 REF_0001 NOTE:

 REF_0002 NOTE:

 REF_0003 NOTE:

 REF_0004 NOTE:

 REF_0005 NOTE:

 REF_0006 NOTE:

 REF_0007 NOTE:

      Thermal expansion assessed by Guillermet and Gustafson (1985).

 REF_0008 NOTE:

 Free energy of hercynite is determined from the following reaction:

                  Alm + Sill = Her + Q

 The heat capacity expression for hercynite used by Saxena and Eriksson

 (1983b) is adjusted here. The entropy is from Robie et al. (1978).

 Enthalpy is adjusted within the error limits of Robie et al. (1978)

 (-1966.48 +/- 8.5 KJ/mol).

 REF_0009 NOTE: Calorimetric data:      H: -3983.93+1.3         S: 198.6 +0.6

 H, Charlu et al. (1981); S, Hemingway and Robie (1984).

        Wollastonite and Gehlenite participate in reactions involving the

 breakdown of anorthite. These reactions, studied by various workers are as

 follows:

                          An + Woll = Gr + Q

                          An + Ge = Gr + Cor

                          An + Ge + Woll = Gr

 For the second reaction, Gasparik (1984b) evaluated the experimental data

 of Boettcher (1970) and Huckenholz et al. (1975) and found the equilibrium

 pressure as

                      P = 23.8T(C) - 17440

 Using these data, del-C'p, the difference between the experimental and the

 calculated heat capacities, for gehlenite is found to be

            del-C'p = 7.5491 (+/-0.134) + 0.0027126 (+/-0.00019) * T

 and a corresponding del-Hf listed above. This value is comparable to

 -3979046 J/mol derived from the del-Hf(970) value of Charlu et al. (1981)

 using the Cp expression from Robie et al.(1978). The entropy of gehlenite

 is selected as 204.35 J/mol.K following Woodhead (1977), who considers a

 progressively increasing disorder in gehlenite with temperature.

 REF_0010 NOTE: Calorimetric data:      H: -3865.6 +1.13        S: 209.33+2.09

 H, Charlu et al. (1981); S, Robie et al. (1978).

 The experimental data of Yoder (1968) involving wollastonite, monticellite

 and akermanite are used to calculate the H of akermanite. The S and Cp data

 are from Robie et al.(1978). The data are close to the calorimetric data of

 Haas et al. (1981) and Charlu et al. (1981).

 REF_0011 NOTE: Calorimetric data:      H: -2171.72+3.76        S: 94.12+1.0

 H, Brousse et al.(1984)(-2174.14,Haselton 1979);S, Robie et al.(1982b).

     Brousse et al. (1984) discussed the calorimetric data on enthalpy of

 forsterite which range from a high of -57.823 to a low of -63.262 KJ/mol

 (del-Hf(298)-oxides). The value recommended here is -60.68 KJ/mol. Most

 of the calorimetric data are close to this value. The entropy and Cp of

 forsterite are from Robie et al. (1978). Robie et al. (1982b) determined

 the heat capacity of forsterite in the range 5-380 K. The Cp recommended

 here is closely similar to the Cp determined by them. Thermal expansion and

 compressibility are consistent respectively with the data of Suzuki (1975)

 and Sumino et al. (1977).

 REF_0012 NOTE:

 REF_0013 NOTE: Free energy of fayalite is adopted from Robie et al. (1982a) whi
ch is

 determined by calorimetry. Thermal expansion data is consistent with

 Suzuki et al.(1981).

 REF_0014 NOTE: Calorimetric data: H: -2248.9 +1.72,

 Brousse et al. (1984); S: 108.1 +0.2, Sharp et al. (1986).

 The enthalpy of monticellite

 is adjusted from Brousse et al. (1984) so that an improved fit to

 Yoder's (1968) experimental data

 involving wollastonite, monticellite and akermanite is obtained. The

 entropy is from Robie et al. (1978) and the heat capacity equation is as

 recommended by Helgeson et al. (1978).

 REF_0015 NOTE: Calorimetric data: H: -1546.19+1.76,Brousse et al.(1984);

  S: 66.27+0.1, Krupka et al.(1985a).

    The enthalpy of enstatite is from Brousse et al. (1984). Although

 there are other determinations of the enthalpy, the value of Brousse

 et al. is close to the average of all the values. So, their value is

 adopted. Entropy and heat capacity of enstatite are from Haselton

 (1979). All these values are calorimetric.

 REF_0016 NOTE:

    The properties of these phases are adopted from Saxena et al. (1986).

 Their evaluations are based on the phase equilibrium data compiled by

 Lindsley (1983) on quadrilateral pyroxenes.

 REF_0017 NOTE:

 Calorimetric data: S: 94.6 +0.1, Bohlen and Boettcher (1981) (derived indirectl
y).

 Ferrosilite breaks down to give fayalite and quartz according to the

 following reaction:

                             Fer = Fay + Q

 This reaction was studied experimentally by Bohlen et al. (1980). However,

 when orthopyroxene solutions break down there is a three phase stability

 field where orthopyroxene solution is present along with olivine solution

 and quartz. This phenomenon was recently investigated by Bohlen and

 Boettcher (1981).

     Free energy of ferrosilite is closely constrained by the above

 reaction. Enthalpy (adjusted by 300 J) and entropy are the recommended

 values of Bohlen and Boettcher (1981) and the heat capacity is calculated

 from the above reaction. The compressibility data is consistent with

 the data of Bass and Weidner (1984) and  Weidner (1986).

 REF_0018 NOTE: Calorimetric data:  H: -1544.15+2.09  S: 67.86+0.42

 Kiseleva et al. (1979). Gasparik (1990a,b) discussed the phase relations

 in the MgSiO3 system with three polymorphs (clino) a low-clino, a high-P

 form and a high-T clino. This phase is the low-clinoenstatite.

 REF_0019 NOTE:

 Calorimetric data: H: -1600.15 +0.86,S: 72.15 +0.42

 Robie et al. (1978).

     The properties listed in Robie et al. (1978) are adopted. These

 data are from calorimetric sources.

 REF_0020 NOTE:

     The enthalpy and entropy are as recommended by Saxena et al. (1986)

 adjusted from the data of Helgeson et al. (1978) to fit the equilibrium

 data on quadrilateral pyroxenes from Lindsley (1983). Recently, Haselton

 et al. (1987) determined the heat capacity of hedenbergite by low-temperature

 adiabatic and differential scanning calorimetry in the range 9-647 K.

