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 17 of 17 for “"radiogenic isotopes"”.
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The genesis of ‘giant’ copper-zinc-gold-silver volcanogenic massive sulphide deposits at Tambogrande, Perú : age, tectonic setting, paleomorphology, lithogeochemistry, and radiogenic isotopes
… of sulphide deposition. Geochemical and radiogenic isotope data indicate that the rhyolites in the VMS deposits were high temperature partial melts of the juvenile arc crust that had inherited the isotopic signatures of continental crust. Moreover, Pb isotope data suggest the metal budget …
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Potassium-Argon Dating
… radioactive isotope K40 decays to the stable radiogenic isotopes A40 and Ca40. The rate of decay is a constant ratio, called the branching ratio, and is used to determine the age of a mineral. Because potassium exists almost everywhere this gives us a valuable method for dating rocks. The …
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Does the theory of parameterized conveciton apply to layered mantle convection?
… for the case of layered convection with a radiogenically enriched lower mantle. I modified the finite-element code ConMan to include exponentially decaying internal heating so that the radiogenic isotopes in the lower layer would be accurately represented, and compared the experimental …
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Understanding Non-Plume Related Intraplate Volcanism
… ages along with new geochemical data, and radiogenic isotopes that constrain the melting conditions and the timing of emplacement. Modeling of the melting conditions suggests that melting occurred under conditions slightly higher than average mantle beneath mid-ocean ridges. Asthenosphere …
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Supercontinental Inheritance and its Influence on Supercontinental Breakup: The Central Atlantic Magmatic Province and the Breakup of Pangea
… Pangea. Major and trace element data, Sr-Nd-Pb radiogenic isotopes, and high-precision olivine chemistry were collected on primitive CAMP dikes from Virginia (VA). These new samples were used in conjunction with a global CAMP data set to elucidate different mechanisms for supercontinent breakup …
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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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Geochemical Implications of Stirring and Mixing in the Earth's Mantle
Measurements of radiogenic isotopes can in principle constrain the melting, melt migration, and solid state convection that occurs in the Earth's mantle, but to do so requires suitable quantitative models. A new statistical model is introduced to better understand the observed heterogeneity in …
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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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Geochemical Analysis of Mississippian Cherts and Devonian-Mississippian Novaculites, Southern Midcontinent Region
<p>This study uses trace elements and radiogenic isotopes (Pb, Sr, and Nd) to investigate the origin and mode of formation for the siliceous deposits in the Lower Mississippian Boone Formation and the Devonian-Mississippian Arkansas Novaculite in the southern midcontinent. Mississippi Valley-type …
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Basalt Magmatism as a Key to Unlocking Cenozoic Dynamic Topography
… and rare earth elements, as well as selected radiogenic isotopes. Geochemical concentrations are corrected to approximate primary melt compositions. A suite of complementary geophysical and geomorphic techniques are used to estimate the amplitude, wavelength and depth of mantle thermal …
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The hydrochemical and isotopic characterization of groundwater in southern Mozambique
… two labs at Stellenbosch University, and stable isotopes of oxygen and hydrogen, and radiogenic isotopes of strontium were analyzed at the Department of Geological Sciences at the University of Cape Town. The aim of this study was to characterize the isotopic and hydrochemical composition of …
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Geochemical and isotopic constraints on the source regions of phanerozoic carbonatites and associated alkaline rocks from the Zandkopsdrift complex of Namaqualand, South Africa, and the Marinkas Quellen, and Dicker Willem complexes in Namibia
… and associated igneous rock samples contain unradiogenic Sr and mildly radiogenic Nd isotope compositions below and above Bulk Earth/CHUR values respectively. This suggests that carbonatite magmas were generated from sources with long-lived Rb/Sr lower than, and Sm/Nd higher than, the primitive …
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The isotope geochemistry of abyssal peridotites and related rocks
… geologic techniques, principally major elements, radiogenic isotopes and trace elements, but including petrography, mineral chemistry, x-ray diffraction, seafloor geomorphology, and analysis of the tectonics of fracture zones. The first chapter is an introduction to the problems to be addressed in …
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A heavy stable isotope approach to tracing mantle source and process
… part of this variability. Recently, heavy stable isotopes have been suggested as a new tool to complement existing tracers of mantle heterogeneity and lithology (e.g., major and trace elements, radiogenic isotopes), because mineral- and redox-specific equilibrium stable isotope fractionation …
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Mineralogical, Chemical, and Isotopic (Sr, Pb) Composition of Atmospheric Mineral Dusts in an Ombrotrophic Peat Bog, Southern South America
… mineralogy of atmospheric dust and their radiogenic isotope compositions in the peat, provide important information about the mineralogical host phases of major and trace elements transported through the atmosphere, grain size fractionation during transport, and their possible source areas …
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Paleoceanographic and Paleoclimatic Changes Associated With the Eocene-Oligocene Transition
… patterns associated with the EOT. A pulse of nonradiogenic ε<sub>Nd</sub> at Site 1090 occurs in conjunction with the benthic δ<super>18</super>O increase across Oi-1. A similar relationship at ODP Site 738 from Prydz Bay [Scher et al., 2011] argues for a pulse of eroded sediments …
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Geochemical and fluid dynamic investigations into the nature of chemical heterogeneity in the Earth's mantle
Variations in the abundances of elements and radiogenic isotopes in mantle derived peridotites and volcanic rocks are chemical integrals over time, space, and process, which ultimately contain information about the role of convection in the earth's mantle in creating, maintaining, and destroying …