L'uranium, élément lithophile et incompatible, peut être utilisé en traceur géochimique pour discuter des différents modèles de formation et d'évolution de la croûte continentale. Ce travail de thèse, ciblé sur la ceinture Pan-Africaine du Lufilien en Zambie, caractérise le cycle de l'U et les minéralisations d'U pour ce segment de croûte continentale. Les séries silicoclastiques/évaporitiques de la ceinture du Lufilien, encaissant les minéralisations d'U, se sont déposées en contexte de rift (bassin du Roan) lors de la dislocation du supercontinent Rodinia au Néoprotérozoïque inférieur. Les âges U-Pb des grains de zircon détritique de ces séries métasédimentaires soulignent une source principalement Paléoprotérozoïque. Ces mêmes grains de zircon présentent des signatures isotopiques epsilonHf inférieures au CHUR (entre 0 et -15) et des âges modèles TDM Hf, compris entre ~2.9 et 2.5 Ga. Ces données suggèrent donc la formation d'une croûte continentale précoce, et donc une extraction mantellique de l'U dès la fin de l'Archéen puis une remobilisation par déformation et métamorphisme au cours du Protérozoïque. L'U aurait donc été remobilisé et re-concentré au cours d'orogenèses successives jusqu'au cycle Pan-Africain. Durant ce cycle Pan-Africain, la datation U-Pb et la signature REY (REE et Yttrium) des cristaux d'uraninite caractérisent un premier évènement minéralisateur, daté vers 650 Ma, associé à la circulation de fluides de bassin expulsés des évaporites du Roan, circulant à l'interface socle/couverture, dans ce contexte de rift continental. Un second événement minéralisateur, daté vers 530 Ma et contemporain du pic métamorphique, est assuré par des fluides métamorphiques issus de la dissolution des évaporites, en contexte de subduction/accrétion continentale. Quelques remobilisations tardives de l'U sont observées lors de l'exhumation des roches métamorphiques / Uranium is an incompatible and lithophile element and can be used as a geochemical tracer to discuss the generation and the evolution of continental crust. This thesis, focused on the Pan-African Lufilian belt in Zambia, characterizes the U cycle for this crustal segment. Silici-clastic and evaporitic sediments have been deposited within an intracontinental rift during the dislocation of the Rodinia supercontinent during the early Neoproterozoic. U-Pb ages on detrital zircon grains in these units indicate a dominant Paleoproterozoic provenance. The same zircon grains show subchondritic epsilonHf (between 0 and -15) and yield Hf model ages between ~2.9 and 2.5 Ga. These data suggest that the continental crust was generated before the end of the Archean associated with U extraction from the mantle. This old crust has been reworked by deformation and metamorphism during the Proterozoic. U has been remobilized and re-concentrated during several orogenic cycles until the Pan-African orogeny. During this Pan-African cycle, U-Pb and REY (REE and Yttrium) signatures of uranium oxides indicate a first mineralizing event at ca. 650 Ma during the continental rifting. This event is related to late diagenesis hydrothermal processes at the basement/cover interface with the circulation of basinal brines linked to evaporites of the Roan. The second stage, dated at 530 Ma, is connected to metamorphic highly saline fluid circulations, synchronous to the metamorphic peak of the Lufilian orogeny. These fluids are derived from the Roan evaporite dissolution. Some late uranium remobilizations are described during exhumation of metamorphic rocks and their tectonic accretion in the internal zone of the Lufilian orogenic belt

Esta memoria trata de la evolución geoquímica de cuencas evaporíticas terciarias y de su utilidad en la reconstrucción de la evolución isotópica (delta(34)S y delta(18)O) del sulfato disuelto en el océano durante el Terciario. Para ello se ha dividido el texto en tres partes principales: Parte 1. Se tratan los aspectos metodológicos y se describen las técnicas empleadas. El microanálisis de inclusiones fluidas mediante Cryo-SEM-EDS, permite el análisis cuantitativo de los solutos en inclusiones fluidas congeladas de tamaños de hasta 15 delta m. Los electrolitos analizados son los componentes mayoritarios presentes en las salmueras atrapadas. Na, K. Mg, Ca, Cl y SO(4). La precisión del método varia según los casos, pero es inferior al 6% para todos ellos salvo para el Cl (<15%). Con el objeto de ampliar el número de elementos analizados a minoritarios y traza, se han realizado análisis mediante otra técnica, LA-ICP-MS, demostrándose que ambas técnicas son complementarias. También se describe la metodología empleada en el análisis isotópico, en especial el funcionamiento de las líneas de extracción de gases y la manipulación de las muestras. Otra parte fundamental es la descripción del funcionamiento de las simulaciones numéricas y sus fundamentos teóricos. Todos los datos analíticos obtenidos de forma sistemática a lo largo de las secuencias evaporíticas son comparados con simulaciones numéricas en diferentes escenarios. Estas comparaciones permiten refinar un modelo de evolución de las cuencas evaporiticas durante la precipitación de las evaporitas, en especial de las halitas. De esta forma se obtienen los parámetros fundamentales en la evolución hidrológica de la cuenca: el índice de restricción, que indica lo abierta o cerrada que está la cuenca a los aportes externos, y las proporciones de recarga, que son las proporciones aproximadas de los distintos tipos de aguas que llegan a la cuenca (continentales, marinas, reciclajes, etc.). Las composiciones isotópicas también están introducidas en los modelos, de forma que una vez determinados el índice de restricción y las proporciones de recarga puede ajustarse la evolución isotópica de las unidades evaporíticas. Al establecerse el carácter marino de la totalidad o de parte de las unidades, éstas pueden ser utilizadas para deducir la composición isotópica de las salmueras y del océano original del que proceden. Los datos de composición isotópica del mar, obtenidos a partir de estas unidades están corregidos de los fraccionamientos provocados por cristalización o por variaciones en el índice de restricción de la cuenca. Por otra parte pueden detectarse otros fenómenos que modifican la composición isotópica, tales como la sulfato-reducción bacteriana o el reciclaje de evaporitas previamente