Matching Items (14)
Description
Lithium (Li) is a trace element in kerogen, but the content and isotopic distribution (δ7Li) in kerogen has not previously been quantified. Furthermore, kerogen has been overlooked as a potential source of Li to sedimentary porefluids and buried sediments. Thus, knowing the content and isotopic composition of Li derived from kerogen may have implications for research focused on the Li-isotopes of buried sediments (e.g., evaluating paleoclimate variations using marine carbonates).The objective of this work is to better understand the role of kerogen in the Li geochemical cycle. The research approach consisted of 1) developing reference materials and methodologies to measure the Li-contents and δ7Li of kerogen in-situ by Secondary Ion Mass Spectrometry, 2) surveying the Li-contents and δ7Li of kerogen bearing rocks from different depositional and diagenetic environments and 3) quantifying the Li-content and δ7Li variations in kerogen empirically in a field study and 4) experimentally through hydrous pyrolysis.
A survey of δ7Li of coals from depositional basins across the USA showed that thermally immature coals have light δ7Li values (–20 to – 10‰) compared to typical terrestrial materials (> –10‰) and the δ7Li of coal increases with burial temperature suggesting that 6Li is preferentially released from kerogen to porefluids during hydrocarbon generation. A field study was conducted on two Cretaceous coal seams in Colorado (USA) intruded by dikes (mafic and felsic) creating a temperature gradient from the intrusives into the country rock. Results showed that δ7Li values of the unmetamorphosed vitrinite macerals were up to 37‰ lighter than vitrinite macerals and coke within the contact metamorphosed coal.
To understand the significance of Li derived from kerogen during burial diagenesis, hydrous pyrolysis experiments of three coals were conducted. Results showed that Li is released from kerogen during hydrocarbon generation and could increase sedimentary porefluid Li-contents up to ~100 mg/L. The δ7Li of coals becomes heavier with increased temperature except where authigenic silicates may compete for the released Li. These results indicate that kerogen is a significant source of isotopically light Li to diagenetic fluids and is an important contributor to the global geochemical cycle.
ContributorsTeichert, Zebadiah (Author) / Williams, Lynda B. (Thesis advisor) / Bose, Maitrayee (Thesis advisor) / Hervig, Richard (Committee member) / Semken, Steven (Committee member) / Shock, Everett (Committee member) / Arizona State University (Publisher)
Created2022
Description
Most asteroids originated in larger parent bodies that underwent accretion and heating during the first few million years of the solar system. We investigated the parent body of S-type asteroid 25143 Itokawa by developing a computational model which can approximate the thermal evolution of an early solar system body. We compared known constraints on Itokawa’s thermal history to simulations of its parent body and constrained its time of formation to between 1.6 and 2.5 million years after the beginning of the solar system, though certain details could allow for even earlier or later formation. These results stress the importance of precise data required of the material properties of asteroids and meteorites to place better constraints on the histories of their parent bodies. Additional mathematical and computational details are discussed, and the full code and data is made available online.
ContributorsHallstrom, Jonas (Author) / Bose, Maitrayee (Thesis director) / Beckstein, Oliver (Committee member) / Barrett, The Honors College (Contributor) / Department of Physics (Contributor) / Materials Science and Engineering Program (Contributor)
Created2023-05
Description
During the Dawn mission, bright spots were discovered on the surface of the dwarf planet Ceres, which were determined to be evaporite deposits of sodium carbonate, ammonium carbonate, and hydrohalite. These deposits are significant because they indicate the presence of subsurface water and potential geologic activity on Ceres. These evaporites form from the brine-water mixture in the deep Ceres reservoir, which likely possesses the conditions ideal for forming complex organics. Here, we report the results of a suite of laboratory techniques (CHN Elemental Analyzer, Secondary Ion Mass Spectrometry, Fourier-Transform Infrared Spectroscopy, Gas Chromatography, and Brunauer-Emmett-Teller Analysis) for quantifying the likelihood of primordial carbon survival and distribution in analog materials found on Ceres, particularly in salt evaporates. We are specifically looking at if the amino acid glycine can be preserved in sodium chloride crystals. Our results conclude that if the Ceres brine reservoir is saturated with organics, and with the lower limits that we have for our instrumentation thus far, these techniques should be more than sufficient to measure glycine content should we ever receive samples from Ceres.
