Doctor of Philosophy, The Ohio State University, 2024, Earth Sciences

Knowledge of the distribution of Fe2+ and Mg between olivine and melt (the distribution coefficient, KD) is crucial to understand the origin and evolution of magmas. However, there is disagreement regarding which variables (temperature, melt composition, and oxygen fugacity – fO2) influence the value of KD, as well as the magnitude of their effects. To evaluate the dependence of KD on these variables, data were compiled from literature consisting of equilibrium olivine-melt pairs in experiments at controlled temperature, fO2, and 1 atm pressure. The results confirm that KD is essentially independent of temperature and fO2. However, it is strongly dependent on melt composition (particularly the concentration of silica and alkalis). An evaluation of different published formulations for KD using these data demonstrates that the expression of Gee and Sack (1988) is the most accurate and precise. Furthermore, a new and simpler model based on variation of KD with silica and alkalis has been fit to the olivine-melt database. This reproduces KD with the same accuracy and precision as the Gee and Sack (1988) formulation. The olivine-melt database also illustrates that KD can be used to calculate the proportion of the different valence states of iron in the melt (the Fe3+/ΣFe ratio), which cannot be measured using routine analytical techniques. The melt Fe3+/ΣFe can then be related to fO2 using empirical relationships. This method, referred to as the Olivine-Melt Equilibrium (OME) method, reproduces the fO2 imposed on the experiments within ±0.3 log units. This method was applied to compiled data for natural samples from literature from mid-ocean ridges, ocean islands, back-arc basin spreading centers, and volcanic arcs. Olivine-melt calculated values of fO2 for each location investigated agree with the results of independent techniques. These include compiled measurements of Fe3+/ΣFe ratios using Fe K-edge μ-X-ray Absorption Near Edge Structure (XANES) spectroscopy, as we (open full item for complete abstract)

Committee: Michael Barton (Advisor); Berry Lyons (Committee Member); Daniel Kelley (Committee Member); Derek Sawyer (Committee Member); David Cole (Committee Member) Subjects: Earth; Geochemistry; Geological; Geology; Petrology; Plate Tectonics

Doctor of Philosophy, The Ohio State University, 2024, Earth Sciences

Fuego and Pacaya volcanoes in Guatemala are highly active volcanoes located near dense population centers. Despite this, both volcanoes are understudied, and there is insufficient data to fully understand their magma evolutionary processes and magma plumbing systems, and to adequately constrain eruption triggers. Because these are key components of volcanic hazard mitigation efforts, further investigation of Fuego and Pacaya will provide disaster response agencies with vital information to minimize loss of life and property in vulnerable Guatemalan communities. This research involves a petrological and geochemical study of recent and historical eruptive products from Fuego and Pacaya and will provide insight into the present and past magma storage conditions, recharge processes, and eruption triggers. Mineralogical data presented in this study highlight the complex, polybaric nature of magma storage and eruption at both Pacaya and Fuego Volcanoes. A detailed analysis of mineralogical data from Fuego 2018 eruption finds that this paroxysm was likely sourced from Fuego's extensive magma storage system, and that this eruption involved rapid decompression of these magmas creating the observed variation in crystal compositions and groundmass glass textures observed in these samples. However, because this eruption was a high-volume paroxysm, recharge of the magma plumbing system is necessary. Therefore, future sampling and petrologic monitoring is key for understanding this magma supply problem. Pacaya volcano has extensive evidence for magma mixing, assimilation, and recharge events, and mineralogical data points to magma mixing being an important eruption trigger. This finding, along with geobarometry work indicating that magma storage at Pacaya is generally at shallow depths (0 to 4 km beneath the crater), are both important considerations for future hazard mitigation efforts. This study is part of a larger collaborative, interdisciplinary effort at the Ohio State (open full item for complete abstract)

Committee: Michael Barton (Advisor); Demian Gomez (Committee Member); David Cole (Committee Member); Daniel Kelley (Committee Member); Barry Lyons (Committee Member) Subjects: Geology; Mineralogy; Petrology