formadas. En el caso del reciclaje puede llegar a cuantificarse de forma aproximada. Parte II. En esta parte se aplica la metodología descrita a diferentes cuencas evaporíticas. a) Cuenca surpirenaica (subcuenca navarra). En este caso ya existen trabajos anteriores en los que se aplica la metodología descrita y en los que se muestra el carácter marino de la unidad halítica inferior (UHI) y el carácter continental de la unidad halítica superior (UHS). En esta memoria se aplica de forma complementaria el estudio de inclusiones fluidas al estudio de las zonas estériles en los yacimientos de silvita de Subiza (Navarra). Se determina el carácter primario de la silvita y el origen sinsedimentario de las zonas estériles. b) Cuenca surpirenaica (subcuenca catalana). Ésta tiene apones fundamentalmente marinos, si bien se pone de manifiesto la importante influencia del reciclaje de los yesos marginales durante la precipitación de la halita. Esta influencia queda registrada en las composiciones isotópicas más pesadas de la subcuenca catalana respecto de la navarra. Ambas subcuencas siguen una evolución paralela, aunque la mayor influencia continental en la subcuenca catalana parece sugerir una menor conexión entre ambas subcuencas. Para ambas subcuencas se deduce la composición isotópica del mar durante el Eoceno superior. c) Fosa Renana (Cuenca de Mulhouse. Alsacia). La evolución de esta cuenca durante la precipitación de la Sal IV es fundamentalmente continental como indican la evolución de solutos en las inclusiones fluidas, composiciones isotópicas y determinaciones (87)Sr/(86)Sr. Es posible la existencia de una influencia marina en la base de la Sal IV, cerca de la llamada zona fosilífera, si bien no se preserva según evoluciona el medio. En esta cuenca se ponen de manifiesto procesos de mezclas de aguas de diferentes orígenes y en proporciones variables en el tiempo. También se identifican procesos redox con reequilibración del oxígeno del sulfato con el oxígeno disuelto en la salmuera. Eslos procesos provocan el enriquecimiento de la delta(18)O hasta valores de +/- 22º/ºº y parecen estar relacionados a una mayor actividad bacteriana en la cuenca. Los datos obtenidos no permiten deducir la composición isotópica del mar durante el Oligoceno. d) Cuenca Precarpática. Se pone de manifiesto la importancia del reciclaje durante la precipitación de toda la unidad halitica. La fuente de solutos es mayoritariamente marina, al principio de la precipitación de halita, y se pone de manifiesto un incremento notable del reciclaje de evaporitas. La composición isotópica de los sulfatos intercalados entre halita y de los yesos marginales es muy semejante. Se plantea el reciclaje de los sulfatos precipitados en el margen activo de la cuenca como posible fuente de solutos. A partir de los datos obtenidos y una vez determinada la influencia del reciclaje, se deduce una composición isotópica para el mar durante el Badeniense. e) Cuenca de Lorca. Las conclusiones de los estudios preexistentes sobre inclusiones fluidas se ven confirmadas por los nuevos datos isotópicos obtenidos. Se diferencia en la unidad salina un tramo inferior de origen marino, con variaciones en el índice de restricción y apones continentales puntuales que provocan ligeras variaciones isotópicas. Por encima se distingue un tramo superior, de origen continental, con una evolución isotópica que se interpreta por el reciclaje de diferentes proporciones de sulfatos de la propia cuenca y sulfatos de origen Triásico. A partir de los datos de la unidad salina (tramo inferior) se deduce la composición isotópica del mar messiniense. f) Cuenca de Caltanissetta. Los datos de inclusiones fluidas preexistentes y los realizados para esta memoria diferencian un tramo halltico inferior, de origen marino, y un tramo superior, separado por sulfatos de K y Mg, que muestra su carácter marino, pero con influencias del reciclaje de evaporitas de la propia cuenca. Se ha determinado la evolución isotópica de dos sondeos diferentes, siendo los resultados iguales para ambos, y en concordancia con los resultados de las inclusiones fluidas. A partir del tramo marino se obtiene un rango para la composición isotópica delta(34)S del océano messiniense que coincide con la deducida en la cuenca de Lorca. Las delta(18)O obtenidas son aproximadamente +3 º/ºº más pesadas e incompatibles con las deducidas en Lorca. Se propone la existencia de procesos redox generalizados de forma semejante a como sucede en medios actuales de origen marino. Parte III. En esta parte se realizan diversas consideraciones sobre la evolución del sulfato disuelto en el océano. A partir de los datos obtenidos en diferentes cuencas evaporíticas, se concluye que el déficit de sulfato (respecto a la evaporación del mar actual), común a muchas cuencas evaporíticas, no se debe a cambios globales en la composición del océano sino a variaciones locales dentro de las propias cuencas evaporíticas. Procesos de dolomitización o la entrada de salmueras ricas en Ca son las responsables del descenso en la concentración de sulfato. Una de las consecuencias directas del déficit de sulfato es la precipitación de silvita como mineral primario a partir de la evaporación de agua marina. En cuanto a la composición isotópica., se insiste en la necesidad de conocer con exactitud el origen marino de las evaporitas empleadas para deducir la evolución isotópica del sulfato disuelto en el océano. La metodología empleada en trabajos anteriores en la que se utilizan evaporitas de orígenes diversos, y en ocasiones desconocidos, provocan la imprecisión de las curvas de evolución isotópica deducidas. La metodología presentada en esta memoria permite el refinamiento de dichas curvas y la obtención de datos precisos sobre la composición isotópica del sulfato disuelto en el océano. / The subject of this thesis is the geochemical evolution of tertiary evaporitic basins and their use in reconstructing the isotopic evolution (delta(34)S y delta(18)O) of sulphate dissolved in the ocean during the Tertiary. Part 1: The methodology is discussed and the techniques employed are described. Microanalysis using Cryo-SEM-EDS allows the quantitative analysis of frozen fluid inclusions up lo 15 mili-micres in size. The major solutes analysed from the trapped brine are Na. K, Mg, Ca, CI and SO. To analyse minor and trace elements, diverse analyses have been carried out using