Io, the most volcanically active body in the solar system, also has some of the tallest and steepest mountains. The mountains seem to be tectonic in origin, yet the methods of their formation have not been decisively constrained and their associations with volcanic paterae are yet unclear. We have compiled global spatial statistics on mountain dimensions and orientations, lineations attributed to structures, straight patera margins, and patera dimensions in order to better define their genetic relationships and the mechanisms forming each type of feature. Additionally, we have produced 4 regional structural maps of mountain complexes and have proposed tectonic histories. Global statistics show that paterae and mountains and their associated lineations are more common at low latitudes and that lineations attributed to tectonics have preferred azimuths of 45° and 135°, whereas straight patera margins and azimuths appear more random. Additionally, tectonic lineations tend to cluster to those of similar types and are smaller when closer together. Mountains in general on Io are isolated, varied in size and shape, and have no significant geographic patterns in those variations. These results may indicate that global-scale processes are involved in forming Io's tectonic structures, but that the diversity of mountain characteristics and the collapse of paterae adjacent to mountain complexes may be more regionally controlled. Mapping of the Hi'iaka, Shamshu, Tohil, and Zal regions has shown that Io's mountains reside in large, faulted-bounded crustal blocks, which have undergone modification through local responses of subsurface structures. Strike-slip motion along reactivated faults has led to the formation of both transpressional and transtensional features, creating tall peaks and low basins, some of which are now occupied by paterae. Subsurface structures play a large role in Io's mountain diversity. Based on interpretation of statistical results and on our localized mapping, we propose that Io's mountains result from a combination of crustal stresses involving both global and local-scale processes. Multiple faults and fractures in a variety of orientations formed in Io's lithosphere, created over billions of years by stresses imposed by volcanic loading and tidal flexing. These faults have been progressively buried over time under multiple layers of volcanic material. Stresses continuing from loading and tidal massaging sometimes occur at oblique angles to pre-existing faults, reactivating them as reverse, normal, or strike-slip faults. Because of this, large, cohesive fault-bounded blocks have undergone both transpressional and transtensional modification. Further degradation of mountains has also occurred from extensive mass wasting, gravitational collapse, and erosion by sublimation and sapping of sulfur-rich layers within the crust. This model of fault-bounded blocks being modified by continual stresses and local structural response accounts for the variation and patterns of mountain sizes, shapes, and orientations, along with their isolation and interactions with other features. It presents an explanation for the influence of global and regional tectonics and a more detailed account of the formation of some of Io's remarkable mountains.

A lingering question in Cordilleran tectonics is how high plateaus form in the absence of continental collision. The type example of an active Cordilleran high plateau is found in the Central Andes of Peru, Bolivia, Argentina, and Chile. Along this section of the South American Cordillera, tectonics are primarily driven by subduction of the oceanic Nazca Plate beneath the continental South American Plate. Extending over 1,800 km along the active continental margin, the Central Andean Plateau (CAP) reaches a maximum width of around 400 km with several peaks in excess of 6 km. Numerous morphotectonic subdivisions of the CAP highlight the complex along-strike variability of the Plateau providing a natural laboratory for investigating the relative contribution of tectonic processes involved in building and maintaining Cordilleran high plateaus. The scale of this problem extends far beyond the scope of any one geoscientific discipline requiring a multidisciplinary approach. Our contribution to this scientific problem and the focus of the work presented in this dissertation is to better understand the current lithospheric and uppermost mantle structure along the CAP. This is achieved by integrating recent advances in seismic imaging techniques with a growing availability of high-quality seismic data into three distinct studies across the South American continent. In the first study, we present a shear-wave velocity model for the crust below the Altiplano-Puna Volcanic Complex (APVC). The target of this study is to constrain the crustal volume of a large magma reservoir inferred to exist below the APVC. When combined with geological and petrological constraints, the large-volume magma reservoir imaged in this study suggests a significant magmatic contribution to the growth of the Plateau in excess of one kilometer over the last ten million years. In addition to the tectonic contributions of this work, we introduce a new method of jointly inverting surface-wave dispersion data and receiver functions to generate a three-dimensional velocity model. In the second study, we combine Rayleigh-wave dispersion data from ambient noise and earthquake-generated surface waves to invert for a shear-wave velocity model of the lithosphere and uppermost mantle below the Bolivian Orocline. The target of this study is to identify any possible mantle contributions to the uplift history along the northern CAP. The highlight of this study is a high-velocity feature that extends from the base of the crust to ~120 km depth below the Altiplano basin. We interpret this feature using a simple isostatic model and suggest it is responsible for the relatively low topography of the Altiplano basin. In the third and final study, we extend the seismic model of the APVC crust to cover the entire Puna Plateau (southern CAP). The target of this study is to assess the uniqueness of the APMB and to look for additional magma reservoirs in the crust. A highlight of this work is the nearly one-to-one spatial correlation between the long-wavelength topography, ignimbrite deposits, long-wavelength Bouguer gravity anomalies, and four additional mid-crustal low-velocity zones imaged in the southern Puna Plateau. When placed in the context of existing geological and petrological constraints, we suggest the contribution of magmatic addition as an uplift mechanism in Cordilleran systems is much larger than is currently accepted.