Master of Science, University of Akron, 2024, Geology

Partial melting of hydrous phases such as amphibole, biotite, and muscovite occurs in orogens where distributed ductile thinning is causing exhumation of mid- to lower-crustal rocks. The partial melting of these hydrous phases contributes significantly to the physical and chemical evolution of the crust, as well as affecting the crust's strength. The Si-rich melts generated from partial melting reactions of mid- to lower-crustal assemblages migrate toward the upper crust leaving a more mafic restite. Previous laboratory experiments conducted on amphibole-, biotite-, or muscovite-bearing rocks performed at rapid strain rates (10-4/s to 10-5/s) result in brittle deformation due to high local pore pressures. These rapid experiments suggest this brittle behavior is the likely mechanism causing melt segregation in the crust. However, field evidence and slower strain rate experiments (10-6/s to 10-7/s) suggest that crystal plastic processes may be dominant during syndeformational partial melting. To investigate grain-scale melt segregation mechanisms in a common lower crustal protolith, I performed a suite of axial compression and general shear experiments on an amphibole-bearing source rock during syndeformational partial melting at T = 800-975°C, Pc = 1.5 GPa, at a strain rate (ε) of 1.6 x 10-6/s. I also performed axial compression experiments on a biotite-bearing gneiss and a muscovite-bearing quartzite at T = 950°C, Pc = 1.5 GPa, at a strain rate (ε) of 1.6 x 10-6/s to compare the differences in melt development depending on which hydrous phase is partially melting. The Nemo Amphibolite (d = 140 ± 85 μm) is composed of 62 vol% amphibole (Fe-hornblende), 27 vol% plagioclase (andesine; An30Ab69Or1), 8 vol% quartz, and 3 vol% titanite. The biotite-bearing gneiss (d = 80 +/- 40 microns) consists of quartz (43 vol%), plagioclase (andesine (An22Ab77Or1); 40 vol%), biotite (16 vol%), and ~1 vol% muscovite/Fe-Ti oxides. The muscovite-bearing quartzite is composed of 90 vol% q (open full item for complete abstract)

Committee: Caleb Holyoke (Advisor); Molly Witter-Shelleman (Committee Member); David Steer (Committee Member) Subjects: Earth; Experiments; Geochemistry; Geological; Geology; Mineralogy; Petrology; Plate Tectonics

Master of Science (MS), Bowling Green State University, 2023, Geology

Minna Bluff is a 45 km long volcanic peninsula that juts out from the mainland into the southern Ross Sea and is part of the Late Cenozoic Erebus Volcanic Province within the West Antarctic Rift System (WARS). Here the origin of an ultramafic xenolith hosted within a basanite lava flow is investigated through petrography, mineral and whole rock chemistry. The xenolith is an olivine pyroxene hornblendite as defined by its mineralogy and abundances of amphibole (52%), clinopyroxene (34%), olivine (10%), plagioclase (2%) and spinel (1%). Accessory minerals (<1%) include magnesite, ilmenite, and apatite. The sample has textures that indicate a complex history including replacement of clinopyroxene by amphibole, pervasive melt inclusion trains, and microfractures which contain small amounts of carbonate tentatively identified as magnesite. Amphibole is magnesiohastingsite, clinopyroxene is diopside (Wo44-46 En39-41), olivine is forsterite (Fo66-67), plagioclase is labradorite (An 47-50, Ab 47-50), and spinel is magnetite. Thermobarometric estimates suggest that the clinopyroxene was at equilibrium at depths between 15 and 25 km, which approximates the Moho depth beneath this recently active region of the WARS known as the Terror Rift. Metasomatic reaction caused the replacement of clinopyroxene with amphibole and whole rock enrichment in incompatible elements, yielding higher light rare earth (LREE) to heavy rare earth (HREE) element ratios. Magnesite within microfractures formed either by reaction of olivine with hydrothermal fluids near the surface, or deeper and simultaneously with replacement of clinopyroxene. The abundant inclusion trains are interpreted as representing remnants of this metasomatizing agent. This study concludes that the olivine pyroxene hornblendite xenolith represents an earlier stage of partial melting of the same source that produced the host lava, but at a higher percentage of partial melting resulting in it being depleted in trace elements r (open full item for complete abstract)

Committee: Kurt Panter Ph.D. (Committee Chair); Yuning Fu Ph.D. (Committee Member); John Farver Ph.D. (Committee Member) Subjects: Geochemistry; Geology; Petrology

Master of Science, Miami University, 2023, Geology and Environmental Earth Science

Lunar meteorites have the potential to expand our knowledge of the Moon's geological evolution and the processes which operate on differentiated objects in the inner Solar System. This study focuses on meteorite DOM 18543,9. DOM 18543,9 is a basaltic regolith breccia. Clasts within its glassy matrix include basalts, gabbros, and impact melt breccias. Mineral fragments include (clino)pyroxenes, olivines, and plagioclase, with trace oxides, sulfides, and phosphates. Melt veins up to 80μm wide and glass spherules (up to 400μm) are abundant. In addition, 3-phase symplectites composed of Fe-rich olivine, clinopyroxene, and silica occur. Pyroxenes are of augite and pigeonite compositions while olivines are dominantly fayalitic (up to Fa98.7). Plagioclase feldspars throughout the clasts and mineral fragments are predominantly anorthitic. Compared to Apollo basalts, DOM 18543,9 pyroxenes exhibit similar Mg/(Mg+Fe) vs Ti/(Ti+Cr) signatures to pyroxenes in Apollo 12 and 15 low-Ti basalts. Additionally, pyroxene CaO-MgO-FeO systematics are similar to those observed in Apollo 12, 15, and 17 basalts. Furthermore, the petrologic makeup of DOM 18543,9 (and inferred mare-related origin) may support a petrogenetic link to the YAMM meteorite suite and derivation from cryptomare around the Schiller-Schickard crater area on the Moon's nearside.

