Search

Gneiss–migmatitic rocks and granites between the Cubatao and Itariri shear zones characterize the Mongagua Complex-Coastal Terrane. Three major units are defined: (1) the Itariri Suite (IS) composed of monzogranites, granodiorites, tonalites, and locally gneiss–migmatitic rocks; (2) the Areado pluton composed of monzogranite and locally tonalite; and (3) the Ribeirao do Oleo Pluton mainly composed of monzogranites, which is the subject of this article. Combined field observations, petrography, Sr–Nd–Hf isotopes, U–Pb zircon data, and preliminary geochemical studies are presented for the Ribeirao do Oleo Pluton (ROP), intrusive in granite-gneisses of the IS. It is a plutonic association of weakly peraluminous, medium-to-high-K biotite monzogranites that surround microgranular intermediate enclaves, which are products of magma mingling. Different from the most examples of magma mingling described in the literature, the ROP mingling did not result from the intrusion of hot mafic magma into colder host felsic magma. Conversely, the emplacement of the monzogranite started most likely during the medium-to-final stage of crystallization of the quartz microdiorite. A detailed study of LA-ICP-MS U–Pb zircon ages, including zircon morphology and internal structure, was useful to determine more precisely the emplacement sequence and the relation between the units of the ROP. Intermediate and acid facies have Paleoproterozoic and Neoproterozoic inheritances, moreover a mixture of xenocrysts, antecrysts, and autocrysts, indicative of a complex evolution of the ROP. Several magma crystallization pulses are recorded at 655–624 Ma, 627–601 Ma, and 613–586 Ma. The negative eHf(t) ranging from − 17.26 to − 12.51 in monzogranites, eNd(t) values of − 10.66 to − 7.83 at t = 600 Ma in both facies, 87Sr/86Sr of ca. 0.708 for the monzogranite and 0.706 for the quartz microdiorite indicate a strong crustal contribution in the genesis of intermediate and acid magmas of this pluton.

O Superterreno Pernambuco Alagoas (PEAL), previamente designado de Maciço e/ou Terreno, é o segmento tectônico identificado imediatamente ao sul do lineamento Pernambuco. Apresenta uma área de cerca de 60.000km2, forma triangular, com a base entre o Recife e imediações de Maceió, e com vértice nas imediações de Santa Cruz, oeste de Pernambuco. Sua composição é extremamente variada, com terrenos de alto grau, arqueanos, paleoproterozoicos, eo-neoproterozoicos e tratos metavulcanossedimentares neoproterozoicos (faixas supracrustais). Estes terrenos são cortados por granitoides neoproterozoicos diversos, incluindo batólitos lineares de grandes dimensões, por stocks e batólitos menores relativamente isolados. Localmente, na sua parte centro sudoeste, foi recentemente reconhecido magmatismo granítico de arco (Ediacarano em idade). O comportamento geotectônico deste amplo superterreno- posicionado entre as faixas orogênicas da Zona Transversal e aquelas da periferia norte do craton do São Francisco (parte do o chamado “domínio meridional” da Borborema) tem sido bastante estudado, discutido e nomeado, mas é de conhecimento geral ainda perfuntório. Apresenta uma trama litoestrutural complexa, e pode ser preliminarmente dividido, para fins expositivos em três porções distintas: porção ocidental (com muitos relictos arqueanos e paleoproterozoicos), porção central (embasamento paleoproterozóico retrabalhado e supracrustais neoproterozoicas) e porção mais oriental, com exposição de um longo e linear batólito longitudinal (longitudinal à costa atlântica) e algumas supracrustais, distintas daquelas anteriormente citadas.

The tropical Northern Andes constitutes a great area to explore the interaction of tectonics and climate on the evolution of orogenic topography, as they are tectonically active, have steep gradients in relief and precipitation, and were less affected by Quaternary glaciations than high-latitude mountains. This study combines new and published thermochronology along ∼500 km of the Eastern Cordillera in Colombia to explore what controls the rates of Miocene and Pliocene exhumation, including: (1) variations in late Cenozoic paleoclimate, (2) orographic precipitation or (3) variation in rock uplift associated with structural heterogeneities along the eastern flank of the range. New thermochronology data consists of 27 apatite and seven zircon (U-Th)/He ages and five apatite fission track ages. Thermal history models show that rock cooling as a result of erosional exhumation has occurred everywhere in the Eastern Cordillera since at least the Miocene at spatially and temporally variable rates. Exhumation rates vary by an order of magnitude between various fault-bounded blocks and there is no evidence for a spatially uniform increase in exhumation rates during the past ∼4–5 Ma that would indicate uniform climatic driven exhumation. The west (dry) to east (wet) gradient in precipitation rates across the Garzon Massif is not a major factor controlling the exhumation rates, as the exhumation rates are highest on the western drier flank. The greatest rates of exhumation of the Eastern Cordillera occur in the blocks associated with vigorous Cenozoic reactivation of inherited faults that had focused extension during Early Cretaceous rifting.

The Northern Andes are the result of multiple tectonic phases, which include extensional and compressional volcanic arcs, strike-slip fragmentation, and accretion of exotic terranes. The alternations of these tectonic settings have overprinted and fragmented the geological record, which has hindered precise paleogeographic and tectonic reconstructions. In the western segment of the Colombian Andes, the oceanic-cored Western Cordillera (WC) and the continental Central Cordillera (CC) are separated by the Romeral Fault Zone (RFZ). This segment of the Andes preserves the record of Cretaceous back-arc extension, the onset of compression, and the accretion of the Caribbean plateau during the Late Cretaceous-Paleocene. To refine the tectonic evolution of the Western Colombian Andes, this study documents new detrital zircon fission-track (ZFT) data from the Meso-Cenozoic sedimentary cover in the CC, the RFZ, and the WC; new ZFT and zircon helium (ZHe) bedrock data from the CC and the RFZ; and new U–Pb detrital data from the Miocene sedimentary cover of the RFZ. Within the RFZ, we obtained bedrock ZFT ages of 239.0 ± 11.0 Ma and 111.1 ± 4.3 Ma, and detrital ZFT data from the Abejorral Formation are interpreted as the result of post-magmatic cooling and Cretaceous rifting. Late Cretaceous to Eocene ZFT and ZHe ages (∼61–50 Ma) in the CC and detrital ZFT data in the WC record exhumation and deformation of the CC during and after the collision of the Caribbean plateau with the continental margin. Finally, detrital U–Pb and ZFT data from the Amaga Formation record the formation of a Miocene intermountain basin. This study reconstructs the basin geometries and the deformation patterns before, during, and after the collision of the Caribbean plateau with the South American margin. We highlight that in accretionary orogens, in which prolonged deformation and erosion have removed the sedimentary cover, the quantification of differential basement exhumation is key to reconstruct thick-skin deformation and to define major tectonic boundaries.

