Browsing by Author "Stowell, Harold"

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    Carbonation of flue gas desulfurization gypsum for CO2 sequestration
    (University of Alabama Libraries, 2021) Riddle, Jonathan B.; Donahoe, Rona J.; University of Alabama Tuscaloosa
    The IPCC asserts that to prevent a 2°C global temperature increase by the year 2050, CO2 must be removed from the atmosphere by sequestration. The goal of this study was to use FGD gypsum for CO2 mineralization and experimentally explore to find the optimal conditions for the highest conversation rates at ambient temperature while eliminating ammonia usage. While maintaining an alkaline solution using NaOH, a stirred reactor was utilized to study the effects of PCO2 (0.69, 2.07, 4.14, 6.89, and 17.24 bar), solution pH (12, 13, 13.5 and 14), solid-to-solution ratio (1:100, 1:80, 1:40, 1:100), and reaction time (10, 15, 30, and 120+ min) variation on the rate of conversion. The CaCO3 produced was calculated by Rietveld refinement of XRD patterns to determine the impact of each experimental variable.Experimental results showed solution pH was a primary control on mineralization, with nearly 100% conversion of FGD gypsum to CaCO3 occurring at initial pH = 13.5 and 14, for PCO2 > 2 bar and S:L = 1:100. At initial pH of 12, no gypsum conversion occurred. Reaction time also affected the amount of gypsum conversion to CaCO3. At initial pH = 13, S:L = 1:100 and PCO2 = 2.07 bar, 15 min was the optimum reaction time, achieving 75% conversion. However, with the same conditions at 360 min, a 61% conversion occurred, due to final pH’s below 7. Increasing S:L ratio resulted in increased gypsum-to-carbonate conversion. The optimal conditions for conversion of gypsum into calcite occurred at short reaction times of 15 min, low pressures at around PCO2 = 2.07 bar, and low solution ratios of S:L = 1:100, achieving 75% conversion. In contract, a reaction time of 360 min produced a result of only 61% conversion at the same PCO2 and S:L ratio, due to the pH dropping below 7. The results of this study demonstrate that FGD gypsum is a viable feedstock for CO2 mineralization, potentially offering a cheap and rapid method for carbon sequestration.
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    Chemical, Structural, and Magnetic Characterization of Lightning-Induced Glasses Produced from Volcanic Ash and Five Mineral Phases
    (University of Alabama Libraries, 2023) Woods, Taylor; Genareau, Kimberly
    Textures produced by volcanic lightning have been documented in the ashfall deposits of several explosive volcanic eruptions (e.g., Redoubt, USA, 2009; Pavlof, USA, 2016; Ejyafjallajökull, Iceland, 2010) and provide physical evidence of volcanic lightning. The extreme temperatures (>1500 °C) generated by lightning discharge will instantaneously vaporize, melt, and/or fuse airborne volcanic ash grains. Once the discharge dissipates, molten particles quench into new glass, forming a variety of textures, including lightning-induced volcanic spherules, spherule aggregates, pumiceous particles, hair-like particles, and plate-like particles. While several studies have analyzed the formation processes of lightning-induced textures, there is limited research on the resulting chemical, structural, and magnetic alteration. This dissertation seeks to advance our understanding of how lightning affects the chemical, structural, and magnetic properties of volcanic ash using a combination of scanning electron microscopy, wavelength dispersive spectroscopy, energy dispersive spectroscopy, Raman spectroscopy, and vibrating sample magnetometry. High-current impulse experiments were conducted on very fine (< 32 µm) andesitic volcanic ash samples and mineral powders at peak currents of ~7 kA, ~25 kA, and ~40 kA. Analysis of post-experimental lightning-induced textures reveals that lightning will irrevocably alter andesitic ash grains and powdered mineral fragments by transforming them into rounded glassy particles with chemically distinct and variable glass compositions. The composition of the glass depends on the initial glass chemistry and mineral content of the starting material and the degree of mixing between partially or completely melted mineral and glass phases. Lightning-induced chemical alteration may also include secondary precipitation of microcrystalline dendritic magnetite. Due to higher concentrations of ferrimagnetic minerals, the saturation magnetization of the post-experimental albite and magnetite samples increased. However, results also showed that the silicate-rich samples of albite, labradorite, augite, and hornblende became more paramagnetic due to the redistribution of iron from iron-bearing minerals into lightning-induced glass phases. Although specific to volcanic lighting and andesite ash, the results presented in this dissertation are relevant for other types of atmospheric dust, which may act as ice nuclei, and provide insights into high-temperature and pressure alteration of materials affected by lightning or impact events on Earth, the Moon, and throughout the solar system.