The Beyşehir-Hoyran-Hadim Nappes crop out over 700km, from east to west in the Pisidian and Central Taurus Mountains of southern Turkey. During this study, field obsevations of lithological, structural and sedimentological features are combined with igneous geochemical data derived from samples collected to help redefine a series of tectono-stratigraphic units and also determine the origin of the Beyşehir-Hoyran-Hadim Nappes. Above a regionally autochthonous Tauride carbonate platform, the Beyşehir-Hoyran Nappes begin with Ophiolitic Melange, consisting of blocks of neritic and pelagic limestone, basalt, serpentinite, radiolarian chert and, in places, amphibolite-grade metamorphic sole-type rocks, together set in a highly sheared siltstone and mudstone matrix. Locally, large slices of serpentinized harzburgite are incorporated in the melange. The peridotite sheets include lenses of chromitite and dunite and are cut by a series of dolerite dykes. The higher thrust sheets in the Hadim area begin with the Korualan Unit; a thrust sheet (ca. 400m thick) of mainly redeposited carbonates, quartzose sandstones and mudstones of Mid-Late Triassic age, interpreted as a proximal slope/base-of-slope succession. Regionally above is the Huğlu-type Unit; a thrust sheet (ca. 1 km thick) of Mid-Late Triassic intermediate-acidic extrusives, volcaniclastics and minor pelagic carbonates, interpreted as a continental rift. Post-rift subsidence in this thrust sheet is recorded by thin (<100m thick) Upper Triassic-Upper Cretaceous pelagic carbonate and radiolarian chert, depositionally above. The uppermost thrust sheet, the Boyali Tepe-type Unit, comprises broken formation and melange, including Jurassic shallow-water carbonate, Ammonitico Rosso condensed pelagic limestone, radiolarian chert and Upper Cretaceous pelagic limestone, representing a Bahaman-type carbonate platform which subsided in Early Jurassic time. Anastomosing zones of tectonic-sedimentary melange separate these higher units. The Beyşehir-Hoyran Nappes document Triassic rifting and Jurassic-Cretaceous passive margin subsidence bordering the Northern Neotethyan Ocean. The Late Cretaceous harzburgitic ophiolite probably formed above a northerly dipping subduction zone within the Neotethyan ocean basin. Ophiolitic melange formed along the leading edge of the overiding plate. The ophiolite was emplaced southwards onto the northern margin of the Tauride platform in latest Cretaceous time, probably during collision of the passive margin with a trench. The nappe pile and underlying platform (Hadim Nappe) were thrust ca. 150km further south in Late Eocene time during regional continental collision and suture zone tightening. Several alternative palaeo-tectonic models are considered and tested in the light of data presented from this study. Assuming ‘in-sequence’ thrusting, the Beyşehir-Hoyran Nappes restore to a location north of a northerly Neotethyan spreading axis. More probably, they originated near the south margin of the northern Neotethys, but reached their position by ‘out-of-sequence thrusting’. Formation within a localised southerly strand of the northern Neotethys (Inner Tauride ocean) is more probable than within the main Neotethys further north. Wider implications for the Tethyan ocean as a whole and several other orogenic belts are also considered.

