ABSTRACT
We estimated δ13C of the C–H–O fluid produced by the decomposition of stearic acid at high-pressure and high-temperature conditions (10 and 17 GPa, 800–1600°C) from δ13C of the solid carbon products and the initial stearic acid. The δ13C of the stearic acid and the recovered graphite/diamond were −28.0‰ and −27.08 to −29.35‰, respectively. Then, the δ13C of the coexisting C–H–O fluid was estimated to be −26.3 to −29.2‰ based on the stoichiometry of the decomposition reaction C18H36O2 → 10C + 8CH4 + 2H2O. In the studied P-T-t conditions, carbon isotope fractionation through the stearic acid decomposition is as small as < 3‰. This means that the δ13C of the C–H–O fluid is almost identical to that of the initial stearic acid and can be a useful tracer of carbon source for diamond forming reaction such as in fluid/carbonate systems.
Acknowledgements
The authors thank S. Kakizawa, T. Inoue, and K. Litasov for their technical advices in performing high-pressure experiments using the multi-anvil apparatus. The authors also thank K. Amano for her advice on the data visualization of Figure 4. This work was supported by the Joint Usage/Research Center PRIUS, Ehime University, Japan.
Disclosure statement
No potential conflict of interest was reported by the author(s).