Physical Sciences and Mathematics Commons^™

Revealing The Core Dynamics Of Vesta: Insights From Experimental Investigations Of Electrical Resistivity And Thermal Conductivity, Oluwasanmi A. Orole Mr

Electronic Thesis and Dissertation Repository

Insights from high pressure and temperature experiments involving in-situ measurements of the electrical resistivity of Fe-5wt%Ni at temperatures of up to 2000 K, under pressures of 2-5 GPa in a 1000-ton cubic-anvil press have been used to reveal Vesta’s core dynamics. The Wiedemann–Franz law was used to calculate the thermal conductivity from the measured electrical resistivity data. Comparing the findings of this study with prior investigations on both pure Fe and Fe-10wt%Ni indicates that an increase in Ni ranging from 0-10wt% has negligible effect on the electrical resistivity of Fe alloys. By comparing the range of estimated heat flux through …

Empirical Nonlinear Site Response Applicable To Greater Vancouver, British Columbia, Natalia Gomez Jaramillo

Electronic Thesis and Dissertation Repository

In Greater Vancouver, strong earthquake shaking has not been recorded to quantify expected nonlinear soil response. Earthquake horizontal to vertical spectral ratios (eHVSR) are evaluated at seismic stations located at the edges or deeper center of sedimentary basins in Mexico City, the Kanto basin and Anchorage with available weak-to-strong motion recordings that have similar linear site response to Greater Vancouver to constrain the expected nonlinear soil response for future large earthquakes affecting Greater Vancouver. The empirical results confirm that the very low fundamental frequency (f₀ < 0.6 Hz) at deep Fraser River delta sites will be less affected by strong shakings and suggest that for Fraser River delta edge sites the amplification at the predominant frequency (f₁) could increase up to 1.77 times with a strong event. This thesis’ …

Deformation And Evolution Of Achondrite Parent Bodies, Yaozhu Li

Electronic Thesis and Dissertation Repository

Minerals in planetary bodies record accumulated strain from deformation events such as hypervelocity impacts but potentially also parent body processes such as gravitational compaction. This work investigates olivine microstructural features that may distinguish between different impact levels versus parent body plastic deformation regimes. Achondritic meteorites from the ureilite parent body, the Moon, Mars as well as terrestrial basalt and mantle xenolith have been investigated using micro-XRD, EBSD, micro-XRF and other methods to study their parent body deformation history. A Matlab® method, unit segment length (USL), is herein developed to visualize the crystal boundary geometry and quantify the apparent subboundary density …

Short-Term Versus Long-Term Effects Of Nitrogen Addition And Warming On Ecosystem N Dynamics In A Grass-Dominated Temperate Old Field, Benjamin F. A. Souriol

Electronic Thesis and Dissertation Repository

Increased atmospheric nitrogen (N) deposition and climate warming are both anticipated to influence the ecosystem N dynamics of northern temperate ecosystems substantially over the next century. Nevertheless, in field experiments with N addition and warming treatments, temporal scale can play an important role in determining the extent of treatment effects on N dynamics, and it is unclear to what extent the results of short-term studies can be extrapolated to responses over longer time scales. I compared the short-term versus long-term effects of N addition and warming on net N mineralization, N leaching, and N retention in a grass-dominated old field. …

Thermal And Fluid Evolution Of The Clearwater West Impact-Generated Hydrothermal System, Quebec, And Associated Astrobiological Implications, Daliah R. Bibas

Electronic Thesis and Dissertation Repository

Impact-generated hydrothermal systems result from interactions between a permeable substrate, an impact-generated heat source, and fluids (e.g., H₂O). A comprehensive understanding of the evolution of these terrestrial features has significant implications in the search for habitable environments on Mars, a focus in the emerging field of astrobiology. This thesis presents a detailed case study of the impact-generated hydrothermal alteration of impactites at the Clearwater West impact structure, Quebec, focusing on hydrothermally precipitated quartz vugs in crater-fill impact melt rocks. Sample analysis included optical microscopy, electron microprobe analysis, mass spectrometry, and fluid inclusion microthermometry. Results show 3 main quartz …

Terrestrial Craters As Analogues For Degraded Craters On Titan, Taylor M. Duncan

Electronic Thesis and Dissertation Repository

Besides Earth, Titan is the only planetary body in our Solar System to currently have flowing liquid on its surface. Previous works note that dendritic and rectangular stream networks are present on a global scale on Titan, but do not map networks in the vicinity of Titan’s impact craters: Selk and Sinlap. The objective of this work is to understand how stream networks form adjacent to Titan’s impact craters. This information will inform future missions to Titan (i.e., Dragonfly) about the fluvial morphology of streams near their landing site. I conduct an analogue study with the stream networks at three …

