Date of Award
8-1-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Elemental partitioning and crystallization processes on the Earth, Moon, and the meteorite Erg Chech 002 parent body are explored in this thesis, highlighting different mineral assemblage crystallization histories in three distinct geologic environments: the Earth's crust, the Moon's mantle, and the Erg Chech 002 (EC 002) parent body. Multiple series of one-atmosphere zircon synthesizing experiments, using basaltic andesite, andesite, and rhyolite starting materials, have been conducted (Chapter 2) to study the U/Th partitioning behavior between zircon and melt. The results reveal that sector zoning, fractional crystallization, typical igneous oxygen fugacities, and melt composition, particularly the whole rock silica content and NBO/T, do not significantly influence the partitioning of U and Th between zircon and melt. However, these experiments, combined with the compiled natural zircon and experimental datasets, demonstrate that zircon crystallization temperature is the primary control on U/Th partitioning. Consequently, the calibrated equation derived from these findings can be directly applied to the 230Th correction to improve accuracy in age-corrected determinations once the zircon crystallization temperature is known. Chapter 3 is a kinetic reduction experimental study on a natural terrestrial ilmenite megacryst as an analog for lunar ilmenite material to test the hypothesis that subsolidus reduction of ilmenite can enhance metallic FeNi contents within the lunar crust when it occurs in or near cooled mafic intrusive bodies. The experimental results demonstrate that slow cooling and subsolidus reduction of lunar magmatic intrusive bodies is a possible mechanism for producing intense lunar crustal magnetism. The experimental results also show that the ilmenite reduction reaction is a diffusion-controlled reaction; thus, it is dependent on temperature, initial ilmenite grain sizes, and ƒO2. Specifically, reduction within hypabyssal dikes with high-Ti or low-Ti mare basalt compositions can produce sufficient FeNi grains to carry the minimum >0.5 A/m magnetization intensity inferred for swirls, especially if ambient fields are >10 μT or if fine-grained Fe-Ni metals in the pseudo-single domain grain size range are formed. Due to their higher ilmenite content, reduction of high-Ti mare basalts can more easily produce >0.5 A/m magnetizations than reduction of low-Ti mare basalts. Chapter 4 is an experimental study using the bulk composition of EC 002 as the starting material to study the mineral crystallization history of EC 002. Experimental results show that synthetic mineralogy is consistent with observed mineralogy, confirming its lithologic origin as a primitive melt. This chapter aims to provide a comprehensive understanding of the petrology of EC 002 using estimated bulk and mineral composition, specifically focusing on its relationship to a protoplanetary mantle and potentially primary cumulates of a magma ocean. This chapter also provides scientific estimations on the parent body size of EC 002.
Language
English (en)
Chair and Committee
Michael Krawczynski
Committee Members
Bradley Jolliff; Douglas Wiens; Kun Wang; Sonia Tikoo
Recommended Citation
Liang, Yuanyuan, "Experimental Investigations of Elemental and Isotopic Partitioning with Applications to Geochronology, Lunar Crust, and Meteorite Erg Chech 002" (2024). Arts & Sciences Electronic Theses and Dissertations. 3307.
https://openscholarship.wustl.edu/art_sci_etds/3307