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Gas hydrates from two cores at Expedition 311 Site U1328 were measured with Raman and NMR spectroscopy. Both samples were sI methane gas hydrate with one containing small amounts of H2S. Interestingly, in both cases, H2S was detected in the void gas headspace of the recovered core. It is not clear why H2S was present in only one of the samples.
Cage occupancies and hydration numbers compared well with predictions from a statistical thermodynamic gas hydrate program and other measurements on natural methane gas hydrates. Raman spectroscopy has been shown to give quantitative methane cage occupancies even when a small amount of a second component is present in the gas hydrate. In addition, water Raman peaks were used to provide a possible estimate to the degree of sample degradation resulting from unstable conditions during recovery.