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Progress in Earth and Planetary Science
Figure 4 | Progress in Earth and Planetary Science

Figure 4

From: Natural moissanite (SiC) – a low temperature mineral formed from highly fractionated ultra-reducing COH-fluids

Figure 4

Isothermal composition – f O2 sections at (a) 2 GPa, 1100°C and (b) 10 GPa, 1300°C. At oxygen fugacities below the carbide- or metal–forming reaction, X Fe olivine drops rapidly to per mill values. The grey field corresponds to olivine + orthopyroxene saturation and only additional phases are indicated. With decreasing oxygen fugacity the FeSiC-alloy becomes more and more Si-rich, leading to the fcc-bcc phase transition and then to iron silicide stability. Note that the Si-alloy formed orthopyroxene and olivine breakdown is essentially pure Si with 1 mol% C and almost no iron. The calculations are done at discrete f O2 -values represented by symbols; green: X Mg olivine, black: X Mg opx, red: C content in metal alloy, blue: Si-content in metal alloy.

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