.

Mysen Progress in Earth and Planetary Science 2014, 1:4
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Page 15 of 18

Pressure (high density) MPa
1200
900
600

A
-0.2
-0.4

Pressure (low density) MPa
400
300
200

Pressure (low density) MPa
400
300
200

fluid
high-density fluid
low-density fluidln(D/H)melt-0.6
ln(D/H)fluid

Pressure (high density) MPa
1200
900
600

B

-0.8
-1.0

-0.4

melt

-0.6

high-density fluid
low-density fluid

-0.8
-1.0
-1.2
-1.4

-1.2

-1.6

-1.4

-1.8
-1.6
0.9

1.0

1.1

1.2 1.3
1/T•103(K-1)

1.4

1.5

-2.0
0.9

1.0

1.1

1.2 1.3
1/T•10 3(K-1)

1.4

1.5

Figure 24 Evolution of D/H ratio of coexisting fluid (A) and melt (B) for (H2O + D2O)-bearing Na-aluminosilicate melts. As a function ofdifferent fluid densities. In these experiments, the fluid density governs the relationship between temperature and pressure as shown in the
figures. Data from Mysen 2013.

melts also become temperature and pressure dependent(Figures 24 and 25).
The temperature and pressure effects in Figure 24 reflect the changes in silicate concentration and speciationin the coexisting aqueous fluid and silicate melts. Furthermore, different D/H values for different fluid densities
again reflect the concentration and type of Qn species

Figure 25 (D/H) fluid-melt partition coefficients for coexisting
fluid and melt (Figure 24). For low- and high-density aqueous fluid
from the data in Figure 24.

because the different density trajectories reflect pressure/temperature trajectories of the diamond cell experimentsthat followed different pressure paths (Mysen 2013). It follows from the different trajectories of D/H ratios in fluids
and melts that the D/H partitioning between fluids andmelts will also be dependent on temperature and pressure(Figure 25). Finally, in silicate mineral/aqueous fluid orsilicate mineral/hydrous melt environments, temperatureand pressure-dependent partitioning will also take placebecause of the temperature/pressure dependence of theD/H fractionation with the fluid and melt phases.

Conclusions
Understanding the role of hydrous melts and silicaterich fluids in transport processes depends sensitively on
how chemical composition, temperature, and pressure
govern the physicochemical properties of these materials(viscosity, diffusion, thermodynamics of mixing, element
partitioning between phases, phase relations, etc.; see, forexample, Mysen and Richet 2005, for review of experimental and theoretical information of structure-property
relations of silicate glasses and melts). Attainment of thisobjective requires well-determined solubilities in and partitioning between melts, fluids, and crystalline phases, detailed understanding of the oxide solution mechanisms inmelts and fluids, and determination of how fluid and melt
structure governs those properties.
Structural information cannot be obtained directly on
chemically complex natural systems because the resolving power of spectroscopic methods employed for such
purposes diminishes rapidly with increasing chemicalcomplexity. However, structural data from simpler binary

Mysen Progress in Earth and Planetary Science 2014, 1:4
http://www.progearthplanetsci.com/content/1/1/4

