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This study addresses the origin of the combined He-Ne-Ar-Xe noble gas isotopic variation in mantle derived oceanic basalts. High precision heavy noble gas compositions of basalts from the Rochambeau Rift along the Northwestern Lau Basin, the Gakkel Ridge, the Southeast Indian Ridge and the South Atlantic Ridge presented here confirms fundamental differences between the volatile constituents of the depleted mid-ocean ridge basalt (MORB) source and plume sources. We find that the depleted MORB mantle is characterized by systematically lower proportions of Pu-fission derived Xe than the Iceland plume and the Samoan-like plume sampled at the Rochambeau Rift. These two plume sources are associated with low radiogenic \(^{129}Xe/^{130}Xe\) ratios that are not attributable to recycled atmosphere and must sample ancient (4.45 Ga) volatile rich mantle reservoir that experienced a lower degree of mantle processing than the depleted MORB source. I report \(^{128}Xe/^{130}Xe\) ratios in excess with respect to the atmosphere in deeply erupting Gakkel lavas, similar to mantle derived volatiles in natural gas samples. Deconvolution of fission derived xenon isotopes indicate that natural gas samples and the Gakkel MORBs are derived from the same volatile depleted mantle reservoir. The radiogenic He isotopic composition, the low estimated ratio of Pu to U derived xenon isotopes, and the low \(^{129}Xe/^{130}Xe_E\) ratio found in the source of the West Volcanic Zone (WVZ) along the Gakkel Ridge indicates the presence of increased amounts of recycled atmospheric volatiles. I suggest that the low \(^{129}Xe/^{130}Xe\) ratio beneath the WVZ cannot be explained by sampling an ancient (>4.45 Ga) lithospheric mantle component that evolved in isolation from convection throughout Earth's history. Instead, the Xe isotopic composition may be consistent with the presence of subduction derived metasomatizing fluids with atmospheric heavy noble gases trapped in the sub-continental lithospheric mantle sampled along the ridge. Available Ne isotope MORB data and new high precision Ne data presented in this study (including basalts from the East Pacific Rise, the Galapagos Spreading Center, and the Juan de Fuca Ridge) allows me to construct a combined He-Ne isotope distribution and infer first order source mixing systematics in the upper mantle., Earth and Planetary Sciences

The volatile inventories of the Earth and Moon reflect unique histories of volatile acquisition and loss in the early Solar System. The terrestrial volatile inventory was established after the giant impact phase of accretion, and the planet subsequently settled into a regime of long-term volatile exchange between the mantle and surface reservoirs in association with plate tectonics. Therefore, volatiles in the Earth and Moon shed light on a diverse array of processes that shaped planetary bodies in the Solar System as they evolved to their present-day states., Earth and Planetary Sciences

The history of planet formation and evolution is strongly tied to understanding the outcomes of a wide range of impact events, from slow accretionary events to hypervelocity events that melt and vaporize large fractions of the colliding bodies. To better understand impact processes, their effects on planetary evolution, and how to interpret geochemical data, we need to improve our knowledge of the behavior of materials over the entire range of conditions accessed by collisions. Here I present experimental results from gas gun, laser driven, and pulsed power facilities. Together these facilities can access the tremendously wide range of pressure and temperature conditions achieved in natural impact events. This work focuses on the thermodynamics of impacts to better understand the phase transitions that most strongly affect the dynamics and chemical consequences of a collision. I show that the entropy generation during collisions is the most natural means of interpreting the thermodynamic processes that occur during an impact event. For materials with sufficient thermodynamic data at high pressures and temperatures, I present a method for obtaining the entropy generation during an impact. With the knowledge of the entropy, I present new shock-and-release techniques to investigate the liquid-vapor region of the phase diagram. I also show that for materials without sufficient data to calculate the entropy generation during an impact, one can use the shock-and-release techniques described here to determine the entropy in the high pressure shock state. With better equation of state models that are constrained by our experimental data, our confidence in impact models improves dramatically. Using a high fidelity equation of state for \(H_2O\). ice, I derive scaling laws for how much \(H_2O\) ice melts and vaporizes for impacts onto icy bodies. Recognizing that icy bodies are not pure ice, I have performed experiments to show how the impact energy partitions between the disparate phases. Finally, I discuss some of the uncertainties in using the laboratory experiments to directly interpret the effects of impacts in nature., Earth and Planetary Sciences

The Helium isotopic system provides novel tools to probe the sedimentary record of the earth over the last few hundred million years. Radiogeneically derived \(^4He\) and solar wind implanted \(^3He\) is delivered to sediments by weathered continental material and interplanetary dust particles, respectively. The purpose of research presented in this thesis is to use \(^4He\) of terrestrial and \(^3He\) of extraterrestrial origins as tools to investigate the relationship between global climate and surface processes on earth. I measured \(^4He\) in annual growth bands in a Porites coral from the northern Red sea, lacustrine carbonate sediments from the Bahamas and marine sediments in the North Atlantic (Ocean Drilling Program site 1313). Terrestrially derived fraction of the measured \(^4He\) in the Red Sea Porites coral and carbonates of the Bahamas together provide accurate information about changes in dust export rates from North Africa over the last millennium; dust fluxes are intimately tied to droughts in North Africa at decadal to centennial time scales over the last millennium that in turn, appears to be modulated by sea surface temperatures (SSTs) in the Indian and the Atlantic Ocean. On the other hand, \(^4He\) content in marine sediments in the North Atlantic provide information about changes in sources of detrital over the last six million years that in turn appears to reflect changes in ocean circulation in the sub-polar north Atlantic. Accretion rates of solar wind implanted \(^3He\) provide independent constraints on time distribution and physical processes operational during the deposition of marine sedimentary sequences. I measured extraterrestrial \(^3He\) in sediments from the late Cretaceous through the early Danian at one site in the North Pacific (Ocean Drilling Program site 1209 on the Shatsky Rise) and in three sites from the South Atlantic (Deep Sea Drilling Projects sites 516F on Rio De Grande Rise and 528 on the Walvis Ridge). The high-resolution record of extraterrestrial \(^3He\) at the Shatsky Rise demonstrates that there was no increase in solar system dustiness associated with the meteorite impact thought to be responsible for the end cretaceous mass extinction. The assumption of constant delivery of extraterrestrial material therefore resulted in independent constraints on sediment accumulation rates and resultant age model through the early Danian, the latter marking the recovery of ocean system following the events of the end Cretaceous mass extinction. On the other hand, the extraterrestrial \(^3He\) derived mass accumulation rates in the south Atlantic sites demonstrate that carbonate-clay cyclicity in sediments—used by cyclostratigraphy to derive age models—are generated by different physical processes at different sites. It is therefore, crucial to understand processes underlying the carbonate-clay cyclicity before interpreting sediment couplets in terms of age model., East Asian Languages and Civilizations