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The timing, duration, and pressure-temperature (P-T) conditions of metamorphism provide a direct record of the physical and chemical evolution of the crust and inform our knowledge and understanding of plate tectonics. The characteristic timescales and length-scales of metamorphism vary by orders of magnitude, depending on the driving tectonic process. Two fundamental problems with the retrieval of this information from the metamorphic rock record are insufficient temporal resolution and processes that overprint or obscure the full record of metamorphism. Understanding what processes are recorded, and why they are recorded, is critical for accurate models of tectonics. This dissertation examines these processes in the metamorphic rock record in two settings: the central Appalachian orogen and the Western Alps fossil subduction zone. Chapters 2 and 3 focus on poly-metamorphic migmatites from the Smith River Allochthon (SRA) in the central Appalachians. A combination of petrography, thermodynamic modeling, and geochemistry is used to document and quantify the metamorphic evolution of the SRA and determine the petrologic processes that control metamorphic re-equilibration in high-temperature metamorphic systems. Chapter 2 presents new constraints for Silurian high-temperature (~750℃, 0.5 GPa) contact metamorphism in response to mafic magmatism and a cryptic Alleghanian metamorphism (~600℃, 0.8 GPa). A combination of extensive and highly variable melt loss followed by H2O-flux melting during contact metamorphism is shown to produce a range of modified bulk rock compositions and domains with variable fertilities for metamorphic re-equilibration during the Alleghanian. In chapter 3, monazite, allanite, and zircon laser ablation split-stream petrochronology are used to constrain the timing of poly-metamorphism and develop a tectonic model for the SRA. The SRA preserves evidence for at least three orogenic events, each with a relatively short duration (< 10 Myr.), likely due to repeated magmatic heating. The full record of this punctuated heating is obscured by dissolution-reprecipitation reactions that variably recrystallize monazite and decouple trace element chemistry from isotopic age and significantly restrict equilibrium length-scales. Chapters 4 and 5 examine the dynamic interplay between transient fluid flow, episodic metamorphism, and deformation in subduction zones. In chapter 4, diffusional speedometry is applied to eclogite breccias from the Monviso ophiolite to quantify the periodicity of transient deformation and metamorphism at eclogite facies P-T conditions. The maximum timescale for repeated fracturing is constrained to ~1 Myr., likely caused by cyclic variations in fluid pressure and strain rate (not necessarily seismicity). While difficult to preserve and detect in the rock record, this periodic metamorphism may play an important role in detachment and exhumation processes in subduction zones worldwide. Finally, in chapter 4 a combination of thermodynamic modeling and Sm-Nd garnet geochronology are used to construct a model for subduction and exhumation of the Voltri ophiolite. Garnet growth occurs rapidly and close to peak P-T conditions (~520℃, 2.4 GPa) across the ophiolite, with large (>10 km2) areas preserving near-identical ages, suggesting that the Voltri ophiolite was exhumed as several large coherent units, aided by the presence of buoyant serpentinites. / Doctor of Philosophy / Metamorphism provides a direct record of the physical and chemical evolution of Earth's crust and informs our knowledge and understanding of how plate tectonics works on Earth. Differences in the physical conditions (e.g. pressure, temperature) and timescales of metamorphism can provide clues for the operation of unique tectonic processes, such as the intrusion and cooling of magma deep underground or the collision of two tectonic plates and formation of a mountain range. The key is to correctly "read" the metamorphic rock record. One inherent difficulty in reading and interpreting metamorphic rocks is that few current methods are able to resolve very short timescale events (much less that 1 million years (Myr.) in duration), such as earthquakes, in the rock record. Moreover, metamorphic rocks experience numerous distinct 'events', which partly overprint one another and produce a complicated and near impossible puzzle for geologists to unravel. Solving this puzzle is critical to fully understand how plate tectonics works on Earth. This dissertation addresses these problems and examines metamorphism in two locations: the core of the ancient supercontinent Pangea (central Appalachians) and a fossil subduction zone (the Western Alps). Chapters 2 and 3 focus on the central Appalachians. Chemical and textural analysis of metamorphic rocks are used to understand the major heat sources that operated in the crust during the formation of the Appalachians and determine the processes that control metamorphic re-crystallization at extremely high temperatures. Chapter 2 presents new constraints for high-temperature (~750℃) metamorphism in response to magmatic heating and provides evidence for a younger metamorphic event that is cryptically recorded. A combination of compositional changes caused by earlier high-temperature metamorphism and the later addition of water along reactive grain boundaries are shown to be important factors in the cryptic record of the younger metamorphic event. In chapter 3, U-Pb geochronology is used to the determine the timing of metamorphism and construct a tectonic model for the central Appalachians, which preserves evidence for at least three tectonic events over ~200 Myr, but with each occurring over a relatively short duration (< 10 Myr.). These events are interpreted to represent repeated magmatic heating 