Physical Sciences and Mathematics Commons^™

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 …

Lunar Regolith Simulant Behaviours Affected By Shock Metamorphism And Mineralogy, Xiao Chen Zhang

Electronic Thesis and Dissertation Repository

There are still many gaps in improving the fidelity of lunar regolith simulants to simulate more properties. This study compares some fundamental physical and mineralogical properties of three types of lunar highland regolith simulants: LHS-1, a commercial product with high mineralogical fidelity; UWO-1G, an original simulant that is the main component of LHS-1; and UWO-1S, another original product that is attempted to produce shocked grains in lunar simulants from pulverizing and mixing impact rocks sourced from the Mistastin Crater.

Preliminary results indicated that even though all simulants are composed of mostly plagioclase minerals and have similar particle size distribution patterns, …

Investigation Of Shocked Basalts From Vargeão Dome And Vista Alegre: Implications For The Search For Life On Mars, Nikol Posnov

Electronic Thesis and Dissertation Repository

Impact craters represent excellent astrobiological targets for planetary exploration missions to Mars. The impact of an asteroid or comet into a crystalline, H₂O-bearing target may result in development of a hydrothermal system and increase the habitability of the substrate for the colonization of endolithic microorganisms. Given that Mars’ surface is covered by cratered basaltic rock, this study investigated target rocks and impact breccias from Vargeão Dome and Vista Alegre impact structures that formed in basalt in the Paraná Basin of Brazil.

Utilizing petrography and micro-X-ray diffraction (μXRD), the degree of shock metamorphism in plagioclase was quantitively determined. Measuring …

Raman Spectroscopy And Synchrotron X-Ray Diffraction Study Of Lunar And Terrestrial Plagioclase Feldspar At High-Pressure And High-Temperature Conditions, Tianqi Xie

Electronic Thesis and Dissertation Repository

Plagioclase feldspar is one of the abundant minerals on the surface of the Earth, the Moon and Mars, and is also commonly found in meteorites. This dissertation seeks to better understand the phase changes in plagioclase when subjected to meteorite impact and fundamental information about impact cratering process.

Shock features in plagioclase from Mistastin Lake impact structure, Canada, and Apollo samples returned from the Moon were investigated. A series of progressive optical shock features were observed, and their Raman spectra was collected systematically. Identified shock featurs include deformed twins, planar features, and partially to completely isotropic or diaplectic glass. However, …

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 …

Ureilite Meteorite Record Of Shock Metamorphism And Parent Body Processes, Yaozhu Li

Electronic Thesis and Dissertation Repository

Ureilites are an abundant non-chondritic meteorite class that are petrographically similar to terrestrial ultramafic rocks, consisting mostly of coarse-grained olivine and pyroxene, with remarkably low occurrence of plagioclase feldspar. This work examines a suite of ureilites (six monomict ureilites and one polymict ureilite), primarily focusing on the mineral olivine as a recorder of shock damage. Optical petrography and Raman spectroscopy provide context information, and in-situmicro-X-ray diffraction (𝜇XRD) is used to obtain quantitative measurements of diffraction peak Full-Width-Half Maxima upon integration along the chi direction on 2D XRD patterns. Ureilites show an increasing streak length of FWHMχ and asterism (discrete …

Microstructural Geochronology Of Zircon Across The Central Uplift Of The Vredefort Impact Structure, South Africa, Connor Lawrence Davis

Electronic Thesis and Dissertation Repository

The Vredefort central uplift, or ‘dome,’ represents the erosional remnant of one of the largest (~300 km diameter) and oldest (~2.020 Ga) terrestrial impact structures. This investigation was performed to help elucidate the complexity of the shock process on zircon, incorporating various electron beam methods, including BSE and SE imaging, EBSD, CL, and EDS (mapping and semi-quantitative compositional analysis). A new shock microstructural progression in terrestrial zircon is suggested, as well as a complete structure-wide analysis of impact melt inclusions in zircon. Regional trends in the effects of shock on zircon are included. Impact melt glass inclusion compositions vary widely, …

Shock Metamorphic Effects In Lunar And Terrestrial Plagioclase Feldspar Investigated By Optical Petrography And Micro-X-Ray Diffraction, Annemarie E. Pickersgill

Electronic Thesis and Dissertation Repository

Shock metamorphism, caused by hypervelocity impact, is a poorly understood process in feldspar. This thesis addresses: a) developing a quantitative scale of shock deformation in plagioclase feldspar; b) expanding the utility of plagioclase feldspar for determining shock level; and c) micro-X-ray diffraction as a technique with which to study shock in feldspar.

Andesine and labradorite from the Mistastin Lake impact structure, Labrador, Canada, and anorthite from Earth’s moon, returned during the Apollo program, show shock effects such as diaplectic glass. Planar deformation features are absent in plagioclase, but abundant in terrestrial quartz. A pseudomorphous zeolite phase (levyne-Ca) was identified as …