Petrology, Vol. 13, No. 5, 2005, pp. 407–426. Translated from Petrologiya, Vol. 13, No. 5, 2005, pp. 451–472.
Original Russian Text Copyright © 2005 by Bezmen, Zharikov, Zevel’sky, Kalinichev.
English Translation Copyright © 2005 by åÄIä “Nauka /Interperiodica” (Russia).
Melting of Alkali Aluminosilicate Systems
under Hydrogen–Water Fluid Pressure, Ptot = 2 kbar
N. I. Bezmen*, V. A. Zharikov*, V. O. Zevel’sky**, and A. G. Kalinichev*
*Institute of Experimental Mineralogy, Russian Academy of Sciences,
Chernogolovka, Moscow oblast, 142432 Russia
e-mail: [email protected]
**Institute of Physiologically Active Substances, Russian Academy of Sciences,
Chernogolovka, Moscow oblast, 142432 Russia
Received April 13, 2004
Abstract—The melting curves of albite and albite–quartz and albite–orthoclase–quartz eutectics were studied
at a water–hydrogen fluid pressure of 2 kbar using high-pressure gas apparatuses. Instead of buffer reactions,
hydrogen fugacity was directly controlled in the experiments using a specially designed cell with Ar–H2 mixtures, in which hydrogen mole fraction, X(H2), ranged from 0 to 0.9. The addition of hydrogen to the watersaturated systems considered resulted in the appearance of a distinct temperature minimum on the solidus
curves within a hydrogen fugacity range of 300–500 bar, when the melting temperature decreased relative to
the water-saturated solidus by 22°C for albite (Ab), 30°C for albite with quartz (Ab–Qtz), and 40°C for the haplogranite (Ab–Or–Qtz) system. A further increase in hydrogen content in the mixtures raised the melting temperatures, which attained the maximum values under pure hydrogen pressure. The results of NMR and photoelectron spectroscopy of aluminosilicate and Na silicate glasses obtained under water and H2O–H2 pressure
suggested different mechanisms for the dissolution of water and water–hydrogen fluids in magmatic melts. In
contrast to pure water, hydrogen–water fluid produced distinct depolymerization of aluminosilicate melts,
which caused the decrease of their solidus temperatures. In order to estimate the influence of hydrogen on the
formation of granitic melts, determine the redox conditions of granite magmatism, and compare the results
obtained here with published data obtained using buffer reactions in the Fe–O system, the magnetite–wüstite
and iron–wüstite buffer equilibria were investigated under the same parameters. These equilibria are regarded
as indicators of reducing conditions in natural and experimental processes. The experiments showed that the
hydrogen fugacities attained in the presence of water at the oxygen fugacities imposed by the buffer reactions
MW and WT are sufficiently high for the occurrence of hydrogen–oxide reactions and formation of mixed compounds. As a result, the univariant buffer equilibria were transformed into divariant fields, and the stability of
magnetite, which is widespread in granites, expanded considerably to reducing conditions, up to f(H2) ≈
1100 bar at 700°C and 2 kbar total pressure.
INTRODUCTION
The idea that magma-generating zones in the Earth’s
crust and mantle may be reduced, especially during the
early stages of planetary evolution, has long been discussed in the literature (Letnikov et al., 1977; Haggerty
and Toft, 1985; Taylor and Green, 1989; Bezmen, 1992,
2001; Ballhaus, 1993; Kadik, 1997, 2004). This suggestion was supported by oxygen fugacity estimates for the
minerals of mantle nodules and igneous rocks, analyses
of gases released from the minerals of igneous complexes and MORB glasses, and investigations of the
composition of gases from submarine volcanic centers
(Welhan and Craig, 1979, 1983; Arculus et al., 1984;
Ballhaus and Stumpfl, 1985; Kadik et al., 1990; Charlou
et al., 2002). Thus, the available published data indicate
that reduced gases, e.g., CH4 and H2, must occur in fluidbearing magmas. Some authors (e.g., Slobodskoi, 1979;
Sobachenko and Zaboeva, 1994) presented evidence for
the formation of granite massifs and related pegmatites
under reducing conditions.
The interaction of silicate minerals and melts with
H2O–H2 fluids has been extensively studied (Nakamura, 1974; Luth and Boettcher, 1986; Bezmen et al.,
1990a, 1991; Schmidt et al., 1997; Bezmen, 2001;
Zavel’sky et al., 2003, 2004). Our previous comprehensive study of the NaAlSi3O8–H2O–H2 system focused
mainly on the solubility of fluid components and mechanisms of fluid–melt interaction (Bezmen et al., 1990a,
1990b, 1991; Bezmen, 1992; Zavel’sky and Bezmen,
1990). It was found that water solubility in albite melt
increases in the presence of hydrogen at 2 kbar and
1200°C (Bezmen et al., 1990a, 1991). A significant
increase in water solubility in the presence of hydrogen
compared with water-saturated melts was also detected
for Na-silicate (Na2O · 3SiO2) and haplogranite
(Ab32Or29Qtz29) melts at 950°C and 2 kbar water–
hydrogen fluid pressure (unpublished data). This
implies that the presence of hydrogen in magmatic fluid
must depress the melting temperatures of minerals and
rocks. However, Schmidt et al. (1997) reported experiments on the interaction between the haplogranite sys-
407
408
BEZMEN et al.
tem and H2O–H2 fluid performed using buffer equilibria and several discrete fluid compositions and did not
observe a decrease in solidus temperature in the presence of hydrogen.
In this connection, it is instructive to study melting
in the haplogranite system and its albite and albite–
quartz subsystems under hydrogen–water fluid pressure within a broader compositional range (from pure
water to pure hydrogen). Using these data we will
attempt to assess the role of hydrogen in the processes
of granite magma formation.
EXPERIMENTAL METHODS
Preparation of Starting Materials
Natural high albite from a rare metal pegmatite of
the Kalbinskii Range, Kazakhstan, and Ab59Qtz41 and
Ab32Or29Qtz29 (wt %) crystal mixtures were used as
starting materials. These mixtures are close to the
eutectic compositions at a water pressure of 1 kbar
(Tuttle and Bowen, 1958). The crystalline materials
were obtained by crystallizing glasses of appropriate
compositions. According to X-ray luminescence analysis performed by R. Seltmann at GeoForschungsZentrum (Potsdam, Germany), the albite contained (wt %)
67.71 SiO2, 0.005 TiO2, 19.73 Al2O3, 0.05 Fe2O3, 0.008
MnO, 0.01 MgO, 0.12 CaO, <0.005 Li2O, 11.25 Na2O,
0.14 K2O, 0.081 P2O5, 0.09 LOI, and 0.02 H2O, with a
total of 99.2. In order to purify the starting composition,
albite powder was recrystallized in 1 m NaCl solution
for 20 days at 700°C and 1 kbar in welded Pt ampoules
using a cold-seal hydrothermal pressure vessel. After
this treatment, the admixtures in the albite compositions were below the sensitivity levels of electron
microprobe analysis. The major-component composition of the albite is the following (wt %): 68.89 SiO2,
19.01 Al2O3, and 11.15 Na2O, which is close to the stoichiometric albite composition. The Al/Si distribution
was determined by the X-ray diffraction method and
showed that the recrystallized albite is represented by
an almost completely disordered structural modification.
Crystal charges of the Ab59Qtz41 composition were
prepared from gels, which were kindly provided by
F. Holtz and B. Schmidt. The gels were produced using
tetraethyl orthosilicate and aluminum and sodium
nitrates (Holtz et al., 1991). In accordance with the recommendations of Holtz et al. (1992), the gels were
fused at a temperature of 1300°C in Pt capsules in two
melting cycles, 4 h each, until a homogeneous glass
was obtained. The glasses were then recrystallized for
14 days under a water pressure of 1 kbar and 700°ë in
hydrothermal pressure vessels.
Alkali feldspar crystals with the Na0.48K0.52AlSi3O8
composition were used in the haplogranite melting
experiments. The alkali feldspar was prepared by crystallizing a glass synthesized at 1400°ë from ultra-pure
NaAlO2, K2CO3, and Al2O3 reagents in a high-temper-
ature vacuum set-up in two 20-min cycles. Similar to
the previous case, the glasses were crystallized for
3 days in hermetic Pt ampoules with 1 wt % water at
900°ë and a pressure of 1 kbar using a high-pressure
gas apparatus.
According to the results of X-ray analysis, the prepared compositions contained quartz and disordered
albite crystals in the first series and feldspar crystals
(0.01 to 0.1 mm in size) in the second series. The composition of the alkali feldspar crystals determined on an
electron microprobe, Na0.48 ± 0.02K0.52 ± 0.02AlSi3O8 (wt %),
was close to the target composition. Synthetic quartz
crystals, 0.08–0.1 mm in size, were added in experiments with the haplogranite composition (29 wt % of
the total charge).
Starting materials for the investigation of buffer
equilibria in the Fe–O–H2O system with magnetite
(Mt), wüstite (Wu), and metallic iron (Femet) were prepared from the high-purity reagents of ferrous oxide
(FeO) and carbonyl iron. Magnetite was synthesized by
oxidizing FeO with water at 950°ë and 2 kbar in
welded gold ampoules in a high-pressure gas vessel.
After a 24-h exposure under these parameters, X-ray
diffraction patterns showed no wüstite peaks.
A 0.08–0.10 mm fraction of Ab crystals or mixtures
of Ab (59 wt %) and Qtz (41 wt %) or Qtz (29 wt %) and
Ab52Or48 (71 wt %) crystals with a total weight of 5 mg
was loaded into a platinum capsule with a length of
20 mm, a diameter of 3 mm, and a wall thickness of
0.1 mm. Then, 31–50 mg of water were poured into the
ampoule in accordance with estimated P–V–T data. The
amount of water was chosen so that the ampoule
retained its initial shape. The ampoules were welded
and inserted into a molybdenum block, which was in
turn placed within the tungsten reactor of the hydrogen
cell (Fig. 1) of the internally heated high-pressure gas
vessel.
Argon–hydrogen mixtures of the desired composition were prepared in a special device and pumped into
the reactor under a total pressure of 100 atm (accuracy
of pressure determination was ± 0.4 atm for each gas).
The mass of hydrogen in the cell was approximately
200 times that of hydrogen in the reaction ampoule,
which provided a steady-state hydrogen potential even
in the experiments with low hydrogen mole fractions.
The mole fraction of hydrogen in the mixtures varied
from 0 to 0.9. The internal argon–hydrogen part of the
cell was separated from the outer pressure-transmitting
argon medium by a piston (Persikov and Epel’baum,
1978), which was located in the cold zone (Fig. 1).
Under a total pressure of 2 kbar, the uncertainties in the
experimental partial pressures of argon and hydrogen
could be as high as ±8 bar. Pressure in the high-pressure
gas vessel was measured by a Bourdon-tube gauge to
an accuracy of ±50 bar.
Temperature was measured using a Pt resistance
thermometer, whose coil was located in the molybdenum block near the ampoule along its whole length.
PETROLOGY
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MELTING OF ALKALI ALUMINOSILICATE SYSTEMS
Temperature measurements were pressure corrected
(Tarzimanov and Lozovoi, 1969), and the correction
varied from 3 to 4°ë within the experimental temperature range. The accuracy of temperature measurement
by the platinum resistance thermometer is ±0.1°ë. The
thermometer was calibrated against the points of water
boiling and silver melting (960.5°ë) at an argon pressure of 1 atm. The temperature gradient along the
ampoule was monitored by two independent heating
coils and measured by two Pt–PtRh thermocouples,
which were also located in the molybdenum block
(Fig. 1). The temperature gradient was no larger than
±1°ë per one centimeter of ampoule length at 1000°ë.
Overall, taking into account the temperature gradient
along the ampoule, the maximum error in temperature
measurement was no higher than ±2°ë.
dM ( H 2 )/dt
i 1/2
= 2πkl [ ( f ( H 2 )
e 1/2
e
i
– ( f ( H 2 ) ]/ ln ( r /r ),
solidus curve at T = 647°C, f( H 2 ) = 303 bar, and logk =
–10.28 mol H2/(cm s bar), this value is about an order
of magnitude lower, dM(H2)/dt = 0.39 mg/h. Under
such conditions, the equilibrium distribution of H2 in
the reactor and capsule is reached within several hours
at 805°C and within about 7 h at 647°C. Our experiments were always of much longer duration.