El Grupo Puesto Viejo constituye una unidad continental de edad triásica localizada en el bloque de San Rafael, al oeste de las principales acumulaciones de esa edad del ámbito cuyano. Su conocimiento está basado en estudios regionales, sedimentológicos y bioestratigráficos. Alberga un importante contenido paleontológico de restos fósiles vertebrados, restos fósiles vegetales, registros palinológicos y de invertebrados, ampliamente estudiados. En este trabajo se presenta un análisis tectonoestratigráfico del Triásico de San Rafael, integrando información estructural, sedimentológica y geocronológica de modo de brindar un panorama del origen y evolución de la cuenca en la que se depositó. Las tareas fueron llevadas a cabo en un área de estudio limitada dentro de los afloramientos del Grupo Puesto Viejo, en la cual las relaciones entre estructuras y relleno permitieron verificar que integran un único depocentro convenientemente preservado de las inversiones tectónicas andinas. A través de estudios de campo y gabinete, se pudo constatar que la estructura del depocentro estudiado responde a la geometría de un graben NO-SE, con estructuras internas oblicuas ONO-ESE. Las fallas que bordean el depocentro registraron movimientos de rumbo y normales, mientras que las internas fueron fallas casi puramente normales. Dentro del graben se han preservado otras estructuras internas como zonas de acomodación y pliegues amplios. Algunas de las fallas internas generaron flexuras monoclinales. Las estructuras se observan a la escala de algunos kilómetros y hasta la de pequeñas fallas centimétricas. La estructura del graben se desarrolló en sucesivas etapas, en las cuales se generaron grábenes y hemigrábenes rellenos por sedimentitas y volcanitas triásicas. En este trabajo se subdividieron cuatro etapas principales de estructuración. En la primera se habría generado el espacio general del graben, con amplio desarrollo areal y escasa subsidencia. En las siguientes etapas, la acción de las fallas internas creó espacios estructurales ligados a la subsidencia mecánica, observándose que las mismas secuencias triásicas se encuentran afectadas por fallamiento en las etapas III y IV. El relleno del depocentro se encontró fuertemente condicionado por la estructura y el magmatismo. A partir del análisis estratigráfico, sedimentológico y geoquímico de las unidades que lo componen se pudieron agrupar asociaciones de facies que derivaron en la definición de unidades de acumulación. Se identificaron cinco unidades de acumulación que se definieron como abanicos aluviales, sistemas fluviales, flujos piroclásticos, efusiones lávicas e intrusivos. La composición magmática es de carácter bimodal, con productos volcánicos andesíitco/basálticos y piroclásticos riolíticos. Cada una de las etapas estructurales tiene su correlato en una etapa de relleno, cada una de las cuales posee características particulares. La etapa inicial muestra el desarrollo de abanicos aluviales que son cubiertos por flujos piroclásticos. La etapa II está caracterizada por el desarrollo de sistemas fluviales meandrosos de alta sinuosidad y también finaliza con la aparición de mantos de flujos piroclásticos. La etapa III se caracteriza por la presencia de depósitos de sistemas meandrosos de baja sinuosidad y finaliza con episodios volcánicos, tanto efusivos como intrusivos. La etapa IV se caracteriza por la presencia de un sistema de abanicos aluviales que se intercala con flujos piroclásticos. La geometría del depocentro, tanto como su evolución y la cinemática de las estructuras permiten definir que se trata de una cuenca de carácter extensional, que puede ser caracterizada como un rift oblicuo. La disposición general del depocentro copia la dirección de las estructuras heredadas de la historia orogénica paleozoica del Bloque de San Rafael (orogenia Sanrafaelica) y la disposición de las estructuras internas son compatibles con un régimen de extensión con dirección de máxima elongación ENE-WSW. La cinemática de las estructuras puede ser explicada por una baja a moderada oblicuidad y alta partición de la deformación. Recientes edades radimétricas ( 245 Ma – 235 Ma) ubican a los procesos del Grupo Puesto Viejo dentro del marco geocronológico general de la extensión triásica del oeste de la Argentina, cuyas etapas de rift evolucionaron durante el Triásico Medio. Estas edades permiten reconocer que no existe continuidad estratigráfica entre los últimos procesos del Pérmico y que puede ser necesaria una revisión bioestratigráfica parcial de la unidad., Facultad de Ciencias Naturales y Museo

Tese (doutorado)—Universidade de Brasília, Instituto de Geociências, Programa de Pós-Graduação em Geologia, 2015. O Bloco Rio Apa compreende segmento crustal Paleoproterozoico da porção sul do Cráton Amazônico, situado no sudoeste do estado do Mato Grosso do Sul e nordeste do Paraguai. Constitui o embasamento de sequências metassedimentares do Orógeno Paraguai e é recoberto pelos depósitos paleozoicos da Bacia do Paraná e por extensas coberturas cenozoicas da Bacia do Pantanal. Este estudo apresenta novos dados geológicos, geoquímicos e geocronológicos (U-Pb, Sm-Nd, Ar-Ar), com sugestão de reordenamento tectono-estratigráfico do Bloco Rio Apa. Este terreno constitui segmento de margem continental ativa, edificado durante o Orosiriano/Estateriano, resultado da convergência de arco magmático, na porção sul do Cráton Amazônico, durante a evolução do supercontinente Columbia. O bloco é resultado de eventos orogenéticos acrescionários, incluindo geração de crosta juvenil e retrabalhamento crustal, subdividido nos setores ocidental, central e oriental. É caracterizado por um embasamento granito-gnáissico Riaciano-Orosiriano, representado pelo Complexo Porto Murtinho (2,07 - 1,89 Ga). Intrudido nestas rochas ocorre a Suíte Amoguijá (1,88-1,83 Ga), formada pelos granitos Alumiador e pelas rochas vulcânicas da Formação Serra da Bocaina, associadas à Suíte Gabro-anortosítica Serra da Alegria e ao Gabro Morro do Triunfo. Sobrepostos a estes litotipos, ocorrem às rochas do Grupo Alto Tererê (1,76 Ga) geradas em ambiente de bacia de retroarco, seguido por intrusões graníticas tardi a pós-orogênicas, estaterianas, do Complexo Rio Apa (1,80-1,71 Ga). Estes eventos magmáticos constituem segmentos do Arco Magmático Amoguijá, conforme demostrado nos estudos litoquímicos e são caracterizados por associações graníticas calci-alcalinas, geradas entre 1,88 e 1,71 Ga (TDM 2,69 a 1,75 Ga e eNd -5,91 a +3,29). Capeando estes conjuntos litológicos, ocorrem às rochas metassedimentares do Grupo Amolar. Relacionado a evento extensional tardio, são encontrados enxame de diques e sills máficos da Suíte Rio Perdido (1.59Ga), com ampla distribuição na área. A estruturação do bloco é resultado de processos deformacionais que promoveram encurtamento crustal. Dois importantes episódios metamórficos são reconhecidos: 1670 Ma e ~1300 Ma, com homogeneização isotópica e retrometamorfismo do fácies anfibolito para xisto verde. Esses eventos levaram à individualização de três domínios lito-estruturais, com características deformacionais distintas, resultado de imbricamento das unidades. Esses domínios são limitados por zonas de cisalhamento vergentes para oeste e desenvolvidas principalmente durante a Orogenia San Ignácio (1,32-1,30 Ga). Verificou-se que as rochas do Bloco Rio Apa foram preservadas da deformação brasiliana. Os dados obtidos sugerem correlação das rochas do Arco Amoguijá com as rochas do arco magmático Juruena, exposto no norte do Mato Grosso que integram o Cráton Amazônico e constituem segmentos da Província Geocronológica Rondônia- Juruena. Este estudo contribui para a melhoria do conhecimento geológico regional da porção sul do Cráton Amazônico e compreensão dos processos de evolução geotectônica do Bloco Rio Apa. The Rio Apa Block comprises Paleoproterozoic crustal segment of the southern portion of the Amazonian Craton. It is located in Southwest of Mato Grosso do Sul-Brazil and northeast of the Paraguay. Consists in the basement of metasedimentary sequences of the Paraguay Orogen, covered eastwards by paleozoic deposits of the Paraná Basin and by extensive cenozoic coverage of the Pantanal Basin. This study presents new geological, geochemical and geochronological (U-Pb, Sm-Nd, Ar-Ar) data with tectono-stratigraphic reordering of Rio Apa Block. This terrain consists of an active continental margin segment. It was built during the Orosirian/Estateterian, within a process of magmatic arc convergence on the southern portion of the Amazon Craton during the evolution of supercontinent Columbia. Rio Apa block results of a succession of accretionary orogenic events, including juvenile crust generation and crustal reworking. It was divided into three main sectors: (i) Western sector; (ii) Central sector; (iii) Eastern sector. The stratigraphy of the block is characterized by a Rhyacian-Orosirian granitic gneiss basement (2.07-1.89Ga), represented by the Porto Murtinho Complex. It is intruded by the Amoguijá Suíte (1.88-1.83Ga), which consists of Alumiador granites and the Serra da Bocaina Formation, related to basic intrusions of Serra da Alegria gabbro-anorthositic Suíte and Morro do Triunfo Gabbro. Overlying these lithotypes appear the rocks of the back arc generated Alto Tererê Group (1.76Ga), related to Staterian late to post orogenic gneiss and granite of the Rio Apa Complex (1.80-1.71Ga). It constitutes segments of the Amoguijá Magmatic Arc, as demonstrated in lithochemical studies and characterized by calc-alkaline granitic associations – crystallized between 1.88 Ga and 1.71 Ga (TDM from 2.69 to 1.75 Ga and eNd ranging from -5.91 to +3.29). The metasediments of Amolar Group covers these lithological sets. Related to the calimian extensional event at 1.59 Ga are found mafic dyke and sill swarm of Rio Perdido, widely distributed in the area. The structure of the block results of deformational processes that promoted crustal shortening. Two important metamorphic deformational episodes are recognized (1670Ma and ~ 1300 Ma) with isotopic homogenization and amphibolite to green schist facies retrometamorphism. Those events allowed the individualization of three litho-structural domains, with different deformation characteristics. Those domains result of overlapping units, whose borders are controlled by west vergent shear zone and were developed mainly in the San Ignácio orogeny (1.32-1.30 Ga). It was found that the rocks from the Rio Apa Block were not affected by the brasilian deformation. These data along with petrological and litochemical information suggest correlation between the Amoguija Arc rocks and the Juruena magmatic arc rocks, outcropped in north of Mato Grosso. They integrate the Amazon Craton and consist in the geochronological Rondônia- Juruena Province. This study contributes to the improvement of the regional geological knowledge of the southern portion of the Amazonian Craton and understanding of the processes involved in the geotectonic evolution of Rio Apa Block.

