Petrography and mineralogy of two basalts and olivine‐pyroxene‐spinel fragments in achondrite EETA79001

Three lithologies occur in shocked achondrite EETA79001: A1, exotic irregular crystals and clusters of coarse‐grained olivine (Fo 81–55 :CaO 0.2, Cr 2 O 3 0.06, NiO 0.5 wt.%), low‐Ca pyroxene (En 82 Wo 2 ‐ En 58 Wo 12 ) and low‐Ti chromite (Cr 2 O 3 59, FeO 27, TiO 2 0.7 wt.%) A2 basaltic host to A1 containing pyroxene (mainly pigeonite En 67 Wo 12 ‐ En 52 Wo 13 ), maskelynite (An 61–55 Or 0.7 ,), high‐Ti chromite (some rimming low‐Ti chromite), whitlockite, minor Cl‐apatite, ilmenite, pyrrhotite, and mesostasis; and B, a homogeneous basalt containing augite laths (∼En 40–50 Wo 25–35 ) in a matrix of pigeohite‐augite, maskelynite (An 62–56 Or 1.2 )ulvöspinelilmenite intergrowth, whitlockite, Cl‐apatite, and mesostasis. Mineral compositions indicate an oxidation state similar to that of shergottites. Lithology A1 represents an unmetamorphosed cumulate that was disrupted and partly resorbed by a basaltic magma. Incorporation of low‐Ca magnesian pyroxenes and olivine increased the Mg/Fe ratio of the basaltic magma responsible for A2, and resulted in abundant crystallization of pigeonite. Lithology B was generated from a distinct magma lacking fragments of A1. The parental spinel harzburgite of A1 was not annealed, and is probably a near‐surface igneous cumulate from a shergottite‐type basalt. Ringwood (?) and majorite (?) were found in shock veins.