Coexistence of structure I and II gas hydrates in Lake Baikal suggesting gas sources from microbial and thermogenic origin

[1] We report the field observation of hydrate deposits of different crystal structures in the same cores of a mud volcano in the Kukuy Canyon. We link those deposits to chemical fractionation during gas hydrate crystallization. Gas composition and crystallographic analyses of hydrate samples reveal involvement of two distinct gas source types in gas hydrate formation at present or in the past: microbial (methane) and thermogenic (methane and ethane) gas types. The clathrate structure II, observed for the first time in fresh water sediments, is believed to be formed by higher mixing of thermogenic gas.

[1]  E. D. Sloan,et al.  Structural transitions in methane+ethane gas hydrates — Part I: upper transition point and applications , 2000 .

[2]  Tsutomu Uchida,et al.  Spectroscopic Observations and Thermodynamic Calculations on Clathrate Hydrates of Mixed Gas Containing Methane and Ethane: Determination of Structure, Composition and Cage Occupancy , 2002 .

[3]  K. Hayamizu,et al.  Chemical shift standards in high-resolution solid-state NMR (2) 15N nuclei , 1991 .

[4]  D. Hutchinson,et al.  Depositional and tectonic framework of the rift basins of Lake Baikal from multichannel seismic data , 1992 .

[5]  D. Hutchinson,et al.  Heat flow and gas hydrates of the Baikal Rift Zone , 2000 .

[6]  K. Hayamizu,et al.  Chemical shift standards in high-resolution solid-state NMR (1) 13C, 29Si, and 1H nuclei. , 1991 .

[7]  Alexei V. Milkov,et al.  Molecular and stable isotope compositions of natural gas hydrates : A revised global dataset and basic interpretations in the context of geological settings , 2005 .

[8]  T. Ebinuma,et al.  Coexistence of structure I and II hydrates formed from a mixture of methane and ethane gases , 2003 .

[9]  M. Vanneste,et al.  Sublacustrine mud volcanoes and methane seeps caused by dissociation of gas hydrates in Lake Baikal , 2002 .

[10]  E. D. Sloan,et al.  Fundamental principles and applications of natural gas hydrates , 2003, Nature.

[11]  V. Soloviev,et al.  Gas hydrate accumulation in the subsurface sediments of Lake Baikal (Eastern Siberia) , 2003 .

[12]  Michael J. Whiticar,et al.  Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane , 1999 .

[13]  L. P. Golobokova,et al.  Methane hydrate in the near-bottom deep-water sediment of lake Baikal , 2003 .

[14]  Steven F. Dec,et al.  Evidence of structure II hydrate formation from methane+ethane mixtures , 2000 .