The main objectives of this study are to determine how various physical and chemical properties of geologic samples can be investigated by Fourier Transform InfraRed (FTIR) spectral analyses, and determine how each of these individual properties uniquely alter the mid-infrared spectrum. Of particular interest is how extraterrestrial samples differ (spectrally) from terrestrial samples, and how such findings can be applied to current and future missions to airless planetary bodies (such as Diviner Lunar Radiometer, aboard the Lunar Reconnaissance Orbiter, and the Mercury Thermal Radiometer on BepiColombo). As such, a range of geological samples have been analysed including terrestrial rocks (anorthosite, granite, grabbro etc.), mineral standards (common rock-forming minerals), lunar meteorites (from Miller Range, Antarctica), and Apollo 14, 15, and 16 soils. A new technique to analyse such samples has been developed and implemented as part of this study: FTIR spectral imaging of unconsolidated samples (powders and soils) to obtain modal mineralogy estimates. Such estimates are comparable to QEMSCAN analyses and spot point counting of the same samples. This is particularly relevant for the non-destructive analysis of Apollo soil samples (bulk and sieved fractions). Individual spectra of polished terrestrial and extraterrestrial samples have been obtained in preparation for the creation of a spectral database. Such samples also have coupled chemical composition information via Electron Probe MicroAnalysis (EPMA). To have a spectrum and an associated chemical composition for each mineral in a database is unique compared to other spectral databases. Analyses of lunar meteorites resulted in an understanding of how shock (caused by hypervelocity impacts) alters the physical and spectral properties of lunar minerals. FTIR microscopy of individual minerals and phases in the meteorites were coupled with optical and cathodoluminescence (CL) imaging to identify the level of shock obtained by each mineral and phase. The FTIR reflectance bands of plagioclase merge with increasing shock pressure until a single, low-reflectance broad peak is displayed by the most highly shocked plagioclase (>45 GPa), and a dark-red colour is present in CL images. FTIR and QEMSCAN analyses of Apollo regolith samples have provided an understanding of the spectral effects of bulk mineralogy, maturity (a measure of the time spent at the lunar surface), grain size, and mineral chemistry. Using such information, the modal mineralogy of each sample has been estimated, one of which had not previously been analysed for its modal mineralogy. Samples from the same Apollo missions present similar spectral features, meaning FTIR spectroscopy can be used to identify the origin of lunar soils. A weak correlation in maturity with a spectral feature termed the Christiansen Feature has been found for lunar samples. Related to maturity, FTIR spectra of individual agglutinates (a product of space weathering) have been obtained and the spectral properties of agglutinates (decreased %Reflectance values of the region sensitive to geological materials) resemble those of highly mature lunar soils.

abstract: Shock metamorphism in meteorites constrains the impact histories of asteroids and planets. Shock-induced high-pressure (HP) minerals can provide more precise estimates of shock conditions than shock-induced deformation effects. In this research, I use shock features, particularly HP minerals, in ordinary-chondrite samples to constrain not only shock pressures but also the pressure-temperature-time (P-T-t) paths they experienced. Highly shocked L5/6 chondrites Acfer 040, Mbale, NWA 091 and Chico and LL6 chondrite NWA 757 were used to investigate a variety of shock pressures and post-shock annealing histories. NWA 757 is the only highly shocked LL chondrite that includes abundant HP minerals. The assemblage of ringwoodite and majoritic garnet indicates an equilibration shock pressure of ~20 GPa, similar to many strongly shocked L chondrites. Acfer 040 is one of the only two chondrite samples with bridgmanite (silicate perovskite), suggesting equilibration pressure >25 GPa. The bridgmanite, which is unstable at low-pressure, was mostly vitrified during post-shock cooling. Mbale demonstrates an example of elevated post-shock temperature resulting in back-transformation of ringwoodite to olivine. In contrast, majoritic garnet in Mbale survives as unambiguous evidence of strong shock. In these two samples, HP minerals are exclusively associated with shock melt, indicating that elevated shock temperatures are required for rapid mineral transformations during the transient shock pulse. However, elevated post-shock temperatures can destroy HP minerals: in temperature sequence from bridgmanite to ringwoodite then garnet. NWA 091 and Chico are impact melt breccias with pervasive melting, blackening of silicates, recrystallization of host rock but no HP minerals. These features indicate near whole-rock-melting conditions. However, the elevated post-shock temperatures of these samples has annealed out HP signatures. The observed shock features result from a complex P-T-t path and may not directly reflect the peak shock pressure. Although HP minerals provide robust evidence of high pressure, their occurrence also requires high shock temperatures and rapid cooling during the shock pulse. The most highly shocked samples lack HP signatures but have abundant high-temperature features formed after pressure release. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2016