 The heat capacity recommended by Saxena et al. (1986) is consistent with

 this later experimental determination. The difference between the

 heat capacity of Saxena et al. and Haselton et al. at 647 K is 0.8 J/cation.

 REF_0021 NOTE: Calorimetric data: H: -3029.88+4.2;

 Hemingway et al. (1981) (derived indirectly);  S: 133.48+1.26., Robie et al. (1
978)

 Entropy and Cp of jadeite are as listed in Robie et al. (1978).

 REF_0022 NOTE: Calorimetric data: H: -5249.82+10.71;

 Chatillon-Colinet et al.(1983a); S: 339.69+0.51, Metz et al.(1983).

 Cp of almandine is estimated from the Fe-Mg exchange reaction

                          En + Alm = Fer + Pyr                          (a)

 by assuming that del-Cp of the reaction is zero. Although this is normally

 not true, it is preferred over the Cp determined by Metz et al. (as in

 Bohlen et al. (1986)) for the reason that when their determined Cp values

 are extrapolated to high T's such as for the range of experiments of Lee and

 Ganguly (1987) (see Ganguly and Saxena, 1988) they become too high to fit

 the observed equilibria.

 The substantial adjustment in H and S are needed to be consistent with

 the experimental phase equilibria data on the reactions involving rutile

 and ilmenite and anorthite and forsterite as considered later.

 REF_0023 NOTE:Calorimetric data: H: -6290.76+1.59;

 Charlu et al. (1975);  S: 266.28, Haselton and Westrum (1980).

 The enthalpy is from Charlu et al. (1975), the entropy is from Haselton

 and Westrum (1980) and the heat capacity is from Haselton (1979). The value

 are calorimetric. The thermal expansion is consistent with Skinner's (1956)

 Similarly the compressibility data are consistent with the data of Bonczar

 (1977).

 REF_0024 NOTE: Calorimetric data: H: -6632.76+2.79;

 Charlu et al. (1978);  S: 260.13, Haselton and Westrum (1980).

    The enthalpy is from Charlu et al. (1975), the entropy is from Haselton

 and Westrum (1980) and the heat capacity is from Haselton (1979). The value

 are calorimetric. Thermal expansion checked against Skinner (1956).

 Compressibility data  of Halleck (1973) taken into consideration.

 REF_0025 NOTE:

     Enthalpy optimized by Zhang and Saxena (1991) on the basis of the follo

 reactions:

                 Ad = Woll + Mag + O2

                 Ad + Mag + Q = Hed + O2

                 Ad + Q = Hed + Woll + O2

                 Ad = Woll + Hem

     Volume is from the data base of Helgeson et al. (1978) (optimized).

 Other values are calorimetric. Thermal expansion and compressibility are

 as for grossular.

 REF_0026 NOTE: Calorimetric data: H: -4227.83+2.01;

 Charlu et al. (1978);  S: 199.3 +0.3, Robie et al. (1978).

 A reaction involving anorthite and grossular is as follows:

                       An = Gr + Ky + Q                            (a)

 This was studied by many workers. Koziol and Newton's (1988a) results

 constrains the boundary within tight reversal brackets. Gasparik's (1984c)

 results place the reaction boundary a few kbars above that of Goldsmith's

 (1980). Gasparik (1984b) also studied the following reaction for the silica

 unsaturated system:

                      Gr + Ky = An + Cor                          (b)

 For reactions involving anorthite, wollastonite and gehlenite see note

 under gehlenite.

     The following reaction is an important mechanism in the plagioclase-

 lherzolite to spinel-lherzolite transition

                      An + Fo = Sp + opx + cpx                    (c)

 This reaction was studied by Herzberg (1976) and Kushiro and Yoder (1966).

     The heat capacity of anorthite, as listed in Robie et al. (1978) upto

 1800K, shows an anomalous extrapolation above 1200K. In Chatterjee (1989),

 the data upto 1200 K are fitted to the Fei-Saxena equation for high-T

 extrapolation. The resulting equation gives very similar results when

 compared to the equation of Holland (1981). Entropy of anorthite is from

 Robie et al. (1978) and enthalpy is calculated from reaction (a).

     The low pressure equilibria of anorthite in the CaO-MgO-Al2O3-SiO2

 system (reaction (c)) are reproduced by the data recommended in this study.

 REF_0027 NOTE: Calorimetric data: H: -3929.56+1.71; S: 220.3 +0.4.

 Hemingway et al. (1981) (derived from aluminum avoidance model)

      The following reaction, studied by Holland (1979) relates jadeite

 and albite:

                           Ab = Jd + Q                                 (a)

     The free energies of albite and jadeite were evaluated by Hemingway et

 al. (1981). Holland (1979) also attempted to evaluate the free energy of

 albite on the basis of reaction (a). Hemingway et al.'s values on albite

 are based on a careful consideration of the low-albite->albite transition.

 Their values on jadeite and albite are thus consistent with both the

 transition and the reaction (a). However, they did not consider the

 effect of thermal expansion and bulk modulus of these two phases. When

 these two parameters are considered, their second model which assumes that

 the aluminum avoidance principle holds for albite fits the experimental

 equilibria the best. Thus, the values recommended by Hemingway et al.(1981)

 are adopted for albite.

 REF_0028 NOTE:

     All the values were determined through calorimetry.

 The experimental data on the transformation

                       a-quartz  =  b-quartz

 are available from Fenner (1913), Cohen and Klement (1967)

 and Mirwald and Massonne (1980). These data were used to estimate the

 data for beta-quartz.

 REF_0029 NOTE:

 The experimental data on the transformation

                       a-quartz  =  b-quartz

 are available from Fenner (1913), Cohen and Klement (1967)

 and Mirwald and Massonne (1980).

 REF_0030 NOTE:

    Akaogi and Navrotsky (1984), using new calorimetric data, calculated

 pphase relations in SiO2 (quartz, coesite and stishovite). Fei and

 Saxena (1986) started with the thermochemical data on quartz from

 Robie et al.(1978), and evaluated the thermochemical data on coesite

 and stishovite; these data were then combined with the phase equilibrium

 data for the quartz-coesite transformation (Bohlen and Boettcher, 1982),

 for the coesite-stishovite transformation (Yagi and Akimoto, 1976) and

 with the calorimetric data from Akaogi and Navrotsky (1984).