A compreensão dos condicionantes deflagradores de movimentos de massa é importante na medida em que a partir do entendimento desses é possível prevenir ou mitigar desastres naturais em determinada região. No caso do município de Baixo Guandu-ES, mais de 1200 cicatrizes de deslizamentos foram fotointerpretadas e posteriormente checadas em trabalhos de campo. Segundo informações da Defesa Civil Municipal a deflagração desses eventos se deu, majoritariamente, em 25 de dezembro de 2013 durante uma forte precipitação, causada por um corredor de umidade que estacionou sobre a região pela ação de uma Zona de Convergência do Atlântico Sul. Cerca de 77% das cicatrizes mapeadas estão em encostas com declividade não superiores a 30º. Até o dia 23 de dezembro, apesar do acumulado de chuva de mais de 600 milímetros, nenhum ou pouco evento de movimentações de massa haviam ocorrido no município. As análises mostraram que a região com maior quantidade de cicatrizes observada é coincidente com a área onde o acumulado de chuva entre os dias 23/12/2013 e 24/12/2013 (dois dias antes de ocorrer os deslizamentos) foi de mais de 120 milímetros. Dentre as condicionantes estudadas, o principal agente deflagrador para os movimentos de massa que atingiram região de Baixo Guandu-ES foi a chuva de dois dias antes dos eventos, onde o solo já se encontrava quase saturado e as forças atuantes estavam praticamente iguais as forças de resistentes do maciço. The knowledge of the triggering factors of mass movements is important for the prevention and mitigation of natural disasters in a particular region. In the case of the municipality of Baixo Guandu-ES, more than 1200 sliding scars were photointerpreted and later assessed in field work. According to information shared by the Municipal Civil Defense Office, the outbreak of these events had occurred mainly on December 25, 2013 during a heavy rainfall, caused by a humidity corridor that parked over the region by the action of a South Atlantic Convergence Zone. About 77% of the scars mapped are located on slopes not exceeding 30º. Until December 23, despite accumulated rain of more than 600 millimeters, no mass movement event had occurred in the city. Data revealed that the region with the highest number of scars coincides with the area where the accumulated rainfall between 12/23/2013 and 12/24/2013 (two days before landslides) was more than 120 mm. Among the potential variables studied, the main deflagrating agent for the mass movements that reached the Baixo Guandu-ES region was the rainfall of two days before the events; since the soil was already almost saturated and the driving forces were practically equal to the resistance forces.

Este trabalho é uma síntese acerca do conceito de terrenos tectônico-estratigráficos.O retrospecto histórico do tema é particularmente importante para o entendimento real do conceito; implica o reconhecimento de diferentes fases de evolução do conhecimento geológico:(a) Fase preliminar e longa de discriminação e reconhecimento destes elementos tectônicos por aqueles geólogos chamados de geossinclinalistas / fixistas[~ 1900-1990], todos eles apoiados somente em argumentos descritivos.(b) Fase curta [~1970-1990] de proposição dos primeiros modelos de Tectônica de Placas, quando foram omitidas as muitas ocorrências reconhecidas dos terrenos/“maciços”, porque não podiam se ajustar aos esquemas simplistas dos primeiros modelos, ditos plaquistas.(c) Amplo desenvolvimento do conceito, desde as observações verificadas inicialmente na cordilheira norte-americana ocidental pelos geólogos do United States Geological Survey, USGS (especialmente de 1990-1995) até o presente, pari passu com o marcante enriquecimento dos diferentes e novos suportes alcançados, os quais culminaram com a (atual)admissão de uma Tectônica Global. Como consequência da última fase, quando o reconhecimento da presença de terrenos foi feito praticamente em todos os continentes e em diferentes colagens orogênicas, o conceito deve estar presente como tema obrigatório e usual dos artigos científicos com suporte geológico.

Para la ciudad de Villavicencio (Colombia), desde el estudio de microzonificación sísmica, la amenaza sísmica ha sido definida como alta. En este trabajo se muestran aspectos morfotectónicos y sismológicos que lo corroboran y se exponen las posibles consecuencias que tendría para la ciudad la ocurrencia de un sismo de gran magnitud, ya que su vulnerabilidad se incrementa por las falencias en su infraestructura, por la falta de planes gubernamentales frente a este tipo de contingencia, tanto en prevención como en atención, y porque su población no está preparada para este tipo de amenaza natural.

Introduction to littoral erosion problem in Urabá (Arboletes-Turbo area) Colombian Caribbean coast. Shoreline retreat has been the net dominant historical trend along the 145 km-length littoral between Arboletes and Turbo (Southern Caribbean of Colombia). For the last four decades, there were identified in this littoral shoreline retreats of about 50-100m in several places (Uveros, Damaquiel, Zapata, Turbo) and a maximun of 1.6 km in the Punta Rey-Arboletes area, where land losses were of 4.5 k m2, at exceptional rates of 40m/year. The synthesis of the available information suggest that the general “susceptibility” to erosion between Arboletes and Turbo could be related primarily to relative sea level rise, associated to tectonic movements as well as to the effects of mud diapirism and hydroisostacy. In the more critical areas (Arboletes, Turbo), the natural erosive trends were accelerated by anthropic actions, including river diversion (Turbo), beach mining, and inadequate (or total absense) practices for controlling residual and natural waters. Up to August 2000, there were invested about $ Col 10.000 billions in 155 engineering defences (groins, sea walls and rip-rap which totalize 6.2 km of total length and a volume of materials of 37.000 m3). With few exceptions, groins have not been successful and are now part of the problem, accelerating shore erosion along the adyacent sectors. In the short term, the littoral erosion between Arboletes and Turbo is caused both by marine and by subaerial factors. It is facilitated by the poor lithological strengths of cliffs and marine terraces, mainly composed of highly fractured and weathered claystones and mudstones (with stratification and weakeness planes dipping toward sea) and nonconsolidated, easily liquefacted, fine sediments; both conditions facilitate the occurrence of rocks falls, slides and mud flows that result in high figures of cliff retreat (3 to 4m), specially during the first 15 days of the summer-winter transition (april) and in high waves periods. The case of the littoral erosion between Arboletes and Turbo illustrates well how the natural erosive trends of an area can be accelerated by human interventions and the urgent need for coordinating efforts to cope with littoral land losses., La erosión litoral ha sido la tendencia histórica dominante a lo largo de los aproximadamente 145 km de línea de costa entre las ciudades de Arboletes y Turbo (sur del Litoral Caribe colombiano). En las cuatro últimas décadas ocurrieron retrocesos de la línea de costa del orden de los 50-100m en varios sectores (Uveros, Damaquiel, Zapata, Turbo), y de hasta 1.6 km en el área Punta Rey-Arboletes, en la cual las pérdidas de terrenos suman más de 4.5 km2 y la erosión alcanzó tasas máximas de hasta 40m/año. La síntesis de la información disponible sugiere que la “susceptibilidad” generalizada a la erosión podría ser la respuesta a ascensos relativos del nivel del mar, asociados a la tectónica regional, a los efectos del diapirismo de lodos y a la hidroisostacia, entre otros posibles factores. En los sectores más críticos (Arboletes y Turbo), las tendencias erosivas naturales fueron aceleradas por intervenciones humanas como la desviación del río Turbo, la extracción intensiva de materiales de playa y el manejo inadecuado (o no manejo) de las aguas lluvias y residuales. El costo actualizado de las 155 obras de defensa (espolones, barreras y muros de contención que totalizan 6.2 km de longitud y un volumen de materiales de 37.000m3) construidas hasta agosto del 2000 se calcula en alrededor de los $ Col 10.000 millones. Con muy pocas excepciones, los espolones perpendiculares a las playas no han recuperado arenas y más bien se han convertido en generadores de nuevos problemas en los sectores adyacentes. A corto plazo, la erosión litoral entre Arboletes y Turbo es causada tanto por factores marinos como por procesos de erosión subaérea y es función en buena parte de las litologías poco resistentes de las terrazas y acantilados, compuestos en su mayoría por lodolitas fracturadas y meteorizadas (con buzamientos o planos de debilidad inclinados hacia el mar) y por sedimentos finos no consolidados, fácilmente licuables: ambas condiciones facilitan la ocurrencia de deslizamientos, caídas de rocas y flujos de lodo que determinan retrocesos rápidos (3 a 4 metros) del contorno litoral, sobre todo en los primeros 15 días de la transición verano-invierno (abril) y durante los “mares de leva” (periodos de oleajes fuertes). El caso de la erosión litoral entre Turbo y Arboletes ilustra claramente cómo las tendencias erosivas naturales pueden intensificarse fuertemente por intervenciones humanas (incluyendo las defensas ingenieriles) y la necesidad urgente de coordinar esfuerzos para controlar o mitigar con eficiencia las pérdidas de terrenos litorales.

