Petrography, mineral chemistry, and petrogenesis of Antarctic Shergottite LEW88516

LEW88516 (LEW), like its near-twin ALH77005 (ALH), is a maskelynite-bearing harzburgite and a member of the SNC family of achondrites. LEW is texturally heterogenous, exhibiting both poikilitic (pyroxene oikocrysts enclosing subhedral olivine and euhedral chromite) and non-poikilitic (cumulus framework of olivine and minor pyroxene, with interstitial maskelynite and secondary minerals) textures. Pyroxenes in LEW appear to be slightly more iron-rich and more varied in composition than those in ALH. LEW olivines have distinctly higher Fe contents; most of the olivine grains in LEW have compositions more iron-rich than any ALH olivine observed. LEW olivine in non-poikilitic areas is substantially more iron-rich than olivine armored by pyroxene. Trace element and minor element patterns of LEW and ALH minerals are essentially identical and are consistent with closed-system, large-volume crystallization of the major phases, followed by development of later phases after assembly of the crystal pile. Major element compositions show the effects of moderate near-solidus re-equilibration in both meteorites. The compositions of possible LEW parent magmas, calculated from mass-balance methods using the components of magmatic inclusions in large olivine grains, are very similar to those proposed earlier for ALH and the EETA79001 shergottite. While the subtle differences between LEW and ALH suggest they are not part of the same fall, it is likely that they are derived from the same igneous processes.