'pulses' during the formation of Pangea. However, the full record of this punctuated heating is partly obscured by subsequent fluid alteration. Chapters 4 and 5 examine the dynamic interplay between transient fluid flow, earthquakes, and metamorphism deep in subduction zones. In chapter 4, fracture sets within metamorphic garnet crystals from the French Alps (Monviso) are used to determine the timescale of repeated fracturing and recrystallization during subduction. The fracture timescales are estimated to be much less than 1 Myr. and are interpreted to record repeated fluid "pulses" and possibly deep earthquakes. While difficult to preserve and detect in the rock record, this process may play an important role in bringing metamorphic rocks back from deep in subduction zones to Earth's surface. In chapter 4, a combination of mineral chemistry and geochronology are used to construct a tectonic model for the subduction and exhumation of a portion of the Italian Alps (Voltri). Metamorphic reactions occur synchronously and immediately before exhumation across a wide area (> 10 km2). This suggest that large (> 10 km2) pieces of oceanic crust can metamorphose, detach, and exhume deep in subduction zones.

The Northern Highlands Terrane (NHT) in Scotland preserves a long record of metamorphism and convergent deformation related to several orogenic events that occurred from Neoproterozoic to Devonian time. Deconvolving the signatures of multiple tectonic events and determining the rates of metamorphism in settings like the NHT are important parts of better understanding the thermal and mechanical processes controlling convergent tectonics. I have used monazite-xenotime thermometry and geochronology, in conjunction with metamorphic petrology and additional accessory phase geochronology, to place constraints on the timing and rates of thermal metamorphism in a variety of structural settings throughout the NHT. Our data show that the ductile thrust nappes of northernmost Scotland preserve a record of Scandian (435-410 Ma) orogenesis. High grade metamorphism in the hinterland Naver nappe likely resulted from the widespread infiltration of granitic magmas at c. 425 Ma, which coincided with peak metamorphism. The timing of metamorphism in the hinterland Scandian thrust nappes is apparently younger than at least some deformation in the foreland Moine thrust zone, suggesting this orogenic wedge experienced large-scale out-of-sequence deformation and metamorphism. In contrast to the Scandian nappes, the Sgurr Beag nappe records primarily Precambrian metamorphism related to the Knoydartian orogeny (780-725 Ma). Additionally, monazite in the Sgurr Beag nappe preserves a record of widespread metasomatism and metamorphism at c. 600 Ma, possibly related to the break-up of Rodinia at that time. A potentially important heat source in orogenic systems, like those preserved in Scotland, is the thermal energy dissipated during deformation, otherwise known as shear heating. It is important to consider to how shear heating may contribute to metamorphism during orogenesis. This is challenging because there are few, if any, methods of relating observations from typical orogenic systems to magnitudes of shear heating. We have developed a model that is adaptable to a wide range of parameters that can be measured from naturally deformed rocks and places first-order constraints on magnitudes of shear heating. While our models suggest that shear heating is not particularly important in the NHT, in lower initial temperature mylonite zones shear heating could be more significant. / Doctor of Philosophy / The Northern Highlands Terrane (NHT) in Scotland preserves a long record of metamorphism and convergent deformation related to several orogenic events that occurred from Neoproterozoic to Devonian time. Understanding the record of each of these events and the rates at which metamorphic changes occurred is important for improving our understanding of the processes at work in continental collisions. The work presented in this thesis involves determining the temperatures recorded by metamorphic minerals and the ages of those minerals in order to reconstruct the temperature-time evolution of samples in a variety of positions within the NHT. Our data show that the collision and thermal metamorphism at 435-410 Ma is well preserved in northernmost Scotland. We argue that metamorphism in this area resulted from the widespread intrusion of hot magmas, which coincided in time with peak metamorphism. The timing of metamorphism in the core (hinterland) of this mountain belt is apparently younger than shallower deformation at the edges (foreland) of the mountain belt, suggesting active deformation and metamorphism retreated toward the hinterland during crustal shortening. In another part of the NHT, known as the Sgurr Beag nappe, a much older metamorphic event that occurred at 780-725 Ma is better preserved. In this area, the mineral monazite appears to record evidence of widespread fluid alteration at ~600 Ma, which has not previously been widely recognized in Scotland. A potentially important heat source in the Earth’s crust is shear heating associated with the thermal energy produced during deformation. It is important to consider what contribution shear heating may have made to the preserved metamorphic record in orogenic belts. This is challenging because there are few, if any, methods of relating observations from typical metamorphic rocks to estimated magnitudes of shear heating. We have developed a numerical model that is adaptable to a wide range of realistic natural scenarios and places first-order constraints on potential magnitudes of shear heating. While our models suggest that shear heating is not particularly important in the NHT, in some lower temperature fault zones shear heating could be more significant.