O Orógeno Gondwana Oeste (OGO), sugerido nesta Tese, é uma faixa linear que se estende por mais de 5000 km do atual noroeste da África ao Brasil Central. Perspectivas modernas e tradicionais sugerem que este Orógeno resultou do consumo e fechamento do Oceano Goiás-Faruriano que culminou na colisão continente-continente envolvendo os crátons Amazônico/Oeste Africano contra os crátons São Francisco/Congo e Saariano. Nesta Tese foi investigada a evolução crustal de um importante setor do OGO no noroeste da Província Borborema (NE-Brasil), assim como em outras áreas no Togo e Mali, utilizando-se de uma estratégia coerente. A geocronologia U-Pb em zircões de rochas siliciclásticas e ígneas indicam a existência de uma margem convergente de longa duração (de até 350 m.y.) associada ao consumo do Oceano Goiás-Faruriano. Na área investigada, particularmente no NE do Brasil no Domínio Ceará Central, o magmatismo associado a esta convergência pode ser dividido em três principais períodos: i) um período inicial constituído essencialmente por magmatismo de arco juvenil em ca. 880-800 Ma que continua até 650 Ma, como evidenciado indiretamente por zircões detríticos de depósitos sin-orogênicos, ii) um estágio de arco maturo em ca. 660-630 Ma caracterizado por rochas magmáticas hibridas entre crosta e manto e iii) anatexia crustal em 625-618 Ma que continua até 600 Ma. A longa evolução do OGO e o sincronismo do metamorfismo de ultra-alta pressão UAP no NE do Brasil, Togo e Mali indicam que a subducção continental e, portanto, a colisão continental ocorreu simultaneamente por pelo menos 2500 km durante o período Ediacariano (620-610 Ma). Nesta Tese propõem-se que o desenvolvimento da Província Borborema entre 620 a 570 Ma resultou da interação de dois eventos colisionais distintos. A Colisão I ao longo do OGO ocorreu há ca. 620-610 Ma como resultado da colisão entre o Bloco Parnaíba, como parte dos crátons Amazônico/Oeste Africano, contra o embasamento antigo da Província a leste. A zona de sutura associada a esta colisão foi reativada por uma zona transformante dextral (o Lineamento Transbrasiliano), permitindo a aproximação da Província Borborema e sua subsequente colisão contra o cráton São Francisco em ca. 590-580 Ma, marcando a Colisão II ao longo do Orógeno Sergipano. A interação dos esforços de leste relacionados com a Colisão I com os esforços de norte relacionados a endentação cratônica em uma litosfera espessa gerou uma trama extensa de zonas de cisalhamento direcionais que contribuíram para a extrusão da Província na direção nordeste. Nesta Tese, também foi considerado que o sincronismo do metamorfismo UAP (620-610 Ma) por pelo menos 2500 km no OGO registra o primeiro indício de subducção continental na escala do Orógeno Himalaiano e o consequente surgimento de Megamontanhas no registro geológico. A formação destas Megamontanhas ca. 40 m.y. antes da explosão da Vida no período Ediacariano tem a idade ideal para providenciar, por meio da erosão, os sedimentos (nutrientes) que são considerados necessários para a evolução da Vida. Finalmente, a evolução do OGO indica que o supercontinente Gondawa já estava formado desde o Oeste da África ao Brasil Central, dificultando a hipótese da chegada tardia do cráton Amazônico/Oeste Africano e assim a existência de um amplo Oceano Cambriano como previamente proposto. The Neoproterozoic West Gondwana Orogen (WGO), suggested in this Thesis, is a linear belt that extended for more than 5000 km from nowadays northwest Africa to Central Brazil. Traditional views suggest that this orogen resulted from the consumption and closure of the Goiás-Pharusian Ocean that culminated in a continent-continent collision involving mainly the conjoined Amazon and West African cratons against the São Francisco-Congo and Saharan cratons. In this Thesis it has been investigated the crustal evolution of an important sector of the WGO in NE-Brazil at the northwestern portion of the Borborema Province as well as in some areas of Africa in Togo and Mali using a coherent approach. U-Pb Zircon geochronology of siliciclastic and igneous rocks indicates a long-lived convergent tectonics (up to 400 m.y) related to the comsumption of the Goiás-Pharusian Ocean. In the studied, particularly in NE- Brazil in the Ceára Central Domain, convergent-related magmatism can be divided into three main periods: i) an early period comprising essentially juvenile arc magmatism at ca. 880-800 Ma and continuing to 650 Ma as evidenced indirectly by detrital zircons from syn-orogenic deposits, ii) a more mature arc period at ca. 660-630 Ma characterized by hybrid mantle-crustal magmatic rocks, and iii) crustal anatexis at 625-618 Ma continuing until ca. 600 Ma. Protracted tectonic evolution in the WGO and synchronicity of UHP metamorphism in NE-Brazil, Togo and Mali indicate that continental subduction, and hence continental collision, occurred simultaneously over at least 2500 km during the Ediacaran period (620-610 Ma). Here, it has been proposed that Borborema Province development from 620 to 570 Ma resulted from two discrete collisional events. Collision I, along the WGO, took place at ca. 620-610 Ma as the result of collision between the Parnaíba Block, as the forefront of the much larger Amazonian-West Africa Craton, and the old basement of the Borborema Province. The suture zone related to this collision was reactivated by a dextral transform zone (the Transbrasiliano Lineament), allowing the Borborema Province to approach and collide against the São Francisco Craton in the south at ca. 590-580 Ma marking collision II along the Sergipano Orogen. The combined stresses related to eastward push from collision I and northward push from the cratonic indentation onto a thickened lithosphere gave rise to an extensive network of strike-slip shear zones across the Province forcing its northeastward extrusion. It has bee also considered here that synchronicity of UHP metamorphism (620-610 Ma) over at least 2500 km in WGO records the first Himalayan-scale deep-continental subduction and the consequent appearance of Megamountains in the geological record. The formation of these Megamountains ca. 40 m.y. before the explosion of Life in the Late Ediacaran is perfectly timed to deliver by erosion the sediments (nutrients) that have been deemed necessary for Life evolution. Finally, evolution of the WGO indicate that the Gondwana supercontinent was already assembled from West Africa to Central Brazil, precluding the late arrive of the Amazon-West African craton and hence the existence of a large Cambrian Ocean as proposed earlier.