and ternary systems can be used to describe the more
complex systems. This objective requires, however, detailed characterization of silicate speciation in fluids andmelts as a function of Al/Si ratio, the type of charge balance for tetrahedrally coordinated cations, and the type
and proportion of network-modifying metals (alkali metals
and alkaline earths). Currently, a combination of structural
information and empirical relationships can be applied todescribe liquidus phase relations and fluid/mineral/meltelement and stable isotope partitioning. Transport properties can be understood and sometimes quantified in termsof configurational properties of individual Qn species.
However, the experimental database used for these
purposes dominantly is from alkali silicate and alkali
aluminosilicate systems. This permits application tofelsic magmatic systems. However, the lack of much information in alkaline earth aluminosilicate system
makes quantitative application to hydrous basaltic lessquantitative.
Competing interests
The author declares that he has no competing interests.
Acknowledgements
Many of the ideas and conclusions discussed in this review were developed
during the preparation of invited lectures at Tohoku University, Japan in
2013. Portions of the reviewed research were supported by grants from the
National Science Foundation (US) (EAR-0707861, EAR1250449, EAR12151931
and EAR-1212754).
Received: 3 December 2013 Accepted: 10 March 2014
Published: 22 April 2014
References
Adam G, Gibbs JH (1965) On the temperature dependence of cooperative
relaxation properties in glass-forming liquids. J Chem Phys 43:139–146
Antignano A, Manning CE (2008) Rutile solubility in H2O, H2O -SiO2, and H2ONaAlSi3O8 fluids at 0.7-2.0 GPa and 700–1000 degrees C; implications formobility of nominally insoluble elements. Chem Geol 255:283–293
Audetat A, Keppler H (2004) Viscosity of fluids in subduction zones. Science
303:513–516
Audetat A, Keppler H (2005) Solubility of rutile in subduction zone fluids, as
determined by experiments in the hydrothermal diamond anvil cell. Earth
Planet Sci Lett 232:393–402
Ayers JC, Watson EB (1993) Apatite/fluid partitioning of rare-earth elements andstrontium; experimental results at 1.0 GPa and 1000 degrees C andapplication to models of fluid-rock interaction. Chem Geol 110:299–314
Bassett WA, Shen AH, Bucknum M, Chou IM (1994) A new diamond cell forhydrothermal studies to 2.5 GPa and from −190˚C to 1200˚C. Rev Sci
Instrum 64:2340–2345
Behrens H, Jantos N (2001) The effect of anhydrous composition on watersolubility in granitic melts. Amer Miner 86:14–20
Behrens H, Nowak M (1997) The mechanisms of water diffusion in polymerized
silicate melts. Contrib Miner Petrol 126:377–385
Behrens H, Meyer M, Holtz F, Nowak M (2001) The effect of alkali ionic radius,
temperature, and pressure on the solubility of water in MAlSi3O8 melts(M=Li, Na, K, Rb). Chem Geol 174:275–289
Bernini D, Audetat A, Dolejs A, Keppler H (2013) Zircon solubility in aqueous
fluids at high temperatures and pressures. Geochim Cosmochim Acta
119:178–187
Boettcher AL (1984) The system SiO2-H2O-CO2: Melting solubility mechanisms ofcarbon and liquid structure to high pressures. Amer Miner 69:823–834
Bottinga Y, Richet P (1995) Silicate melts: The "anomalous" pressure dependenceof the viscosity. Geochim Cosmochim Acta 59:2725–2732

