Table 5 Electron-microprobe analyses* of tourmaline from hematite–talc schist

wt.% / 1 / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10 / 11 / 12 / 13
B2O3 / 10.76 / 10.59 / 10.79 / 10.60 / 10.94 / 10.61 / 10.55 / 10.60 / 10.52 / 10.59 / 10.62 / 10.69 / 10.51
SiO2 / 36.85 / 36.43 / 37.03 / 35.87 / 37.64 / 36.00 / 36.27 / 35.97 / 35.99 / 36.22 / 36.16 / 36.64 / 36.12
Al2O3 / 31.06 / 29.21 / 31.76 / 29.71 / 32.07 / 28.58 / 29.90 / 29.64 / 28.16 / 28.35 / 30.16 / 31.36 / 29.58
TiO2 / <0.17 / <0.14 / <0.13 / <0.14 / <0.15 / <0.14 / <0.15 / <0.14 / <0.16 / <0.15 / <0.13 / <0.13 / <0.14
FeO(t) / 5.78 / 8.74 / 5.02 / 8.60 / 5.26 / 8.92 / 7.50 / 8.26 / 9.27 / 9.59 / 7.82 / 5.05 / 8.07
MnO / 0.07 / 0.09 / 0.06 / 0.09 / 0.06 / 0.09 / <0.06 / 0.08 / 0.08 / 0.09 / 0.08 / 0.07 / 0.06
MgO / 9.76 / 8.81 / 9.69 / 8.92 / 9.76 / 9.60 / 8.89 / 9.15 / 9.26 / 9.16 / 8.95 / 9.63 / 8.69
CaO / 0.37 / 0.78 / 0.23 / 0.80 / 0.23 / 1.11 / 0.57 / 0.64 / 1.01 / 0.99 / 0.62 / 0.26 / 0.65
Na2O / 2.68 / 2.36 / 2.55 / 2.46 / 2.35 / 2.18 / 2.42 / 2.53 / 2.22 / 2.22 / 2.38 / 2.52 / 2.54
K2O / <0.04 / <0.04 / <0.04 / <0.04 / <0.04 / 0.03 / 0.04 / <0.04 / <0.04 / <0.04 / <0.04 / <0.04 / <0.04
Total / 97.34 / 97.00 / 97.13 / 97.04 / 98.31 / 97.13 / 96.13 / 96.88 / 96.50 / 97.21 / 96.79 / 96.22 / 96.22
Number of ions on the basis of T+Z+Y = 15
B / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000
Si / 5.949 / 5.980 / 5.963 / 5.884 / 5.978 / 5.900 / 5.977 / 5.896 / 5.945 / 5.945 / 5.917 / 5.958 / 5.971
Al / 0.051 / 0.020 / 0.037 / 0.116 / 0.022 / 0.100 / 0.023 / 0.104 / 0.055 / 0.055 / 0.083 / 0.042 / 0.029
ΣT / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000
Al / 5.859 / 5.632 / 5.989 / 5.628 / 5.982 / 5.420 / 5.782 / 5.622 / 5.427 / 5.430 / 5.734 / 5.969 / 5.734
Fe / 0.141 / 0.368 / 0.011 / 0.372 / 0.018 / 0.580 / 0.218 / 0.378 / 0.573 / 0.570 / 0.266 / 0.031 / 0.266
ΣZ / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000 / 6.000
Mg / 2.350 / 2.156 / 2.326 / 2.180 / 2.311 / 2.345 / 2.185 / 2.235 / 2.281 / 2.242 / 2.184 / 2.334 / 2.142
Fe / 0.640 / 0.831 / 0.666 / 0.808 / 0.681 / 0.643 / 0.815 / 0.754 / 0.708 / 0.745 / 0.805 / 0.656 / 0.850
Mn / 0.010 / 0.012 / 0.008 / 0.012 / 0.009 / 0.012 / – / 0.011 / 0.011 / 0.013 / 0.011 / 0.010 / 0.008
ΣY / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000 / 3.000
Ca / 0.065 / 0.137 / 0.040 / 0.141 / 0.040 / 0.195 / 0.100 / 0.113 / 0.178 / 0.174 / 0.109 / 0.045 / 0.115
Na / 0.838 / 0.752 / 0.796 / 0.781 / 0.724 / 0.694 / 0.772 / 0.804 / 0.710 / 0.706 / 0.754 / 0.794 / 0.815
K / – / – / – / – / – / 0.007 / 0.008 / – / – / – / – / – / –
ΣX / 0.902 / 0.889 / 0.836 / 0.922 / 0.764 / 0.896 / 0.879 / 0.917 / 0.889 / 0.880 / 0.863 / 0.839 / 0.930
Mg/(Mg+Fe) / 0.75 / 0.64 / 0.77 / 0.65 / 0.77 / 0.66 / 0.68 / 0.66 / 0.64 / 0.63 / 0.67 / 0.77 / 0.66
X/(X+Na) / 0.10 / 0.13 / 0.17 / 0.09 / 0.25 / 0.13 / 0.14 / 0.09 / 0.14 / 0.15 / 0.15 / 0.17 / 0.08

* Cameca SX100, Technische Universität Clausthal, Germany. The analytical conditions andreference materials are the same as appended to Table 2

B2O3 calculated using stoichiometric constraints (e.g. Henry et al. 2008)

FeO as total iron

X in the ratio X/(X+Na) represents X-site vacancy