ContributorsReynoso, Lucas (Author) / Bose, Maitrayee (Thesis director) / Castillo-Rogez, Julie (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / School of Earth and Space Exploration (Contributor)
Created2023-05
Description
Characterizing the surface mineralogy of asteroids is critical to constraining their formation history and provides insight into the processes of planetary formation. One method of determining the surface mineralogy of asteroids is comparison of their visible to near-infrared reflectance (VNIR) spectra with laboratory spectra from meteorites and minerals. Subsequent in-situ investigation of these asteroids by spacecraft can supplement or supersede interpretations derived from Earth-based observations.I investigated a suite of aubrites, sulfide minerals, and metal-rich chondrites in a variety of forms (hand samples, powders, and slabs) to identify similarities with ‘spectrally featureless’ asteroids. I collected VNIR spectra and powder X-ray diffraction patterns of these samples and compared their overall reflectance and spectral slope with X-complex and T-, L-, and D-type asteroid spectra.
The Psyche Mission will orbit asteroid (16) Psyche beginning in 2026. I provide a pre-flight assessment of the surface composition of Psyche by comparing spectra of Psyche to a large spectral library of possible surface analog materials (e.g., iron meteorites, mesosiderites, pallasites, sulfides, enstatite, ordinary, and metal-rich chondrites, endmember silicates, and mixtures of silicates, metal, and sulfides). Spectra of Psyche are generally consistent with iron meteorite powder, mixtures of iron meteorite powder and low-Fe, low-Ca pyroxene, sulfide minerals, and the CH/CBb chondrite Isheyevo. Next, I demonstrate some anticipated capabilities of the Psyche Multispectral Imager by comparing spectral parameters derived from Imager-convolved data to those from high resolution laboratory spectra. I offer preliminary strategies for classifying surface composition based on Imager filter ratios and overall reflectance.
Last, I present an assessment of a benchtop, commercial-off-the-shelf (COTS) version of the Psyche Imager. The COTS Imager uses the same model CCD and a similar f-number commercial camera lens. I measured the gain, full well, linearity, read noise, quantum efficiency, and modulation transfer function to compare with eventual calibration data from the flight Imager. I validate the results of a radiometric model developed for the flight Imager with signal measurements from the COTS Imager. This work demonstrates that the COTS Imager is an effective testbed for validating Imager requirements and developing software and procedures for eventual calibration of the flight instrument.
ContributorsDibb, Steven (Author) / Bell, James (Thesis advisor) / Hardgrove, Craig (Committee member) / Garvie, Laurence (Committee member) / Elkins-Tanton, Linda (Committee member) / Bose, Maitrayee (Committee member) / Arizona State University (Publisher)
Created2021
Description
Brown dwarfs are a unique class of object which span the range between the lowest mass stars, and highest mass planets. New insights into the physics and chemistry of brown dwarfs comes from the comparison between spectroscopic observations, and theoretical atmospheric models. In this thesis, I present a uniform atmospheric retrieval analysis of the coolest Y, and late-T spectral type brown dwarfs using the CaltecH Inverse ModEling and Retrieval Algorithms (CHIMERA). In doing so, I develop a foundational dataset of retrieved atmospheric parameters including: molecular abundances, thermal structures, evolutionary parameters, and cloud properties for 61 different brown dwarfs. Comparisons to other modeling techniques and theoretical expectations from the James Webb Space Telescope (JWST) are made. Finally, I describe the techniques used to improve CHIMERA to run on Graphical Processing Units (GPUs), which directly enabled the creation of this large dataset.
ContributorsZalesky, Joseph (Author) / Line, Michael R (Thesis advisor) / Patience, Jennifer (Committee member) / Groppi, Christopher (Committee member) / Young, Patrick (Committee member) / Bose, Maitrayee (Committee member) / Arizona State University (Publisher)
Created2022
Description
Space weathering of planetary surfaces is a complex process involving many mechanisms that work independently over different timescales. This research aims to address outstanding questions related to solar wind rim formation on space weathered regolith and tests a new hypothesis that dielectric breakdown plays an important role in the optical maturation of lunar regolith. The purpose of this work is to highlight the limitations imposed by laboratory equipment to accurately simulate the solar wind’s effects on regolith and to provide physical context for the possible contributions of dielectric breakdown to space weathering. Terrestrial and lunar samples were experimentally irradiated and damage was characterized using electron microscopy techniques. Low-fluence proton irradiation produced differential weathering in a lunar mare basalt, with radiation damage on some phases being inconsistent with that found in the natural lunar environment. Dielectric breakdown of silicates revealed two electrical processes that produce characteristic surface and subsurface damage, in addition to amorphous rims. The results of this research highlight experimental parameters that if ignored, can significantly affect the results and interpretations of simulated solar wind weathering, and provides a framework for advancing space weathering research through experimental studies.
