Programa de Pós-Graduação em Geodinâmica e Geofísica
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Doctoral Thesis Modelagem física da influência da herança estrutural na formação de novas estruturas: aplicação à Zona de Cisalhamento Pernambuco, NE do Brasil(Universidade Federal do Rio Grande do Norte, 2024-12-18) Venâncio, Marilia Barbosa; Silva, Fernando César Alves da; http://lattes.cnpq.br/8572129314081197; http://lattes.cnpq.br/5123468840851117; Bruna, Vincenzo La; Trzaskos, Bárbara; Morales, Noberto; Miranda, Tiago Siqueira deShear zones in the crystalline basement create crustal and lithospheric heterogeneities, acting as zones of weakness that influence the location, geometry, and segmentation of more recent structures. This study investigates the impact of preexisting structures on the development of sedimentary basins and newly formed or reactivated structures during subsequent tectonic events, using the brittle deformation of the Pernambuco Shear Zone (PESZ) as a natural example. Experimental models analyzed with Particle Image Velocimetry (PIV) simulated the role of structural inheritance in forming a rift basin orthogonal to a preexisting weakness zone under different rheological conditions. The effects of preexisting structure orientation on subsequent brittle deformation were also examined. The integration of experimental and field data provided a better understanding of the brittle deformation of the PESZ. The results indicate that preexisting shear zones influence the orientation, location, and geometry of newly formed structures in orthogonal basins, even without reactivation. Rift basins associated with these structural inheritances are wider and shallower. Rheological variations also impacted the number of structures formed. In strikeslip zones, the orientation of inherited structures controlled the formation of subsidiary fractures in the Riedel system, revealing the relationship between the new stress field, the type of structures formed, and the evolutive nature (new or reactivated). This relationship affects the main fault's growth, either as a continuous or in segments, as well as the number of structures formed and the distribution of on- and off-fault deformation. The field and experimental data integration shows that inherited mylonitic fabric acted as a mechanical weakness zone, facilitating brittle reactivation. Three groups of brittle structures were identified along the PESZ: (i) dextral strike-slip reactivation at the end of the Brasiliano Cycle; (ii) sinistral reactivation in the Early Cretaceous, associated with the opening of the South Atlantic Ocean; and (iii) N-S oriented normal faults and fractures, related to the same opening process as (ii), but formed later. The experiments suggest that PESZ may act as a structural high separating the Pernambuco and Paraíba sub-basins. The results highlight the potential of analog modeling for predicting fault and fracture patterns in complex tectonic systems, demonstrating how inherited shear zones can influence the evolution of new structures.Master Thesis Texturas e química mineral de zirconosilicatos em granitos peralcalinos do Pluton Papanduva, PR-SC(Universidade Federal do Rio Grande do Norte, 2024-08-23) Grangeiro, Larissa Praxedes; Vilalva, Frederico Castro Jobim; https://orcid.org/0000-0003-3399-6863; http://lattes.cnpq.br/6227637633613443; http://lattes.cnpq.br/3254967283599785; Rojas, Gaston Eduardo Enrich; Rosa, Pedro Augusto da SilvaElpidite (Na₂ZrSi₆O₁₅·3H₂O) and (Na,K)-zirconosilicates are zirconium-bearing minerals identified in the peralkaline granites of the Papanduva Pluton, located in the Graciosa Province in southern Brazil. These minerals crystallized during the late- to post-magmatic stages, providing insights into the formation and evolution processes in complex magmatic environments. Elpidite occurs in three distinct textural types: (1) isolated crystals with subhedral to euhedral forms, (2) granular aggregates, and (3) vein-like aggregates, each exhibiting specific compositional variations. Additionally, two phases of (Na,K)-zirconosilicates, designated as (Na,K)ZrS-I and (Na,K)ZrS-II, were identified, each displaying distinct textural and compositional properties. Chemical analysis reveals that elpidite has a predominantly uniform composition, with variations in Zr, Al, Ca, and K, aligning with the ideal end-member of elpidite. In contrast, (Na,K)-zirconosilicates are enriched in K relative to Na and exhibit diverse compositional trends. The (Na,K)ZrS-II phase shows greater compositional affinity with melansonite, whereas (Na,K)ZrS-I represents