<p>U-Pb zircon datasets for Plutonic Clasts collected from conglomerate are presented first as a summary that includes sample name, GPS location, and datatables for each sample.</p> <p><br></p> <p>Additionally, raw datasets for each sample are included that includes detailed information on laser settings for each analyses</p> <p><br></p> <p>Note: Sample 062618WA-01 is included in one raw dataset as three igneous samples were analyzed on the same sample mount. This particular sample is a bedrock sample. Use caution</p> <p><br></p> <p>All analyses were completed at the University of Arizona Laserchron Center (NSF-EAR 1649254)</p>

<p>This dataset includes a summary excel file that details all the datatables for each detrital zircon sample and their location relative to each site and depth collected.</p> <p><br></p> <p>In addition to this summary, raw datasets for each individual analyses is included that have detailed information regarding the laser settings used for analyses.</p> <p><br></p> <p>All datasets were analyzed at the University of Arizona LaserChron Center (NSF-EAR 1649254)</p>

Submitted by Jordan (jordanbiblio@gmail.com) on 2016-10-19T14:49:06Z No. of bitstreams: 1 DISS_2015_Shayenne Fontes Nogueira.pdf: 6085146 bytes, checksum: 0c934cfd81d96aa21aaed95906de3b37 (MD5) / Approved for entry into archive by Jordan (jordanbiblio@gmail.com) on 2016-10-19T14:50:04Z (GMT) No. of bitstreams: 1 DISS_2015_Shayenne Fontes Nogueira.pdf: 6085146 bytes, checksum: 0c934cfd81d96aa21aaed95906de3b37 (MD5) / Made available in DSpace on 2016-10-19T14:50:04Z (GMT). No. of bitstreams: 1 DISS_2015_Shayenne Fontes Nogueira.pdf: 6085146 bytes, checksum: 0c934cfd81d96aa21aaed95906de3b37 (MD5) Previous issue date: 2015-08-31 / CNPq / O Terreno Rio Apa é marcado por uma história evolutiva complexa e ainda contêm problemáticas a serem estudadas e compreendidas. Neste trabalho são apresentados os resultados obtidos a partir da caracterização petrológica do Granito Aquidabã que pertence à Suíte Intrusiva Alumiador inserida no Arco Magmático Amoguijá deste terreno. Em um contexto anterior, as rochas deste granito eram descritas como pertencentes ao Batólito Alumiador, porém, as mesmas apresentam características singulares que levaram à sua individualização. O Granito Aquidabã está representado por rochas plutônicas e efusivas, de natureza ácida. São classificadas como dacitos e riolitos, riolitos/riolitos alcalinos e adamelitos (monzogranitos)/granitos, subdivididos em três fácies petrográficas: Granito Gráfico (fácies 1), Subvulcânicas Dacítica-Riolítica (fácies 2), Microgranito (fácies 3). A primeira é, volumetricamente, dominante no corpo mapeado sustentando as partes mais elevadas, e disposta na porção central da Serra da Alegria; caracteriza-se por rochas maciças e de cor rosa a rosa-acinzentado, leucocráticas, equi- a inequigranulares média a fina. A fácies 2 é caracterizada pela ocorrência de litotipos que variam de dacitos a riolitos.Os dacitos apresentam-se marrom-acinzentado, com textura porfirítica, destacando fenocristais de plagioclásio e quartzo, por vezes com dimensões entre 1 e 7 mm apresentando, comumente, feições de corrosão magmática como golfos e embaiamentos, envoltos por uma matriz felsítica cinza. Os riolitos são rosa-acinzentado, maciços, afaníticos, com variedades porfiríticas, apresentando fenocristais de feldspato alcalino com tamanhos entre 1 e 5 mm