ContributorsShusterman, Morgan (Author) / Robinson, Mark S (Thesis advisor) / Sharp, Thomas G (Thesis advisor) / Hibbits, Charles (Committee member) / Bose, Maitrayee (Committee member) / Semken, Steven (Committee member) / Arizona State University (Publisher)
Created2023
Description
Subsolidus convection in the mantle of Earth is the driving mechanism behind plate tectonics and provides a central framework linking geophysical, geochemical, petrological, hydrological, and biological processes within the system. Seismic observations have revealed mantle heterogeneities in wide-ranging scales from less than tens of to thousands of kilometers. Understanding the origins and dynamics of these anomalies is critical to advance our knowledge on how mantle convection operates and coevolves with the surface system. This dissertation attempts to constrain the past, present and future of mantle dynamics with lines of evidence from seismology, geodynamics, petrology, geochemistry, and astrophysics. Above Earth’s core, two continent-sized large low shear velocity provinces (LLSVPs) beneath Africa and the Pacific Ocean were seismically detected decades ago. Yet their origin, composition, detailed morphology and influence over mantle convection remain elusive. First, I propose the two LLSVPs may represent the mantle remnants of the Moon-forming impactor Theia. I show that the mantle of Theia is intrinsically denser than Earth’s mantle and would have sunk and accumulated into LLSVP-like structures in the deepest mantle after 4.5 billion years. Second, I examined the maximum height of the two LLSVPs and determined that the African LLSVP is ~1,000 km higher than the Pacific counterpart. Using geodynamic simulations, I find the height of a stable LLSVP is mainly controlled by its density and the ambient mantle viscosity. With ~1,000 numerical experiments, I conclude that the origin of the great height difference between the LLSVPs is that the African LLSVP is less dense, and thus less stable than the Pacific LLSVP. Next, I numerically identified another dynamic scenario accounting for the vastly different height of the two LLSVPs, which is caused by catastrophic sinking of accumulated subducted slabs at the 660-km boundary. Last, targeting one ancient carbonatite above the African LLSVP, I show that lithium isotopes in humite measured by nanoscale secondary ion mass spectrometry was able to uncover the signature of a subducted oceanic crust in its magma source, which may return from the interior to the surface by mantle plumes.
ContributorsYuan, Qian (Author) / Li, Mingming (Thesis advisor) / Garnero, Edward (Committee member) / Shim, Sang-Heon (Committee member) / Hervig, Richard (Committee member) / Bose, Maitrayee (Committee member) / Arizona State University (Publisher)
Created2022
Description
The transport of hydrogen to the Earth’s deep interior remains uncertain. The upper mantle minerals have very low hydrogen solubilities (hundreds of ppm). The hydrogen storage capability in the transition zone minerals (2 wt%) is high compared to those of the upper mantle. The hydrogen storage in the lower mantle is not well known. The main minerals in the lower mantle bridgmanite and ferropericlase have very low hydrogen storage capacities (less than 20 ppm). In order to further understand the hydrogen storage in the lower mantle, a series of experiments had been conducted to simulate the environment similar to the Earth’s mantle. The experiments with hydrous Mg2SiO4 ringwoodite (Rw) show that it converts to crystalline dense hydrous silica, stishovite (Stv) or CaCl2-type SiO2(mStv), containing ∼1 wt% H2O together with bridgmanite (Brd) and MgO at the pressure-temperature conditions expected for lower mantle depths between approximately 660 to 1600 km. Brd would break down partially to dense hydrous silica (6–25 mol%) and(Mg,Fe)O in mid-mantle regions with 0.05–0.27 wt% H2O. The hydrous stishovite has a CaCl2 structure, which is common among hydrous minerals in the lower mantle. Based on this observation, I hypothesize the existence of hydrous phases in the lower mantle. The experiments found a new hexagonal iron hydroxide (η-Fe12O18+x/2Hx) between the stability fields of the epsilon and pyrite-type FeOOH at 60–80 GPa and high temperature. The new phase contains less H2O, limiting the H2O transport from the shallow to the deep mantle in the Fe–O–H system. Possible hydrogen storage in Ca-perovskite was studied. CaPv could contain 0.5–1 wt% water and the water in CaPv could distort the crystal structure of CaPv from cubic to tetragonal structure. In conclusion, hydrogen can be stored in hydrous stishovite in the shallower depth of the lower mantle. At greater depth, the new η phase and pyrite-type phase would take over the hydrogen storage. The role of CaPv in deep water storage needs to be considered in future studies.