a transitional phase between lower and higher K end-members. However, elemental substitutions occurred within a limited range, suggesting the absence of a complete solid solution between these elements. Trace element analysis of elpidite revealed lower concentrations of most elements compared to zircon, including rare earth elements (REE), but with significant enrichments in Ba, Pb, and Sr. The textural relationships and compositional data of zirconosilicates from the Papanduva Pluton suggest a complex evolution of these minerals, reflecting a transition from less evolved rocks, where zircon predominates as the zirconium carrier, to more evolved rocks. Elpidite likely formed during the late magmatic stages, followed by the development of granular and vein-like varieties. Interaction with K-rich hydrothermal fluids, possibly facilitated by sub-magmatic deformation, resulted in significant hydrothermal alteration, chemical remobilization (including HFSE and REE), and element incorporation, forming (Na,K)ZrS-I and (Na,K)ZrS-II phases from a precursor zirconosilicate, ideally elpidite, or directly from the fluids. This transition is associated with increased peralkalinity (alkali activity), oxygen fugacity, and variation in water content, favoring the stabilization of zirconosilicates as zirconium-bearing phases.Doctoral Thesis Hidrodinâmica em cânions submarinos da margem continental do Rio Grande do Norte(Universidade Federal do Rio Grande do Norte, 2024-11-20) Damasceno, Úrsula Martin; Gomes, Moab Praxedes; Cintra, Márcio Machado; http://lattes.cnpq.br/9348402509955995; https://orcid.org/0000-0003-0836-1073; http://lattes.cnpq.br/2086362176219605; https://orcid.org/0000-0002-2280-3715; http://lattes.cnpq.br/6861998172708778; Costa, Mirella Borba Santos Ferreira; Gbo, Gbekpo Aubains Hounsou; Ximenes Neto, Antônio Rodrigues; Pimenta, Felipe MendonçaPhysical processes at continental margins control the transport of heat, sediments, chemical compounds, and nutrients between the ocean basin and the continental shelf, which affects the ecosystems nearby. The shelf-edge submarine canyons interact with the currents and are potential flow channelers between the coastal zones and the oceanic basin. Despite the importance of these phenomena, canyon-flow interactions in low latitudes of the Atlantic Ocean are poorly understood. This study aims to characterize the hydrodynamic phenomena of the Brazilian tropical margin, specifically the submarine canyons in areas of shelf break zones on the eastern and northern shores of Rio Grande do Norte (RN). Physical processes were investigated using the Coastal Regional Oceanic Community Model (CROCO). The first analysis presented here pertains to the Natal Canyon and was developed in CROCO using regional bathymetry interpolated from nautical charts and global databases, validated with in situ data. This study aims to analyze the hydrodynamics of the Natal Canyon and its effects on the exchange between the shelf and the ocean, and suspended particles. The correlation analysis includes the components of canyon flow, the North Brazil Current, the transport of the outer-middle shelf, and wind stress. Additionally, a drifter model was built using the velocity field of the oceanic model with the Ichthyop model for three different positions: on the southern edge of the canyon, at the head of the canyon, and along the current path on the slope. The results show two main forces driving the canyon dynamics: i) the meridional wind, which has the highest correlation coefficient with canyon transport (-0.75), and ii) the North Brazil Undercurrent with the second highest correlation coefficient (-0.64). In all three simulated scenarios, the current isstrong enough to transport most of the suspended particles (~95%) northward. Despite the general westward transport of the canyon, the current is not strong enough to prevent the capture of particles (~2%) within the canyon. A small portion of particles (<2%) reaches the inner shelf through the canyon head and the coastal current. The results indicate that the dynamics of the Natal Canyon are wind- driven and favor downward flow. This context impacts suspended particles and may explain the starved condition in low-latitude shelves, such as the eastern margin of Rio Grande do Norte, Brazil.Doctoral Thesis Análise probabilística da ameaça sísmica para o Nordeste do Brasil(Universidade Federal do Rio Grande do Norte, 2024-11-29) Fonsêca, José Augusto Silva da; Nascimento, Aderson Farias do; https://orcid.org/0000-0002-3961-5884; http://lattes.cnpq.br/8600906973888297; https://orcid.org/0000-0002-2756-686X; http://lattes.cnpq.br/8516129832322936; Bezerra, Francisco