envoltos por uma franja esferulítica de composição quartzo+K-feldspato. A fácies Microgranito (fácies 3) é a de menor representatividade, sendo encontrada nas bordas oeste e sudoeste do corpo granítico, caracterizada por rochas maciças cinza-claro, inequigranulares fina a muito fina. Os dados geoquímicos sugerem um magmatismo de composição compatível com a de granitoides tipo A gerados em ambiente de arco magmático, em período pós-tectônico. Através do método geocronológico U-Pb (SHRIMP) em zircão se obteve idade de 1811±6,8 Ma para o Granito Aquidabã, com valores εNd (1,81Ga) de -2,18; -4,37 e -1,50, e idade modelo TDM de 2,35, 2,57 e 2,26 Ga que apontam para participação de uma fonte crustal na origem do magma, possivelmente envolvendo processos de fusão parcial de uma crosta continental neoarqueana a paeloproterozoica na geração do granito. Os resultados obtidos apontam que o Granito Aquidabã corresponde a um magmatismo desenvolvido no final do Orosiriano no Arco Magmático Amoguijá. / The Rio Apa Terrane is marked by a complex evolutionary history and still contain issues to be studied and understood. This paper presents the results obtained from the petrologic characterization of Aquidabã granite belonging to Intrusive Suite Alumiador inserted into the Magmatic Arc Amoguijá. In a previous context, this granite rocks were described as belonging to the Batholith Alumiador, however, they present unique characteristics that led to its individualization. The Aquidabã Granite is represented by plutonic and effusive rocks, acidic in nature. They are classified as dacites and rhyolites, rhyolites / alkaline rhyolites and adamelitos (monzogranites) / granite, divided in three petrographic facies: Graphic Granite (facies 1), Subvolcanic Dacitic-Riolítica (facies 2), Microgranito (facies 3). The first is volumetrically dominant in the body, arranged in the central portion of the Serra da Alegria; It characterized by massive rocks and pink , pink-gray, leucocratic, inequigranular thin.The facies 2 is characterized by the occurrence of rock types ranging from the dacites, dacites/riolitos. Have color grayish to brown, with phenocrysts of quartz and plagioclase, sometimes with dimensions between 1 and 7 mm, presenting features magmatic corrosion as gulfs and embayments, surrounded by a gray matrix felsítica.The rhyolites are pink-gray, massive, afaníticos with porphyritic varieties, with phenocrysts of alkali feldspar with sizes between 1 and 5 mm surrounded by a fringe spherulitic quartz K-feldspar + composition. The Microgranito facies (facies 3) is the smaller representation, found in the western and southwestern edges of the granite body, characterized by light gray massive rocks, thin inequigranular very thin. The geochemical data suggest a composite magmatism compatible with the granitic type A generated in magmatic arc environment in post-tectonic period. Through the method geochronological U-Pb (SHRIMP) was obtained zircon age ± 6.8 1811 Ma to Aquidabã Granite with εNd values (1,81Ga) of -2.18; -4.37 And -1.50, and TDM model age of 2.35, 2.57 and 2.26 Ga pointing to involvement of a crustal magma source in origin, possibly involving partial melting processes of continental crust neoarqueana the paeloproterozoica in granite generation. The results suggest that the Aquidabã Granite corresponds to a magmatism developed in the late Orosirian in Magmatic Arc Amoguijá.

