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 20 of 58 for “"MORB"”.
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Syn-eruptive degassing of a single submarine lava flow : constraints on MORB CO2 variability, vesiculation, and eruption dynamics
Mid-ocean ridge basalts (MORBs) exhibit a wide range of CO2 concentrations, reflecting saturation to supersaturation (and rarely undersaturation) relative to their emplacement depths. In this study, we explore the mechanisms of CO2 degassing and the implications this has for estimating the advance …
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Syn-eruptive degassing of a single submarine lava flow : constraints on MORB CO₂ variability, vesiculation, and eruption dynamics
Mid-ocean ridge basalts (MORBs) exhibit a wide range of CO2 concentrations, reflecting saturation to supersaturation (and rarely undersaturation) relative to their emplacement depths. In this study, we explore the mechanisms of CO2 degassing and the implications this has for estimating the advance …
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The influence of ridge geometry at the ultraslow-spreading Southwest Indian Ridge (9⁰-25⁰E) : basalt composition sensitivity to variations in source and process
… One 630 km long supersegment erupts N-MORB that is progressively enriched in incompatible element concentrations from east to west. The second 400 km long supersegment contains three separate volcanic centers erupting E-MORB and connected by long amagmatic accretionary segments, where …
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Spatial-Statistical Properties of Geochemical Variability as Constraints on Magma Transport and Evolution Processes at Ocean Ridges
… use spatial patterns of mid-ocean ridge basalt (MORB) glass variability to test competing hypotheses about crystallization in the thermal boundary layer beneath ocean ridges. I develop the hypothesis that reactive crystallization (crystallization influenced by chemical exchange with surrounding …
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The influence of ridge geometry at the ultraslow-spreading Southwest Indian Ridge (9º-25ºE) : basalt composition sensitivity to variations in source and process
… One 630 km long supersegment erupts N-MORB that is progressively enriched in incompatible element concentrations from east to west. The second 400 km long supersegment contains three separate volcanic centers erupting EMORB and connected by long amagmatic accretionary segments, where …
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Elasticity across the post-stishovite transition in subducted basalt
… 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, physical properties of …
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Mantle Heterogeneity Through Mid-Ocean Ridge Basalts
… 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 models were utilized to scrutinize the source and …
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Neon, Helium and Argon isotope systematics of the Hawaiian hotspot
… Mauna Kea, Kohala and Kilauea lavas yielded MORB-like to moderately high 3He/4He ratios, while 3He/4He ratios in post-shield stage Haleakala lavas are MORB-like. Few samples show 20Ne/22Ne and 21Ne/22Ne ratios different from the atmospheric values, however, Mauna Kea and Kilauea lavas with …
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Temporal and petrogenetic constraints on volcanic accretionary processes at 9-10 degrees north East Pacific Rise
… isotopically enriched mid-ocean ridge basalt (MORB) collected off-axis erupted >8 ka and that E-MORB magmatism is interspersed with normal, depleted MORB magmatism. Lava ages are consistent with eruption from the AST and flow down the ridge flanks, which is in contrast to previous studies that …
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Temporal and petrogenetic constraints on volcanic accretionary processes at 9-10 degrees North East Pacific Rise
… isotopically enriched mid-ocean ridge basalt (MORB) collected off-axis erupted >8 ka and that E-MORB magmatism is interspersed with normal, depleted MORB magmatism. Lava ages are consistent with eruption from the AST and flow down the ridge flanks, which is in contrast to previous studies that …
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A heavy stable isotope approach to tracing mantle source and process
… 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. Recently, heavy stable isotopes have been …
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Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges
… case study of 33 young (<10ka) MOR basalts (MORB) from the shallow endmember of the global ridge system, the Kolbeinsey Ridge (67°05’-70°26’N) found that unaltered Kolbeinsey MORB have universally high (230Th/238U) (1.165-1.296) and relatively uniform (230Th/232Th) (1.196-1.324), εNd (8.43- …
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Kinetic processes of mantle minerals
… results designed to constrain the processes of MORB generation. The main focus of this study is to investigate the location and the related processes of the transformation boundary from spinel to garnet peridotite facies at subsolidus conditions, because the presence of garnet in melting …
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Kinetic processes of mantle minerals
… results designed to constrain the processes of MORB generation. The main focus of this study is to investigate the location and the related processes of the transformation boundary from spinel to garnet peridotite facies at subsolidus conditions, because the presence of garnet in melting …
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Geophysical and geochemical constraints on submarine volcanic processes
… CO2 concentrations in mid-ocean ridge basalts (MORB). Based on synthetic vesicle populations, 2D and 3D measurements, and Raman spectroscopy, I show that traditional methods overestimate MORB CO2 concentrations by as much as 50%, which has important implications for estimating ridge CO2 flux. In …
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Helium isotope geochemistry of oceanic volcanic rocks : implications for mantle heterogeneity and degassing
… helium partitioning in mid-ocean ridge basalt (MORB) glass, performed by crushing and melting in vacuo, show that a significant fraction of the helium resides within vesicles. Measured concentrations are therefore a function of original helium content, magmatic history, vesicle size and …
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Helium and lead isotope geochemistry of oceanic volcanic rocks from the East Pacific and South Atlantic
… Rise covers ~80% of the variability for Pacific MORB, due to small-scale heterogeneity in the underlying mantle. Tholelites at these seamounts have He, Pb, Sr and Nd isotope compositions which are indistinguishable from MORB. Associated alkali basalts show more radiogenic He, Pb and Sr …
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ΟΦΙΟΛΙΘΟΙ ΤΗΣ ΝΗΣΟΥ ΚΡΗΤΗΣ
… ΒΑΣΑΛΤΩΝ ΚΑΙ ΔΙΑΒΑΣΩΝ ΤΥΠΟΥ MORB ΚΑΙ IAT.
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The composition of noble gas and co2 in the european subcontinental lithospheric mantle
… European SCLM range (6±1 Ra) that is lower than MORB (8±1 Ra). This indicates a widespread recycling of crustal material below Europe if compared to other continental rift (e.g., Antarctica, East African). However, the careful investigation of olivine, cpx, and opx in single localities allowed …
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Basalt petrogenesis beneath slow- and ultraslow-spreading Arctic mid-ocean ridges
… case study of 33 young (<10ka) MOR basalts (MORB) from the shallow endmember of the global ridge system, the Kolbeinsey Ridge (67°05'-70°26'N) found that unaltered Kolbeinsey MORB have universally high (230Th/238U) (1.165-1.296) and relatively uniform (230Th/232Th) (1.196-1.324), ENd …
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