000			01931nab a2200205 4500
005			20260520000836.0
008			260224s2009 xxu
245	0	0	_aIn situ diamond-anvil cell observations of methanogenesis at high pressures and temperatures
260			_a _b _cnov./dic. 2009
270			_a08/06/2010 ; 08/06/2010
300			_a8 p. ; 5571-5579
520			_aTranscripción del resumen del autor. In situ high pressure-temperature (P-T) measurements on C-H-O fluids at lower crust and upper mantle conditions have been performed to assess the extent and limit of methane generation within the Earth. Experiments were conducted using diamond-anvil cells at temperatures from 250 to >1500 °C and pressures between 1 and 8 GPa, assuming conditions along a subduction-setting geotherm. In many experiments, methanogenesis is observed, in particular, in those experiments in which elemental carbon or reduced transition metals (e.g., Fe0) were present. The direct reduction of CO2 to methane was not observed under any set of conditions. Methanogenesis is sensitive to C-H-O fluid composition and, specifically, the activity of H2. Kinetic barriers to direct hydrogenation of CO persists over the range of conditions explored, and hydrogenated transition-metal carbonyl species likely play a critical role in methane formation. Surprisingly, the direct hydrogenation of graphite yields considerable methane. The observation of both CO2 and H2 generation during high T and P reactions of ferrous oxide, calcium carbonate, and water indicates that methanogenesis in the lower crust and upper mantle is plausible; however, the absolute yield of methane is strongly controlled by the activity of H2.
581			_a6
773	0		_tEnergy & fuels _g23
942			_cARTICULO
100	1		_aSharma, Anurag _942287
100	1		_aCody, George D. _942288
100	1		_aHemley, Russell J. _942289
999			_c170793 _d170793