another technique, LA-ICP-MS. Thus demonstrating that, these techniques complement each other. The methodology used in isotopic analysis and numerical simulations, how they work and their theoretical bases are also described. The analytical data are compared with numerical simulations that reproduce different scenarios. Thus a model of the evaporitic basins evolution during precipitation can be refined. From these models fundamental parameters in the basins hydrological evolution have been obtained: restriction index and recharge proportions. The isotopic compositions are also introduced into the models so the isotopic evolution of the evaporitic units can be adjusted. Once the marine origin has been established, the model is used to deduce the brine's isotopic composition and that of the original ocean. Part II: In this section the methodology discussed above is applied to various evaporitic basins. - Southpyrenean basin (Navarran sub-basin, Spain) - Southpyrenean basin (Catalonian sub-basin, Spain) - Rhine Graben (Mulhouse basin, Alsace, France) - pre-Carpathian basin (Poland) - Lorca basin (Murcia, Spain) - Caltanissetta basin (Sicily, ltaly) Part III: According to the data obtained from different evaporitic basins it is concluded that the sulphate deficit - in respect to the evaporation of today's seawater - common in many evaporitic basins is not due to global changes in the oceans composition but rather lo local variations within the evaporitic basins. Regarding the isotopic compositions, it is important lo assure the exact marine origin of the evaporates that are used to deduce the isotopic evolution of sulphate dissolved in the ocean. The methodology presented in this thesis allows isotopic curves to be refined.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-04T11:32:21Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE_INALDO.pdf: 12292650 bytes, checksum: 47271b94bc4307fa96add30491036a09 (MD5) / Made available in DSpace on 2016-07-04T11:32:21Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) TESE_INALDO.pdf: 12292650 bytes, checksum: 47271b94bc4307fa96add30491036a09 (MD5) Previous issue date: 2015-08-04 / CAPEs / Este trabalho tem por objetivo simular numericamente via método dos elementos finitos a deformabilidade e estabilidade geomecânica de lavras subterrâneas em evaporitos, considerando cenários de galerias executadas pelo método de câmaras e pilares e de escavação para estocagem de gás natural. Os evaporitos são economicamente importantes por serem fontes de matéria-prima para a fabricação de diversos produtos. A silvita é o mineral mais explorado para a produção de potássio, pois a sua estrutura química de cloreto simples favorece o seu aproveitamento industrial. No Brasil, a produção de potássio é realizada pela CVRD (Companhia Vale do Rio Doce) na mina de Taquari-Vassouras, que está localizada em Sergipe. Foi utilizado o modelo constitutivo mecanismo duplo de deformação com ativação térmica. Para validação do modelo constitutivo foi comparado resultados de simulações com resultados de medições, reais, de convergência de deformação, de câmaras do Painel D1. Foi estudado a possibilidade de influxo de água no Painel I5 e apresentou-se uma modelagem de um pilar 3D. Foi simulado, ainda, queda de blocos laterais e uma câmara para estocagem de gás natural. Para reproduzir os efeitos do processo de formação de fraturas, apresenta-se a técnica de fragmentação, a qual usa os elementos de interface para reproduzi-las. Onde os elementos regulares têm comportamento assumidamente de fluência e o comportamento dos elementos da região de interface é regido por um modelo constitutivo inelástico capaz de simular os fenômenos envolvidos no processo de degradação do material até a formação da fratura, como o modelo de dano. Tanto o modelo de dano como o modelo mecanismo duplo de deformação, de fluência estacionária, encontram-se implementados no programa, in-house, de elementos finitos CODE_BRIGHT (COupled DEformation BRIne Gas and Heat Transport). As análises apresentaram resultados consistentes, possibilitando o conhecimento do comportamento de fluência das rochas salinas, e seus efeitos, como subsidência, influxo de água, formações de chocos. Além disso, as análises demonstraram a viabilidade da aplicação da técnica de fratura em projetos de Engenharia com a aplicação da metodologia proposta. / This study aims to simulate numerically via the finite element method the deformability and geomechanical stability of underground mines in evaporites considering scenarios galleries performed by the method of room and pillar and digging for natural gas storage. The evaporites are economically important because they are sources of raw material for the manufacture of several products. The sylvite is the most explored mineral for potash production because its chemical structure simple chloride favors its industrial use. In Brazil, potash production is carried out by CVRD (Company Vale do Rio Doce) in the Taquari- Vassouras mine, which is located in Sergipe. We used the constitutive model dual mechanism of deformation with thermal activation. To validate the constitutive model was compared simulation results with measurement results, real, deformation convergence of the cameras of Panel D1. It studied the possibility of water inflow in Panel I5 and presented himself a modeling a pillar 3D. Was simulated also down side blocks and a camera for storage of natural gas. To reproduce the effects of the training process fractures, shows the fragmentation technique, which uses the interface elements to play them. Where regular elements have openly creep behavior and the behavior of the interface elements region is governed by an inelastic constitutive model able to simulate the phenomena involved in the material degradation process until the formation of the fracture, as the damage model. Any damage model as the model dual mechanism of deformation, creep stationary, are implemented in software, in-house finite element CODE_BRIGHT (Gas and Brine Deformation Coupled Heat Transport). The analysis showed consistent results, enabling the knowledge of the creep behavior of the salt rock, and its effects, as subsidence, water inflow and falling blocks. Furthermore, the analysis demonstrated the feasibility of applying the fracture technique in engineering projects with the application of the proposed methodology.

