Global ETD Search
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Showing 1 to 20 of 28 for “"Nd isotope"”.
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An isotope study of the felsic units of the Bushveld Large Igneous Province, South Africa
An O, H, Sr and Nd isotope study was carried out on the ~ 2059 Ma Bushveld granites and granophyres. A small number of Rooiberg Group felsites were also studied.
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The isotopic evolution of the British lithosphere
A Sm-Nd mineral isochron obtained from an olivine gabbro yields an age of 375 +/- 34 Ma (M.S.W.D. = 0.006) and represents the formation age of the Lizard Igneous Complex. Two magmatic suites are recorded in the complex, an early trace element enriched (ENd<sub>375</sub> = + 8.9 - + 10.1) and a late …
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Isotope shift spectroscopy of ions in cryogenically cooled neutral plasmas
This thesis describes precision measurements of isotope shifts of Nd+ ions using a novel cryogenic ion source. Isotope shift measurements are useful in searching for a hypothetical light boson that couples with electrons and neutrons, and which could be the long-sought-after dark matter particle. …
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Sm-Nd and C-isotope chemostratigraphy of Ordovician epeiric sea carbonates, midcontinent of North America
Interpreting and correlating epeiric sea sequences is key to understanding ancient marine environments. As a result, eNd, d13C and Sm/Nd profiles are developed as tools for interpreting epeiric sea carbonates. Previously, eNd and d13C profiles in epeiric sea carbonates have been used to study …
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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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Tectonic implications of mantle source changes recorded by Eocene-Oligocene basalts from the Dillon volcanic field southwest Montana (USA)
… tectonics, within the northern Rocky Mountains and accordingly, also present across the North American Cordillera. The Dillon volcanic field is composed of lavas and intrusives that crop out across southwestern Montana, but most prominently in the Gravelly Range, where they define multiple …
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Sediment incorporation into continental arc systems and paleogeography of the western North American Cordillera: Insights from the North Cascades, Washington
… arc systems provide evidence for the vertical and horizontal transfer of upper crustal rocks into arcs within convergent-margin settings. These incorporated sediments are proposed to play a significant role in the evolution of the arc by potentially triggering high-flux magmatism and driving …
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Geochemistry, Thermochronometry, Petrogenesis, and Geometry of Igneous Dikes in Central Arkansas: Implications for Mississippi Embayment Evolution
… the Cambrian Mississippi Valley Graben (MVG) and serves as a natural laboratory for extensional tectonics. The Arkansas Alkaline Province (AAP) lies along the ME’s western border in central Arkansas and was emplaced in the mid-Cretaceous Period as a suite of intrusive bodies. The relationship …
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Provenance of Eastern Magallanes Foreland Basin Sediments: Mineralogical and Geochemical Analyses Reveal Paleogene Tectonic Unroofing of the Fuegian andes
<p>Though southern South America and the Antarctic Peninsula were previously connected through a Paleozoic-Mesozoic subduction system on the western margin of Gondwana, this connection was tectonically disrupted in the Cenozoic by forming the Drake Passage in the Scotia Sea. Heavy mineral …
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Geodynamic Development of the South China Block from Precambrian to Cretaceous: Constraints from Geology Geochemistry and Geochronology
… block is subject to debate. Most articles tend to subdivide the South China block into two sub-ordinate blocks (Yangtze and Cathaysia), with a central Sibao (Jiangnan) Orogen, although there are also suggestions for a separate eastern (Tolo) block. Debate primarily occurs around the timing of …
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Oxygen and radiogenic isotope constraints on the generation of coexisting silica-undersaturated and oversaturated felsic magmas of the Ditrau Alkaline Massif (Romania)
… the relationship between the silica-undersaturated and oversaturated Ditrău rocks based on oxygen, Sr, Nd and Pb isotope data. Different models have been proposed previously to explain the coexisting silica-undersaturated and oversaturated rocks in general: (1) both …
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Archean continental crust formation and the rise of atmospheric oxygen
… the establishment of the continental crust and the progressive rise of an oxygenated atmosphere. The volume of continental crust on the earliest Earth is a critical parameter for constraining the chemical evolution of major terrestrial reservoirs, and radiogenic isotope signatures document …
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Origin and evolution of parental magmas associated with Pliocene-Quaternary low-silica volcanism within the Altiplano-Puna Volcanic Complex of northern Chile
The Andean continental arc is built upon the thickest crust on Earth, whose eruption products reflect varying degrees of crustal assimilation. Physical interactions between mafic and felsic magmas for this arc are therefore difficult to recognize due to the differentiation of mantle-derived magma …
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Compositional Analysis of the Martian Meteorites Northwest Africa 6342 and Northwest Africa 10961
The most abundant type of meteorite that we have from Mars is the shergottite. This makes the study of shergottite samples invaluable to understanding the geological evolution of that planet. Electron microprobe analyses, bulk elemental composition calculation, and laser ablation-inductively …
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Using Nd Isotopes to understand changes in continental weathering flux in Mid-Pennsylvanian (Desmoinesian) carbonate cycles
… of study on Phanerozoic sedimentary deposits indicates that changes in Earth's orbital parameters are one of the main drivers of climate change on the 104-105 yr time scales, however understanding the relationships between climate change on coeval marine and continental deposits is difficult …
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Micro-geochemistry of the mantle and its volcanic rocks
… utilise detailed micro-sampling techniques to understand the effects of melt infiltration in the continental lithosphere and the relationship of deeply derived kimberlite melts to lithospheric processes. To be able to make these links it is necessary to better constrain the geochemical …
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Tectonic, magmatic and metallogenic evolution of the Cajamarca mining district, Northern Peru
… had a close association with orogenic episodes and high plate convergence rates. New 40Ar/39Ar dates show magmatism in the region had commenced by late Palaeocene times, some 15 m.y. earlier than suggested by previous geochronological studies. Palaeogene (57-43 Ma) intrusive and volcanic rocks …
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Igneous and metamorphic processes in the Shap Granite and its aureole
… Granite outcrops in eastern Cumbria, N.W. England and is a post—orogenic granite intruded during the Lower Devonian (ie 394 Ma) into rocks of Ordovician to Siturian age. It is of adamellite composition and is notable in having megacrysts of orthoclase which crystallised late (relative to the …
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Petrology and geochemistry of Sangeang Api and recent volcanism in the Sumbawa-Flores sector of the Sunda Arc: the response of along-arc geochemistry to subduction processes.
… data from an active volcano (Sangeang Api) and previously unstudied, extinct volcanoes (Wai Sano and Doro Kota and Doro Kuta) from adjacent sectors of the eastern Sunda Arc, Indonesia. Sangeang Api erupts co-magmatic suites of lavas and cumulate xenoliths. Lavas are ne-normative, …
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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
This is a study of Phanerozoic carbonatites and related alkaline silicate rocks from Zandkopsdrift in Namaqualand, South Africa (55 Ma), and Marinkas Quellen (529 Ma), and Dicker Willem (49 Ma) in southern Namibia, all emplaced within the Proterozoic Namaqua Natal province. The aims of this thesis …
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