Extensive volatile loss during formation and differentiation of the Moon

Chizu Kato (1, 2) , Frédéric Moynier (2, 3) , Maria C Valdes (4) , Jasmeet K Dhaliwal (5) , James Day (6, 5)

1 Department of Earth and Planetary Sciences [St Louis]
2 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
3 IUF - Institut universitaire de France
4 WUSTL - Washington University in Saint Louis
5 SIO - UC San Diego - Scripps Institution of Oceanography
6 Geosciences Research Division [La Jolla]

Low estimated lunar volatile contents, compared with Earth, are a fundamental observation for Earth-Moon system formation and lunar evolution. Here we present zinc isotope and abundance data for lunar crustal rocks to constrain the abundance of volatiles during the final stages of lunar differentiation. We find that ferroan anorthosites are isotopically heterogeneous, with some samples exhibiting high d 66 Zn, along with alkali and magnesian suite samples. Since the plutonic samples were formed in the lunar crust, they were not subjected to degassing into vacuum. Instead, their compositions are consistent with enrichment of the silicate portions of the Moon in the heavier Zn isotopes. Because of the difference in d 66 Zn between bulk silicate Earth and lunar basalts and crustal rocks, the volatile loss likely occurred in two stages: during the proto-lunar disk stage, where a fraction of lunar volatiles accreted onto Earth, and from degassing of a differentiating lunar magma ocean, implying the possibility of isolated, volatile-rich regions in the Moon's interior.

Mots clés: LUNAR VOLCANIC GLASSES; ISOTOPE FRACTIONATION; ZINC; ORIGIN; IRON; ABUNDANCES; COPPER; WATER; EARTH

Domaines: Planète et Univers [physics]

Chizu Kato, Frédéric Moynier, Maria C Valdes, Jasmeet K Dhaliwal, James Day. Extensive volatile loss during formation and differentiation of the Moon. Nature Communications, 2015, 6, ⟨10.1038/ncomms8617⟩. ⟨insu-02611933⟩