Focused groundwater discharge in endorheic basins provides opportunities to investigate mechanisms for closing hydrologic budgets in arid regions. The Salar de Atacama (SdA), a closed basin in northern Chile, has accumulated over 1800 km3 of halite and a lithium-rich brine since the late Miocene primarily through evapotranspiration of groundwater. The hydrologic balance of SdA and sources of water and solutes required to explain this deposit are not well constrained. An adapted chloride mass balance method drawing on a database of over 200 water sample sites is applied to a remotely-sensed precipitation dataset to estimate spatially-distributed modern groundwater recharge. Comparing groundwater recharge to evapotranspiration in a steady-state water budget constrains potential regional-scale watersheds on the Altiplano-Puna Plateau. The sodium mass balance of the deposit is used to predict long-term water discharge from the basin and place modern fluxes in a paleo-hydrologic context. A 2D groundwater model informed by published paleoclimate reconstructions evaluates whether draining groundwater storage contributes to the modern hydrologic system. Modern recharge from precipitation in the topographic watershed is extremely small compared to evapotranspiration. The missing water is sourced from precipitation in an area over 4 times larger than the topographic watershed, and groundwater recharged during wetter periods in the late Pleistocene is still actively draining and discharging from storage without a corresponding input into the system. These results have implications for lake-level based paleoclimate reconstructions, conceptualizations of watershed boundaries and water resource management.

Uganda is well endowed with economic quantities of salt evident in the interstitial brines and evaporite deposits of Lake Katwe, a closed saline lake located in the western branch of the great East African rift valley. Currently, rudimentally methods of salt mining based on solar evaporation of brine continue to be used for salt extraction at the lake. These have proved to be hazardous and unsustainable to the salt miners and the environment. In this work, literature concerning the occurrence of salt and the most common available technologies for salt extraction is documented. Field studies were undertaken to characterize the salt lake deposit and to devise strategies of improving salt mining and extraction from the salt lake raw materials. The mineral salt raw materials (brines and evaporites) were characterized to determine their physical, chemical, mineralogical, and morphological composition through field and laboratory analyses. In addition, laboratory extraction techniques were undertaken to evaluate possibilities of future sustainable salt extraction from the lake deposit. Also, PHREEQC simulations using Pitzer models were carried out to determine the present saturation state of the lake brine and to estimate which salts and the order in which they precipitate from the brine upon concentration by evaporation. Results reveal that the raw materials from the salt lake contain substantial amounts of salt which can be commercialized for optimum production. The brines are highly alkaline and rich in Na+, K+, Cl-, SO42-, CO32-, and HCO3-. Moreover, they contain trace amounts of Mg2+, Ca2+, Br-, and F-. The lake is hydro-chemically of a carbonate type with the brines showing an intermediate transition between Na-Cl and Na-HCO3 water types. The evaporites are composed of halite mixed with other salts such as hanksite, burkeite, trona etc, with their composition varying considerably within the same grades. The laboratory extraction experiments indicate that various types of economic salts such as thenardite, anhydrite, mirabilite, burkeite, hanksite, gypsum, trona, halite, nahcolite, soda ash, and thermonatrite precipitate from the brine of Lake Katwe. The salts crystallize in the order following the sequence starting with sulfates, followed by chlorides and carbonates, respectively. Moreover, thermodynamic modeling in PHREEQC accurately predicted the solubility and sequence of the salt precipitation from the lake brine. Understanding the sequence of salt precipitation from the brine helps to control its evolution during concentration and hence, will lead to an improved operating design scheme of the current extraction processes. The work providesinformation towards future mineral salt exploitation from the salt lake. / <p>QC 20131129</p>

A precaução com a ruína em um material geológico submetido a altas tensões é um problema bastante comum na Geotecnia. Em um túnel, por exemplo, durante a escavação, é possível gerar uma perda de equilíbrio que pode levar à ruptura, fechamento e perda do mesmo. Quando a perfuração é feita em um maciço com características de deformabilidade dependentes do tempo, a redistribuição de tensões pode levar à ocorrência de grandes deformações em longo prazo. Esse fato se deve ao comportamento de fluência (Creep) do mesmo, que se caracteriza por uma deformação lenta e contínua sobtensão e temperaturas constantes. Tendo como fundamento a modelagem para melhor compreensão e controle desses problemas, este trabalho teve inicialmente por objetivo realizar simulações da interação de maciços evaporíticos com a estrutura de suporte, durante e após a escavação de um túnel. Ao longo do trabalho, vislumbrou-se a oportunidade de ampliar seu escopo para problemas mais gerais de interação maciço-suporte, detalhando-se também a interação entre camadas primária e secundária da estrutura de concreto. Assim, incorporaram-se resultados de análises com atrito limitado entre estruturas de suporte e o maciço, e de interação através da interface de uma membrana para impermeabilização aderente às duas camadas. Essas simulações foram realizadas utilizando o programa de elementos finitos Abaqus® e, em alguns casos, levou em conta a utilização de elementos de suporte no contorno do túnel. / Geotechnical engineers have been faced with difficult problems due to failure of geological materials caused by stresses exceeding the strength. The strain around a circular tunnel during and after excavation, for example, may lead to failure due to stresses redistribution. Particularly in rock masses with time-dependent deformation properties, the new stress field can lead to large strains in the long term or even to the closure of the tunnel due to creep behavior under constant stress and temperature. This work aimed originally at simulating the interaction of concrete support structures with evaporites identifying the effects of creep phenomenon in underground excavations. During the development of the work, it was decided to extend the scope to include other phenomena related to the interaction between the first and second layers of tunnel support structures. These include partial friction or the mechanical interface of a waterproofing sprayed membrane. For the development of the present study, numerical simulation of the time-dependent interaction between support and rock masses, during and after excavation of a tunnel were carried out with the commercial FEM software Abaqus®, chosen due to its versatility for the solution of non-linear problems.

