Abundances and distribution of volatile trace elements in chondritic meteorites and their components
Zusammenfassung der Projektergebnisse
Bulk trace element compositions for up to 51 elements within 16 randomly selected CAIs from R chondrites were determined using LA-ICP-MS. The R chondrite CAIs are characterized by a variety of patterns including the classical patterns of Group I, III, and V which were established in Allende inclusions and a number of other patterns. The latter comprise patterns similar to the classical, fractionated Group II and inclusions displaying unfractionated flat patterns with a superimposed negative Eu anomaly. REE enrichments were typically measured between ~5 and ~30 times CI for most elements. Two inclusions from metamorphosed lithologies classified as Group I are characterized by low abundances around CI. The observed REE patterns and the abundances of the other trace elements measured indicate complex formation and evolution processes. These include fractional condensation with removal of an ultra-refractory component, equilibrium condensation with complete or incomplete condensation of the most volatile elements, possibly evaporation and/or distillation, as well as metamorphic redistribution of certain elements. In order to obtain a more reliable and representative data set and to gain further insights into the formational conditions of CAIs found in R chondrites, additional measurements should be conducted.