This study utilizes new geochemical analyses of fluids (formation water and gas) collected predominately from Devonian organic-rich shales and reservoir sandstones from the northern Appalachian Basin margin to investigate basin scale hydrologic processes, water-rock reactions, microbial activity, and natural gas generation. Elemental and isotopic composition of co-produced formation waters and natural gas show that the majority of methane in Devonian organic-rich shales and reservoir sandstones is thermogenic in origin with localized accumulations of microbial gas. Microbial methanogenesis appears to be primarily limited by redox buffered conditions favoring microbial sulfate reduction. Thermal maturity (bioavailability) of shale organic matter and the paucity of formation waters may also explain the lack of extensive microbial methane accumulations. Iodine and strontium isotopes, coupled to elemental chemistry demonstrate basin scale fluid flow and clay mineral diagenesis. Evidence for this is based on anomalously high ¹²⁹I/I values sourced from uranium deposits (fissiogenic production of ¹²⁹I) at the structural front of the Appalachian Basin. Radiogenic ⁸⁷Sr/⁸⁶Sr (up to 0.7220), and depleted boron and potassium concentrations support smectite clay diagenesis at temperatures greater than 120 °C. The development of fissiogenic ¹²⁹I as a tracer of basin scale fluid flow is a novel application of iodine isotopes provided that the sources of cosmogenic and anthropogenic ¹²⁹I are reasonably well constrained. The anomalously high ¹²⁹I/I in Appalachian Basin brines may be alternatively explained by microbial fractionation based on a correlation with decreasing δ¹³C-DIC values and decreasing sulfate concentrations in the range of sulfate reduction. These results demonstrate that the microbial fractionation of iodine isotopes may be possible and an important consideration when interpreting ¹²⁹I/I, regardless of the source of ¹²⁹I. Results from this study have important implications for understanding the controls on and origins of natural gas production in sedimentary basins; tectonically and topographically driven basin scale fluid flow, including diagenetically induced waterrock reactions and mineral ore deposition related to orogenesis; and an improvement of the use of iodine isotopes for understanding large scale fluid flow, and possibly its use as a tracer of organic matter diagenesis and the distribution of radionuclides in the environment.

A região de Gondola-Nhamatanda localiza-se na parte limítrofe entre as províncias de Manica e Sofala, centro de Moçambique. Ela está geologicamente inserida no complexo de Bárue (Grupo de Chimoio) e na cobertura fanerozoica. O Complexo de Bárue é composto pelos Grupos supracrustais de Macossa e Chimoio intrudidos por rochas plutônicas de várias composições. Enquanto que a cobertura fanerozoica consiste de sedimentos terrestres e rochas vulcânicas associadas pertencentes ao Supergrupo do Karoo e à sequências do rifte Este Africano. A área de trabalho foi estudada em termos de petrografia; geoquímica de elementos maiores, traço e de terras raras; geocronologia e geologia isotópica pelos métdos U -Pb em zircão, Rb-Sr e Sm-Nd em rocha total e Rb-Sr em minerais para o granito de Inchope, quartzo-sienito do monte Chissui e fonolito do monte Xiluvo. Este estudo permitíu determinar os litotipos que intrudiram o grupo supracrustal de Chimoio , suas idades de cristalização e de diferenciação dos magmas que formaram seus protólitos e ainda o enquadramento tectônico. As rochas estudadas são basicamente calci -alcalinas com variações de meta à peraluminoso para os granitoides e quartzo-sienito e peralcalino para o fonolito do monte Xiluvo. Os granitoides do grupo de Chimoio foram cristalizados no Mesoproterozoico (idades U-Pb e Rb-Sr) a partir de protólitos Paleoproterozoicos (\'T IND.DM\' = 1,7 - 2,3 Ga); por sua vez, as rochas vulcânicas (fonolitos) do monte Xiluvo cristalizaram rápidamente no Câmbrico (idade Rb-Sr) dum protólito do Neoproterozoico-Câmbrico (\'T IND.DM\' = 0,54 - 0,56 Ga). Os dados isotópicos obtidos no presente estudo