Page 16 of 18

Bouhifd MA, Whittington A, Roux J, Richet P (2006) Effect of water on the heat
capacity of polymerized aluminosilicate glasses and melts. Geochem
Cosmochim Acta 70:711–722
Boyd FR, England JL, Davis BCT (1964) Effect of pressure on the melting andpolymorphism of enstatite, MgSiO3. J Geophys Res 69:2101–2109
Buckermann W-A, Muller-Warmuth W, Frischat GH (1992) A further 29Si MAS NMR
study on binary alkali silicate glasses. Glasstechnische Bericht 65:18–21
Bureau H, Keppler H (1999) Complete miscibility between silicate melts andhydrous fluids in the upper mantle; experimental evidence and geochemical
implications. Earth Planet Sci Lett 165:187–196
Burnham CW (1975) Thermodynamics of melting in experimental silicate-volatilesystems. Geochim Cosmochim Acta 39:1077–1084
Cody GD, Mysen BO, Lee SK (2005) Structure vs. composition: A solid state1
H and 29Si NMR study of quenched glasses along the Na2O-SiO2-H2O join.
Geochim Cosmochim Acta 69:2373–2384
Dingwell DB, Webb SL (1990) Relaxation in silicate melts. Eur J Mineral 2:427–449
Dixon JE, Stolper EM (1995) An experimental study of water and carbon dioxide
solubilities in mid-ocean ridge basaltic liquids; Part II, Applications todegassing. J Petrol 36:1633–1646
Einstein A (1905) Über die von der molekular-kinetischen Theorie der Wärme
geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen.
Ann Phys 17:549–560
Eyring H (1935a) The activated complex in chemical reactions. J Chem Phys
3:107–115
Eyring H (1935b) The activated complex and the absolute rate of chemical
reactions. Chem Rev 17:65–77
Farnan I, Kohn SC, Dupree R (1987) A study of the structural role of water inhydrous silica using cross-polarisation magic angle NMR. Geochim
Cosmochim Acta 51:2869–2874
Foustoukos DI, Mysen BO (2012) D/H isotopic fractionation in the H2-H2O systemat supercritical water conditions: Composition and hydrogen bonding
effects. Geochim Cosmochim Acta 86:88–102
Foustoukos DI, Mysen BO (2013) H/D methane isotopologues dissolved inmagmatic fluids: Stable hydrogen isotope fractionations in the Earth’s
interior. Amer Miner 98:946–954
Grove TL, Elkins-Stanton LT, Parman SW, Chatterjee N, Muntner O, Gaetani GA(2003) Fractional crystallization and mantle-melting controls on calc-alkalinedifferentiation trends. Contrib Miner Petrol 145:515–543
Grove TL, Till CB, Krawczynski MJ (2012) The roleof H2O in subduction zone
magmatism. Ann Rev Earth Planet Sci 40:413–439
Hack A, Thompson AB (2012) Density and viscosity of hydrous magmas andrelated fluids and their role in subduction zone processes. J Petrol 52:1333–
1362
Hamilton DL, Burnham CW, Osborn EF (1964) The solubility of water and theeffects of oxygen fugacity and water content on crystallization of mafic
magmas. J Petrol 5:21–39
Hess K-U, Dingwell DB (1996) Viscosities of hydrous leucogranitic melts: A
non-Ahrrenian model. Amer Miner 81:1297–1300
Holloway JR, Jakobsson S (1986) Volatile solubilities in magmas: Transport ofvolatiles from mantles to planet surfaces. J Geophys Res 91:505–508
Holtz F, Behrens H, Dingwell DB, Johannes W (1995) H2O solubility inhaplogranitic melts: Compositional, pressure, and temperature dependence.
Amer Miner 80:94–108
Hunt JD, Manning CE (2012) A thermodynamic model for the system SiO2 -H2O
near the upper critical end point based on quartz solubility experiments at
500–1100 degrees C and 5–20 kbar. Geochim Cosmochim Acta 86:196–213
Jackson I (1976) Melting of the silica isotypes SiO2, BeF2 and GeO2 at elevatedpressures. Phys Earth Planet Int 13:218–231
Jaeger WL, Drake MJ (2000) Metal-silicate partitioning of Co, Ga, and W;
dependence on silicate melt composition. Geochim Cosmochim Acta64(22):3887–3895
Kawamoto T, Ochiai S, Kagi H (2004) Changes in the structure of water deduced
from the pressure dependence of the Raman OH frequency. J Chem Phys
120:5867–5870
Kennedy GC, Wasserburg GJ, Heard HC, Newton RC (1962) The upper threephase region in the system SiO2-H2O. Amer J Sci 260:501–521
Kohn SC, Schofield PF (1994) The importance of melt composition in controlling
trace-element behaviour: An exprimental study of Mn and Zn partitioning
between forsterite and silicate melt. Chem Geol 117:73–87
Kurkjian CR, Russell LE (1958) Solubility of water in molten alkali silicates. J Soc
Glass Techn 42:130T–144T

Mysen Progress in Earth and Planetary Science 2014, 1:4
http://www.progearthplanetsci.com/content/1/1/4

