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 18 of 18 for “"Mid-ocean ridge basalt"”.
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Geochemical heterogeneity in the Hawaiian plume : constraints from Hawaiian volcanoes and Emperor seamounts
… geochemical characteristics are not present in mid-ocean ridge basalt (MORB). Consequently, it is inferred that a common mantle source has been contributing to the Hawaiian-Emperor volcanism for over 80 My, which provides the strongest geochemical argument supporting the plume hypothesis. The …
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Origin of geochemical heterogeneity in the mantle : constraints from volcanism associated with Hawaiian and Kerguelen mantle plumes
… probably related to Southeast Indian Ocean mid-ocean ridge basalt, but possibly intrinsic to the Kerguelen plume, and an enriched Kerguelen plume component. From -34 Ma to <1 Ma, on average the proportion of the depleted component decreased. Subsequently, a second mixing process …
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Interactions between mantle plumes and mid-ocean ridges : constraints from geophysics, geochemistry, and geodynamical modeling
This thesis studies interactions between mid-ocean ridges and mantle plumes using geophysics, geochemistry, and geodynamical modeling. Chapter 1 investigates the effects of the Marion and Bouvet hotspots on the ultra-slow spreading, highly-segmented Southwest Indian Ridge (SWIR). Gravity data …
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Element fractionation in the petrogenesis of ocean island basalts
… [230ThP32Th] atomic ratios (3-8x10-6) typical of basaltic lavas using a single focussing mass spectrometer. Compared to conventional alpha-counting methods, the technique presented typically gives a 2-5 fold improvement in reproducibility of 230 Th/232Th ratios, and furthermore uses -5x less …
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Geochemical Implications of Stirring and Mixing in the Earth's Mantle
… 206Pb/204Pb and 207Pb/204Pb measured on mid-ocean ridge basalt. The model is highly idealised, analytically tractable, and contains the essential physical processes involved: radioactive decay, the stirring and recycling of mantle convection, partial melting, and the mixing of melts. …
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Elasticity across the post-stishovite transition in subducted basalt
… Subducting slabs transport surface hydrated mid-ocean ridge basalt (MORB) into deep Earth, which is chemically and physically distinct from the surrounding mantle. Physical properties of MORB materials are thus important to understand observed seismic Vₛ anomalies. In this dissertation, …
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Interactions between mantle plumes and mid-ocean ridges : constraints from geophysics, geochemistry, and geodynamical modeling
This thesis studies interactions between mid-ocean ridges and mantle plumes using geophysics, geochemistry, and geodynamical modeling. Chapter 1 investigates the effects of the Marion and Bouvet hotspots on the ultra-slow spreading, highly-segmented Southwest Indian Ridge (SWIR). Gravity data …
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Temporal and petrogenetic constraints on volcanic accretionary processes at 9-10 degrees north East Pacific Rise
… by magmatic processes that occur beneath mid-ocean ridges, and the half-lives of 226Ra (1.6 kyrs) and 230Th (75 kyrs) make them ideally suited for determining eruption ages and placing constraints on eruption frequency and temporal changes in magma chemistry. Accordingly, major and trace …
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Temporal and petrogenetic constraints on volcanic accretionary processes at 9-10 degrees North East Pacific Rise
… by magmatic processes that occur beneath mid-ocean ridges, and the half-lives of 22 6Ra (1.6 kyrs) and 23Th (75 kyrs) make them ideally suited for determining eruption ages and placing constraints on eruption frequency and temporal changes in magma chemistry. Accordingly, major and trace …
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Experimental, geochemical and isotopic insights on melting and degassing behavior on Earth
… degassing of arc magmas, and mantle melting at mid-ocean ridges. Through this unlikely “medley” of Earth Science problems, parallels are drawn between experiments investigating melting and degassing at high pressure, geochemical and isotopic fingerprints of the Earth’s oldest rocks, and kinetic …
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Helium isotope geochemistry of oceanic volcanic rocks : implications for mantle heterogeneity and degassing
… have been measured in a number of mantle derived oceanic basalts. The goal of this research is to use the helium isotopic systematics to constrain the nature and origin of mantle heterogeneity in the oceanic mantle. Studies of helium partitioning in mid-ocean ridge basalt (MORB) glass, performed …
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Spatial-Statistical Properties of Geochemical Variability as Constraints on Magma Transport and Evolution Processes at Ocean Ridges
… properties of major element variability in basaltic lavas and mantle residues to constrain some of the processes and dynamics occurring beneath ocean ridge magmatic systems. Ocean ridges represent a critical setting for many geochemical fractionation processes involved in the chemical …
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Global isotopic signatures of oceanic island basalts
… island groups, 3 seamounts or seamount chains, 2 oceanic ridges and 1 oceanic plateau [for a total of 36 geographic features] are compiled to form a comprehensive oceanic island basalt [OIB] data set. These samples are supplemented by 90 selected mid-ocean ridge basalt [MORB] samples to give …
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Carbon systematics of the Icelandic crust and mantle
… hosts a greater mass of carbon than that of the oceans, atmosphere and crust combined, which has buffered the carbon content of the atmosphere over geological time. Yet only a few direct measurements of carbon from the upper mantle, and none from the lower mantle, have been made. Undegassed …
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The high temperature geochemistry of vanadium: From isotope ratios in ocean island basalt to thermal diffusion processes at the core-mantle boundary
… I measured the V isotopic composition of ocean island basalts (OIB) which potentially sample materials from the lower mantle rather than upper mantle as represented by mid-ocean ridge basalt (MORB). While there is some variability due to magmatic differentiation processes, the average δ51V …
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Global isotopic signatures of oceanic island basalts / by
… island groups, 3 seamounts or seamount chains, 2 oceanic ridges and 1 oceanic plateau [for a total of 36 geographic features] are compiled to form a comprehensive oceanic island basalt [OIB] data set. These samples are supplemented by 90 selected mid-ocean ridge basalt [MORB] samples to give …
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Trace element geochemistry of oceanic peridotites and silicate melt inclusions : implications for mantle melting and ocean ridge magmagenesis
The mantle melting process is fundamental to basalt genesis and crustal accretion at mid-ocean ridges. It is believed that melts ascend more rapidly than the surrounding mantle, implying a process similar to fractional melting may be occurring, but geochemical evidence for this has been lacking. …
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Single-crystal elasticity of Al-rich phases in the Earth’s transition zone and lower mantle
… frontiers in Earth sciences. The subduction of oceanic lithosphere must produce chemical heterogeneities in the mantle, which may explain some instances of lateral heterogeneity in seismic wave velocities. Seismic observations of the Earth’s interior provide the only method to investigate the …