sugerem que as rochas do cinturão de Moçambique foram geradas por fusão parcial que provavelmente envolveu mistura ( valores negativos de ?Nd ) da crosta arqueana / paleoproterozoica e magma mesoproterozoico a 1100 Ma e sofreram retrabalhamento marcado pela aglutinação do Gondwana (orogenia Pan-Africana) e tafrogênese marcada pela fraturação do Gondwana (Rifte Este Africano ). / The region of Gondola-Nhamatanda is located at the border between the provinces of Manica and Sofala, central part of Moçambique. It is geologically inserted in the Bárue complex and the Phanerozoic cover. The Bárue complex is composed of the Macossa and Chimoio supracrustal groups intruded by plutonic rocks of various compositions, whereas the Phanerozoic cover consists of terrestrial sediments and volcanic rocks belonging to the Karoo Super-group and East African Rift Sequences. The work area was studied in terms of petrography; geochemistry of major elements, trace and rare earth elements; geochronology and isotope geology by the methods U -Pb in zircon, Rb-Sr and Sm-Nd in whole rock and Rb-Sr in minerals for the Inchope granite, Chissui mountain Quartzo-sienito and Xiluvo mountain phonolite. This study allowed to determine the lithotypes that intruded the Chimoio supracrustal group, its crystallization ages and the differentiation ages of the magmas that formed the protoliths and the tectonic framework. The studied rocks are basically calc-alkaline varying from meta to peraluminous for the granitoids and quartz-sienite and peralkaline for the mount Xiluvo phonolite. The Chimoio Group granitoids had been crystallized in the Mesoproterozoic (U-Pb and Rb-Sr ages) from Paleoproterozoic protoliths (\'T IND.DM\' = 1.7 - 2.4Ga); on the other hand, the volcanic rocks (phonolites) of the Xiluvo mount had crystallized fast in the Cambrian (Rb-Sr age) from a Neoproterozoic-Cambrian protolith (\'T IND.DM\' = 0.54 - 0.56Ga). The isotopic data, in the present study , suggest that the rocks of the Mozambique belt had been generated by partial melting that probably involved the mixture of the archean/paleoproterozoic crust and the Mesoproterozoic magma at 1100Ma and had suffered reworking marked by the Gondwana amalgamation (Pan-African orogeny) and extensional processes marked by the Gondwana break up (East African Rift).

A região de Gondola-Nhamatanda localiza-se na parte limítrofe entre as províncias de Manica e Sofala, centro de Moçambique. Ela está geologicamente inserida no complexo de Bárue (Grupo de Chimoio) e na cobertura fanerozoica. O Complexo de Bárue é composto pelos Grupos supracrustais de Macossa e Chimoio intrudidos por rochas plutônicas de várias composições. Enquanto que a cobertura fanerozoica consiste de sedimentos terrestres e rochas vulcânicas associadas pertencentes ao Supergrupo do Karoo e à sequências do rifte Este Africano. A área de trabalho foi estudada em termos de petrografia; geoquímica de elementos maiores, traço e de terras raras; geocronologia e geologia isotópica pelos métdos U -Pb em zircão, Rb-Sr e Sm-Nd em rocha total e Rb-Sr em minerais para o granito de Inchope, quartzo-sienito do monte Chissui e fonolito do monte Xiluvo. Este estudo permitíu determinar os litotipos que intrudiram o grupo supracrustal de Chimoio , suas idades de cristalização e de diferenciação dos magmas que formaram seus protólitos e ainda o enquadramento tectônico. As rochas estudadas são basicamente calci -alcalinas com variações de meta à peraluminoso para os granitoides e quartzo-sienito e peralcalino para o fonolito do monte Xiluvo. Os granitoides do grupo de Chimoio foram cristalizados no Mesoproterozoico (idades U-Pb e Rb-Sr) a partir de protólitos Paleoproterozoicos (\'T IND.DM\' = 1,7 - 2,3 Ga); por sua vez, as rochas vulcânicas (fonolitos) do monte Xiluvo cristalizaram rápidamente no Câmbrico (idade Rb-Sr) dum protólito do Neoproterozoico-Câmbrico (\'T IND.DM\' = 0,54 - 0,56 Ga). Os dados isotópicos obtidos no presente estudo sugerem que as rochas do cinturão de Moçambique foram geradas por fusão parcial que provavelmente envolveu mistura ( valores negativos de ?Nd ) da crosta