Evidence for K-rich terranes on Vesta from impact spherules

available online at http://meteoritics.org Evidence for K-rich terranes on Vesta from impact spherules J. A. BARRAT1, 2*, M. BOHN1, 2, PH. GILLET3, and A. YAMAGUCHI4 1Université Européenne de Bretagne, France 2CNRS UMR 6538 (Domaines Océaniques), U.B.O.-I.U.E.M., Place Nicolas Copernic, 29280 Plouzané Cedex, France 3Laboratoire des Sciences de la Terre, CNRS UMR 5570, Université de Lyon, Ecole Normale Supérieure de Lyon, 46 Allée d Italie, 69364 Lyon Cedex 7, France 4Antarctic Meteorite Research Center, National Institute of Polar Research, 1-9-10 Kaga, Itabashi, Tokyo 173-8515, Japan *Corresponding author. E-mail: [email protected] (Received 29 May 2008; revision accepted 07 November 2008) Abstract The howardite-eucrite-diogenite (HED) clan is a group of meteorites that probably originate from the asteroid Vesta. Some of them are complex breccias that contain impact glasses whose compositions mirror that of their source regions. Some K-rich impact glasses (up to 2 wt% K2O) suggest that in addition to basalts and ultramafic cumulates, K-rich rocks are exposed on Vesta s surface. One K-rich glass (up to 6 wt% K2O), with a felsic composition, provides the first evidence of highly differentiated K-rich rocks on a large asteroid. They can be compared to the rare lunar granites and suggest that magmas generated in a large asteroid are more diverse than previously thought.The howardite-eucrite-diogenite (HED) clan is a group of meteorites that probably originate from the asteroid Vesta. Some of them are complex breccias that contain impact glasses whose compositions mirror that of their source regions. Some K-rich impact glasses (up to 2 wt% K2O) suggest that in addition to basalts and ultramafic cumulates, K-rich rocks are exposed on Vesta s surface. One K-rich glass (up to 6 wt% K2O), with a felsic composition, provides the first evidence of highly differentiated K-rich rocks on a large asteroid. They can be compared to the rare lunar granites and suggest that magmas generated in a large asteroid are more diverse than previously thought.