Recent advances in pressure coring techniques, such as the HYACINTH and IODP PCS pressure
cores deployed during Expedition 1 of the India National Gas Hydrate Program using the
JOIDES Resolution have enabled the recovery of fine grained sediments with intact gas hydrates
contained within the sediments. This has provided the opportunity to study the morphology of
gas hydrates within fine grained sediments which until now has been hindered due to the long
transit times during core recovery leading to the dissociation of the gas hydrates. Once recovered
from the seafloor, rapid depressurization and subsequent freezing of the cores in liquid nitrogen
has enabled the near complete fine fracture filling nature of the gas hydrates to be largely
preserved. High resolution X-ray CT (computer tomography), which has a pixel resolution of
approx. 0.07mm, has been used to provide detailed images showing the 3-dimensional
distribution of hydrates within the recovered fine grained sediments. Results have shown that in
fine grained sediments gas hydrates grow along fine fracture faults within the sediment. Although
the fractures were predominantly sub-vertical and continuous through the cores, stranded
fractures were also observed suggesting that hydrate formation is episodic. However, within the
cores open voids were observed which were not evident in low resolution CT images taken
before the depressurization step suggesting that during depressurization either finely
disseminated gas hydrate was dissociated or that gas exsolving from solution created these voids
in the sample prior to freezing in liquid nitrogen. These detailed observations of gas hydrate in
fine grained sediments will help us understand the differing morphology of gas hydrates in
sediments. They also show that sample disturbance is still a major concern and further techniques
are required to restrict these effects so that meaningful laboratory tests can be undertaken on
recovered samples.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/1796 |
| Date | 07 1900 |
| Creators | Priest, Jeffery, Kingston, Emily, Clayton, Chris R.I., Schultheiss, Peter, Druce, Matthew, NGHP Expedition 01 Scientific Party |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Rights | Priest, Jeffrey |
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