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Title: Chromium stable isotope variations in the early solar system and deep Earth
Author: Jerram, Matthew
ISNI:       0000 0004 8503 3142
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2019
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This study uses high precision chromium (Cr) isotope measurements to provide insights into the composition of the mantle, and constraints on the material from which Earth accreted. This involved achieving a deeper understanding of Cr isotope fractionation, facilitating the determination of a more precise δ53Cr for the bulk silicate Earth (BSE). This in turn leads to a comparison with different classes of chondrites as representatives of distinct types of disk material. The δ53Cr composition of the mantle is unaffected by partial melting, but is perturbed by different metasomatic processes, which has created a δ53Cr heterogeneous mantle. An accurate δ53Cr BSE value cannot be acquired using mantle peridotites due to the widespread metasomatic variations they record. An alternative method to calculate the δ53Cr BSE composition is to use komatiites, as they sample a large volume of the mantle. The δ53Cr of komatiites varies during fractional crystallisation, which must be considered when calculating the initial composition. Different methods were used to determine the initial composition of the komatiite liquid. A weighted average is best able to account for the variations to the δ53Cr during crystallisation, and produces a well-constrained BSE composition, -0.12 ± 0.03 ‰. Enstatite chondrites are meteorites that may have made up a significant proportion of the material that formed the Earth. The δ53Cr isotopic composition of the enstatite chondrites are within error of the BSE, with the closest match provided by EH chondrites.
Supervisor: Halliday, Alex ; Bonnand, Pierre Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available