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Table 2 Enthalpy of 13C/12C fractionation in coexisting fluid and melt in silicate-COH under oxidizing and reducing conditions (data from Mysen 2016, 2017)

From: Redox-controlled mechanisms of C and H isotope fractionation between silicate melt and COH fluid in the Earth’s interior

Oxidizing Reducing
∆HCO3(fluid)* 11 ± 3 kJ/mol ∆HCH4(fluid) 4.7 ± 0.2 kJ/mol
∆HHCO3(fluid)** − 12 ± 5 kJ/mol ∆HCH4(melt) − 4.8 ± 0.6 kJ/mol
∆HCO3(melt)* − 30 ± 4 kJ/mol ∆HKmelt/fluidb 9.5 ± 0.8 kJ/mol
∆HHCO3(melt)** 29 ± 6 kJ/mol   
∆H∑13C/∑12C(melt)a − 9 ± 1.6 kJ/mol   
∆H∑13C/∑12C(fluid)a − 5.8 ± 1.3 kJ/mol   
∆HKmelt/fluidb 3.2 ± 0.7 kJ/mol   
  1. *∆HCO3(fluid)and ∆HCO3(melt) were derived from the relationship, ln(13C/12C) vs. 1/T (K−1) in fluid and melt under oxidizing conditions
  2. **∆HHCO3(fluid)and ∆HHCO3(melt) were derived from the relationship, ln(13C/12C) vs. 1/T (K−1) in fluid and melt under oxidizing conditions
  3. ∆HCH4(fluid)and ∆HCH4(melt) were derived from the relationship, ln(13C/12C) vs. 1/T (K−1) in fluid and melt under reducing conditions
  4. aThe same as for ∆HCO3(fluid) and ∆HCO3(melt) except that total carbonate ratio ∑13C/∑12C, where total carbonate is CO3 + HCO3, is used
  5. b∆HKmelt/fluid under oxidizing and reducing conditions was derived from the relationship, ln[(∑13C/∑12C)melt/[(∑13C/∑12C)fluid] vs. 1/T (K−1)