Masters Theses

Date of Award

8-2016

Degree Type

Thesis

Degree Name

Master of Science

Major

Geology

Major Professor

Harry Y. McSween Jr.

Committee Members

Lawrence A. Taylor, Christopher M. Fedo

Abstract

A comprehensive petrologic and geochemical characterization of six paired howardites collected from the Dominion Range, Antarctica was conducted. These howardites are megaregolith samples from the asteroid 4 Vesta. Collectively, they contain an assortment of igneous rock fragments that indicate magmatic processes were capable of producing a variety of rock types; 22 chemically and texturally discrete basaltic eucrite, cumulate eucrite, and diogenite lithologies are recognized. The implications for remote-sensing observations of Vesta are discussed. The petrogenesis of two previously unrecognized lithologies are described in further detail: an evolved dacite that we propose is a residual melt from extensive crystallization, and a Mg-rich olivine-orthopyroxene and symplectite assemblage, which we interpret to represent the mantle of Vesta. Evidence suggests that complete melting of Vesta likely did not occur, and that partial melting and serial magmatism dominated the early magmatic history of Vesta. This research supports an evolving view that the differentiation and magmatic activity that occurred on Vesta was extremely complex.

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