Tectonics and Structure Commons^™

Migmatite Formation, Geochronometer Petrogeneisis, And Rare Earth Element Mineralization In The Adirondack Mountains, Ny, Kaitlyn Suarez

Doctoral Dissertations

The Adirondack Mountains in upstate New York contain exposures of complex partially melted rocks, in addition to iron oxide-apatite (IOA) deposits with variable rare earth element (REE) concentrations. Previous workers have suggested that melting occurred during the ca. 1150 Ma Shawinigan and the ca. 1050 Ma Ottawan orogenies. However, there are challenges in determining the timing of melting and the number of partial melt events. Further, tectonic models must be developed to describe the petrogenesis of IOA and REE mineralization. Migmatites are present along Rt. 4/22 near Whitehall, NY. In chapter two, all layers of a single migmatitic rock were …

Natural, Experimental, And Educational Explorations Of The Interiors Of Terrestrial Planetary Bodies, Nadine L. Grambling

Doctoral Dissertations

Planetary interiors are enigmatic, inaccessible, and vital to the processes that have formed the rocks we see on the surface of bodies in the inner Solar System today. Based on geophysical explorations of the Moon and Earth, along with information gleaned from rocks at the surface today, there is understanding of the basic structure and processes at depth. Using a combination of natural samples and experimental studies, we attempt to learn more about the physical conditions beneath the surface, and their effect on material properties and tectonics processes in the mantle.

On Earth, mid-ocean ridge processes have long been debated, …

Implications And Significance Of Partial Melting On The Tectonic History Of The Eastern Adirondack Mountains, Claire Rose Pless

Doctoral Dissertations

The eastern Adirondack Mountains contain abundant exposures of high-grade metamorphic rocks. These exposures are interpreted to be a window into the mid/deep crust of an ancient, large, hot, long-duration orogen, allowing the Adirondack Mountains to be used as an analogue to the deep processes of modern orogens. Currently interpreted thermo-tectonic events in the eastern Adirondack Mountains include the ca. 1245-1220 Ma Elzevirian orogeny, the ca. 1190-1150 Ma Shawinigan orogeny, emplacement of the ca. 1150 Ma AMCG igneous suite, the ca. 1090-1050 Ma Ottawan orogeny, and a ca. 1050-1020 Ma extensional collapse phase. This dissertation focuses on six migmatite domains within …

3-D Shear Wave Velocity Structures Of The Crust And Upper Mantle Beneath Cascadia And New Zealand From Full-Wave Ambient Noise Tomography, Sampath Rathnayaka Mudiyanselage

Doctoral Dissertations

The (de)hydration process and the amount of hydrated sediment carried by the downgoing oceanic plate play a key role in the subduction dynamics. The deformation and (de)hydration of the downgoing tectonic plates, as well as the seismic, tsunami, volcanic hazards, in Cascadia and the New Zealand regions are not fully understood, partly due to a lack of combined studies of onshore and offshore data. In order to address these questions, we developed a 3-D high-resolution shear wave velocity model beneath Cascadia, the North and the South Islands of New Zealand, extending from offshore to onshore, with the use of full-wave …

A New Paradigm For Predicting Fracture Growth, Interaction And Linkage: Faulting In Numerical And Physical Experiments With Work Optimization, Jessica Mcbeck

Doctoral Dissertations

This dissertation predicts fracture propagation and interaction within the framework of work optimization. With this approach, fractures are predicted to propagate along the path that optimizes work. This dissertation includes three projects that predict fracture growth using work optimization in varying tectonic environments. The projects build on work completed during my M.S. at UMass, which includes the development of the fracture modeling tool Growth by Optimization of Work (GROW) [McBeck et al., 2016]. GROW simulates fracture propagation, interaction and linkage by iteratively searching for fracture propagation paths that maximize the change in external work done on the system …

Kinematic, Metamorphic, And Geochronologic Constraints On The Evolution Of The Lhagoi Kangri Gneiss Dome, Southern Tibet: Insight Into Mid-Crustal Processes During Himalayan Orogenesis, Timothy Francis Diedesch

Doctoral Dissertations

The north Himalayan gneiss domes are a series of isolated structures in southern-central Tibet that expose middle crust and record an early history of deformation, metamorphism, and partial melting. The domes are windows into the processes and physical conditions that promoted growth and uplift of the Himalaya during the early stage of collision (Eocene to Miocene) between India and Asia. Mechanisms responsible for creating the north Himalayan gneiss domes are crucial to understanding the early tectonic evolution of large orogens, such as the Himalaya, particularly with respect to crustal rheology and how middle crust is exhumed in collisional settings. Models …

Metamorphic And Structural Control Of Magnetism Within The Lower Continental Crust, Northern Saskatchewan, Canada, Jeffrey R. Webber

