Artificial meteor ablation studies: Iron oxides

Abstract

Artificial meteor ablation was performed on natural minerals composed predominately of magnetite and hematite by using an arc-heated plasma stream of air. Analysis indicates that most of the ablated debris was composed of two or more minerals. Wustite, a metastable mineral, was found to occur as a common product. The ‘magnetite’ sample, which was 80% magnetite, 14% hematite, 4% apatite, and 2% quartz, yielded ablated products consisting of more than 12 different minerals. Magnetite occurred in 91% of the specimens examined, hematite in 16%, and wustite in 39%. The ‘hematite’ sample, which was 96% hematite and 3% quartz, yielded ablated products consisting of more than 13 different minerals. Hematite occurred in 47% of the specimens examined, magnetite in 60%, and wustite in 28%. The more volatile elements (Si, P, and Cl) were depleted by about 50%. Also the relative abundance of Fe increased as a result of both volatile depletion (loss of Si, P, Cl, and Ca) and reduction in its oxidation state. Hematite was converted to magnetite in the ablation zone along the front face of the sample. Also quartz and apatite minerals reacted with the iron oxide melt to form an Fe-rich glass consisting of varying amounts of Si, P, Cl, and Ca, depending on the accessory minerals available at the time of melting. These glass phases occurred as unusual myrmekiticlike intergrowths, which are unique textural indicators of the environment through which the material has survived. The chemistry and mineralogy of these phases remain the only trace of the original minerals. This study has shown that artificially created ablation products from iron oxides exibit unique properties that can be used for identification. These properties are morphologic characteristics, textural parameters, and the existence of metastable minerals and depend on the composition of the original material and the environmental conditions of formation.