Are terrestrial ferropicrites analogues of Martian rocks?

Introduction: The SNC meteorites and the Pathfinder and MER Rover data represent our only information on individual rocks on the Martian surface, and therefore our only glimpse into Martian igneous processes. Because of this limitation, terrestrial analogues would provide a wealth of additional information. Analogies to terrestrial rocks have been made for the meteorites and Pathfinder rock but the differences have suggested that numerous chemical disparities exist between terrestrial and Martian magmas. However, these comparisons have been primarily based on terrestrial basalts and terrestrial peridotite nodules. The potential for better analogues was shown by Lentz et al. who compared the nakhlite meteorites with Theo‘s flow, a pyroxenite flow in Ontario, Canada [1]. We have looked for alternative terrestrial analogues, in order to better understand martian magmatic processes. Terrestrial ferropicrites. Terrestrial ferropicrites are volcanic rocks, commonly associated with tholeiitic flood volcanics, alkalic extrusives, and more evolved rhyolites and dacites [2-4]. They consist of a sequence of igneous rocks: a basal olivine cumulate layer, a mid-layer clinopyroxenite, and an olivine or clinopyroxene spinefex-textured top [2, 5]. The mineralogic sequence is comparable to the chassignites, nahklites, and olivine-phyric shergottites, respectively. Although detailed petrologic studies have been done on the ferropicrites, their formation history is still debated. Some workers suggest that the ferropicrites represent primitive liquid formed in pockets of Fe-rich streaks in the terrestrial mantle [7]. Others have suggested that the ferropicrites are partial cumulates containing evolved liquids [2]. Questions regarding the origin as “liquids” or partial cumulates are analogous to the questions raised about the origin of the olivinephyric shergotties.