Relative chronology of crust formation on asteroid Vesta: Insights from the geochemistry of diogenites

Jean-Alix J-A Barrat (1, 2) , A. Yamaguchi (3, 4) , B. Zanda (5) , Claire Bollinger (1, 2) , Marcel Bohn (1, 2)

1 LDO - Domaines Océaniques
2 UEB - Université européenne de Bretagne - European University of Brittany
3 Antarctic Meteorite Research Center
4 Department of Polar Science
5 LMCM - Laboratoire de Minéralogie et Cosmochimie du Muséum

The eucrites and diogenites are meteorites that probably originate from asteroid 4-Vesta. The upper part of the crust of this body is certainly composed of eucrites which are basaltic or gabbroic rocks. Diogenites are ultramafic cumulates whose relationships with eucritic lithologies are unknown. Here, we show that the orthopyroxenes of some diogenites display very deep negative Eu anomalies (Eu/Eu* close to 0.1 or lower). The contamination of the parental magmas of diogenites by melts derived by partial melting of the eucritic crust can satisfactorily explain the range of the Eu anomalies displayed by diogenites. Thus, these anomalies are the first firm indication that parental melts of diogenites have intruded the eucritic crust, and consequently are younger than eucrites.

Domains: Geochemistry; Global Changes

Jean-Alix J-A Barrat, A. Yamaguchi, B. Zanda, Claire Bollinger, Marcel Bohn. Relative chronology of crust formation on asteroid Vesta: Insights from the geochemistry of diogenites. Geochimica et Cosmochimica Acta, 2010, 74 (21), pp.6218-6231. ⟨10.1016/j.gca.2010.07.028⟩. ⟨insu-00517866⟩