An Intrinsic Volatility Scale Relevant to the Earth and Moon

1. An Intrinsic Volatility Scale Relevant to the Earth and Moon Francis Albarède Ecole Normale Supérieure de Lyon Emmanuelle Albalat, ENS Lyon Cin-Ty Lee, Rice University, Houston

2. Water is one of the many volatile elements Why are planets from the inner Solar System so depleted in volatile elements?

3. Lunar pyroclastic glasses (lava fountaining) 74220 15426

4. Evidence for a wet Moon (1)Water in melt inclusions of orange glass 74220 (Hauriet al., 2011) > 1000 ppm indicates that some parts of the lunar interior contain as much water as Earth’s upper mantle.Mare basalts dry because of outgassing during eruption.Can we conclude that the Moon is wet?

5. The chemistry of the 74220 orange soil (fire fountain pyroclastics) is very unusual

6. Green glass 15425 outcrop

7. Evidence for a wet Moon (2)The water concentrations of some lunar apatites compare with their terrestrial equivalents 14053 14053 Boyce et al. (2010) Lunar apatite Ca10(PO4)6(OH,F,Cl)2 contains up to 6000 ppm water and in basalts hosts nearly all the water of the sample

8. Phosphorus and apatite saturationin lunar basalts • OH-bearing apatite Ca5(PO4)3(OH,F,Cl) is the ubiquitous host of terrestrial phosphate, whereas occurrence of the dry whittlockite (Ca,Mg)3(PO4)2 is an exception (Ionov et al., 2006) • Whittlockite, not apatite, is the common phosphate reservoir in the Moon (Jolliff et al., 1993), which is in itself a strong indication that the interior of the Moon is largely dry. • Upon fractional crystallization of lunar basalts, apatite only reaches saturation after 96.5% crystallization when the residual melt rises to 65% SiO2

9. Some ‘magic’ elemental ratios do not change upon melting and melt crystallization • Principle introduced by Schilling et al. (1980) and Hofmann & White (1983) • ‘Magic’ ratios in magmatic products can be used to infer ratios in the source mantle • Important examples: Rb/Cs, Sm/Hf, K/U • Magmatically unfractionated volatile/refractory pairs H2O/Ce, K/U, Rb/Ba, Ge/Si, and now Zn/Fe, are of particular importance to understand planetary inventories of volatile elements D=Dsol/melt Hofmann Hofmann & White (1983)

10. Rb is depleted in the Moon relative to the Bulk Silicate Earth (Ba refractory).Orange and green glasses behave ‘normally’. GEOROC-PetDB ID-TIMS Gast-Wiesmann-Hubbard-Nyquistdatabase (1975)

11. K is depleted in the Moon relative to the Bulk Silicate Earth (U refractory).Orange and green glasses behave normally. GEOROC-PetDB ID-TIMS Gast-Wiesmann-Hubbard-Nyquistdatabase (1975)

12. LeRoux et al. (2010) demonstrated that terrestrial Zn/Fe ratios are insensitive to magmatic processes.New data: Zn is very depleted in the Moon relative to BSE The Earth: GEOROC-PetDB New LA-ICP-MS data on lunar mineral and glasses!

13. Using the H2O/Ce ratio

14. Lodder’s (2003) condensation temperature scale

15. T50 varies with PH2 Nebular condensation temperatures are not relevant to the Earth-Moon system: • A lunar disk made of silicate vapor should be less reducing than the Solar Nebula, which is chiefly composed of H2 • Condensation temperatures of mineral phases depend on the partial pressure of the elements in the cooling nebular gas and therefore on the total gas pressure • Contrary to the Solar Nebula, in which the decline in total pressure does not change with condensation and mostly reflects the declining thermal energy of non-condensable hydrogen, the gas of the lunar nebular disk is dominated by elements removed at an early stage by condensation of high-temperature phases, mostly as olivine, pyroxene, plagioclase and metal

16. Calibration of an intrinsic volatility scale:Relationship between bond energy and T50condensation temperature in the Solar Nebula (H2-rich)The slope of this line is a function of PH2

17. Testing how the new volatility scale correlates with abundances in the Bulk Silicate Earth (McDonough, 1995) and the Moon (O’Neill, 1991)

18. The Moon • As forcefully established by careful work on Apollo samples in the 70s, the source of mare basalts is dry • As established by Hauri et al. (2011) and Saal et al. (2013), the source of the unusual pyroclastic orange and green glasses contain volatiles in excess of the surrounding mantle, but this does not make the Moon a wet planetary body

19. When were volatiles delivered? Age of the lunar impact Albarede (2009) Borg et al. (2011)

20. Predictions of apatite saturation using MELTS and Watson’s (1979) experimental data:96.5 percent fractional crystallization before apatite saturation

21. About unusual ‘wet’ samples Based on our observations of several hundred spheres from both Apollo and Luna missions, the classic micromound coating is unique to the Apollo 15 green and Apollo 17 orange and black droplets. Although some investigators have proposed various impact sequences to produce these unique droplets, the volcanic fire fountain origin is favored. (citation Clanton et al., 1978). Goldberg (1976): fluorine is restricted to coatings 74220: photo by K Hollocher (2003)

22. H2O in an unusual sample, orange soil 74220, a volatile and incompatible element-rich pyroclastic rock next to a 30 Ma crater Hauri et al. (2011)

23. The 74220 site next to the 30 Ma old Shorty Crater