Towards Automated Mineral Identification In Martian Rocks From X-Ray Diffraction Patterns, Luke Tambakis

Electronic Thesis and Dissertation Repository

The CheMin (Chemistry and Mineralogy) instrument on the Curiosity rover has provided a rich set of X-ray diffraction (XRD) patterns from Martian rocks and regolith. These XRD patterns have allowed geologists to make exciting new discoveries about the mineralogy and the geological history of Mars. These discoveries pave the way for further Martian exploration and provide a deeper understanding of Martian geology. The Curiosity rover is very slow by design, travelling at about 4 cm/s. New, faster rovers are being developed to increase scientific throughput and exploration. XRD is valuable for future missions as it can produce new discov- eries …

Petrophysical Properties Of The Hed Meteorites And The Bushveld Igneous Complex: Implications For Future Asteroid Prospecting Missions, Lukas Louwerse

Electronic Thesis and Dissertation Repository

In this work, I make a quantitative and mineralogical comparison of Howardite-EuctriteDiogenite (HED) meteorites with terrestrial samples from the Bushveld Igneous Complex (BIC) to assess how geophysical surveys of 4 Vesta or of V-type asteroids could detect BIClike ore deposits. Petrophysical methods in this work include bulk and grain density, derived porosity (using helium pycnometry, the Archimedean method, and X-ray micro-computed tomography), magnetic susceptibility, induced polarization and resistivity, and P-wave velocity. Mineralogical methods in this work include optical microscopy, micro X-ray diffraction, micro X-ray fluorescence element mapping, and electron beam methods. Howardite NWA 15199 was classified as part of this …

Topographic Effects Of Shallow Crustal Earthquakes In The Greater Vancouver Region, Alex Vanderhoeff

Electronic Thesis and Dissertation Repository

Vancouver has a high seismic risk due to the proximity of the city to the Cascadia subduction zone offshore, the soft sediments the metropolitan region overlies, and the mountainous topography nearby. The soft sediments and mountainous topography could cause an increase in shaking due to the sedimentary basin, topographic resonance and constructive/destructive interference, respectively. Numerical three-dimensional (3D) wave propagation simulations (WPS) were run using a finite difference scheme developed by Peterson and Sjogreen (2012), Seismic Waves, 4^th order, to perform simulations of large shallow crustal rupture scenario earthquakes using the 1994 M6.7 Northridge, California earthquake slip distribution. The …

Late Neoarchean To Middle Paleoproterozoic Geology Of Devon And Ellesmere Islands, Canadian Arctic, Joshua P. Laughton

Electronic Thesis and Dissertation Repository

The northernmost exposure of the Laurentian shield in Canada outcrops on Devon and Ellesmere islands within the Canadian Arctic Archipelago. Due to the remote location, the basement rocks of these islands have received little attention. From this study, zircon crystallization ages demonstrate that Devon Island is underlain by a late Neoarchean terrane comprising orthogneisses emplaced at ca. 2.55–2.51 Ga and an interleaved metasedimentary sequence deposited at ca. ≥2.47 Ga. On northern Devon Island, younger metasedimentary sequence(s) were deposited at ca. 2.2–1.9 Ga and intruded by ca. 2.01–1.95 Ga granitoids. Devon and Ellesmere islands experienced widespread metamorphic activity associated with the …

The Fate Of Carbonate Rocks During Hypervelocity Impacts: Case Studies From Three Impact Structures On Earth, Nicolas D. Garroni

Electronic Thesis and Dissertation Repository

Approximately 28% of all hypervelocity impact structures discovered on Earth exist in a carbonate-dominated target sequence. Despite decades of research, how carbonate rocks and minerals react to shock metamorphism is still poorly understood. In this contribution, three impact structures on Earth were studied to determine the effects of shock metamorphism on carbonate minerals: Chicxulub, Crooked Creek and Jebel Waqf as Suwwan.

At Chicxulub, carbonates from the impact-melt bearing breccia of drill core, M0077A were characterized petrographically and geochemically. Calcite was the only carbonate mineral present and is abundant throughout the impact breccia in five distinct varieties: limestone clasts …

Soil Organic Carbon Dynamics And The Effects Of Resident Vegetation In Pelee Island Soils, Colton Geil

Electronic Thesis and Dissertation Repository

Soil organic carbon (SOC) enhances nutrient retention, structural stability, porosity, aeration, water infiltration, and overall soil health. Understanding SOC turnover and its preservation in soils is paramount to managing carbon sequestration. On Pelee Island, we used δ¹³C, δ¹⁵N and C/N of SOC at various depths to identify the sources and evolution of SOC with time. At depths >150 cm, SOM was from a mixture of aquatic and terrestrially derived sources. We also analyzed the impact of permanent cover crops called ‘resident vegetation’ on the ability of soils to store carbon in different aggregate size fractions. SOC …