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Volatile Recycling at Subduction Zones

Volatile Recycling at Subduction Zones. Terry Plank, Lamont Doherty Earth Observatory. The Subduction Factory. Is the Ocean Shrinking?. Water Fluxes During Subduction. 60% of structurally- bound H 2 O released. Hacker (2008) G3; Jarrard (2003) G3. Water Fluxes During Subduction.

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Volatile Recycling at Subduction Zones

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  1. Volatile Recycling at Subduction Zones Terry Plank, Lamont Doherty Earth Observatory The Subduction Factory

  2. Is the Ocean Shrinking?

  3. Water Fluxes During Subduction 60% of structurally- bound H2O released Hacker (2008) G3; Jarrard (2003) G3

  4. Water Fluxes During Subduction H2O Output? H2O % in magma Magma Mass Flux 60% of structurally- bound H2O released Hacker (2008) G3

  5. Arc Data: 2000 (SubFac Science Plan) Centam MORB 0 1 2 3 4 5 6 7 8 H2O (least degassed) wt%

  6. Arc Data: 2009 Centam Tonga MORB Mexico Marianas Kamchatka Aleutians 0 1 2 3 4 5 6 7 8 H2O (least degassed) wt% 3.9 wt% H2O +/- 1.0 (1 stdev)

  7. Average Arc Growth Rates Suyehiro et al. (1996) Science Holbrook et al (1999) Geology Izu Arc (km3/km/Ma) 28 (Reymer&Schubert, 1984) 66 (Suyehiro et al., 1996) 56-60 (Dimalanta et al., 2002) Duration: 47 Ma Aleutian Arc 23-33 (Reymer&Schubert, 1984) 75-82 (Holbrook et al., 1999) 59-61 (Dimalanta et al., 2002) 89-182 (Jicha et al., 2006) Duration: 46 Ma

  8. Th output (g/yr) = CTh * Magma Mass Flux Th input (g/yr) 100 km Hebert et al (2009)

  9. Water Fluxes During Subduction 4 +/- 1 wt% H2O arcs 60 +/- 20 km3/km/Ma 3.0E8 = 40 +/- 20% recycled to arc 60% of structurally- bound H2O released Hacker (2008) G3

  10. 1000 Relative sea level change (meters) 800 40% 600 50% 400 70% 200 600 300 0 Millions of years before present Subduction of Water Lowering Sea Level 50% water recycled to surface from Rupke et al. (2004)

  11. Global Sea Level Variations meters Sea level fall over past ~ 600 Ma due to subduction of water?? Millions of years before Present Hallam (1982); and Wallman (2001)

  12. Ocean shrinking Ocean growing Size of Ocean today hotter mantle cooler mantle from Rupke et al, Earth and Planetary Science Letters (2004)

  13. 2% H2O in 4 km mantle 5.7

  14. Water Fluxes During Subduction All serpentine- bound H2O bypasses arc? Hacker (2008) G3

  15. Lose ocean In 1.7 Ga! past arc 0.5 2.5 2% H2O in 4 km mantle 5.7 5.4

  16. Wiens/Lizarralde MARGINS experiment

  17. Subducting Carbonate and CO2 Cycling

  18. GLOSS - global subducting sediment Plank & Langmuir (1998) Centam Plank, et al (2002) Geology

  19. Altered oceanic crust Alt figure?? (1999) GCA

  20. CO2 Output?? Figure from Wallace (2005) JVGR

  21. ? Melt Inclusions - minimum CO2 Benjamin et al. (2007) JVGR -- Irazu Volcano, Costa Rica

  22. Global Flux Estimates from Wallace (2005) JVGR

  23. C Flux in & out of the mantle Input Output 25% (Alt & Teagle, 1999; Sleep & Zahnle, 2001; Jarrard, 2003) Courtesy of M. Hirschmann

  24. Centam, CO2 flux from slab Gorman et al (2006) G3

  25. Typical CO2/3He in Centam despite major carbonate subduction Shaw et al (2003) EPSL

  26. H2O Recycling CO2 Recycling • 25% returned to arc • decarbonation? • CO2 fluxes out volcanoes • 40-60% returned to arc • serpentine subduction? REE/Th

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