http://localhost:8080/tede/handle/tede/3 2026-11-13T08:56:45Z http://localhost:8080/tede/handle/tede/232 “ARQUITETURA DE UM SISTEMA VULCÂNICO KAMAFUGÍTICO NA PROVÍNCIA ÍGNEA DO ALTO PARANAÍBA A PARTIR DE DADOS AUDIOMAGNETOTELÚRICOS E ANÁLISES COMPLEMENTARES” Lucca Martins Franco, Lucca Martins Franco Emanuele Francesco La Terra , Emanuele Francesco La Terra This study investigates the geolectrical and structural architecture of a volcano-sedimentary system associated with a kamafugite occurrence in the Alto Paranaíba Igneous Province, southeastern Brazil. Kamafugites are ultrapotassic alkaline volcanic rocks with significant economic potential for the agricultural sector and for rare-earth element exploration. However, characterizing these bodies in the subsurface remains challenging, particularly in ancient and stabilized volcanic systems, where their physical properties are not controlled by active thermal processes. To address this issue, audiomagnetotelluric data were integrated with complementary geophysical methods, including seismic reflection and magnetometry, as well as geological and petrographic descriptions and geochemical data. The analysis of electromagnetic data was carried out using established methodologies, including dimensionality analysis, sensitivity tests, three-dimensional inversion, and forward modeling for conductor testing. The resulting resistivity models were interpreted alongside structural and lithological data, thereby constraining the geometry and physical properties of subsurface units. The results reveal a complex geolectrical framework, primarily controlled by mineralogical alteration processes and fluid circulation along structural discontinuities. Conductive zones are interpreted as regions of intense hydrothermal alteration and fluid accumulation, whereas resistive domains are associated with more preserved volcanic units and sedimentary sequences. The proposed model indicates that fluid percolation along faults and fractures plays a fundamental role in modifying the physical properties of the studied volcano-sedimentary succession. The results contribute to understanding ancient volcanic systems, demonstrate the applicability of the audiomagnetotelluric method for characterizing volcanic rocks in the subsurface, and provide support for evaluating alternative agricultural inputs in Brazil. Observatorio Nacional Tese 2026-04-30T00:00:00Z http://localhost:8080/tede/handle/tede/231 “IMAGEAMENTO GEOELÉTRICO DA BACIA DO PARNAÍBA POR MEIO DA INVERSÃO MAGNETOTELÚRICA DETERMINÍSTICA E BAYESIANA” Gonzalo Gadafi Romero Beltran, Gonzalo Gadafi Romero Beltran Emanuele Francesco La Terra , Emanuele Francesco La Terra The objective of this thesis is to improve the understanding of the internal structure and tectonic framework of the Parnaíba Basin by applying the magnetotelluric (MT) method, within the framework of the Parnaíba Basin Analysis Project (PBAP). The Parnaíba Basin is located in northeastern Brazil, where a thick Phanerozoic sedimentary sequence covers most of the basin, and the presence of magmatic intrusions represents a key element in the geodynamic evolution of the basin. The MT dataset used in this research consists of 218 broadband magnetotelluric (BBMT) stations and 37 long-period magnetotelluric (LMT) stations, distributed along a profile crossing the basin in an E–W direction. The data were analyzed and processed using robust techniques, ensuring the quality and reliability of the resulting magnetotelluric responses. Subsequently, the data were modeled and inverted using both deterministic and probabilistic inversion methodologies. In this context, this thesis is organized into two main parts, each focusing on the characterization of the deep structure of the Parnaíba Basin at different scales of analysis. The first part consists of obtaining crustal-scale resistivity models through 3D deterministic inversion strategies. The inversion results reveal the presence of three contiguous lithospheric blocks that constitute the Parnaíba Basin. From west to east, these correspond to the Amazonian Craton, the Parnaíba Block, and the Borborema Province, separated by lithospheric-scale resistive discontinuities. Within each block, the models display distinct geoelectrical characteristics. The Amazonian Craton exhibits a conductive domain, possibly associated with the replacement or modification of a previously delaminated lithosphere. The Parnaíba Block, in turn, is composed of two distinct tectonic domains: the highly resistive Grajaú Block and the more conductive Teresina