Differentiated Meteorites

This project aims in making some progress in the understanding of differentiated meteorites - in particular of iron meteorites and basaltic achondrites. There exist many conflicts between the popular models for meteorite genesis and reality and we would like to find solutions to at least a few of them. Our preliminary investigations of metal, schreibersite and carbon in the Campo del Cielo (IAB), Canyon Diablo (IAB) and Elbogen (IID) iron meteorites revealed that: (a) Metal in graphite nodules of Canyon Diablo and Campo del Cielo is chemically inhomogeneous and has fractionated siderophile trace element abundances. The fractionation of refractory siderophile elements observed cannot be explained by fractional crystallization and inhomogeneities can not be expected in igneous metal at all. We suspect, that low temperature processes were involved in the formation of iron meteorites rather than the high- temperature processes preferred in the popular genetic models. (b) Schreibersite in Campo del Cielo and other iron meteorites is also chemically highly heterogeneous. Chemical variation is extreme and is correlated with the size of the crystals. Trace element abundances follow the Ni abundance trend and are also strongly fractionated - in a way similar to their fractionation in Canyon Diablo metal. Consequently, also schreibersites are far out of equilibrium with the metal they are embedded in and indicate a low temperature formation by a process similar to that which formed the metal. We suspect that metal carbonyls could be involved. This is supported by preliminary data on C isotope abundances in graphite from Campo del Cielo which is highly heterogeneous on a m scale. In any case, we would like to investigate in proper detail the mineral-association and the major, minor and trace element abundances in co- existing phases of a few iron meteorites, notably San Juan (a recently found mass of the Campo del Cielo, Argentina, iron), Canyon Diablo, Elbogen and Netschaevo. In addition, the isotopic composition of carbon in these irons (where present) as well as of N and H contained in the carbon shall be determined. Parallel to the study of irons we want to study the geochemistry of glasses from achondrites. Our comprehensive study of meteoritic glasses (FWF project P13975-GEO) revealed the omnipresence of refractory glasses in chondrites and achondrites. We would like to study in detail glasses from the achondrites Cachari (eucrite, Argentina), North West Africa XX (new howardite) and D`Orbigny (angrite, Argentina). We suspect that glass could have been formed in the early solar nebula rather than in igneous processes on planetesimals as predicted by the achondrite genesis models. We would like to find solutions to at least some of the open problems in meteorite genesis. These attempts will be undertaken in an international co-operative research with institutions and scientists from Argentina, USA, Germany and Austria.

This project aims in making some progress in the understanding of differentiated meteorites - in particular of iron meteorites and basaltic achondrites. There exist many conflicts between the popular models for meteorite genesis and reality and we would like to find solutions to at least a few of them. Our preliminary investigations of metal, schreibersite and carbon in the Campo del Cielo (IAB), Canyon Diablo (IAB) and Elbogen (IID) iron meteorites revealed that: (a) Metal in graphite nodules of Canyon Diablo and Campo del Cielo is chemically inhomogeneous and has fractionated siderophile trace element abundances. The fractionation of refractory siderophile elements observed cannot be explained by fractional crystallization and inhomogeneities can not be expected in igneous metal at all. We suspect, that low temperature processes were involved in the formation of iron meteorites rather than the high-temperature processes preferred in the popular genetic models. (b) Schreibersite in Campo del Cielo and other iron meteorites is also chemically highly heterogeneous. Chemical variation is extreme and is correlated with the size of the crystals. Trace element abundances follow the Ni abundance trend and are also strongly fractionated - in a way similar to their fractionation in Canyon Diablo metal. Consequently, also schreibersites are far out of equilibrium with the metal they are embedded in and indicate a low temperature formation by a process similar to that which formed the metal. We suspect that metal carbonyls could be involved. This is supported by preliminary data on C isotope abundances in graphite from Campo del Cielo which is highly heterogeneous on a m scale. In any case, we would like to investigate in proper detail the mineral-association and the major, minor and trace element abundances in co-existing phases of a few iron meteorites, notably San Juan (a recently found mass of the Campo del Cielo, Argentina, iron), Canyon Diablo, Elbogen and Netschaevo. In addition, the isotopic composition of carbon in these irons (where present) as well as of N and H contained in the carbon shall be determined. Parallel to the study of irons we want to study the geochemistry of glasses from achondrites. Our comprehensive study of meteoritic glasses (FWF project P13975-GEO) revealed the omnipresence of refractory glasses in chondrites and achondrites. We would like to study in detail glasses from the achondrites Cachari (eucrite, Argentina), North West Africa XX (new howardite) and D`Orbigny (angrite, Argentina). We suspect that glass could have been formed in the early solar nebula rather than in igneous processes on planetesimals as predicted by the achondrite genesis models. We would like to find solutions to at least some of the open problems in meteorite genesis. These attempts will be undertaken in an international co-operative research with institutions and scientists from Argentina, USA, Germany and Austria.