1 / 30

What is the role of Subduction in Deep Earth Volatile Cycles?

What is the role of Subduction in Deep Earth Volatile Cycles?. Marc Hirschmann University of Minnesota. Earth’s Deep Volatile Cycles. Hydrogen. Carbon. (diagram courtesy of J Phipps-Morgan). Influence of Modern Tectonics on Deep Earth Volatile Cycles. Possibilities: 1. Net Outgassing

vianca
Download Presentation

What is the role of Subduction in Deep Earth Volatile Cycles?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. What is the role of Subduction in Deep Earth Volatile Cycles? Marc Hirschmann University of Minnesota

  2. Earth’s Deep Volatile Cycles Hydrogen Carbon (diagram courtesy of J Phipps-Morgan)

  3. Influence of Modern Tectonics on Deep Earth Volatile Cycles Possibilities: 1. Net Outgassing 2. Net Ingassing 3. Quasi-steady state

  4. Phanerozoic sea level variation H2O must be near steady state Miller et al., Science 2005

  5. H/C Ratios of Chondritic Meteorites Kerridge, 1985; Robert+Merlivat, 1979; McNaughton et al. 1981; Grady et al., 1989; Javoy, 1998

  6. H/C ratio of the mantle: Evidence from undegassed basalts

  7. Simple Model for H and Cin the Bulk Silicate Earth (BSE) • H/C of exosphere=1.95±0.15 • H/C of MORB source=0.75±0.25 • H/C of OIB source=0.5±0.3 • H2O in MORB source=100±50 ppm • H2O in OIB source=600±300 ppm • OIB source=10 to 70% of mantle • No hidden volatile-rich reservoirs • Sum these in a Monte Carlo simulation to give H/C of the mantle and the BSE.

  8. H/C ratio of the mantle

  9. H/C ratio of the Bulk Silicate Earth

  10. H/C ratios of principal Earth and cosmochemical materials

  11. Why is the H/C Ratio of the Exosphere Much Greater than the Mantle H/C Ratio? Volcanic outgassing has the opposite effect (Coutgassing>H outgassing) Loss of volatiles to space has the opposite effect (Cescape<H escape) *Preferential Subduction of Carbon *Remnant of events in Deep Time - Loss of massive CO2-rich atmosphere - Retention of C during magma ocean degassing - Early massive return of C to mantle

  12. Dasgupta et al. (2004)

  13. Evolution of exosphere by preferential subduction of C (Total H subducted, C/H ratio of subducted mass)

  14. Evolution of exosphere by preferential Subduction of C

  15. carbonates mantle organic carbon Hayes and Waldbauer, 2006

  16. The exosphere carbon reservoir is dominated by continental sediments…… Age distribution of present-day continental sediments …and so the surface carbon reservoir grows with the continents. Veizer and Mackenzie, 2004

  17. H/C evolution of the Exosphere (?)

  18. Zahnle et al. 2007

  19. Impact Ejecta (lunar glass beads) (highly susceptible to reaction with atmospheric CO2) Sleep and Zahnle, 2001

  20. H/C evolution of the Exosphere

  21. Carbon may not be subductable in early, hot subduction zones

  22. H/C ratios of principal Earth and cosmochemical materials

  23. H/C evolution of the Exosphere Net C ingassing Net C outgassing

More Related