Committee: Claire McLeod Dr. (Advisor); Mark Krekeler Dr. (Committee Member); Marion Lytle Dr. (Committee Member) Subjects: Geochemistry; Geology; Petrology

Master of Science (MS), Ohio University, 2023, Geological Sciences (Arts and Sciences)

Syrtis Major Planum is a low-relief shield volcano on Mars with a minimal dust content and is considered the best example of a Surface Type 1 dominated volcanic region. While no longer volcanically active, lava flows that were generated from Syrtis may serve as a reflection of the processes that were occurring in its magmatic source from the Late Noachian to the Late Hesperian martian epochs. This study sought to identify compositional, mineralogical, and petrological variations between temporally and spatially distinct flows using thermal infrared (TIR) spectroscopy to determine the extent of any differentiation throughout the volcanic record of Syrtis Major. A total of 610 Thermal Emission Spectrometer (TES) emissivity spectra were selected from 30 thermophysical units (assumed to be individual lava flows) as delineated by Demchuk (2021). Averaged TES spectra for all 30 units were modeled using spectral endmembers over a defined spectral range which excluded the prominent martian atmospheric CO2 absorption centered at 667 cm-1. Modeled endmember percentages are reflective of mineral modes, which were used to calculate bulk chemistries and rock types for each unit. Lava flows are dominated by high-Ca pyroxene and plagioclase feldspar, and bulk chemistries are consistent with mafic igneous rocks. Units are predominantly characterized as tholeiitic basalt, with rock types ranging from picrite to basaltic andesite. Any apparent variations in minerals, major oxides, and rock types across much of Syrtis from the Late Noachian to the Late Hesperian, are within the detection limits of the technique, which implies limited or no melt evolution in the magmatic source of Syrtis. Comparisons to terrestrial volcanoes and volcanic regions suggest differences in tectonic regimes and crustal thicknesses could affect the manifestation of hot spot volcanism on Mars. Further research on smaller Syrtis lava flows is needed to determine if temporal and/or spatial compositiona (open full item for complete abstract)

Committee: Keith Milam (Advisor) Subjects: Geochemistry; Geographic Information Science; Geology; Mineralogy; Petrology; Planetology; Remote Sensing

Master of Science, University of Akron, 2023, Geology

Within the mid to lower continental crust distributed ductile thinning occurs, in orogens that form mountains like the Himalayas and Appalachia, due to a weak middle to lower crust that deforms laterally in response to loading of a thickened, cold upper crust. This thinning destabilizes large orogens and causes the exhumation of hot and weak rock from the mid to lower crust that begins to partially melt. This melting further weakens the rocks and may affect the deformation mechanisms operating in the crust. Melting has been seen to have impacts on the deformation mechanisms and resulting lattice preferred orientations (LPO) that form in olivine-basalt aggregates (Holtzman et al., 2003). To investigate the effects of partial melting on deformation mechanisms and LPO development in two common foliated felsic rocks, I performed general shear deformation experiments on a fine-grained quartzite and fine-grained gneiss at T = 800°C, 850°C, 900°C, 950°C, or 975°C, P = 1.5 GPa, and strain rate of 6*10-5/s. The quartzite (grain size ~30 microns) is composed of 90% quartz and 10% muscovite. The fine-grained gneiss (grain size ~50 microns) is composed of 43% quartz, 40% plagioclase, 16% biotite, and 1% accessory minerals. The foliation in the slices of each rock was oriented parallel to the shear plane between Al2O3 shear pistons with a cut made at 45° to the compression direction. Experiments were performed at a range of temperatures to change the melt fraction present in the rocks during deformation (Melt = ~0%, 0.25%, 0.5%, and 1%). The yield stress of Moine Thrust quartzite decreased as a function of increasing temperature from ~1000 to ~300 MPa. However, all the experiments with melt present (T equal to to greater than 850°C) significantly strain hardened after a shear strain (g) of 1. This hardening may be due to the presence of melt along grain boundaries which is absorbing water from the recrystallizing quartz grains which slows diffusive recovery in quartz. The Gne (open full item for complete abstract)

