American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 352586 bytes)    Cited by

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. B10, 2495, doi:10.1029/2002JB002300, 2003

A steady state model for marine hydrate formation: Constraints on methane supply from pore water sulfate profiles

M. K. Davie

Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, Canada


B. A. Buffett

Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia, Canada


Abstract

We develop a steady state model to describe the formation of hydrate below the seafloor. The model includes the sulfate reducing zone (SRZ), which permits sulfate measurements to be used in conjunction with chloride data to better constrain the supply of methane at hydrate locations. The steady state model is applied at Ocean Drilling Program Site 997 to resolve the methane source at the Blake Ridge. Sulfate measurements rule out a shallow source of methane directly below the SRZ because the predicted sulfate concentration overestimates the measurements by a factor of 2 or more. Although a deep source of methane reproduces the main features of the sulfate and chloride data when the upward fluid velocity is 0.25 mm yr−1, the deep source fails to reproduce the increased freshening observed between 200 and 450 m below seafloor. We find that an in situ methane source (located in the lower part of the hydrate stability zone) together with an incoming methane bearing fluid at 0.23 mm yr−1 gives the best fit to both the sulfate and chloride data. In addition, the predicted sulfate profile indicates that anaerobic methane oxidation is the primary pathway of sulfate depletion at the Blake Ridge.

Received 7 November 2002; accepted 24 July 2003; published 22 October 2003.

Index Terms: 1050 Geochemistry: Marine geochemistry (4835, 4850); 3022 Marine Geology and Geophysics: Marine sediments—processes and transport; 3099 Marine Geology and Geophysics: General or miscellaneous; 3210 Mathematical Geophysics: Modeling.

Read Full Article (file size: 352586 bytes)    Cited by

Citation: Davie, M. K., and B. A. Buffett (2003), A steady state model for marine hydrate formation: Constraints on methane supply from pore water sulfate profiles, J. Geophys. Res., 108(B10), 2495, doi:10.1029/2002JB002300.