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 118 for “"Oceanic crust"”.
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The accretion of lower oceanic crust
… control on the composition of the oceans, ocean crust, and upper mantle. Two complementary approaches are used to investigate the thermal implications of endmember theoretical models that describe the accretion of the lower oceanic crust at fast spreading rates. The first approach uses the record …
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A search for layering in the oceanic crust
… have shown that the seismic structure of the oceanic crust can be usefully parameterized by a small number of locally horizontal layers within which the rates of change of velocity and impedance as a function of depth are approximately constant. Layer boundaries are defined by changes in …
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A search for layering in the oceanic crust
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.
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Ridge segmentation, tectonic evolution and rheology of slow-spreading oceanic crust
Two-thirds of the Earth's surface is oceanic crust formed by magmatic and tectonic processes along mid-ocean ridges. Slow-spreading ridges, such as the Mid-Atlantic Ridge, are discontinuous and composed of ridge segments. Segments are thus fundamental units of magmatic accretion and tectonic …
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Hydrothermal alteration of upper oceanic crust formed at fast spreading rates
… from deep in the Earth’s interior to the ocean crust, the oceans and the atmosphere. It is also on of the principal mechanisms for heat transfer from the mantle to the oceans, atmosphere and ultimately, outer space. This process fundamentally influences the composition of the ocean crust during …
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Ridge segmentation, tectonic evolution and rheology of slow-spreading oceanic crust
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996.
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Fracture Analysis of the Lower Oceanic Crust, Atlantis Bank, Southwest Indian Ridge
<p>Atlantis Bank (AB) is an oceanic core complex (OCC), formed at the slow-spreading (spreading rate/yr) Southwest Indian Ridge (SWIR)-Atlantis II transform junction. AB is a domal massif composed of lower crustal and upper mantle rocks exhumed along a normal-sense detachment shear zone/fault. OCCs …
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A study of the seismic structure of upper oceanic crust using wide-angle reflections
The lateral homogeneity of oceanic crust on the scale of a seismic experiment is a condition that most methods of seismic interpretation depend on. Whether this condition is in fact true is largely unknown and only recently have efforts been made to test this hypothesis. This thesis is part of that …
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A study of the seismic structure of upper oceanic crust using wide-angle reflections
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1983.
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The primary structures and fabrics of the upper mantle and lower oceanic crust from ophiolite complexes
… history of the upper mantle and lowermost oceanic crust at accretionary margins. In all areas the mantle has similar petrological features. It is composed largely of harzburgite which is often compositionally banded into orthopyroxene-rich and olivine-rich segregation layers. Dunitic sheets …
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Deciphering the signature of fluid/rock reactions in the lower oceanic crust: The Oman ophiolite analogue
… moderating elemental and heat transfers between oceanic lithosphere and the hydrosphere. The characterization and quantification of fluid/rock reactions and fluid fluxes in fast-spreading mid-ocean ridges has been a long-term ambition given these ridges are responsible for formation of two thirds …
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Seismic and magnetic constraints on the structure of upper oceanic crust at fast and slow spreading ridges
The upper ocean crust contains a comprehensive record of the shallow geological processes active along the world's mid-ocean ridge system. This thesis examines the magnetic and seismic structure of the upper crust at two contrasting ridges-the fast spreading East Pacific Rise (EPR) and the slow …
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Seismic and magnetic constraints on the strucutre of upper oceanic crust and fast and slow spreading ridges
The upper ocean crust contains a comprehensive record of the shallow geological processes active along the world's mid-ocean ridge system. This thesis examines the magnetic and seismic structure of the upper crust at two contrasting ridges-the fast spreading East Pacific Rise (EPR) and the slow …
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Structural Re-orientation of Magmatic Fabrics and Layering in the Lower Oceanic Crust: Hole GT1, Wadi Tayin Massif, Samail Ophiolite
… Drilling Project to better constrain models of crustal accretion. The gabbro glacier model proposes that crystallized basalt flows down and away from the crystallization site to form the lower crust while the sheeted sill model proposes that basaltic melt crystallizes at multiple levels in the …
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The Impact of Fe-Ti Oxide Concentration on the Structural Ridgity of the Lower Oceanic Crust, Atlantis Bank, Southwest Indian Ridge
<p>Fe-Ti oxides are important components of oceanic core complexes (OCC) formed at slow-spreading mid-ocean ridges since Fe-Ti oxides are more susceptible to crystal-plastic deformation than silicate minerals. This study investigated the predicted relationship between the presence and concentration …
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The Effects of Amphibole- and Sulfide-Producing Melts on Crustal Strength in Gabbros of Lower Oceanic Crust in Oceanic Core Complexes, Mid-Atlantic and Southwest Indian Ridges
<p>This study investigates gabbro-cored oceanic core complexes in the slow-spreading Mid-Atlantic Ridge (MAR) and the ultraslow spreading Southwest Indian Ridge (SWIR). Dikelets are a texture found in thin section samples from these systems that form as a result of crystal-plastic deformation. Thin …
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Ocean bottom seismic scattering
Seismic studies of the oceanic crust, both experimental and theoretical, often assume a flat seafloor and laterally homogeneous crust. This is done regardless of the appearance in seismic data of obvious effects due to scattering from lateral heterogeneities both on and in the seafloor. Detailed …
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Tectonic and sedimentary history of the Mid-Natal Valley (S.W. Indian Ocean)
… deep basin plain. Thinned (20-25 km) continental crust, attenuated and subsided in response to Gondwana rifting and drifting, underlies the Central Terrace, Tugela Cone and Mozambique Ridge. Southern margins of the Central Terrace and Tugela Cone are cored by a series of subsea floor ridge and …
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The petrology, geochemistry and structure of the plutonic rocks of the Oman ophiolite
The Oman Ophiolite represents a fragment of oceanic crust and upper mantle that was emplaced onto the Arabian continental margin during the late Cretaceous. An area of 3000km2, comprising the Haylayn and Rustaq Blocks, has been mapped and specific localities were investigated in order to examine …
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Fluid-mobile element cycling (halogens, boron, lithium) and sourcing through the Costa Rican convergent margin
… forearc. Describing fluid loss from subducting oceanic crust to the forearc is difficult for several reasons including differences in pathways due to faulting, variability in the depth in which fluids are released, and compositional changes of the subducting slab. Seepage through the …
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