Table 1

Average chemical compositions of clinoenstatite, ilmenite, and perovskite. Compositions of ilmenite and perovskite were determined by ATEM and that of clinoenstatite by electron microprobe analysis. The number in parentheses for each phase is the number of analyses of the different grains.

Oxide (weight %)Clinoenstatite (8)Ilmenite* (6)Perovskite*(3)
Na2O0.010.670.81
MgO29.3328.3928.58
Al2O3 0.150.070.16
SiO2 55.7456.3555.14
CaO0.780.380.12
TiO2 0.150.170.42
Cr2O3 0.160.160.18
MnO0.510.280.19
FeO13.5113.5414.41
Total100.33100100
Cation number (O = 6)
Na0.000.050.06
Mg1.561.511.53
Al0.010.000.01
Si1.992.011.98
Ca0.030.020.01
Ti0.000.000.01
Cr0.010.000.01
Mn0.020.010.01
Fe0.400.400.43
Total4.014.01 4.03
Fe/(Mg + Fe)0.21  ±  0.010.21  ±  0.010.22  ±  0.01
  • * Values were calculated by use of the experimentally determined K-values with synthetic corundum (Al2O3)–ilmenite (MgSiO3) and silicate perovskite phases, respectively (18). K-values of some cation pairs for ilmenite were taken from the average K-values of pyroxene and silicate perovskite.