MgO-SiO2
New end-members in this subsystem are clinohumite, antigorite and the high-pressure Phase A. Clinohumite data are fitted to the experiments of Duffy & Greenwood (1979) and Phase A to the experiments of Pawley & Wood (1996). The entropy of antigorite was estimated from Holland (1989), the volume was taken from Mellini et al. (1987), and the enthalpy was derived from fitting to the experiments of Evans et al. (1976). The experiments of Aranovich & Newton (1996) on dehydration of brucite have provided much more stringent constraints on the brucite enthalpy. Data for cummingtonite are now fitted to the experiments of Fonarev & Korolkov (1980), using the Fe-Mg order-disorder model in Holland & Powell (1996b). The experiments of Koziol & Newton (1995, 1997) and those of Johannes & Metz (1968) and Philipp & Girsperger (in Trommsdorff & Connolly, 1990) on magnesite decarbonation are now used, as well as those of Koziol & Newton (1995, 1997) on the reactions 2mag + en = 2fo + 2CO2 and 2mag + 2q = en + 2CO2.
18) ta + 2en = anth (Chernosky et al., 1985)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 - 10.0 755 780 8.39 8.79 3 783 18 1 (8.41 <-> 8.77)
cH = 8.85 (sd 0.15)
too high but OK
uH = 0.13, d/s = 1.6, h = 0.51
19) phA = 3br + 2fo (Pawley & Wood, 1995)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 - 27.5 26.0 500 10.88 11.54 26.67 2.27 3 (10.88 <-> 11.61)
0 - 34.8 32.5 600 11.04 11.95 34.29 2.63 cH = 11.24 (sd 0.51) 2
0 - 39.5 37.5 650 10.88 11.58 38.46 2.87 within bracket
uH = 0.30, d/s = 0.8, h = 1.00
20) br = per + H2O (Barnes & Ernst, 1963;)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 0.5 564 574 80.87 81.60 573 4 3 (81.10 <-> 81.80)
0 0 1.0 604 607 80.99 81.18 5 612 4 cH = 81.51 (sd 0.14) 2
0 0 1.5 633 648 81.31 82.16 637 6 within bracket
0 0 2.0 653 664 81.35 81.94 656 6 uH = 0.30, d/s = -0.3, h = 0.13
21) br = per + H2O (Aranovich & Newton, 1995)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 2.0 655 670 81.46 82.26 656 6 3 (81.23 <-> 81.86)
0 0 4.2 715 730 81.23 81.93 721 6 cH = 81.51 (sd 0.14)
0 0 7.0 770 790 80.98 81.82 783 8 within bracket
0 0 10.0 830 845 81.29 81.87 836 8 uH = 0.25, d/s = 0.0, h = 0.77
0 0 15.0 890 905 80.93 81.46 1 906 8
22) br = per + H2O (Schramke et al., 1981; Irving et al., 1977)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 4.0 690 725 80.29 81.93 716 6 1 (80.81 <-> 81.50)
0 0 5.1 720 745 80.50 81.62 743 6 cH = 81.51 (sd 0.14) 2
0 0 6.1 740 765 80.46 81.54 764 6 too high but OK
0 0 8.1 785 806 80.77 81.62 803 8 uH = 0.24, d/s = 1.6, h = 0.08
* br = per + H2O (Irving et al., 1977)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 17.0 915 945 80.99 82.02 930 8 ** NOT USED **
0 0 27.0 1020 1080 81.45 83.31 1022 10 cH = 81.51 (sd 0.14)
0 0 33.0 1075 1105 81.93 82.83 -14 1061 10
23) 2ta = 3en + 2q + 2H2O (Chernosky, 1976; Chernosky et al., 1985; Skippen, 1971)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 0.5 656 672 216.19 219.55 663 2 3 (217.26 <-> 219.44)
0 0 1.0 700 721 218.16 222.18 -3 697 2 cH = 217.66 (sd 0.27)
0 0 2.0 725 735 217.03 218.77 729 4 within bracket
uH = 0.93, d/s = 0.3, h = 0.10
24) 2ta = 3en + 2q + 2H2O (Chernosky et al., 1985)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 10.0 790 800 215.93 217.35 2 802 4 3 (214.48 <-> 216.14)
0 0 13.0 800 216.01 12 812 4 cH = 217.66 (sd 0.27)
0 0 13.6 785 213.80 814 4 too high
0 0 17.0 795 214.39 820 4 uH = 0.70, d/s = 0.1, h = 0.08
25) 2ta = 3en + 2q + 2H2O (Jenkins, Holland & Clare, 1991)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 25.0 800 820 214.34 216.78 7 827 4 1 (214.54 <-> 216.57)
