SUMMARY AND REEVALUATION OF THE HIGH-TEMPERATURE ISOTOPE GEOCHEMISTRYOF METHANE

Thirty years of research are brought together into one coherent summar y of carbon and hydrogen isotope effects during the thermocatalytic pr oduction of methane from model compounds, petroleum, source rocks, and coals. The approach used by the authors and co-workers has been to py rolyze model and natural compounds and to study the isotopic fractiona tions associated with molecular structure, temperature, and catalysis. The results from these experiments are summarized. A practical applic ation of these pyrolysis experiments was the development of the pyroly sis-carbon isotope method (PCM) for determining kerogen maturity. This maturity indexing procedure is based on the isotopic difference betwe en the total methane produced by exhaustive pyrolysis and the parent o rganic carbon and the mole ratio of methane to parent carbon. Data are also summarized for the thermal destruction of methane and carbon iso tope exchange between methane and amorphous carbon and carbon dioxide. The latter results are important when determining the source of metha ne in hydrothermal fluids. Copyright (C) 1997 Elsevier Science Ltd.