As mineralizações Mississipi Valley-type (MVT) dos depósitos de Zn-Pb de Shalipayco no centro do Peru e de Florida Canyon no norte do Peru, separados por centenas de quilômetros e hospedados na mesma sequência de rochas carbonáticas e evaporíticas de mais de mil quilômetros de extensão motivaram diversos questionamentos que vieram a compor esta tese. As questões fundamentais em que se basearam esta pesquisa são quais as possíveis conexões genéticas entre esses depósitos e como elas se relacionam com a evolução da bacia de Pucará. Assim o estudo enfoca os processos pré-, pós- e formadores do minério ocorrentes em ambos os depósitos, a idade das mineralizações, os controles estruturais e litológicos destas mineralizações, e as implicações para descoberta de novos depósitos neste contexto geológico. Estudos petrográficos, paragenéticos e de caracterização mineralógica, apoiados por análises isotópicas de carbono, oxigênio e estrôncio nos carbonatos e de enxofre, rubídio-estrôncio e chumbo-chumbo nos sulfetos permitiram identificação de fontes do fluido, de enxofre e de metal para mineralizações, a caracterização dos processos de interação fluido?rocha, das condições físico-químicas e dos mecanismos de deposição dos minérios nos depósitos de Florida Canyon e Shalipayco. As mineralogias de minério compostas por esfalerita, galena e pirita são as mesmas nos dois depósitos ocorrendo hospedadas em rochas denominadas dolomito poroso ou brecha dolomítica evaporítica. Estas rochas formam estratos permeáveis e porosos bem definidos, interpretados como fácies de ambiente deposicional sabkha intercalados em calcários finos da sequência do Grupo Pucará de idade Triássico Inferior a Jurássico Superior. Estes estratos originalmente de evaporitos provavelmente se tornaram dolomitos de granulação grossa durante diagênese de soterramento. Estes processos modificaram drasticamente as rochas originais e geraram porosidade e permeabilidade que tornaram estas rochas excelentes hospedeiras de hidrocarbonetos e mineralizações sulfetadas de Zn e Pb. Poros preenchidos por betume foram posteriormente preenchidos por esfalerita e galena e finalmente selados por dolomita tardia. Isótopos de carbono, oxigênio e estrôncio e imagens de catodoluminescência suportam a distinção de carbonatos de diagênese precoce, de diagênese de soterramento e tardios associados aos sulfetos de Zn e Pb, tanto em Florida Canyon quanto em Shalipayco. Os isótopos de enxofre indicam mistura de fontes de enxofre reduzido (BSR, TSR e/ou degradação térmica de matéria orgânica) que teriam se acumulado nos estratos de dolomito poroso e de brecha evaporítica. A mineralização MVT é posterior à migração e acumulação de óleo, e ambas ocorrem nas mesmas rochas do Grupo Pucará. O reconhecimento de mesmas rochas hospedeiras, mesma mineralogia e em mesma paragênese, condicionada por mesmos controles estruturais nos depósitos de Shalipayco e Florida Canyon permitiu assumir mesmos processos atuantes na Bacia Pucará. Foi possível associar estes processos geradores de rocha, de estruturas, de fluidos mineralizantes e de migração destes fluidos aos principais eventos tectônicos descritos na literatura para evolução Andina peruana. A estrutura dômica de Florida Canyon provavelmente se formou por halocinese durante a orogênese Juruá (157-152 Ma); a migração de hidrocarbonetos deve ter ocorrido durante o evento Mochica (100-95 Ma); e as mineralizações MVT de Zn-Pb de Shalipayco e Florida Canyon provavelmente sincrônicas, devem ter ocorrido durante ou logo após a orogênese Peruvian (86-83 Ma). Em Florida Canyon a mineralização supergênica de Zn é dada por smithsonita, hemimorfita e goethita, tendo sido gerada predominantemente por substituição direta da mineralização hipogena. Por correlação com as mineralizações zincíferas supergênicas da Mina Grande e Cristal no mesmo distrito de Bongará, pode-se atribuir a idade do Mioceno superior à de Florida Canyon. / The Mississipi Valley-type (MVT) Zn-Pb deposits of Shalipayco in central Peru and Florida Canyon in northern Peru are separated by hundreds of kilometers and hosted in the same sequence of carbonate and evaporite-bearing rocks that span more than thousand kilometers in the Pucará basin motivated several questions that came to compose this thesis. Fundamental questions that underpin the research of this this study are what are the possible genetic connections between these deposits and how do they related to the evolution of the Pucará basin. This study focuses on the investigation of the pre-, post- and ore-forming processes that occurred in both deposits; the age of the ore forming events; the structural and lithological controls on mineralization; and the implications for the discovery of new deposits in the basin. Petrographic, paragenetic and mineralogical studies supported by isotopic analyzes of carbon, oxygen and strontium in carbonates and sulfur, rubidium-strontium and lead-lead in the sulfides allowed the identification of possible fluid, sulfur and metal sources for mineralization, characterization of the rock-fluid interaction processes, physicochemical conditions and ore deposition mechanisms in the Florida Canyon and Shalipayco deposits. The sphalerite, galena and pyrite mineral assemblages are the same in the two deposits and occurs in porous dolostone or evaporite dolomitic breccia. These rocks form well-defined porous and permeable strata interpreted as depositional sabkha facies intercalated with fine limestones of the Pucará Group sequence from the Lower Triassic to the Upper Jurassic. These former evaporite-bearing strata were probably altered to coarse-grain dolomite during burial diagenesis. These processes drastically modified the original rocks and generated porosity and permeability that made these rocks an excellent host for hydrocarbons and Zn and Pb mineralization. Pores filled with bitumen were later filled by sphalerite and galena and finally sealed by late dolomite. Carbon, oxygen and strontium isotopes and cathodoluminescence images support the distinction between carbonates from early diagenesis, burial diagenesis, and late Zn and Pb mineralization, both in Florida Canyon and in Shalipayco. The sulfur isotopes indicate a mixture of reduced sulfur sources (BSR, TSR and/or possibly thermal cracking of organic matter) that would have accumulated in the porous dolomite and evaporite breccia strata interpreted as sabkha facies. The MVT mineralization occurred after the migration and accumulation of oil, in the same Pucará Group host rocks. The recognition of same host rocks, mineralogy and paragenesis, and same structural controls in the Shalipayco and Florida Canyon deposits suggests that the same processes of diagenesis and mineralization occurred on a basin-scale. It is possible to associate these processes of rock diagenesis, development of structural features and the generation and migration of the mineralizing fluids to the main tectonic events of the Peruvian Andean evolution. The Florida Canyon dome probably involved halokinesis during the Juruá orogeny (157-152 Ma). The migration of hydrocarbons probably occurred during the Mochica event (100-95 Ma) and the Shalipayco and Florida Canyon Zn-Pb MVT mineralization probably occurred during or just after the Peruvian orogeny (86-83 Ma). The supergene Zn mineralization in Florida Canyon deposit consists of smithsonite, hemimorphite and goethite which formed by direct replacement of hypogene sulfide mineralization. Supergene zinc mineralization in the Mina Grande and Cristal deposits in the Bongará district, occurred during the late Miocene, which may have also account for the supergene ores at the Florida Canyon deposit.

