SCANNING ELECTRON MICROSCOPY (SEM) IMAGING OF LABORATORY-GROWN GAS HYDRATES, AND COMPARISONS WITH RECOVERED SAMPLES FROM MARINE AND PERMAFROST ORIGIN

Laura A. Stern¹*, Stephen H. Kirby¹, Susan Circone¹, and William B. Durham^2
1 U. S. Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 USA
² U. C. Lawrence Livermore National Laboratory, Livermore CA 94550 USA
*Corresponding author: [email protected], 650/329-4811 (Tel), 650/329-5163 (Fax)

Scanning Electron Microscopy (SEM) serves as a powerful technique for observing grain and pore structure development associated with gas hydrate formation. Here, we use this technique to observe laboratory-synthesized gas hydrates of known purity, composition and pressure-temperature processing histories that formed originally from reaction of a hydrate-forming gas or liquid with melting ice. We present images conveying the range and variety of textures observed at various extents of reaction. We then image synthetic gas hydrate samples used in increasingly complex laboratory and ocean-floor experiments, and compare the observed features to those developed within natural gas hydrate nodules or hydrate zones recovered from both marine and permafrost settings. While accurately identifying in situ growth features and distinguishing them from features produced as artifacts of recovery or handling methods will likely remain problematic in at least the near future, we demonstrate that lab-synthesized samples can be produced to yield remarkably similar textures, phase distribution , and grain contacts as found in at least some hydrate-bearing materials recovered from natural settings.