Committee: Caleb Holyoke (Advisor); John Peck (Committee Member); Molly Witter-Shelleman (Committee Member) Subjects: Earth; Environmental Geology; Experiments; Geochemistry; Geological; Geology; Geophysics; Geotechnology; High Temperature Physics; Mineralogy; Petrology

Doctor of Philosophy, Miami University, 2023, Geology and Environmental Earth Science

Basaltic magmatism is a fundamental process through which rocky objects across the Solar System differentiate and evolve. Basaltic partial melts generated within planetary mantles provide a record of the geologic evolution of mantle source regions, magma storage and ascent dynamics, and the processes through which primary and secondary crusts are established. In terrestrial basaltic systems, comprehensive macro- and microscale investigations that integrate the physical (e.g. crystal size and shape) and chemical (e.g. elemental stratigraphy) properties of crystals have often led to the identification of multiple, petrogenetically distinct crystal populations throughout one mineral phase. This has led to a so-called “paradigm shift” in the field of terrestrial igneous petrology: magmatic systems are “open” in nature. However, the extent to which open system processes exist on other rocky, differentiated planetary objects remains largely unconstrained. Thus, this work targets a suite of basaltic samples collected during the lunar Apollo missions, representing the only direct sampling of basaltic materials from spatially constrained locations on another inner Solar System object. Through a detailed textural, mineralogical, and geochemical investigation this work provides new insights into the emplacement of lava on the lunar surface and new constraints on the evolution of magmatic systems within (and on) the lunar crust. First, X-ray computed tomography (XCT) datasets from a lithologically diverse suite of Apollo basaltic rock chips captured and quantified lunar basalt petrofabrics in 3D. From study of mineral (e.g., ilmenite), and vesicle distributions, resulting textures were found to be broadly consistent with terrestrial pahoehoe lava flow stratigraphy. Second, petrographic study and in-situ geochemical analysis of major and minor silicate phases in thin sections of the same samples indicated the presence of distinct crystal populations within multiple phases. This (open full item for complete abstract)

Committee: Claire McLeod (Advisor); Mark Krekeler (Committee Member); Burcin Bayram (Other); Barry Shaulis (Committee Member); Elisabeth Widom (Committee Member) Subjects: Geochemistry; Geology; Petrology

Master of Science, Miami University, 2022, Geology and Environmental Earth Science

The Trans-Mexican Volcanic Belt is host to several active volcanic fields, within which are clusters of monogenetic volcanoes that erupt in close temporal and spatial proximity to one another. These fields provide a unique opportunity to investigate the petrologic and geochemical evolution associated with monogenetic magmatism at a single location over a well-constrained timeframe. The Holocene Tacambaro cluster, located in the Michoacan-Guanajuato volcanic field in central Mexico, comprises four monogenetic volcanoes. These centers erupted basaltic andesite to andesite over ~3,300 years, starting with an explosive eruption and evolving to effusive eruptions, with increasing SiO2 and decreasing crystal contents. We have performed petrography, elemental and isotopic analyses, and geochemical modeling of Tacambaro cluster samples to assess the potential roles of fractional crystallization, crustal assimilation, and mantle source enrichment contributing to their petrogenesis. Major elements are generally consistent with variable degrees of fractional crystallization, but trace elements and isotopes are indicative of mantle source enrichment. The temporal-compositional variations are interpreted to derive from multiple melts of a heterogeneous, slab fluid-enriched mantle source, which undergo variable crustal storage and extents of fractional crystallization.

Committee: Elisabeth Widom (Advisor); Claire McLeod (Committee Member); Michael Brudzinski (Committee Member) Subjects: Geochemistry; Geology; Petrology

Doctor of Philosophy, Miami University, 2022, Geology and Environmental Earth Science

