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 “"Middle crust"”.
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Tectonic significance of the Atnarko complex, Coast Mountains, British Columbia
… and compression. The conditions of the lower and middle crust within the orogen were established by how strain was partitioned across the orogen. The distributed strain also shaped how the orogen responded to Tertiary extension. Continued compression to the northwest of the Atnarko complex led to …
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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 …
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Continental Arc Processes in British Columbia and Earthquake Processes in Virginia: Insights from Seismic Imaging
… P and S-wave seismic velocity models of the crust and uppermost mantle. A felsic upper crust and a felsic to intermediate middle crust are observed in both the batholith complex and the accreted Stikine island arc terrane. The P and S wave models demonstrate a high-velocity (P 7.0 km/s, S 3.8 …
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The Structure and Behavior of Plate Boundary Regions Through the Wilson Cycle
… strike-slip conjugate faulting in the upper crust. In it we present new electron backscatter diffraction (EBSD) data and in situ trace element and U-Pb isotopic compositions for monazite and titanite. These datasets provide quantitative constraints on the style and conditions of deformation …
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Continental Deformation: Collisional Orogenesis to Passive Margin Processes
… changes from seismogenic in the brittle upper-middle crust, to aseismic in the ductile middle-lower crust. I determine correlation coefficients between ksn and: MHT coupling, lithology, and precipitation using a series of cross-orogen profiles. Averaging the results reveals a strong correlation …
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A study of the structure of the Belgian crust by Moho determination and local seismic tomography
… is known about the extension of the different crustal structures into the middle and lower crust. Until now, only seismic profiles and gravimetric and magnetic data gave some insights. The general aim of this thesis is to improve the understanding of the lower/middle crustal structure of …
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Seismic imaging and thermal modeling of active continental rifting processes in the Salton Trough, Southern California
… attest to ongoing rifting of thin, transitional crust. Recently acquired controlled-source seismic refraction and wide-angle reflection data in the Salton Trough provide constraints upon crustal architecture and active rift processes. The crust in the central Salton Trough is only 17-18 km thick, …
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How Hot, How Deep, How Long: Constraints on the Tectono-Metamorphic Evolution of Granulite Terranes
… (UHT) and partial melting of Earth's crust. Granulites are ubiquitous in exhumed Archean cratons and are thought to comprise much of Earth's stable lower crust. Understanding the mechanisms responsible for crustal heating in Archean terranes is thus paramount to understanding the …
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Probing the interior of an active volcano: Three-dimensional seismic tomography at Montserrat
… of magma storage regions in the upper and middle crust, which can influence the style and time-scales of eruptions. Seismic tomography can provide detailed resolution of the physical characteristics of complex three-dimensional structures in the subsurface, and has been successfully …
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Quantifying The Properties Of Magmatic Intrusions In The Central Andes With Geodesy
… vertically-aligned reservoirs in the lower crust and middle crust to explain the observation of uplift and peripheral subsidence at Uturuncu. The ratio of vertical to radial surface displacements for single inflation source is increased by adding a dipole reservoir, but decreased to a …
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Crustal velocity structure in the southern coast belt, British Columbia, from a seismic refraction survey
… forward modelling was used to interpret crust and upper mantleP-wave velocity structure. The structural model features a thin (0.5 to 3.0 kin) near-surface layer with an average velocity of 4.40 km/s, a significant vertical velocity gradient and lateral variations. This uppermost stratum …
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Polyphase Proterozoic tectonometamorphic history of the Taos Range, northern New Mexico
… exposed in the northern Taos Range where supracrustal rocks are sandwiched between ca. 1.65 Ga plutons. Supracrustal rocks preserve peak metamorphic conditions of T less than or equal to 650 degrees Celsius, 6-8 kb in the northern Taos Range, and T greater than or equal to 550 degrees Celsius, …
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The structural setting of the Canaã dos Carajás region and Sossego-Sequeirinho deposits, Carajás – Brazil
… aims of the study include: (1) identification of crustal scale regional lineaments and their relationship with mineral deposits; (2) a new tectonic framework and structural model for the Canaã dos Carajás region; and (3) description and interpretation of the structural framework of the Sossego and …
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Metamorphic evolution of ultrahigh-temperature granulite facies and upper amphibolite facies rocks of the Epupa Complex, NW Namibia
… heating-cooling paths but represent individual crustal levels: Heating led to the partial replacement of amphibole, biotite and muscovite through dehydration melting reactions. The peak-metamorphic P-T conditions of c. 700°C, 6.5 +/- 1.0 kbar (south-eastern part), c. 820°C, 8 +/- 0.5 kbar …
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Middle Crustal Ductile Deformation Patterns in Southern Tibet: Insights from Vorticity Studies in Mabja Dome
<p>Mabja Dome, southern Tibet, exposes mid-crustal rocks proposed to have originated from a southward flowing mid-crustal channel. Kinematic, mean kinematic vorticity (Wm), and metamorphic petrography analyses on these mid-crustal rocks were performed to test this hypothesis. Kinematic indicators …
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Metamorfismo ercinico di bassa-pressione: evoluzione tettonico-metamorfica del complesso di mandatoriccio (massiccio della Sila - Calabria)
… that experienced abnormal heat flow in shallow crustal levels (T > 600 °C; P < 4 kbar) resulting in anomalous geothermal gradients (60-150 °C/km). The abnormal amount of heat has been related to crustal underplating of mantle-derived basic magmas or to thermal perturbation linked to intrusion of …