The experimental procedure was similar to that
described by Schmidt et al. (1997), when hydrogen
PETROLOGY
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2005
Piston
Thermocouples
Ar + H2
Ar
Ar
1
2
3
4
5
6
(1)
where k is the H2 permeability constant, l is the length
of the capsule (cm), r and ri are the external and interi
e
nal radii of the capsule (cm), and f( H 2 ) and f( H 2 ) are
the internal (in the capsule) and external (in the hydrogen cell) hydrogen fugacities. For the albite solidus
curve at the lowest experimental temperature of T =
e
805°C, f( H 2 ) = 278 bar, and logk = –9.64 mol H2/
(cm s bar) (Chou, 1986), the calculated rate of H2 permeation is dM(H2)/dt = 2.49 mg/h; for the haplogranite
e
Ar
Pt resistance
thermometer
Attainment of Equilibrium
Our method of hydrogen fugacity [f(H2)] control
under P–T melting conditions is based on H2 diffusion
through noble metals (usually, platinum), which are
used as experimental containers. In contrast to the
buffer method, in which hydrogen fugacity can take
discrete values during a limited time interval of buffer
assemblage operation, the use of a hydrogen cell allows
us to maintain any ç2/ç2é ratio in the experiment.
Since the permeation of hydrogen through the walls of
the tungsten reactor is negligible at high temperatures
(Bezmen, 1989), hydrogen fugacity can be kept constant
in experiments over practically infinite time periods.
The theoretical mass exchange of H2, M(H2) (in
grams), through the ampoule is calculated by the equation of Harvie et al. (1980):
409
Ar
Fig. 1. A sketch of a hydrogen cell of the high-pressure gas
apparatus. (1) Coil of the platinum resistance thermometer;
(2) ç2é-ç2 fluid within the reaction ampoule; (3) platinum
ampoule, 20 mm long, 3 mm diameter, and 0.1 mm wall
thickness; (4) experimental sample; (5) molybdenum block;
and (6) W or W–Re reactor.
fugacity is imposed by the external medium. In their
experiments, samples were initially held about 20°C
below the desired temperature for 5–17 h in order to
equalize hydrogen fugacity within the reactor and the
ampoule. Then temperature was raised to the desired
level and held for 2 h, which was sufficient for the
detection of the melting effect studied. Our procedure
differed in longer experimental durations: the first stage
of our experiments lasted for one day and the second
stage, 5–10 h. The experiments were quenched by shutting off the heater power, after which the temperature
410
BEZMEN et al.
Temperature, °ë
1100
Ptot = 2 kbar
1050
1000
950
900
Ab
850
Ab–Qtz
800
750
Ab–Or–Qtz
700
650
600
0
500
1000
1
2
3
1500
2000
2500
Hydrogen fugacity, f(H2), bar
Fig. 2. Solidus curves of the Ab, Ab–Qtz, and Ab–Or–Qtz
systems as functions of hydrogen fugacity in H2O–H2 gas
phase at a total pressure of 2 kbar. The experiments were
performed in the presence of excess gas phase. (1) Appearance of melt (liquid + crystals + vapor), (2) no melting
(crystals + vapor), and (3) extrapolation to X(ç2é) = 0.
decreased by 50°ë within 0.3 min and reached ambient
temperature within 20 min.
One of the most important criteria for the correctness of experiments was the presence of water in the
ampoules. The solidus temperature of vapor-saturated
melt at various H2O/H2 ratios in the fluid phase was
determined from the appearance of quenched liquids,
which occurred as a thin surface layer agglutinating the
crystals. This resulted in complete or partial (near the
solidus temperature) sintering of the charge. Microscopic examination revealed uniform glass distribution
along grain boundaries. In the experiments without
melting, the charge remained loose and disintegrated to
individual crystals.
In the experimental series on the investigation of
iron oxide equilibria, 30 mg of Fe3O4, FeO, or Femet
were loaded into a Pt container together with 30 ml of
water, which was sufficient to completely oxidize the
charge (even metallic iron) to magnetite. The container
was welded shut and inserted into the molybdenum
block of the hydrogen cell. The experiments were carried out at temperatures of 1200, 950, 850, and 700°ë
and a total pressure of 2 kbar. Temperature and temperature gradient were controlled in these experiments by
two thermocouples with an accuracy of ±7°ë. The first
experiments showed that already in the very beginning,
practically during the attainment of final experimental
conditions (20–30 min), the charge was completely
oxidized to magnetite and then gradually reduced to the
equilibrium state. Since it appeared to be senseless to
approach the equilibrium state from two sides, i.e., with
oxidized and reduced starting materials, the main criterion for the attainment of equilibrium was the constancy of phase proportions through time. The phase
composition and proportions in the experiments were
determined by the X-ray diffraction method. The proportions of phases did not change in experiments longer
than 2 h at 1200°ë, 24 h at 850°ë, and 48 h at 700°ë.
However, when possible, some experiments were
exposed over much longer time intervals. Electron
microprobe analysis showed that the concentration of
platinum in metallic iron from experiments was below
the analytical sensitivity (less than 0.1 wt %) within the
whole temperature interval.
EXPERIMENTAL RESULTS AND DISCUSSION
The results of aluminosilicate melting experiments
are shown in Tables 1–3 and Figs. 2 and 3. The tables
present the parameters that were directly controlled
during experiments: temperature and H2 mole fraction
in the Ar–H2 mixture, X(H2), and some calculated quantities: H2 activity coefficients in Ar–H2 mixtures for the
given temperature and H2 mole fraction, γ(H2); hydrogen fugacity in experiments, f(H2); and H2O mole fraction in the H2O–H2 fluid phase, X(H2O). According to
Shmulovich et al. (1980, 1982), the Ar–H2 system is
almost ideal: at 2 kbar the activity coefficients of hydrogen are γ(ç2 ) Ar–H2 < 1.09 within the whole range of
temperature and hydrogen mole fraction (Tables 1–3).
Therefore, hydrogen fugacity is the main fluid parameter directly controlled during the experiment. It can be
calculated rather accurately from the mole fraction of
hydrogen in argon–hydrogen mixtures:
f(H2) = γ(ç2 ) Ar–H2 · ϕ(ç2)P–T · X(ç2 ) Ar–H2 ,
(2)
where γ(ç2 ) Ar–H2 , ϕ(ç2)P–T, and X(ç2 ) Ar–H2 are the
coefficients of activity and fugacity and mole fraction
of hydrogen in the Ar–H2 mixture, respectively, at
2 kbar and experimental temperature. The activity coefficients of hydrogen in mixtures were calculated using
the equation of state of the Ar–H2 system (Shmulovich
et al., 1980, 1982). The fugacity coefficients of hydrogen under various pressures and temperatures are taken
from Mel’nik (1978).
During the experiment, hydrogen diffuses through
the wall of the platinum ampoule, and, after attainment
of equilibrium, hydrogen fugacity in the H2O–H2 system within the ampoule becomes equal to that in the
external Ar–H2 mixture. Because of the nonideal mixing of gases in the H2O–H2 system, the calculation of
other fluid parameters in this system, i.e., the activity
H O–H
and mole fraction of hydrogen, a(H2 ) 2 2 and
PETROLOGY
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MELTING OF ALKALI ALUMINOSILICATE SYSTEMS
411
Table 1. Experimental results on the melting of albite under a pressure of 2 kbar in the presence of water–hydrogen fluid
Run no.
T, °C
04
05
07
06
00
08
09
13
12
11
26
25
10
14
15
18
17
16
19
20
03
02
01
21
22
23
24
27
&
840
835
834.5
830
820
822
819
814
810
805
811
809
822
817
812
850
845
835
926
918
910
894
870
995
985
983
1051
1045
1086
Ar–H2
H2O–H2
X(H2)
γ(H2)
f(H2), bar
X(H2O)
~0
~0
~0
~0
~0
0.1
0.1
0.1
0.1
0.1
0.15
0.15
0.2
0.2
0.2
0.3
0.3
0.3
0.5
0.5
0.5
0.5
0.5
0.7
0.7
0.7
0.9
0.9
1.0
~1
~1
~1
~1
~1
1.058
1.059
1.059
1.060
1.060
1.055
1.055
1.049
1.049
1.050
1.038
1.039
1.039
1.021
1.021
1.021
1.022
1.023
1.009
1.010
1.010
1.002
1.002
1.000
~0
~0
~0
~0
~0
291
292
292
293
294
437
438
578
579
580
847
850
853
1352
1355
1359
1369
1381
1830
1837
1838
2300
2304
2527
1.00
1.00
1.00
1.00
1.00
0.952
0.952
0.952
0.952
0.952
0.923
0.924
0.891
0.892
0.893
0.809
0.811
0.813
0.602
0.603
0.604
0.606
0.612
0.370
0.370
0.370
0.153
0.153
0
Melt
appearance
+
+
+
–
–
+
+
+
–
–
+
–
+
+
–
+
–
–
+
+
–
–
–
+
+
–
+
–
+
Note: + denotes melt appearance; –, no melting; &, extrapolated data.
X(ç2 )
H 2 O–H 2
; the activity and mole fraction of water,
H 2 O–H 2
H 2 O–H 2
a(ç2é )
and X(ç2é )
; and oxygen fugacity, f(O2), is accompanied by large uncertainties. This
fact is related to different theoretical approaches proposed by various authors for the description of nonideality (Redlich and Kwong, 1949; Shaw, 1963; Shmulovich et al., 1980, 1982; Holloway, 1981; Grevel and
Chatterjee, 1992). In this study, we used the equation of
state of the ç2é–ç2 system and algorithms for the calculation of water and hydrogen mole fractions proposed by Shmulovich et al. (1980, 1982). The results
are shown in Fig. 3.
The determination of fluid characteristics in the
ç2é–ç2 system raises major difficulties related to the
PETROLOGY
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No. 5
2005
use of results obtained by various authors for buffer
assemblages ignoring the effect of hydrogen.
Solidus Temperatures under 2 kbar Water Pressure
Experiments under pure water pressure were conducted using pure argon in the reactor. Ignoring the
nonideal behavior of the ç2é–ç2 system, water dissociation occurs in the hermetic capsule during the experiment via the reaction
2ç2é = 2ç2 + é2; Kp = [X(H2)2 · X(O2)]/X(ç2é)2, (3)
which yields
1/2
X(ç2é) = K r /[X(H2) · X(O2)1/2],
(4)
412
BEZMEN et al.
Table 2. Experimental results on the melting of Ab–Qtz eutectic point under a pressure of 2 kbar in the presence of water–
hydrogen fluid
Run no.
T, °C
28
29
31
30
27
32
33
34
44
43
41
50
49
35
36
37
42
45
46
48
47
47a
53
54
55
56
60
59
58
57
&
750
745
743.5
742
740
743.5
734
724
715
711
700
717
715
740
730
720
755
751
748
825
820
815
920
910
905
900
980
975
970
965
1017
Ar–H2
H2O–H2
X(H2)
γ(H2)
f(H2), bar
X(H2O)
~0
~0
~0
~0
~0
0.1
0.1
0.1
0.1
0.1
0.1
0.125
0.125
0.2
0.2
0.2
0.3
0.3
0.3
0.5
0.5
0.5
0.7
0.7
0.7
0.7
0.9
0.9
0.9
0.9
1.0
~1
~1
~1
~1
~1
1.068
1.070
1.071
1.073
1.073
1.075
1.069
1.070
1.058
1.059
1.060
1.046
1.047
1.047
1.025
1.025
1.026
1.011
1.011
1.011
1.011
1.002
1.003
1.003
1.003
1.000
~0
~0
~0
~0
~0
304
306
308
310
310
312
385
386
603
607
610
888
890
892
1408
1411
1415
1877
1884
1887
1890
2349
2353
2357
2360
2574
1.0
1.0
1.0
1.0
1.0
0.955
0.955
0.955
0.956
0.956
0.957
0.950
0.951
0.907
0.909
0.911
0.838
0.840
0.841
0.629
0.631
0.633
0.377
0.379
0.380
0.381
0.154
0.155
0.155
0.155
0
Melt
appearance
+
+
+
–
–
+
+
+
+
–
–
+
–
+
+
–
+
+
–
+
+
–
+
–
–
–
+
–
–
–
+
Note: + denotes melt appearance; –, no melting; &, extrapolated data.
where Kr is the equilibrium constant; and X(H2), X(O2),
and X(ç2é) are the mole fractions of hydrogen, oxygen, and water, respectively. If a certain amount of
hydrogen is initially produced by the water dissociation
reaction (Eq. 3), it begins to diffuse through the walls of
the Pt ampoule into the external Ar medium. As a result,
the amount of hydrogen in the ampoule declines, while
the mole fraction of water increases and approaches
unity in accordance with Eq. 4. The process is inhibited
when a significant decrease in hydrogen fugacity
strongly depresses the rate of its permeation according
to Eq. 1. The fluid generated in such a way within the
ampoule is composed of almost pure water with very
small amounts of oxygen and hydrogen, the total fugacity of which is much lower than 1 bar.