Doctoral Dissertations

The linking of geophysical information to tectonometamorphic processes holds great potential for the surveying of vast remote areas of the planet and may allow for the transcendence of observational scales. Investigations concerning magnetic properties of the lower continental crust can reveal an incredible wealth of information concerning the conditions of metamorphism, regional extent of deformation, and controls on the magnetic architecture of the lithosphere. This dissertation presents three contributions aimed at the integration of petrology, structural geology, and rock magnetism in order to investigate the magnetic nature of the lower continental crust, constrain tectonometamorphic processes at the regional scale in …

Neoarchean Arc Magmatism, Subsequent Collisional Orogenesis, And Paleoproterozoic Disruption Within The Western Churchill Province: Implications For The Growth And Modification Of Lower Continental Crust, Sean P. Regan

Doctoral Dissertations

The growth and modification of continental lithosphere are fundamental geologic processes that have had a profound effect on Earth’s evolution. The lower continental crust can play a myriad of roles pertaining to these processes depending on the strength, age, temperature, and composition of the rocks present. However, the lower continental crust is impossible to sample in-situ, and thus observations of modern lower continental crust are limited to seismic studies and xenolith studies, which provide mere snap shots of the lower crust. High pressure granulite terranes provide 4 dimensional, and spatially resolvable, analogues of lower continental crust. The Athabasca granulite terrane …

Investigations Into The Tectonics Of Uranian And Saturnian Icy Satellites, Chloe Brett Beddingfield

Doctoral Dissertations

This dissertation reports a range of analyses of tectonic structures on various icy satellites and the implications of these analyses for each satellite’s geologic history. On Miranda, I tested the hypothesis that faults of the Arden Corona boundary and the 340º [degree] Chasma are listric in geometry. A listric fault geometry implies the presence of a subsurface detachment, which likely marked Miranda’s brittle-ductile transition (BDT) at the time of faulting. Results support the hypothesis for the Arden Corona boundary, although not for the 340˚ [degree] Chasma. Using the Arden Corona fault system geometry, the BDT depth, thermal gradient, and heat …

Geologic Investigations In The Central Georgia Inner Piedmont And The Western Flank Of The Carolina Superterrane: Implications Regarding Acadian And Alleghanian Collisional Orogenesis, Fault Reactivation, And The Mesozoic Breakup Of Pangea, Matthew Tiesher Huebner

Doctoral Dissertations

Detailed geologic mapping, U-Pb geochronology, igneous petrology and whole-rock geochemical analysis, and structural analysis of the Inner Piedmont and Carolina superterrane were conducted to better define the tectonic history of the southern Appalachian orogen; results yield implications for Acadian/Neoacadian and Alleghanian collisional events and Mesozoic breakup of Pangea. Detailed geologic mapping was focused in the Inner Piedmont at the northeastern end of the Pine Mountain window to investigate an aeromagnetic anomaly that was hypothesized to represent the southwestern continuation of the Brindle Creek fault, which separates the Inner Piedmont terranes (Tugaloo and Cat Square). Evidence supports this hypothesis, while contrasting …

Dome Formation During Crustal Extension In The Himalaya: Kinematic And Pressure-Temperature-Time-Deformation Constraints On Extensional Exhumation Along The Southern Margin Of The Tibetan Plateau, Jackie M. Langille

Doctoral Dissertations

The Himalaya and Tibetan Plateau were built by a combination of south-directed thrusting, north-directed extension, and generally east-west-directed extension within the Himalaya and Tibetan Plateau all to accommodate convergence between the Indian and Eurasian plates that began in the Eocene. Normal-sense shear zones that accommodate roughly east-west-directed extension across the southern margin of the Himalaya have exhumed young metamorphic domes across the Himalayan front. These metamorphic domes contain high-grade metamorphic rocks bound by normal-sense shear zones. The purpose of this study is to evaluate how these normal-sense shear zones develop and how they exhume metamorphic domes, which remains poorly understood …

Surface And Subsurface Structures Of The Western Valley And Ridge In Tennessee And Geometry And Kinematics That Permit Reconstruction Of The Tennessee Salient, Southern Appalachians, Jennifer Kathleen Whisner

Doctoral Dissertations

The southern and central Appalachian foreland fold-thrust belt comprises a series of orogen -scale curves that extend from Alabama to New York. One of these is the Tennessee salient, a foreland-convex curve that extends from Cartersville, Georgia, to Roanoke, Virginia. Development of a kinematic model for deformation in the salient has been hindered by a paucity of penetrative deformation in this generally low temperature, low volume-loss portion of the orogen.

Industry seismic reflection lines provide greater resolution of subsurface geometry of both the basement surface and the overlying fold-thrust belt, confirming some previous interpretations and changing others. A series of …