Volcanic rocks record the complex nature of magmatic systems. The mineralogical, petrological, and geochemical heterogeneity that exists within an eruptive unit at a single volcano is challenging to reconcile with a static magma chamber model. Current understanding, therefore, supports the presence of complex, dynamic trans crustal magmatic systems (TCMSs) that consist of interconnected regions of magma storage where liquid-poor, crystal-rich mushes exist and variably interact. This dissertation presents an investigation into the magmatic and crustal components of TCMSs through a study of andesitic-dacitic lavas, hornblendite cumulates, and crustal xenoliths from the Plio- Pleistocene Pampa Aullagas (PA) and Quillacas (QL) monogenetic centers on the Bolivian Altiplano, Central Andes. In Chapter 1, amphibole's role in continental arc petrogenesis is investigated through a textural and geochemical study of hornblendite cumulates entrained within QL lavas. Granular, idiomorphic textures, the absence of relict clinopyroxene, and mesocumulate textures defined by intercumulus feldspar, apatite, and Fe-Ti oxides all support the formation of the hornblendites as cumulates in the lower arc crust. Reaction rims associated with cumulus amphiboles record cumulate mobilization, ascent, and eruption through TCMSs over relatively short timescales (<30 days). In Chapter 2, the crustal components of the QL and PA TCMSs are investigated through a lithologically diverse crustal xenolith suite which provides insights into the tectonomagmatic history of the Central Andean continental crust. From U-Pb zircon geochronology, evidence for ~3 Ga of tectono-magmatic events is recorded within the Central Andean continental basement. Age population peaks correlate with global supercontinent cycles, including the establishment of Nuna, Rodinia, and Gondwana, and record a long history of terrane accretion and arc magmatism along the western margin of South America. In Chapter 3, the origin of num (open full item for complete abstract)

Committee: Claire McLeod (Advisor); Michael Brudzinski (Committee Member); Jennifer Blue (Committee Member); Alicia Cruz-Uribe (Committee Member); Mark Krekeler (Committee Member) Subjects: Geochemistry; Geology; Mineralogy; Petrology

Bachelor of Science (BS), Ohio University, 2022, Geological Sciences

The Tavsanlı Zone high-pressure/low-temperature (HP/LT) metamorphic belt exposed in NW Turkey represents the subducted northern margin of the Anatolide-Tauride Platform. The subduction of the Anatolide-Tauride Platform beneath the Pontides resulted in the closure of the Neotethys Ocean, a Mesozoic Ocean that separated Laurasia (Pontides) and Gondwana (Anatolide-Taurides). Numerous tectonic models have been proposed to explain how the closure of the ocean occurred, however, debate still exists as to the number of ocean basins and subduction zones involved and their ages. This research uses U-Pb geochronology and trace element data from zircons in three lawsonite blueschist and eclogite facies metamafic samples collected from the Tavsanlı Zone to constrain the timing of subduction initiation and metamorphism in the region. Zircons from one lawsonite eclogite sample lack older cores and yield ages of 88 Ma – 116 Ma, which are interpreted as metamorphic ages. Zircons from the other lawsonite eclogite sample and the lawsonite blueschist preserve older cores and younger rims. Core ages range from ~170 Ma – 907 Ma, whereas rim ages range from 69 Ma – 142 Ma. Probability density plots indicate common zircon growth events at ~95 Ma, ~110 Ma, ~130 Ma, and ~180 Ma. The ~95 Ma, ~110 Ma, and ~130 Ma age peaks likely represent metamorphic events, whereas the 180 Ma age peak likely represents the age of the protolith. Zircon cores with ages > 180 Ma are likely xenocrystic in origin. The U/Yb and Hf contents of the ~180 Ma zircon cores indicate that the protolith for both the lawsonite blueschist and lawsonite eclogite originated from an enriched mantle or continental source. Zircon cores with ages > 180 Ma have similar U/Yb and Hf contents as the ~180 Ma zircon cores, likely indicating a similar origin. The ~95 Ma and ~110 Ma zircon age peaks are consistent with previous 40Ar/39Ar phengite and Lu-Hf garnet and lawsonite geochronology results from the Sivrihisar Massif and indicate (open full item for complete abstract)

Committee: Katherine F. Fornash (Advisor); Eung Seok Lee (Committee Member); Alycia Stigall (Committee Member) Subjects: Geochemistry; Geology; Petrology

Master of Science, Miami University, 2022, Geology and Environmental Earth Science

Observations of Allan Hills 81005 via PLM and SEM-EDS are consistent with the classification of anorthositic regolith breccia. Clasts of anorthosite, basalt, granulite, and impact melt breccia are present. The brecciated matrix is dominated by plagioclase, minor (clino)pyroxene, and rarer olivine in addition to trace oxides and sulfides. Phosphates, spinels, glass spherules, and crystalline spherules are rare and not ubiquitous in studied sections. In section -92, a spinel-bearing dunite clast is present alongside several pink spinel-bearing troctolitic clasts. The composition of dunitic olivines is consistent with the lunar Mg-suite as exemplified by Mg#, CaO, Cr, and Mn systematics. Compositions also overlap with those from dunite sample 72417. Both are distinct from non Mg-suite dunites in 74275 and the modeled composition of early-formed LMO cumulates. Spinels within the dunite clast are also consistent with spinels within Mg-suite dunites (Mg# ~50, Cr# ~70) while troctolitic pink are consistent with Mg-suite spinel troctolites (Mg# ~70-80, Cr# <10). Collectively, the clast and mineral assemblages support an origin of ALHA81005 from the lunar highlands. The observation of a lunar dunite contributes to our understanding of Mg-suite magmatism during lunar differentiation.

