CaO-FeO-Al2O3-SiO2
This subsystem includes the problematic relations involving andradite, epidotes and hedenbergite. It has not been possible to derive data which will satisfy all the experiments, probably because of the unknown extent of ferric and ferrous iron incorporation into wollastonites and ferric iron into hedenbergites in the experiments at high temperatures. However, the andradite data are consistent with the experiments of Huckenholz & Yoder (1971) for the reaction andr = 3pswo + hem, and of Gustavson (1974) and Moecher & Chou (1990) for the reaction 6andr = 4mt + 18wo + O2, as well as the data of Liou (1973) and Holdaway (1972) on coexisting epidotes and garnets in their epidote breakdown experiments. Reactions involving andradite with hedenbergite did not yield consistent data when compared with the exchange equilibria involving clino- and orthopyroxenes (see exchange section of table 7).
Ferroactinolite was derived from the experiments of Ernst (1966) on the reaction 2fact = 3fa + 5q + 4hed + 2H2O. These data are also nicely consistent with Fe-Mg exchange equilibrium seen in natural assemblages (see exchange section of table 7).
* gr + 2alm = 3fa + 3an (Bohlen et al., 1983)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
5.32 - 5.1 4.7 750 34.98 38.38 4.95 0.38 ** NOT USED **
5.32 - 5.2 4.8 800 37.99 41.39 0.20 5.40 0.38 cH = 36.25 (sd 1.62)
5.32 - 5.6 5.2 850 38.46 41.86 0.26 5.86 0.39
5.32 - 6.0 5.6 900 38.95 42.34 0.32 6.32 0.39
5.32 - 6.4 6.0 950 39.44 42.83 0.38 6.78 0.39
5.32 - 6.8 6.4 1000 39.96 43.34 0.44 7.24 0.39
5.32 - 7.1 6.7 1050 41.35 44.73 0.60 7.70 0.39
* gr + 2alm = 3fa + 3an (Perkins & Vielzeuf, 1992)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
5.32 - 6.4 6.0 900 35.56 38.95 6.32 0.39 ** NOT USED **
5.32 - 6.8 6.3 950 36.06 40.29 6.78 0.39 cH = 36.25 (sd 1.62)
5.32 - 7.1 6.6 1000 37.43 41.65 0.14 7.24 0.39
5.32 - 7.3 7.0 1050 39.66 42.19 0.40 7.70 0.39
243) 2hed = 2wo + fa + q (Lindsley & Munoz, 1969)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
-2.10 - 1.0 945 28.89 33.14 -2.11 0.26 1 (29.33 <-> 32.69)
cH = 31.11 (sd 1.34) 3
within bracket
uH = 0.59, d/s = 3.6, h = 0.05
244) 2fact = 3fa + 5q + 4hed + 2H2O (Ernst, 1966)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 1.0 452 465 167.10 169.16 28 493 16 4 (172.35 <-> 174.89)
0 0 2.0 498 509 172.79 174.45 503 18 cH = 173.61 (sd 1.33) 2
0 0 3.0 528 546 176.26 178.90 -18 510 18 within bracket
uH = 0.76, d/s = -4.6, h = 0.98
245) andr = 3pswo + hem (Huckenholz & Yoder, 1971)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 - 0.0 1130 1150 58.92 59.93 1139 16 1 (59.00 <-> 59.84)
cH = 59.35 (sd 0.38) 2
within bracket
uH = 0.25, d/s = 2.0, h = 0.16
246) 6andr + 3fa = 6mt + 18wo + 3q (Gustavson, 1974)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 - 0.5 740 760 203.48 210.61 743 12 3 (203.43 <-> 207.96)
0 - 1.0 760 773 204.04 208.68 761 12 cH = 204.47 (sd 2.13) 2
0 - 2.0 785 797 199.86 204.14 1 798 12 within bracket
uH = 1.83, d/s = 0.0, h = 0.42
247) 6andr + 2Ni = 4mt + 18wo + 2NiO (Gustavson, 1974)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 - 0.5 785 800 253.88 259.09 787 12 3 (252.30 <-> 257.15)
0 - 1.0 795 815 251.37 258.32 805 12 cH = 254.67 (sd 2.13) 2
0 - 2.0 825 840 249.85 255.06 839 12 within bracket
uH = 1.77, d/s = 0.3, h = 0.40
248) 6andr = 4mt + 18wo + O2 (Moecher & Chou, 1990)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
-29.84 - 2.0 840 860 733.21 739.89 840 6 2 (732.02 <-> 741.08)
cH = 733.56 (sd 2.10) 2
within bracket
uH = 3.84, d/s = 0.9, h = 0.05
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