H and N systematics in thermally altered chondritic insoluble organic matter: An experimental study

A series of experiments was performed to constrain the chemical and isotopic evolution of insoluble organic material (IOM) during hydrothermal alteration at temperatures ranging from 250 degrees C to 450 degrees C at 50 MPa. Experiments involved IOM that was extracted from the Murchison (CM2) meteorite or synthesized by aqueous carbonization of dextrose. Flash (dry) pyrolysis experiments at 400 - 1000 degrees C were also conducted with Murchison IOM to distinguish between the effects of hydrothermal and thermal degradation. Extended reaction times (up to 3905 h) were employed to establish D/H equilibria between IOM and H2O. The H isotope compositions of the H2O used in the experiments ranged from delta D= -447 parts per thousand to 3259 parts per thousand. Results revealed that the extent of the IOM H isotope evolution strongly depends on the delta D composition of the coexisting H2O with minimal temperature effects. The empirical relationship that describes the isotope exchange between IOM and H2O is as follows: