Anmerkungen:
Tag der Verteidigung: 08.02.2023
Zusammenfassungen in deutscher und englischer Sprache
Beschreibung:
Micro- to nanometer-sized metal-volatile related inclusions have been investigated by a combined SEM-FIB-TEM approach within primitive meteorites Acfer 094 and QUE 97990. Acfer 094 contains polycrystalline sulfide-oxide assemblages with concentric character that, in some cases contain relict metal within their center. It was possible to constrain the formation scenario of these assemblages to a most likely solar nebula scenario, taking place prior to Acfer 094s’ parent body accretion. A probable formation scenario could be the reaction of primitive metal condensates with nebular gases such as H2S and H2O. It was possible to detect carlsbergite (CrN) inclusions within metal in QUE 97990 as well as roaldite (Fe4N) in Acfer 094. The crystallographic orientation relationships between metal and nitride confirm a formation of nitride from the metal, which indicates that at least the observed nitrides in Acfer 094 and QUE 97990 are the products of metal-gas interactions independent of sulfide-formation. Metal (Fe/Ni,Co,Cr) – H2/H2S experiments have been performed in order to verify the conclusions drawn from the results on natural samples. The experimentally produced samples were studied by a combined SEM-FIB-TEM approach as well. The experiments were performed at several temperatures (250 °C, 350 °C, and 550 °C) under solar nebula pressure conditions (10 mbar total pressure). The results from the highest temperature experimental run (550°C) are in good agreement with the observations made in Acfer 094, based both on chemical behavior of main (Fe, Ni) and minor (Co, Cr) elements as well as texture.