| | synHP1a | synHP1 + Cr + Mnb | HAB + Ol + Mn | synMORB80c | synMORB60 | synMORB40 |
|---|
SiO2 | 45.39 | 44.57 | 47.14 | 50.66 | 48.97 | 43.78 |
TiO2 | 1.41 | 1.38 | 0.55 | 0.75 | 1.04 | 0.92 |
Al2O3 | 8.28 | 8.47 | 15.49 | 14.08 | 13.61 | 12.17 |
Cr2O3 | 0.22 | 1.05 | 0.03 | 0.00 | 0.00 | 0.00 |
FeO* | 12.03 | 11.82 | 8.56 | 7.12 | 13.75 | 24.16 |
MnO | 0.18 | 0.81 | 0.49 | 0.50 | 0.50 | 0.50 |
MgO | 25.48 | 25.02 | 15.53 | 15.97 | 11.58 | 9.04 |
CaO | 6.72 | 6.60 | 10.13 | 10.92 | 10.55 | 9.43 |
Na2O | 0.00 | 0.00 | 1.88 | 0.00 | 0.00 | 0.00 |
K2O | 0.00 | 0.00 | 0.08 | 0.00 | 0.00 | 0.00 |
NiO | 0.29 | 0.29 | 0.08 | 0.00 | 0.00 | 0.00 |
P2O5 | 0.00 | 0.00 | 0.04 | 0.00 | 0.00 | 0.00 |
Total | 100 | 100 | 100 | 100 | 100 | 100 |
Mg# | 79.1 | 79.1 | 76.4 | 80.0 | 60.0 | 40.0 |
- Oxide concentrations are based on the mass fraction of components in each mix. FeO* = all Fe expressed as FeO. Mg# = 100 [Mg/(Mg + Fe)], molar. Note that HAB + Ol + Mn was the only natural basalt powder and was the only mix to which synthetic Mg2SiO4 was added. The remaining starting mixes were made of mixed oxides and CaCO3 powders (see Starting Compositions). a From Matzen et al. (2011), Table 1 and Table 3 (the superliquidus experiments 43 and 34). The authors noted that the synHP1 mix had gained ~ 0.7 wt% Al2O3 during the grinding process, probably reflecting the fact that the grinding was done using an alumina mortar and pestle and that some fraction of the Al2O3 oxide powder had converted to corundum during repeated firings at 800–1000 °C. This increase in Al2O3 is included in the synHP1 composition reported above. b Mass balance of the synHP1 + Cr + Mn experiments showed a consistent increase in Al2O3 in the calculated bulk compositions relative to the nominal synHP1 + Cr + Mn composition; the average increase was ~ 3.3% and is most likely due to the same issue discussed in (a), since synHP1 + Cr + Mn was constructed using powder from the original batch of synHP1. The Al2O3 content of the nominal synHP1 + Cr + Mn composition has been increased by 0.31 wt%, the remaining oxide concentrations were reduced proportionally. c Initial target MORB composition based on Fo90-corrected average subaqueous ridge segments from Gale et al. (2014), expressed in wt% on an alkali and MnO-free basis: SiO2 = 50.2, TiO2 = 1.07, Al2O3 = 13.95, FeO* = 9.54, MgO = 14.43, CaO = 10.81, Mg# = 73. The section Starting compositions describes how the compositions for the three synMORB mixes were calculated; for synMORB80, the weighed-out mass fraction of TiO2 was low by ~ 30% (0.75 wt% instead of 1.07 wt%), all the remaining oxide concentrations were increased proportionally (note that these changes are quite small, e.g., silica changes from the original target value of 50.50 to 50.66 wt%). Drying temperatures to remove adsorbed water prior to weighing powders: SiO2 and TiO2 at 800 °C, Al2O3 at 1000 °C, Fe2O3 at 700 °C, CaCO3 at 400 °C, and Cr2O3, Mn2O3, forsterite, and the synHP1 and HAB powders in a vacuum oven at 120 °C
