PETROGRAPHY, MINERAL CHEMISTRY, AND PETROGENESIS OF ANTARCTIC SHERGOTTITE LEW88516

LEW88516 (LEW), like its near-twin ALH77005 (ALH), is a maskelynite-be aring harzburgite and an member of the SNC family of achondrites. LEW is texturally heterogenous, exhibiting both poikilitic (pyroxene oikoc rysts enclosing subhedral olivine and euhedral chromite) and non-poiki litic (cumulus framework of olivine and minor pyroxene, with interstit ial maskelynite and secondary minerals) textures. Pyroxenes in LEW app ear 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 A LH olivine observed. LEW olivine in non-poikilitic areas is substantia lly more iron-rich than olivine armored by pyroxene. Trace element and minor element patterns of LEW and ALH minerals are essentially identi cal and are consistent with closed-system, large-volume crystallizatio n of the major phases, followed by development of later phases after a ssembly of the crystal pile. Major element compositions show the effec ts of moderate near-solidus re-equilibration in both meteorites. The c ompositions of possible LEW parent magmas, calculated from mass-balanc e methods using the components of magmatic inclusions in large olivine grains, are very similar to those proposed earlier for ALH and the EE TA79001 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.