 REF_0031 NOTE:

    Akaogi and Navrotsky (1984), using new calorimetric data, calculated

 phase relations in SiO2 (quartz, coesite and stishovite). Fei and

 Saxena (1986) started with the thermochemical data on quartz from

 Robie et al.(1978), and evaluated the thermochemical data on coesite

 and stishovite; these data were then combined with the phase equilibrium

 data for the quartz-coesite transformation (Bohlen and Boettcher, 1982),

 for the coesite-stishovite transformation (Yagi and Akimoto, 1976) and

 with the calorimetric data from Akaogi and Navrotsky (1984). Data on

 thermal expansion and compressibility respectively are consistent with

 those of Ito et al. (1974) and Weidner et al. (1982).

 REF_0032 NOTE: Calorimetric data:      H: -1634.77+0.7         S: 81.03+0.68

                         Haas et al. (1981).

     The properties of wollastonite are as listed in Haas et al. (1981)

 and are closely similar to those of Charlu et al. (1981).

 REF_0033 NOTE:

     Hankey and Schuele's (1970) data on compressibility is consistent

 with the above.

 REF_0034 NOTE: Calorimetric data: H: -2587.77+1.73; S: 95.79+0.14.

 Robie and Hemingway (1984b).

     Several experiments on the following equilibria

                         andalusite = kyanite

                            kyanite = sillimanite

                        sillimanite = andalusite

 relating the three polymorphs have been performed. However, the results

 obtained by different workers are very different. Experiments were done by

 Evans (1965), Newton (1966, 1969), Althaus (1967), Richardson et al. (1968,

 1969) and Holdaway (1971). The reason behind this discrepancy is the small

 difference in the free energies of formation of the three polymorphs which

 leads to metastability.

     Robie and Hemingway (1984b) determined the heat capacities of the three

 aluminosilicates in the range 10-380K. The slopes of phase boundaries among

 these phases match the experimental data of Evans(1965), Newton (1966,1969)

 and Holdaway (1971). Robie and Hemingway concluded that since Evans's,

 Newton's and Holdaway's results are consistent with their independently

 derived calorimetric data, the equilibrium results of these three workers

 must be correct. The thermodynamic properties given by Robie and Hemingway

 are adopted here. Robie and Hemingway also concluded that Al and Si are

 ordered in sillimanite to at least 1100 K. The compressibility data is cons

 with the data of Brace et al. (1969).

 REF_0035 NOTE: Calorimetric data: H: -2596.01+1.7; S: 82.3 +0.13.

 Robie and Hemingway (1984b).

 See note on sillimanite

 REF_0036 NOTE: Calorimetric data: H: -2591.9 +1.72; S: 91.39+0.14.

 Robie and Hemingway (1984b). See note on sillimanite.

 REF_0037 NOTE: Calorimetric data: H: -3296.62+1.63;

 Charlu et al. (1978);  S: 135.3, Haselton et al. (1984).

     Ca-Tschermak is related to grossular and anorthite by the following

 equilibrium reactions:

                           Gr + Cor = CaTs                             (a)

                         An + Ge + Cor = CaTs                          (b)

 Reaction (a) was studied by Gasparik (1984b), Hays (1966) and Wood (1978),

 and reaction (b) was studied by Hays (1966).

     Free energy of Ca-Tschermak was calculated by Saxena and Chatterjee(198

 using Gasparik's (1984b) data on reaction (a) and (b) which yielded

                   del-C'p = 2220824 (+/-130) / T2

 with a corresponding del-Hf(298) of -3300902 J/mol, where, del-C'p is the

 difference between the experimental and the calculated heat capacities.

 This del-Hf(298) is comparable to -3297994 J/mol (calculated from

 del-Hf(970)) determined by Charlu et al. (1978). The enthalpy and entropy

 needed adjustment in this study while the heat capacity of Saxena and

 Chatterjee (1986) is retained. The data on Cp listed above represents the

 addition of del-C'p to the Cp expression of Haselton et al. (1984).  Thermal

 expansion data is consistent with that of Haselton et al. (1984).

 REF_0038 NOTE: Calorimetric data: H: -9161.52+5.85; S: 407.2 +3.8.

 Robie et al. (1978).

     The upper stability limit of Mg-cordierite is given by the following

 reaction studied by Seifert (1974) and more recently by Herzberg (1983):

                          Cord + Fo = En + Sp                           (a)

 This reaction is influenced by Al solubility in enstatite.

     The heat capacity of cordierite is from Robie et al. (1978). The

 enthalpy and entropy are adjusted within the error limits of Robie et al.

 to fit the experimental data on reaction (a). Enstatite is considered an

 ideal solution between MgSiO3 and Al2O3.

 REF_0039 NOTE:

     Experimental data on the distribution of Fe and Mg between garnet and

 cordierite were obtained by Hensen and Green (1973), Holdaway and Lee (1977

 and Perchuk and Lavrent'eva (1983). The reaction is as follows:

                     Fe-cord + Pyr = Cord + Alm                        (a)

 The equation given below represents the average of all the experimental

 data:

                     LnKd = 3039.06/T(K) - 1.242                       (1)

 where, Kd is the distribution coefficient.

     The free energy and volume of Fe-cordierite and the interaction

 parameters of the cordierite-ferrocordierite solution are calculated

 assuming del-Cp of reaction (a) as zero and from the following

 equilibrium relation:

               del-G (o) (P,T) + RT LnKd + RT LnKgamma = 0             (2)

 the only unknown quantity in the term del-G (o) (P,T) being the free energy

 of ferrocordierite at P and T; and in the Kgamma term, the activities of

 cordierite and ferrocordierite; and where, LnKd is given by equation (1).

 REF_0040 NOTE:

     The data on Fe-perovskite are estimated from limited solution data and

 from analog with other related phases (Fei and Saxena, 1986).

     The Mg-Fe distribution data between coexisting magnesiowustite and

 perovskite and the maximum solubility of FeSiO3 in perovskite, determined

 by Yagi et al. (1979), Ito (1984) and Fei (1989)  are

 taken into consideration in the evaluation.

