Physical Sciences and Mathematics Commons^™

Quantification Of Surface Roughness Of Lava Flows On Mars, Carolina Rodriguez Sanchez-Vahamonde

Electronic Thesis and Dissertation Repository

Volcanism has played a significant role throughout Mars’ geologic history. Extensive lava flows are widely spread across Mars’ equatorial region, shaping the surface in a very distinct way. In radar images (at the decimeter scale), these flows are bright, which is a typical characteristic of extremely rough, blocky lavas flows seen on Earth. Although the source of the extreme roughness of Martian lava flows is unknown, their surface roughness parameters can be constrained to 1) gain information about Mars’ interior processes, 2) find appropriate analogues on other planetary bodies, and 3) ideally infer the emplacement style of such lavas. Here, …

Numerical Simulations Of Complex Crater Formation In Layered And Mixed Targets, Ryan Hopkins

Electronic Thesis and Dissertation Repository

Numerical simulations of hypervelocity impact events provide a unique method of analyzing the mechanics that govern impact crater formation. This thesis describes modifications that were made to the impact Simplified Arbitrary Lagrangian Eulerian (iSALE) shock-physics code in order to more accurately simulate meteorite impacts into layered target sequences and details several applications that were investigated using this improved strength model.

Meteorite impacts occur frequently in layered targets but resolving thin layers in the target sequence is computationally expensive and therefore not often considered in numerical simulations. To address this limitation iSALE was modified to include an anisotropic yield criterion and …

Shock Effects Recorded By The U-Pb Radiometric System In Zircons Of Apollo 17 Impact Breccias And By Raman Spectroscopy In Enstatite Meteorites, Bidong Zhang

Electronic Thesis and Dissertation Repository

Impact cratering processes and formations are ubiquitous on the rocky planets within the Solar System. The Earth-Moon system was formed by a massive planetary impact, and numerous impacts afterwards significantly reshaped the topography and lithology of the Moon surface. This dissertation focuses on studying some specific geochemical, geochronological, and geophysical signatures of impact processes preserved in lunar rocks and asteroidal meteorites.

The zircon U-Pb radiometric system is one of the most reliable geochronometers in measuring geological time. Recently, unsupported radiogenic Pb enrichment has been reported to compromise the accuracy and precision of zircon U-Pb geochronometer in terrestrial rocks. In Chapter …

Ni And Fe Isotope Fractionation During Weathering And The Formation Of Ni Laterite Ore Deposits In The Philippines, Congxi Zhu

Electronic Thesis and Dissertation Repository

Weathering processes on Ni-rich ultramafic rocks in tropical areas produce laterites that become exploitable for Ni mining. To better understand these processes, samples were collected stratigraphically with water samples from several Ni mines in the Philippines and studied for Ni and Fe isotope compositions. This study found that Ni isotope fractionation takes place during the formation of Ni-enriched minerals (goethite), when light Ni isotopes are preferentially incorporated into new minerals formed, leaving heavy Ni isotopes in groundwater. The Δ⁶⁰Ni_{Limonite-Bedrock} is up to -0.19 ± 0.32‰. Even though Fe is partitioned with redox state change during these reactions, …

Creating Calibration Curves Using In Situ X-Ray Diffraction To Determine The Shock Pressure Experienced By Clinopyroxene, Laura Jenkins

Electronic Thesis and Dissertation Repository

This work extends on two quantitative methods for evaluating shock metamorphism to include clinopyroxene using X-ray diffraction (XRD). Clinopyroxene samples experimentally shocked to known shock pressures were studied with XRD. Lattice strain (ε) and strain-related mosaicity (SRM) were measured for each sample and plotted against their known shock pressures, creating a ε versus shock pressure calibration curve and an SRM versus shock pressure calibration curve. These calibration curves were applied to three meteorites: Nakhla, Zagami, and ALHA 77005. The SRM calibration curve gave peak shock pressures of 12±8 GPa for Nakhla, 44±8 GPa for Zagami, and 68±8 GPa for ALHA …