The results obtained for the water-saturated solidi of
the systems studied at a pressure of 2 kbar are compared with published data in Table 4. It can be seen that
the solidus temperatures obtained in this study (832 ±
2°ë for albite, 743 ± 2°ë for the albite–quartz eutectic,
and 682 ± 2°ë for the haplogranite albite–orthoclase–
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2005
MELTING OF ALKALI ALUMINOSILICATE SYSTEMS
413
Table 3. Experimental results on the melting of Ab–Or–Qtz eutectic point at varying hydrogen content in water–hydrogen
fluid and a total pressure of 2 kbar
Run no.
T, °C
61
62
63
64
71
66
65
72
70
73
78
79
80
83
82
81
67
68
76
69
77
84
85
86
87
91
90
89
88
&
685
680
665
655
655
650
645
645
640
635
660
655
645
690
680
670
765
755
755
745
745
850
840
830
820
930
920
910
900
975
Ar–H2
H2O–H2
X(H2)
γ(H2)
f(H2), bar
X(H2O)
~0
~0
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.1
0.2
0.2
0.2
0.3
0.3
0.3
0.5
0.5
0.5
0.5
0.5
0.7
0.7
0.7
0.7
0.9
0.9
0.9
0.9
1.0
–
–
1.081
1.083
1.083
1.084
1.085
1.085
1.086
1.087
1.069
1.070
1.071
1.053
1.054
1.056
1.028
1.029
1.029
1.030
1.030
1.013
1.013
1.013
1.013
1.002
1.003
1.003
1.003
1.000
~0
~0
320
323
323
324
325
325
326
327
635
637
642
923
929
936
1448
1456
1456
1464
1464
1928
1936
1944
1952
2384
2394
2403
2411
2607
1.0
1.0
0.964
0.966
0.966
0.968
0.969
0.969
0.971
0.972
0.921
0.922
0.923
0.863
0.867
0.871
0.662
0.669
0.669
0.677
0.677
0.393
0.395
0.398
0.402
0.160
0.160
0.160
0.160
0
Melt
appearance
+
–
+
+
+
+
+
+
–
–
+
+
–
+
+
–
+
+
+
–
–
+
–
–
–
+
–
–
–
+
Note: + denotes melt appearance; –, no melting; &, extrapolated data.
quartz system) are identical to the published data within
the experimental uncertainties.
Solidus Temperatures as Functions
of the Composition of H2O–H2 Fluid
Let us examine in more detail the curves shown in
Fig. 2. It can be seen that the systems studied show similar behaviors of solidus curves as functions of hydrogen content in the fluid phase. The addition of small
amounts of hydrogen to water fluid depresses the solidus temperatures, which attain minimum values at
f(ç2) ≈ 300–400 bar. A further increase in hydrogen
PETROLOGY
Vol. 13
No. 5
2005
content raises the solidus temperatures, and the maximum values are reached under pure hydrogen pressure.
Relative to the ç2é-saturated solidus, the maximum
temperature depression was 22°ë for albite, 30°C for
the albite-quartz mixture, and 40°C for the albite–
orthoclase–quartz composition. The behavior of the
ç2é–ç2 system is nonideal within the experimental
pressure–temperature range. The experimental hydrogen fugacity values (Fig. 2) were recalculated to the
mole fractions of water taking into account the nonideal
behavior of the ç2é–ç2 system and using the algorithm proposed by Kalinichev and collaborators
414
BEZMEN et al.
can be concluded that minima on melting curves are
attained at small hydrogen contents in the fluid phase.
Temperature, °ë
1100
Melting temperatures under pure hydrogen pressure
were determined by extrapolating the solidus curves to
water-free compositions (Fig. 3). The melting temperature of albite under 2 kbar hydrogen pressure is approximately 1086°ë, which is 32°ë lower than the melting
point of dry albite at 2 kbar (Bohlen et al., 1982). Our
data are in good agreement with the results of Persikov
et al. (1986), who reported a melting temperature of
1082°ë for the Ab–ç2 system under 2 kbar hydrogen
pressure. The solidus temperatures of the Ab–Qtz and
Ab–Or–Qtz eutectics under pure hydrogen pressure are
1017 and 975°ë, respectively.
Ptot = 2 kbar
1000
Ab
Ab–Qtz
900
800
Ab–Or–Qtz
Mechanisms of H2O–H2 Fluid Dissolution
in Aluminosilicate Melts
700
1
2
3
600
1.0
0.8
0.6
0.4
0.2
0
Molar fraction of water in fluid, X(H2O)
Fig. 3. Position of minima on the melting curves of the Ab,
Ab–Qtz, and Ab–Or–Qtz systems as functions of the mole
fraction of water in fluid calculated accounting for the nonideality of the H2O–H2 system (Shmulovich et al., 1980,
1982). (1) Appearance of melt; (2) no melting; and
(3) extrapolation to X(ç2é) = 0.
Numerous experimental studies of water interaction
with aluminosilicate melts at various temperatures,
pressures, and compositions revealed high water solubility. Water dissolution causes considerable changes in
the physical properties of melts, including viscosity,
diffusion mobility of components, conductivity, etc.,
which is explained by melt depolymerization. Zharikov
(1969) evaluated published experimental data on isothermal water solubility in magmatic melts and proposed a mechanism for the interaction of water with
aluminosilicate melts, which can be described by the
reaction between water molecules and oxygen ions
with the formation of hydroxyl groups:
2–
(Shmulovich et al., 1980, 1982). The following values
were obtained for the minima on solidus curves:
X(ç2é) = 0.92 for Ab, X(ç2é) = 0.96 for Ab–Qtz, and
X(ç2é) = 0.97 for the haplogranite system (Fig. 3). It
–
ç2éfluid + OH melt = 2 OH melt .
(5)
In melts containing both silicon–oxygen tetrahedra
and cation groups, a water molecule breaks an M–O
bond (where M is the divalent cation) to produce
Table 4. Comparison of the solidus temperatures reported by various authors for the systems studied at a water pressure of
2 kbar
System
Solidus temperature, °C,
this study
Solidus temperature, °C,
published data
Reference
Ab–H2O
832 ± 2
840 ± 10
834
818 ± 10
(Goranson, 1938)
(Johannes, Holtz, 1996)
(Goldsmith, Jenkins, 1985)
Ab–Qtz–H2O
743 ± 2
740 ± 3
(Holtz et al., 1992)
Ab–Or–Qtz–H2O
682 ± 2
680–690 (1961 bar)
(Tuttle, Bowen, 1958)
685
(Tuttle, Bowen, 1958)
685
(Holtz et al., 1992)
670–680
(Keppler, 1989)
680
(Ebadi, Johannes, 1991)
680–690
(Schmidt et al., 1997)
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MELTING OF ALKALI ALUMINOSILICATE SYSTEMS
M−OH and Si–OH groups, which can be described by
the general reaction
ån[SiO3]n + mH2O = ån[SinO3n – m] · [OH]2m. (6)
Zharikov (1969) suggested that water can dissolve
in silicate melts, especially at high pressures, not only
in the dissociated form but also as molecules. Water
molecules form hydrous shells around ions or occur in
water complexes, distribute in the free volume of melt,
and are connected by hydrogen or coordination bonds
to various structural groups in melt.
Burnham (1975, 1979) proposed a model for water–
melt interaction, which can also be described in a general form by reaction (5). Burnham used P–V–T data
for the albite–water system and supposed that water
interacted with the bridging oxygen of AlO4 and SiO4
tetrahedra. According to this model, ç+ of water forms
a bond with tetrahedral Al rather than with Na+, while
éç– groups of water break the bridging Si–O–Si bonds
of tetrahedra producing Si–OH and Si–é– structural
groups. The charge of the latter is compensated by Na+.
The reaction of water dissolution in albite melt at H2O
concentrations of up to 50 mol % is described by the
following reaction:
(7)
NaAlSi3O8 + ç2é = HAlSi3O7(OH)(NaO),
whereas at H2O concentrations higher than 50 mol %,
the breakage of Si–O–Si bonds produces Si–OH groups
only:
HAlSi3O7(OH)(NaO) + ç2é = HAlSi3O6(OH)3(ONa),
(8)
etc.
This model ignored the presence of molecular water
in melts. In subsequent studies, various authors
detected both éç– groups and molecular water in
quenched hydrous glasses and directly in melts by IR,
Raman, and NMR spectroscopy and other physical
methods.
The main body of data on the speciation of water in
aluminosilicate glasses has been obtained by the IR
spectroscopy of quenched hydrous glasses in the near
infrared range (Stolper, 1982a, 1982b; Silver and
Stolper, 1989; Silver et al., 1990). NMR studies of 1ç,
23Na, 27Al, 29Si, and 17O nuclei focused on the determination of the structure of fluid-bearing glasses depending on their composition and water content (Bartholomew and Schreuer, 1980; Farnan et al., 1987; Eckert
et al., 1988; Kohn et al., 1989, 1992; Zavel’sky and
Bezmen, 1990; Zavel’sky et al., 1998, 1999, 2000; Holland, 1999; Zeng et al., 1999, 2000; Zavel’sky and
Salova, 2001; Schmidt et al., 2001a, 2001b; Liu et al.,
2002; etc.). Some authors reported the results of investigations of glasses synthesized under the pressure of
water–hydrogen and hydrogen fluid (Bezmen et al.,
1990a, 1990b, 1991; Bezmen, 1992; Zavel’sky et al.,
2003, 2004).
IR spectroscopic studies demonstrated that water
dissolves in aluminosilicate melts as OH groups and
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415
H2O molecules. At low concentrations (up to 1 wt %),
water in glasses occurs mainly as hydroxyl groups.
With increasing water content in quenched aluminosilicate glasses, the fraction of molecular water increases
and becomes comparable with that of OH groups at
approximately 4 wt % ç2é. However, in situ IR spectroscopy of aluminosilicate melts revealed that the fraction of dissociated water increased considerably with
increasing temperature (Nowak and Behrens, 1995;
Shen and Keppler, 1995; Withers et al., 1999; Sowerby
and Keppler, 1999) and became much higher than in
quenched glasses. Nonetheless, because of methodic
difficulties, the investigation of quenched glasses
remains to be the main source of information on the
mechanism of fluid–melt interaction.
Taking into account the results of IR spectroscopy
of quenched hydrous glasses, Stolper (1982a) proposed
a mechanism of water dissolution in aluminosilicate
melt involving two reactions:
(9)
H2Ofluid = H2Omelt
and
H2Omelt + 2O– = 2OH–melt.
(10)
A more informative method for the investigation of
fluid-bearing glasses is nuclear magnetic resonance
(NMR), which provides evidence on both water speciation in melts and the nature of interaction between
water and nuclei of Si, Al, Na, and other elements.
NMR spectroscopic studies have demonstrated that
water dissolves in quartz melt as OH groups only, forming Si–OH groups (Zavel’sky et al., 1999).