A integração de dados geológicos e geofísicos permitiu um melhor entendimento da inter-relação entre estruturas oceânicas e continentais. Fenômenos tectônicos e magmáticos do Meso-Cenozóico do Sudeste Brasileiro podem ter sido condicionados pelo prolongamento das zonas de fratura oceânicas em direção à margem continental. O foco deste trabalho é a evolução da Zona de Fratura de Vitória-Trindade (ZFVT). A Zona de Fratura de Vitória-Trindade (ZFVT), localizada na latitude de 18º40' na Cordilheira Mesoatlântica (CMA), foi mapeada utilizando-se sísmica de reflexão, gravimetria e isócronas magnéticas. A ZFVT na CMA corresponde a um deslocamento axial em torno de 6 km, configurando uma descontinuidade de segunda ordem. O segmento assísmico da ZFVT é definido por uma depressão gravimétrica de direção E-W. Sua extensão para oeste corresponde à Cadeia Vitória-Trindade, representada por altos topográficos individualizados, que limitam desníveis crustais de mais de 400 m e províncias sedimentares de características e espessuras distintas. Esta região cortada pela intrusão de diques (alguns aflorando na superfície) e sills, indica instabilidade tectônica com a movimentação de falhas e ocorrência de estruturas transpressivas (estruturas em flor), elevando toda a coluna sedimentar incluindo o assoalho oceânico. Estas observações sugerem reativações recentes da crosta oceânica com esforços alternantes, ora compressivos ora distensivos, associados a vulcanismos e falhamentos normais. Evidências geológicas e geofísicas, além do mapeamento do alinhamento de epicentros de terremotos, sugerem que o prolongamento da ZFVT está relacionado ao Alto de Vitória e ao tectonismo e magmatismo na porção emersa, representado pelo Lineamento Sismo-Magmático Alcalino Trindade-Paxoréu / Alto do Paranaíba. Propõe-se que a ZFVT atuou e continua atuando como conduto para o magmatismo da Pluma Mantélica de Trindade. The integration of geological and geophysical data allowed a better understanding of the inter-relation between the oceanic and continental structure. Tectonic and magmatic phenomena of the Meso-Cenozoic were probably related to the prolongation of oceanic fracture zones into the Brazilian Southeast continental margin. This work will focus on the behaviour of the Vitória-Trindade Fracture Zone (VTFZ). The Vitória-Trindade Fracture Zone (VTFZ), located at 18º40S in the Mid-Atlantic Ridge (MAR), was defined by seismic, gravity and magnetic isochrones. At the MAR axis the VTFZ corresponds to a second-order discontinuity, with a 6 km axial offset. Away from the ridge axis, potential field data shows a gravimetric depression in E-W direction, which represents the asseismic portion of the VTFZ. Towards the Brazilian Continental Margin there is a series of topographic highs defining the Vitória-Trindade Chain, which is divided into distinct sedimentary thickness and tectonic domains. This area is cut by sills and dikes, indicating tectonic instability, remobilization of faults and strike-slip tectonics which has uplifted the entire sedimentary column, including the oceanic bottom. All of these observations suggest recent oceanic crust reactivation with alternations of compressive and extensional stress associated with volcanism and normal faulting. Geological and geophysical studies, in addition to mapping the earthquakes epicenters, suggest that the continuation of the VTFZ that occurs onland is related to the Vitória High and to tectonic and volcanic activities, which are expressed by the Trindade-Paxoréu /Alto do Paranaíba Alkalic Magmatic and Seismic Lineaments. We propose that the VTFZ acts as a pathway for the magma generated by the Trindade Mantle Plume.

El Alto Atlas de Marruecos se formó por la inversión durante el Cenozoico de un rift continental que se formó durante el Triásico-Jurásico. El Alto Atlas de Marrakech, donde afloran principalmente materiales del basamento y del Triásico sinrift, había sido considerado como un alto o zona poco subsidente durante el rifting Triásico-Jurásico. El estudio multidisciplinario presentado en esta tesis, que integra análisis estructural y termocronología de baja temperatura, revela que el rifting Triásico-Jurásico tuvo un desarrollo completo en el Alto Atlas de Marrakech (con espesores de materiales Triásico-Jurásicos de hasta 4.5-6 km) y por tanto, sugiere que el rift del Tethys y del Atlántico estaban conectados durante el Triásico hasta el Jurásico medio-superior. El estudio de las principales cuencas Triásicas y sus fallas limitantes indican un mecanismo de apertura en extensión, siendo los movimientos direccionales menores, lo que difiere de previas interpretaciones que sugerían un modelo de apertura con movimientos direccionales importantes, incluyendo la zona de falla de Tizi n’Test. La buena exposición de las fallas y cuencas Triásicas proporciona buenos análogos de campo para la exploración en el subsuelo de sistemas extensionales de pre-sal. El análisis estructural también muestra que el rift del Alto Atlas de Marrakech fue estrecho, muy segmentado y que se desarrolló en una dirección ortogonal a la dirección de extensión regional de la época (~NW-SE), a diferencia del Alto Atlas central que desarrolló de forma oblicua. Esta diferencia en la orientación del rift la atribuyo a la indentación del macizo precámbrico del Ouzellarh (parte del Cratón Africano), que desvió la dirección general del rift evidenciando el marcado rol que ejerce la anisotropía litosférica heredada en la dirección y evolución del rift. En cuanto a los resultados de termocronología de (U-Th)He, las edades de enfriamiento de zHe del Jurásico medio-superior a Cretácico inferior obtenidas en el Alto Atlas de Marrakech indican que la subsidencia relacionada con el rift cesó en el Jurásico medio tardío, seguida por un periodo de exhumación en el que se erosionaron 2-3 km de roca. Este resultado, conjuntamente con resultados similares obtenidos por autores previos en la Meseta y el Anti-Atlas muestran una amplia área de exhumación durante esa época, siguiendo la orientación del margen Atlántico. Los modelos térmicos basados en los datos de termocronología de zHe y aHe indican que la orogenia Atlásica en las zonas internas de la cordillera empezó en el Cretácico superior. Los modelos muestran que la exhumación relacionada con la compresión se aceleró en el Oligoceno o en el Mioceno, lo cual es coherente con depósitos sinorogénicos datados anteriormente en las cuencas de antepaís periféricas. El acortamiento orogénico en el Alto Atlas de Marrakech se acomodó por pliegues de gran longitud de onda donde el basamento está involucrado, y por la creación de cabalgamientos de tipo shortcut o by-pass. Los indicadores de movimiento direccional en dichos cabalgamientos son menores. Tanto las evidencias estructurales de campo como los datos de termocronología indican que les fallas activas durante la extensión Triásico-Jurásico no fueron reactivadas en la etapa compresiva, actuando como butresses. La comparación entre las secciones estructurales actuales y la reconstrucción de las cuencas Triásicas-Jurásicas apoyada en la termocronología sugiere acortamientos mínimos totales para el Alto Atlas de Marrakech de entre 13 y 14.2 km (21% y 17% respectivamente)., The High Atlas of Morocco is an aborted continental rift developed during the Triassic-Jurassic and moderately inverted during the Cenozoic. The Marrakech High Atlas, with large exposures of basement and Triassic early syn-rift deposits, has been viewed as a morphologic high or a poorly subsiding domain during the Triassic-Jurassic rifting. The multidisciplinary approach presented in this thesis that integrates structural analysis and low-temperature thermochronology reveals that the Triassic-Jurassic rift was well developed in the Marrakech High Atlas (4.5-6 km thickness of Triassic-Jurassic deposits) and suggests that the Tethys and Atlantic rifts were connected in Triassic to Mid-Late Jurassic times. The main Triassic basins and basin-margin faults show a dominant dip-slip opening kinematics with strike-slip playing a minor role, at variance to models proposing a major strike-slip component, including faults belonging to the Tizi n’Test fault zone. Well-exposed fault and graben structures provide good analogues for the exploration of pre-salt systems in the subsurface. This multidisciplinary study also shows that the Marrakech High Atlas was a narrow and highly segmented orthogonal rift (sub-perpendicular to the main regional extension direction which was ~NW-SE), in contrast to the central and eastern segments of the Atlas rift which developed obliquely. This difference in orientation is attributed to the indented Ouzellarh Precambrian salient, part of the West African Craton, which deflected the general rift trend in the area evidencing the major role of inherited lithospheric anisotropies in rift direction and evolution. The Mid-Late Jurassic to Early Cretaceous zHe cooling ages obtained in certain areas indicate that rift-related subsidence in the Marrakech High Atlas finished in late Mid Jurassic times and was followed by a period of exhumation where nearly 2-3 km of rock were eroded. This, together with previous results in the Moroccan Meseta and Anti-Atlas, define a Mid-Late Jurassic to Early Cretaceous exhuming high following the orientation of the current Atlantic margin. Thermal models based on thermochronologic data indicate that Atlas orogeny in the inner parts of the High Atlas started in the Late Cretaceous, and compression-related exhumation accelerated since the Oligocene or Miocene, consistent with dated tectonics-sedimentation relationships elsewhere. Shortening appears accommodated by basement-involved large-scale folding, and by newly formed shortcut or by-pass thrusting, with rare left-lateral strike-slip indicators. Field structural evidence and thermochronology show that Triassic faults were mostly not reactivated, acting as buttresses. The Triassic-Jurassic basins reconstruction assisted by thermochronology and on the constrained tectonic structures, when compared with present-day cross-sections, suggests minimum values of total shortening in the Marrakech High Atlas of 13 to 14.2 km (21% to 17%).

