Carbon isotope fractionation between graphite and diamond during shock experiments
Abstract
Carbon isotopic compositions were measured for shock-produced diamond and shocked graphite formed at peak pressures ranging from 37 to 52 GPa. The 13C values of diamonds produced in a sealed container were generally lower than that of the initial graphite. The differences in the carbon isotopic composition between initial graphite and shocked graphite/diamond may reflect kinetic isotopic fractionation during the oxidation of the graphite/diamond and/or analytical artifacts possibly induced by impurities in the samples. The pressure effect on the isotopic fractionations between graphite and diamond can be estimated from the 13C values of impurity-free diamonds produced using a vented container from which gases, including oxygen, in pore spaces escaped during or after the diamond formation (e.g., 0.039 ± 0.085 at a peak pressure of 52 GPa). Any isotopic fractionation induced by shock conversion of graphite to diamond is too small to be detected in natural shock-induced diamond-graphite systems related to terrestrial impact cratering processes.
- Publication:
-
Meteoritics and Planetary Science
- Pub Date:
- August 2003
- DOI:
- 10.1111/j.1945-5100.2003.tb00311.x
- Bibcode:
- 2003M&PS...38.1255M