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Lu et al. 2005
Lu, H., Moudrakovski, I., Riedel, M., Spence, G., Dutrisac, R., Ripmeester, J., Wright, F. and Dallimore, S. (2005). Occurrence and structural characterization of gas hydrates associated with a cold vent field, offshore Vancouver Island. Journal of Geophysical Research 110: doi: 10.1029/2005JB003900. issn: 0148-0227.

Gas hydrate samples recovered from a cold vent field offshore Vancouver Island were studied in detail both by macroscopic observations and instrumental methods (powder X-ray diffraction method (PXRD), nuclear magnetic resonance (NMR), and Raman spectroscopy). It was found that gas hydrates were massive from 2.64 to 2.94 m below seafloor (mbsf), elongated, nodular and tabular from 4.60 to 4.81 mbsf, and vein-like from 5.48 to 5.68 mbsf, showing a trend of decreasing hydrate content with increasing depth. All samples were determined to be structure I hydrate from PXRD, NMR, and Raman spectroscopies. The hydration numbers were estimated to be 6.1 ¿ 0.2 on average as determined from the methane distribution over the cage sites from NMR and Raman analytical results. Estimates of conversion levels indicated that ~78% of the water in the massive samples was hydrate, down to a low value of ~0.4% for the pore hydrate samples. The results are compared with measurements on synthetic hydrates and samples recovered from below the permafrost on the Mallik site. Differences in methane content and lattice parameters for synthetic and natural samples are relatively minor. Additional work is needed to address the presence of minor gas components and the heterogeneity of natural hydrate samples.

BACKGROUND DATA FILES

Abstract

Keywords
Marine Geology and Geophysics, Gas and hydrate systems, Mineralogy and Petrology, Mineral and crystal chemistry, Mineral Physics, Physical thermodynamics, Mineral Physics, Optical, infrared, and Raman spectroscopy, Mineral Physics, X-ray, neutron, and electron spectroscopy and diffraction, gas hydrate, occurrence, structure, Cascadia, hydration number, saturation
Journal
Journal of Geophysical Research
http://www.agu.org/journals/jb/
Publisher
American Geophysical Union
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