La successió cuisiana i luteciana de la Conca Sud-pirinenca Oriental (CSO), situada al NE d’Ibèria, mostra un conjunt de sediments carbonatats, evaporítics i detrítics, els quals van ser dipositats en un context compressiu en una conca d’avantpaís. Aquesta compressió es va generar per col•lisió continental de la placa d’Ibèria i l’Europea entre el Cretaci superior i el Miocè inferior. Com a conseqüència de l’escurçament, els sediments es troben distribuïts en tres unitats estructurals: la unitat autòctona de la conca de l’Ebre, localitzada al sud, i les unitats al•lòctones del Serrat i del mantell del Cadí, ubicades al nord, situada la primera per sota de la segona. Encara que molts treballs s’han centrat en l’estudi de l’estratigrafia i l’estructura de la CSO, l’arquitectura estratigràfica i els ambients deposicionals de les evaporites no s’han acabat de resoldre. Les roques evaporítiques dipositades en conques d’avantpaís actuen, en molts casos, com a nivells de desenganxament i, per tant, aquestes roques estan deformades o simplement no afloren. Com a conseqüència, el coneixement d’aquests dipòsits no és molt ampli, i l’estudi d’afloraments i litofàcies resulta un repte. L’objectiu general d’aquesta tesi és millorar aquest coneixement. En aquesta tesi, a partir de la realització de mapes i talls geològics detallats, i de la correlació de columnes i logs de pous, s’ha establert l’arquitectura estratigràfica de la CSO per als períodes Cuisià superior i Lutecià. Aquesta arquitectura presenta sis seqüències deposicionals, tres de les quals de nova proposta en el present treball. Aquestes tres seqüències corresponen a la seqüència Serrat, formada per les Evaporites del Serrat, i a les seqüències Bellmunt inferior i superior, constituïdes per sediments detrítics. Les Evaporites del Serrat, dipositades per sobre d’una primera seqüència carbonatada (formacions Penya i Armàncies), es caracteritzen per tenir capes de sals i lutites en un depocentre situat actualment en el mantell del Cadí. Aquestes sals estan envoltades per un cinturó marginal anhidrític, localitzat en la conca de l’Ebre. En el centre de la conca, aquestes evaporites estan cobertes per una successió turbidítica atribuïda a la Formació Vallfogona (seqüència Campdevànol) en diferents depocentres. Cap als marges de la conca, aquesta formació canvia lateralment a unitats carbonatades (Calcàries de la Pedra i Calcisiltites). La Formació Guixos de Beuda es troba per sobre de la seqüència Campdevànol, i representa la segona seqüència evaporítica. Les seqüències Bellmunt inferior i superior, caracteritzades per dipòsits d’origen fluviodeltaic (formacions Banyoles, Coubet i Bellmunt), representen les seqüències més modernes d’aquesta arquitectura. Aquestes dues seqüències estan separades per una altra unitat evaporítica, anomenada en el present treball Guixos de Besalú. S’ha reconegut que la potència de les capes d’anhidrites atribuïdes a les Evaporites del Serrat és major en la conca de l’Ebre que en el mantell del Cadí. Per tant, s’ha considerat que aquesta unitat es configura, de la conca de l’Ebre fins al mantell del Cadí, com a un tascó anhidrític que passa a una cubeta salina en el centre de la conca. Per contra, també s’ha reconegut que la potència de la Formació Beuda és menor a la conca de l’Ebre que en el mantell del Cadí. L’anàlisi de mostres d’afloraments i de testimonis de pous ha permès interpretar els models sedimentaris de les unitats evaporítiques més representatives. En les Evaporites del Serrat, s’han distingit tres paleoambients, de marge a centre de conca: plataforma sulfatada, constituïda per anhidrita nodular i pseudomòrfica (de selenites); talús, format per guix secundari (anhidrita en profunditat) amb litofàcies laminada, de caràcter detrític; i conca profunda, constituïda per capes de sal i lutites reconegudes només en el subsòl. En canvi, en la Formació Beuda només s’ha reconegut un únic paleoambient, corresponent a un sistema de conca sulfatada situat en el mantell del Cadí. Aquest paleoambient està representat per cicles de guix secundari (anhidrita en profunditat) amb litofàcies massives i nivells pseudomòrfics (de selenites). De tota manera, l’existència d’àrees amb litofàcies bandades i laminades, atribuïdes a ambients més profunds, indiquen l’existència de petites zones més deprimides en la conca. La composició isotòpica (delta-34S, delta-18O; 87Sr/86Sr) de mostres de guix i anhidrita indiquen un origen marí per aquestes unitats i, a més, processos de dissolució/reprecipitació dels sulfats. A partir de l’anàlisi estructural de les correlacions estratigràfiques, dels mapes i talls geològics, de la interpretació de perfils sísmics reprocessats i de noves dades gravimètriques s’ha deduït que la sedimentació durant el Cuisià superior i Lutecià va tenir dues etapes tectòniques: una primera etapa extensiva, coetània amb la sedimentació de les Evaporites del Serrat i la Formació Vallfogona, i caracteritzada per falles normals produïdes per flexió extensional; i una segona etapa compressiva, sincrònica a la sedimentació fluviodeltaica, i caracteritzada per encavalcaments i plecs, i falles transversals de tipus strike-slip. Durant la primera etapa, les falles normals van tenir direccions obliqües i perpendiculars respecte l’escurçament pirinenc (N-S). Durant la segona etapa, les falles de strike-slip van estar generades per la reactivació de falles normals preexistents. A més, les Evaporites del Serrat van actuar com a nivell de desenganxament del mantell del Cadí i de la Unitat Serrat. Finalment, en aquesta tesi, s’han realitzat models sandbox per tal de millorar el coneixement del paper de l’arquitectura estratigràfica d’una successió dúctil (en aquest cas, evaporites) sobre l’evolució estructural. A partir d’una sèrie d’experiments, s’ha observat que l’existència de discontinuïtats geomètriques en els materials anàlegs a les litologies evaporítiques generen zones de deformació preferencial. Comparant els resultats d’aquests experiments amb els trets estructurals de la CSO, s’ha interpretat que l’evolució i estil estructural d’aquesta conca va estar controlada per l’existència de discontinuïtats litològiques –com el canvi de gruix de les anhidrites entre la plataforma evaporítica i la conca profunda– en