| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | August 3, 2010 |
| Latest Amendment Date: | August 9, 2013 |
| Award Number: | 1037874 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Barbara Ransom
bransom@nsf.gov (703)292-7792 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | October 1, 2010 |
| End Date: | September 30, 2014 (Estimated) |
| Total Intended Award Amount: | $67,852.00 |
| Total Awarded Amount to Date: | $67,852.00 |
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| Recipient Sponsored Research Office: |
4333 BROOKLYN AVE NE SEATTLE WA US 98195-1016 (206)543-4043 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
4333 BROOKLYN AVE NE SEATTLE WA US 98195-1016 |
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Performance Congressional District: |
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| NSF Program(s): | Marine Geology and Geophysics |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
The concentrations and isotopic compositions of volatiles like CO2, CH4, and H2 in hydrothermal fluids provide crucial information concerning the nature of the heat source underlying hydrothermal systems and the high temperature water-rock reactions that occur deep in the ocean crust. These chemical species are also a vital link between the mantle, magmas, and the biological communities that thrive at deep-sea hydrothermal vents. This research focuses on determining the concentration of CO2, methane, and C2 hydrocarbons in long-term (~20 year) time-series fluid samples from hydrothermal vents on the Endeavour Segment of the Juan de Fuca Ridge off the northwestern coast of the US. Work also involves analyzing the associated carbon and hydrogen isotopes. These data will be used to discriminate between magmatic, thermal, and sedimentary/biological processes controlling the targeted carbon-bearing species and identify the source of the anomalous carbon gradient that is found in the Endeavour hydrothermal vent area. The primary broader impact of the work is completing a major hydrothermal fluid dataset for the NSF-funded Ridge 2000 Program to allow studies of integration and synthesis to take place. There is also international collaboration with a Swiss scientist.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
One objective of this project was to develop an analytical system that would allow the determination of carbon isotope values for hydrothermal gas samples that had been previously collected on several cruises. The other objective was to use the isotopic data produced to either prove or disprove earlier ideas about the higher than usual concentrations of methane in the vent fluids along the Endeavour segment of the Juan de Fuca Ridge. This ridge appears to be a “bare rock” ridge in that no sediments are visible but concentrations of methane as high as 4 millimolar have been seen there. Most truly “bare rock” systems contain less than 0.1 millimolar methane in their fluids. Early speculation about the anomalously high methane concentration was that it was due to the thermal decomposition of organic material in sediments that were deposited earlier then buried by subsequent lava flows. The isotopic data produced by this work does indeed support the earlier speculation. The carbon isotopic values have a higher proportion of the heavier isotope of carbon (13C) as the number of carbon atoms increases in the hydrocarbon, in this case from methane to ethane to propane. This is indicative of hydrocarbons produced by the thermal decomposition of organic matter and supports the concept of hidden sediments beneath the ridge crest.
The data produced here also helped us to understand that these hidden sediments are more pronounced in the north and likely means the sediment source was the Vancouver Island continental margin. We also learned that a large earthquake that occurred in 1999 caused changes in the isotopic composition of methane. That means that the earthquake altered the mechanism of methane production.
Another important aspect of this work is that the instrument developed during the project has become an important educational tool that is being used in the thesis work of three graduate students so far.
Last Modified: 06/27/2015
Modified by: Marvin D Lilley
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