Made available in DSpace on 2014-12-17T14:08:43Z (GMT). No. of bitstreams: 1 SeverinoFN_DISSERT.pdf: 3869767 bytes, checksum: 945ebd462d1133b15f06af55a2ec4392 (MD5) Previous issue date: 2009-12-16 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The general objective of this study was to contribute to the understanding of the chemical evolution of fluids that percolate through carbonate rocks of the Janda?ra Formation. The oxidation and reduction conditions in which grains, source and cement were formed was investigated using the cathodoluminescence technique (CL). The study area is located in the west part of the Potiguar Basin (Fazenda Bel?m field) and Ros?rio Ledge (Felipe Guerra municipality, State of Rio Grande do Norte, Brazil). The analysis of thin sections of carbonate rocks under CL revealed that grains (allochemical or not) and diagenetic products (micritization, dolomitization, neomorphism and cementation) exhibit since absence of luminescence the various luminescence colors (yellow, orange, red, brown, and blue) in a variety of intensities. As pure calcite shows dark blue luminescence, the occurrence of different luminescence colors in calcite crystals suggest one or more punctual crystal defects such as free electron, free space and impurity. The dyeing of thin sections with alizarin and potassium ferrocyanide revealed the absence of ferrous carbonate in the different lithotypes of Janda?ra Formation. Therefore, the different colors and intensities of CL observed in these rocks are probably caused by the presence of ion activators such as Mn2+ and is not an activator/inhibitor combination. In the same way, the absence of luminescence is very probably caused by the absence of activator ions and not due to the low concentration of inhibitor ions such as Fe2+. The incorporation of Mn2+ in the different members of the Janda?ra Formation must have been controlled by the redox state of the depositional environment and diagenesis. Therefore, it is possible that the luminescent members have been formed (e.g.,ooids) or have been modified (gastropod neomorphism) under reduction conditions in the depositional environments, in subsurface during the burial, or, in the case of Rosario Ledge samples , during the post-burial return to surface conditions. As regards the sudden changes from low to moderate and to strong luminescence, these features should indicate the precipitation of a fluid with chemical fluctuations, which formed the frequent zonations in the block cement of the Rosario Ledge samples. This study suggests that the different intensities and colors of CL should be correlated with the Mn2+ and Fe2+ contents, and stable isotopes of samples to determine the salinity, temperature, pH e Eh conditions during deposition / O objetivo geral deste trabalho foi contribuir para a compreens?o da evolu??o qu?mica dos fluidos percolantes atrav?s das rochas carbon?ticas da Forma??o Janda?ra. As condi??es oxidantes e redutoras nas quais gr?os, matriz e cimento foram formadas foi investigada usando a t?cnica da catodoluminesc?ncia (CL). A ?rea de estudo localiza-se a oeste da Bacia Potiguar (Campo da Fazenda Bel?m) e no Lajedo do Ros?rio (Munic?pio de Felipe Guerra, Estado do Rio Grande do Norte, Brasil). As an?lises das l?minas delgadas das rochas carbon?ticas sob CL revelou que gr?os (aloqu?micos ou n?o) e produtos diagen?ticos (micritiza??o, dolomitiza??o, neomorfismo e cimenta??o) exibiu desde aus?ncia de luminesc?ncia ? v?rias cores de luminesc?ncia (amarela, laranja, vermelha, marrom e azul) numa variedade de intensidades . Como a calcita pura mostrou luminesc?ncia azul escuro, a ocorr?ncia de diferentes cores de luminesc?ncia em cristais de calcita sugere um ou mais defeitos pontuais nos cristais tais como el?trons livres, espa?os livres e impurezas. O tingimento das l?minas delgadas com alizarina e ferrocianeto de pot?ssio revelou aus?ncia de carbonatos ferrosos nos diferentes lit?tipos da Forma??o Janda?ra. Portanto, as diferentes cores e intensidades de CL observada nestas rochas s?o provavelmente causadas pela presen?a de ?ons ativadores tais como Mn2+ e n?o uma combina??o ativador / inibidor. Da mesma forma, a aus?ncia de luminesc?ncia ? muito provavelmente causada pela aus?ncia de ?ons ativadores e n?o devido a uma baixa concentra??o de ?ons inibidores tais como Fe2+. A incorpora??o do Mn2+ nos diferentes constituintes da Forma??o Janda?ra deve ter sido controlada atrav?s do estado redox do meio ambiente deposicional e diagen?tico. Portanto ? poss?vel que os constituintes luminescentes tenham se formados (Ex: o?ides) ou tenham sido modificados (Ex: neomorfismo de gastr?podes) sob condi??es redutoras no meio ambiente deposicional, em subsuperf?cie durante o soterramento, ou, no caso das amostras do Lajedo do Ros?rio, durante o p?s-soterramento, no retorno ?s condi??es superficiais. No que diz respeito ?s mudan?as bruscas de luminesc?ncia baixa para moderada e forte, estas caracter?sticas devem indicar a precipita??o de um fluido com flutua??es qu?micas, nas quais formou freq?entes zona??es no cimento blocoso das amostras do Lajedo do Ros?rio. Este estudo sugere que as diferentes intensidades e cores de CL deve ser correlacionado com o conte?dos de Mn2+ e Fe2+ e is?topos est?veis das amostras para determinar a salinidade, temperatura, pH e Eh durante deposi??o

