Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996. / Includes bibliographical references (p. 126-139). / by Richard A. Bennett. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1986. / Microfiche copy available in Archives and Science. / Bibliography: leaves 273-281. / by Henry Box Selkirk. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002. / Includes bibliographical references. / Through experimental petrology and geodynamic modeling, processes of melting under thick lithospheres on the Earth and the moon are investigated. Phase equilibrium experiments were carried out on Apollo 14B and 15C picritic glasses (Chapters 5 and 6) and on a Sierran high-potassium lava (Chapter 1). These, along with petrologic modeling of Cascades high alumina olivine tholeiites (Chapter 4), yield information on depths and pressures of melt generation and constraints on source composition. Geodynamic modeling of lithospheric thinning processes, including delamination under the Siberian flood basalts (Chapter 2), gravitational instabilities in the lunar magma ocean cumulates (Chapter 7), and thinning and convection due to giant meteorite impacts (Chapters 3 and 8), has lead to new models for melt production. These studies together show how lithospheric thinning and unusual mantle compositions can lead to melting without calling on unusual mantle potential temperatures, and can explain the volumes and durations of continental flood basalts and lunar mare basalts. / by Linda Tarbox Elkins Tanton. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997. / Includes bibliographical references. / by Emile Ernestine Ebba Hooft. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002. / Includes bibliographical references. / I report on laboratory experiments designed to investigate the microphysical processes that result in rate- and state-dependent friction behavior and experiments designed to match the boundary conditions used by numerical models of granular friction. The effect of relative humidity (RH from <5% to 100%) is investigated with velocity stepping tests (10-20 tm/s) and slide-hold-slide (SHS) tests (3-1000 s) on 3 mm thick layers of quartz powder, alumina powder, Westerly granite powder, and Westerly granite blocks sheared at 25 MPa normal stress. Powders are conditioned in situ under controlled RH to create new surface area before shearing. A transition from velocity-strengthening to velocity-weakening frictional behavior occurs as RH increases. Frictional healing is negligible at low humidity and increases with increasing RH for both materials. While the coefficient of sliding friction for powders is independent of humidity, bare surface data indicate that sliding friction decreases with increased RH. Normal stress vibrations in SHS tests can add compaction induced granular strengthening, but for constant normal force tests, chemically assisted healing mechanisms control the friction behavior. The chemically assisted contact junction processes can be reduced or turned off at low humidity at room temperature in quartz and alumina. Velocity stepping tests and SHS tests are also performed at different values of applied normal stress (5 to 45 MPa) after pre-conditioning at high normal stress (40 and 35 MPa) for powders and no pre-conditioning for bare surfaces. Time-dependent frictional healing decreases with increasing normal stress. / (cont.) For the powders, velocity stepping tests require the use of a 2 state variable model to accurately retrieve rate- and state-friction parameters. The complex velocity dependent behavior may be a result of over-compaction in the granular layers during preconditioning. Numerical models of granular shear show lower friction and a greater tendency for stick slip than laboratory studies designed to investigate fault mechanics. Chapters 4 and 5 detail laboratory experiments designed to reproduce the conditions of numerical models and test the role that grain characteristics play in controlling frictional behavior. Friction and microstructural data are compared for direct shear experiments on thin layers (2-3 mm) of angular quartz sand and spherical glass beads. We study the effect of grain shape, roughness, size distribution,comminution, and particle dimensionality In a non-fracture loading regime, sliding friction for In a non-fracture loading regime, sliding friction for smooth spherical particles ([mu] [approx. equal to] 0.45) is measurably lower than for angular particles ([mu] [approx. equal to] 0.6). Anarrow particle size distribution (PSD) of spherical beads (105-149 [mu] tm) exhibits unstable stick-slip behavior, whereas a wide PSD of spheres (1-800 [mu]m) and the angular gouge display stable sliding. At higher stress, where grain fracture is promoted, initially spherical particles become stable with accumulated slip and friction increases to the level observed for angular gouge. Quartz glass rods are sheared in 1-D and 2-D configurations and I compare the results to previously published numerical models and to the friction behavior of angular gouge. / by Kevin M. Frye. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001. / Includes bibliographical references (p. 147-152). / This thesis presents imaging results from a 3D reverse vertical seismic profile (RVSP) dataset measured at a hydrocarbon bearing pinnacle reef in northern Michigan. The study presented many challenges in seismic data processing and imaging, as the survey geometry was unique in several ways. Reverse VSP, which uses seismic sources in a borehole and receivers on the earth's surface, is fairly rare. RVSP in 3D with a random distribution of surface geophones is unprecedented. At the time this data was collected, no commercially available processing tools existed to address this geometry, so a processing scheme had to be developed. The data processing sequence presented in this thesis, which includes amplitude corrections, first break picking, deconvolution, wavefield separation, and application of statics, takes advantage of the repeatible signature of the new downhole source (Paulsson et al., 1998). Since the data can be handled in common-receiver gathers instead of the usual common-source gathers, it can be treated like several single offset VSPs during the processing sequence. Issues related to the 3D geometry and the random distribution of the receiver array need not be addressed until the imaging step. The generalized Radon transform (GRT) migration method of Miller et al. (1987) provides a high resolution image of a portion of the target reef at 4600 feet (1400 meters) depth. The high resolution of the image is largely due to the downhole source, which generated a high powered signal at frequencies up to several hundred Hertz. Another factor in the high resolution of the image is the success of receiver consistent model-based Wiener deconvolution (Haldorsen et al., 1994), possible because the source signature was repeatable. Due to adverse conditions and power system failure, a large portion of the surface array did not record data. / (cont.) The reduced spatial coverage limits the extent of the migrated image, precluding an evaluation of the effectiveness of the random receiver spread. The limited nature of the receiver array also caused artifacts resembling migration smiles in the image. These artifacts are partially suppressed by limiting the aperture of the migration, but this also removes dipping reflectors from the image. To maximize the imaging capibilities of the data, a second approach complimenting the GRT method is developed. This approach, termed vector image isochron (VII) migration, removes array artifacts from the image without losing energy from dipping reflectors. This allows artifacts in the conventional image to be identified, aiding interpretation of the GRT images. VII images also show more even illumination than conventional images, although an effect similar to NMO stretching reduces the resolution of the VII image as compared to the GRT image. The VII scheme is an extension of the GRT migration process of Miller et al. (1987), but involves forming an image which depends on the imaged plane orientation, transforming the image based on the array geometry, then finishing the GRT summation over plane orientations. The VII imaging method is derived in both 2D and 3D with the assumption that the ray paths are straight and that at least one of the arrays, source or receiver, is horizontally oriented. The surface array can have any distribution, regular or random. The other array can have any orientation in general, although this thesis assumes that it will be either another surface array or a vertically oriented borehole array. ... / by Mary L. Krasovec. / Ph.D.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014. / Some pages printed landscape orientation. Cataloged from PDF version of thesis. / Includes bibliographical references (pages 299-311). / The mechanisms of magma ascent and emplacement inferred from study of intrusive complexes have long been the subject of intense debate. Current models favor incremental construction, but much of this work has been focused on a single crustal level. However, the study of magmatism throughout the crust is critical for understanding how magma ascends through and intrudes surrounding crustal material. I present new field, geochronologic and geochemical data from three intrusive complexes emplaced at a range of crustal depths in the Cretaceous North Cascades magmatic arc. Integration of geological mapping and high-precision U-Pb TIMS geochronology allows me to demonstrate variable styles of intrusion in different complexes: Assembly of the Black Peak intrusive complex occurred via a series of small (<1 km 3) magmatic increments from ca. 91.7 Ma to 86.8 Ma. My data indicate each of these increments were emplaced and solidified without major assimilation of country rock. The Seven- Fingered Jack intrusive complex, emplaced around ~20-25 km, preserves a similar record of intrusion between ca. 91.8 Ma and 90.5 Ma. Significant compositional variability and antecrystic zircons suggest that the Seven-Fingered Jack represents the remnants of mid-crustal magmatic conduit. Geochronology from the deep-crustal (~25-30 km) Tenpeak intrusive complex, intruded between ca. 92.2 Ma and 89.5 Ma, suggests that plutons comprising the complex were assembled rapidly (<300 ka). These intrusive complexes represent different parts of an arc system, including deep- and shallow-crustal intrusions and a magmatic conduit. I propose a model where increments of magma migrated through the crust in magmatic conduits that were active multiple times. These conduits focused rising magma and served as a crustal filter. Geochronologic and isotopic variability between the Tenpeak and Black Peak intrusive complexes are likely a result of this filtering process and the vastly different conditions in the deep and shallow crust. / by Erin Kathleen Shea. / Ph. D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1992. / Vita. / Includes bibliographical references. / by David Speir McCormick. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1992. / Includes bibliographical references (leaves 168-175). / by Robert Joseph Wilt. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, 1984. / Microfiche copy available in Archives and Science. / Bibliography: leaves 251-264. / by Hein J.W. de Baar. / Ph.D.