Guest Blog: Satoko Owari, Inorganic Geochemist

My research topic is identifying the source and migration of fluids in marine sediments using radioactive iodine (129I) with a half-life of 15.7 million years. Half-life is the time it takes half of the atoms of a material to decay.

Previous work with iodine isotopes (isotopes: atoms of the same element with different numbers of neutrons) has demonstrated that the way a fluid (e.g., water, gas) moves through sediment depends on the physical properties (e.g., porosity, permiability) of the sediment. Specifically, the interstitial water (interstitial water: fluid in between sediment particles) contains relatively “old” iodine in gas hydrate bearing layers.

Understanding gas hydrates is very important because they include H2O molecules and methane gas in their crystal structures. Gas hydrate is called “fire ice” because it can burn itself and looks like ice. Gas hydrate formation and dissociation are strongly related to pore fluid geochemistry.

For IODP Expedition 372, I am interested in using the presence of these radioactive iodine isotopes to determine the age of the interstitial water in the sediment cores we collect from the Hikurangi Margin in New Zealand. Knowing more about the age of the fluids in the sediment will tell me something about where the fluids came from and what types of sediments they have passed through. The origin and age of these fluids will also teach us about how they are related to the formation of gas hydrate in the sediment and how the gas hydrate can deform the sediment.

We are using these fluid geochemistry techniques to create an origin story for the sediment cores we recovered and understand how they got to their characteristics.

Erin Todd
More articles by: Erin Todd

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