0 0 28.0 770 210.69 829 4 cH = 217.66 (sd 0.27)
too high
uH = 0.61, d/s = 2.0, h = 0.05
* 2ta = 3en + 2coe + 2H2O (Pawley & Wood, 1995)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 29.0 800 820 224.96 227.28 10 830 6 ** NOT USED **
0 0 38.0 770 790 224.99 227.18 11 801 6 cH = 228.40 (sd 0.29)
0 0 49.0 730 224.48 38 768 6
26) 2fo + 2ta = 5en + 2H2O (Chernosky, 1976; Chernosky et al., 1985)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 0.5 600 621 198.70 202.93 619 2 3 (201.46 <-> 203.75)
0 0 1.0 652 657 203.38 204.29 -4 648 4 cH = 202.61 (sd 0.30)
0 0 2.0 650 677 199.44 203.85 669 4 within bracket
0 0 3.0 673 692 201.56 204.53 680 4 uH = 0.97, d/s = -0.2, h = 0.36
0 0 4.0 686 691 202.72 203.48 -1 685 4
0 0 6.0 679 694 201.21 203.36 689 4
27) 2anth = 7en + 2q + 2H2O (Chernosky & Autio, 1979)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 1.0 719 760 197.50 204.02 735 6 3 (199.00 <-> 200.74)
0 0 1.5 752 767 199.28 201.51 757 6 cH = 199.97 (sd 0.40)
0 0 2.0 765 775 199.10 200.51 771 6 within bracket
0 0 3.0 755 195.37 790 6 uH = 0.74, d/s = 0.8, h = 0.30
0 0 10.0 815 200.77 808 8
28) 7ta = 3anth + 4q + 4H2O (Chernosky & Autio, 1979)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 0.5 647 677 462.24 476.28 -1 646 2 3 (461.85 <-> 466.56)
0 0 1.0 664 687 456.41 466.24 677 4 cH = 461.87 (sd 0.70)
0 0 1.5 693 701 461.61 464.86 694 4 within bracket
0 0 2.0 706 719 461.90 467.02 706 4 uH = 2.00, d/s = 0.5, h = 0.22
0 0 3.0 727 742 462.72 468.39 -2 725 4
29) 2anth + 2fo = 9en + 2H2O (Chernosky et al., 1985)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 0.5 632 667 183.21 189.20 642 6 1 (183.29 <-> 185.32)
0 0 2.0 677 710 181.86 186.26 700 6 cH = 184.92 (sd 0.43)
0 0 4.0 677 181.26 708 8 within bracket
0 0 5.0 684 735 182.64 188.54 704 8 uH = 0.72, d/s = 1.5, h = 0.14
0 0 6.0 661 701 180.93 185.40 697 8
30) 9ta + 4fo = 5anth + 4H2O (Chernosky et al., 1985)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 1.0 625 645 450.19 458.97 -2 623 4 3 (447.63 <-> 453.25)
0 0 2.0 635 660 445.66 455.75 644 4 cH = 449.45 (sd 0.93)
0 0 5.0 665 685 445.49 452.89 676 6 within bracket
0 0 6.0 674 689 446.30 451.76 683 6 uH = 2.02, d/s = 0.4, h = 0.27
31) br + chr = 2fo + 3H2O (Johannes, 1968; Kitahara et al., 1966)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 1.0 350 370 212.99 216.17 358 4 1 (213.71 <-> 215.64)
0 0 3.0 380 400 213.26 215.80 388 6 cH = 214.29 (sd 0.52)
0 0 4.0 395 430 213.55 218.80 401 4 within bracket
0 0 7.0 415 440 212.60 216.31 427 8 uH = 0.61, d/s = 1.8, h = 0.48
0 0 18.2 450 520 210.33 219.40 481 8
0 0 27.3 460 520 209.12 216.39 503 10
32) 5chr = ta + 6fo + 9H2O (Chernosky, 1973)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 4.0 456 476 680.54 690.52 471 10 1 (682.38 <-> 689.97)
0 0 5.0 468 488 681.83 691.53 481 10 cH = 687.95 (sd 2.53)
within bracket
uH = 2.50, d/s = 1.7, h = 0.58
33) atg = 4ta + 18fo + 27H2O (Evans et al., 1976)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0 2.0 480 540 2122.22 2222.55 531 8 3 (2198.23 <-> 2217.92)
0 0 4.0 520 570 2144.07 2220.72 562 10 cH = 2208.07 (sd 7.18)
0 0 6.0 560 590 2173.44 2216.89 584 10 within bracket
0 0 10.0 615 630 2207.15 2227.17 616 10 uH = 7.17, d/s = 0.7, h = 1.00
0 0 15.0 640 660 2205.88 2230.75 642 12
34) 2cumm = 7en + 2q + 2H2O (Fonarev & Korolkov, 1980)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0.79 0 3.0 718 748 174.75 178.25 732 24 2 (174.66 <-> 178.07)
0.64 0 5.0 728 758 174.73 177.99 743 26 cH = 176.37 (sd 1.39)
