Diamond and graphite crystallization from C–O–H fluids under high pressure and high temperature conditions |
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Authors: | A G Sokol Yu N Pal'yanov G A Pal'yanova A F Khokhryakov Yu M Borzdov |
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Affiliation: | Institute of Mineralogy and Petrography, Russian Academy of Sciences, Koptyuga pr., 3, Novosibirsk, 630090, Russia |
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Abstract: | Crystallization of diamond was studied in the CO2–C, CO2–H2O–C, H2O–C, and CH4–H2–C systems at 5.7 GPa and 1200–1420°C. Thermodynamic calculations show generation of CO2, CO2–H2O, H2O and CH4–H2 fluids in experiments with graphite and silver oxalate (Ag2C2O4), oxalic acid dihydrate (H2C2O4·2H2O), water (H2O), and anthracene (C14H10), respectively. Diamond nucleation and growth has been found in the CO2–C, CO2–H2O–C, and H2O–C systems at 1300–1420°C. At a temperature as low as 1200°C for 136 h there was spontaneous crystallization of diamond in the CO2–H2O–C system. For the CH4–H2–C system, at 1300–1420°C no diamond synthesis has been established, only insignificant growth on seeds was observed. Diamond octahedra form from the C–O–H fluids at all temperature ranges under investigation. Diamond formation from the fluids at 5.7 GPa and 1200–1420°C was accompanied with the active recrystallization of metastable graphite. |
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Keywords: | HP-HT experiment Diamond crystallization C–O–H system Fluid |
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