arqueana / paleoproterozoica e magma mesoproterozoico a 1100 Ma e sofreram retrabalhamento marcado pela aglutinação do Gondwana (orogenia Pan-Africana) e tafrogênese marcada pela fraturação do Gondwana (Rifte Este Africano ). / The region of Gondola-Nhamatanda is located at the border between the provinces of Manica and Sofala, central part of Moçambique. It is geologically inserted in the Bárue complex and the Phanerozoic cover. The Bárue complex is composed of the Macossa and Chimoio supracrustal groups intruded by plutonic rocks of various compositions, whereas the Phanerozoic cover consists of terrestrial sediments and volcanic rocks belonging to the Karoo Super-group and East African Rift Sequences. The work area was studied in terms of petrography; geochemistry of major elements, trace and rare earth elements; geochronology and isotope geology by the methods U -Pb in zircon, Rb-Sr and Sm-Nd in whole rock and Rb-Sr in minerals for the Inchope granite, Chissui mountain Quartzo-sienito and Xiluvo mountain phonolite. This study allowed to determine the lithotypes that intruded the Chimoio supracrustal group, its crystallization ages and the differentiation ages of the magmas that formed the protoliths and the tectonic framework. The studied rocks are basically calc-alkaline varying from meta to peraluminous for the granitoids and quartz-sienite and peralkaline for the mount Xiluvo phonolite. The Chimoio Group granitoids had been crystallized in the Mesoproterozoic (U-Pb and Rb-Sr ages) from Paleoproterozoic protoliths (\'T IND.DM\' = 1.7 - 2.4Ga); on the other hand, the volcanic rocks (phonolites) of the Xiluvo mount had crystallized fast in the Cambrian (Rb-Sr age) from a Neoproterozoic-Cambrian protolith (\'T IND.DM\' = 0.54 - 0.56Ga). The isotopic data, in the present study , suggest that the rocks of the Mozambique belt had been generated by partial melting that probably involved the mixture of the archean/paleoproterozoic crust and the Mesoproterozoic magma at 1100Ma and had suffered reworking marked by the Gondwana amalgamation (Pan-African orogeny) and extensional processes marked by the Gondwana break up (East African Rift).

Na porção W-SW do lobo Guaxupé, pertencente à Nappe Socorro-Guaxupé, nos arredores da cidade de São José do Rio Pardo, é registrado um evento metamórfico e anatético de fácies granulito, sob condições de desidratação da hornblenda, com T >=850ºC. As rochas diatexíticas, que compõem as suítes São José do Rio Pardo (SJRP) e Pinhal, resultam desse evento de alta temperatura, ocorrido há ~625 Ma. As assinaturas geoquímicas e isotópicas sugerem uma geração a partir da anatexia da crosta continental inferior. Além disso, o enriquecimento em potássio da suíte SJRP indica uma afinidade vaugnerítica, a qual é caracterizada por altos conteúdos de Mg, elementos do tipo LILE (large ion lithophile elements), HFSE (high field strenght elements) e ETR-leves, além de valores negativos de \'épsilon\'Nd e razões de Sr iniciais baixas, ~0.706. O magmatismo vaugnerítico implica em um manto litosférico metassomatizado como fonte, o qual foi enriquecido por eventos de subducção precedentes. A presença de pseudomorfos de fusão nesses diatexitos indicam uma evolução quase isotérmica sob presença de líquido anatético. O transporte sin-magmático ocorreu para NE-E. A fonte de calor para esse metamorfismo pode estar associada à delaminação da base do arco magmático. O processo de fusão parcial gerou leucossomas charno-enderbíticos na Unidade Metatexítica, com assinaturas geoquímicas e isotópicas que indicam uma fonte crustal. Dessas rochas, foram separados cristais de zircão que mostraram duas populações distintas. A primeira, tipicamente com cristais prismáticos e bipiramidados, indicam idades em torno de 620 Ma, enquanto que a segunda, com cristais isométricos típicos de alto grau metamórfico, indicam idades em torno de 610 Ma. Em relação ao pico metamórfico de ~625 Ma, as idades mais jovens obtidas sugerem um período de 15 my em que predominaram altas temperaturas. O transporte tectônico para NW, em estado sólido de alta temperatura, é posterior à