Hilário Rego; Ferreira, Joaquim Mendes; Assumpção, Marcelo Sousa de; Miranda, Paulo de Souza TavaresAlthough they exhibit lower seismicity compared to plate boundary regions, Stable Continental Regions (SCR) are not free from adverse seismic impacts. Assessing seismic hazard in these regions is essential, especially considering the presence of critical infrastructure and urban areas, where low-probability but significant-sized events can still pose substantial risks. In this context, Northeast Brazil stands out as one of the most seismically active areas in the SCR of South America, with events in recent decades causing significant damage to civil structures. This study conducted a Probabilistic Seismic Hazard Analysis for Northeast Brazil, focusing on critical locations, using an updated regional earthquake catalog and newly defined seismic source zones. For this, the application of more appropriate models for magnitude distribution was sought, revealing the rejection of the Gutenberg-Richter relation in one of the seismic sources. The results showed PGA values < 0.01 g for most of the study area, typically ranging between 0.01 g and 0.04 g for much of its northeastern portion, considering a 10% probability of exceedance over 50 years. In this region, under the same conditional probability, the highest PGA values were found in the range of 0.10 g to 0.20 g around the four most active seismic sources. The uniform hazard spectrum indicated values between 0.18 g and 0.08 g over a wide range of structural period for a critical location, reaching an average peak of 0.31 g. The findings suggest that, although most of the region complies with the current Brazilian seismic code, certain areas present significantly higher seismic hazard. In these areas, the respective seismic intensities can vary between VI and VIII, potentially causing damage ranging from minor in civil constructions to the collapse of older buildings.Master Thesis Histologia óssea e diagênese fóssil de smilodon populator e puma concolor (carnivora: felidae) do pleistoceno do Brasil equatorial(Universidade Federal do Rio Grande do Norte, 2024-11-22) Maciel, Virgínia Silva; Ghilardi, Aline Marcele; Aureliano Neto, Tito; https://orcid.org/0000-0002-6918-0519; http://lattes.cnpq.br/3666297020355529; https://orcid.org/0000-0001-9136-0236; http://lattes.cnpq.br/5761534317977568; http://lattes.cnpq.br/4943881100446288; Castro, Mariela Cordeiro de; Araújo Júnior, Herminio Ismael deLarge felids have been one of the groups most impacted by climate change over the last 50,000 years. By comparing palaeobiological aspects of extinct species with those of living species, it is possible to identify possible reasons for extinction selectivity and even describe how species were affected by environmental changes in the past. Understanding these issues is fundamental to understanding the risk that current species face in the face of ongoing climate change. In this study, the femur histology of Smilodon populator (MCC-868V) and a fossil specimen of Puma concolor (MCC-991V) were sampled, both from Quaternary deposits in Rio Grande do Norte, northeastern Brazil, one from a tank and the other from a cave. In addition, estimates of body mass were made for the specimens analysed to compare with bone compactness, and the diagenetic signatures of both specimens were analysed. The presence of EFS (External Fundamental System), generations of secondary osteons and remodeled bone tissue suggest that the individuals analysed were sexually mature, although MCC-868V was a young adult at the time of death and MCC-991V a senescent adult. P. concolor showed slightly greater bone compactness, which may be related to its more advanced ontogenetic stage. The estimated mass for the P. concolor (62 kg) is within the limits observed for the species. However, the estimated mass for S. populator (157 kg) is lower than expected, even though the specimen analysed was an adult with closed growth. There is no histological evidence that the specimen in question was restricted during its growth, suggesting a naturally smaller individual, a trait that may have been selected in a local population due to the specific environmental and ecological conditions of the region and/or the presence of competition with other carnivore(s). Both specimens analysed showed growth with intense secondary remodelling, which differs from what is known for most tetrapods. The extinction of Smilodon is likely more related to ecological aspects, such as a reduction in prey availability