Extended Data Fig. 5: Pressure estimation of the diamond source.
From: Redox state of the deep upper mantle recorded by nickel-rich diamond inclusions
Diamond symbols: internal pressure at room temperature (black dashed line) recorded by the various trapped phases in the inclusions. Blue diamonds: 8.4 and 8.7 GPa (shift of Raman lines) and 8.1 GPa (not shown) based on the X-ray peak. The blue lines: isochores (equal-volume lines) of fluid N2 at high pressure and temperature. The volume was determined based on the pressure in the deltanitrogen inclusions in the two diamonds and the EOS of solid δ-N234. It was extrapolated to high temperatures using the EOS of fluid N235,36. Volume change due to thermal expansion and compressibility of the diamond were neglected and would lead to somewhat higher pressure if included18. Cyan diamond: solid CO2-I at 8 GPa based on the shift of the FTIR line38 (Supplementary Data 5, Supplementary Fig. 5.2) Cyan lines: isochores for fluid CO2, using the volume calculated using the EOS of CO2-I40 and of fluid CO2 (a41, b42). Brown diamond and line: The maximum internal pressure at room temperature (3-9 GPa, by the Raman spectra) and the isomeke for coesite in diamond (the line along which the diamond and the coesite have the same P, T and volume, calculated using the software of Angel et al.44). Dashed grey line – the diamond graphite phase boundary78, Black line – the melting curve of solid N279. Orange line – the 38 mW/m2 geotherm80 connected to the mantle adiabate37. Orange thick line – the inferred possible range of pressure and temperature for the two diamonds.
