Earth and Planetary Sciences ETDs

Publication Date

2-1-2012

Abstract

The chlorine isotope composition of chondrites provides information about isotopic reservoirs that were present in the solar nebula and the effect of secondary processes on the isotopic composition. We analyzed twenty chondrites that included both unaltered (type 3) and altered (types 1-2, 4-6) chondrites from the carbonaceous, ordinary, and enstatite classes. Petrologic type 3 chondrites are the least equilibrated and are those most likely to retain primary nebular signatures. By analyzing unaltered, pristine, chondrites from each class, we can determine if chlorine isotope variations existed among the classes and thus if multiple isotopic reservoirs existed. Since chlorine behaves as a hydrophile and volatile element, analyses of aqueously altered (types 1-2) and metamorphosed (types 4-6) chondrites provide insight into effects of secondary processes on the chlorine isotope composition. Type 3 chondrites have similar δ37Cl values that average -0.3± 0.4°. This value is indistinguishable from the δ37Cl values of the bulk Earth, lowest measured value of the Moon, and the average of martian meteorite samples from the literature. From this similarity, we conclude that the inner regions of the solar nebula had a homogeneous chlorine isotope reservoir. For samples that have undergone secondary processing, we observe slight variations from -2.1 to 1.0° for metamorphosed samples (average -0.3°) and -2.0 to 2.7° for aqueously altered samples (average 0.7°). We conclude that these processes were not significant in fractionating the chlorine isotopes.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Jones, Rhian

Second Committee Member

Brearley, Adrian

Third Committee Member

Shearer, Charles

Language

English

Keywords

chlorine isotope, chondrite, solar nebula

Document Type

Thesis

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