1. Terrestrial magmatism covers 8 orders of magnitude oxygen fugacity from Carmichael (1991)

2. Compiled from work of O’Neill, Pownceby, Holzheid and others

3. Chondritic metals become Co- and Ni-poor and Fe-rich Chondritic silicates become Fe-, Ni-, Co-poor from Arculus et al. (1990)

4. Olivine composition changes with oxygen fugacity such that it has an enormous stability field that depends upon equilibria with Fe metal and Fe oxide 2Fe 3 O 4 + 3SiO 2 = 3Fe 2 SiO 4 + O 2 FeSiO 3 + Fe + ½ O 2 = Fe 2 SiO 4 from Nitsan (1974)

5. from Buening and Buseck (1973)from Chakraborty et al. (2004) Diffusion of major, minor and trace elements in crystalline solids is strongly dependent upon oxygen fugacity

6. from Righter (2003) Metal-silicate partition coefficients are fO 2 dependent

7. Five different approaches in high pressure research A)Sliding sensors (Taylor et al. 1992; Rubie et al., 1993) B)Sample composition helps to set fO 2 (Rubie, 1999) C)Fluid or buffer in capsule (King et al. 2000) D)Capsule imposes fO 2 (Frost et al. 2004) E)Assembly imposed (COMPRES development?) (Dobson and Brodholt, 1999)

8. Respond to fO 2 of environment and record in either metal or oxide solid solution Problems: Cannot really control fO 2 using this approach, but at least it can be known from Taylor et al. (1992) A) Sliding sensors

9. Fe 2 SiO 4 = 2Fe + SiO 2 + O 2 Ni 2 SiO 4 = 2Ni + SiO 2 + O 2 Mg 2 SiO 4 + SiO 2 = Mg 2 Si 2 O 6 from Rubie et al. (1993) fO 2 calculated from td and a-x data.

10. B) Sample composition participates from Rubie (1999) Si:Fe ratio in metal of metal/silicate experiments was varied to vary the fO 2 imposed upon sample Problems: Si in metal causes non-ideal behavior and therefore potentially not natural

11. C) Fluid or buffer in capsule from Holloway et al. (1992); Pawley et al. (1992); King et al. (2000) CO 2 or O 2 sources have been used to fix fO 2 in capsules Problems: -C migration into Pt and reduction over time - fluids dissolve into other phases

12. C) Fluid or buffer in capsule from Rubie (1999) Ni-NiO mix has been used to fix fO 2 in capsules Problems: NiPt alloying

13. D) Capsule imposed Re capsules have been used to carry out experiments at higher fO 2, because Re-ReO 2 buffer is much higher than IW or QFM Problems: buffer never verified and buffer can react with sample from Frost et al. (2004)

14. D) Capsule imposed from Arculus et al. (1990) Graphite capsules can be used to buffer oxygen fugacity C-CO-CO 2 is below IW at 1 bar, but is very pressure sensitive At 10 kb 3 log units higher…..

15. D) Capsule imposed from LaTourette and Holloway (1994) ……by 80 kb, oxygen fugacity is buffered about 6 log fO 2 units above that of 1 bar

16. from Luth (1993) Diamond can also participate in buffering equilibria, but its hardness becomes a problem for later sample preparation – grinding and polishing

17. Best approach? Buffer is in pressure medium Advantages: - Long lasting - Doesn’t react with sample from Dobson and Brodholt (1999) E) Pressure medium imposed

18. Castable octahedra gasket and pressure medium are the same (Dobson and Brodholt, 1999) => high failure rate Ni-, Fe-, Re-doped pressure medium – cast or injection molded? Pre-cast with spacers gasket and pressure medium are different (maybe an area for COMPRES development??) => lower failure rate ? Hybrid ?