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Table 3 Representative chemical compositions of exsolved amphibole in garnet subgroups: B1 (amphibole lamella type), B3 (dense lamellae type), and B4 (clinopyroxene-amphibole lamellae type)

From: Hydrous Na-garnet from Garnet Ridge; products of mantle metasomatism underneath the Colorado Plateau

  Exsolved amphibole
Host garnet: (B) Cr-poor pyrope
Wt. % B1 B3 B4
SiO2 43.58 42.98 43.90 43.62 50.24 50.51
TiO2 0.35 0.33 1.09 0.97 0.23 0.19
Al2O3 16.13 16.38 18.25 16.71 8.65 8.93
Cr2O3 0.12 0.14 0.07 0.00 0.19 0.16
FeOa 2.21 2.49 3.97 3.75 2.40 2.38
CaO 12.64 12.37 9.33 11.54 9.37 9.12
MnO 0.03 0.00 0.03 0.02 0.00 0.02
MgO 18.00 18.12 15.71 17.18 20.67 20.48
NiO 0.76 0.38 0.36 0.34 0.13 0.09
Na2O 4.26 3.84 5.62 3.81 5.55 5.35
K2O 0.01 0.00 0.02 0.00 0.31 0.30
Cl 0.10 0.02 0.00 0.00 0.02 0.04
Total 98.18 97.05 98.36 97.94 97.77 97.57
Cations Number of cation based on 23 oxygen
Si 6.137 6.104 6.145 6.142 7.006 7.039
Ti 0.037 0.036 0.115 0.103 0.024 0.020
Al 2.677 2.742 3.011 2.774 1.422 1.467
Cr 0.013 0.016 0.008 0.000 0.021 0.018
Fe2+ 0.260 0.296 0.465 0.442 0.280 0.277
Ca 1.907 1.882 1.399 1.741 1.400 1.362
Mg 3.778 3.836 3.278 3.606 4.297 4.254
Mn 0.003 0.000 0.004 0.002 0.000 0.002
Ni 0.087 0.044 0.041 0.038 0.014 0.010
Na 1.163 1.057 1.525 1.040 1.501 1.446
K 0.001 0.000 0.004 0.000 0.054 0.053
Total 16.064 16.011 15.995 15.889 16.023 15.955
Cl 0.024 0.005 0.000 0.000 0.004 0.009
  1. aTotal Fe as FeO