No description available.

No description available.

Abstract This work deals with microstructural features, chemistry and the search for traces of a meteoritic component in proximal tektite-like glasses from the Zhamanshin impact structure (Kazakhstan; further abbreviated as ZIS), and tektites from two strewn fields - moldavites (Czech Republic) and Australasian tektites (Laos; further abbreviated as AAT). Detailed microstructural observations and subsequent chemical and mineralogical studies of various types of inclusions were also performed; these inclusions were mostly found in the studied types of glasses for the first time ever. The aim of this PhD thesis was to (i) describe the microstructure of all studied glasses with a focus on yet unobserved microstructural phenomena, and (ii) try to determine the admixtures of meteoritic components in these glasses. In addition, the available target rocks, which could be a source of moldavites or AAT, were also studied. The microstructures of the studied glasses mutually differ. This is due to a diversity of parent materials and different glass formation conditions occurring during a particular impact event. A new type of "composite splash-form" has been identified among the ZIS glasses, whose chemical composition does not fit into the previously defined groups of irghizites or basic "splash-forms". For...

No description available.

From the early stages of planetary accretion and differentiation to the geomorphology of planetary surfaces and the evolution of life, fluids play an integral role in shaping planetary bodies. Fluid properties and processes were investigated under a range of planetary conditions through (1) experimental simulations of impact events and petrographic analysis of terrestrial impactites to determine the effects of shock metamorphism on fluid inclusion properties; and (2) numerical thermodynamic equilibrium modeling of aqueous alteration processes on Mars. Results of impact experiments and analyses of fluid inclusions in rocks from the Ries Crater and Meteor Crater indicate that fluid inclusions reequilibrate systematically with increasing shock pressure: stretching and decrepitating under low shock pressure conditions and collapsing at moderate shock pressures. Above the Hugenoit Elastic Limit, fluid inclusion vesicles are destroyed due to plastic deformation and phase transitions within the host mineral. This suggests that impact processing may result in the destruction of fluid inclusions, leading to shock devolatilization of target rocks. In addition, the absence of fluid inclusions in planetary materials does not preclude the presence of fluids on the meteorite's parent body. Thermodynamic modeling of aqueous alteration of basalt under Mars-relevant conditions provides constraints on the conditions under which secondary sulfates are likely to have formed. The results of this study indicate that jarosite is likely to form as a result of water-limited chemical weathering of basalts. Magnesium sulfates are only predicted to form as a result of evaporation. This suggests that in order to form the alteration assemblages recently observed by the Mars Exploration Rover Opportunity at Meridiani Planum, water must have been removed from the system after a geologically short period of time, before fluids came into equilibrium with mafic surface materials and became alkaline. / Ph. D.

