Experimental Constraints on the geochemical processing planetary interiors: Noble gases and spinel spectroscopy

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Overview

Title
Experimental Constraints on the geochemical processing planetary interiors: Noble gases and spinel spectroscopy
Contributors
Jackson, Colin (creator)
Parman, Stephen (Director)
Cooper, Reid (Reader)
Saal, Alberto (Reader)
Mukhopadhyay, Sujoy (Reader)
Parmentier, Marc (Reader)
Brown University. Geological Sciences (sponsor)
Doi
10.7301/Z0CJ8BVC
Copyright Date
2015
Abstract
The first three chapters of this thesis are focused on experimental determinations of noble gas solubility in a variety of materials relevant to partial melting of the mantle and subduction. Combined, these chapters represent an experimental exploration of the deep noble gas cycle. In the first chapter, we show that helium, neon, and argon are strongly incompatible in upper mantle minerals. Further, we demonstrate that helium solubility in olivine is insensitive to changes in common point defect concentrations, suggesting helium is primarily incorporated onto interstitial sites. Application of helium solubility data to mantle melting models indicates that melting residues will have decreased He/(U+Th), and, with time, radiogenic helium isotopic signatures. The second two chapters focus on the mineralogic controls on noble gas recycling. Specifically, we quantify noble gas solubility in a wide range of minerals with lattice ring structures. We show that minerals with ring structures have a strong, but variable, affinity for helium, and thus, may facilitate recycling of noble gases. We further show that ring structure minerals tend to favor smaller radii noble gases. The final chapter is focused on determining the factors that control visible to near-infrared reflectance spectra of iron-bearing aluminate spinels. This chapter is motivated by the recent remote sensing detections of spinel-rich deposits on the Moon and seeks to provide additional geologic context for these spinels. To this end, we synthesized a series of spinels with variable amounts of iron under lunar-like redox conditions. By controlling point defect chemistry, we demonstrate that absorption bands near ~1000 nm in spinel are particularly sensitive to the abundance octahedral, ferrous iron, which is primarily controlled by cooling rate in natural systems. Accounting for geologic cooling rates, we conclude that 1) the spinels associated with central peaks and basin walls are very magnesian (~6 wt. % FeOt) and 2) the pyroclastic spinels associated with Sinus Aestuum either are ferric iron-rich or cooled very rapidly, possibly in the absence of an extensive vapor cloud.
Keywords
noble gases
Gases, Rare
Geochemistry
Spinel
Notes
Thesis (Ph.D. -- Brown University (2015)
Extent
13, 301 p.

Citation

Jackson, Colin, "Experimental Constraints on the geochemical processing planetary interiors: Noble gases and spinel spectroscopy" (2015). Earth, Environmental and Planetary Sciences Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0CJ8BVC

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