title: Generation of methane in the Earth's mantle: in situ high pressure-temperature measurements of carbonate reduction.
abstract: We present in situ observations of hydrocarbon formation via carbonate reduction at upper mantle pressures and temperatures. Methane was formed from FeO, CaCO(3)-calcite, and water at pressures between 5 and 11 GPa and temperatures ranging from 500 degrees C to 1,500 degrees C. The results are shown to be consistent with multiphase thermodynamic calculations based on the statistical mechanics of soft particle mixtures. The study demonstrates the existence of abiogenic pathways for the formation of hydrocarbons in the Earth's interior and suggests that the hydrocarbon budget of the bulk Earth may be larger than conventionally assumed.
authors.affiliation: Department of Physics and Astronomy, Indiana University, South Bend, IN 46634, USA. hpscott@iusb.edu
authors.forename: Henry P
authors.initials: HP
authors.lastname: Scott
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Hemley
authors.forename: Ho-Kwang
authors.initials: HK
authors.lastname: Mao
authors.forename: Dudley R
authors.initials: DR
authors.lastname: Herschbach
authors.forename: Laurence E
authors.initials: LE
authors.lastname: Fried
authors.forename: W Michael
authors.initials: WM
authors.lastname: Howard
authors.forename: Sorin
authors.initials: S
authors.lastname: Bastea