The Gatun Structure (N 09º 05’ 58.1”, W 79º 47’ 21.8”, situated in the triple-canopy rainforest 10 km to the WSW of the Gamboa and about 2 km south of the Isle of Barbacoas, Republic de Panama), is a partially inundated, quasi-concentric surface feature ~3km in diameter, which appears in aerial photographs and in radar imagery as an arcuate chain of islands with a raised center. Although the structure has been heavily weathered and altered, it has retained morphology consistent with complex craters: an elevated circular central uplift 500-600 m in diameter and approximately 70 m high, and arcuate boundary ridges (a rim structure?) ranging from ~50-110 meters high. Within the central peak, highly altered and fractured siltstone of the Gatuncillo Formation (?) (Eocene) ± older rocks are uplifted and exposed through surrounding calcareous units of the Caimito Formation (Oligocene) and the Las Cascadas Formation (Miocene), the major target rocks in the region. Lithologies in the structure include highly fractured siliciclastic rocks (siltstone, sandstones and greywackes), limestones with anomalous spherical glass inclusions, both black and white hypocrystalline glasses (possible melt rocks), lithic fragmental breccias, and melt-bearing breccias (possible impact melt breccias and suevites) containing flow banding and evidence for selective melting of minerals. Three types of spherules (glass, fluid-drop and lithic), a pyroxenequartz “necklace” disequilibrium structure (coronas), plagioclase feldspars exhibiting mosaicism and partially amorphization and zeolitization, possible liquid immiscibility between melts of calcite and felpspathic glass, as well as decomposition of titano-magnetite, are all petrographic criteria that suggest a hypervelocity impact event. The structure is crosscut by numerous dikes of unshocked basalt and basaltic andesite related to volcanism along the Panamanian segment of the Central American arc to the south. However, the lithologies of the Gatun Structure are chemically inconsistent with the regional volcanic rocks and the unshocked volcanic rocks that crosscut the structure. An impact origin is our preferred interpretation for the Gatun structure due to the lack of an igneous relationship between the Gatun structure and the explosive volcanism of Panamanian arc, the presence of classical impactite lithologies within the site, the occurrence of spherules, maskelynite (as suggested by Raman Spectroscopy) and other disequilibrium shock features in the Gatun suite of rocks.

Title from PDF of title page. / Document formatted into pages; contains 558 pages. / Original thesis submitted in HTML and can be accessed at http://www.lib.usf.edu/ETD-db/theses/available/etd-10122001-142859/unrestricted/frame.html / td.pdf / Thesis (M.S.)--University of South Florida, 2002. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The Gatun Structure, (Latitude N 09° 05&softsign; 58.1", Longitude W 79° 47&softsign; 21.8", situated in the triple-canopy rainforest 10 km to the WSW of the Gamboa and about 2 km south of the Isle of Barbacoas, Republic de Panama), is a partially inundated, quasi-concentric surface feature 2.2 - 3km in diameter, which appears in aerial photographs and in radar imagery as an arcuate chain of islands with a raised center. Although the structure has been heavily weathered and altered, it has retained morphology consistent with complex craters: an elevated circular central uplift 500-600 m in diameter and 50m high, and arcuate boundary ridges (a rim structure?) ranging from 50-100 meters high. Within the central peak, highly altered and fractured siltstone of the Gatuncillo (?) formation (Eocene) (+-) older rocks are uplifted and exposed through surrounding calcareous units of the Caimito formation (Oligocene) and the Las Cascadas formation (Miocene), the major target rocks in the region. / ABSTRACT: Lithologies in the structure include highly fractured siliciclastic rocks (siltstone, sandstones and greywackes), limestones with anomalous spherical glass inclusions, both black and white hypocrystalline glasses (possible melt rocks), lithic fragmental breccias, and melt-bearing breccias (possible impact melt breccias and suevites), some of which contain flow banding and evidence for selective melting of minerals. Three types of spherules (glass, fluid-drop and lithic), a pyroxene-quartz "necklace" disequilibrium structure (coronas), plagioclase feldspars exhibiting mosaicism and partially amorphization, possible liquid immiscibility between melts of calcite and felpspathic glass, as well as decomposition of titanomagnite or ulvospinel, are all petrographic indicators of a hypervelocity impact event. / ABSTRACT: The structure is crosscut by numerous dikes of unshocked basalt and basaltic andesite related to volcanism along the Panamanian segment of the Central American arc to the south. However, the lithologies of the Gatun Structure are chemically inconsistent with the regional volcanic rocks and the unshocked volcanic rocks that crosscut the structure. The lack of an igneous relationship between the Gatun structure and the explosive volcanism of Panamanian arc the presence of classical shock lithologies within the site, and the occurrence of spherules, maskelynite and other disequilibrium shock features in the rocks, an impact origin is our preferred interpretation for the Gatun structure. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.