The NMR spectroscopy of more complex anhydrous Na-silicate glasses (Na2O · nSiO2; n = 3, 4) suggested that 23Na+ occurs in two positions with strongly
different symmetries of electron surrounding. Part of
Na+ ions are implanted into the quartz matrix breaking
bridging Si–O–Si bonds and forming Si–O–Na groups.
Other Na+ ions form an interstitial solid solution with
quartz and sit in holes formed by bridging oxygen
atoms with unshared electron pairs (Zavel’sky and
Salova, 2001; Zavel’sky et al., 2004). By the example
of an NMR study of Na silicate glasses with varying
water content, Zavel’sky and Salova (2001) inferred
that water dissolution is accompanied by ç+ substitution for Na+ in Si–O–Na fragments and expelling of
Na+ into oxygen holes, which serve as coordination
centers for water molecules in Na-silicate glasses.
At least three chemically different states of proton
were detected by NMR spectroscopy in quenched H2Osaturated albite glasses (Zavel’sky et al., 1998). One of
them is reliably identified as protons of isolated water
molecules represented by a Pake doublet in the spectra
(Fig. 4, lower spectrum). The second type of protons is
associated with a central spectral line, whose halfheight width varies depending on the water content in
glass from 10 to 13 kHz. This signal is related to OH
groups at H2O concentrations of up to ~50 mol %. At
higher water contents, the central singlet narrows
416
BEZMEN et al.
ters for water molecules and form additional ion-dipole
pairs with them. As a result, noninteracting (isolated)
water molecules appear in albite glasses. They are manifested in spectra by Pake doublets (Fig. 4). Water clusters
are formed at high water contents (above ~50 mol %).
They are probably also localized around sodium ions
forming solvated species (Zavel’sky and Salova, 2001).
H2
OH
Ab0.933(H2)0.067
Ab0.778(H2O)0.057(H2)0.165
H2O
Ab0.525(H2O)0.327(H2)0.148
Ab0.385(H2O)0.566(H2)0.040
Ab0.495(H2O)0.505
–20
0
20
kHz
Fig. 4. 1H static NMR spectra of albite glasses synthesized
in the presence of H2O–H2 fluid at 1200°ë and 2 kbar. The
compositions of glasses are given in mole fractions. The
methods of synthesis, analysis, and NMR spectroscopy of
glasses were described by Bezmen et al. (1990a, 1990b,
1991).
abruptly when temperature increases above ~300 K
(Zavel’sky and Bezmen, 1990). The abrupt (threshold)
narrowing of the central line can be explained by supposing the existence of a third type of protons in glasses
with high contents of dissolved water (Zavel’sky and
Bezmen, 1990; Zavel’sky et al., 1998, 2004): small
(~10 molecules) water clusters, in which water molecules are connected by hydrogen bonds. At a certain
temperature (~300 K for albite), the hydrogen bonds in
clusters undergo thermally activated breaking and
water molecules acquire additional mechanical degrees
of freedom, which causes an extensive line narrowing
at a constant integral intensity. An abrupt narrowing of
the central line was also observed in the proton magnetic resonance (1H NMR) spectra of hydrous sodium
silicate glasses (Na2O · 3SiO2) at a higher temperature
of ~345 K (Zavel’sky and Salova, 2001). Thus, according to the NMR data, ç2é-saturated albite glasses contain OH groups and isolated water molecules. The Na+
ions sitting in oxygen holes serve as coordination cen-
The formation of Si–OH and Al–OH bonds in
hydrous aluminosilicate glasses has been vigorously
debated in recent years. This question has a direct bearing on the problem of depolymerization of hydrous
magmatic melts. Changes in many physical parameters
of magmatic melts in response to water dissolution,
including viscosity (Johannes and Holtz, 1996), density
(Epel’baum, 1980), diffusion mobility of species
(Chekhmir et al., 1991), melting temperatures, and others, are explained by depolymerization. However, 27Al
and 29Si magic angle spinning (MAS) NMR spectra do
not exhibit significant isotropic chemical shifts of these
elements in aluminosilicate glasses, which casts doubt
on the formation of Si Q3–OH and Al Q3–OH bonds
(Kohn et al., 1989; Schmidt et al., 2001b; Padro et al.,
2003). The symbol Qi usually denotes the remaining
oxygen bonds in silicon–oxygen tetrahedra. According
to Schmidt (2001b), changes in quadrupole coupling
constants with increasing water content in melts also
suggest the absence of significant amounts of 29Si–OH
and 27Al–OH groups. In contrast to 27Al and 29Si, the
isotropic chemical shift of 23Na changes dramatically
with increasing water content in aluminosilicate
glasses. Since the isotropic chemical shift of 23Na correlates with the content of molecular water in glasses, it
is supposed that a hydrate shell is formed around Na
atoms and the Na–O distance decreases compared with
the structure of anhydrous aluminosilicate glasses
(Schmidt et al., 2001b). Thus, the structural features of
hydrous glasses obtained by the analysis of NMR spectra suggest that aluminosilicate melts do not undergo
extensive depolymerization under the influence of
water fluid. Taking into account these observations,
Kohn et al. (1989, 1992) and Schmidt et al. (2000,
2001b) proposed a mechanism for water dissolution in
silicate melts involving formation of Si–OH–Al bridging groups, where the cation charge is compensated at
the expense of proton exchange. However, NMR spectroscopy cannot unambiguously demonstrate the complete absence of 29Si–OH and 27Al–OH groups because
of the considerable width of 29Si and 27Al signals in
MAS NMR spectra. Furthermore, quenching processes
could be accompanied by extensive changes in the
structural characteristics of melts, which was shown by
in situ IR spectroscopic studies of melts under water
pressure (e.g., Nowak and Behrens, 1995).
Taking into account the structural characteristics of
ç2é-saturated aluminosilicate glasses determined by
NMR studies, including the formation of Na(OH) complexes, the presence of molecular water, and the
absence of Si–OH and Al–OH bonds, the mechanism of
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MELTING OF ALKALI ALUMINOSILICATE SYSTEMS
water dissolution in albite melt can be described by the
reaction (Johannes and Holtz, 1996; Kohn, 2000)
NaAlSi3O8 + ç2é = HAlSi3O8 + Na(OH).
Vol. 13
No. 5
2005
(H+ in molecular water)/(H+ in OH groups), wt %
5
(11)
The NMR spectra of hydrogen-bearing albite
glasses are not fundamentally different from those of
water-saturated glasses. Figure 4 shows typical 1H
static NMR spectra of quenched albite glasses with various water and hydrogen contents obtained at 1200°ë
and a total pressure of 2 kbar within a wide range of
fluid phase composition, from pure water to pure
hydrogen. The methods of synthesis of fluid-bearing
albite glasses and their NMR investigation were
described by Bezmen et al. (1990a, 1990b, 1991).
Their spectra consist of a Pake doublet due to isolated
water molecules and a central line attributed to OH
groups (Fig. 4). In addition, the spectra display a narrower line with a half-height width of 1.5 kHz at high
hydrogen content. This line was tentatively ascribed by
us to magnetically diluted OH groups (Bezmen et al.,
1991) connected by weaker bonds to other elements
(Na, Al, and Si). However, a more detailed NMR study
of hydrous Na-silicate glasses allowed us to identify
this line as a signal of molecular hydrogen, which is
localized, similar to water, in holes formed by oxygen
atoms (Zavel’sky et al., 2003).
On the other hand, despite the similarity in the speciation of dissolved fluid components, there are significant differences in the proportions of dissociated and
molecular species in hydrogen-bearing and water-bearing quenched albite glasses depending on fluid composition (ç2é/ç2 ratio). The relative amounts of OH
groups and molecular water in quenched hydrous albite
glasses show distinct correlations with the bulk water
content (Stolper, 1982a, 1982b; Silver and Stolper,
1989; Silver et al., 1990). In the 1H NMR spectra of
quenched albite glasses containing no more than
~50 mol % of bulk water, the integral intensities of the
central singlet and doublet are proportional to the contents of protons from OH groups and molecular water
and can be used for the calculation of proportions of
protons associating with various dissolved species
(Eckert, 1988; Bezmen, 1992; Riemer et al., 2000;
Schmidt et al., 2001a; Liu et al., 2002). High-resolution spectra collected at low temperatures are most suitable for this purpose. At high water content (more than
~50 mol %), an additional component related to water
clusters contributes to some extent to the central line of
the spectrum. The signal of this component is added to
the singlet of OH groups (Zavel’sky and Bezmen,
1990). The integral intensities of the singlet and doublet
(peak areas) of the 1H NMR spectra of ç2é-saturated
and H2O–H2-bearing quenched albite glasses were
determined by numerical integration after the deconvolution of the spectra with an accuracy of ~10%, which
was estimated by the repeated analysis of samples.
Spectra of ç2é-saturated and hydrogen-bearing albite
glasses with previously determined water and hydrogen
contents collected at 150 K were used for calculations
PETROLOGY
417
4
1
2
3
3
X(H2) = ~0
2
1
X(H2) = 0.7
X(H2) = ~1
0
0.2
X(H2) = 0.4
X(H2) = 0.1
0.4
0.6
0.8
1.0
1.2
Total content of H+ in glass, wt %
Fig. 5. Influence of hydrogen on the proportions of molecular water and OH groups in H2O–H2-bearing albite glasses
depending on the bulk content of fluid. The curves were
obtained by recalculation of the data of IR spectrometry and
analysis of 1H static NMR spectra to the contents of protons
in molecular water and OH groups. (1) Recalculation of IR
spectroscopic data (Silver and Stolper, 1989) to the contents
of protons in molecular water and OH groups in H2O-saturated albite glasses; (2) data of 1H NMR spectroscopy of
H2O-saturated albite glasses synthesized at T = 1200°C and
P H O = 0.5–5.0 kbar (Zavel’sky and Bezmen, 1990);
2
(3) data of 1H NMR spectroscopy of ç2-bearing albite
glasses synthesized at T = 1200°ë and Ptot = 2 kbar (Bezmen et al., 1990).
(Zavel’sky and Bezmen, 1990; Bezmen et al., 1990a,
1991). The 1H NMR data on the speciation of fluid
components were compared with the results of IR spectroscopy (Silver and Stolper, 1989) recalculated to the
proportions of protons of OH groups and molecular
water in quenched albite glasses as functions of the
bulk concentration of ç+ (wt %) in water. As can be
seen in Fig. 5, the ratio of OH group protons to molecular water protons obtained by the analysis of 1H NMR
spectra of ç2é-saturated albite glasses are practically
identical to those calculated from IR spectra.
In hydrogen-bearing albite glasses, the dissociated
water species are much more abundant than in ç2ésaturated glasses; moreover, the ratio of OH groups to
molecular water in hydrogen-bearing glasses is weakly
dependent on the bulk concentration of fluid (Fig. 5).
Kadik et al. (2004) observed a strong predominance of
OH groups over molecular water in the IR spectra of a
ferrobasalt glass synthesized at 3.7 GPa pressure of ç2bearing fluid and 1520–1600°ë. It should be noted that
these authors analyzed quenched fluid-bearing glasses.
The melts could be characterized by other proportions
of dissociated and molecular water species (Nowak and
Behrens, 1995; etc.), but these data suggest a similarity
in the speciation of dissolved water and water–hydro-
418
BEZMEN et al.
537 532 527 121 117 103 99
32 28 24 20 16 12 8
(‡)
4 eV
(b)
1
1
2
2
3
3
4
4
O1s
Al2s
Si2p
Na2p
O2s
Fig. 6. Photoelectron spectra of fluid-bearing glasses of the Ab–H2O–H2 system: (a) é1s, Al2s, and Si2p; (b) Na2p and O2s. Compositions of glasses (molar fractions): (1) Ab, (2) Ab0.712(H2O)0.288, (3) Ab0.605(H2O)0.231(H2)0.164, and (4) Ab0.933(H2)0.067.
The spectra are discussed in the text and by Bezmen et al. (1990b, 1991).
gen fluid components in glasses and melts, although the
mechanisms of their interaction with aluminosilicate
melts may be different.
These differences are very pronounced in X-ray
photoelectron spectra (Bezmen et al., 1990b, 1991).