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    Compositional and Chronological Studies on Chondritic and Achondritic Meteorites: Implications for the Formation and Evolution of the Solar System
    (University of Alabama Libraries, 2024) Kouvatsis, Ioannis; Genareau, Kimberly
    Meteorites represent some of the most important materials we have for understanding our Solar System. Chondrites are stony meteorites that represent undifferentiated parent bodies (i.e. primitive materials that have not been subjected to significant melting or differentiation) thus providing a snapshot of the conditions prevailing in the early Solar System. By contrast, achondrite meteorites have been differentiated and reprocessed by melting and recrystallization of their parent bodies (e.g., Mars or larger asteroids like 4 Vesta). Chronometers with various half-lives and sensitivities to disturbances (e.g. heating and thermal/shock effects from impacts) can provide significant information about the formation, and subsequent evolution, of meteorite parent bodies. In my dissertation, I am examining chondritic material to understand processes that took place at the very first stages of the Solar System. Moreover, I am investigating achondrites to understand the evolution and impact history of asteroid parent bodies. Chapter 1 is an introduction to asteroids and meteorites, and I briefly describe the subject of each subsequent chapter of this dissertation. Chapter 2 is an investigation of the carbonaceous chondrite meteorite Aguas Zarcas, which was an observed fall in 2019 in Costa Rica, and includes a study of textures and compositions of its phases (e.g., chondrules, minerals, matrix etc.) to decipher the formation of chondrites and early Solar System processes such as brecciation and aqueous alteration. Chapter 3 utilizes in-situ lead-lead (Pb-Pb) dating using Secondary Ionization Mass Spectrometry (SIMS) on two distinct groups of meteorites: mesosiderites and eucrites. Eucrites, part of the Howardite Eucrite Diogenite (HED) clan, are thought to have crystallized as lavas or in shallow dykes and plutons on asteroid Vesta's surface and are potentially linked to mesosiderites due to mineralogical, geochemical, and isotopic similarities. In this chapter, I study the petrography and perform Pb-Pb dating of two eucrites and three mesosiderites, with the aim of examining their proposed link. Chapter 4 expands the chronological investigation of achondrites by including Argon-Argon (Ar-Ar) dating of a eucrite and a mesosiderite previously analyzed in Chapter 3. The combination of chronometers with different sensitivities (such as Pb-Pb and Ar-Ar) can provide valuable insights into the processes active on asteroid parent bodies resulting in a better understanding of their formation and evolution. Moreover, the combined data from the two chronometers can provide information on whether HEDs and mesosiderites come from the same parent body. This focused study highlights the complex nature of primitive Solar System materials, while also exploring consistency in event timings between different possibly related meteorite groups. In Chapter 2, through textural and chemical studies of the carbonaceous chondrite Aguas Zarcas, I observed two lithologies, separated by a boundary, which exhibited different degrees of aqueous alteration. A more detailed study revealed the fine-grained rims present around major phases were likely formed in the solar nebula, and not within the parent body through aqueous alteration processes. In Chapter 3, I analyzed melt clasts in eucrites and phosphate minerals in mesosiderites using Pb-Pb dating, to investigate initial crystallization ages and potential resetting from large magnitude impacts. In Chapter 4, I analyzed bulk samples of previously studied samples from Chapter 3 using Ar-Ar dating, to investigate impacts of smaller magnitude that may not have been recorded by the more robust Pb-Pb chronometer. The combination of the two chronometers could help us understand the formation and evolution of asteroid parent bodies in detail.
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    Prolonged Metamporphism During Long-Lived Terrane Accretion: Sm-Nd and U-Pb Zircon Geochronology and Pressure-Temperature Paths from the Salmon River Suture Zone, West-Central Idaho, USA
    (2017-06-30) McKay, Matthew P.; Bollen, Elizabeth M.; Gray, Keith D.; Stowell, Harold; Schwartz, Joshua J.; University of Alabama Tuscaloosa
    The Salmon River suture zone of western Idaho (USA) records mid-crustal metamorphism and deformation associated with orogenesis during Mesozoic accretion of volcanic arc terranes to western Laurentia. We present petrographic and microstructural observations, garnet geochemistry, pressure-temperature isochemical phase diagrams, and Sm-Nd garnet and U-Pb zircon ages to investigate the timing and conditions of metamorphism in the Salmon River suture zone. The Salmon River suture zone is comprised of three thrust sheets: from east to west, the amphibolite facies Pollock Mountain plate, upper greenschist to amphibolite facies Rapid River plate, and greenschist facies Heavens Gate plate. The Pollock Mountain plate was isothermally loaded from 6 to >8 kbar at ~700 °C between 141 and 124 Ma during northwest-southeast crustal shortening. The underlying Rapid River plate was isothermally loaded from 7 to ~10 kbar at 600–650 °C during ca. 124–112 Ma metamorphism, which is contemporaneous with late- to post-peak metamorphism and ca. 118 Ma exhumation of the overlying Pollock Mountain plate. In the Rapid River plate, thrust sheet emplacement induced high-strain ductile deformation and led to regional development of linear-planar fabrics. The 206Pb/238U zircon ages for syndeformational to postdeformational magmatism record ca. 117 Ma or younger juxtaposition of the two plates on the southeast-dipping Pollock Mountain thrust fault. Coeval 124–112 Ma metamorphism of the Rapid River plate, ca. 118 Ma exhumation of the Pollock Mountain plate, and ca. 117 Ma or younger movement along the Pollock Mountain fault suggest that metamorphism of the Rapid River plate was possibly driven in part by thrust juxtaposition and loading along the Pollock Mountain fault. In this context, we interpret that metamorphism records diachronous thrust stacking during prolonged (>30 m.y.) accretionary orogenesis in western Idaho.