within bracket
uH = 1.35, d/s = 1.2, h = 1.00
35) chum = 4fo + per + H2O (Duffy & Greenwood, 1979)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0.43 0 2.0 751 106.31 107.62 0.43 0.16 1 (106.37 <-> 107.56)
cH = 106.97 (sd 0.68)
within bracket
uH = 0.41, d/s = 1.6, h = 1.00
36) mag = per + CO2 (Harker & Tuttle, 1955; Goldsmith & Heard, 1962)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 1 0.7 730 750 116.38 118.48 731 4 3 (116.53 <-> 117.99)
0 1 1.4 800 825 116.74 119.17 -3 797 4 cH = 116.43 (sd 0.23)
0 1 2.1 800 875 112.30 119.23 845 6 too low but OK
0 1 2.8 875 900 115.59 117.81 885 6 uH = 0.52, d/s = 1.0, h = 0.19
0 1 3.0 952 121.43 895 6
0 1 5.0 977 1008 115.61 118.14 987 6
37) mag = per + CO2 (Johannes & Metz, 1968; Philipp & Girsperger, 1990; Koziol & Newton, 1995)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 1 0.5 680 710 113.91 117.18 703 4 3 (115.43 <-> 116.68)
0 1 1.0 740 760 114.14 116.16 3 763 4 cH = 116.43 (sd 0.23)
0 1 2.0 810 835 113.79 116.12 3 838 6 within bracket
0 1 0.5 700 710 116.09 117.18 703 4 uH = 0.53, d/s = -0.0, h = 0.44
0 1 0.6 0.6 715 115.86 116.75 0.58 0.03
0 1 1.0 760 770 116.16 117.17 763 4
* mag = per + CO2 (Irving & Wyllie, 1975)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 1 18.0 1350 1400 114.25 117.46 1384 8 ** NOT USED **
0 1 21.0 1420 1470 114.00 117.09 1459 8 cH = 116.43 (sd 0.23)
0 1 22.7 1520 117.59 1501 8
* 2mag + 2q = en + 2CO2 (Johannes, 1969)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 1 2.0 510 520 168.19 170.08 -3 507 4 ** NOT USED **
cH = 167.66 (sd 0.40)
38) 2mag + 2q = en + 2CO2 (Koziol & Newton, 1995)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 1 7.5 638 663 162.73 166.75 6 669 4 5 (166.59 <-> 170.42)
0 1 8.0 640 670 161.30 166.09 10 680 4 cH = 167.66 (sd 0.40)
0 1 10.6 10.2 715 164.81 166.00 -0.54 9.66 0.24 within bracket
0 1 12.0 750 782 166.11 170.90 760 6 uH = 1.02, d/s = -1.9, h = 0.38
0 1 14.0 801 820 168.35 171.12 -5 796 6
0 1 15.5 816 851 166.81 171.82 822 6
0 1 17.5 870 890 169.82 172.61 -15 855 6
* 2mag + 2coe = en + 2CO2 (Haselton et al., 1978)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 1 37.0 1120 1140 154.54 157.02 1139 6 ** NOT USED **
0 1 41.6 1185 1200 154.21 156.02 8 1208 6 cH = 156.93 (sd 0.41)
39) 2mag + en = 2fo + 2CO2 (Haselton et al., 1978; Koziol, 1994)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 1 8.0 740 780 177.06 183.45 775 6 3 (179.96 <-> 183.74)
0 1 10.0 810 830 179.53 182.60 1 831 6 cH = 182.72 (sd 0.41)
0 1 14.0 930 950 182.22 185.09 933 6 within bracket
0 1 17.6 1000 1020 179.94 182.67 1020 6 uH = 1.60, d/s = -0.3, h = 0.35
0 1 23.1 22.2 1125 179.87 182.47 -0.08 22.12 0.28
0 1 24.2 1150 1180 179.92 183.69 1172 6
0 1 28.7 1240 1280 178.79 183.56 1273 6
0 1 33.3 1380 1400 183.32 185.57 -5 1375 8
0 1 37.0 1450 1500 182.04 187.45 1456 8
40) ta + 5mag = 4fo + 5CO2 + H2O (Greenwood, 1967)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 0.40 2.0 540 562.57 -7 533 4 3 (563.93 <-> 572.63)
0 0.35 2.0 550 571.18 529 4 cH = 558.10 (sd 1.01) 2
0 0.75 2.0 560 563.61 -9 551 4 too low
0 0.73 2.0 586 579.20 550 4 uH = 3.11, d/s = 1.1, h = 0.01
0 0.51 2.0 560 570.17 540 4
41) 2wo + 2mont = di + merw (Yoder, 1968)
ln_K x(CO2) P(kbar) T(C) H(low) H(high) miss calc 2sd summary
0 - 6.0 6.7 740 24.97 26.20 6.04 0.27 1 (25.09 <-> 26.03)
0 - 6.2 7.0 700 24.84 26.25 6.32 0.27 cH = 25.04 (sd 0.24)
0 - 6.5 7.3 650 24.75 26.16 6.67 0.27 too low but OK
uH = 0.24, d/s = 2.5, h = 0.46
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