Basaltic volcanism on the eucrite parent body: Petrology and chemistry of the polymict eucrite ALHA80102

Abstract

The polymict eucrite meteorite ALHA80102 i s an unequilibrated breccia of basaltic and gabbroic clasts in a fragmental matrix. Clasts include basalts of many textural types, cumulate gabbro, black “glass,” and ferroan troctolite (plagioclase, silica, Fe‐rich olivine, ilmenite, mesostasis). Ferroan troctolite has not been previously reported from eucrites or howardites; it is interpreted as the end‐product of fractional crystallization of eucritic magmas. Bulk and trace element compositions (by electron microprobe and INAA) of clasts and matrix from ALHA80102 are similar to those of other eucrites; the meteorite contains clasts similar to Juvinas and to Stannern. A clast of cumulate eucrite gabbro is enriched in the light rare earths (La/Lu=2XCI). This clast is interpreted as an unrepresentative sample of metamorphically equilibrated gabbro; LREE‐enriched magmas need not be invoked. ALHA80102 is similar to other polymict eucrites from the Allan Hills and may be paired with ALHA76005, ALHA77302, and ALHA78040.