les Evaporites del Serrat. L’existència d’aquestes discontinuïtats litològiques va generar encavalcaments fora de seqüència, contribuint a la generació d’una conca de piggyback. / The Cuisian and Lutetian succession of the Southeastern Pyrenean Basin (SePB), NE of Iberia, shows an assemblage of carbonate, evaporite and detrital sediments, deposited under a compressional context in a foreland basin. The compression was generated by continental collision of the Iberian and the European plates during the time span comprised between the Upper Cretaceous and the Lower Miocene. As a consequence of the shortening, these deposits were distributed in three structural units: the autochthonous unit of the Ebro Basin, located to the south; and the allochthonous units of the Serrat Unit (below) and the Cadí thrust sheet (above), placed to the north. Despite many studies have been focused on the stratigraphy and the structure of the SePB, the stratigraphic framework and the depositional environments of the evaporites remain poorly understood. In foreland basins, the evaporite rocks usually act as décollement levels, so they are deformed or simply are not outcropping. As a consequence, the knowledge of these deposits is limited, and the study of outcrops and lithofacies is a challenge. The general aim of the present Ph.D. Thesis is to improve this knowledge. In this Ph.D. Thesis, on the basis of geological maps, cross-sections, and sections and welllogs correlations, a stratigraphic framework of the SePB was established for the Late Cuisian and Lutetian times. This framework considers six depositional sequences, and three of them are newly proposed. These three sequences correspond to the Serrat sequence, formed by the Serrat Evaporites, and the Lower and Upper Bellmunt sequences, constituted by detrital sediments. The Serrat Evaporites, deposited on a previous carbonate sequence (Penya and Armàncies formations), are characterized by salt – shale layers in a depocenter located basinward (nowadays in the Cadí thrust sheet). These salt layers are surrounded by an anhydrite marginal belt, placed in the Ebro Basin. In the basin center, these evaporites are covered by turbidite successions attributed to the Vallfogona Formation (Campdevànol sequence) in different depocenters. To the margins, this formation changes laterally to carbonate deposits (Pedra Limestones and Calcisiltites). The Beuda Gypsum Formation is overlying the Campdevànol sequence, and represents the second evaporite sequence. The Lower and Upper Bellmunt sequences, characterized by fluvio-deltaic deposits (Banyoles, Coubet and Bellmunt formations), are the youngest sequences of this succession. These two sequences are divided by another evaporite unit, called Besalú Gypsum in the present work. The anhydrite layers attributed to the Serrat Evaporites were recognized to be thicker in the Ebro Basin than in the Cadí thrust sheet. Thus, the stratigraphic framework of this unit is characterized, from the Ebro Basin to the Cadí thrust sheet, by an anhydrite wedge which changes to a salt deposit in the basin center. By contrast, the Beuda Formation was recognized to be thinner in the Ebro Basin than in the Cadí thrust sheet. The analysis of samples and well-cores allowed to interpret the sedimentary models of the most representative evaporite units. Three paleoenvironments were distinguished in the Serrat Evaporites, from the margin to the basin center: sulphate platform, constituted by anhydrite nodules and pseudomorphs (after selenite gypsum); slope, formed by secondary gypsum (anhydrite in the subsurface) with laminated, detrital lithofacies; and deep basin, constituted by salt and shale layers, only recognized in the subsurface. On the other hand, in the Beuda Formation, only one paleoenvironment, characterized by a sulphate basin, was recognized in the Cadí thrust sheet. This paleoenvironment is represented by cycles of secondary gypsum (anhydrite in the subsurface) with massive and pseudomorphic (after selenite gypsum) lithofacies. However, the existence of areas with banded and laminated lithofacies, attributed to deeper environments, indicates the occurence of small troughs in the basin. The isotopic composition (delta-34S, delta-18O; 87Sr/86Sr) of gypsum and anhydrite samples indicates a marine origin of these units and, also, dissolution/re-precipitation processes of the sulphates. On the basis of the structural analysis of the stratigraphic correlations, the geological maps, the cross-sections, the interpretation of reprocessed seismic profiles and new gravity data, it was deduced that the sedimentation during the Late Cuisian and Lutetian had two tectonic stages: a first extensive stage, coeval to the sedimentation of the Serrat Evaporites and the Vallfogona Formation, and characterized by normal faults generated by flexural extension; and a second compressional stage, coeval to the fluvio-deltaic sedimentation, and characterized by fold-and-thrust and transverse strike-slip faults. During the first stage, the normal faults had oblique and perpendicular directions with respect to the Pyrenean shortening (N-S). During the second stage, the strike-slip faults were generated by reactivation of pre-existing normal faults. Also, the Serrat Evaporites acted as the décollement level of both the Cadí thrust sheet and the Serrat Unit. Finally, in this Ph.D. Thesis, in order to improve the knowledge about the role of the stratigraphic framework of a ductile succession (evaporites, in this case) on the structural evolution, sandbox models were developed. On the basis of a series of experiments, it was observed that the existence of geometrical discontinuities, located in materials analogue of the evaporites, generates zones of preferential deformation. Comparing the results of these experiments with the structural features of the SePB, it was interpreted that the evolution and the structural style of this basin was controlled by the existence of lithological discontinuities –as the case of the thickness change of the anhydrites between the evaporite platform and the deep basin– in the Serrat Evaporites. The existence of these lithological discontinuities generated out of sequence thrusts, contributing to the development of a piggyback basin.

