Earth and Planetary Sciences ETDs

Publication Date

Summer 7-15-2021

Abstract

Melting and differentiation are fundamental to early solar system evolution on planetary bodies that accreted enough material to heat up radioactively or through impacts and breach their solidi. Partially and fully melted material is present in the meteorite record in the form of primitive achondrites and achondrites, which are fragments of planetesimals that underwent heating events in the first few million years of solar system history. Although the vast majority of this material is mafic or ultramafic, new evolved samples, recovered in the last few decades, are pushing the petrologic and geochemical boundaries of planetesimal melting, differentiation, and crust formation. The goal of this study is to analyze the composition and interpret the petrogenesis of some of this newly discovered evolved material, which includes deep crustal or mantle cumulates and evolved crustal basaltic andesites and trachyandesites. The formation conditions of these rocks are debated in a terrestrial setting, and on planetesimals their petrogenesis has until now remained mysterious.

Chapter 1 is a study of the petrology and geochemistry of the dunitic monomict fragmental breccias Northwest Africa (NWA) 12217 and 12562. These rocks represent large melting events on a unique parent body that resulted in the formation of deep crustal or mantle cumulates. Chapter 2 focuses on evolved planetesimal crustal material by characterizing NWA 6698, an evolved diorite with a cumulate texture. The oxygen isotopic composition of this rock links it to the ureilite parent body, and the potential for the melting and differentiation of this object is explored. Chapter 3 is a project in experimental petrology in which chondritic bulk compositions are melted under varying temperatures and oxygen fugacities at 1 atmosphere of pressure. This is an attempt to explain the unique evolved compositions of these recent meteorite finds relative to their potentially chondritic precursors. Chapter 4 is a review paper providing a synoptic view of Martian magmatism through geologic time via the study of meteorite chronology.

Degree Name

Earth and Planetary Sciences

Level of Degree

Doctoral

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Carl Agee

Second Committee Member

Charles Shearer

Third Committee Member

Horton Newsom

Fourth Committee Member

Adrian Brearley

Fifth Committee Member

James Day

Language

English

Keywords

Meteorites, Asteroid Belt, Petrology, Geochemistry, Achondrites

Document Type

Dissertation

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