Kushiro I (1969) The system forsterite-diopside-silica with and without water athigh pressures. Amer J Sci 267-A:269–294
Kushiro I (1972) Effect of water on the composition of magmas formed at highpressures. J Petrol 13:311–334
Kushiro I (1990) Partial melting of mantle wedge and evolution of island arc
crust. J Geophys Res 95:15929–15939
Kushiro I, Mysen BO (2002) A possible effect of melt structure on the Mg-Fe2+
partitioning between olivine and melt. Geochim Cosmochim Acta 66:2267–2273
Kushiro I, Yoder HS, Nishikawa M (1968a) Effect of water on the melting of
enstatite. Geol Soc Amer Bull 79:1685–1692
Kushiro I, Syono Y, Akimoto SI (1968b) Melting of a peridotite nodule at highpressures and high water pressures. J Geophys Res 73:6023–6029
Lee SK, Stebbins JF (1999) The degree of aluminum avoidance in aluminumsilicate glasses. Amer Miner 84:937–945
Lee SK, Cody GD, Fei Y, Mysen BO (2004) Nature of polymerization andproperties of silicate melts at high pressure. Geochem Cosmochim Acta
68:4189–4200
Luth WC, Jahns RH, Tuttle OF (1964) The granite system at pressures of 4 to 10
kilobars. J Geophys Res 69:759–773
Maekawa H, Maekawa T, Kawamura K, Yokokawa T (1991) The structural groupsof alkali silicate glasses determined from 29Si MAS-NMR. J Non-Cryst Solids
127(1):53–64
Manning CE (1994) The solubility of quartz in H2O in the lower crust and upper
mantle. Geochim Cosmochim Acta 58:4831–4840
Manning CE (2004) The chemistry of subduction-zone fluids. Earth Planet Sci Lett
223:1–16
McMillan PF (1994) Water solubility and speciation models. In: Carroll MR,
Holloway JR (ed) Volatiles in magmas. Mineralogical Society of America,
Washington DC, pp 131–156
McMillan PF, Holloway JR (1987) Water solubility in aluminosilicate melts. Contr
Miner Petrol 97:320–332
Merzbacher CI, White WB (1991) The structure of alkaline earth aluminosilicate
glasses as determined by vibrational spectroscopy. J Non-Cryst Solids
130:18–34
Mibe K, Kanzaki M, Kawamoto T, Matsukage KN, Fei Y, Ono S (2007) Second
critical endpoint in the peridotite-H2O system. J Geophys Res 112. doi:
10.1029/2005JB004125
Moulson AJ, Roberts JP (1961) Water in silica glass. Trans Faraday Soc
57:1208–1216
Mysen BO (2002) Water in peralkaline aluminosilicate melts to 2 GPa and 1400°C.
Gechim Cosmochim Acta 66:2915–2928
Mysen BO (2007) The solution behavior of H2O in peralkaline aluminosilicate
melts at high pressure with implications for properties of hydrous melts.
Geochim. Cosmochim. Acta, 71, 1820–1834. Geochim Cosmochim Acta
71:1820–1834
Mysen BO (2009) Solution mechanisms of silicate in aqueous fluid and H2O incoexisting silicate melts determined in-situ at high pressure and hightemperature. Geochim Cosmochim Acta 73:5748–5763
Mysen BO (2010a) Structure of H2O-saturated peralkaline aluminosilicate melt
and coexisting aluminosilicate-saturated aqueous fluid determined in-situ to
800˚C and ~800 MPa. Geochim Cosmochim Acta 74:4123–4139
Mysen BO (2010b) Speciation and mixing behavor of silica-saturated aqueous
fluid at high temperature and pressure. Amer Miner 95:1807–1816
Mysen BO (2011) An experimental study of phosphorous and aluminosilicate
speciation in and partitioning between aqueous fluids and silicate melts
determined in-situ at high temperature and pressure. Amer Miner 96:1636–1649
Mysen BO (2012a) High-pressure/-temperature titanium solution mechanisms insilicate-saturated aqueous fluids and hydrous silicate melts. Amer Miner
97:1241–1251
Mysen BO (2012b) Silicate-COH melt and fluid structure, their physicochemical
properties, and partitioning of nominally refractory oxides between melts
and fluids. Lithos 148:228–246
Mysen BO (2013) Hydrogen isotope fractionation between coexisting hydrous
melt and coexisting silicate-saturated aqueous fluid: An experimental study
in-situ at high pressure and temperature. Amer Miner 98:376–386
Mysen BO, Virgo D (1980) Trace element partitioning and melt structure;
an experimental study at 1 atm pressure. Geochim Cosmochim Acta
44(12):1917–1930
Mysen BO, Virgo D (1986) Volatiles in silicate melts at high pressure andtemperature. 1. Interaction between OH groups and Si4+, Al3+, Ca2+, Na+ and
H+. Chem Geol 57:303–331

