Abstract
Sodium-rich montmorillonite, Na-exchanged montmorillonite, and Na-exchanged nontronite form intercalate complexes with methane hydrate, identified by a characteristic d(001) value of ~2.2 nm. The upper stability of both Na-rich montmorillonite-methane-hydrate complexes is nearly identical to that of methane hydrate, whereas that of Na-exchanged nontronite-methane-hydrate complex is ~1 °C lower. The low-temperature stability of these complexes is controlled by dehydration reactions of the montmorillonite and nontronite. At temperatures of 2 °C, the d(001) value of the montmorillonite complex decreases step-wise with decreasing temperature from ~2.2 nm at 2 °C to 1.6 nm at ≤-5 °C, indicating that H2O is progressively expelled from the interlayer. All methane is probably expelled at ~0 °C. The d(001) value of the nontronite complex did not show a similar step-wise reduction and, consequently, the lower stability of this complex is not well established. We conclude that under conditions of reduced salinity, smectite may sufficiently swell and intercalate with methane hydrate in an intermediate to deep-ocean floor environment. Consequently, these smectite-methane-hydrate complexes in the sub-ocean-floor surface may store substantial quantities of carbon.
© 2015 by Walter de Gruyter Berlin/Boston
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- Determination of high-pressure phase equilibria of Fe2O3 using the Kawai-type apparatus equipped with sintered diamond anvils
- Suhailite, a new ammonium trioctahedral mica
- First record of K-cymrite in North Qaidam UHP eclogite, Western China
- Stability of uranium (VI) peroxide hydrates under ionizing radiation
- Heat capacities and thermodynamic functions of TiO2 anatase and rutile: Analysis of phase stability
- The behavior of Co and Ni in olivine in planetary basalts: An experimental investigation
- Partitioning of Ni between olivine and an iron-rich basalt: Experiments, partition models, and planetary implications
- The application of Lorentz transmission electron microscopy to the study of lamellar magnetism in hematite-ilmenite
- A Monte Carlo study of short- and long-range order of tetrahedral cations in sapphirine and khmaralite
- High-pressure ammonium-bearing silicates: Implications for nitrogen and hydrogen storage in the Earth’s mantle
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- Interaction of phosphate-bearing solutions with gypsum: Epitaxy and induced twinning of brushite (CaHPO4·2H2O) on the gypsum cleavage surface
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