 REF_0041 NOTE:

     The phase relations for the three Mg2SiO4 polymorphs (olivine,

 beta-phase and spinel) have been experimentally investigated by

 Ringwood and Major (1970), Suito (1972), Suito (1977), Kawada (1977),

 Ohtani (1979), Fukizawa (1982), Sawamoto (1986), and Katsura and Ito(1989).

 The calorimetric data for the olivine/beta-phase transition were

 determined by Akaogi et al. (1984).

     The data on beta-phase and spinel were evaluated from the

 olivine/beta-phase transition by Katsura and Ito (1989) and beta/spinel

 transition by Katsura and Ito (1989) (1473-1873 K) and by Sawamoto (1986)

 (1873-2373 K), combined with the calorimetric data by Akaogi et al. (1984)

 and Akaogi et al. (1989) (see Fei et al., 1989 for discussion).

 REF_0042 NOTE:

     Beta-fayalite is a fictive component in the system. Its thermochemical

 and thermophysical properties are either extrapolated from limited solution

 data or estimated by using analog (Fei and Saxena, 1986). The data on

 H1000 and S1000 of the olivine-beta transition as estimated by

 Akaogi et al. (1989) were used as additional constraints in the data

 evaluation (see Fei, 1989).

 REF_0043 NOTE:

     The phase relations for the three Mg2SiO4 polymorphs (olivine,

 beta-phase and spinel) have been experimentally investigated by

 Ringwood and Major (1970), Suito (1972), Suito (1977), Kawada (1977),

 Ohtani (1979), Fukizawa (1982), Sawamoto (1986), and Katsura and Ito(1989).

 The calorimetric data for the olivine/beta-phase transition were

 determined by Akaogi et al. (1984).

     The data on beta-phase and spinel were evaluated from the

 olivine/beta-phase transition by Katsura and Ito (1989) and beta/spinel

 transition by Katsura and Ito (1989) (1473-1873 K) and by Sawamoto (1986)

 (1873-2373 K), combined with the calorimetric data by Akaogi et al. (1984)

 and Akaogi et al. (1989) (see Fei et al., 1990 for discussion). The thermal

 expansion is consistent with the data of  Suzuki et al. (1979).

 REF_0044 NOTE:

      The olivine-spinel transition in Fe2SiO4 has been experimentally

 studied using the quench technique (Akimoto et al., 1965, 1967) and using

 the in-situ X-ray diffraction method (Inoue, 1975; Sung and Burns, 1976;

 and Furnish and Bassett,1983). Very recently, Yagi et al.(1987) determined

 the equilibrium phase boundary between 1073 and 1473 K using a cubic anvil

 type of high pressure and high temperature X-ray diffraction apparatus

 combined with synchrotron radiation. The transition pressure

 P(GPa) = 3.43 + 0.0025T(K).

 The enthalpy and entropy for Fe2SiO4 spinel were evaluated from the phase

 equilibrium data (Yagi et al., 1987), constrained by the calorimetric data

 on H1000 and S1000 of the olivine-spinel transition as obtained by

 Akaogi et al. (1989).

 REF_0045 NOTE:

      For the magnesiowustite solid solution, MgO (periclase) was chosen

 to mix as a third component with FeO and FeO1.5 (see wustite FeO-FeO1.5). T

 data on thermal expansion and compressibility respectively are consistent w

 those of Suzuki (1975), Jackson and Niesler (1982) and Anderson and Zhou (1989)
.

 REF_0046 NOTE:

   Wustite has a temperature-composition field within which its composition

 varies mainly between Fe0.947O and Fe0.85O. The system may be modeled by

 considering wustite as a solid solution of two fictive, isostructural

 components FeO and FeO1.5. A precise model for the wustite solid solution

 particularly for modeling the crystal chemical behavior must include the

 effect of additional components (other than FeO and FeO1.5) and other

 parameters discussed by Hazen and Jeanloz (1984).

      The reaction within the field of wustite solution is

                      {FeO} + 0.25O2 = {FeO1.5}

 and in the field towards magnetite, the reaction may be conceived as

                   {5FeO} + O2 = {2FeO1.5} + Fe3O4

 where the brackets denote the components in the wustite solution.

 The computed Wij values for wustite are (FeO = 1, FeO1.5 = 2):

                   W12 = -7229, W21 = -2142 (J/mol)

 which are the same as in Bjorkman (1984).

 [continued in NOTE for WUSTITE(FEO)]

 REF_0047 NOTE:

   Wustite has a temperature-composition field within which its composition

 varies mainly between Fe0.947O and Fe0.85O. The system may be modeled by

 considering wustite as a solid solution of two fictive, isostructural

 components FeO and FeO1.5. A precise model for the wustite solid solution

 particularly for modeling the crystal chemical behavior must include the

 effect of additional components (other than FeO and FeO1.5) and other

 parameters discussed by Hazen and Jeanloz (1984).

      The reaction within the field of wustite solution is

                      {FeO} + 0.25O2 = {FeO1.5}

 and in the field towards magnetite, the reaction may be conceived as

                   {5FeO} + O2 = {2FeO1.5} + Fe3O4

 where the brackets denote the components in the wustite solution.

 The computed Wij values for wustite are (FeO = 1, FeO1.5 = 2):

                   W12 = -7229, W21 = -2142 (J/mol)

 which are the same as in Bjorkman (1984).

 [continued in NOTE for WUSTITE(FEO)]

 REF_0048 NOTE:

     Magnetite transforms to its high-pressure polymorph at pressure of

 about 25 GPa at room temperature (Mao et al., 1974). The magnetite and

 high-pressure magnetite boundary was determined to have a negative slope

 (dT/dP = -45 K/GPa, Huang and Bassett, 1986). Shock-wave data indicate

 that hematite transforms to its high-pressure polymorph below pressure of

 60GPa. The transition also was not observed in the diamond-anvil cell below

 30 GPa (Mao and Bell, 1977). Some physical properties of these phases are

 available (e.g. Mao et al., 1974; Ahrens et al., 1969; Finger et al., 1986;

 Wilburn et al., 1978; Sato and Akimoto, 1979; and Finger and Hazen, 1980).

 Thermochemical data for magnetite and hematite are from Haas

 (see Fei and Saxena, 1986).