Committee: Dr. Claire McLeod (Advisor); Dr. Mark Krekeler (Committee Member); Dr. John Rakovan (Committee Member) Subjects: Chemistry; Geochemistry; Geological; Mineralogy; Petrology; Planetology; Remote Sensing; Scientific Imaging

Master of Science (MS), Ohio University, 2021, Geological Sciences

Syrtis Major is an important and somewhat under-studied shield volcano on Mars, being distinct from other martian volcanoes in terms of morphology and the amount of exposed autochthonous or parautochthonous low-albedo material available for spectral studies. Syrtis Major lava flows were distinguished and mapped based on thermophysical properties when using thermal infrared data such as Thermal Emission Spectrometer (TES) and Thermal Emission Imaging System (THEMIS) and visible imagery such as Context Camera (CTX), Mars Orbiter Camera (MOC), and High Resolution Imaging Science Experiment (HiRISE). Defined units were assigned relative ages through crater counting processes using crater density estimates. Unit ages ranged from Late Noachian to Late Hesperian. An analysis of thermal infrared emissivity data indicated that 12 of the units were geochemically similar which could suggest undifferentiated lavas. Further spectral analysis of the thermophysical units could give greater constraints on the mineralogy and geochemistry of Syrtis Major.

Committee: Keith Milam PhD (Advisor); Katherine Fornash PhD (Committee Member); Gregory Springer PhD (Committee Member) Subjects: Astronomy; Geochemistry; Geology; Mineralogy; Petrology; Planetology; Remote Sensing

Master of Science (MS), Ohio University, 2020, Geological Sciences

This study evaluated the use of geophysical well logs to interpret igneous and metamorphic lithologies from the Precambrian basement in east-central Ohio.Geophysical well logs are a staple of the oil and gas industry, but are designed and calibrated for use in sedimentary rocks. Thin-section petrography and X-ray Fluorescence were used to analyze 13 and 16 basement sidewall core samples, respectively, from two wells in Noble and Coshocton counties. The samples were separated into two broad groups on a standard Quartz-Alkali-Plagioclase plot. The Noble county samples were predominantly syenogranites with minor monzogranite and quartz syenite. The Coshocton county samples were more mafic falling into the tonalite, quartz gabbro/anorthosite, and diorite/anorthosite fields. The responses of a suite of geophysical well logs from both wells were compared to the geochemical data in order to determine whether or not the tool response could identify the different crystalline rocks. Gammaray, bulk density, and photoelectric logs were used due to their distinctive responses in sedimentary rocks. Mann-Whitney nonparametric comparisons of well responses showed that the gamma-ray and bulk density responses could delineate lithologies whereas the photoelectric log values could not.

Committee: Daniel Hembree (Advisor); Katherine Fornash (Committee Member); Keith Milam (Committee Member) Subjects: Geochemistry; Geological; Geology; Geophysical; Geophysics; Mineralogy; Petroleum Geology; Petroleum Production; Petrology

Master of Science, Miami University, 2020, Geology and Environmental Earth Science

Apatite group minerals are ubiquitous in crustal carbonatites and can accommodate many elements useful for assessing the chemical provenance of these rocks. Apatite from c. 65 crustal carbonatite occurrences in Ontario, Quebec and New York were analyzed using single crystal X-ray diffraction (SCXRD) to determine the column anion composition (via structure and site occupancy refinement) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to assess the trace element composition. Four trends of crustal carbonatites are apparent (Bancroft, Frontenac, Lowlands and Highlands). Most crustal carbonatite apatite is hydroxyl-rich fluorapatite of the approximate composition c. 60:40 F:OH, although chlorapatite and hydroxylapatite also occur. Apatite from the Bancroft and Highlands trends is generally less enriched in Mg and Cl but more enriched in Fe, Mn, As, U, Th and REE than apatite from the Frontenac and Lowlands trends, which commonly contains Cl to c. 10% column anion site occupancy. Plots of 1/δSr vs 1/δEu suggest evolution towards larger Sr/Eu anomalies and higher U/Th/REE concentrations possibly resulting from lower degrees of crust partial melting during the Ottawan-Rigolet transition, whereas no geographic trend in U/Th/REE concentrations and Sr/Eu anomalies is observed in Frontenac and Lowlands samples. No correlations to wall rock chemistry were observed.

