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Articles 1 - 12 of 12
Full-Text Articles in Geochemistry
Diatom Productivity And Nutrient Dynamics In The Ross Sea, Antarctica During Warm Events In The Neogene, Marialena Christopoulou
Diatom Productivity And Nutrient Dynamics In The Ross Sea, Antarctica During Warm Events In The Neogene, Marialena Christopoulou
Graduate Research Theses & Dissertations
Increased melting of the Antarctic Ice Sheet (AIS) in recent decades, has had a significant impact on many aspects of the global ocean. Models indicate that by the end of the 21st century atmospheric carbon dioxide (CO2) concentrations may exceed 500 ppm, and the average global temperature will likely warm by more than 2°C. However, data that provide model constraints on potential feedbacks in ice-ocean-atmosphere system are limited by short-timescales (e.g., decadal- to centennial-scale) and incomplete spatial coverage. In particular, little is known about the impacts of future warming and widespread melting of AIS on marine biological productivity, silicate weathering …
Vanadium Partitioning Between Magnetite, Hematite, And A Hydrothermal Fluid: Implications For Iocg And Ioa Deposits, Jeremy Raymond Nederbo
Vanadium Partitioning Between Magnetite, Hematite, And A Hydrothermal Fluid: Implications For Iocg And Ioa Deposits, Jeremy Raymond Nederbo
Graduate Research Theses & Dissertations
Iron oxide-copper-gold (IOCG) and iron oxide-apatite (IOA) deposits are major sources of iron contained within magnetite and/or hematite as well as copper contained within copper-iron sulfides and gold as a native metal. Their formations have been attributed to magmatic, hydrothermal, or a mixture of magmatic-hydrothermal processes. Vanadium can readily substitute into magnetite via ion exchange due to similar atomic radii and charges as iron and has thus been hypothesized to be an effective tracer of hydrothermal or magmatic inputs. To evaluate the mobility of vanadium in a magnetite-hematite-fluid system, experiments on the partitioning of vanadium between magnetite, hematite and a …
Late Holocene Terrestrial Hydroclimate Reconstructions From Central And South American Sites, Brittany N. Price
Late Holocene Terrestrial Hydroclimate Reconstructions From Central And South American Sites, Brittany N. Price
Graduate Research Theses & Dissertations
Terrestrial records of hydroclimate variability from Central and South America were developed to better constrain previously unknown regional responses to a range of hydroclimate drivers in the recent past. Developing these late Holocene terrestrial hydroclimate records improves our understanding of past hydroclimate variability by increasing temporal resolution and allows us to further understand complexities in spatial dynamics of the climate system. From South-Central Chile, a geomorphic analysis of landforms emplaced in a glacial valley indicated a positive glacial mass balance in the recent past. A high-precision chlorine-36 chronology was developed from basaltic boulders, with additional minimum constraining ages from Araucaria …
Evaluating Holocene Precipitation Variability In The Baltic Region Using Oxygen Isotopes Of Lacustrine Carbonate From Estonia, Maxwell Gordon Boes
Evaluating Holocene Precipitation Variability In The Baltic Region Using Oxygen Isotopes Of Lacustrine Carbonate From Estonia, Maxwell Gordon Boes
Graduate Research Theses & Dissertations
A high-resolution Holocene record of groundwater isotopic composition from eastern Europe enhances the current understanding of ocean atmosphere interactions and moisture transport dynamics. In the modern system, it has been established that the amount of regional winter precipitation is driven by the strength and direction of the sea level atmospheric pressure gradient over the Atlantic Ocean. This is defined by the North Atlantic Oscillation (NAO) index, that shows a positive correlation with precipitation amount during the cold season. This study aims to discover the link between atmospheric dynamics and the ratio of warm season to cold season precipitation through the …
Impact Of Prairie Restoration On Geochemistry And Microbial Communities In Groundwater, Kayla Koenig
Impact Of Prairie Restoration On Geochemistry And Microbial Communities In Groundwater, Kayla Koenig
Graduate Research Theses & Dissertations
Prairie restoration is important for reversing the loss of biodiversity and repairing ecosystem functions humanity is dependent on diverse ecosystems. This study looks at the impact of the beginning phases of prairie restoration on groundwater geochemistry and microbial communities the relationship between them. This research project studied the geochemistry and microbial communities in five wells before, during, and after the beginning phases of the first year of a prairie restoration on the Northern Illinois University campus. Water samples were collected bimonthly for a year and analyzed on an Ion Chromatograph. Microbial samples were collected monthly and underwent DNA extraction, amplification, …
Miocene-Pleistocene Diatom Oxygen Isotope And Biogenic Silica Record From Iodp Site U1523, Ross Sea, Antarctica, Donald James Mclennan
Miocene-Pleistocene Diatom Oxygen Isotope And Biogenic Silica Record From Iodp Site U1523, Ross Sea, Antarctica, Donald James Mclennan
Graduate Research Theses & Dissertations
The West Antarctic Ice Sheet (WAIS) plays a significant role in Earth’s climate. WAIS is currently retreating due to changes in wind-driven oceanic currents resulting in an increasing flux of warm waters to ice margins. Brine rejection in the Ross Sea is also major source of High Salinity Shelf water (HSSW) and Antarctica Bottom Waters (AABW), which creates a stratified ocean and plays a significant role in regulating Earth’s climate. Currently, there are very limited proxies that can quantify the variable input of HSSW formation on geologic time scales. Here we provide a 18Odiatom and biogenic silica (BSi) record which …
