1. The Ongoing and the Early Differentiation of the Earth: the Role of Volatiles Rajdeep Dasgupta June 26, 2008COMPRES

2. Volatiles and Solid Earth Science

4. Short-Term Carbon Cycle http://earthobservatory.nasa.gov/Library/CarbonCycle

5. Long-Term Carbon Cycle

6. C Fluxes – IN and OUT (How uncertain?) (Marty and Tolstikhin, 1998; Plank and Langmuir, 1998; Sleep and Zahnle, 2001; Jarrard, 2003; Resing et al., 2004; Hayes and Waldbauer, 2006)

7. Partial melting of carbonated eclogite (eclogite + CO 2 ) is likely to control the depth of release of crustal carbon in the mantle Release of Subducted Carbon – how, where ?

8. Deep Cycling of Carbon Dasgupta et al. (2004) - EPSL

9. Fate of Carbonated Eclogite in the Upwelling Mantle Deep Melting of Carbonated Eclogite in the Earth’s upper mantle and generation of carbonatitic melt Dasgupta et al. (2004) - EPSL

10. If carbonated eclogite melts very deep, solidus of peridotite+CO 2 controls loci of carbon storage and release

11. Experiments with Peridotite+CO 2 6.6 GPa, 1250 °C6.6 GPa, 1300 °C Dasgupta and Hirschmann (2006) - Nature

12. Solidus of Peridotite with trace CO 2 Dasgupta and Hirschmann (2006) - Nature Falloon and Green (1989) Deep Melting of Carbonated peridotite in the Earth’s upper mantle and generation of carbonatitic melt (with ~40 wt.% CO 2 ) For 30-350 ppm C, this melting generates 0.03-0.3 wt.% carbonatitic melt eclogite + CO 2

13. Geochemical Consequence of Deep Melting Dasgupta & Hirschmann (2006) - Nature 1  10 18 g of mantle/ yr 25% of the mantle/ Ga Release of highly incompatible tracers and volatiles U-Th-Pb-He and K-Ar, Rb-Sr, Sm-Nd may be strongly fractionated in the depleted residual peridotite and in small-degree carbonatitic melt If stored for long, both carbonatite extracted residue and carbonatite implanted metasomatized mantle lithology may evolve as geochemical reservoirs with distinct isotopic signatures.

14. Carbon in the Core?

15. Behavior of C during early Earth differentiation (metal-silicate equilibration)? C Partitioning of C during core-mantle equilibration Behavior of Carbon during magma ocean differentiation?

16. Solubility of Carbon in core melts? Carbon solubility determinations at 2 GPa at 1300-2500 °C Starting mix – Fe or Fe-5.2 wt.% Ni in graphite capsule Electron microprobe analysis of carbon content using LPC2 crystal and experimentally synthesized Fe 3 C and Fe 7 C 3 crystals as standards Dasgupta and Walker (2008) - GCA

17. Solubility of Carbon in core melts? Texture of quenched Fe±Ni-C melt Dasgupta and Walker (2008) - GCA

18. Carbon solubility in core melts Dasgupta and Walker (2008) - GCA

19. Constraint on D C (silicate-metal) from solubility Dasgupta and Walker (2008) - GCA

20. Constraint on D C (silicate-metal) from mantle carbon content Carbon content of the mantle? ￭ Measurement of CO 2 /Incompatible species ratio in glasses, fluids, gases and independent estimate of mantle He or Nb etc. CO 2 / 3 He, CO 2 / 4 He (e.g., Trull et al., 1993; Marty and Tolstikhin, 1998; Shaw et al., 2003; Resing et al., 2004) CO 2 /Ar (e.g., Tingle, 1998; Cartigny et al., 2001) CO 2 /Nb (e.g., Saal et al., 2002; Cartigny et al., 2008) CO 2 /Cl (e.g., Saal et al., 2002) Direct measurement of CO 2 in mantle derived melts/ glasses (MORB, OIB, Arc Lavas and melt inclusions) (e.g., Dixon et al., 1997; Bureau et al., 1998) Direct measurement of CO 2 in mantle-derived fluids (trapped gas bubbles in basalts, hydrothermal vent fluids, plumes) and gases (e.g., Aubaud et al., 2005)

21. Constraint on D C (silicate-metal) from mantle carbon content Dasgupta and Walker (2008) - GCA Batch segregation of core melt

22. Constraint on D C (silicate-metal) from mantle carbon content + metal solubility Dasgupta and Walker (2008) - GCA Batch segregation of core melt Fractional segregation of core melt

23. Carbon in the Core? Dasgupta and Walker (2008) - GCA 0.25 ± 0.15 wt.% C Core is likely to be the most enriched deep Earth reservoir of carbon ~48 x 10 24 g C in the core

24. Summary

25. Interested in the role of volatiles…? Rajdeep.Dasgupta@rice.edu The Road Ahead