Figure 6 shows photoelectron spectra of glasses
obtained under fluid-absent conditions and in the presence of water, water–hydrogen, and hydrogen fluid.
These spectra were described in detail by Bezmen et al.
(1990b), and we point out here only some important
characteristics of spectra of hydrogen-bearing glasses:
strong shift of maxima on the Si2p and Al2s spectra,
appearance in the é1s spectra of an additional peak of
unknown nature at 536.5 eV and, especially important,
an additional peak at 99 eV corresponding to Si0. In the
valence band spectra (Fig. 6b), the é2s line is characterized by a more complex structure: the spectra of
fluid-bearing glasses show two additional weak peaks
on the high-energy shoulder, which can be attributed to
Si–OH and Al–OH bonds. The latter components are
more clearly manifested in hydrogen-bearing glasses
(Fig. 6b).
The presence of hydrogen in the fluid phase results
in the development of reducing processes in the melts,
which, according to the data of NMR and X-ray photoelectron spectroscopy, are obviously coupled with aluminosilicate melt depolymerization. This is recorded in
a significant shift of the Si2p and Al2s peaks, appearance of additional peaks in the valence region of é1s
and é2s electrons, and formation of zero-valent silicon
detected in the photoelectron spectra (Fig. 6). The
H2O/OH ratio in the 1H NMR spectra of ç2-bearing
glasses is low compared with glasses obtained under
pure water pressure (Fig. 5). In addition, the 29Si static
NMR spectra of ç2-bearing albite glasses exhibit an
isotropic chemical shift of approximately 7 ppm relative to the spectra of ç2é-saturated albite glasses (Bezmen, 1992). The mechanism of dissolution of H2O–H2
fluid accounting for the reduction of silicon to the zerovalent state was discussed by Bezmen et al. (1990b).
However, zero-valent silicon (Si0) is probably thermodynamically unstable in magmatic melts, and Si can occur
in a transitional valence state, between Si4 and Si0.
Among possible variants is the formation of é–Si=Si–é
bonds, whereas Si0 could be formed during quenching.
On the whole, investigations using various physical
methods suggest that water and water–hydrogen fluid
are dissolved in magmatic melts through different
mechanisms, and hydrogen causes stronger depolymerization of aluminosilicate liquids, which results in an
increase in water solubility and corresponding depression of solidus temperatures (Figs. 2, 3).
Comparison with Published Data
Nakamura (1974) studied the SiO2–H2O–H2 system
at a total pressure of 15 kbar and hydrogen fugacity
controlled by the IW buffer reaction. He demonstrated
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MELTING OF ALKALI ALUMINOSILICATE SYSTEMS
that the presence of hydrogen shifts the critical point to
pressures higher than 15 kbar. Luth and Boettcher
(1986) determined the fluid-saturated solidus of the low
albite–H2O–H2 system at pressures of 5–17 kbar. They
used pure water, HM, NNO, and IW buffer systems to
control f(H2). Unfortunately, the buffer method used by
these authors did not allow constraining the solidus
near the minimum melting temperature (relative to
H2O-saturated conditions), i.e., at X(H2é) = 0.92–0.97
(Fig. 3).
Temperature, °ë
820
Schmidt et al. (1997) determined the solidus temperatures of the haplogranite system (Ab32Or29Qtz39–
H2O–H2). The experiments were carried out at 1, 2, and
5 kbar pressure with pure water and in the presence of
hydrogen. Hydrogen fugacity was controlled by diffusion through an Ag40Pd60 membrane at low values (up
to 55 bar) (Scaillet et al., 1992) and Co–CoO (CCO),
MW, and IW buffer assemblages at f (H2) > 55 bar. In
experiments with the MW and IW buffer assemblages,
hydrogen was added into the high-pressure gas vessel
( P H2 = 50 bar). These authors also studied melting temperatures of compositions close to the eutectics of the
Ab58Qtz42–H2O–H2 and Or58Qtz42–H2O–H2 subsystems
at 1 and 5 kbar and low hydrogen fugacities, f(H2) =
0.03–55 bar, controlled by a modified membrane technique (Shaw, 1963; Scaillet et al., 1992). The results of
the investigation of the Ab–Qtz–H2O–H2 system at
1 kbar and the Ab–Or–Qtz system at 2 kbar are shown
in Fig. 7. It can be seen that within the range of f(H2)
values appropriate for the use of the membrane method,
hydrogen has a negligible effect on the solidus temperatures. This could be related to the accuracy of the
experimental data. Considerable differences between
our data and the results reported by Schmidt et al.
(1997) were observed for the haplogranite system at
high hydrogen fugacities (Fig. 8) (we used the same
composition for the investigation of this system:
Ab32Or29Qtz39–H2O–H2). Our data for melting under
pure water pressure are essentially identical to those of
Schmidt et al. (1997): 682 ± 2 and 685 ± 5°C, respectively. At low hydrogen fugacities (up to 54 bar), the
solidus temperature are not affected by the presence of
hydrogen (Fig. 7, 8), which is consistent with our data.
Considerable discrepancies were observed at hydrogen
fugacities controlled by the IW and, especially, WM
buffer assemblages (Fig. 8).
740
Divariant Character of Buffer Reactions
in the Presence of Water–Hydrogen Fluid
In water-bearing systems, hydrogen fugacity is usually calculated from the value of oxygen fugacity controlled by a solid-state buffer assemblage ignoring
interactions between buffer phases and hydrogen.
Moreover, f(O2) values of buffer reactions reported by
different authors are often used as reference points.
Figure 8 shows the results of calculations for buffer
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2005
419
800
Ptot = 1 kbar
Ab–Qtz
780
760
crystals + liquid + vapor
crystals + vapor
720
700
Ptot = 2 kbar
Ab–Or–Qtz
680
660
0
10
20
30
40
50
60
70
80
Hydrogen fugacity, f(H2), bar
Fig. 7. Experimental data by Schmidt et al. (1997) on the
Ab–Qtz solidus at 1 kbar and Ab–Or–Qtz solidus at 2 kbar
in the presence of H2O–H2 fluid at low hydrogen fugacities
controlled by a modernized membrane method (Shaw,
1963; Scaillet et al., 1992).
reactions at 2 kbar according to the data by Jacobsson
1
and Rosen (1981) and Jacobsson (1985): MW i , and
1
WI i ; and O’Neill (1988) and O’Neill and Pownceby
2
2
(1993): MW i and WI i . Schmidt et al. (1997) used the
latter data with a pressure correction for 2 kbar according to Chou (1987). The calculations were performed
assuming ideal mixing of real gases (Lewis–Randall
rule). It is known that the ç2é–ç2 system is not ideal
under the experimental conditions.
In order to clarify the reason for the discrepancy
between our data and the results of Schmidt et al.
(1997), we undertook an investigation of the MW and
IW buffer reactions exposed to hydrogen–water fluid
pressure. The results are presented in Table 5 and Fig. 8.
The Fe–O system becomes ternary in the presence
of water. In addition to oxygen, it contains water and
hydrogen. The proportions of gases in this system may
vary depending on physicochemical conditions. The
amount of hydrogen increases with decreasing f(é2).
Under MW equilibrium conditions, high f(ç2) values
are attained, and hydrogen can react with wüstite forming mixed compounds via the reaction
Fe1 – xO + x/2H2 = Fe1 – xHxO.
(12)
420
BEZMEN et al.
Temperature, °ë
Ptot = 2 kbar
1200
Wl1i
W + Femet
1100
Mt
Mt + Wu
Femet
Wu
Ab
1000
Ab–Qtz
900
MW1i
Ab–Or–Qtz
800
MW2i
Wl2i
1
2
3
4
5
6
7
CCO i
700
600
0
500
1000
1500
2000
2500
Hydrogen fugacity, f(H2), bar
Fig. 8. Experimental results on the magnetite–wüstite (MW) and wüstite–metallic iron (WI) equilibria in the Fe–O–H2O–H2 system
compared with experimental results for the solidus curves of the haplogranite system and Ab and Ab–Qtz subsystems. The positions
1
of the Co–CoO (CCOi), MWi, and WIi buffer equilibria are shown ignoring the nonideal behavior of the H2O–H2 system. MW i
1
2
2
and WI i are the data of Jacobsson and Rosen (1981) and Jacobsson (1985); and MW i and WI i are after O’Neill (1988) and
O’Neill and Pownceby (1993). (1)–(5) Phases of the Fe–O system stable depending on f(ç2) at a total pressure of 2 kbar: (1) Mt,
(2) Mt + Wu, (3) Wu, (4) Wu + Femet, (5) Femet; (6) and (7) experimental data of Schmidt et al. (1997) for the solidus of the haplog2
2
ranite system at 2 kbar in the presence of H2O–H2 fluid using the MW i and WI i buffer reactions: (6) calculated from the f(é2)
of the dry system (Schmidt et al., 1997) and (7) taking into account the correction for the interaction of the buffer phases with hydrogen determined in this study.
The MW equilibrium changes into the divariant
reaction:
6Fe3O4 + (2 – 5x)H2
(4 – 2x)Fe3O4 + 6Fe1 – xHxO + (2 – 8x)H2O.
(13)
With increasing hydrogen fugacity, the MW equilibrium is shifted to reduced conditions and transformed
into a divariant field, which is illustrated in Fig. 8. At
low temperatures (below 950°ë), the increasing nonideality of the ç2é–ç2 system enhances the displacement of the reaction to high f(ç2) values.
The behavior of the IW reaction is more complex. In
this case hydrogen reacts with both wüstite and metallic
iron. The dissolution of hydrogen in metallic iron
(occlusion) is described by the reaction
2(1 – x)Fe + xH2 = 2Fe1 – xHx.
(14)
The equilibrium of metallic iron with wüstite in the
presence of hydrogen is described by the reaction
Fe1 – xHxO + H2
Fe1 – xHx + H2O.
(15)
As can be seen in Fig. 8, the increase in hydrogen
solubility in metal at high temperatures enhances the
displacement of the IW reaction toward high f(ç2)
PETROLOGY
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MELTING OF ALKALI ALUMINOSILICATE SYSTEMS
421
Table 5. Experimental results on the magnetite (Mt)–wüstite (Wu) and wüstite (Wu)–metallic iron (Femet) buffer equilibria
in the Fe–O–H2O system at 2 kbar and varying hydrogen fugacity
700°C
850°C
Run no.
Duration, h
f(H2), bar
Phases
Run no.
Duration, h
f(H2), bar
B-40
B-41
B-17
B-45
B-37
B-38
B-26
B-27
B-28
B-50
B-29
B-33
B-32
B-42
48
48
48
72
48
72
48
72
72
72
48
72
48
72
581
581
727
727
872
872
1163
1163
1163
1308
1453
1599
1744
1889
Mt
Mt
Mt
Mt
Mt + Wu
Mt + Wu
Mt + Wu
Mt + Wu
Mt + Wu
Wu
Wu
Wu + Femet
Femet
Femet
B-44
B-46
B-47
48
48
24
1360
1436
1632
950°C
Phases
Wu
Femet
Femet
1200°C
Run no.
Duration, h
f(H2), bar
Phases
Run no.
Duration, h
f(H2), bar
Phases
B-18
B-4
B-15
B-23
B-9
B-2
B-14
B-19
B-20
B-5
B-7
B-21
B-22
B-16
B-11
18
6
5
24
5
8
8
17
18
5
5
18
24
5
15
236
263
328
368
394
525
657
722
788
1051
1313
1366
1419
1445
1576
Mt
Mt
Mt
Mt + Wu
Mt + Wu
Mt + Wu
Mt + Wu
Wu
Wu
Wu
Wu
Wu + Femet
Wu + Femet
Femet
Femet
N-4
N-5
N-6
N-14
N-7
N-9
N-11
N-13
N-10
N-15
N-12
N-17
B-10
7
6
8
3
5
8
8
2
7
8
8
7
9
123
172
246
369
492
738
984
1230
1476
1537
1599
1722
1845
Mt
Mt + Wu
Mt + Wu
Mt + Wu
Wu
Wu
Wu
Wu
Wu
Wu + Femet
Wu + Femet
Femet
Femet
values, and at 1200°ë the equilibrium is strongly
shifted to reducing conditions with the corresponding
expansion of the divariant field. With decreasing temperature, the solubility of H2 in metal diminishes, and
at 950°ë the equilibrium lies near the IW buffer (Fig. 8)
calculated ignoring the hydrogen effect. At lower temperatures, the shift of the IW equilibrium into the
reducing region due to the presence of water is probably related not only to the solubility of hydrogen in
coexisting phases but also to the nonideality of the
H2O–H2 system. It is noteworthy that there are data in
the literature on hydrogen substitution for magnesium
in the olivine structure (Churakov et al., 2003), which
supports the possibility of formation of mixed hydrogen-bearing oxide and silicate compounds. Interesting
results on the interaction of water with metallic iron at
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75 GPa and ~2000 K were reported by Saxena et al.
