‘Normal’ Fe-Mg-Al-Cr Spinel Minerals in Chondritic Stratospheric IDPs

Introduction: Spinel minerals with 'normal' structure are common in extraterrestrial materials and can form via a large range of processes including nebular condensation, crystallization from liquid melts and sub-solidus metamor-phic reactions. Owing to their ability to accept a large range of cations in their crystal structures these minerals can be regarded as useful petrogenetic indicators which largely reflect their parental sources. In carbonaceous chondrites, for instance, multicomponent spinels present in Type 2 chondrules crystallized from silicate melts (drop-lets) rich in Fe, Cr, Mg and Al whereas nearly pure MgAl 2 0 4 spinels present in Type B CAIs formed in a nebu-lar environment consistent with high temperature condensation of refractory minerals. In this study we examine non-magnetite, non-magnesioferrite spinel minerals rich in Fe