 REF_0049 NOTE:

     Magnetite transforms to its high-pressure polymorph at pressure of

 about 25 GPa at room temperature (Mao et al., 1974). The magnetite and

 high-pressure magnetite boundary was determined to have a negative slope

 (dT/dP = -45 K/GPa, Huang and Bassett, 1986). Shock-wave data indicate

 that hematite transforms to its high-pressure polymorph below pressure of

 60GPa. The transition also was not observed in the diamond-anvil cell below

 30 GPa (Mao and Bell, 1977). Some physical properties of these phases are

 available (e.g. Mao et al., 1974; Ahrens et al., 1969; Finger et al., 1986;

 Wilburn et al., 1978; Sato and Akimoto, 1979; and Finger and Hazen, 1980).

 Thermochemical data for magnetite and hematite are from Haas

 (see Fei and Saxena, 1986).

 REF_0050 NOTE:

     Magnetite transforms to its high-pressure polymorph at pressure of

 about 25 GPa at room temperature (Mao et al., 1974). The magnetite and

 high-pressure magnetite boundary was determined to have a negative slope

 (dT/dP = -45 K/GPa, Huang and Bassett, 1986). Shock-wave data indicate

 that hematite transforms to its high-pressure polymorph below pressure of

 60GPa. The transition also was not observed in the diamond-anvil cell below

 30 GPa (Mao and Bell, 1977). Some physical properties of these phases are

 available (e.g. Mao et al., 1974; Ahrens et al., 1969; Finger et al., 1986;

 Wilburn et al., 1978; Sato and Akimoto, 1979; and Finger and Hazen, 1980).

 Thermochemical data for magnetite and hematite are from Haas

 (see Fei and Saxena, 1986).

 REF_0051 NOTE:

     Magnetite transforms to its high-pressure polymorph at pressure of

 about 25 GPa at room temperature (Mao et al., 1974). The magnetite and

 high-pressure magnetite boundary was determined to have a negative slope

 (dT/dP = -45 K/GPa, Huang and Bassett, 1986). Shock-wave data indicate

 that hematite transforms to its high-pressure polymorph below pressure of

 60GPa. The transition also was not observed in the diamond-anvil cell below

 30 GPa (Mao and Bell, 1977). Some physical properties of these phases are

 available (e.g. Mao et al., 1974; Ahrens et al., 1969; Finger et al., 1986;

 Wilburn et al., 1978; Sato and Akimoto, 1979; and Finger and Hazen, 1980).

 Thermochemical data for magnetite and hematite are from Haas

 (see Fei and Saxena, 1986).

 REF_0052 NOTE:

 REF_0053 NOTE:

     Kato and Kumazawa (1985, 1986) reported that garnet phase of MgSiO3 is

 stable at very high temperature. It is tetragonal,but a cubic form may also

 exist and cubic(majorite) garnet solid solution between Mg4Si4O12 (4MgSiO3)

 and Mg3Al2Si3O12 (pyrope) are reasonably well documented (Ringwood, 1967;

 Akaogi and Akimoto, 1977; Liu, 1977; Akaogi et al, 1987). Akaogi et al.(198

 estimated the enthalpy of the pyroxene-cubic garnet transition as 36.5 KJ

 (per mole MgSiO3) and the bulk modulus of cubic garnet as 154GPa (assuming

 K' = 4.0) from enthalpies of solution and volume compression along the

 Mg4Si4O12-Mg3Al2Si3O12 join. Their extrapolated molar volume for cubic

 garnet is 28.50 cm3/mole (MgSiO3), slightly larger than volumes near 28.1

 to 28.2 cm3/mole for tetragonal garnet (Kato and Kumazawa, 1985, 1986).

 Because the enthalpy of the cubic-tetragonal transition are unknown, we

 shall use data for the cubic phase in subsequent calculations. Lacking

 thermal expansion data, we assume a the same as for pyrope (Leitner et al.,

 1980). Heat capacities for MgSiO3 garnet are unavailable. One can either

 use values estimated from vibrational calculations or those for pyrope;

 both are similar.

 REF_0054 NOTE:

   The bulk modulus and elasticity for MgSiO3 ilmenite have been reported by

 Weidner and Ito (1985) and heat capacity at 300-600 K has been measured by

 Watanabe (1982). Recently Ashida et al. (1988) have measured heat capacity

 over a somewhat wider range (160 - 550 K) and the thermal expansion at

 295-875 K. McMillan and Ross (1987) calculated the entropy and heat capacit

 at 0-1800K using vibrational models. All these estimates of Cp are in close

 agreement. We evaluated the enthalpy and entropy of ilmenite from phase

 equilibrium data for the reaction, spinel + stishovite = ilmenite

 (Ito and Navrotsky, 1985) and for the ilmenite-perovskite transition by

 Ito and Takahashi (1989), P(GPa) = 27.5-0.0025 T(K), a slightly lower curve

 than previously determined (Ito and Yamada,1982). Since the data for ilmeni

 have to be consistent with both transformations, very little adjustment can

 be done to the ilmenite data. The calculated enthalpy of the

 pyroxene-ilmenite transition at 298 K (59.9 kJ/mol) is in good agreement

 with the new calorimetric value of 59.03+4.26 kJ/mol (Ashida et al., 1988)

 which revises the earlier prilimenary calorimetric value of 71.8 kJ/mol

 (Ito and Navrotsky, 1985).

 REF_0055 NOTE:

     Data for MgSiO3 perovskite include estimates of compression by X-ray

 diffraction (Yagi et al., 1982; Kudoh et al., 1987) and from elasticity

 (Yeganeh-Haeri et al.,1989) and of thermal expansion (Knittle et al.,1986).

 The reactions ilmenite = perovskite and spinel = perovskite + periclase

 have been studied by Ito and Yamada (1982) and recently by Ito and Takahash

 (1989). Both these transitions appear to have negative P-T slopes. No Cp

 measurements have been reported but an estimate of Cp from vibrational

 models (Fei et al., 1989). Recently Ito, Akaogi and Navrotsky (Navrotsky,

 pers. comm.) attempted to measure the enthalpy of the perovskite by drop

 solution calorimetry. They obtained a value of H(ilmenite - perovskite) in

 the range 40 - 60 kJ/mol; the large uncertainty reflecting the presence of

 significant amounts of other phases in the sample. Vibrational calculations

 support that the entropy of the ilmenite-perovskite transition is positive,

 implying a negative dP/dT, but they suggest that S may depend quite

 strongly on temperature. Thermal expansion is consistent with the data

 of Knittle et al. (1986).