(2004). Iron hydride and high magnetite (h-Fe3O4)
appeared to be stable under such conditions, i.e., the
magnetite stability field expands to strongly reduced
conditions at high pressures and temperatures.
A comparison of our data with the results reported
by Schmidt et al. (1997) sheds light on the discrepancy
in the behavior of solidus curves of alkaline aluminosilicate systems depending on redox conditions. When
discussing the kinetics of the buffer equilibria, we
noted that the reduced phase was almost completely
oxidized during the time of attainment of the desired
experimental conditions. Hydrogen fugacity increases
strongly in experiments performed using the double-
422
BEZMEN et al.
ampoule method at the expense of water decomposition
by the reactions
3FeO + H2O
Fe3O4 + H2,
(16)
and
Fe + H2O
FeO + H2.
(17)
This is probably the reason for the melting of the
Ab−Or–Qtz system in the presence of H2O–H2 fluid at
the reduced boundary of the magnetite–wüstite field.
Owing to hydrogen diffusion out of the ampoule,
hydrogen fugacity decreases but the charge occurs
under superliquidus conditions. Under the IW buffer
conditions, the solidus temperatures of the haplogranite
system determined by various experimental methods
are almost identical because of the small influence of
hydrogen on the position of this buffer reaction at
765°ë (Fig. 8). It is therefore clear that the discrepancy
between our results and those of Schmidt et al. (1997)
is explained by the fact that these authors calculated
hydrogen fugacity or mole fraction ignoring the influence of hydrogen on the MW and IW buffer equilibria
in the presence of H2O–H2 fluid.
GEOLOGICAL APPLICATIONS
The analysis of redox conditions during the formation of the Earth’s crust suggests an important role of
hydrogen behavior for the evolution of the fluid regime
(Letnikov, 1982; Kadik et al., 1990; Jana and Walker,
1999; Bezmen, 2001). Owing to its high chemical affinity for iron metal, hydrogen and other hydrogen-bearing gases concentrated in the core during the formation
of the Earth’s shells (Stevenson, 1977; Marakushev and
Bezmen, 1983; Bezmen, 1992; Marakushev, 1994,
1999; Okuchi, 1997; Saxena et al., 2004). In the course
of subsequent planetary evolution, hydrogen was transferred to the upper shells, where it was oxidized and
promoted metamorphic and magmatic processes (Letnikov et al., 1977; Marakushev, 1999). Reducing conditions probably prevailed during the early stages of
crust formation. Letnikov (1982) argued that the metamorphism and magmatism of Archean and Early Proterozoic time were characterized by areal distribution of
reduced fluid regimes. The great majority of differentiated complexes were formed during this period.
Hydrogen is the most mobile gas and it escapes from
magma chambers during the crystallization of massifs,
which promotes oxidizing reactions. In general, oxygen
fugacity in natural magmatic processes varies from the
stability of metallic iron to the QFM buffer and higher.
Hydrogen plays an important role in redox evolution,
and its content in fluid decreases with increasing oxygen
fugacity (Fig. 8). The solidus temperatures of the hydrogen-bearing haplogranite system determined in this
study (Fig. 8) and the occurrence of depolymerization in
aluminosilicate melts have important bearings on magmatic and metamorphic processes. The results of investigations of the behavior of buffer reactions in the Fe–O–
H2O–H2 system suggest that granite massifs and related
pegmatites could be formed under reducing conditions
(magnetite is stable up to f(H2) ≈ 1100 bar at 700°ë and
a total pressure of 2 kbar, Fig. 8).
In spite of the development of oxidizing processes
during late magmatic and postmagmatic stages, evidence
for the formation of granite massifs and related pegmatites under reducing conditions is often preserved (Slobodskoi, 1979). Granites sometimes contain magmatic
minerals that crystallized under reduced conditions, such
as native iron (Tyan et al., 1976; Ermolaev and Korolyuk, 1978; Shramenko et al., 1981), titanium (Trunilina
et al., 1988), occasionally lead and zinc (Vladimirova,
1969). Findings of metallic iron (Mets and Men’shikov,
1971), graphite (Soman et al., 1986), and organic matter
(Luk’yanova et al., 1991; Bushuev et al., 1997) were
also reported from granite pegmatites. Ilmenite granites
are probably the most spectacular examples of massifs
formed under reducing conditions.
The analysis of gas components from inclusions in
minerals of granite massifs often indicates the presence
of hydrogen and reduced gases, CO, ëç4, etc. (Glebovitskii et al., 1991; Pakhomova et al., 1992; Bushuev
et al., 1996). Reduced gases were also detected in
inclusions in minerals from granite pegmatites (Shugurova, 1967; Kul’chitskaya et al., 1992). Considerable
amounts of hydrogen and reduced gases were found in
phenocrysts from felsic volcanics (Grib and Shugurova, 1984; Polin and Konovalova, 1985; Shadiev
and Lokhov, 1990).
Our previous experiments (Bezmen et al., 1999;
Fed’kin et al., 1999) demonstrated that, under the pressure of an H–O–C fluid phase with X(ç2) ≈ 0.03, granite melts containing fluorine and phosphorus underwent
superliquidus cryptic and contrasting layering with separation of quartz-rich melts at 800°ë and a total pressure of 2 kbar. The depolymerization of ç2-bearing aluminosilicate melts probably results in the formation of
fluid–silicate clusters (Bezmen, 2001) capable of gravitational movement in granite magmas.
Thus, many genetic features of differentiated granite
complexes and related pegmatites could be related to
reducing conditions, which were probably widespread
during the early stages of formation and evolution of
silicic magmas.
CONCLUSIONS
(1) At an H2O–H2 fluid pressure of 2 kbar, the solidus curves of aluminosilicate systems display a distinct
temperature minimum within a hydrogen fugacity
range of 300–500 bar, when melting temperatures
decrease relative to the H2O-saturated solidus by 22°C
for albite, 30°C for albite with quartz, and 40°C for the
haplogranite system.
(2) A comparison of structural characteristics of
alkaline aluminosilicate glasses synthesized under
pressure of pure water and water–hydrogen fluid (data
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MELTING OF ALKALI ALUMINOSILICATE SYSTEMS
of NMR and X-ray photoelectron spectroscopy) suggests that the mechanism of dissolution of water and
water–hydrogen fluid in melts are different. The dissolution of hydrogen in H2O-saturated melts results in
their depolymerization, which is accompanied by an
increase in water solubility (Bezmen et al., 1990). This
effect is responsible for the depression of solidus temperatures in the H2O–H2-saturated aluminosilicate systems studied.
(3) Buffer reactions in the Fe–O system (equilibria of
wüstite with magnetite and metallic iron) are widely
used for the estimation of redox conditions in experimental and natural systems. It was experimentally established that the hydrogen fugacity values attained in the
presence of water under reduced conditions imposed by
the MW and IW buffer equilibria are sufficiently high for
hydrogen interaction with wüstite and metallic iron. As a
result, the equilibria transform into divariant fields, and
the stability of magnetite, which is a widespread mineral
of granites, is shifted to reduced conditions.
(4) The data obtained here suggest the possibility of
hydrogen participation in the genesis and evolution of
granite melts and related pegmatites. The occurrence of
minerals formed under reducing conditions in granites
and the detection of hydrogen, methane, and other
reduced gases in the fluid phase released from minerals
confirm the presence of hydrogen in granitoid melts.
Owing to their high depolymerizing capacity, hydrogen-bearing fluids are of fundamental importance for
the formation of differentiated granite complexes.
ACKNOWLEDGMENTS
The authors are grateful to Profs. G.P. Zaraisky
(Institute of Experimental Mineralogy, Russian Academy of Sciences), F. Holtz (Institut für Mineralogie,
Universität Hannover, Germany), and B. Schmidt
(Department of Physics, University of Warwick, UK),
who kindly provided analyzed minerals and a gel of the
desired composition for the preparation of starting
materials for our experiments. This study was financially supported by the Russian Foundation for Basic
Research, project nos. 01-05-64837, 02-05-64205,
03-05-64511, and 03-05-64535, and fundamental program no. 10 of the Russian Academy of Sciences
“Experimental Investigations of Physicochemical Problems Relevant to Geologic Processes.”
REFERENCES
1. R. J. Arculus, J. B. Dawson, R. H. Mitchell, et al., “Oxidation State of the Upper Mantle Recorded by Megacryst Ilmenite in Kimberlite and Type A and B Spinel
Lherzolite,” Contrib. Mineral. Petrol. 85, 85–94 (1984).
2. C. G. Ballhaus, “Redox States of Lithospheric and
Asthenospheric Upper Mantle,” Contrib. Mineral.
Petrol. 114, 331–348 (1993).
3. C. G. Ballhaus and E. F. Stumpfl, “Occurrence and Petrological Significance of Graphite in the Upper Critical
PETROLOGY
Vol. 13
No. 5
2005
423
Zone, Western Bushveld Complex, South Africa,” Earth
Planet. Sci. Lett. 74, 58–68 (1985).
4. R. F. Bartholomew and J. W. H. Schreurs, “Wide-Line
NMR Study of Protons in Hydrosilicate Glasses of Different Water Content,” J. Non-Cryst. Solids 38/39,
679−684 (1980).
5. C. W. Burnham, “Significance of Volatile Components,”
in The Evolution of the Igneous Rocks, Ed. by
H. S. Yoder, Jr. (Princeton Univ. Press, New Jersey,
1979; Mir, Moscow, 1983), pp. 425–467.
6. N. I. Bezmen, “High Pressure Gas Media Apparatus for
Controlling Fugacity of Hydrogen-Bearing Fluid Systems,” in Proceedings of the First Indo–Soviet Workshop on Experimental Mineralogy and Petrology, Ed.
by V. K. Gaur and A. K. Gupta (Govern. Ind. Publ.,
Dehli, 1989), pp. 9–15.
7. N. I. Bezmen, “Hydrogen in Magmatic System,” Exp.
Geosi. 1 (2), 1–33 (1992).
8. N. I. Bezmen, “Superliquidus Differentiation of FluidBearing Magmatic Melts under Reducing Conditions as
a Possible Mechanism of Formation of Layered Massifs: Experimental Investigations,” Petrologiya 9,
398−416 (2001) [Petrology 9, 345–361 (2001)].
9. N. I. Bezmen, V. A. Zharikov, V. O. Zavel’sky, et al.,
“The System Albite–Hydrogen–Water: Solubility of
Fluid Components under 2 kbar and 1200°C,”
Geokhimiya, No. 5, 640–648 (1990a).
10. N. I. Bezmen, V. O. Zavel’sky, Yu. P. Dikov, and
M. B. Epel’baum, “Albite Melt–Hydrogen Interaction,”
Dokl. Akad. Nauk SSSR 311, 458–462 (1990b).
11. N. I. Bezmen, V. A. Zharikov, M. B. Epelbaum, et al.,
“The System NaAlSi3O8–H2O–H2 (1200°C, 2 kbar): The
Solubility and Interaction Mechanism of Fluid Species
with Melt,” Contrib. Mineral. Petrol. 109, 89–97 (1991).
12. N. I. Bezmen, A. V. Fed’kin, and G. P. Zaraisky, “Experimental Study of Phosphorus and Fluorine Influence on
the Superliquidus Differentiation of Granite Melts: Preliminary Data,” Exp. Geosci. 8 (1), 49–53 (1999).
