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With lots of discussions with Adam Dziewonski, Rick O’Oconnell

What do noble gases really say about mantle convection and the deep Earth volatile cycles. Work done with Helge Gonnermann, Rice. With lots of discussions with Adam Dziewonski, Rick O’Oconnell. After Barfod, 1999. MORBs: sample well-mixed degassed mantle with low 3 He/U+Th

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With lots of discussions with Adam Dziewonski, Rick O’Oconnell

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  1. What do noble gases really say about mantle convection and the deep Earth volatile cycles Work done with Helge Gonnermann, Rice With lots of discussions with Adam Dziewonski, Rick O’Oconnell

  2. After Barfod, 1999 MORBs: sample well-mixed degassed mantle with low 3He/U+Th OIBs: sample heterogeneous, less degassed mantle with high 3He/U+Th

  3. Preserving noble gases in a convecting mantleGonnermann and Mukhopadhyay, Nature 2009

  4. ~50% of slabs have gone into lower mantle over Earth history. The upper mantle has passed through the ridge system 3-7 times. Mass flux out of lower mantle = 0.5-1 times lower mantle mass. Very limited direct mixing between upper and lower mantle. UM concentration from ocean He flux

  5. A toy model for the carbon cycle 50% of slabs circulate in lower mantle and small degree of direct coupling between upper and lower mantle For q=1 (lower mantle), C/3He increases by 1.8; ~50% of C in LM still primordial. For q=5 (upper mantle), C/3He increases by 46; essentially no primordial C. . Initial C/3He is ~0.7 -1 x 108, present day C/3He is ~1-2 x108 in LM and ~2-3 x 109 in UM. C content of BSE is 80-250 ppm. Zhang&Zindler (1993) ->100 ppm

  6. Are there two distinct reservoirs in the mantle with 129Xe anomalies?

  7. Are there two distinct reservoirs in the mantle with 129Xe anomalies?

  8. The solid Earth volatile cycle If we put strong constraints on production rates of tectonic plates and how the flux of subducted plates is partitioned between upper and lower mantle, we can start putting strong constraints on volatile cycles and the injection of oxidants into the mantle.

  9. 5 RA 8 RA 3He/4He 50 RA 5 RA HIMU EM1 EM2 DMM FOZO 50 RA

  10. Estimated CO2 contents in parental magmasBased on measured noble gases in erupted lavas water depth

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