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 16 of 16 for “"Mantle Heterogeneity"”.
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Mantle Heterogeneity Through Mid-Ocean Ridge Basalts
The chemical heterogeneity of Earth's upper mantle is often examined through mid-ocean ridge basalts (MORB), which contest the prevalent assumption of a well-mixed convecting mantle. This dissertation delves into studying mantle heterogeneity from a local to regional scale. Initially, petrological …
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Helium isotope geochemistry of oceanic volcanic rocks : implications for mantle heterogeneity and degassing
… of helium 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) …
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Helium isotope geochemistry of oceanic volcanic rocks : implications for mantle heterogeneity and degassing
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1982.
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Insights into the location, nature and influence of mantle heterogeneity in the Galápagos mantle plume
… of the Earth's, highly heterogeneous, convecting mantle. Our view of the Earth's mantle is, however, partially obscured by processes that influence mantle-derived melts as they transition through the lithosphere (e.g. mixing, assimilation). Nevertheless, via careful consideration of the magmatic …
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Dismantling the deep earth : geochemical constraints from hotspot lavas for the origin and lengthscales of mantle heterogeneity
… 3 deals with the largest possible scales of mantle heterogeneity, and presents the highest magmatic 3He/4He (33.8 times atmospheric) discovered in Samoa and the southern hemisphere. Along with Samoa, the highest 3He/4He sample from each southern hemisphere high 3He/4He hotspot exhibits lower …
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Dismantling the deep earth : geochemical constraints from hotspot lavas for the origin and lengthscales of mantle heterogeneity
… 3 deals with the largest possible scales of mantle heterogeneity, and presents the highest magmatic 3He/4He (33.8 times atmospheric) discovered in Samoa and the southern hemisphere. Along with Samoa, the highest 3He/4He sample from each southern hemisphere high 3He/4He hotspot exhibits lower …
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The geochemistry of Cenozoic basalts and peridotite xenoliths from Hannuoba region, eastern China : implication for their petrogenesis and subcontinental mantle heterogeneity
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.
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Quantifying Crustal Assimilation in Historical to Recent (1329-2005) Lavas at Mt. Etna, Italy: Insights from Thermodynamic Modeling
… sedimentary basement), and (2) changes in the mantle source, possibly due to increased interaction between the mantle source and subduction related fluids, and/or a mantle source that was melted to different degrees. This study quantitatively examines the role of crustal contributions to …
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Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges
… 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 disequilibria, radiogenic isotopes, and trace-element compositions were measured for the slow-spreading Arctic mid-ocean ridges (MOR). A focused case …
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Upper mantle reflectivity beneath an intracratonic basin: insights into the behavior of the mantle beneath Illinois basin.
… images of the lower crust and uppermost mantle beneath the Illinois basin have been derived from reprocessing of several hundred kilometers of industry seismic reflection data using extended vibroseis recorrelation. The recorrelation was based on extending an originally 4-s correlated …
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Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges
… 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 disequilibria, radiogenic isotopes, and trace-element compositions were measured for the slow-spreading Arctic mid-ocean ridges (MOR). A focused case …
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Mantle and crustal controls on the distribution of chalcophile elements in silicate melts
… and assess the effects of crustal thickness, mantle heterogeneity and oxygen fugacity on the sulfur and CSE systematics of mantle-derived basalts. Conclusions drawn from each sample set offer unique insights into how chalcophile elements are processed and distributed in the Earth’s crust, with …
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Seismic structure of the mantle beneath the Pacific Hemisphere
Aside from xenoliths, the Earth's mantle is a region that is inaccessible directly, leaving us with limited tools to investigate its characteristics indirectly. Seismology is a tool well-suited for this purpose, and has provided valuable insight regarding many fundamental processes occurring within …
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A heavy stable isotope approach to tracing mantle source and process
The geochemistry of global mantle melts suggests that both mid-ocean ridge basalts (MORB) and ocean island basalts (OIB) sample lithological heterogeneities originating in both the upper and lower mantle, with recycled crustal material accounting for a significant part of this variability. …
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Seismic imaging of the mantle transition zone
… high-resolution seismo-stratigraphy of the upper mantle transition zone. The generalized Radon transform (GRT) is based on the single scattering approximation and maps singularities (reflections) in broad-band data into singularities (reflectors/scatters) in the medium. It is able to detect and …
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Sound velocity study of natural orthopyroxenes with varying iron content
… to identify the underlying causes of seismic heterogeneity. Such laboratory measurements are essential to determine the structure, composition and temperature variability of the upper mantle. This study presents a systematic characterization of orthopyroxene elastic moduli as a function of …