Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 22 for “"Pb isotopes"”.
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Evolution of anthropogenic Pb and Pb isotopes in the deep North Atlantic Ocean and the Indian Ocean
Pb and Pb isotopes in the ocean have varied on decadal to centennial time scales due to anthropogenic Pb inputs. Thus, tracing the temporal variation of Pb and Pb isotopes in the ocean provides information on the major sources of Pb and the transport of Pb from sources to the ocean surface and into …
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Evolution of Anthropogenic Pb and Pb isotopes in the deep North Atlantic Ocean and the Indian Ocean
Pb and Pb isotopes in the ocean have varied on decadal to centennial time scales due to anthropogenic Pb inputs. Thus, tracing the temporal variation of Pb and Pb isotopes in the ocean provides information on the major sources of Pb and the transport of Pb from sources to the ocean surface and into …
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Source Constraints of Ore Metals in Mississippi Valley-type Deposits in Central and Eastern Tennessee using Pb Isotopes
… same mineralizing fluids and may have different Pb sources. Nu Plasma MC-ICP-MS Pb isotopic analyses on sulfides from Central and East TN were conducted and the metal sources evaluated. Results were plotted on covariation diagrams with respect to the average crustal growth curve from Stacy and …
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Fluid/rock Interaction History of a Faulted Rhyolite-Granite Contact, Eastern Rhine Graben Shoulder, SW-Germany : Alteration Processes Determined by Sr- Pb-Isotopes, Th/U-Disequilibria and Elemental Distributions
… The use of several isotopic systems, Rb/Sr -, U/Pb-isotopes and Th/U disequilibria, reveals a complex history of polyphase fluid/rock interaction following the Permian volcanic extrusion, showing notable disturbances during the late Jurassic hydrothermal activities, the Tertiary rifting of the …
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Lead isotopes as a palaeodietary tracer in southwestern South Africa
This thesis evaluates the utility of lead (Pb) isotopes, in combination with strontium (Sr) isotopes, as a geochemical tracer for studying the palaeodiets and palaeo-landscape usage in southwestern South Africa. Isotopes of light elements, carbon (C), nitrogen (N), oxygen (O), and sulphur (S), are …
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Helium and lead isotope geochemistry of oceanic volcanic rocks from the East Pacific and South Atlantic
… source regions and volcanic magmas. He and Pb isotopes were measured in glassy basalts from young seamounts in the East Pacific, and in phenocrysts and corresponding whole rocks, respectively, from the island of St. Helena. He isotopes were also measured in glassy mid-ocean ridge basalts …
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The Evolution and Impact of Weddell Sea Deep Water
… sediment provenance (detrital radiogenic Nd and Pb isotopes), water mass provenance (authigenic Pb isotopes), and identification of marine forward and reverse silicate weathering processes (dissolved stable Si and radiogenic Sr isotopes, fine grained K’/Ar ages). Overall, the novel findings of …
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Anthropogenic Lead Deposition and Four National Parks in Poland as Determined by Lead Isotope Ratios
… high concentrations of heavy metals, including Pb. Partitioning of metals in geochemical fractions, by sequential chemical extractions, may indicate whether a metal has been recently deposited in the soil. While concentration levels alone cannot distinguish between natural and anthropogenic Pb, …
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Helium and lead isotope geochemistry of oceanic volcanic rocks from the East Pacific and South Atlantic
… source regions and volcanic magmas. He and Pb isotopes were measured in glassy basalts from young seamounts in the East Pacific, and in phenocrysts and corresponding whole rocks, respectively, from the island of st. Helena. He isotopes were also measured in glassy mid-ocean ridge basalts …
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U-Th-Pb fractionation in selected carbonate and silicate systems
V-Th-Pb fractionation trends, and the associated variations in Pb-isotopes, provide important constraints on the nature, and age, of a wide range of geological processes. This thesis presents three detailed case studies from a carbonatite intrusive complex, lower crustal granulite xenoliths, and …
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Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges
… results to model time-dependent uranium-series isotopes do not support the presence of a fixed quantity of garnet pyroxenite in the source of OIB. To use U-series isotopes to further constrain mantle heterogeneity and the timing and nature of melting and melt transport processes, U-Th-Pa-Ra …
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Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges
… results to model time-dependent uranium-series isotopes do not support the presence of a fixed quantity of garnet pyroxenite in the source of OIB. To use U-series isotopes to further constrain mantle heterogeneity and the timing and nature of melting and melt transport processes, U-Th-Pa-Ra …
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The Dynamics of the Late Neogene Antarctic Ice Sheets in the Central Ross Sea using a Multianalytical Approach
… from sixteen different cores were measured for U-Pb isotopes via LA-ICP-MS. Zircon data was compared to neodymium isotope and clast lithology datasets from collaborators. Site U1522 shows three distinct provenance shifts from the late Miocene to the Pleistocene, two of which are coincident with …
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Melting processes in small basaltic systems: the Auckland Volcanic Field, New Zealand
… geochemical dataset of the AVF, including Sr-Nd-Pb isotopes and a subset of U-Th-Ra isotopes. In addition to a whole-field study, two case studies of well-exposed volcanic centres in the AVF are presented: Rangitoto and Motukorea. Major and trace element and isotopic whole rock data are used to …
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Geochemistry of the Northern Izu-Bonin arc: implications for crustal recycling and mantle processes
… HFSEs and fluid-modified strontium isotopes. However, a systematic variation in<br/>isotope and trace element ratios is recognised across the Izu-Bonin arc. Radiogenic 87Sr/86Sr<br/>and 143Nd/144Nd, low Nb/Y and high Ba/La in the volcanic front suggests melting of a …
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Testing the driving mechanisms for exhumation of the Greater Himalayan zone in eastern Bhutan: Implications of split-stream zircon and monazite geochronology
… and the GHZ were analyzed for U–Th–Pb isotopes and trace-element abundances using split-stream laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Cathodoluminescence images of the zircons typically revealed three generations of crystallization: (1) an inherited …
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Characterisation of ocean island basalt sources : St. Helena
… a residual K-rich phase. Combined Sr-Nd-Pb isotope and fractionation corrected trace element data for fresh rocks enable consideration of changing thermal and chemical fluxes impinging on and interacting with the base of the lithosphere over a period of at least 2 Ma. The existence of two …
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The timescales of andesite generation at Mount Ruapehu, New Zealand
… with major and trace elements and Sr, Nd and Pb isotopes for lavas sampled from coherent stratigraphic sequences on Mount Ruapehu. This andesitic volcano lies at the southern end of the Taupo Volcanic Zone (TVZ) in the centre of North Island, New Zealand. Volcanic activity at Ruapehu is …
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Evaluating mantle and crustal processes using isotope geochemistry
… The similar "ages" determined by Re-Os and Sm-Nd isotopes and the high Re/Os ratios in the most fertile peridotites plotting to the right of the geochron, indicate that the mafic layers and the ultramafic rocks are genetically related by a refertilization process which took place ≈ 1 Ga ago. The …
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Classification and petrogenesis of the Tongo dike-01 from the Tongo-Tongoma cluster, Sierra Leone: constraints from bulk rock geochemistry
… major and trace elements as well as Sr-Nd-Pb isotope geochemistry. The primary objectives of this study are: 1) provide detailed petrographic observations of the dike, 2) classify the dike relative to kimberlites worldwide, 3) constrain the geochemical effects of secondary processes on …
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