Submitted by Jordan (jordanbiblio@gmail.com) on 2016-10-21T11:39:58Z No. of bitstreams: 1 DISS_2015_Leticia Alexandre Redes.pdf: 8294298 bytes, checksum: 8db7bb3276d8fbf7eb60e5f07cf9aec7 (MD5) / Approved for entry into archive by Jordan (jordanbiblio@gmail.com) on 2016-10-21T11:40:54Z (GMT) No. of bitstreams: 1 DISS_2015_Leticia Alexandre Redes.pdf: 8294298 bytes, checksum: 8db7bb3276d8fbf7eb60e5f07cf9aec7 (MD5) / Made available in DSpace on 2016-10-21T11:40:54Z (GMT). No. of bitstreams: 1 DISS_2015_Leticia Alexandre Redes.pdf: 8294298 bytes, checksum: 8db7bb3276d8fbf7eb60e5f07cf9aec7 (MD5) Previous issue date: 2015-02-13 / CAPES / O Granito Taquaral possui dimensões batolíticas, localiza-se no sul do Cráton Amazônico, na região de Corumbá, extremo ocidente do estado de Mato Grosso do Sul, próximo ao limite Brasil-Bolívia, sendo parcialmente recoberto pelas rochas sedimentares das formações Urucum, Tamengo, Bocaina e Pantanal e pelas as Aluviões Atuais. Com base no estudo das rochas do Granito Taquaral a partir de granulação, cor e composição, juntamente com o mapeamento geológico de detalhe, foi realizada a identificação de três fácies petrográficas: Fácies Média a Grossa Cinza, Fácies Grossa Rosa e Fácies Fina Rosa. A primeira é, volumetricamente, dominante no corpo mapeado; caracteriza-se por rochas leucocráticas, de cor cinza, textura inequi a equigranular média a grossa, às vezes, mostra-se milonitizada e são classificadas como quartzo-monzodiorito, granodiorito e monzogranito. A segunda é constituída por rochas leucocráticas de cor rosa, inequigranulares, grossas, de composição quartzo-monzonito e monzogranito. Enquanto que a terceira é composta por rochas hololeucocráticas de cor rosa-claro, equi a inequigranulares classificadas como monzo a sienogranítica, de granulação fina e representadas por diques aplíticos. Localmente são encontrados dois tipos de enclaves de natureza e origens diferentes, um de composição máfica, corresponde a xenólito e outro, identificado como Enclave Microgranular Félsico. Na área de estudo são encontrados, também diques de diabásio sempre em contatos abruptos com o granito. Foram identificadas duas fases deformacionais, uma de natureza dúctil (F1) e outra rúptil/rúptil-dúctil (F2). Os dados geoquímicos indicam composição intermediária a ácida para essas rochas e sugerem sua colocação em ambiente de arco, representando um magmatismo cálcio-alcalino de médio a alto-K, metaluminoso a peraluminoso. Através do método geocronológico U-Pb (SHRIMP) em zircão se obteve idade de 1861±5,3 Ma para sua cristalização. Análises Sm-Nd em rocha total fornecem valores de εNd(1,86 Ga) de -1,48 e -1,28 e TDM de 2,32 e 2,25 Ga apontando para uma provável fonte crustal riaciana. Os resultados obtidos apontam que o Granito Taquaral corresponde a um magmatismo desenvolvido no final do Orosiriano no Arco Magmático Amoguijá. / The Taquaral Granite comprises an intrusion of batholithic dimensions, located in the south of the Amazon Craton in Corumbá region - far west of the state of Mato Grosso do Sul, near the border between Brazil and Bolivia -, partially covered by sedimentary rocks of the Urucum, Tamengo, Bocaina and Pantanal formations and the Alluvial Deposits. Based on grain size, color, and composition along with detailed geological mapping, three petrographic facies are attributed to the rocks of Taquaral Granite: Medium to Coarse-grained Grey Facies, Coarse-grained Pink Facies and Fine-grained Pink Facies. The first facies is volumetrically dominant in the mapped body; characterized by leucocratic rocks, grey, inequigranular to equigranular medium-to-coarse grained, sometimes displaying a mylonitized texture and are classified as quartz-monzodiorite, granodiorite and monzogranite. The second facies consists of pink leucocratic rocks, inequigranular, coarse-grained, of quartz monzonite and monzogranite composition. In turn, the third facies consists of light-pink hololeucocratic rocks, equigranular to inequigranular, classified as fine-grained aplite dykes of monzogranitic to syenogranitic composition. Two different types of enclaves are locally found: one corresponds to a mafic xenolith; another is identified as felsic microgranular enclave. In the study area, diabase dikes are also found, always in direct contact with the granite. Two deformation phases are identified, one of ductile behaviour (F1) and another of brittle / ductile brittle behaviour (F2). Geochemical data indicate intermediate to acid composition for these rocks and suggest an arc environment, representing a medium to high-K calc-alkaline magmatism, metaluminous to peraluminous. SHRIMP U-Pb zircon ages of 1861 ± 5.3 Ma are attributed to crystallization. Sm-Nd whole rock analyses provided negative εNd(1.86 Ga) values (-1.48 and -1.28) and TDM model ages from 2.32 to 2.25 Ga indicating a Rhyacian crustal source. The results indicate that Taquaral Granite is an evidence of a magmatism developed in the Amoguijá Magmatic Arc in late Orosirian.