Page 17 of 18

Mysen BO, Wheeler K (2000) Solubility Behavior of Water in Haploandesitic Meltsat high Pressure and high Temperature. Amer Miner 85:1128–1142
Mysen BO, Cody GD (2004) Solubility and solution mechanism of H2O in alkali
silicate melts and glasses at high pressure and temperature. Geochem
Cosmochim Acta 68:5113–5126
Mysen BO, Richet P (2005) Silicate glasses and melts: properties and structure.
Developments in geochemistry. Elsevier, New York
Mysen BO, Mibe K, Chou I-M, Bassett WA (2013) Structure and equilibria amongsilicate species in aqueous fluids in the upper mantle: Experimental SiO2-H2Oand MgO-SiO2-H2O data recorded in-situ to 900˚C and 5.4 GPa. J Geophys
Res 118. doi:10.1002/2013JB010537
Nernst W (1888) Zur Kinetik der in lösung befindtlicher Körper. Erste Abhandlung,
Theorie der Diffusion. Z Phys Chem 2:613–637
Newton RC, Manning CE (2002) Solubility of enstatite+forsterite in H2O in deep
crust/upper mantle conditions: 4 to 15 kbar and 700 to 900˚C. Geochim
Cosmochim Acta 66:4165–4176
Newton RC, Manning CE (2008) Solubility of corundum in the system Al2O3–
SiO2–H2O–NaCl at 800 °C and 10 kbar. Chem Geol 249:250–261
Nowak M, Behrens H (1995) The speciation of water in haplogranitic glasses andmelts by in-situ, near-infrared spectroscopy. Geochim Cosmochim Acta
59:3445–3450
Ochs FA, Lange RA (1999) The density of hydrous magmatic liquids. Science
283:1314–1317
Ohtani E, Taulelle F, Angell CA (1985) Al3+ coordination changes in liquid silicates
under pressure. Nature 314:78–81
Pascal ML, Anderson GM (1989) Speciation of Al, Si, and K in supercriticalsolutions: Experimental study and interpretation. Geochim Cosmochim Acta
53:1843–1856
Poli S, Schmidt MW (2002) Petrology of subducted slabs. Ann Rev Earth PlanetSci 30:207–235
Richet P (1984) Viscosity and configurational entropy of silicate melts. Geochim
Cosmochim Acta 48:471–483
Richet P, Neuville DR (1992) Thermodynamics of silicate melts: configurational
properties. In: Saxena SK (ed) Thermodynamic data: systematics andestimation. Advances in physical geochemistry, vol 10. Springer, New York,pp 132–161
Richet P, Lejeune A-M, Holtz F, Roux J (1996) Water and the viscosity of andesite
melts. Chem Geol 128:185–197
Richet P, Neuville DR, Holtz F (1997) Viscosity of water-bearing melts. Terra Nova
Abstr Supple 9(480)
Roy BN, Navrotsky A (1984) Thermochemistry of charge-coupled substitutions insilicate glasses:-The systems Mn+
n AlO2 - SiO2 (M=Li, Na, K, Rb, Cs, Mg, Ca, Sr,
Ba, Pb). J Amer Ceram Soc 67:606–610
Satherley K, Smedley SI (1985) The electrical conductivity of some hydrous andanhydrous molten silicates-as a function of temperature and pressure.
Geochim Cosmochim Acta 49:769–777
Schmidt BC, Riemer T, Kohn SC, Holtz F, Dupree R (2001) Structural implicationsof water dissolution in haplogranitic glasses from NMR spectroscopy:
Influence of total water content and mixed alkali effect. Geochim
Cosmochim Acta 65:2949–2964
Spallanzani L (1798) Viaggi alle Due Sicilie e in alcune parti dell' Appennino, transl.
as Travels in the Two Sicilies and Some Parts of the Appenines, J. Robinson,
London. Stamperia di B, Comini, Pavia
Spera FJ (1974) A thermodynamic basis for predicting water solubilties insilicatemelts and implications for the low velocity zone. Contr Mineral Petrol
45:175–186
Stebbins JF (1987) Identification of multiple structural species in silicate glasses
by 29Si NMR. Nature 330:465–467
Stern CR, Huang W-L, Wyllie PJ (1975) Basalt-andesite-rhyolite-H2O: Crystallizationintervals with excess H2O and H2O-undersaturated liquidus surfaces to 35
kilobars, with implications for magma genesis. Earth Planet Sci Lett 28:189–196
Stolper E (1982) The speciation of water in silicate melts. Geochim Cosmochim
Acta 46:2609–2620
Takata M, Acocella J, Tomozawa M, Watson EB (1981) Effect of water content
on the electrical conductivity of Na2O•3SiO2 glass. J Amer Ceram Soc
64:719–724
Toplis MJ, Corgne A (2002) An experimental study of element partitioning
between magnetite, clinopyroxene and iron-bearing silicate liquids withparticular emphasis on vanadium. Contrib Mineral Petrol 144:22–37
Tuttle OF, Bowen NL (1958) Origin of granite in light of experimental studies inthe system NaAlSi3O8-KAlSi3O8-SiO2-H2O. Geol Soc Amer Mem 74:1–153

