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Date of Award

Fall 2025

Document Type

Masters Thesis

Department or Program Affiliation

Geology Department

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Boujibar, Asmaa

Second Advisor

Rice, Melissa S.

Third Advisor

Sas, Mai

Fourth Advisor

Kraft, Michael David

Abstract

Mercury’s high density and large metallic core indicate that it underwent unique accretion and differentiation processes. These conditions influenced the distribution of major and minor elements, resulting in a planet with low FeO contents and distinctive geochemical affinities compared to other terrestrial bodies. Understanding how these conditions affected Mercury’s differentiation provides key insights into the formation of our solar system; and one way to do so is via chondritic meteorites as they are good proxies for planetary building blocks. To evaluate whether Mercury’s bulk composition is chondritic, this study investigated the partitioning of Cr and Ti between metal, silicate, and sulfide phases since Cr and Ti are key elements that are sensitive to redox conditions. I analyzed experiments conducted below the silicate liquidus and combined them with published datasets to refine partition coefficients for Cr and Ti between orthopyroxene, silicate melt, metal, and sulfide phases. These data were incorporated into thermodynamic models to predict their distribution across Mercury’s core, mantle, and crust. The combined experimental and modeling results demonstrate that both Cr and Ti become increasingly siderophile and chalcophile with decreasing oxygen fugacity, while their partitioning between orthopyroxene and silicate melt decreases with increasing pressure and melt composition. Monte Carlo simulations coupled with mass balance calculations indicate that Mercury’s bulk Cr/Al and Ti/Al ratios are consistent with chondritic values if differentiation occurred between IW–4 and IW–3.5. These findings suggest that an impact scenario was not required in Mercury’s history to explain its Cr/Al and Ti/Al ratios. These results emphasize the importance of oxygen fugacity in planetary differentiation and core formation. Mercury provides an important endmember case for understanding how small variations in redox conditions and starting materials can produce the diverse geochemical outcomes observed among terrestrial planets.

Type

Text

Keywords

Mercury, Planetary Science, Experimental Petrology, Planet

Publisher

Western Washington University

OCLC Number

1565076010

Subject – LCSH

Planetary science; Planets--Geology; Petrology; Chromium; Titanium

Geographic Coverage

Mercury (Planet)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

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