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-07-08T21:26:33Z No. of bitstreams: 1 JulianaGomesRabelo_DISSERT.pdf: 6918558 bytes, checksum: 49052116e94f4eb616610a9e4ad69145 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-07-12T21:45:11Z (GMT) No. of bitstreams: 1 JulianaGomesRabelo_DISSERT.pdf: 6918558 bytes, checksum: 49052116e94f4eb616610a9e4ad69145 (MD5) / Made available in DSpace on 2016-07-12T21:45:11Z (GMT). No. of bitstreams: 1 JulianaGomesRabelo_DISSERT.pdf: 6918558 bytes, checksum: 49052116e94f4eb616610a9e4ad69145 (MD5) Previous issue date: 2014-10-06 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O fraturamento em rochas carbon?ticas vem atra?ndo aten??o devido as novas descobertas de petr?leo em reservat?rios carbon?ticos. Este estudo investiga como fraturas (falhas e juntas) submetidas a diferentes campos de tens?es se comportam e como seu comportamento pode estar associado ? gera??o de carste e, consequentemente, ao aumento da porosidade secund?ria em carbonatos. Neste estudo usei imagens de sat?lite e imagens de ve?culos a?reos n?o tripulado, al?m de dados de campo para identificar e mapear falhas e juntas no lajedo de rochas carbon?ticas, que considero ser um bom an?logo para reservat?rio carbonat?co. O lajedo est? localizado na Forma??o Janda?ra, Bacia Potiguar. Os dados de campo foram modelados utilizando o software TECTOS, que usa an?lise de elementos finitos para fraturas 2D. Formam identificados tr?s sets de juntas NS, EW e NW-SE, que foram reativadas como falhas. Os maiores valores de Ratio of Failure by Stress (RFS) obtido na modelagem representam o qu?o perto a rocha est? de tocar a envolt?ria Mohr-Coulomb, que indica a concentra??o da tens?o. Os resultados indicam que as tens?es tect?nicas est?o concentradas em zonas estruturais preferenciais, que s?o locais ideais para a gera??o de dissolu??o nos carbonatos. Observei dissolu??o ao longo de fraturas e planos de estratifica??o em todo o lajedo. No entanto, concluo que os maiores valores de RFS ocorrem no cruzamento e termina??es das fraturas. Estes s?o lugares de concentra??o do carste. Finalmente sugiro que existe uma rela??o direta entre a concentra??o da tens?o e a localiza??o da dissolu??o em rochas carbon?ticas. ABSTRACT The fracturing in carbonate rocks has been attracting increasing attention. This study investigates how the fractures (faults and joints) behaves subjected to the stress field and how their behavior may be associated with the generation of karst and consequently to increased secondary porosity in these rocks. We use satellite imagery and VANT image and field data to identify and map the faults and joints, analogous outcrop carbonate rock reservoir in the Janda?ra Formation, Potiguar Basin. Then, we modeled our data using the TECTOS software, which uses finite element analysis for 2D fractures. The results indicate that the tectonic stresses are concentrated in preferred structural zones, which are ideal places for the generation of dissolution in carbonates. The highest values of Ratio of Failure by Stress (RFS) obtained in modeling represents how close the rock is touching the envelopment Morh-Coulomb. We conclude that the highest values of RFS occur at the intersection of fractures and termination thereof. These sites are places of concentration of karst. From the data collected in the field there were three sets of fractures with NS, EW and NW-SE directions. In all cases, the regular pattern of fractures indicates that the system of lineaments 80 ? and 340 ? direction are sets of joints that were reactivated as faults. The joints and faults are shown consistent with the extracted lineaments in the GoogleEarth image. However, it is observed that, in marioria cases, both sets are reactivated as strike-slip faults. Tectonic stylolites occur mainly found in Lajedo showing shortening parallel to the joints (stylolites NS direction), formed in the same tectonic event. In every part of the flagstone we observed dissolution along fractures and bedding planes of the rock. Combining field data with numerical modeling we suggest that there is a direct relationship between stress concentration and location of dissolution. / The fracturing in carbonate rocks has been attracting increasingly attention due to new oil discoveries in carbonate reservoirs. This study investigates how the fractures (faults and joints) behave when subjected to different stress fields and how their behavior may be associated with the generation of karst and consequently to increased secondary porosity in these rocks. In this study I used satellite imagery and unmanned aerial vehicle UAV images and field data to identify and map faults and joints in a carbonate outcrop, which I consider a good analogue of carbonate reservoir. The outcrop comprises rocks of the