cinemática sin-magmática para NE, e deve estar associado à compressão da placa superior convergente, dentro desse período de alta temperatura. Esse regime tectônico é compatível com modelos recentes da tectônica Andina onde é descrita uma subducção horizontal (Pampean flat subduction). Dentre as rochas da Unidade Granulítica Basal, também submetida à fusão parcial por desidratação da hornblenda, ocorrem gnaisses com afinidade adakítica, sugerida pelas altas razões Sr/Y = 72.73, La/Yb = 23.07, \'(La/Yb) IND.N\' = 15.56, e teores de #mg = 51.77, Sr = 1062 ppm, Cr = 197 ppm e Ni = 103 ppm. Tal afinidade sugere magmas resultantes da fusão de um slab em subducção. A Nappe Socorro-Guaxupé admite uma evolução que se inicia, cerca de 670-640 Ma, com uma subducção inclinada para a geração de rochas cálcio-alcalinas com alguns membros adakíticos. É seguido um momento de colisão, entre 625 e 610 Ma, com a geração de rochas diatexíticas e metatexíticas de alto potássio, onde o arco migrou primeiramente para o ante-arco (estado subsólido) e depois em direção ao interior da placa superior (estado sólido). A estabilização da nappe se deu quando da colocação dos maciços sieníticos pós-tectônicos, Capituva e Pedra Branca. / The W-SW portion of the Guaxupé Domain, nearby the São José do Rio Pardo city, records a granulite facies anatetic event under hornblende dehydration-melting conditions, i.e. T >=850ºC. The diatexitic rocks that are comprised within the São José do Rio Pardo and Pinhal suites resulted from this high-T metamorphic event, ca. 625 Ma. Geochemical and isotopic signatures suggest derivation from the lower continental crust. The K-rich SJRP suite also show geochemical affinity with vaugneritic rocks, suggested by high contents of Mg, LILE, HFSE and light-REE in addition to negative ?Nd and low Sr initial ratio (~0.706). Vaugneritic magmatism implies on a derivation from a metasomatized lithospheric mantle source enriched before partial melting in a previous subduction setting. Once both suites contain melt pseudomorphs, it is then suggested and isothermic evolution under the presence of melt. A syn-magmatic driven transport occurred towards NE-E, and the heat source for high-T conditions could be assigned to mantle delamination under the margmatic arc. Within the Metatexitic Unit, partial melting resulted in charno-enderbitic leucosomes whose geochemical and isotopic signatures indicate crustal sources. From these leucosomes, two different populations of zircon crystals were separated. The first, comprising bypiramidal-prismatic grains, yield ages around 620 Ma, whereas the second typology of zircons is isometric and soccer-ball type, yielding younger ages around 610 Ma. The latter typology is typical of high-T and melt-bearing rocks. Considering the 625 Ma metamorphic peak, the younger ages suggest a 15 my period when high-T conditions prevailed. Top-to-NW transport, under solid-state high-T conditions, can be associated to the compression of the upper convergent plate within this high-T period. Textural features suggest this transport to have occurred after the crystallization of the syn-magmatic rocks. The compression of the upper plate resembles recent models of the Andean orogenic cycle, where the Pampean flat subduction is described. Among the rocks of the Basal Granulitc Unit, which also underwent hornblende-dehydration partial melting, a gneissic rock shows adakitic affinity, suggested by Sr/Y = 72.73, La/Yb = 23.07, \'(La/Yb) IND.N\' = 15.56, #mg = 51.77, Sr = 1062 ppm, Cr = 197 ppm and Ni = 103 ppm. Adakitic magmas are thought to be slab melts. The Socorro-Guaxupé Nappe was built up between 670 and 640 Ma with a steep subduction and generation of calc-alkaline and subordinate adakitic rocks. A collisional setting, generating high-K diatexites and metatexites, took place between 625 and 610 Ma, where the arc firstly migrated (in subsolidus state) towards the forearc and then migrated (in solid state) towards the interior of the upper plate. Post-tectonic Capituva and Pedra Branca syenitic plutons intruded around 610 Ma, recording the arc migration ceasing.

