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Dissolved gases in the mariana backarc water column
- 1. Tracing mantle helium and methane in the Mariana back-arc water column Riley Garvey Clemson University Biosystems Engineering Healthy Oceans PMEL Hatfield Marine Science Center Tamara Baumberger David Butterfield 27 July 2020
- 2. Objectives • Provide support for possible sources of hydrothermal venting using water column data from the Mariana backarc • Specifically focusing on methane and mantle helium • Track Helium-3 (conservative tracer) in the water column
- 3. • Data was gathered during the FK151121 cruise aboard R/V Falkor • Study location was along the central and Southern Mariana Backarc • A hydrothermally active region of the Western Pacific Geographical Setting Source: Ocean Data View Source: FK151121 Cruise Report
- 4. Geological setting • Subduction of the Pacific Plate below the Philippine Plate creates a volcanic arc and backarc • These interactions lead to hydrothermal activity Source: Schmidt Ocean Institute Source: Schmidt Ocean Institute and Bill Chadwick
- 5. Ship Methodology • Water samples were taken using a CTD water sampling rosette using tow yo and vertical casts • CTD – Conductivity, Temperature, Depth • Samples were analyzed for methane content on the ship using a gas chromatograph
- 8. Ship Methodology • Water samples were taken using a CTD water sampling rosette using tow yo and vertical casts • CTD – Conductivity, Temperature, Depth • Samples were analyzed for methane content on the ship using a gas chromatograph
- 9. Lab methodology • Helium samples were stored in copper tubing • Brought back to NOAA PMEL Helium Isotope Laboratory in Newport, Oregon to be analyzed • Extracted using a high vacuum extraction line • Run on a dual collector, 25-cm-radius mass spectrometer • Sample data gathered in excel and analyzed using Ocean Data View
- 10. Results
- 11. Helium
- 12. Helium
- 13. Methane
- 14. Summary Snail Vent Perseverance Vent Hafa Adai Vent Alice Springs (Previously known)
- 15. Next Steps • Explore the Northern portion of the Mariana backarc • There is a cruise scheduled for the Northern portion of the backarc in 2021 • Analyze more of the helium samples, especially where there are large gaps in the data
- 16. Acknowledgements • I would like to thank: • Tamara Baumberger for her mentorship on this project and for her work compiling the helium dataset and the methane dataset • David Butterfield for generating the methane dataset • Camilla Wilkinson for running helium samples • Hu Wang for assistance with sample collection • The FK151121 cruise ship’s crew and scientific party • Adi Hanein for managing the logistics for the undergraduates • The Hollings Scholarship Team
Editor's Notes
- Mantle is not a big source of methane, it tends to come from reduced CO2 in the mantle and basaltic rocks, generated by microbes, and cooking of organic material. Most of this is interaction with basaltic rocks Methane is consumed Don’t say “event plumes” because that’s a specific term, say something like “ongoing” and “Not ongoing”
- Data was gathered along the Mariana backarc, which is a spreading center in the northwestern pacific, at the convergence of the Pacific and Philippine plates, with extensive hydrothermal activity. All data was gathered during the FK151121 cruise aboard R/V Falkor in November/December 2015. Methane samples were analyzed aboard the Falkor and helium samples were sealed in copper pipes and frozen (?) on the ship and later analyzed at the Helium Isotope Lab in Newport OR.
- My role in the project comes in to analyze the helium and methane data that has been collected through sample analysis.
- My role in the project comes in to analyze the helium and methane data that has been collected through sample analysis.
- Was the time between
- Add excel plot of the 18.2 cast (strongest signals) and combine methane and helium in the same plot. Change range of depths to 1500-4500 Remove lines between dots because it’s all over the place Make plots like this for methane Talk about which depth the plumes are concentrated and their height from this data Increase font size of axes and legend
- Snail vent – 18.2 17 North plume might be the result of distance from the main plume – as you move away from the main source, helium is diluted, but methane is diluted and consumed, so the signals from ongoing plumes become more divergent Have second plot with higher resolution in the weaker signals Add plot of vertical casts to show rise height, thickness, width of plumes Perseverance vent field
- Snail vent – 18.2 17 North plume might be the result of distance from the main plume – as you move away from the main source, helium is diluted, but methane is diluted and consumed, so the signals from ongoing plumes become more divergent Have second plot with higher resolution in the weaker signals Add plot of vertical casts to show rise height, thickness, width of plumes Perseverance vent field
- Add pictures of vents from 2016 cruise report under the strong signals We see that the plume at 15-16 North is first seen at 4100 mbsl and reaches up to around 3600 mbsl
- Add pictures here