CUMULATE EUCRITE, DIOGENITE, AND NAKHLITE MELT INCLUSION ANALYSES: INVESTIGATING PARENT MELT CHARACTERISTICS OF ACHONDRITES FROM 4 VESTA AND MARS

The evolution of parent melts on Mars and 4 Vesta can be traced through the analyses of melt inclusions in cumulate achondrite meteorite samples. Primary melt inclusions record early parent melt compositions while secondary melt inclusions can reflect later changes in magmatic systems. Importantly, elemental compositions of such phases can highlight magmatic activity at different stages throughout parent melt evolution. Nakhlites, a group of Martian meteorites which show cumulate igneous textures, are dominantly composed of clinopyroxene and contain melt inclusions (e.g., Treiman, 2005). Cumulate eucrites and diogenites, part of the HED (howardite-eucrite-diogenite) meteorite clan believed to originate from 4 Vesta, also host primary and secondary melt inclusions (e.g., Drake, 2000, and references therein). This study will investigate melt inclusions from two nakhlites (NWA 11013 and NWA 13669), one cumulate eucrite (NWA 8564), and one diogenite (NWA 7831). Utilizing scanning electron microscopy (SEM), electron microprobe analysis (EMPA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), major, minor, and trace element compositions of melt inclusions will be acquired to determine the parent melt characteristics of our samples. Due to the complex emplacement history of nakhlites and evidence for contamination of light rare earth element (LREE) and chlorine-rich exogenous fluids in the Martian subsurface (Cartwright et al., 2013; McCubbin et al., 2013; Hicks et al., 2016; Udry and Day, 2018), investigating nakhlite melt inclusions will provide insight into the compositional evolution of the nakhlite cumulate suite. Primary nakhlite melt inclusion compositions should reflect a more depleted parent melt, while secondary melt inclusions should reflect enrichment via open system partitioning of LREEs in nakhlite magmas (Udry and Day, 2018). Lower incompatible trace element abundances have been noted within cumulate eucrites (Kumler and Day, 2021), likely reflecting a more depleted parent melt. Diogenites, which formed with or after eucrites (Yamaguchi et al., 2011), host melt inclusions that may record parent melt enrichment. Thus far in our study, we have identified melt inclusions in all of our samples and are working towards determining their composition.