Block. This resistivity contrast is primarily related to magmatic activity, which is more pronounced in the Teresina domain, although it may also be influenced by Cretaceous extensional events associated with the opening of the South Atlantic Ocean. In the Borborema Province, resistive and conductive signatures observed at lower crustal depths provide evidence of collisional processes associated with its Neoproterozoic formation. Overall, these deep resistivity models provide new insights into the crustal amalgamation of the Parnaíba Basin and contribute to a better understanding of the tectonic processes that shaped Western Gondwana. The second part of this research focuses on the characterization of the shallow structure of the basin (~ 3–4 km depth) through the application of 1D Bayesian trans-dimensional inversion approach based on Markov chain Monte Carlo (MCMC), which allow uncertainties associated with non-1D effects in the data to be properly accounted for. Furthermore, by integrating magnetotelluric data with structural information and well data, and through the application of the Bayesian Estimate Fusion (BEF) approach, it was possible to construct a robust model of basement geometry. This approach also enabled the identification of the sedimentary cover-basement interface, as well as highly conductive anomalies within the sedimentary sequence, particularly associated with the Poti and Cabeças formations, which are linked to hydrocarbon reservoirs in the Parnaíba Basin. These results provide a more detailed view of the shallow architecture of the basin and its economic potential. Overall, the results obtained in this thesis significantly contribute to the understanding of both the deep and shallow structure of the Parnaíba Basin, providing key insights into its tectonic evolution as well as valuable information for future hydrocarbon exploration. Keywords: Parnaíba Basin, Magnetotellurics, 3D inversion, 1D Probabilistic inversion, Markov Chanin Monte Carlo (MCMC), Bayesian Estimate Fusion, West Gondwana Formation, Hydrocarbon Exploration Observatorio Nacional Tese 2026-05-28T00:00:00Z http://localhost:8080/tede/handle/tede/218 “Magnetita em rochas carbonáticas: implicações para a recuperação de hidrocarbonetos e caracterização petrofísica por RMN” Jonatã Barbosa Teixeira, Jonatã Barbosa Teixeira Daniel Ribeiro Franco, Daniel Ribeiro Franco The presence of magnetite (Fe3O4) in petroleum systems represents an important factor in understanding inaccuracies related to carbonate formations, which influence both exploration and the petrophysical analysis of these reservoirs. In this doctoral thesis, we investigate the effects of synthesized magnetite, using the co-precipitation method, in various grain sizes and concentrations, exploring its relationship with the pore space in different porosities and the fluid present in the reservoir. The results consist of two main articles. The first article investigates how pH variations induced by acid affect the surface properties and catalytic and leaching activities of nanometric and micrometric magnetites, particularly in the presence of naphthalene. These changes are crucial for chemical decomposition processes in carbonate reservoirs. By analyzing catalytic performance under different pH conditions, the project provides valuable insights into the potential environmental impacts and practical applications of acid fracturing, particularly relevant to Enhanced Oil Recovery (EOR). It was noted that under acidic conditions, the Fe2+ ions leached from magnetite oxidize naphthalene, revealing their crucial role in the chemical decomposition of organic substrates in oil extracted from rocks containing magnetite. It was discovered that the chemical and crystallographic structure of magnetite significantly influences the decomposition of naphthalene, used as a model of Polycyclic Aromatic Hydrocarbon (PAH). Additionally, the morphology of magnetite grains, whether micro or nanometric, plays an important role as a heterogeneous catalyst, along with the acidity of the aqueous medium. Homogeneous catalysts demonstrated greater efficiency in decomposing naphthalene, followed by samples of nanometric and micrometric magnetite, which act as heterogeneous catalysts. The second article employs laboratory methods to investigate the interferences that magnetites may cause in Nuclear Magnetic Resonance (NMR) spectra and consequently in petrophysical estimates based on NMR. Twelve synthetic carbonates with different concentrations of magnetites and varying porosities were