Alteration Reactions In A Hornblende-Biotite-Anthophyllite-Fluid System: Implications For Cu-Au Ore Deposits, James Mitchell Lightner
Alteration Reactions In A Hornblende-Biotite-Anthophyllite-Fluid System: Implications For Cu-Au Ore Deposits, James Mitchell Lightner
Graduate Research Theses & Dissertations
High-grade porphyry Cu-Au ore deposits are typically contained in the potassic alteration zone, which forms through the alteration of preexisting country rock by a magmatic volatile phase (MVP) exsolved from an igneous intrusion. The MVP is a H2O dominant phase that contains high concentrations of NaCl, KCl, FeCl2, HCl, sulfur (as H2S or SO2) and minor concentrations of metals. The minerals in the potassic alteration zone are predominantly K-feldspar and biotite with a shreddy texture. Shreddy biotite forms from the replacement of prismatic-tabular shaped hornblende crystals, resulting in a characteristic shreddy texture. The alteration of hornblende to biotite can neutralize …
Cobalt Partitioning And Solubility In Low-Temperature Carbonate-Hydrothermal Systems, Seth Kurtis Coursey
Cobalt Partitioning And Solubility In Low-Temperature Carbonate-Hydrothermal Systems, Seth Kurtis Coursey
Graduate Research Theses & Dissertations
Cobalt mineralization has been documented in low temperature Mississippi Valley-type (MVT) deposits in southeast Missouri. Lead and zinc are the most economically important metals in these deposits and are contained within galena (PbS) and sphalerite (ZnS), respectively. Cobalt is also mined in some of the deposits with cobalt-bearing ores, e.g., siegenite ((Ni,Co)3S4) and fletcherite (Cu,(Ni,Co)2S4), occurring stratigraphically below main-stage galena and sphalerite. The hydrothermal fluids responsible for cobalt mineralization are thought to be chemically distinct from the predominant MVT ore-bearing fluids and represent a distinct mineralizing event. Cobalt is likely transported as CoCl2 in hydrothermal fluids and sourced from structures …
Model-Based Estimates Of The Timing Of Brine Flux Into The Victoria Land Basin From The Mcmurdo Dry Valleys, Antarctica, Valerie Nicole Voisin
Model-Based Estimates Of The Timing Of Brine Flux Into The Victoria Land Basin From The Mcmurdo Dry Valleys, Antarctica, Valerie Nicole Voisin
Graduate Research Theses & Dissertations
Submarine groundwater discharge (SGD) at a continental scale is one of the least constrained components of the hydrologic cycle and may represent a significant flux of iron and silica waters to the global ocean. Quantifying SGD along the Antarctic margin is complicated by complex subglacial and subsurface hydrogeology and limited observational data. Airborne transient electromagnetic (AEM) surveys have identified extensive high-salinity subsurface brines in the McMurdo Dry Valleys (MDV) that are hydrologically connected to surface features in the MDV (e.g. Taylor Glacier, saline lakes) and are potentially a significant source of SGD to McMurdo Sound. A 2D numerical model was …
Copper And Gold In Vapors And Liquids As A Function Of Hcl At 700°C And 100 Mpa, Corrie A. Lucchesi
Copper And Gold In Vapors And Liquids As A Function Of Hcl At 700°C And 100 Mpa, Corrie A. Lucchesi
Graduate Research Theses & Dissertations
Porphyry ore deposits are major sources of copper (Cu) and gold (Au) and form when a magmatic volatile phase (MVP) exsolves from a porphyritic intermediate to felsic melt and transports metals to surrounding country rock where they precipitate in an ore zone. There is a consensus that the chloride concentration of the MVP has a direct relationship to the concentration of Cu and Au in the MVP, but the role of dissolved HCl on Cu and Au concentrations has not been addressed. It is hypothesized that increasing HCl concentrations in the MVP will result in higher concentrations of Cu and …
The Petrogenesis Of The No Agua High-Silica Rhyolite In The Taos Plateau Volcanic Field, Northern New Mexico, Kevin M. Voelz
The Petrogenesis Of The No Agua High-Silica Rhyolite In The Taos Plateau Volcanic Field, Northern New Mexico, Kevin M. Voelz
Graduate Research Theses & Dissertations
The Taos Plateau volcanic field (TPVF) is located in Northern New Mexico between the eastern flanks of the Tusas Mountains and west of the Sangre de Cristo range. The TPVF is dominantly composed of basaltic lava flows, olivine andesites, and two-pyroxene dacites which erupted from 5.88 to 1.03 Ma. The variety of compositions within the field owes its origin to processes such as magma mixing, fractional crystallization, and crustal assimilation based on chemical modeling. Curiously placed within this spectrum of mafic to intermediate lavas exists the singular high-silica rhyolite of the No Agua Peaks. XRF and ICP-MS analyses from this …
Occupational Seasonality And Paleoenvironmental Reconstruction At Quebrada Jaguay 280, Stephanie Melissa Gruver
Occupational Seasonality And Paleoenvironmental Reconstruction At Quebrada Jaguay 280, Stephanie Melissa Gruver
Graduate Research Theses & Dissertations
Quebrada Jaguay 280 (QJ-280) is one of the oldest maritime archaeological sites in the New World. Previous excavations of the southern Peruvian coastal site have dated occupation from ~13,000-8,000 cal yr BP. These excavations also determined that the occupants of the site used preferential maritime resource procurement strategies and had an interzonal connection to the highlands. In 2017 a new excavation was conducted at QJ-280 and the remains of the marine mollusk Mesodesma donacium were recovered. Geochemical examinations on the shell remains informed on the occupational seasonality of the site and reconstructed sea surface temperatures experienced off the coast of …