Uranium and thorium abundances in stony meteorites: 2. The achondritic meteorites

Abstract

Neutron activation determinations of U and Th abundances in two diogenites (Ellemeet, Johnstown), a howardite (Binda), a eucrite (Moore County), a nakhlite (Nakhla), and an angrite (Angra dos Reis) are in agreement with the hypothesis that these achondrites have formed as a result of differentiation of an ordinary chondrite magma. The Bishopville enstatite achondrite (aubrite) has U and Th abundances consistent with an origin directly from an enstatite chondrite of the Hvittis type by simple melting and gravity separation of metal and sulfide phases.