Mysen Progress in Earth and Planetary Science 2014, 1:4
http://www.progearthplanetsci.com/content/1/1/4

Page 18 of 18

Virgo D, Mysen BO, Kushiro I (1980) Anionic constitution of 1-atmosphere silicate
melts: implications of the structure of igneous melts. Science 208:1371–1373
Walrafen GE, Yang WH, Chu YC (1996) Raman OD-stretching overtone spectrafrom liquid D2O between 22 and 152 decrees C. C. J Phys Chem
100:1381–1391
Wang YB, Cody SX, Cody GD, Mysen BO (2011) 2H and 1H NMR study onhydrogen isotope effects in silicate glasses. Paper presented at the 2011 AGU
Fall Meeting, San Francisco, CA
Wasserburg GJ (1957) The effects of H2O in silicate systems. J Geol 65:15–23
Watson EB (1994) Diffusion in volatile-bearing magmas. In: Carroll MR, Holloway
JR (ed) Volatiles in magmas: reviews in mineralogy, 30th edition.
Mineralogical Society of America, Washington, DC, pp 371–411
Whittington APR, Holtz F (2000) Water and the viscosity of depolymerized silicate
melts. Geochim Cosmochim Acta 64:3725–3736
Xue Y, Kanzaki M (2004) Dissolution mechanisms of water in depolymerized
silicate melts: Constraints from 1H and 29Si NMR spectroscopy and ab initio
calculations. Geochim Cosmochim Acta 68:5027–5057
Zhang Y-G, Frantz JD (2000) Enstatite-forsterite-water equilibria at elevatedtemperatures and pressures. Amer Miner 85:918–925
Zhang Y (1999) H2O in rhyolitic glasses and melts: measurements, speciation,solubility, and diffusion. Rev Geophys Space Phys 37:493–516
Zotov N, Keppler H (1998) The influence of water on the structure of hydrous
sodium tetrasilicate glasses. Amer Miner 83:823–834
doi:10.1186/2197-4284-1-4
Cite this article as: Mysen: Water-melt interaction in hydrous magmatic
systems at high temperature and pressure. Progress in Earth andPlanetary Science 2014 1:4.

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