Janda?ra Formation, Potiguar Basin. Field data were modeled using the TECTOS software, which uses finite element analysis for 2D fracture modeling. I identified three sets of fractures were identified: NS, EW and NW-SE. They correspond to faults that reactivate joint sets. The Ratio of Failure by Stress (RFS) represents stress concentration and how close the rock is to failure and reach the Mohr-Coulomb envelopment. The results indicate that the tectonic stresses are concentrated in preferred structural zones, which are ideal places for carbonate dissolution. Dissolution was observed along sedimentary bedding and fractures throughout the outcrop. However, I observed that the highest values of RFS occur in fracture intersections and terminations. These are site of karst concentration. I finally suggest that there is a relationship between stress concentration and location of karst dissolution in carbonate rocks.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-04-03T21:15:21Z No. of bitstreams: 1 OrildoDeLimaESilva_DISSERT.pdf: 10653683 bytes, checksum: a0aad2b3ae9ff3382f46da744b549427 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-04-07T22:08:14Z (GMT) No. of bitstreams: 1 OrildoDeLimaESilva_DISSERT.pdf: 10653683 bytes, checksum: a0aad2b3ae9ff3382f46da744b549427 (MD5) / Made available in DSpace on 2017-04-07T22:08:14Z (GMT). No. of bitstreams: 1 OrildoDeLimaESilva_DISSERT.pdf: 10653683 bytes, checksum: a0aad2b3ae9ff3382f46da744b549427 (MD5) Previous issue date: 2016-08-23 / Este estudo teve seu foco em dados de superf?cie e sub-superf?cie rasa, permitindo a caracteriza??o da evolu??o recente do carste epig?nico em quatro est?gios. Durante o Est?gio 1 as fraturas foram abertas pelo processo de dissolu??o, as quais formaram caminhos verticais em escala centim?trica ? m?trica. O conjunto mais abrangente de fraturas concentra a dissolu??o. Ao longo de camadas horizontais intersectadas pelas fraturas tamb?m se observa dissolu??o intraestratal e interestratal. Este sistema de canaliza??o forneceu os caminhos para o fluxo de ?gua, gerando avan?ada lixivia??o. A expans?o alargamento desses condutos em sub-superf?cie ocasiona no Est?gio 2 a queda de blocos, gera??o de dolinas e cavernas. Durante o Est?gio 3, a propaga??o da dissolu??o horizontal e vertical ao longo de fraturas e camadas causam coalesc?ncia de dolinas e captura de pequenos riachos que evoluem para vales incisos e canyons, como pode ser observado no Riacho do Livramento, afluente do rio Apodi-Mossor?, descrito na ?rea III deste estudo. Processos fluviais dominam a dissolu??o do carste durante o Est?gio 4, onde os sedimentos aluviais que recobrem a superf?cie c?rstica carbon?tica, resultando no preenchimento e posterior soterramento de cavernas e dolinas ao longo do vale. Observou-se assim que a influ?ncia do controle tect?nico e do acamamento sedimentar ocorre em todas as fases de evolu??o do carste, resultando nas diversas estruturas e formas de relevo coexistentes espacialmente e que se sucedem, temporalmente, durante os diversos est?gios descritos. Os dados aqui apresentados corroboram os resultados obtidos em outros estudos utilizando dados de GPR, po?os e levantamentos s?smicos, tanto na Bacia Potiguar como em outras bacias sedimentares que evidenciaram que tais estruturas podem ser preservadas ap?s o soterramento. / This research analyzes different types of karst landforms and their relationships with fracture systems, sedimentary bedding, and fluvial processes. We mapped karst features in Cretaceous carbonates of the Janda?ra Formation in the Potiguar Basin, Brazil. The study area is a semi-arid region, with low annual rainfall (600mm) and high evaporation (2000mm). We used high-resolution digital elevation models acquired by Light Detection and Ranging (LiDAR) and aerial ortophotographs acquired by unmanned aerial vehicle (UAV). This study focuses on surface and near surface process and grouped karst evolution into four stages. Fractures were opened by dissolution, which form vertical fluid pathways during stage 1 in a centimetric to metric scale. The most pervasive set of fracture concentrates the dissolution. Coeval intrastratal and interstratal dissolution occurred along horizontal layers, which bound dissolved fractures. This conduit system acted as pathways for water flow, which caused advanced leaching. The enlargement of conduits in subsurface contributed to the collapse of blocks, generation of sinkholes, and caves expansion in stage 2. During stage 3, propagation of horizontal and vertical dissolution along fractures and layers cause coalescence of sinkholes and capture of small streams. Fluvial processes dominate karst dissolution during stage 4, where alluvial sediments that caps the carbonate karst surface and fill caves and sinkholes along the valley. Tectonic and sedimentary bedding control all stages of karst evolution and resulting structures and landforms formed during these stages coexist. Comparisons with GPR, borehole and seismic surveys in sedimentary basins indicate that these structures are preserved after burial.