 REF_0056 NOTE: Calorimetric data: H: -3959.56+3.37, S: 232.9 +0.48, Robie et al
. (1978).

 The equilibrium relations between sanidine and muscovite have been

 studied by many workers. Important reactions are as follows:

                       Ms = Cor + San + H2O                        (a)

                    Ms + Q = San + Al2SiO5 + H2O                   (b)

 Experimental work has been done on (a) by Velde (1966) and Chatterjee and

 Johannes (1974) and on (b) by Evans(1965), Althaus et al.(1970), Day (1973)

 and Chatterjee and Johannes (1974).

     Krupka et al.(1979) attempted to calculate the enthalpy and free energy

 energy of muscovite from the experimental data of Chatterjee and Johannes o

 the above reactions. Their calculations were based on the fugacity values

 of steam from Chatterjee and Johannes and Fisher and Zen (1971) and the Cp

 muscovite determined by them and the unpublished data on sanidine listed in

 Robie et al.(1978). Here, the more general equation for water fugacity of

 Saxena and Fei (1987a,b) and the published Cp data on sanidine by Hemingway

 et al.(1981) are used. The enthalpy of sanidine is from Robie et al.(1978).

 The thermal expansion of muscovite is also optimized from a combination of

 the phase equilibrium and Cp data. The optimized S of sanidine is found to

 be 7.09 J/mol-K higher than that determined by Openshaw et al.(1976). This

 amount can be considered as the disorder S of sanidine. Sanidine shows an

 Al/Si disorder and since, at very low temperatures, its Cp is not well

 characterized, this treatment is reasonable. However, it should be kept in

 mind that the zero-point Al/Si disorder S of muscovite is also unknown.

 REF_0057 NOTE: Not evaluated.

 REF_0058 NOTE: Not evaluated.

 REF_0059 NOTE:    Reversed distribution data of Fe and Mg between biotite and g
arnet

 are available from Ferry and Spear (1978) and Perchuk and Lavrent'eva (1983

 These data are used to calculate the free-energy and volume data of annite

 and the solution properties of the biotite solution. The relevant reaction

 is as follows:         Alm + Phl = Pyr + Ann                         (a)

 The values for annite and the solution parameters are calculated assuming

 del-Cp of reaction (a) as zero and from the following relation:

               del-G (o) (P,T) + RT LnKd + RT LnKgamma = 0

 the only unknown quantities in the term del-G (o) (P,T) being the enthalpy,

 entropy and volume of annite at P and T and where, Kd is from Ferry and

 Spear or Perchuk and Lavrent'eva.

     When the data of Ferry and Spear and Perchuk and Lavrent'eva are used

 together, convergence is not achieved. It is concluded that the two sets of

 data are inconsistent. When only the data of Ferry and Spear are used,the f

 obtained is not satisfactory. Also,the solution parameters obtained suggest

 an extremely asymmetric solution. This could be due to the fact that the

 data are only in the Fe-rich end of the binary. When only the data of

 Perchuk and Lavrent'eva are used, a much better fit is obtained. Thus, thei

 data are used in the calculations. An uncertainty of 700 J is found in the

 enthalpy of annite.

 REF_0060 NOTE: Calorimetric data:      H: -6203.9 +6.73        S: 334.6 +1.0

   H, Clemens et al.(87) (derived indirectly); S, Robie & Hemingway (84a).

 Enthalpy of phlogopite was determined by Clemens et al. (1987) by

 solution calorimetry. Their value of -6215.33 KJ/mol was derived by

 considering a calorimetric cycle for the reaction:

                         Per + Br + San = Phl                        (3.aa)

 and using the free energies of periclase, brucite and sanidine from Robie

 et al. (1978) and the heat capacity of phlogopite from Robie and Hemingway

 (1984a). The same procedure is repeated here. A different value for the

 enthalpy of phlogopite is obtained for the following reason. Saxena (1989b)

 and Fei and Chatterjee (1988) using the experimental data on the reaction

                             Br = Per + H2O

 from Irving et al. (1977), which are upto a temperature of 1400 K, obtained

 an optimized heat capacity expression for brucite. The heat capacities of

 brucite obtained from this expression differ from the original data of King

 et al.(1975) (used by Clemens et al.) by 0.8 and 1.35J/mol at 500 and 700K.

 The entropy of phlogopite is from Robie and Hemingway(1984a). This includes

 a configurational entropy of 18.7 J/mol.K assuming total Al-Si disorder

 REF_0061 NOTE:

     For the reaction

                       Cord + H2O = Hydrous-cord

 Bhattacharya and Sen (1985) give the following relations in the range

 773-1073 K:

         del-G (solids) (1,T) = - 271018.6 + 134.976xT  J/mol

    del-V (solids) (1,T) = - 3.7656x10andU.-3andD.xT - 2.1514  J/bar/mol

 Using these relations, the enthalpy, entropy, molar volume and thermal

 expansion of hydrous cordierite are calculated. The heat capacity is

 assumed to be the same as that of cordierite.

 REF_0062 NOTE: Calorimetric data: H: -924.5 +1.4,S: 63.18+0.13,Robie et al. (19
78).

    The equilibrium data on the following reaction were determined by Barnes

 and Ernst (1963), Irving et al. (1977) and Schramke et al. (1982):

                           Br = Per + H2O                              (a)

    Experimental data on this reaction are used to determine the free energy

 of brucite. The heat capacity of brucite are available up to a temperature

 of 700 K (King et al.,1975). The equilibrium data of Irving et al. are upto

 a temperature of approximately 1400 K. Thus, it is necessary to extrapolate

 the heat capacity using the Fei-Saxena formulation.  Enthalpy, entropy, the

 expansion and bulk modulus of brucite are optimized from the experimental

 data.

 REF_0063 NOTE: Calorimetric data: H: -5976.74+3.24,S: 306.4 +0.61,Robie et al. 
(1978).

 The equilibrium relations between sanidine and muscovite have been

 studied by many workers. Important reactions are as follows:

                       Ms = Cor + San + H2O                        (a)

                    Ms + Q = San + Al2SiO5 + H2O                   (b)

 Experimental work has been done on (a) by Velde (1966) and Chatterjee and

 Johannes (1974) and on (b) by Evans(1965), Althaus et al.(1970), Day (1973)

 and Chatterjee and Johannes (1974).

