Trace and minor elements in ureilites and deuterium-enrichments in several primitive meteorites: Characteristics and geochemical implications.

摘要

his thesis consists of two distinct lines of study. The first part presents trace element (particularly REE) microdistributions in ureilites. Comprehensive ion microprobe measurements demonstrate that LREE enrichments observed in some ureilites are located in their C-rich matrix areas. Ion imaging, used for the first time to examine the microdistribution of REEs in C-rich areas, indicates that these enrichments are not carried by a discrete minor mineral phase. In most C-rich areas, LREEs are homogeneously distributed and are probably absorbed on the fine-grained matrix material. It is unlikely that the LREEs were introduced by late-stage metasomatism on the ureilite parent body. Secondary alteration, that occurred on the surface of the Earth, is a possible alternative. REEs and other elements were also determined for various lithic and mineral clasts in three polymict ureilites. The results suggest that melt clasts, combined with plagioclase clasts and some high-Ca pyroxenes, probably represent the "missing" basaltic component associated with monomict ureilites.;The second part of this thesis includes an investigation of the distribution of D-rich materials in Renazzo (CR) matrix, and D/H measurements of glassy and phyllosilicate spherules in Al Rais (CR) and Orgueil (CI). Typical black fragments from Renazzo matrix are modestly enriched in deuterium, with