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Table 2 Representative chemical compositions of pyrope from Garnet Ridge

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

  (A) Cr-rich pyrope (B) Cr-poor pyrope
B1 B2 B3 B4
Wt.% Amp Ilm-only Dense lamellae Cpx-Amp
SiO2 41.91 42.24 41.02 41.32 40.40
TiO2 0.09 0.05 0.14 0.10 0.06
Al2O3 22.30 23.36 21.66 23.01 22.72
Cr2O3 1.71 0.13 1.46 0.01 0.04
FeOa 8.80 9.26 13.82 14.49 19.7
MnO 0.36 0.38 0.54 0.41 0.45
MgO 19.31 18.75 15.81 15.85 13.33
CaO 5.43 5.99 5.43 4.93 3.41
Na2O 0.02 0.02 0.03 0.05 0.05
K2O 0.00 0.00 0.00 0.00 0.00
Total 99.92 100.18 99.91 100.17 100.15
Cations Number of cations on the basis of 12 oxygen
Si 3.000 3.009 3.007 3.007 3.001
Ti 0.005 0.003 0.008 0.006 0.003
Al 1.881 1.961 1.871 1.974 1.989
Cr 0.097 0.008 0.085 0.001 0.002
Fe3+ 0.019 0.023 0.034 0.016 0.004
Fe2+ 0.498 0.517 0.797 0.857 1.218
Mn 0.022 0.023 0.034 0.025 0.029
Mg 2.060 1.991 1.728 1.719 1.476
Ca 0.416 0.457 0.426 0.384 0.271
Na 0.002 0.002 0.004 0.007 0.006
K 0.000 0.000 0.000 0.000 0.000
Total 7.999 7.994 7.992 7.996 8.001
  1. aTotal Fe as FeO