or preferred habitat than physiological aspects. Finally, MCC-868V shows diagenetic fractures filled with oxides that break up histological structures and the presence of quartz grains in the bone trabeculae. MCC-991V, on the other hand, shows evidence of recent weathering and the presence of oxide precipitates. The diagenesis of the specimens analysed is very similar to that found in other fossils from the same deposits, which adds to the understanding of the fossilization processes involved in tank and cave deposits in equatorial regions.Master Thesis Integração de dados radiométricos e petrográficos de plutons ediacaranos para detalhamento de mapeamento geológico no domínio Rio Piranhas-Seridó, extremo NE da Província Borborema(Universidade Federal do Rio Grande do Norte, 2024-11-28) Dias, Marília Cristina Santos Souza; Nascimento, Marcos Antônio Leite do; http://lattes.cnpq.br/5356037408083015; http://lattes.cnpq.br/9527786124074381; Vilalva, Frederico Castro Jobim; https://orcid.org/0000-0003-3399-6863; http://lattes.cnpq.br/6227637633613443; Guimarães, Suze Nei PereiraRadiometry is a shallow geophysical investigation method based on the emission of natural gamma radiation from rocks, which aids in identifying lithotypes and lithologicalcontacts. The qualitative interpretation of radiometric data allowed for the characterization of the main signatures of the shoshonitic, high-potassium calc-alkaline porphyritic, high-potassium calc-alkaline equigranular, calc-alkaline suites associated with Ediacaran magmatism (635 – 541 Ma) in the northeastern edge of the Borborema Province. Four plutons were highlighted as target areas: i. Acari; ii. Totoró; iii. São Rafael; and iv. Serrada Garganta. Data from the potassium channels (K in %), equivalent thorium (eTh in ppm), equivalent uranium (eU in ppm), and ternary radiometric composition RGB (red, green, and blue) were used to delineate radiometric domains in a GIS environment. Thesedomains represent closed polygons where the distribution pattern of K, eTh, and eU radioelement contents is classified as low (1), medium (2), and high (3). Interpretation maps for each target area were created based on the 27 possible color combinations in the RGB pattern. The mineralogical composition of the granites, which are mainly composed of quartz, feldspars (plagioclase and microcline), and micas (biotite and muscovite), favors generic K-rich signatures. Additionally, the texture of these granites (grain size and crystal orientation) affects the distribution of these elements. A pattern predominantly showing high values for K and eTh is observed in rocks belonging to the high-potassium calc-alkaline porphyritic (Itaporanga type), alkaline (Conceição type), and highpotassium calc-alkaline equigranular (Dona Inês type) suites. However, the texture of these rocks also influences this analysis, as porphyritic granites tend to highlight K values in relation to eTh and eU content due to the size of the K-feldspar crystals. Nevertheless, regions mapped as the Itaporanga Intrusive Suite that exhibit low to medium patterns in radioelements can be explained by the interference of lenses of dioritic rocks, metasedimentary rocks, terrigenous quartzose sediments, as well as water bodies. For the São João do Sabugi Suite, a predominant pattern of low values for the radioelements was observed, attributed to the mineralogical composition of the rocks in this suite, characterized by the low representation of K, eTh, and eU-rich minerals, with a predominance of biotite and amphibole.Doctoral Thesis Evolução da linha de costa nos deltas do nordeste brasileiro(Universidade Federal do Rio Grande do Norte, 2024-04-30) Ferreira, Thiago Augusto Bezerra; Vital, Helenice; https://orcid.org/0000-0003-0462-9028; http://lattes.cnpq.br/3595069999049968; http://lattes.cnpq.br/4270582380157017; Gomes, Moab Praxedes; Nogueira, Mary Lúcia da Silva; Almeida, Narelle Maia de; Araújo, Paulo Victor do NascimentoDeltas, serving as significant hubs for agriculture, industry, and energy, are susceptible to coastal erosion owing to anthropogenic pressures in both the drainage basins and the coastal zone. This study investigates alterations in the shoreline of three Northeastern Brazilian deltas (São Francisco, Parnaíba, and Jequitinhonha) from the 1980s to 2021, correlating them with both human-induced and natural impacts. Multispectral imagery was utilized to assess horizontal changes in the shoreline through the DSAS software, providing insights into long-term trends across different decades. Additionally, variations in the active coastal area were