What Were the Major Factors That Controlled Mineralogical Similarities and Differences of Basaltic, Lherzolitic and Clinopyroxenitic Martian Meteorites within Each Group?

Introduction: Twelve Martian meteorites that have been recovered so far are classified into five groups (basalt, lherzolite, clinopyroxenite, dunite, or-thopyroxenite) mainly from petrology and chemistry [e.g., 1]. Among them, the dunite and orthopyroxenite groups consist of only one meteorite, respectively (dunite: Chassigny, orthopyroxenite: ALH84001). The basalt group is the largest group and consists of four meteorites (Shergotty, Zagami, EETA79001, QUE94201). The lherzolitic and clinopyroxenitic groups consist of three meteorites, respectively (lher-zolite: ALH77005, LEW88516, Y793605, clinopyrox-enite: Nakhla, Governador Valadares, Lafayette). These meteorites within each group are generally similar to the others, but none of them is paired with the others. In this abstract, we discuss what were the major factors that controlled mineralogical similarities and differences of basaltic, lherzolitic and clinopyrox-enitic meteorites within each group. This may further help drawing useful information to understand their petrogenesis and original locations on Mars in general. Basalt: Pyroxene and maskelynite (shocked pla-gioclase glass) are major minerals in the basaltic Martian meteorites. Pigeonite and augite show two distinct textural occurrences of chemical zoning patterns. In Shergotty and Zagami, pigeonite and augite are usually present as separate grains that are zoned from Mg-rich core to Fe-rich rim, respectively. Both pigeonite and augite usually have homogeneous cores, considered to be cumulus phases. Zagami pyroxenes are not zoned as extensively as those in Shergotty, but their mineralogy is quite similar. On the other hand, pigeonite and au-gite in EETA79001 and QUE94201 are both present in individual composite grains. These pyroxenes are complexly zoned, and typically the cores are Mg-rich pigeonites, mantled by Mg-rich augite, and the rims are Fe-rich pigeonite. Maskelynite compositions also correspond to differences in pyroxene zoning. Maskelynites in Shergotty and Zagami are more alkali-rich than those in EETA79001 and QUE94201, suggesting later crystallization. Shergotty and Zagami maskelynites indicate growth from the surrounding pyroxene walls in interstitial melts, whereas EETA79001 and QUE94201 normally grew from core to rim. FeO in the maskelynite cores is different between Shergotty and Zagami (0.5-0.6 wt%) and EETA79001 and QUE94201 (0.3-0.4 wt%). The lower