13. S. R. Bohlen, A. L. Boettcher, and V. J. Wall, “The System Albite–H2O–CO2: A Model for Melting and Activities of Water at High Pressures,” Am. Mineral. 67,
451−462 (1982).
14. C. W. Burnham, “Water and Magmas: A Mixing
Model,” Geochim. Cosmochim. Acta 39, 1077–1084
(1975).
15. A. G. Bushev, G. A. Sidorenko, N. A. Cherkashina, and
G. L. Zhuikova, “Hydrocarbons in Prospecting for Pegmatite Deposits,” Zap. Vseross. Mineral. O–va, No. 3,
1–10 (1996).
16. A. G. Bushev, V. P. Kuz’mina, V. F. Penkov, et al.,
“Organic Compounds in Minerals of the Pamir Pegmatites,” Geokhimiya, No. 3, 348–354 (1997) [Geochem.
Int. 35, 239–244 (1997)].
17. J. L. Charlou, J. P. Donval, Y. Fouquet, et al.,
“Geochemistry of High H2 and CH4 Vent Fluids Issuing
from Ultramafic Rocks at the Rainbow Hydrothermal
Field (36°14′ N, MAR),” Chem. Geol. 191, 345–360
(2002).
18. A. S. Chekhmir, A. G. Simakin, and M. B. Epel’baum,
Dynamic Phenomena in Fluid–Magmatic Systems
(Nauka, Moscow, 1991) [in Russian].
424
BEZMEN et al.
19. I.-M. Chou, “Permeability of Precious Metals to Hydrogen at 2 kb Total Pressure and Elevated Temperatures,”
Am. J. Sci. 286, 638–658 (1986).
20. I.-M. Chou, “Oxygen Buffer and Hydrogen Sensor
Technique at Elevated Pressures and Temperatures,” in
Hydrothermal Experimental Techniques, Ed. by
H. L. Barnes and G. C. Ulmer (Wiley, New York, 1987),
pp. 61–99.
21. S. V. Churakov, N. R. Khisina, V. S. Urasov, and R. Wirth,
“First-Principles Study of (MgH2SiO4)–n(Mg2SiO4)
Hydrous Olivine Structures: I. Crystal Structure Modeling
of Hydrous Olivine Hy-2a (MgH2SiO4)–3(Mg2SiO4),”
Phys. Chem. Mineral. 30, 1–11 (2003).
22. A. Ebadi and W. Johannes, “Beginning of Melting and
Composition of First Melts in the System Qtz–Ab–Or–
H2O–CO2,” Contrib. Mineral. Petrol. 106, 286–295
(1991).
23. H. Eckert, J. P. Yesinowski, L. A. Silver, and E. M. Stolper,
“Water in Silicate Glasses: Quantitation and Structural
Studies by 1H Solid Echo and MAS–NMR Methods,”
J. Phys. Chem. 92, 2055–2064 (1988).
24. M. B. Epel’baum, Silicate Melts with Volatile Components (Nauka, Moscow, 1980) [in Russian].
25. P. V. Ermolaev and V. N. Korolyuk, “Composition and
Structure of Magnetic Granites,” Dokl. Akad. Nauk
SSSR 240, 155–158 (1978).
26. I. Farnan, S. C. Kohn, and K. Dupree, “A Study of the
Structural Role of Water in Hydrous Silicate Glass
Using Cross-Polarization Magic Angle Spinning
NMR,” Geochim. Cosmochim. Acta 51, 2869–2874
(1987).
27. A. Fed’kin, R. Seltman, D. Rhede, et al., “Reaction of
Granitic Melt with Fluorine and Phosphorus Enriched
Fluids at H–O–C Conditions,” in Mineral Deposits:
Processes to Processing (Balkema, Rotterdam, 1999),
pp. 349–352.
28. V. A. Glebovitskii, E. A. Vapnin, and I. S. Sedova,
“Fluid Regime of Granite Formation in Ultrametamorphism Zones,” Izv. Akad. Nauk SSSR, Ser. Geol.,
No. 10, 44–57 (1991).
29. J. R. Goldsmith and D. M. Jenkins, “The Hydrothermal
Melting of Low and High Albite,” Am. Mineral. 70,
924–933 (1985).
30. R. W. Goranson, “Silicate–Water System: Phase Equilibria in the NaAlSi3O8–H2O and KAlSi3O8–H2O Systems at High Temperatures and Pressures,” Am. J. Sci.
35A, 71–91 (1938).
31. K.-D. Grevel and N. D. Chatterjee, “A Modified
Redlich–Kwong Equation of State for H2–H2O Fluid
Mixtures at High Pressures and Temperatures above
400°C,” Eur. J. Mineral. 4, 1303–1310 (1992).
32. E. N. Grib and N. A. Shugurova, “The Composition of
Gaseous Phase of Silicic Lavas in the Uzon Geyser
Region: Evidence from Microinclusions,” Vulkanol.
Seismol., No. 3, 87–90 (1984).
33. S. E. Haggerty and P. B. Toft, “Native Iron in the Continental Lower Crust: Petrological and Geophysical
Implications,” Science 229, 647–649 (1985).
34. C. Harvie, J. W. Weare, and M. O’Keefe, “Permeation
of Hydrogen through Platinum: A Re-evaluation of the
Chou, et al.,” Geochim. Cosmochim. Acta 44, 899–900
(1980).
35. D. Holland, “NMR Studies of Thermal Effects on Glass
Structure,” J. Phys. Chem. 98, 65–70 (1999).
36. I. R. Holloway, “Compositions and Volumes of Supercritical Fluids in the Earth’s Crust,” in Fluid Inclusions:
Applications to Petrology, Ed. by L. S. Hollister and
M. Crawford (Mineral. Assoc. Can. Publ., Toronto,
1981), pp. 13–18.
37. F. Holtz, M. Pichavant, P. Barbey, and W. Johannes,
“Effect of H2O on Liquidus Phase Relations in the Haplogranite System at 2 and 5 kbar,” Am. Mineral. 77,
1223–1241 (1992).
38. E. Jacobsson, “Solid State EMF Studies of the Systems
FeO–Fe3O4 and Fe3O4–Fe2O3 in the Temperature
Range 1000–1600 K,” Scand. J. Metall. 14, 252–256
(1985).
39. E. Jacobsson and E. Rosen, “Thermodynamic Studies
of High Temperature Equilibria: 25. Solid State EMF
Studies of the Systems Fe–FeO, Ni–NiO and Co–CoO
in the Temperature Range 1000–1600 K,” Scand. J.
Metall. 10, 39–43 (1981).
40. W. Johannes and F. Holtz, Petrogenesis and Experimental Petrology of Granitic Rocks (Springer-Verlag, Berlin, 1996).
41. D. Jana and D. Walker, “Core Formation in the Presence
of Various C–H–O Volatile Species,” Geochim. Cosmochim. Acta 63, 2299–2310 (1999).
42. A. A. Kadik, “Evolution of Earth Redox State during
Upwelling of Carbon-Bearing Mantle,” Phys. Earth
Planet. Int. 100, 157–166 (1997).
43. A. A. Kadik, O. A. Lukanin, and I. V. Lapin, Physicochemical Evolution of Basaltic Magmas in Subsurface
Sedimentary Deposits (Nauka, Moscow, 1990) [in Russian].
44. A. A. Kadik, F. Pineau, Y. Litvin, et al., “Formation of
Carbon and Hydrogen Species in Magmas at Low Oxygen Fugacity,” J. Petrol. 45, 1297–1310 (2004).
45. H. Keppler, “The Influence of the Fluid Phase Composition on Solidus Temperatures in the Haplogranite System NaAlSi3O8–KAlSi3O8–SiO2–H2O–CO2,” Contrib.
Mineral. Petrol. 102, 321–327 (1989).
46. S. C. Kohn, “The Dissolution Mechanism of Water in
Silicate Melts: A Synthesis of Recent Data,” Mineral.
Mag. 64, 385–408 (2000).
47. S. C. Kohn, R. Dupree, and M. E. Smith, “A Multinuclei
Magnetic Resonance Study of the Structure of Hydrous
Albite Glasses,” Geochim. Cosmochim. Acta 53,
2925−2935 (1989).
48. S. C. Kohn, R. Dupree, and R. Mortuza, “The Interaction between Water and Alumosilicate Magmas,” Chem.
Geol. 96, 399–409 (1992).
49. A. A. Kul’chitskaya, D. K. Voznyak, Yu. A. Galaburda,
and V. I. Pavlishin, “High-Temperature Pyrolitic Gas
Chromatography of Pegmatitic Minerals,” Mineral. Zh.
14 (6), 88–98 (1992).
50. F. A. Letnikov, “Fluid Regime Evolution of Endogenic
Processes during the Geologic History of the Earth,”
Dokl. Akad. Nauk SSSR 226, 1438–1440 (1982).
51. F. A. Letnikov, I. K. Karpov, A. N. Kiselev, and
B. O. Shkandrii, Fluid Regime of the Earth’s Crust and
Upper Mantle (Nauka, Moscow, 1977) [in Russian].
PETROLOGY
Vol. 13
No. 5
2005
MELTING OF ALKALI ALUMINOSILICATE SYSTEMS
52. Y. Liu, H. Nekvasil, and H. Long, “Water Dissolution in
Albite Melts: Constraints from ab Initio NMR Calculations,” Geochim. Cosmochim. Acta 66, 4149–4163
(2002).
53. V. T. Luk’yanova, R. V. Lobzova, and V. N. Trubkina,
“Composition of Cerite Fibers from Volyn’ Pegmatites:
Genetic Implications,” in Abstracts of Annual Conference of the All-Union Mineralogical Society on Economic and Ecological Aspects of Mineralogy, Zvenigorod, March 19–21, 1990 (Nauka, Moscow, 1991),
Vol. 2, pp. 137–138.
54. R. W. Luth and A. L. Boettcher, “Hydrogen and the
Melting of Silicates,” Am. Mineral. 71, 264–276
(1986).
55. A. A. Marakushev, “Genetic Groups (Families) of
Meteorites and Lunar and Terrestrial Rocks,”
Petrologiya 2, 380–409 (1994).
56. A. A. Marakushev, Origin of the Earth and the Nature
of Its Endogenic Activity (Nauka, Moscow, 1999) [in
Russian].
57. A. A. Marakushev and N. I. Bezmen, The Evolution of
Meteoritic Matter, Planets, and Magmatic Associations
(Nauka, Moscow, 1983) [in Russian].
58. Yu. P. Mel’nik, Thermodynamic Properties of Gases
under Conditions of Deep Petrogenesis (Naukova
Dumka, Kiev, 1978) [in Russian].
59. O. F. Mets and Yu. P. Men’shikov, “Native Iron from
Pegmatites of the Area of Stremny River, Kola Peninsula,” Zap. Vses. Mineral O–va 100, 329–337 (1971).
60. Y. Nakamura, The System SiO2–H2O–H2 at 15 kbar
(Carnegie Inst., Washington, 1974).
61. M. Nowak and H. Behrens, “The Speciation of Water in
Haplogranitic Glasses and Melts Determined by in Situ
Near-Infrared Spectroscopy,” Geochim. Cosmochim.
Acta 59, 3445–3450 (1995).
62. H. St. C. O’Neill, “System Fe–O and Cu–O: Thermodynamic Data for Equilibria Fe–'FeO', Fe–Fe3O4, 'FeO'–
Fe3O4, Fe3O4–Fe2O3, Cu–Cu2O and Cu2O–CuO from
EMF Measurements,” Am. Mineral. 73, 479–486
(1988).
63. H. St. C. O’Neill and M. I. Pownceby, “Thermodynamic Data from Redox Reactions at High Temperatures: 1. An Experimental and Theoretical Assessment
of the Electrochemical Method Using Stabilized Zirconia Electrolytes, with Revised Values for the Fe–'FeO',
Co–CoO, Ni–NiO, and Cu–Cu2O Oxygen Buffers, and
New Data for W–WO2 Buffer,” Contrib. Mineral.
Petrol. 114, 296–314 (1993).
64. T. Okuchi, “Hydrogen Could Be the Most Common
Element Present in the Core,” Science 278, 1781–1792
(1997).