Inciativa Ibérica para el Estudio de las Fallas Activas (IBERFAULT), Primera Reunión Ibérica sobre Fallas Activas y Paleosismología - Primeira Reunião Ibérica sobre Falhas Activas e Paleossismologia - First Iberian Meeting on Active Faults and Paleoseismology, 27-29 de Octubre de 2010, Sigüenza, Guadalajara, España.-- 4 pages, 4 figures, [EN] In December 2008, in the framework of the EVENT project, we installed a continuous GPS station several km SW of the village of Rodalquilar, inside the Cabo de Gata-Nijar natural park, with the main objective of monitoring the activity of the Carboneras fault. After analyzing 15 month long time-series we have estimated that the fault in question continuues to be active and exhibits mainly left-lateral strike-slip motion of 1.5±0.7 mm/yr with a minor compressive component of 1.0±0.7 mm/yr. Although these findings are still preliminary, they are in agreement with the estimates of slip rates from onshore-offshore paleoseismic studies, [ES] En diciembre del 2008, en el marco del proyecto EVENT y con el propósito de monitorizar la tasa de desplazamiento de la Falla de Carboneras, instalamos una estación permanente GPS a pocos kilómetros al sur-oeste de la localidad de Rodalquilar, dentro del Parque Natural de Cabo de Gata-Nijar. Después de analizar los datos de la estación de GPS, denominada GATA, recopilados durante 15 meses, hemos obtenido evidencias de que la falla en cuestión sigue siendo activa con un movimiento siniestro del orden de 1.5±0.7 mm/año y con una componente de compresión menor, del orden de 1.0±0.7 mm/año. Estas observaciones, aunque preliminares, son coherentes con los resultados de estudios paleosismológicos a lo largo de la falla en tierra y en mar, The work has been supported by the Spanish Ministry of Science and Innovation projects: EVENT (CGL2006-12861-C02-01) and Topo-Iberia (CSD2006-00041) and the FPU pre-doctoral grant to E.A. (AP-2008-01482 )

The Rio Apa cratonic fragment crops out in Mato Grosso do Sul State of Brazil and in northeastern Paraguay. It comprises Paleo-Mesoproterozoic medium grade metamorphic rocks, intruded by granitic rocks, and is covered by the Neoprotero- zoic deposits of the Corumbaand Itapocumi Groups. Eastward it is bound by the southern portion of the Paraguay belt. In this work, more than 100 isotopic determina- tions, including U-Pb SHRIMP zircon ages, Rb-Sr and Sm-Nd whole-rock determina- tions, as well as K-Ar and Ar-Ar mineral ages, were reassessed in order to obtain a complete picture of its regional geological history. The tectonic evolution of the Rio Apa Craton starts with the formation of a series of magmatic arc complexes. The oldest U-Pb SHRIMP zircon age comes from a banded gneiss collected in the northern part of the region, with an age of 1950 23 Ma. The large granitic intrusion of the Alumiador Batholith yielded a U-Pb zircon age of 1839 33 Ma, and from the southeastern part of the area two orthogneisses gave zircon U-Pb ages of 1774 26 Ma and 1721 25 Ma. These may be coeval with the Alto Tereremetamorphic rocks of the northeastern corner, intruded in their turn by the Bao´a das Garcas granitic rocks, one of them yielding a zircon U-Pb age of 1754 49 Ma. The original magmatic protoliths of these rocks involved some crustal component, as indicated by the Sm-Nd T DM model ages, between 1.9 and 2.5 Ga. Regional Sr isotopic homogenization, associated with tectonic deformation and medium-grade metamorphism occurred at approximately 1670 Ma, as suggested by Rb-Sr whole rock reference isochrons. Finally, at 1300 Ma ago, the Ar work indicates that the Rio Apa Craton was affected by widespread regional heating, when the temperature probably exceeded 350°C. Geographic distribution, age and isotopic signature of the lithotectonic units suggest the existence of a major suture separating two different tectonic domains, juxtaposed at about 1670 Ma. From that time on, the unified Rio Apa continental block behaved as one coherent and stable tectonic unit. It correlates well with the SW corner of the Amazonian Craton, where the medium-grade rocks of the Juruena-Rio Negro tectonic province, with ages between 1600 and 1780 Ma, were reworked at about 1300 Ma. Looking at the largest scale, the Rio Apa Craton is probably attached to the larger Amazonian Craton, and the actual configuration of southwestern South America is possibly due to a complex arrangement of allochthonous blocks such as the Arequipa, Antofalla and Pampia, with different sizes, that may have originated as disrupted parts of either Laurentia or Amazonia, and were trapped during later collisions of these continental masses.

Con base en cartografía geológica del Anticlinal de Buenavista se identificaron elementos estructurales que sugieren que el anticlinal es producto de la inversión de la Falla de Mirador, una paleo-falla normal activa durante el cretácico inferior. Adicionalmente se estudiaron los sistemas de fracturas presentes en cada dominio estructural, con lo cual se propone su asociación a tres eventos de deformación frágil. Un evento pre-plegamiento asociado a un campo de esfuerzo regional, un evento sin-plegamiento con fracturas en simetría con las estructuras, y un evento sin-fallamiento asociado a la propagación de las fallas sobre la cobertera sedimentaria. / Abstract. Base on cartography of the Buenavista Anticline the structural elements identified suggest that this structure is related to Inversion of the Mirador Fault, an ancient cretaceous normal fault. In addition, fracture systems were studied in each structural domain, which are proposed to be related to 3 fragile deformation events. A pre-folding event related to regional stress field, a sin-folding event with fracture aligned with major structures, and a sin-faulting event related to propagation of faults in the sedimentary cover. Maestría

We used the fabrics of two granite plutons and U/Pb (SHRIMP) zircon ages to constrain the tectonic evolution of the E-trending Patos shear zone (Borborema Province, NE Brazil). The pre-tectonic Teixeira batholith consists of an amphibole leucogranite locally with aegirine-augite. Zircons from a syenogranite yielded crystallization ages of 591 ± 5 Ma. The batholith fabrics were determined by anisotropy of magnetic susceptibility (AMS) and mineral shape preferred orientation. The fabrics support pre-transcurrent batholith emplacement, as evidenced by: (i) magmatic/magnetic fabrics in low susceptibility ( 1 mSI) corridors connected to shear zones branching off from Patos. One of these satellite shear zones controlled the syntectonic emplacement of the Serra Redonda pluton, which yields a crystallization age of 576 ± 3 Ma. This late shearing event marks the peak regional deformation that, south of Patos, was coupled to crustal shortening nearly perpendicular to the shear belt. The chronology of the deformational events indicates that the major shear zones of the eastern Borborema are late structures active after the crustal blocks amalgamated.