Na porção W-SW do lobo Guaxupé, pertencente à Nappe Socorro-Guaxupé, nos arredores da cidade de São José do Rio Pardo, é registrado um evento metamórfico e anatético de fácies granulito, sob condições de desidratação da hornblenda, com T >=850ºC. As rochas diatexíticas, que compõem as suítes São José do Rio Pardo (SJRP) e Pinhal, resultam desse evento de alta temperatura, ocorrido há ~625 Ma. As assinaturas geoquímicas e isotópicas sugerem uma geração a partir da anatexia da crosta continental inferior. Além disso, o enriquecimento em potássio da suíte SJRP indica uma afinidade vaugnerítica, a qual é caracterizada por altos conteúdos de Mg, elementos do tipo LILE (large ion lithophile elements), HFSE (high field strenght elements) e ETR-leves, além de valores negativos de \'épsilon\'Nd e razões de Sr iniciais baixas, ~0.706. O magmatismo vaugnerítico implica em um manto litosférico metassomatizado como fonte, o qual foi enriquecido por eventos de subducção precedentes. A presença de pseudomorfos de fusão nesses diatexitos indicam uma evolução quase isotérmica sob presença de líquido anatético. O transporte sin-magmático ocorreu para NE-E. A fonte de calor para esse metamorfismo pode estar associada à delaminação da base do arco magmático. O processo de fusão parcial gerou leucossomas charno-enderbíticos na Unidade Metatexítica, com assinaturas geoquímicas e isotópicas que indicam uma fonte crustal. Dessas rochas, foram separados cristais de zircão que mostraram duas populações distintas. A primeira, tipicamente com cristais prismáticos e bipiramidados, indicam idades em torno de 620 Ma, enquanto que a segunda, com cristais isométricos típicos de alto grau metamórfico, indicam idades em torno de 610 Ma. Em relação ao pico metamórfico de ~625 Ma, as idades mais jovens obtidas sugerem um período de 15 my em que predominaram altas temperaturas. O transporte tectônico para NW, em estado sólido de alta temperatura, é posterior à cinemática sin-magmática para NE, e deve estar associado à compressão da placa superior convergente, dentro desse período de alta temperatura. Esse regime tectônico é compatível com modelos recentes da tectônica Andina onde é descrita uma subducção horizontal (Pampean flat subduction). Dentre as rochas da Unidade Granulítica Basal, também submetida à fusão parcial por desidratação da hornblenda, ocorrem gnaisses com afinidade adakítica, sugerida pelas altas razões Sr/Y = 72.73, La/Yb = 23.07, \'(La/Yb) IND.N\' = 15.56, e teores de #mg = 51.77, Sr = 1062 ppm, Cr = 197 ppm e Ni = 103 ppm. Tal afinidade sugere magmas resultantes da fusão de um slab em subducção. A Nappe Socorro-Guaxupé admite uma evolução que se inicia, cerca de 670-640 Ma, com uma subducção inclinada para a geração de rochas cálcio-alcalinas com alguns membros adakíticos. É seguido um momento de colisão, entre 625 e 610 Ma, com a geração de rochas diatexíticas e metatexíticas de alto potássio, onde o arco migrou primeiramente para o ante-arco (estado subsólido) e depois em direção ao interior da placa superior (estado sólido). A estabilização da nappe se deu quando da colocação dos maciços sieníticos pós-tectônicos, Capituva e Pedra Branca. / The W-SW portion of the Guaxupé Domain, nearby the São José do Rio Pardo city, records a granulite facies anatetic event under hornblende dehydration-melting conditions, i.e. T >=850ºC. The diatexitic rocks that are comprised within the São José do Rio Pardo and Pinhal suites resulted from this high-T metamorphic event, ca. 625 Ma. Geochemical and isotopic signatures suggest derivation from the lower continental crust. The K-rich SJRP suite also show geochemical affinity with vaugneritic rocks, suggested by high contents of Mg, LILE, HFSE and light-REE in addition to negative ?Nd and low Sr initial ratio (~0.706). Vaugneritic magmatism implies on a derivation from a metasomatized lithospheric mantle source enriched before partial melting in a previous subduction setting. Once both suites contain melt pseudomorphs, it is then suggested and isothermic evolution under the presence of melt. A syn-magmatic driven transport occurred towards NE-E, and the heat source for high-T conditions could be assigned to mantle delamination under the margmatic arc. Within the Metatexitic Unit, partial melting resulted in charno-enderbitic leucosomes whose geochemical and isotopic signatures indicate crustal sources. From these leucosomes, two different populations of zircon crystals were separated. The first, comprising bypiramidal-prismatic grains, yield ages around 620 Ma, whereas the second typology of zircons is isometric and soccer-ball type, yielding younger ages around 610 Ma. The latter typology is typical of high-T and melt-bearing rocks. Considering the 625 Ma metamorphic peak, the younger ages suggest a 15 my period when high-T conditions prevailed. Top-to-NW transport, under solid-state high-T conditions, can be associated to the compression of the upper convergent plate within this high-T period. Textural features suggest this transport to have occurred after the crystallization of the syn-magmatic rocks. The compression of the upper plate resembles recent models of the Andean orogenic cycle, where the Pampean flat subduction is described. Among the rocks of the Basal Granulitc Unit, which also underwent hornblende-dehydration partial melting, a gneissic rock shows adakitic affinity, suggested by Sr/Y = 72.73, La/Yb = 23.07, \'(La/Yb) IND.N\' = 15.56, #mg = 51.77, Sr = 1062 ppm, Cr = 197 ppm and Ni = 103 ppm. Adakitic magmas are thought to be slab melts. The Socorro-Guaxupé Nappe was built up between 670 and 640 Ma with a steep subduction and generation of calc-alkaline and subordinate adakitic rocks. A collisional setting, generating high-K diatexites and metatexites, took place between 625 and 610 Ma, where the arc firstly migrated (in subsolidus state) towards the forearc and then migrated (in solid state) towards the interior of the upper plate. Post-tectonic Capituva and Pedra Branca syenitic plutons intruded around 610 Ma, recording the arc migration ceasing.