prepared, and mineralogical and magnetic characterizations were performed. Furthermore, the study included gas porosimetry analyses and permeability estimation using a permeameter. It was observed that shifts in the T2 spectrum are strongly correlated with increased magnetic susceptibility. The gradient of diffusive relaxation contributed to the overlap of the magnetic susceptibility of carbonates concerning the amount of porosity in samples with higher magnetite concentrations, while in carbonates with lower amounts of magnetite, the surface relaxivity modulated the T2 curve. These results show a strong correlation between the rate of diffusive relaxation and the concentration of magnetite. It is emphasized that to utilize relaxation rates from NMR in estimating porosity and permeability in carbonate rocks, one must consider the effects caused by magnetite. In summary, these studies represent a significant contribution to advancing knowledge in the characterization of magnetic minerals in carbonate formations of petroleum systems, exploring their interaction with pore space, their filling, and enhancing the understanding of pore potential. This provides insights for future research on chemical reactions in the magnetic characterization of carbonates, enhanced oil recovery, and the estimation of porosity and permeability based on T2 spectra. Observatorio Nacional Tese 2025-04-29T00:00:00Z http://localhost:8080/tede/handle/tede/200 “ANÁLISE CICLOESTRATIGRÁFICA DOS DEPÓSITOS SEDIMENTARES DA BACIA POTIGUAR DURANTE O INTERVALO CENOMANIANO-TURONIANO” Evelyn Paiva do Nascimento, Evelyn Paiva do Nascimento Daniel Ribeiro Franco, Daniel Ribeiro Franco Exploratory sedimentary basins require continuous chronostratigraphic refinement. However, in continental settings, this remains challenging due to the complex and dynamic erosional processes of fluvial and fluvio-estuarine systems, which often obscure the depositional record. Consequently, investigating the influence of orbital cycles - an approach that can aid in refining chronostratigraphic frameworks - in these records is also a challenge. As a result, studies on this topic are relatively uncommon in the literature, despite the growing recent interest from the scientific community. In this context, the fluvio-estuarine deposits of the Açu Formation, in the Potiguar Basin - an important exploratory basin located on the Brazilian equatorial margin - represent an special sedimentary archive in which T-R cycles can be traced laterally for tens of kilometers. This makes them an interesting subject for cyclostratigraphic analysis in non-marine environments. This study investigates the influence of orbital forcing on the Açu Formation, correlate cycles influenced by orbital variations in the wells, and establish the preserved time interval through the construction of an Astronomical Time Scale (ATS). Cyclostratigraphic analyses were performed using time series techniques on gamma-ray logging data from three wells, focusing on two third-order sequences deposited from the Cenomanian-Turonian boundary (approximately 101 to 93 million years ago). Statistical methods including correlation coefficient (COCO) and the null hypothesis (H0), were applied to determine the ideal sedimentation rate (SAR) and test the record of astronomical cycles. The Integrated Error Prediction Filter Analysis (INPEFA) was used to identify trends in the sedimentary record, improving the correlation of matching cycles. The cyclostratigraphic results demonstrate the imprint of orbital forcing on the sedimentary deposits, consistent with the astronomical solutions for the Cenomanian-Turonian interval. The inferred sedimentation rates range from approximately 3 to 8 cm/kyr, consistent with similar depositional environments. The identification of spectral bands corresponding to the long eccentricity cycle (405 ka) allowed for the construction of a floating ATS for the Cenomanian-Turonian interval in the basin and the estimation of the recorded time. Since the good preservation of orbital signals in fluvio-estuarine environments is uncommon - limiting the number of cycle-stratigraphic studies - this research provides important insights into the behavior of orbital signals and basin filling in this type of paleoenvironment. Furthermore, as this interval includes hydrocarbon-bearing deposits, the findings contribute to the advancement of cyclostratigraphic studies in exploratory basins, with potential applications for chronostratigraphic correlation. Observatorio Nacional Dissertação 2025-06-13T00:00:00Z