     Krupka et al.(1979) attempted to calculate the enthalpy and free energy

 energy of muscovite from the experimental data of Chatterjee and Johannes o

 the above reactions. Their calculations were based on the fugacity values

 of steam from Chatterjee and Johannes and Fisher and Zen (1971) and the Cp

 muscovite determined by them and the unpublished data on sanidine listed in

 Robie et al.(1978). Here, the more general equation for water fugacity of

 Saxena and Fei (1987a,b) and the published Cp data on sanidine by Hemingway

 et al.(1981) are used. The enthalpy of sanidine is from Robie et al.(1978).

 The thermal expansion of muscovite is also optimized from a combination of

 the phase equilibrium and Cp data. The optimized S of sanidine is found to

 be 7.09 J/mol-K higher than that determined by Openshaw et al.(1976). This

 amount can be considered as the disorder S of sanidine. Sanidine shows an

 Al/Si disorder and since, at very low temperatures, its Cp is not well

 characterized, this treatment is reasonable. However, it should be kept in

 mind that the zero-point Al/Si disorder S of muscovite is also unknown.

 REF_0064 NOTE: Calorimetric data:  S: 3598.53+26.78, King et al. (1967).

     The stability of antigorite is defined by the following reaction:

                        Ant = 18Fo + 4Tc + 27H2O

 The equilibria for this reaction were experimentally determined by Evans et

 al. (1976). These data are used to optimize the free energy of antigorite.

 The heat capacity of antigorite was measured up to a temperature of 850 K

 by King et al. (1967). The optimized parameters for antigorite include

 enthalpy, entropy, thermal expansion and bulk modulus.

 REF_0065 NOTE: Calorimetric data: H: -5949.33+4.6, S: 277.1 +0.9,Robie and Hemi
ngway (1984a)

 (derived from ordered model).

     Reactions involving jadeite, albite and paragonite are as follows:

                        Pg = Ab + Cor + H2O                         (a)

                    Pg + Q = Ab + Al2SiO5 + H2O                     (b)

                         Pg = Jd + Ky + Q                           (c)

 Experimental work has been done on reaction (a) by Chatterjee (1970); on

 reaction (b) by Chatterjee (1972) and on reaction (c) by Holland (1979).

     Using the entropy of paragonite from Robie and Hemingway (1984a), the

 enthalpy and heat capacity of paragonite are optimized. The thermal

 expansion and bulk modulus are also optimized simultaneously. The resulting

 value of the bulk modulus was not different from that of muscovite.

 The values listed above perfectly reproduce the reactions (a), (b) (for

 sillimanite and andalusite) and (c).

 REF_0066 NOTE:

    Calculated from the experimental data on Mg-Fe exchange between

 olivine and (Mg,Fe)-grunerite reaction from Miyano and Klein (1983):

                         Cumm + Fay = Grun + For

 They give the following equilibrium relation:

                         LnKd = -2328.2/T(K) + 1.27

 REF_0067 NOTE:

     The grunerite breakdown reaction was studied by Mel'nik and Radchuk

 (1977) and Forbes(1977). Their results agree at the WM buffer. The reaction

 is as follows:

                         Grun = Fay + Q + H2O

     Experimental data on the above reaction are used to optimize the free

 energy of grunerite. Miyano and Klein (1983) determined the free energy

 of grunerite by the same method. However, since they used different free

 energy values of fayalite and quartz than the values used in this study,

 the procedure had to be repeated. Their heat capacity equation is accepted

 in this work while calculating the enthalpy and entropy of grunerite. The

 molar volume of grunerite is from Klein and Waldbaum (1967).

 REF_0068 NOTE: Calorimetric data: H: -12086.0 +7.5, Weeks (1955);

  S: 537.0 +2.7, Krupka et al. (1985a).

     The stability limits of anthophyllite and talc were recently

 studied in detail by Chernosky et al. (1985). The following

 reactions were studied:

                       Anth = 7En + Q + H2O

                       Anth + Fo = 9En + H2O

                       Tc + 4En = Anth

                       9Tc + 4Fo = 5Anth + 4H2O

                       7Tc = 3Anth + 4Q + 4H2O

 Experimental data on these five reactions from many sources are used to

 optimize the thermodynamic properties of anthophyllite. Heat capacity data

 on anthophyllite in the temperature range 300-700 K from Krupka et al.

 (1985a,b) are also included in the optimization of thermal expansion and

 bulk modulus.

 REF_0069 NOTE: Calorimetric data:      H: -5915.9 +4.33,Robie et al. (1978);

 S: 260.79+0.4, Robie and Stout (1963).

     The stability limit of talc was recently studied in details by

 Chernosky et al. (1985). The following reactions studied involve talc

 exclusively:

                          Tc = 3En + Q + H2O                          (a)

                          Tc + Fo = 5En + H2O                         (b)

 At first, experimental data on these two reactions from many sources are

 used to optimize the thermodynamic data on talc. It was found that the

 phase equilibrium data on the two reactions are not consistent with each

 other. There is no way to adjust thermodynamic data on talc to fit the

 experimental data on both reactions simultaneously. Thus, the higher

 temperature reaction (a) is chosen to optimize the properties of talc.

 The reason behind this choice is that this reaction is less influenced

 by kinetic factors. Thus values presented here do not reproduce the

 experimental data of Kitihara et al. (1966) on reaction (b).

     The heat capacity of talc are in the temperature range 300-700K and are

 from Krupka et al. (1985a,b). These measured data are also included in the

 optimization of thermal expansion and bulk modulus.

 REF_0070 NOTE: Calorimetric data: H: -4364.3 +3.4,S: 221.33+1.67,King et al. (1
967).

     The following reactions involve chrysotile:

                    Chr + Br = 2Fo + 3H2O

                    5Chr = 6Fo + Tc + 9H2O

 The experimental data on these two reactions are from Kitihara et al.

 (1966), Johannes (1968) and Chernosky (1982).

     Experimental data on the above reactions are used to optimize the

 free energy of chrysotile. The data of some other workers at low pressures

 on the second reaction were also included in the analysis.

 REF_0071 NOTE: Calorimetric data:      H: -1236.62+1.59, Robie et al. (1978);

   S: 108.9 +0.5, Anovitz et al. (1985).