Debate persists on the timing, magnitude and style of crustal shortening, uplift and basin evolution in the Andes. Many studies suggest that the central Andes, including the Altiplano plateau, were gradually uplifted as a result of protracted Cenozoic retroarc shortening. However, recent isotopic studies conclude that the Andes instead rose in pulses, with the most significant event occurring at 10-6 Ma. Many researchers attribute these rapid pulses of uplift to lower lithosphere delamination events. A better understanding of the history of Cenozoic crustal shortening is essential for determination of the mechanism(s) of Andean uplift. The well-exposed Cenozoic San Jerónimo Group was studied in the Ayaviri basin of the northern Altiplano in southern Peru. The 3-5 km-thick succession is situated at 3900-4800 m elevation, between the Western Cordillera magmatic arc and the Eastern Cordillera fold-thrust-belt. New detrital zircon U-Pb geochronological results from four sandstones and one reworked tuff in the San Jerónimo succession show large age populations indicative of syndepositional volcanism between approximately 38 and 27 Ma. A 1600-m-thick magnetostratigraphic section further constrains the depositional timing and accumulation rate of the upper portion of the succession. Sedimentological observations show a rapid transition from cross-stratified braided-fluvial sandstones to proximal channel-fill and alluvial-fan conglomerates at ~30 Ma. Paleocurrent measurements show important temporal and spatial variations in sediment dispersal patterns while conglomerate clast counts show an upsection transition from almost exclusively volcanic input to increasing contributions of clastic, quartzite, and limestone detritus. The corresponding shifts in depositional environment and sediment provenance are attributed to the activation of new thrust structures in close proximity to the basin, namely the Pucapuca-Sorapata fault system, indicating the presence of an eastward advancing fold-thrust belt dating to at least 38 Ma and reaching the Ayaviri basin within the northern Altiplano plateau at ~30 Ma. / text

The kinematics and architecture of orogenic systems may be heavily influenced by climate, but little research has focused on the long-term effects of glacial erosion on orogenesis. Low-temperature thermochronometry and subsidiary structural, earthquake relocation, and offshore seismic reflection data from the St. Elias orogen are the basis for a new architectural model and demonstrate an association between glacial denudation and orogenic evolution. These data show that exhumation and deformation within the St. Elias orogen are focused across a thin-skinned fold and thrust belt on the windward flank, whereas the leeward flank functions as a deformational backstop. A previously unrecognized structure beneath the Bagley ice field separates these domains with south-side-up motion. This structure is interpreted to be a backthrust, making the orogen doubly-vergent. Suggestive of accelerated fault motion in response to climate change, bedrock cooling rates within the hanging wall of the backthrust and across the entire subaerial wedge accelerated ~ten-fold coeval with the onset of intense glacial conditions. Within the orogenic wedge, the zone of highest Quaternary exhumation (5 km/myr (±25%)) is focused around a narrow zone where the glacial equilibrium line altitude (ELA) intersects mean topography. This zone of rapid exhumation, not present prior to the onset of intense glacial conditions, cuts across the structural trend of the orogen and is more narrowly focused than the zone of orographic precipitation. Augmented glacial erosion around glacial ELA also coincided with a regional shift in deformation away from prominent forethrusts including the North American-Yakutat terrane suture (Chugach St. Elias fault) and the seaward deformation front (Pamplona zone). Accelerated denudation across the subaerial wedge thus appears to have forced the redistribution of strain along the backthrust and a series of forethrusts that lie beneath the zone of highest glacial flux, which in turn are systematically truncated by the backthrust. In a cause and effect response, the expansion of glaciers therefore appears to have resulted in an orogen scale structural reorganization and a narrowing of the orogenic wedge to preserve topographic slope. The focusing of long-term erosion around glacial ELA and the structural response of the orogenic wedge to Cenozoic climate change have not previously been observed in a real-world orogenic system and imply a high degree of coupling between climate and tectonics in this glacially-dominated orogen. / Ph. D.