Calcium Isotopes In The Saint Agatha Kettle Lake Deposits Of Southern Ontario, Emma-Dawn Ferguson

Electronic Thesis and Dissertation Repository

The St. Agatha kettle lake deposits, ON, Canada, contain a thick section of endogenic marl and coeval shelly fauna. Marl accumulation occurred from ~13,500 to ~8,200 cal yrs BP. This study examines controls on marl and shell δ^44/42Ca, element ratios (Mg, Fe, and Ba), δ¹⁸O, δ¹³C, and ⁸⁷Sr/⁸⁶Sr ratios of marl calcite, shell aragonite, groundwater, and bedrock as proxies for paleolacustrine conditions. Results for Interval A (532.0 to 475.0cm) indicates a cooler, wetter climate, lower primary lake productivity and higher lake levels. Interval B (475.0 to 345.0cm) marks the onset of …

Evaluating Zircon Strain Chronometry Of A Grenville Front Deformation Fabric Through Microstructural Analysis And Quartz Piezometry, Kaitlyn Petkau

Electronic Thesis and Dissertation Repository

Zircon strain chronometry can allow correlation of isotopic ages with microstructural fabrics to place an absolute age on the timing of deformation. However, the general applicability of zircon strain chronometry to problems in regional continental tectonics is still being tested and this study is the first effort to apply the approach to the ~1 Ga (billion year old) Grenville Province of the Precambrian Canadian Shield. Samples were analyzed from the 1747 +6/-5 Ma Wanapitei Complex, a poly-deformed mafic metaplutonic body that preserves fabric evidence for several stages in the tectonic history of the Grenville Front. This study is the first …

Impact Cratering Processes On The Earth And Moon: Meteorites, Complex Craters, And The Origin Of The Moon, Patrick Hill

Electronic Thesis and Dissertation Repository

This thesis seeks to understand the mechanism of hypervelocity impacts, lunar origin and geology, and stable isotope techniques and its application to lunar material. Three lunar regolith breccias, Dhofar 1673, Dhofar 1983, and Dhofar 1984, were examined. The petrography, mineralogy, isotope chemistry, and bulk chemistry of these meteorites were quantified to investigate their origin. The chemistry of the impact melt rock and bulk chemical analysis suggests sourcing from either the Feldspathic or Outer Feldspathic Highland Terranes. Given the similarities in the meteorites, and the proximal location of each find (within 500 m), this thesis proposes strong evidence for their pairing. …

Characteristics Of Impactites In The Central Uplift Of The Mistastin Lake Impact Structure, Canada, Alaura Singleton

Electronic Thesis and Dissertation Repository

This thesis investigated the nature of parautochthonous and allochthonous impactites found in the erosional remnant of the central uplift of the Mistastin Lake impact structure, central Labrador. This was carried out with the goal of discovering details about the composition and formation conditions of these complex materials. This study involved fieldwork and a range of laboratory techniques. As part of this work, a geological map of Horseshoe Island has been created, and is the most detailed to date. The shock metamorphic features found in the uplifted target rocks have been assessed, and indicate a peak shock level of 5a (35-45 …

The Impact-Generated Hydrothermal System Of The East Clearwater Lake Impact Structure, Quebec, Canada, Derek King

Electronic Thesis and Dissertation Repository

Alteration mineralization at impact craters gives insight into the hydrothermal system generated post-impact. This is the first work to document the alteration mineralization to characterize the East Clearwater impact-generated hydrothermal system. The East Clearwater hydrothermal system in the impact melt rocks and melt-bearing breccias transitions from zeolite-smectite assemblages to chlorite-dominant assemblages with depth. pH evolution of the East Clearwater impact-generated hydrothermal system reflects magmatic-driven hydrothermal systems in granitic rocks. West Clearwater has a different alteration style. Given an impact forms a hydrothermal system, the style of alteration will not only vary dependent on target lithologies (i.e., crystalline, sedimentary, mixed target), …