Mineralogy and bulk chemistry of chondrules and matrix in petrologic type 3 chondrites : implications for early solar system processes

A detailed electron microprobe (EMP) study was performed on chondrules of various textural types in four petrologic type 3 chondrites: MET 00526 (L3.05), MET 00426 (CR3.0), Kainsaz (CO3.2) and Kakangari (K3). Bulk compositions of twenty chondrules in each meteorite were determined with modal recombination analysis. This study provides a self-consistent dataset that combines chondrule textures with mineralogy and bulk chemical compositions. It allows us to make comparisons between different chondrite groups. In order to interpret the compositional relationship between chondrules and matrix, bulk matrix compositions were obtained as well, using EMP defocused beam analyses. In Chapter 1, we compare the mineralogy and bulk chemistry of chondrules and matrix in MET 00526 (L), MET 00426 (CR) and Kainsaz (CO). These three chondrites represent some of the most pristine material that formed in the solar nebula. Chondrule characteristics and the complementary relationship between the compositions of chondrules and matrix suggest open system behavior during chondrule formation, in the form of evaporation and recondensation of volatile and siderophile elements. While chondrules of the same textural types (e.g., FeO-poor (type I) and FeO-rich (type II) porphyritic chondrules) are present in all three chondrites and show similar characteristic features, there are also significant differences between the chondrite groups. This indicates that they probably formed in different regions of the solar nebula. One significant difference can be found in the Fe-Mn systematics of FeO-rich porphyritic olivine (type IIA) chondrules (Chapter 2). We also recognized that Fe-Mn systematics can be used to identify relict grains in type IIA chondrules. Chapter 3 deals with the chondrite Kakangari, which has been thought of as a very pristine chondrite in previous studies. Our study reveals that it records a complex series of events including reduction, thermal metamorphism, sulfidization and low-temperature aqueous alteration. Kakangari chondrules, as they are preserved in the meteorite, are quite different from chondrules in unequilibrated ordinary and carbonaceous chondrites. Kakangari appears to have undergone processing similar to that experienced by the enstatite chondrites.

Name thesis:degree_name

Earth and Planetary Sciences

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Department of Earth and Planetary Sciences

Year

2010

Author dc:creator

• Berlin, Jana

Contributors dc:contributor

• Brearley, Adrian J.
• Jones, Rhian H.
• Sharp, Zachary D.
• Selverstone, Jane
• Grossman, Jeffrey N.

• meteorites
• chondrites
• Kakangari
• bulk chondrule compositions
• modal recombination

Language dc:language

English

Identifier

https://digitalrepository.unm.edu/eps_etds/5

OAI identifier oai:identifier

oai:digitalrepository.unm.edu:eps_etds-1004