ContributorsChen, Huawei (Author) / Shim, Sang-Heon (Thesis advisor) / Garnero, Edward (Committee member) / Bose, Maitrayee (Committee member) / Li, Mingming (Committee member) / Leinenweber, Kurt (Committee member) / Arizona State University (Publisher)
Created2019
Description
Volcanic eruptions are serious geological hazards; the aftermath of the explosive eruptions produced at high-silica volcanic systems often results in long-term threats to climate, travel, farming, and human life. To construct models for eruption forecasting, the timescales of events leading up to eruption must be accurately quantified. In the field of igneous petrology, the timing of these events (e.g. periods of magma formation, duration of recharge events) and their influence on eruptive timescales are still poorly constrained.
In this dissertation, I discuss how the new tools and methods I have developed are helping to improve our understanding of these magmatic events. I have developed a method to calculate more accurate timescales for these events from the diffusive relaxation of chemical zoning in individual mineral crystals (i.e., diffusion chronometry), and I use this technique to compare the times recorded by different minerals from the same Yellowstone lava flow, the Scaup Lake rhyolite.
I have also derived a new geothermometer to calculate magma temperature from the compositions of the mineral clinopyroxene and the surrounding liquid. This empirically-derived geothermometer is calibrated for the high FeOtot (Mg# = 56) and low Al2O3 (0.53–0.73 wt%) clinopyroxene found in the Scaup Lake rhyolite and other high-silica igneous systems. A determination of accurate mineral temperatures is crucial to calculate magmatic heat budgets and to use methods such as diffusion chronometry. Together, these tools allow me to paint a more accurate picture of the conditions and tempo of events inside a magma body in the millennia to months leading up to eruption.
Additionally, I conducted petrological experiments to determine the composition of hypothetical exoplanet partial mantle melts, which could become these planets’ new crust, and therefore new surface. Understanding the composition of an exoplanet’s crust is the first step to understanding chemical weathering, surface-atmosphere chemical interactions, the volcanic contribution to any atmosphere present, and biological processes, as life depends on these surfaces for nutrients. The data I have produced can be used to predict differences in crust compositions of exoplanets with similar bulk compositions to those explored herein, as well as to calibrate future exoplanet petrologic models.
In this dissertation, I discuss how the new tools and methods I have developed are helping to improve our understanding of these magmatic events. I have developed a method to calculate more accurate timescales for these events from the diffusive relaxation of chemical zoning in individual mineral crystals (i.e., diffusion chronometry), and I use this technique to compare the times recorded by different minerals from the same Yellowstone lava flow, the Scaup Lake rhyolite.
I have also derived a new geothermometer to calculate magma temperature from the compositions of the mineral clinopyroxene and the surrounding liquid. This empirically-derived geothermometer is calibrated for the high FeOtot (Mg# = 56) and low Al2O3 (0.53–0.73 wt%) clinopyroxene found in the Scaup Lake rhyolite and other high-silica igneous systems. A determination of accurate mineral temperatures is crucial to calculate magmatic heat budgets and to use methods such as diffusion chronometry. Together, these tools allow me to paint a more accurate picture of the conditions and tempo of events inside a magma body in the millennia to months leading up to eruption.
Additionally, I conducted petrological experiments to determine the composition of hypothetical exoplanet partial mantle melts, which could become these planets’ new crust, and therefore new surface. Understanding the composition of an exoplanet’s crust is the first step to understanding chemical weathering, surface-atmosphere chemical interactions, the volcanic contribution to any atmosphere present, and biological processes, as life depends on these surfaces for nutrients. The data I have produced can be used to predict differences in crust compositions of exoplanets with similar bulk compositions to those explored herein, as well as to calibrate future exoplanet petrologic models.
