Date of Award

Winter 2008

Project Type

Thesis

Program or Major

Earth Sciences: Geology

Degree Name

Master of Science

First Advisor

Julia G Bryce

Abstract

Compositions of mafic lavas from the Turkana region, within the East African Rift System (EARS), provide valuable contributions to the understanding of the significant processes in continental magmatism. Specifically, new Hf isotopic ratios coupled with new and existing Pb, Sr, Nd, and He isotopic compositions of Quaternary and Tertiary lavas from Turkana reveal compositional contributions from melt generation processes occurring in the sublithospheric mantle versus contributions from melt generation processes in the lithosphere. Pb and Nd compositions demonstrate two separate mixing trends within the Turkana lavas, and together with Sr isotopic compositions, three compositional end-members are revealed: C-Component, EM1, and HIMU. New Hf isotope ratios of the Quaternary and Tertiary Turkana samples presented a temporal correlation, in Hf-Pb space one trend progresses from an EM1-like component to a C-component over time, while the other trend progresses from a HIMU like component to an EM1 like component throughout time. Based on compositional and spatiotemporal relationships, a model is proposed where HIMU is a lithospheric component, EM1 is a sublithospheric component that acts as an agent of metasomatism in the lithosphere, and the C-component is a second sublithospheric end-member likely present as a result of regional plume activity.

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