analyzed for the same periods. Furthermore, for the São Francisco delta, sandbanks downstream of the Xingó dam were delineated using satellite imagery. Hydro-climatic data from stations proximate to the coastal zone were also incorporated into the study. The data reveals that the Parnaíba Delta demonstrated a progradation rate at its mouth surpassing 20 m/year, resulting in sedimentary gains of 6 km² across the delta. In contrast, the Jequitinhonha delta experienced predominant erosion processes at the mouth, characterized by rates below 10 m/year and an increased delta mouth protrusion angle of 13° from 1984 to 2021. The limited correlation of the active coastal area (R² = 0.49) suggests that sediments eroded at the mouth are transported, via bidirectional currents, to the delta's margins. Among the three deltas, the São Francisco delta exhibited pronounced erosion at the mouth, with losses exceeding 20 m/year, reaching up to 50 m/year. The angle of the mouth increased by 18° during the analyzed period, and there was a net loss of 6.2 km². Due to sparse human habitation along the coast, the construction of dams within approximately 100 km of the coastal zone has emerged as a significant contributing factor to erosion processes in the Jequitinhonha and São Francisco deltas. Prior to the construction of the Itapebi and Xingó dams, both deltas exhibited relative stability in their coastlines. However, post-dam construction, Net Shoreline Movement (NSM) data indicated a gradual increase in erosion at the mouths over time. Additionally, these structures reduced the annual and monthly variability of the lower river courses of the Jequitinhonha and São Francisco, resulting in a diminished capacity for riverbank erosion and sediment transport to the coastal area. For instance, within the São Francisco delta, spanning from 1984 to 2021, there was a reduction of 7.54 km² in the sandy banks downstream of the Xingó dam. This figure exceeds threefold the loss of active coastal area observed across the entirety of the delta. Notably, this phenomenon did not occur in the Parnaíba delta, as the Boa Esperança dam is situated 600 km away from the coastal zone. Climate change, alongside potential mining and dredging activities, may further alter the stability of the Parnaíba Delta and exacerbate erosion processes in the Jequitinhonha and São Francisco Deltas. Over the last two decades, northeastern Brazil has experienced a reduction of more than 30% in rainfall. IPCC data suggests a projected 60 to 70% reduction in rainfall in this region by 2100. Consequently, the capacity for river transport is expected to decrease significantly, thereby intensifying erosion processes in both deltas.Master Thesis Modelagem de reservatórios fraturados e carstificados usando afloramento análogo de alta resolução e análise de sensibilidade de cenários simulados(Universidade Federal do Rio Grande do Norte, 2024-03-04) Corrêa, Simone Nabuco; Bezerra, Francisco Hilario Rego; https://orcid.org/0000-0002-3512-5212; http://lattes.cnpq.br/6050302316049061; http://lattes.cnpq.br/3997804295045931; Perez, Yoe Alain Reyes; Erthal, Marcelle Marques; Vasconcelos, David Lino; Borges, Sérgio Vieira FreireThis study presents a multidisciplinary workflow to improve understanding of fractured and karstified carbonate reservoirs. The study seeks to uncover geological mechanisms behind fracturing and karstification by integrating analog outcrop fieldwork with regional correlation. This knowledge is crucial for constructing more accurate geological models and improving the management of these complex reservoirs. We use the Jandaíra Formation in the Potiguar Basin, Brazil, as an analog for fractured and karstified carbonate reservoirs. Our results focus on the Furna Feia cave, characterized by dissolution dome structures and NW-SE-trending conduits. Regional stratigraphic analysis identified lithofacies patterns and correlated system tract cycles to map more karstified layers, relating the cave formation to the SB-2 unconformity. Structural analysis revealed that rift faults, caves, and fractures are oriented NW-SE and NE-SW. The regional 3D geological model, covering an area of 30x14 km with 179 layers, integrates data from two wells, interpreted surfaces, fracture models (DFN), and karst features, revealing intensely dissolved layers between the SB-1 and SB-2 unconformities. Building upon this, we propose a new approach to karst modeling that combines conduits and karstified fractures following a comprehensive conceptual model. Four models were simulated to evaluate the water and oil production history, similar