ContributorsBrugman, Karalee (Author) / Till, Christy B. (Thesis advisor) / Bose, Maitrayee (Committee member) / Desch, Steven J (Committee member) / Hervig, Richard L (Committee member) / Shock, Everett L (Committee member) / Arizona State University (Publisher)
Created2020
Description
Short-lived radionuclides (SLRs) once present in the solar nebula can be used to probe the Solar System’s galactic formation environment. Isotopic analyses reveal that the first solids formed in the Solar System, calcium- and aluminum-rich inclusions (CAIs) in chondritic meteorites, formed with the live SLRs 10Be (t1/2 = 1.4 Ma) and 26Al (t1/2 = 0.7 Ma). Beryllium-10 is produced when high-energy ions, solar energetic particles or galactic cosmic rays (GCRs), spall nuclei in gas or dust. The most likely source of Solar System 10Be is inheritance of GCR-irradiated protosolar molecular cloud material, but only if all CAIs recorded the same initial 10Be abundance. The goal of this dissertation is to assess the homogeneity of 10Be by measuring CAIs for 10Be–10B isotope systematics, correlated to 26Al–26Mg and oxygen isotopes.
I synthesized appropriate standards for secondary ion mass spectrometry (SIMS) measurements of 10Be–10B, necessary for accurate determination of the 10Be/9Be ratio. I then analyzed 32 CAIs for 10Be–10B as well as 6 CAIs for 26Al–26Mg and 5 CAIs for oxygen isotopes within this sample set using SIMS. Previous studies analyzed CAIs primarily from CV3 chondrites, which are known to have experienced thermal metamorphism and aqueous alteration. My work included a variety of CAIs (Type A, B, fine-grained, igneous) from CV3oxidized, CV3reduced, CO3, CR2, and CH/CB chondrites. Finally, after evaluating my data and literature data consistently, I statistically tested whether all CAIs belong to a single 10Be population. I find that the majority (~85%) of the normal (i.e., without large isotopic fractionations or anomalies), 26Al-bearing CAIs recorded a single value, 10Be/9Be = (7.0 ± 0.2) × 10-4. Although 6 CAIs recorded higher or lower values, these are plausibly explained by secondary alteration processes. The galaxy-wide average value of 10Be/9Be from GCR interactions 4.56 billion years ago is predicted to be <2 × 10-4; the value I measured is more than 3 times higher. Because GCRs trace supernovae and star formation, my results suggest a similarly enhanced star formation rate in the molecular cloud within ~1 kpc of the Sun, in the ~15 Ma prior to the Sun’s birth.
I synthesized appropriate standards for secondary ion mass spectrometry (SIMS) measurements of 10Be–10B, necessary for accurate determination of the 10Be/9Be ratio. I then analyzed 32 CAIs for 10Be–10B as well as 6 CAIs for 26Al–26Mg and 5 CAIs for oxygen isotopes within this sample set using SIMS. Previous studies analyzed CAIs primarily from CV3 chondrites, which are known to have experienced thermal metamorphism and aqueous alteration. My work included a variety of CAIs (Type A, B, fine-grained, igneous) from CV3oxidized, CV3reduced, CO3, CR2, and CH/CB chondrites. Finally, after evaluating my data and literature data consistently, I statistically tested whether all CAIs belong to a single 10Be population. I find that the majority (~85%) of the normal (i.e., without large isotopic fractionations or anomalies), 26Al-bearing CAIs recorded a single value, 10Be/9Be = (7.0 ± 0.2) × 10-4. Although 6 CAIs recorded higher or lower values, these are plausibly explained by secondary alteration processes. The galaxy-wide average value of 10Be/9Be from GCR interactions 4.56 billion years ago is predicted to be <2 × 10-4; the value I measured is more than 3 times higher. Because GCRs trace supernovae and star formation, my results suggest a similarly enhanced star formation rate in the molecular cloud within ~1 kpc of the Sun, in the ~15 Ma prior to the Sun’s birth.
ContributorsDunham, Emilie T. (Author) / Wadhwa, Meenakshi (Thesis advisor) / Desch, Steven (Committee member) / Hervig, Richard (Committee member) / Bose, Maitrayee (Committee member) / Schrader, Devin (Committee member) / Arizona State University (Publisher)
Created2020