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.
Results
Showing 1 to 20 of 790 for “"crust"”.
-
Hydrothermal alteration of the ocean crust: insights from Macquarie Island and drilled in situ ocean crust
… process in the formation and aging of the ocean crust, influencing its structure, physical and chemical properties, and the composition of the oceans and the mantle. The impact of hydrothermal circulation on mid-ocean ridge processes depends on the composition and volume of circulating …
-
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 …
-
A search for layering in the oceanic crust
… 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 velocity …
-
Carbon systematics of the Icelandic crust and mantle
… 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 basalts erupted at mid-ocean …
-
A search for layering in the oceanic crust
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.
-
Nuclear reactions in the crust of accreting neutron stars
… thermal properties and the composition of the crust. To model the nuclear energy release and crust composition, we build up a first complete network with pycnonuclear fusion. We run a consistent nuclear reaction network that follows the evolution of an accreted fluid element from the atmosphere …
-
Characterization of lunar crust with moon mineralogy mapper data
… determine the compositional variations of lunar crust with depth, and establish a new model to describe the structure of the lunar crust.
-
The evolution of the Archaean continental crust of Northern Zimbabwe
… indicate the presence of continental crust in Northern Zimbabwe prior to the"" 2.7 to "" 2.6Ga "event" which terminated with the stabilisation of the Zimbabwe Craton. The "Kober Technique" (Kober, 1986, 1987) of direct thermal ionisation of zircons has been set up in order to …
-
Melt-freeze crust formation and evolution in the Columbia Mountains
Melt-freeze crusts play an important role in many slab avalanches. Recent work with snowpack models has shown the need for field based research on the formation and evolution of melt-freeze crusts. This project uses historical weather and snowpack data to determine the metrological conditions …
-
Crust and upper mantle structure of the northeastern United States
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980.
-
Archean continental crust formation and the rise of atmospheric oxygen
… surface: the establishment of the continental crust and the progressive rise of an oxygenated atmosphere. The volume of continental crust on the earliest Earth is a critical parameter for constraining the chemical evolution of major terrestrial reservoirs, and radiogenic isotope signatures …
-
Imaging of crust and mantle structures with teleseismic reflected waves
… reflected waves to study discontinuities in the crust and mantle. Specifically, we further developed virtual deep seismic sounding (VDSS) to probe the Moho and we used SS precursors to study mantle transition zone discontinuities. To extend the applicability of VDSS, we developed a source …
-
On Ultra-High Temperature Metamorphism in the Mid-Lower Crust
… understanding of UHT metamorphism in the Earth's crust. This work focuses on the development of hybrid monzonorites and emery at Salt Hill, located in the southeasternmost edge of the Cortlandt Complex. First, a thermobarometric study focuses on the P-T conditions of the country rock into which …
-
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 …
-
The heterogeneity and volatile content of Earth’s mantle, magmas and crust
… content of the mantle, subducted oceanic crust, and arc magmas as well as the structure of slow spreading ocean crust and the heterogeneity of Earth’s upper mantle. In Chapter 2, I directly explore the halogen (F and Cl) content of mantle minerals in situ, then use these measurements to …
-
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 …
-
Deformation Mechanisms and Strain Localization in the Mafic Continental Lower Crust
The rheology and strength of the lower crust play a key role in lithosphere dynamics, influencing the orogenic cycle and how plate tectonics work. Despite their geological importance, the processes that cause weakening of the lower crust and strain localization are still poorly understood. Through …
-
An experimental approach to thermal and solar weathering of Mercury's crust
… aims to map the composition of the Mercurian crust. This composition has direct implications for the formation and evolution of the planet (Solomon, 2003). The instruments that will compositionally map the surface are calibrated and compared with materials in an Earth-like environment. …
-
Geological and thermochronological evolution of the lower crust of southern Africa
… and isotopic studies of kimberlite-borne crustal xenoliths have been used to elucidate the architecture and thermal evolution of the continental lithosphere of southern Africa. U-Pb accessory mineral geochronology of lower crustal xenolith assemblages illustrate the youth of …
Page 1 of 40