65. D. Padro, B. C. Schmidt, and R. Dupree, “Water Solubility Mechanism in Hydrous Aluminosilicate Glasses:
Information from 27Al MAS and MQMAS NMR,”
Geochim. Cosmochim. Acta 67, 1543–1551 (2003).
66. V. A. Pakhomova, A. K. Rub, L. N. Khetchikov, and
M. G. Rub, “Fluid Phase of Rare-Metal Granitic Melts
in the Central Sikhote Alin,” Izv. Akad. Nauk SSSR,
Ser. Geol., No. 4, 64–73 (1992).
67. E. S. Persikov and M. B. Epel’baum, “Set-up for Studying Viscosity and Density of Magmatic Melts under
High Pressure,” in Experiment and Technique of High
PETROLOGY
Vol. 13
No. 5
2005
425
Gas and Solid Phase Pressures, Ed. by I. P. Ivanov and
Yu. A. Litvin (Nauka, Moscow, 1978), pp. 94–99
[in Russian].
68. E. S. Persikov, P. G. Bukhtiyarov, S. F. Pol’skoi, and
A. S. Chekhmir, “Hydrogen–Magma Interaction,” in
Role of Experiments in Studies of Important Geological
Problems, Ed. by V. A. Zharikov (Nauka, Moscow,
1986), pp. 48–70 [in Russian].
69. V. F. Polin and N. L. Konovalova, “Fluid Regime during
Formation of Contrasting Rock Association of the
Amguemo–Komgalan Volcanic Field, East Chukchi
Peninsula,” in Volcanic and Volcanic–Sedimentary
Rocks of the Far East (Nauka, Vladivostok, 1985),
pp. 3–20 [in Russian].
70. O. Redlich and J. N. S. Kwong, “On the Thermodynamic of Solutions: V. An Equation of State: Fugacities
of Gases,” Chem. Rev. 44, 233–244 (1949).
71. T. Riemer, B. C. Schmidt, H. Behrens, and R. Dupree,
“H2O/OH Ratio Determination in Hydrous Aluminosilicate Glasses,” Solid State NMR 15, 201–207 (2000).
72. S. K. Saxena, H-P. Liermann, and G. Shen, “Formation
of Iron Hydride and High Magnetite at High Pressure
and Temperature,” Phys. Earth Planet. Int. 146,
313−317 (2004).
73. B. Scaillet, M. Pichavant, J. Roux, et al., “Improvements of the Shaw Membrane Technique for Measurement and Control of f H 2 at High Temperature and Pressures,” Am. Mineral. 77, 647–650 (1992).
74. B. C. Schmidt, F. Holtz, B. Scaillet, and M. Pichavant,
“The Influence of H2O–H2 Fluids and Redox Conditions on Melting Temperatures in the Haplogranite System,” Contrib. Mineral. Petrol. 126, 386–400 (1997).
75. B. C. Schmidt, T. Riemer, S. C. Kohn, et al., “Different
Water Solubility Mechanism in Hydrous Glasses along
the Quartz–Albite Join: Evidence from NMR Spectroscopy,” Geochim. Cosmochim. Acta 64, 513–526
(2000).
76. B. C. Schmidt, H. Behrens, T. Riemer, et al., “Quantitative Determination of Water Speciation in Aluminosilicate Glasses: A Comparative NMR and IR Spectroscopic Study,” Chem. Geol. 174, 195–208 (2001a).
77. B. C. Schmidt, T. Riemer, S. C. Kohn, et al., “Structural
Implications of Water Dissolution in Haplogranitic
Glasses from NMR Spectroscopy: Influence of Total
Water Content and Mixed Alkali Effect,” Geochim.
Cosmochim. Acta 65, 2949–2964 (2001b).
78. M. G. Shadiev and K. I. Lokhov, “Behavior of Fluids
during Melting of Granites in Basaltic Melt: Evidence
from Jurassic Volcanics of Southwestern Transbaikalia,” Geol. Geofiz., No. 11, 80–85 (1990).
79. H. R. Shaw, “Hydrogen–Water Vapor Mixture: Control
of Hydrothermal Atmosphere by Hydrogen Osmosis,”
Science 139, 1220–1222 (1963).
80. A. Shen and H. Keppler, “Infrared Spectroscopy of
Hydrous Silicate Melts to 1000°C and 10 kbar: Direct
Observation of H2O Speciation in Diamond-Anvil
Cell,” Am. Mineral. 80, 1335–1338 (1995).
81. K. I. Shmulovich, V. A. Masur, A. G. Kalinichev, and
L. I. Khodorevskaya, “P–V–T and Component Activity–Concentration Relations for H2O-Nonpolar Gas
Systems,” Geochem. Int. 17, 18–31 (1980).
426
BEZMEN et al.
82. K. I. Shmulovich, V. M. Shmonov, and V. A. Zharikov,
“The Thermodynamics of Supercritical Fluid Systems,”
Adv. Phys. Geochem. 2, 173–190 (1982).
83. I. F. Shramenko, D. A. Stadnik, L. G. Samoilovich,
et al., “Native Iron in Granites of the Korsun’–Novyi
Mirgorod Pluton,” Dokl. Akad. Nauk SSSR 257,
1450−1453 (1981).
84. N. A. Shugurova, “Changes in Gas Phase Composition
in Minerals during Formation of Quartz–Fluorite Pegmatites,” Dokl. Akad. Nauk SSSR 176, 699–702
(1967).
85. L. A. Silver and E. Stolper, “Water in Albite Glasses,”
J. Petrol. 30, 667–709 (1989).
86. L. A. Silver, P. D. Ihinger, and E. Stolper, “The Influence of Bulk Composition on the Speciation of Water in
Silicate Glasses,” Contrib. Mineral. Petrol. 104,
142−162 (1990).
87. R. M. Slobodskoi, “Reducing Intratelluric Fluids and
Formation of Granitoid Batholiths,” Geol. Geofiz.,
No. 5, 22–31 (1979).
88. V. N. Sobachenko and N. V. Zaboeva, “Fluid Regime
during Granitization- and Faulting-Related Metasomatism in Precambrian Troughs,” Geokhimiya, No. 7,
1123–1129 (1994).
89. K. Soman, R. V. Lobzova, and R. M. Sivadas, “Geology,
Genetic Types, and Origin of Graphite in South Kerala,
India,” Econ. Geol. 81, 997–1002 (1986).
90. J. R. Sowerby and H. Keppler, “Water Speciation in
Rhyolitic Melt Determined by in-Situ Infrared Spectroscopy,” Am. Mineral. 84, 1843–1849 (1999).
91. D. J. Stevenson, “Hydrogen in the Earth’s Core,” Nature
268, 130–131 (1977).
92. E. Stolper, “Water in Silicate Glasses: An Infrared Spectroscopic Study,” Contrib. Mineral. Petrol. 81, 1–17
(1982a).
93. E. Stolper, “The Speciation of Water in Silicate Melts,”
Geochim. Cosmochim. Acta 46, 2609–2620 (1982b).
94. E. Stolper, “Temperature Dependence of the Speciation
of Water in Rhyolitic Melts and Glasses,” Am. Mineral.
74, 1247–1257 (1989).
95. A. A. Tarzimanov and V. S. Lozovoi, “Resistance as a
Function Pressure in Measurements by the Platinum
Thermometer,” Izmer. Tekh., No. 12, 36–37 (1969).
96. W. R. Taylor and D. H. Green, “The Role of Reduced
C–H–O Fluids in Mantle Partial Melting,” in Kimberlites and Related Rocks, Geol. Soc. Aust. Spec. Publ. 1
(14), 592–602 (1989).
97. V. A. Trunilina, S. P. Roev, V. F. Makhotko, and
N. V. Zayakina, “Native Titanium in Granitoids of the
Bezymyannyi Pluton, Eastern Yakutia,” Dokl. Akad.
Nauk SSSR 303, 948–951 (1988).
98. O. F. Tuttle and N. L. Bowen, “Origin of Granite in the
Light of Experimental Studies in the System
NaAlSi3O8–KAlSi3O8–SiO2–H2O,” Mem. Geol. Soc.
Am., No. 74 (1958).
99. V. D. Tyan, P. V. Ermolov, N. V. Popov, et al., “Native
Iron in Granitoids: Magmatic Nature and Oxidation
Products,” Geol. Geofiz., No. 5, 48–54 (1976).
100. E. V. Vladimirova, “Finding of Native Lead and Zinc in
the Kuznetsk Alatau,” Izv. Tomsk. Politekh. Inst. 11, 11
(1969).
101. J. A. Welhan and H. Craig, “Methane and Hydrogen in
East Pacific Rise: Hydrothermal Fluid,” Geophys. Res.
Lett. 6, 829–831 (1979).
102. J. A. Welhan and H. Craig, “Methane, Hydrogen, and
Helium in Hydrothermal Fluids at 21° N on the East
Pacific Rise,” in Hydrothermal Processes at Seafloor
Spreading Centers, Ed. by P. A. Rona, L. Bostrom,
L. Laubier, and K. Smith (Plenum, London, 1983),
pp. 391–409.
103. A. C. Withers, Y. Zhang, and H. Behrens, “Reconciliation of Experimental Results on H2O Speciation in Rhyolitic Glass Using in-Situ and Quenching Techniques,”
Earth Planet. Sci. Lett. 173, 343–349 (1999).
104. V. O. Zavel’sky and N. I. Bezmen, “Water in Albite
Glass: NMR Data,” Geokhimiya, No. 8, 1120–1124
(1990).
105. V. O. Zavel’sky and T. P. Salova, “The Role of Sodium
in the Mechanism of Interaction of Sodium Silicate
Melt with Aqueous Fluid: Evidence from 1H and 23Na
NMR,” Geokhimiya, No. 8, 1–8 (2001) [Geochem. Int.
39, 748–753 (2001)].
106. V. O. Zavel’sky, N. I. Bezmen, and V. A. Zharikov,
“Water in Albite Glasses: OH-Group, Isolated Molecules, and Clusters,” J. Non-Cryst. Solids 224, 225–231
(1998).
107. V. O. Zavel’sky, T. P. Salova, and M. B. Epel’baum,
“Mechanisms of Solution and Speciation of H2O in
Quartz Glass (1H-NMR Studies),” Geokhimiya, No. 2,
218–224 (1999) [Geochem. Int. 37, 187–192 (1999)].
108. V. O. Zavel’sky, T. P. Salova, M. B. Epelbaum, et al.,
“State of Nondissociated Molecules of Water Inclusions
in Aluminosilicate Glasses (1H NMR and Electron
Microscopy Study),” Phys. Chem. Glasses 41, 182–187
(2000).
109. V. O. Zavel’sky, N. I. Bezmen, T. P. Salova, and A. A. Lundin, “1H and 23Na NMR Spectroscopy of H2O–H2Bearing Sodium Silicate Glasses,” Geokhimiya, No. 11,
1221–1226 (2003) [Geochem. Int. 41, 1118–1122
(2003)].
110. V. O. Zavel’sky, T. P. Salova, N. I. Bezmen, and A. A. Lundin, “Physicochemical Features of Water Polymorphism in Water–Hydrogen-Bearing Model Volcanic
Glasses: NMR Data,” Zh. Khim. Fiz. 78, 706–719
(2004).
111. Q. Zeng, H. Nekvasil, and C. P. Grey, “Proton Environments in Hydrous Aluminosilicate Glasses: A 1H/27Al and
1H/23Na TRAPDOR NMR Study,” J. Phys. Chem. B 103,
7406–7415 (1999).
112. Q. Zeng, H. Nekvasil, and C. P. Grey, “In Support of
Depolymerisation Model for Water in Sodium Aluminosilicate Glasses: Information from NMR Spectroscopy,” Geochim. Cosmochim. Acta 64, 883–896
(2000).
113. V. A. Zharikov, “Component Regime in Melts and Magmatic Replacement,” in Problems in Petrology and
Genetic Mineralogy (Nauka, Moscow, 1969), Vol. 1,
pp. 62–79 [in Russian].
PETROLOGY
Vol. 13
No. 5
2005