Siderophile, lithophile and mobile trace elements in the Lunar Meteorite Allan Hills 81005

Abstract

Contents of siderophilic As, Au, Co, Ga and Sb, volatile/mobile Ag, Bi, Cd, In, Se, Te, Tl and Zn and lithophilic Cs, Rb and U determined by radiochemical neutron activation analysis in ALH A81005 are similar to those of lunar highlands samples returned by Apollo missions, indicating this meteorite's lunar origin. Five elements (Co, Ga and lithophiles) reflect lunar crustal processes while the remaining 11 siderophile and mobile elements (including the most mobile ones) indicate 1.4 ± 0.5% micrometeorite (Cl equivalent) admixture or enrichment by thermal redistribution on the moon. Thus, in contrast to L chondrites where severe shock caused trace element loss, impact‐launching of ALH A81005 to Earth was free of substantial (≤20 GPa) shock loading. In this light, a Martian origin for severely shocked SNC meteorites is plausible.