Award Date

8-1-2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geoscience

First Committee Member

Arya Udry

Second Committee Member

Shichun Huang

Third Committee Member

Elisabeth Hausrath

Fourth Committee Member

Andrew Martin

Fifth Committee Member

Aude Picard

Number of Pages

209

Abstract

The ancient Mars crust can yield insights into planet formation and evolution that Earth cannot. Direct investigation of the martian surface is limited to studies on meteorites and rover-obtained analyses. The nakhlites and chassignites, two classes of martian meteorites, are together the largest suite of martian meteorites derived from a single location on the surface. As such, they present a rare opportunity to study the Mars crust in detail using samples bearing a contextual relationship. Rover studies have found a surprising amount of compositional diversity in surface materials, the formation mechanisms of which are not well-constrained. This dissertation leverages meteorites and rover analyses in order to better understand what magmatic processes contributed to the formation and compositional diversification of the martian crust.

In Chapter 1, I conducted thermodynamic modeling to model a magmatic process known as assimilation and fractional crystallization, wherein minerals are removed from the magma as they form (fractional crystallization) and the crust surrounding the magma chamber is incrementally melted and added to the bulk magma (assimilation). I found that assimilation and fractional crystallization may have contributed to early evolution of the Mars crust.

In Chapter 2, I studied melt inclusions in a representative suite of martian nakhlite and chassignite meteorites. Melt inclusions are pockets of magma entrapped in minerals as they form, and can represent an initial magmatic composition if they are entrapped early and remain unaltered. I found that nakhlite and chassignite melt inclusions record evidence of crystal storage in changing magma compositions.

In Chapter 3, I analyzed elemental patterns (called “zoning”) in nakhlite and chassignite minerals. Zoning of elements in a mineral record formation conditions such as changes in temperature and composition of the magma. I found that minerals in the nakhlites and chassignites formed initially very rapidly, and that minerals were stored in changing magma compositions, adding to a growing body of evidence that such formation conditions are very common on Mars.

In this dissertation, I apply a variety of modeling and analytical methods to both samples and to rover analyses in order to study the formation and evolution of the Mars crust. I demonstrate that magmatic processes common on Earth (such as assimilation and fractional crystallization, magma mixing, and crystal storage) evidently contribute to the compositional diversity of the martian crust as well.

Keywords

assimilation; chassignite; igneous petrology; melt inclusion; meteorites; nakhlite

Disciplines

Astrophysics and Astronomy | Geochemistry | Geology

File Format

pdf

File Size

31160 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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