   The following reactions involving rutile and ilmenite were experimentally

 reversed by Bohlen et al. (1983a) and Bohlen and Liotta (1986) respectively

                        Alm + Ru = Ilm + Ky + Q                      (a)

                        garnet + Ru = Ilm + An + Q                   (b)

 Reaction (b) involves the garnet composition Gr1Alm2.

     Enthalpy, entropy and Cp of rutile are calorimetric as given in

 Robie et al. (1978). Entropy and Cp of ilmenite are from Anovitz et al.

 (1985). The enthalpy and thermal expansion of ilmenite calculated from

 reaction (a) by optimization of experimental equilibrium data. The

 enthalpy obtained is within the error limits of the enthalpy given in

 Robie et al. (1978). The data on ilmenite thus obtained, along with the

 solution data on the Gr-Alm solution, reproduce the experimental data on

 reaction (b) well and the experimental data on the reaction

                         Ilm = Fe + Ru + O2                          (c)

 reasonably well.

 REF_0072 NOTE:

 Calorimetric data: H: -944.75+1.26,S: 50.29+0.17,Robie et al. (1978).

     All thermochemical data are from calorimetric sources. The

 compressibility and the thermal expansion data respectively are

 consistent with that of Grimsditch and Ramdas (1976) and  Fritz

 (1974) and as reported in Carmichael (1982).

 REF_0073 NOTE: Evaluated from the phase equilibrium data of Gasparik and Presna
ll (1990).

 REF_0074 NOTE: The experimental data on several reactions as used by Berman (19
88)

 (i.e.Walter,1963a,b, Yin and Greenwood, 1983) are used for the estimation of en
thalpy.

 REF_0075 NOTE: The data on magnesite have been evaluated by Trommsdorff and Con
nolly (1990).

 Their preferred value for enthalpy at 298.15 is -1111197.0. Such a value

 fits the reversals at low pressures and temperatures. We used additionally

 the phase equilibrium data at high P and T (Haselton et al.,1978, Eggler et al.
,

 1979, Newton and Sharp, 1975, Harker and Tuttle, 1955, Goldsmith and Heard, 196
2,

 and Irwing and Wyllie, 1975) which lead to the adopted data.

 REF_0076 NOTE:

 REF_0077 NOTE:

 REF_0078 NOTE:

 REF_0079 NOTE:

 REF_0080 NOTE:

 REF_0081 NOTE:

 REF_0082 NOTE:

 REF_0083 NOTE:

 REF_0084 NOTE:

 REF_0085 NOTE:

 REF_0086 NOTE:

 REF_0087 NOTE:

 REF_0088 NOTE:

 REF_0089 NOTE:

 REF_0090 NOTE:

 REF_0091 NOTE:

 REF_0092 NOTE:

 REF_0093 NOTE:

 REF_0094 NOTE:

 REF_0095 NOTE:

 REF_0096 NOTE:

 REF_0097 NOTE:

 REF_0098 NOTE:

 REF_0099 NOTE:

 REF_0100 NOTE:

 REF_0101 NOTE:

 REF_0102 NOTE:

 REF_0103 NOTE: Not consistent with the other data!!

 REF_0104 NOTE:

 REF_0105 NOTE:

 REF_0106 NOTE:

 REF_0107 NOTE:

 REF_0108 NOTE:

 REF_0109 NOTE:

 REF_0110 NOTE:

 REF_0111 NOTE:

 REF_0112 NOTE:

 REF_0113 NOTE:

 REF_0114 NOTE:

 REF_0115 NOTE:

 REF_0116 NOTE:

 REF_0117 NOTE:

 REF_0118 NOTE:

 REF_0119 NOTE:

 REF_0120 NOTE:

 REF_0121 NOTE:

 REF_0122 NOTE:

 REF_0123 NOTE:

 REF_0124 NOTE:

 REF_0125 NOTE:

 REF_0126 NOTE:

 REF_0127 NOTE:

 REF_0128 NOTE:

 REF_0129 NOTE:

 REF_0130 NOTE:

 REF_0131 NOTE:

 REF_0132 NOTE:

 REF_0133 NOTE:

 REF_0134 NOTE:

     Free energy is from Bokreta (1989). The values were calculated from

 lattice energy consideration. Note that Cp is valid only upto 1300 K.

 REF_0135 NOTE:

 REF_0136 NOTE:

 REF_0137 NOTE:

 REF_0138 NOTE:

 REF_0139 NOTE:

 REF_0140 NOTE: Calorimetric data: H: -2299.38+0.75       S: 80.63+0.42

               H, Charlu et al. (1975); S, Robie et al. (1978)

     Experiments involving spinel, orthopyroxene and pyrope were done

 by Haselton (1979), Lane and Ganguly (1980), Danckwerth and Newton (1978)

 and Gasparik and Newton (1984) on the reaction:     En + Sp = Pyr + Fo

 Free energy of spinel is calculated from the above reaction. Heat capacity

 of spinel is from Robie et al. (1978). Enthalpy and entropy of spinel are

 adjusted in order to reproduce the above reaction. The adjusted entropy

 value (81.5 J/mol.K) lies close to the value in Robie et al. (1978) (80.63

 J/mol.K). However, the enthalpy value (del-Hf(970)-oxides = -30.659 KJ/mol)

 is much lower than the calorimetric value (del-Hf(970)-oxides=-22.51+/-0.75

 KJ/mol) of Charlu et al. (1975). Wood and Holloway (1984) pointed out that

 Charlu et al. prepared their sample at 1698 K. Hence, the sample they used

 had a built-in Mg-Al disorder as the experiment was done at 970 K. The

 energy due to disorder is reflected in their result. Wood et al. (1986)

 studied the disordering behavior of spinel and concluded that above 1173 K

 disordering is negligible. Thus, the difference between the value of Charlu

 et al.(1975) and this study (appox 8 KJ/mol) could be due to the difference

 between the disorder state of spinel at 1173 K and 970 K. Thus, as also

 concluded by Wood & Holloway (1984), the enthalpy of spinel should be much

 less than the value of Charlu et al.(1975). The value obtained here is

 similar to that obtained by Wood and Holloway (1984).  The compressibility

 data (Saxena & Shen,1991) are consistent with that of Wang & Simmons(1972)