to analog carbonate reservoirs. We concluded that including karst and fractures improves performance, increasing production, but it affects some wells due to premature water breakthroughs. Therefore, effective management and optimized planning for wells are essential for reservoirs containing karst and fractures. This multidisciplinary workflow, from creating geological models to reservoir simulation, assesses different scenarios, providing insights into potential outcomes and associated risks that would influence decision-making in production development projects.Doctoral Thesis Explorando os controles estruturais e estratigráficos no Sistema Cárstico Furna Feia(Universidade Federal do Rio Grande do Norte, 2024-05-22) Dantas, Tarsila Barbosa; Bruna, Vincenzo La; Lima Filho, Francisco Pinheiro; http://lattes.cnpq.br/2605754911839657; https://orcid.org/0000-0002-7956-652X; http://lattes.cnpq.br/9411022785782518; Tavares, Aline Cristine; Vasconcelos, David Lino; Guadagnin, Felipe; Barbosa, José AntonioThe Furna Feia cave is the second largest cave in the state of Rio Grande do Norte and was developed along the Cretaceous carbonates of the Jandaíra Formation. The aim of this study was to analyze the geological indicators that affected the development of this karst system, combining surface and subsurface geological and geophysical data. Thus, a multidisciplinary approach was adopted, utilizing field visits, GPR, drones, LiDAR, gamma rays, porosity, permeability, uniaxial compressive strength, and petroglyph analysis. The cave is shallow, with a 766m linear development, meandering linear geometry, and its walls and ceiling exhibit domes and pockets. The identified facies associations were tidal bars at both the base and top of the cave, interspersed with lagoon facies association. Within this lagoonal interval, the rocks are intensely dolomitized. The base tidal bars indicate a paleocurrent towards the northwest, while the top tidal bars indicate a northeast direction. LiDAR data showed that the dolomitized interval is also the most dissolved, where the cave exhibits the greatest widening. This interval also showed the highest amount of fracturing in GPR data and field analyses. Contrarily, this interval presents the lowest porosity and permeability values in its matrix. Additionally, structural analyses also showed a tectonic influence on the development of this karst system. The Poço Verde Fault, trending northwest, affected the orientation of both the galleries and the pockets and domes found in the cave. Therefore, we conclude that dolomitization exerted the greatest control over the formation of the cave, as it allowed for the highest concentrations of fracturing and consequent horizontal fluid percolation for subsequent dissolution of the carbonates. Tectonics, on the other hand, guided this dissolution in preferred directions (northwest and northeast). These findings can be extrapolated and used as guidelines for carbonate reservoirs affected by the same processes and indicate a dual porosity behavior for these rocks.Master Thesis Aplicação de aprendizado de máquina para estimativa da permeabilidade utilizando dados de RMN de rochas análogas a reservatório(Universidade Federal do Rio Grande do Norte, 2024-08-19) Mafra, Mauricio Gabriel Lacerda; Xavier Júnior, Milton Morais; http://lattes.cnpq.br/3128669965557866; https://orcid.org/0000-0003-2720-4655; http://lattes.cnpq.br/7598665592966289; Marques, Manilo Soares; Souza, André Alves deThis master's thesis explores the relevance of studies on rocks analogous to reservoirs, with a primary focus on the petrophysical permeability parameter. Traditional petrophysical techniques provide absolute values for this parameter but offer limited insights into the underlying reasons for these values. The absence of precise information necessitates the use of more advanced techniques for a systematic reservoir analysis. While Nuclear Magnetic Resonance proves effective in obtaining advanced reservoir information, its analytical models for permeability lack accuracy, particularly in heterogeneous reservoirs, revealing certain limitations. Filling this gap, this study aims to improve permeability predictions by employing machine learning models such as Random Forest, Gradient Boosting, and Multi-Layer Perceptron. The goal is to predict permeability based on patterns obtained through Nuclear Magnetic Resonance, compare them with analytical models, and identify the model that best suits the reservoir. It was observed that machine learning models provided more accurate predictions compared to analytical models.