Committee: John Rakovan (Advisor); Claire McLeod (Committee Member); Mark Krekeler (Committee Member) Subjects: Geology; Mineralogy; Petrology

Master of Science, The Ohio State University, 2020, Earth Sciences

The depth of magma storage beneath volcanoes has been a primary focus of recent geophysical and petrological research. Investigation of magma plumbing systems has important implications for volcanic hazard mitigation and eruption forecasting, and also for our understanding of the origin and evolution of magmas. This work is particularly important at mid-ocean ridges, as they are responsible for the formation of the majority of Earth's crust. Previous petrologic studies of mid-ocean ridges have suggested that olivine-plagioclase-clinopyroxene-liquid cotectic crystallization begins at mantle depths, which has far-reaching implications for our understanding of the mechanisms for crustal accretion. We demonstrate a procedure for processing pressure results using the Kelley & Barton (2008) geobarometer, which significantly changes the interpretation of these results. This process allows for high-resolution interpretation of the pressures, and thus depths, of partial crystallization in mafic systems. Application of this approach to data from the Juan de Fuca Ridge suggests that olivine-plagioclase-clinopyroxene-liquid cotectic crystallization occurs within the crust, and not in the mantle as suggested previously. The results suggest that partial crystallization along the ridge is polybaric. In the southern portion of the ridge, seismically imaged melt lenses are within range of the calculated pressures, however, the average pressures suggest that the majority of olivine-plagioclase-clinopyroxene-liquid cotectic crystallization occurs at greater depths than the imaged melt lenses. This suggests multi-depth magma storage along much of the Juan de Fuca Ridge, with only the shallowest magma reservoirs being imaged by seismic studies.

Committee: Michael Barton (Advisor); Daniel Kelley (Committee Member); Thomas Darrah (Committee Member); Elizabeth Griffith (Committee Member) Subjects: Geology; Petrology

Doctor of Philosophy, Case Western Reserve University, 2020, Geological Sciences

Silicate and carbonate melts in the Earth's mantle play a crucial role in the chemical differentiation and heat transfer of the planet, and are largely responsible for the mantle heterogeneities observed geochemically and geophysically. In order to better model mantle melting, magma differentiation and solidification, and to understand the stability, transport of mantle melts and their effects on seismic observations, the knowledge of the physical properties (e.g., sound velocity, density) and equation of state (EOS) of melts are essential. However, the sound velocity and density of melts relevant to mantle processes are still poorly constrained due to experimental challenges to measure these properties of melts at extreme conditions. In this dissertation, I have studied the EOS of silicate and carbonate melts at high pressure and temperature conditions, with a focus on Mg, Fe and Na-rich silicate melts as well as pure carbonate melts, by developing new techniques for high-pressure sound velocity and density measurements on melts, including the in-situ ultrasonic technique and high-pressure X-ray microtomography. Various high-pressure cell designs combined with synchrotron techniques allow us to obtain the first high-pressure sound velocity dataset for silicate melts in the diopside (CaMgSi2O6)-hedenbergite (CaFeSi2O6) join (Chapters II and IV), and for carbonate melts in the MgCO3-CaCO3 join (Chapter VI). The differences of the elastic properties between silicate glasses and their corresponding liquids are revealed (Chapter III). New high-pressure density data using X-ray microtomographic reconstruction for sodium-rich jadeite melt are also reported (Chapter V). The results of these studies have significant implications for several geophysical problems, including the stability and possible density crossover of melts in the Earth's mantle, the origin of the seismic low-velocity regions in the mantle, the solidification of early magma oceans, and the fate of subducte (open full item for complete abstract)

Committee: Zhicheng Jing (Advisor); James Van Orman (Advisor); Steven Hauck II (Committee Member); Ralph Harvey (Committee Member); Daniel Lacks (Committee Member) Subjects: Earth; Geology; Geophysics; Mineralogy; Petrology

