DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Resultados da Pesquisa
Item Análise estrutural descritiva da mina do Lamego e do seu entorno, Quadrilátero Ferrífero, MG.(1998) Carmo, Vitalino Elizeu Ferreira do; Carneiro, Maurício Antônio; Carneiro, Maurício Antônio; Oliveira, Claudinei Gouveia de; Nalini Júnior, Hermínio AriasItem Bacias do Espírito Santo e Mucuri.(1994) Vieira, Roberto A. B.; Mendes, Marcos P.; Vieira, Paulo E.; Costa, Luciano A. R.; Tagliari, Cláudio Vinicius; Bacellar, Luis de Almeida Prado; Feijó, Flávio JuarezItem Proterozoic crustal extension and generation of dome-and-keel structure in an Archean granite-greenstone terrane.(1992) Marshak, Stephen; Alckmim, Fernando Flecha de; Evangelista, Hanna JordtItem Complexos máfico-ultramáficos do escudo Sul-rio-grandense : revisão com ênfase na geoquímica dos elementos da série 3D de transição.(1992) Hartmann, Leo Afraneo; Wildner, Wilson; Remus, Marcus Vinicius Dorneles; Suita, Marcos Tadeu de FreitasOs complexos máfico-ultramáficos do Rio Grande do Sul foram reavaliados, com ênfase nos dados disponíveis para elementos químicos da série 3d de transição. Os complexos apresentam geralmente três componentes, quais sejam, ultramáfico (principalmente peridotitos, serpentinitos e xistos magnesianos), máfico e metassomático. Este último componente está bem desenvolvido na maioria dos complexos e foi identificado mas não estudado em detalhe. A suíte gabróica está presente em diversas áreas, tal como Pedras Pretas, e mostra uma química da série 3d de transição desde menos evoluída até mais evoluída, podendo ser classificada da mesma forma que em outras séries do mundo. Os serpentinitos são semelhantes entre si, independente da área avaliada, normalmente mostrando características residuais exceto em Pedras Pretas, onde a química do protólito gabróico foi mantida. Os peridotitos do Cerro da Mantiqueira são harzburgitos e a sua química da série 3d não pode ser distinguida de serpentinitos. Na região do Arroio Cambaizinho, os xistos magnesianos contendo várias proporções de tremolita + clorita + magnetita + ilmenita foram testados em camadas com um a cinco metros de espessura e que apresentam continuidade lateral de afloramento de centenas de metros. Eles mostram química uniforme na mesma banda e parecem corresponder a lavas magnesianas, de afinidade possivelmente komatiítica, metamorfizada na fácies anfibolito. As lavas foram derivadas de um manto enriquecido em elementos LILE ou contaminadas por material crustal.Item The tectonic evolution of the Quadrilfitero Ferrifero, Minas Gerais, Brazil.(1994) Chemale Júnior, Farid; Rosière, Carlos Alberto; Endo, IssamuThe structural framework of the Quadrilatero Ferrifero is the result of two main deformational events. The first is an extensional event of Palaeoproterozoic age (between 2100 and 1700 Ma, the Transamazonian Event), which resulted in the formation of Archaean granite-gneiss domes and the nucleation of regional synclines in the overlying Rio das Velbas and Minas supergroups strata. Such regional synclines are continuous with each other and are bordered by structural granite-gneiss highs. At the contact between these units, ductile-brittle to ductile extensional shear zones are developed, representing the dislocation surfaces of Archaean blocks. This tectonism is probably related to the evolution of a metamorphic core complex, formed in the hinterland to the west of a Transamazonian collision zone, which structured the Paramirim Craton. The second event is compressive and associated with the closure of the Pan-African/Brasiliano protoocean (650-500 Ma), situated to the east of Quadrilltero Ferrffero (QF). During this event, a west-verging foldandthrust belt (FTB) developed, causing inversion, amplification, translation and rotation of the basinal synclines. The FTB affected mainly the eastern portion of QF and obliterated many of the tectonic features of the extensional event.Item Burial and thermal conditions of diagenesis in the lower cretaceous Barra de Itiúba formation, Sergipe Alagoas Basin, Brazil.(1996) Varajão, Angélica Fortes Drummond Chicarino; Meunier, AlainItem Particle morphological evolution during the conversion of I/S to Illite in lower cretaceous shales from Sergipe-Alagoas basin, Brazil.