This paper presents a stratigraphical and structural study of the transition zone between São FranciscoCraton and Araçuaí Fold Belt in the Minas Gerais state. Two extensional events with rift formation andsedimentation and one orogenic event can be studied.The first extensional event was dated at 1750-1700 Ma. This event is represented by the N-S Espinhaçobasin formation in a continental rift. Its lower part (Early Sequence) is made of acid to intermediatemetavolcanics and fluvial metasediments, with strong fault-block activity in an initial rift phase (mechanicalsubsidence). The Middle Sequence is composed by quartzite with big cross-bedding and the Upper Sequenceconsists of an alternation of quartzite and metapelitic rocks deposited in a shallow marine setting in asubsequent flexural phase (with termal subsidence).The second extensional phase corresponded to Araçuaí rift formation (1000-900 Ma), with maficdikes swarm in the Espinhaço Supergroup. On the highest uplifted continental glaciogenic facies andglacio-marine sequence (Jequitaí Formation) was deposited. To east, in the Araçuaí basin, they grade intomarine deposits with gravitational sedimentation (debris-flow and turbidites) in a typical prism of passivecontinental margin. Westward, on the craton, the Bambuí Group lies directly on the basement. No equivalentshave been identified in the Araçuaí basin either they have not been deposited or are eroded.The orogenic event (650-550 Ma) is caracterized by zones with asymetric folds showing westwardsvergence separated by thin belts of ductile shearing ( Dp phase). N-S Sp cleavage with stretching lineationto east indicates a westward transport of materials toward the São Francisco Craton. The regional Barrowianmetamorphism is associated to Dp, increasing from anchizone to amphibolite facies. During this orogenicevent the São Francisco Craton and the Araçuaí and Paramirim Fold Belts were formed as individualgeotectonics units.

The cataclastic rocks autcrops are located at the northwestern Pampean Ranges and have a N-S direction. They are limiting the Famatina system to the eastern and carne along the Puna.They have been recognized protomylonites, mylonite gneiss and mylonite schists which may be formed under 10 or 15 km of deep and 275-350° C temperatures of source.The main dominant structure have NNW direction and dips to the eastern. There can be seen compressive movements related to western blocks displacements.During de Ocloyica distrophic phase (Upper Ordovician-Lower Silurian) may be formed these cataclastic rocks, related to the Antofalla Craton collision. En las Sierras Pampeanas Noroccidentales del noroeste argentino se desarrolla una faja cataclástica de rumbo submeridional, en rocas del basamento ígneo-metamórfico pertenecientes al Paleozoico Inferior. Esta estructura coincide con el límite oriental del Sistema de Famatina y su porción septentrional se extiende dentro de la provincia morfoestructural de la Puna.En el área estudiada se reconocen protomilonitas, gneises y esquistos miloníticos, los que, en base a sus características texturales, se habrían formado a profundidades de 10 a 15 km y a temperaturas de 275-350° C.El plano principal de cizalla tiene rumbo NNW e inclina hacia el este y sobre el mismo se distinguen movimientos compresivos con desplazamientos relativos de bloques hacia el oeste.La faja de cataclasitas se habría originado durante la Fase Diastrófica Oclóyica (Ordovícico Superior-Silúrico Inferior) relacionada con la colisión del Cratón de Antofalla.

The granitoids of the Neoproterozoic in the Paraiba do Sul belt in the State of Rio de Janeiro are classified according to their ages related to the recognized tectonic phases, their location in the different tectonic domains, the crustal level of emplacement, petrografic compositions and the tectonic environment. Three groups of granites are distinguished: Syn-F2, Syn-F3 and Syn-F4. The compositionally expanded syn-F2 granitoids, (e.g. tonalite/granodiorite/granite), with age about the 620 Ma., are comparable to the Cordilleran I-Type magmatism, emplaced at level of the crust from amphibolite/granulite facies, and their origin is related to a subduction zone below of the Paraiba of Sul belt, from SE to NW. The other syn-F2 are migmatitic S-type granitoids, linked to a continental collision event with age about the 600 Ma. The syn-F3 and syn-F4 groups are compositionally restricted (e.g. monzogranite and syenogranite dominantly) (-490 - 560 Ma), and their magmatism is considered to be Caledonian I-Type.

Diamond-bearing conglomerates occur in the Sopa Brumadinho Formation of the Middle Proterozoic Espinhaco Supergroup and have been mined in the area of Diamantina, central Minas Gerais, since 1725. On the other hand, similar deposits occur at the base of the Upper Cretaceous Uberaba Formation in the area of Romaria in western Minas Gerais and have been mined since the end of the last century. Although these occurrences differ in age by almost 1.5 Ga, they display several geological characteristics that point to their deposition in fans developed in tectonically active areas. In addition, their diamond content is low, ranging from 0.01 up to 0.07 ct/m³. Apparently the most remarkable difference between them is the absence of kimberlitic indicator minerais such as Cr-pyrope garnet and Mg-ilmenite among the heavies in the Diamantina District.