Master of Science (MS), Bowling Green State University, 2018, Geology

The southernmost volcanoes on Earth, Mt. Early and Sheridan Bluff, are two basaltic monogenetic volcanoes located 87°S at the head of the Scott Glacier, in the southern Transantarctic Mountains. The Early Miocene volcanoes lie ~1000 km from any other volcano and ~200 km from the shoulder of the West Antarctic Rift System (WARS), which is the foci of most Cenozoic alkaline volcanism in Antarctica. WARS is part of a larger diffuse alkaline magmatic province (DAMP) including volcanism in New Zealand and Australia. Dating by the 40Ar/39Ar method indicates that Mt. Early is older than previously determined and closer in age to Sheridan Bluff (~19 Ma). Basalts range in composition from alkaline (~6 wt. % Ne-normative) to subalkaline tholeiite (~6 wt. % Hy-normative). Tholeiite have higher ratios of Zr/Nb (9) than alkaline basalts (4) and have lower ratios of La/Yb (5), La/Lu (<50), and Gd/Yb (2) than alkaline basalts (20, 100-150, and ~3 respectively). Fractional crystallization, assimilation-fractional crystallization (AFC), and partial melting are tested as mechanisms to explain compositional variations. Crystal fractionation alone cannot explain the difference in composition. Modelling AFC on plots of Rb, Ba, and La/Nd versus TiO2 show that unrealistic bulk partition coefficients are required to explain the array of compositions using contaminates from the upper crust. I conclude that the coexistence of tholeiite and alkaline basalt is likely due to different degrees of partial melting. The basalts mirror partial melting trends for a common garnet lherzolite source on plots of La/Lu versus Nb/Yb. These models also suggest that tholeiite was produced by higher degrees of melting at shallower depths. Mt. Early and Sheridan Bluff basalt, especially tholeiite, are distinctive from DAMP basalt, having lower Ce/Pb (≤ 20), Gd/Yb (≤ 3) and lack K and Pb anomalies on normalized multi-element plots. Negative K anomalies are a prominent feature of DAMP basalt and are used to (open full item for complete abstract)

Committee: Kurt Panter Dr. (Advisor); Peter Gorsevski Dr. (Committee Member); Daniel Kelley Dr. (Committee Member) Subjects: Geochemistry; Geology; Petrology

Bachelor of Science (BS), Ohio University, 2018, Geological Sciences

Augustine Volcano, located in southern Alaska, has erupted a wide compositional variety of volcanic rocks over its ~26,000 year lifespan. We performed an investigation of the mineralogy and petrology of the low-K dacite (LKD), the oldest yet-unstudied unit in the Augustine tephrostratigraphic succession, with the goal of creating a hypothesis of how the unit formed, as well as finding the unit's relationship to other ancient Augustine tephras. Our work was based on examination of hand samples, grain mounts, and thin sections of the LKD, the latter examined with both petrographic microscopes and with the electron microprobe at the American Museum of Natural History. We found a mineral assemblage in the LKD including plagioclase, calcic amphiboles, cummingtonite, magnetite, and ilmenite. Modeled values for the temperature, pressure, oxygen fugacity, and water content of the LKD's parent melt led us to the conclusion that the unit was derived from mixing of a rhyolitic parent magma similar to that of the ~30 m thick rhyolite erupted by Augustine in the Pleistocene, together with deeply-sourced mafic material of a similar geochemical character to the mafic component of the high-P dacite hypothesized by other research. Further work is needed to fully characterize this unit, as well as those above it in the Augustine tephrostratigraphic column, in order to arrive at a complete understanding of the relationship between ancient and modern Augustine tephras.

Committee: Patricia Nadeau Dr. (Advisor); Keith Milam Dr. (Committee Member); Alycia Stigall Dr. (Committee Member) Subjects: Earth; Geological; Geology; Mineralogy; Petrology

Master of Science, Miami University, 2017, Geology and Environmental Earth Science

New knowledge regarding epithermal gold from Round Mountain Gold Mine (RMGM) aims to add to what is known about gold mineralization and ore formation. The Type 4 gold ore at RMGM is unusual in that it contains both disseminated gold (nm-µm) and macrocrystalline gold. Unmodified samples of macrocrystalline gold and disseminated gold within bulk ore were acquired from the Type 4 and determined to be texturally and mineralogically distinct. Detailed investigation using field emission scanning electron microscopy (FESEM), coupled with energy dispersive x-ray spectroscopy (EDXS), concluded that gold mineralization began as two-dimensional nucleation following nanoparticle aggregation. The dominant mechanism for mineralization then shifted to adhesive growth, as gold in solution reached levels greater than supersaturation. Results further indicate that two distinct sequences for gold mineralization occurred where only macrocrystalline gold contained paragenetic apatite, goethite, and gold telluride, and pyrite and chlorite were associated strictly with bulk ore. Several of these minerals, especially pyrite, goethite, and chlorite may have significant implications for extraction efficiency using conventional cyanide heap leach. U-Pb dating of apatite was also conducted in attempts to further constrain the deposit's complex mineralization history, but was found to be inaccurate in determining an age date due to insufficient samples.

Committee: Mark P.S. Krekeler (Advisor); John Rakovan (Committee Member); Claire McLeod (Committee Member) Subjects: Earth; Geochemistry; Geology; Mineralogy; Mining; Petrology