Earth and Planetary Sciences ETDs

Author

Jana Berlin

Publication Date

2-9-2010

Abstract

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.

Degree Name

Earth and Planetary Sciences

Level of Degree

Doctoral

Department Name

Department of Earth and Planetary Sciences

First Advisor

Brearley, Adrian J.

First Committee Member (Chair)

Jones, Rhian H.

Second Committee Member

Sharp, Zachary D.

Third Committee Member

Selverstone, Jane

Fourth Committee Member

Grossman, Jeffrey N.

Language

English

Keywords

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

Document Type

Dissertation

CO_Kainsaz-chondrules.xls (19313 kB)
EMP data, images and bulk compositions of chondrules

CR_MET00426-chondrules.xls (21156 kB)
EMP data, images and bulk compositions of chondrules

L_MET00526-chondrules.xls (22797 kB)
EMP data, images and bulk compositions of chondrules

K_Kakangari-chondrules.xls (23925 kB)
EMP data, images and bulk compositions of chondrules

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