L'objectiu d'aquest treball és l'estudi de l'estructura i de l'evolució tectònica durant el Terciari d'un sector del nordeste d'Ibèria que comprèn part de les tres unitats tectòniques principals que s'hi han diferenciat clàssicament: la SerraladaIbèrica, la Serralada Costanera Catalana i la Conca de l'Ebre. Més concretament, els objectius del treball poden resumir-se en els punts següents: (1) Estudi de les macrostructures formades durant la compressió alpina, diferenciació de les diverses direccions produïdes i establiment de les relacions temporals i espacials entre elles. (2) Estudi de les macrostructures formades durant la distensió neògena i de les seves variacions espacials. (3) Establiment, a partir dels resultats anteriors, de quina ha estat la cinemàtica de les macrostructures que es van formar i que van actuar durant els dos processos anteriors, compressiu i distensiu. (4) Discutir el o els models dinàmics que es puguin deduir a partir de les conclusions dels apartats anteriors. (5) Estudi de la fracturació a l'escala de l'aflorament -mesostructures fràgils-, de l'evolució que se'n dedueixi discussió de les relacions pntre les macrostructures -compressives i distensives- i les mesostructures.A) Macrostructures formades durant la compressió:A la Serralada Costanera Catalana predominen grans falles de sòcol, d'escala pluriquilomètrica, orientades entre N 070 E al nord i N 030 E al sud. Aquestes falles es disposen esgraonades dextralment.La deformació més important es localitza en bandes estretes al llarg d'aquestes falles i afecta el sòcol hercinià i la cobertora mesozoica. Entre aquestes bandes es troben àrees més extenses i menys deformades. Les faixes de sòcol han sofert un moviment direccional sinistre dominant que, sobretot en les falles d'orientació més pròxima a N 070 E, ha anat acompanyat per una convergència entre els dos llavis de la falla.A la serralada Ibèrica dominen grans falIes de sòcol d'escala pluriquilomètrica d'orientació aproximadament NW-SE. Aquesta directriu és, també, la dominant a la cobertora mesozoica, on es manifesta per plecs i encavalcaments. Hi ha altres directrius minoritàries més pròximes a direccions N-S i E-W.El moviment de les faIles de sòcol té components vertical invers i direccional dextre.La Zona d'Enllaç es caracteritza per un feix frontal (septentrional) d'encavalcaments que s'estén des de Portalrubio (a l'oest) fins a Vandellós (a l'est). Aquest feix posa en contacte la Zona d'Enllaç amb la Serralada Ibèrica, la Conca de l'Ebre i la Serralada Costanera Catalana.Els encavalcaments en superficie afecten només la cobertora mesozoica; el sòcol hercinià no hi aflora.La geometria en planta del feix d'encavalcaments mostra dues virgacions, on les estructures orenen una orientació NE-SW, que se situen damunt les falles de sòcol NE-SW. En secció formen un sistema d'encavalcaments imbricats, amb fletxes pluriquilomètriques (10 Km com a màxim).La deformació de la cobertora minva del nord cap al sud, passant a una àrea subtabular. Al sud del feix d'encavalcaments també s'hi han format plecs d'orientació NW-SE a la cobertora.Les relacions espacials entre aquestes tres unitats i les seves estructures dominants mostren que (1) les virgacions del feix d'encavalcaments estan clarament relacionades amb les falles de sòcol NE-SW sinistres de la Serralada Costanera Catalana, i en són conseqüència; (2) les interferències entre les estructures NW-SE de la Serralada Ibèrica i les E-W de la Zona d'Enllaç mostren que part dels plecs NW-SE són anteriors a les estructures E-W i, posteriorment, ambdues direccions d'estructures es van desenvolupar simultàniament; (3) cal, doncs, una simultaneïtat, almenys parcial, en l'actuació de les tres direccions d'estructures.Les edats de les deformacions compressives que es dedueixen de les relacions d'aquestes amb els materials terciaris indiquen que (1) a la Serralada Costanera Catalana es va produir des de l'Ilerdià-Cuisià (Eocè inferior) fins a l'Oligocè mitjà, com a minim, va haver-hi una migració de l'inici de la deformació des del NE cap al SW; (2) Al sector de Ja Serralada Ibèrica estudiat i a la Zona d'Enllaç l'edat de l'inici de la deformació és imprecís. Les deformacions més antigues identificades són d'edat oligocena inferior i s'estenen fins a l'Oligocè terminal: (3) en alguns llocs de la Serralada Ibèrica (als voltants de Daroca), el moviment dextre invers de les falles de sòcol NW-SE va continuar durant l'Aragonià: (4) s'observa, doncs, novament, la simultaneïtat en la deformació compressiva a les tres graris unitats estructurals de la regió estudiada.B) Macrostructures distensivesEs van desenvolupar posteriorment a les macrostructures compressives i, en bona part, van reaprofitar les falles preexistents, Que van jugar amb moviments normals dominants, formant tot un seguit de fosses litorals (NE-SW) Que s'estenen al llarg de tota la regió estudiada i es continuen fora d'ella.A l'extrem sud de la regió estudiada (a l'Àrea Meridional) es va produir una extensió de la cobertora mesozoica per falles d'escala hectomètrica a quilomètrica, sense que s'hi formessin fosses similars a les litorals.Les edats de les deformacions que es dedueixen en funció dels materials que rebleixen les fosses i cubetes neògenes i de les seves relacions amb les macrostructures distensives indiquen que tant les fosses litorals com les cubetes de l'Àrea Meridional es formaren a partir del Miocè inferior (Burdigalià inferior o Aragonià inferior).C) HesostructuresA partir de l'estudi de les mesostructures fràgils (estilòlits, esquerdes de tensió i, principalment, falles) s'obtenen diverses solucions que es poden agrupar de la manera següent:1) Tensors d'esforços amb sigma-1 i sigma-3 subhoritzontals i valors de R= sigma(2)-sigma(3)/sigma(1)-sigma(3) molt variats. Se'n dedueixen un màxim de dos a cada estació, dels quals un a partir d'una majoria de dades i l'altre només a partir d'una minoria. Els eixos sigma-1 de les dues solucions solen formar un angle proper als 90° i majoritàriament s'orienten al voltant de les direccions NE-SW i NW-SE.2) Tensors d'esforços amb sigma-1 subvertical. L'eix sigma-3 s'orienta o NW-SE o NE-SW; els valors de R són molt variats i sovint pròxims a 0.3) A les estacions on s'ha calculat simultàniament tensors amb sigma-1 vertical i horizontal, l'orientació de sigma-3 horitzontal de la solució majoritària amb sigma-1 horitzontal i de la solució amb sigma-1 vertical coincidexen la gran majoria de les vegades.4) Els tensors amb sigma-1 horitzontal orientat NW-SE només s'han deduït a estacions fetes en materials mesozoics.5) Els tensors amb sigma-1 horitzontal orientat entre N-S I NE-SW i els tensors amb sigma-1 vertical també s'han deduït a estacions fetes en materials neògens.D) Relacions entre les macrostructures i les mesostructuresLes mesostructures formades, tant durant la compressió com durant la distensió, ho fan com a conseqüència de les perturbacions produïdes en el camp d'esforços regional per les macrostructres; no són, doncs, conseqüència directa d'una successió en el temps de diferents camps d'esforços regionals homogenis.E) Evolució de la deformacióTant les macrostructures compressives com les distensives de la regió estudiada poden ser explicades per les variacions produïdes per un mateix mecanisme a escala del nordest d'Ibèria: una col .lisió aproximadament N-S (al voltant de N 010 E) entre Àfrica i Euràsia.Les possibilitats de variacions en la intensitat de l'esforç màxim horitzontal creat a l'interior d'Ibèria com a conseqüència de la col.lisió (amb sigma-1 o sigma-2 orientats al voltant de N 010 E) poden explicar:1) els moviments direccionals o inversos soferts per les grans falles durant la compressió;2) els moviments predominantment normals que tingueren durant la distensió;3) el pas d'un tipus de moviment a l'altre i, per tant, el pas de la compressió a la distensió;4) les variacions espacials í temporals en els moviments de les falles principals., This Thesis deals with the structure and the tectonic evolution during Tertiary or an area comprising the Catalan Coastal Range and the north-eastern most part of the Iberian range, south of the Ebro Basin. It has been carried out taking into account not only the several major structures but also their relations to small-scale structures as analysed in 140 outcrops.There are three main directions of structures within the studied region: NE-SW in the Catalan Coastal Range, NW-SE in the Iberian Range and approximately E-W in the Linking Zone between the former units. In all this area a Hercynian basement exist, unconformably overlain by a mesozoic cover -mainly carbonatic and Paleogene and Neogene siliciclastic rocks.During the Paleogene compressive tectonics in the two former units the dominant structures were basement strike-slip convergent faults, dextral in the NW-SE faults and sinistral in the KE-SW ones. In the Mesozoic cover folding and faulting had similar orientations, but are more developed in the Iberian Range.In the Linking Zone an array or E-W thrusts and raids developed which thrusted on the Iberian Range, the Ebro Basin and the Catalan Coastal Range. Two virgation of this array -structures taking a more NE-SW orientation- show the influence of the contemporary sinistral movement of the NE-SW faults.Compressive deformation began in the Lower Eocene in the Catalan Coastal Range and, at least, in the Lower Oligocene in the Iberian Range and in the Linking Zone. It lasted until the uppermost Oligocene or the lowermost Miocene. From lower Miocene extension have taken place: NE-SW and SW-SE major basement faults became normal faults, giving rise to the formation or rifts superimposed to the compressional former units: the tectonic inversion was very important. Extension didn't start simultaneously all over the studied area; during lower Miocene. When coastal rifts developed, dextral slip still took place into a NW-SE basement fault in the Iberian Range.From the analysis of brittle small-scale structures three types of stress tensors can be deduced: two of them have sigma-1 horizontal and oriented NE-SW and SW-SE respectively. The third one have sigma-1 vertical and sigma-3 SW-SE. Theses small-scale structures were formed in a perturbed local stress-field due to the influence of the geometry and cinematics of major structures, both in time and space, and not the direct result of one or several large-scale geotectonic process.Taking into account the geometry and cinematics or major structures, a near N-S direction of compression is deduced during Paleogene compression, logically caused by Africa-Iberia-Europe collision: a near E-W extension during Neogene is deduced from extensional major structures. Variations in the magnitude or stresses produced by that collision could explain the formation and succession or both Paleogene compressional and Neogene extensional major structures, which had originated within the framework or the same large-scale geotectonic process.