A precaução com a ruína em um material geológico submetido a altas tensões é um problema bastante comum na Geotecnia. Em um túnel, por exemplo, durante a escavação, é possível gerar uma perda de equilíbrio que pode levar à ruptura, fechamento e perda do mesmo. Quando a perfuração é feita em um maciço com características de deformabilidade dependentes do tempo, a redistribuição de tensões pode levar à ocorrência de grandes deformações em longo prazo. Esse fato se deve ao comportamento de fluência (Creep) do mesmo, que se caracteriza por uma deformação lenta e contínua sobtensão e temperaturas constantes. Tendo como fundamento a modelagem para melhor compreensão e controle desses problemas, este trabalho teve inicialmente por objetivo realizar simulações da interação de maciços evaporíticos com a estrutura de suporte, durante e após a escavação de um túnel. Ao longo do trabalho, vislumbrou-se a oportunidade de ampliar seu escopo para problemas mais gerais de interação maciço-suporte, detalhando-se também a interação entre camadas primária e secundária da estrutura de concreto. Assim, incorporaram-se resultados de análises com atrito limitado entre estruturas de suporte e o maciço, e de interação através da interface de uma membrana para impermeabilização aderente às duas camadas. Essas simulações foram realizadas utilizando o programa de elementos finitos Abaqus® e, em alguns casos, levou em conta a utilização de elementos de suporte no contorno do túnel. / Geotechnical engineers have been faced with difficult problems due to failure of geological materials caused by stresses exceeding the strength. The strain around a circular tunnel during and after excavation, for example, may lead to failure due to stresses redistribution. Particularly in rock masses with time-dependent deformation properties, the new stress field can lead to large strains in the long term or even to the closure of the tunnel due to creep behavior under constant stress and temperature. This work aimed originally at simulating the interaction of concrete support structures with evaporites identifying the effects of creep phenomenon in underground excavations. During the development of the work, it was decided to extend the scope to include other phenomena related to the interaction between the first and second layers of tunnel support structures. These include partial friction or the mechanical interface of a waterproofing sprayed membrane. For the development of the present study, numerical simulation of the time-dependent interaction between support and rock masses, during and after excavation of a tunnel were carried out with the commercial FEM software Abaqus®, chosen due to its versatility for the solution of non-linear problems.

La dépression du Chott El Djérid constitue l'un des bassins endoréiques salins les plus importants dans le monde. Au cours du stade d'inondation, le Chott est rempli par deux lacs temporaires localisés au centre du Chott et séparés par la digue-route P16, suite à des pluies abondantes et/ou la remontée de la nappe souterraine. Les variations spatiales du cycle inondation-assèchement sont marquées par une inondation et un assèchement plus rapide dans la partie au sud de la digue-route que celle au nord. Les variations temporelles sont illustrées par la comparaison de ce cycle entre les inondations de l’hiver 2009, du printemps 2007 et de juin 2014 au cours de la période sèche. Au cours de ce cycle entre avril et août 2007, les valeurs de réflectance ont varié de 2 à 37 % au sud de la digue-route et de 2 à 31 % au nord. Elles sont donc plus élevées et leur augmentation est en moyenne plus rapide au sud de la digue-route qu’au nord. Les processus évaporitiques du Chott sont contrôlés par les processus hydriques et éoliens. Après l'assèchement du lac, les croûtes évaporitiques du Chott comprennent un assemblage de minéraux dominé par la halite sur la marge méridionale de la digue-route et par le gypse au nord de celle-ci. Les croûtes gypseuses apparaissent dynamiques dans l'espace et le temps et sont distribuées plus largement que les croûtes de halite. Les données LSR (Landsat Surface Reflectance) ont fourni des indications sur la minéralogie des évaporites, même si elles sont à moyenne résolution spectrale. L’étude a apporté également des informations sur les autres unités de paysage telles que les aïoun, la bordure sableuse, etc. / Chott El Jerid is one of the most important endorheic salt lake or playa lakes in the world. During the flooding stage, the Chott is mainly filled by two temporary lakes separated by the causeway P16, after high rainfalls and/or groundwater recharge. Spatial variations of flooding-desiccation cycle are illustrated by a faster flooding and drying on the southern edge of Chott than the northern. The temporal variation was illustrated by the comparison between the winter flood in 2009, the spring flood in 2007 and the flood of June 2014 (the only flood during the dry period). During this cycle between April and August 2007, the reflectance values varied from 2 to 37 % to the south of the causeway and from 2 to 31 % to the north. The reflectance values are higher and their increase was faster to the south of the causeway than to the north. The behaviour of precipitation, concentration and distribution of the evaporites on the Chott follows the behaviour of flooding and desiccation. After the final desiccation of the playa lake, the mineralogy of salt crusts comprised an assemblage dominated by halite to the south of the causeway and by gypsum to the north. Gypsum crusts appear highly dynamic in space and time, and they are more widely distributed than halite crusts. The LSR (Landsat Surface Reflectance) data provide information about the mineralogical nature of evaporites of the Chott, although LSR offers only a medium spectral resolution. The study also provided information on the other landscape-units such as aioun, the sandy border, etc.