Characterization of the lithological contact in the shergottite EETA79001- A record of igneous differentiation processes on Mars

Elephant Moraine (EET) A79001 is the only Martian meteorite that consists of both an olivine-phyric shergottite (lithology A) and a basaltic shergottite (lithology 13). The presence of these lithologies in one rock has previously been ascribed to mixing processes (either magmatic or impactinduced). Here we present data regarding phase changes across the contact between the lithologies. These data show that the contact is gradational and suggest that it is a primary igneous feature consistent with crystallization of a single cooling magma. We present a model to establish a petrogenetic connection between an olivine-phyric and a basaltic shergottite through differentiation.