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 15 of 15 for “"Isotope variations"”.
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Spatially controlled Fe isotope variations at Torres Del Paine
… trends of changing non-traditional stable isotope ratios in igneous rocks with differentiation index. We present new Fe isotope data for the Torres del Paine igneous complex in southern Chile. The multi-composition pluton consists of a 1.5 km vertical exposure of homogenous granite …
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Petrogenesis of natrocarbonatite at Ol Doinyo Lengai, East Africa—evidence from Fe and U isotope variations
… remains unresolved. We carried out Fe and U isotope analyses among a variety of ODL samples. Our sample set includes natrocarbonatite that erupted in 2005, 2 comingled tephras (mixture of natrocarbonatite and nephelinite) and a sequence of 8 nephelinite tephras that erupted in 2007-2008; as …
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B isotope variations at variable scales in arc volcanoes: a case study of lavas from Paniri and Toconce, Northern Chile
… mantle wedge at subduction zones. The boron isotope composition of magmas is useful in detecting and quantifying the exchange process between the slab and the mantle. This is due to the large boron isotopic difference between the subducting altered oceanic crust and the mantle, and boron …
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Trace Elements and Sulfur Isotope Variations in Endowed and Non-Endowed Porphyry Systems of the Dawson Range Mineral Belt, Yukon Territory
… focusing on select trace elements and sulfur isotope analyses to distinguish between endowed deposits and non-endowed occurrences. The remote location, poor access, and extensive glacial deposits complicate exploration efforts. The study analyzed fifty-six samples from eight porphyry systems, …
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Late Holocene Climatic Change: The little ice age and El Nino from planktonic foraminifera in sediments off walvis bay, South West Africa
… similar research, using species and oxygen isotope variations has been completed in similar sediment off northern Venezuela and in the Santa Barbara Basin (Kipp and Towner 1975, Dunbar 1983), these are the first downcore foraminiferal species records of the South West African deposit. The …
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The potential for using stable isotopes for solving urban geohydrological problems in the Cape Town area
… investigates the potential for using the stable isotopes of hydrogen and oxygen from surface water and shallow aquifer water in solving urban geohydrological problems in the Cape Town metropolitan region. Three different water groups were chosen for detailed analysis, namely groundwater, …
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The chlorine isotope composition of chondrites : evidence for a single nebular reservoir and the effects of secondary processes on chondrite parent bodies
The chlorine isotope composition of chondrites provides information about isotopic reservoirs that were present in the solar nebula and the effect of secondary processes on the isotopic composition. We analyzed twenty chondrites that included both unaltered (type 3) and altered (types 1-2, 4-6) …
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U-Pb geochronology and structural geology across major shear zones of the Southern granulite terrain of India and organic carbon isotope stratigraphy of the Gondwana coal basins of India : their implications for Gondwana studies
… (Chapter 6) tests the use of organic carbon isotopes as a chemostratigraphic tool to correlate between the lower part of terrestrial Gondwana (Upper Carboniferous to Triassic) sequences in India. This work contributes to (i) intra-basinal and inter-basinal stratigraphic correlation and carbon …
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The marine biogeochemistry of chromium isotopes
… general has been identified as a significant Cr isotope fractionation mechanism. This thesis presents the first Cr isotope variations (d53Cr) in ODZs of the ocean and adds to the sparse Cr isotope data published for modern seawater. I developed a precise and accurate Cr isotope method for …
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Recent extreme events in a tropical stalagmite: Multi-proxy records and analysis of ecosystem delta carbon-13 value sensitivity to weak climate forcing
… a weekly-monthly record of stalagmite stable isotope ratios showed low stable oxygen isotope excursions that corresponded to the historical record of tropical storm strikes in the region. Furthermore, excursion amplitude was related to the maximum intensity of storms prior to landfall. The …
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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)
… 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 silicaundersaturated and oversaturated magmas evolve from the same mantle-derived, …
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The marine biogeochemistry of chromium isotopes
… general has been identified as a significant Cr isotope fractionation mechanism. This thesis presents the first Cr isotope variations (653 Cr) in ODZs of the ocean and adds to the sparse Cr isotope data published for modern seawater. I developed a precise and accurate Cr isotope method for …
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Physical and geochemical response in cave drip waters to recent drought, central Texas, USA : implications for drought reconstruction using speleothems
… dripwater Mg/Ca, Sr/Ca, and Ba/Ca ratios, Sr isotope values, Ca concentrations, and oxygen isotope values. This lack of response indicates limited water-rock interaction (WRI) and/or prior calcite precipitation (PCP) affects these dripwaters. Intermediate drip sites exhibit the greatest …
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Groundwater of the North-Western Kalahari, Namibia
… recharge could be demonstrated by stable isotope variations resulting from observed flood events. Within the Kalahari basin several troughs were identified in the pre-Kalahari surface by GIS-based analyses. A map of saturated thickness of Kalahari sediments revealed that these major …
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Characterisation of ocean island basalt sources : St. Helena
… is developed to illustrate temporal geochemical variations over 2 Ma of subaerial activity. This is accomplished in conjunction with a detailed field study of the SHRS by Baker(1968) which is shown to be largely accurate. It is demonstrated that ascending magma batches are substantially modified …