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 |