Orthopyroxene Megacrysts in Toufassour Mesosiderite: Mineralogy and Origin

Many specimens of the Toufassour mesosiderite meteorite found in Tata (Morocco) in 2003 contain large (up to 1.5 cm) single crystals of orthopyroxene, the abundance of which appears to be greater than that found in other mesosiderites. The aim of this work was to study the mineralogy and origin of these megacrysts. The results obtained have shown that, in contrast to orthopyroxene phenocrysts, the megacrysts feature a chemical imbalance with preexisting phenocrysts (Opx, Cpx and Ol), which suggests that pyroxene megacrystals are not crystallized in the same silicate bath.