(1995) Varajão, Angélica Fortes Drummond Chicarino; Meunier, AlainThe illitic end of mixed-layer illite-smectite series (I/S) in shales from Lower Cretaceous Barra de Itifiba Formation, Sergipe-Alagoas basin, was examined with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). A mathematical decomposition of XRD patterns shows different I/S and illite populations. All the samples contain ordered (R = 1) I/S, poorly crystallized illite (PCI) and well crystallized illite (WCI). A randomly interstratified (R = 0) I/S was also identified in a fractured zone at 1020 m. The percentage of expandable layers in ordered I/S decrease progressively from 20% to 10%. TEM observations show a continuous change in morphology between two basic particle shapes: elongated (lath) and isometric. The size and morphology of particles change with increasing depth. The proportion of laths decreases while isometric particles become predominant. However, both particle types continuously grow and enrich the larger size fraction. The growth process is driven by a mass transfer from the dissolving small particles of predominantly I/S (R = 1) composition to the larger (more illitic) lath and isometric ones. The proportion of lath-shaped particles decreases with depth indicating that the more stable population upon increased burial is the isometric well crystallized illite (WCI) particles. Very large laths are observed in the fault zone where conditions may favor faster growth processes.Item Dome-and-keel provinces formed during Paleoproterozoic orogenic collapse—core complexes, diapirs, or neither? : Examples from the Quadrilátero Ferrífero and the Penokean orogen.(1997) Marshak, Stephen; Tinkham, Douglas; Alkmim, Fernando Flecha de; Brueckner, Hannes K.; Bornhorst, TheodorePaleoproterozoic dome-and-keel provinces, in which troughs of deformed and metamorphosed Paleoproterozoic supracrustal rocks surround domes of Archean basement, continue to puzzle geologists. In current literature, some authors refer to the domes as diapirs (implying basement flowed vertically upward) and others consider them to be Cordilleran-type metamorphic core complexes (implying that the contact between basement and cover is an upwarped detachment). Geochronological studies suggest that dome emplacement occurred during extensional collapse of contractional orogens, seemingly supporting the core-complex analogy. However, structural analyses in the Quadrilátero Ferrífero (Brazil) and the Penokean orogen (Michigan) demonstrate that the domes resemble diapirs in shape and in terms of surface kinematics. The domes differ from diapirs, however, in that they did not flow penetratively within but were emplaced by movement along steeply dipping shear zones. We suggest that contrasts between domeand- keel and core-complex provinces reflect contrasts between Paleoproterozoic and Phanerozoic crustal structure. Specifically, during the Paleoproterozoic, when crust was warmer and supracrustal assemblages denser, core-complex–like detachment faulting and associated plutonism resulted in juxtaposition of hot basement beneath a denser, tectonically thickened supracrustal layer. The resulting viscosity contrast and density inversion triggered vertical rise of diapir-shaped basement domes by slip on steep shear zones.Item O grupo Itajaí, estado de Santa Catarina, Brasil : exemplo de sedimentação em uma bacia flexural de antepaís.(1992) Rostirolla, Sidnei Pires; Alkmim, Fernando Flecha de; Soares, Paulo CésarA análise estratigráfica do Grupo Itajaí permitiu individualizar quatro associações faciológicas em um contexto de bacia flexural de antepaís, tendo-se verificado significativa mudança tanto no suprimento como na sucessão vertical de fácies, quando comparados os estágios inicial e final da sedimentação. A primeira associação constituiu-se de depósitos continentais a plataformais retrogradantes com aporte da margem cratônica, a N-NW. A segunda registra uma sedimentação em condições subaquosas profundas, com paleocorrentes para S-SW. A terceira reflete condições transgressivas, com depósitos pelíticos que avançaram em direção à margem norte da bacia. A quarta e última associação encontra-se representada por depósitos costeiros progradantes, com suprimento da margem orogênica, aS-SE.Item Análise estrutural da tectônica deformadora da Bacia de Itajaí, estado de Santa Catarina, Brasil.(1992) Rostirolla, Sidnei Pires; Soares, Paulo César; Alkmim, Fernando Flecha deStructural analysis of the Itaja" Group has confirmed and increase in deformation magnitude from NW to SE, toward the more deformed zone of the Dom Feliciano mobile belt. This condition is in agreement with the predicted characteristics of a foreland basin deformed in a convergent environment. Two families of tectonic structures were recognized, both corresponding to different deformation phases and associated stress fields. The first represents the late collisional phase of the orogenic cycJe, which caused the development of reverse faults, asymmetric folds, and a conjuga te system of strike-slip faults. The progressive evolution of this convergence led to the change from a frontal to an oblique collision, with dextral-reverse kinematics. The second phase records a post-collisional extensional pulse, leading to the reactivation of earlier structures and inversion of movements along the conjugate system of strike-slip faults.