Thermogenic vent gas and gas hydrate in the Gulf of Mexico slope: Is gas hydrate decomposition significant?

Samples of vent gas and gas hydrate on the Gulf of Mexico slope were collec ted by research submersible (similar to 540 m water depth) and by piston co ring (similar to 1060-1070 m water depth). Although gas hydrate that crops out is transiently unstable, the larger volume of structure II gas hydrate in the gulf is stable or increasing in volume because gas from the subsurfa ce petroleum system is venting prolifically within the gas hydrate stabilit y zone. Vent gas from gas hydrate shows no meaningful molecular evidence of gas hydrate decomposition. Gas hydrate fabrics, mainly vein fillings, are typical of ongoing crystallization. Once crystallized, most hydrocarbons ar e protected from bacteria within the crystal lattice of gas hydrate. A leak y petroleum system is proposed to be the main source of thermogenic greenho use gases in the central gulf. Stable gas hydrate sequesters large volumes of greenhouse gases, suggesting that gas hydrate may not be a significant f actor in models of climate change at present.