http://hdl.handle.net/11422/55 2026-07-30T02:52:53Z http://hdl.handle.net/11422/29831 Title: Assinatura geoquímica de columbita-tantalita e levantamento radiométrico de pegmatitos radioativos da região de Parelhas, Rio Grande do Norte, Brasil Author(s)/Inventor(s): Moura, Jorge Costa de Advisor: Ludka, Isabel Pereira Abstract: This thesis is the result of geochemical, structural and radiometric investigations on radioactive pegmatites of the Borborema Pegmatitic Province in Northeast Brazil. The studied area, located in the surroundings of the city of Parelhas in the region of the Serra da Borborema, is well known for its thousands of pegmatitic bodies exploited in primitive mines called garimpos. The main goal was to find an efficient, cheap and routine inspection procedure to identify the origin of commercialized radioactive columbite-tantalite (coltan) ore. The Brazilian Nuclear Energy Agency (CNEN) controls uranium commerce and nuclear activity in Brazil. Without an effective method to characterize coltan ores from different localities it is impossible to control the trade. The here presented new method was developed by correlating structural features of these pegmatites with the geochemical behavior of their coltan samples. It was found that the variation of the ratio U/Th versus Nb2O5/Ta2O5 provides geochemical signatures (analytical fingerprints) for the source location of such ore. A test of the new method with coltan samples of commercial batches from the Brazilian states Amapá and Rondônia also generated distinct geochemical signatures. A radiometric survey (CPS) was carried out in several mines and pegmatites to study the environmental impact of gamma radiation. It included in situ measurements of pegmatite walls, host rocks, soil, and accumulated water and revealed that gamma emitters are hardly solubilized and environmental gamma radiation therefore generally is not enhanced to a dangerous level Publisher: Universidade Federal do Rio de Janeiro Type: Tese 2013-09-11T00:00:00Z http://hdl.handle.net/11422/29774 Title: Os esfagessaurídeos da Bacia Bauru Author(s)/Inventor(s): Iori, Fabiano Vidoi Advisor: Carvalho, Ismar de Souza Abstract: The Notosuchia was a characteristic and peculiar group in the geological history of the Gondwanic Cretaceous. These crocodylomorphs possessed a very specialized dentition and occurred in several ecological niches. In this context the sphagesaurids present a complex masticatory mechanism adapted for herbivory / omnivory. Four genera have been described for this family: Sphagesaurus, Armadillosuchus, Caipirasuchus and Caryonosuchus, all from the Bauru Basin. This basin is located in south-central South American Platform and consists of Late Cretaceous continental deposits. The descriptions of some sphagesaurids were based on the fragmentary fossils and/or uncompleted preparation; then some morphological characters were incorrectly described. The anatomical reanalysis and the discovery of new specimens allowed the taxonomic revision and annotation of a diagnosis for the family based on the following dental pattern: presence of six sphagesauriform teeth in each maxilla and six on each dentary, each upper tooth with an antagonic tooth in the jaw; premaxilla with a caniniform tooth and another conical tooth posteriorly. Adamantinasuchus possess distinct dentition and chewing mechanism; theses aspects and a phylogenetic analysis exclude it from the family Sphagesauridae. The analysis of new aspects related to chewing on Caipirasuchus corroborated previous proposals for the family, as the proal and unilateral movements of the jaw during the bite. Moreover, it was pointed the function of the diastemata and square-articular joint in the masticatory process. The study of the post-cranium of the Caipirasuchus specimens allowed to estimate that these animals had thin bodies and 1.20 m in length. The analysis of anatomical structures of Sphagesaurus, Caryonosuchus, Armadillosuchus allowed to propose an ecological niche for the Sphagesauridae Publisher: Universidade Federal do Rio de Janeiro Type: Tese 2013-12-05T00:00:00Z http://hdl.handle.net/11422/29445 Title: Análise de sismossequências na Seção Drifte da porção offshore da bacia de Barreirinhas, margem equatorial brasileira Author(s)/Inventor(s): Sampol, Juliana Ferreira Gomes Advisor: Borghi, Leonardo Abstract: Important discoveries made over recent years in the South American (Zaedyus discovery) and African (Jubilee Field) equatorial margins opened new perspectives in the exploration of the Brazilian equatorial margin, particularly for the Barreirinhas Basin. The objective of this study is a first seismic analysis approach for the Drift section of Barreirinhas Basin, in deep water areas, based on the identification, correlation and mapping of the seismic facies, horizons and sequences. The few stratigraphic data available together with the lack of stratigraphic interpretations in the studied area make this study challenging. Five 2D depth seismic lines (Pre-Stack Depth Migration) dip oriented and one strike oriented are located in an approximately 1100km2 area, in the offshore Barreirinhas Basin, were interpreted using Petrel (Schlumberger), and its applications. The analysis of seismic characters, impedance contrast, reflectors’ patterns, and sequence geometries showed nine seismic facies, and ten seismic horizons, which seven of them limit six seismic sequences. Geometries identified by isopach maps of the sequences reveals a stratigraphic pattern of aggradational (seismic sequence 1) to retrogradational (seismic sequences 2, and 3) to progradational (seismic sequences 4 and 5) and finally to retrogradational (seismic sequence 6) which can be associated to transgressive-regressive cycles which allowed attemptive correlation to depositional sequences in the onshore previously proposed by literature Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação 2015-10-21T00:00:00Z http://hdl.handle.net/11422/29421 Title: Estruturas sedimentares microbianas em arenitos da Formação Sergi (Jurássico), Bacia do Recôncavo, Bahia, Brasil Author(s)/Inventor(s): Avalone, Maiana Cláudia Kreff Advisor: Borghi, Leonardo Abstract: The bosedimentology is a new area of knowledge in geosciences which studies the influence of microbial organisms in sedimentological processes. Within this new area, there are more traditional studies in carbonate rocks, but more recently, a new focus on the genesis of certain structures in sedimentary sandstones and shales that occur from the precambrian to recent has opened new possibilities for studying biosedimentogy in terrigenous sediments and rocks. This study aims to identify the microbial influence in the genesis of some sedimentary structures in eolian sandstones of Sergi Formation, Jurassic of Recôncavo basin. Several structures have been recognized in this formation, similar to those which has been identified in the literature as elephant skin, pinnacles, wrinkle marks, exfoliating sand laminae and domal buildups, and microscopic structures such as laminations with peculiar spatial arrangement of grains and heavy mineral concentration, all which are associated with microbial genesis. The correct diagnosis of these structures not only increases the descriptive capacity of sedimentary lithofacies for the Sergi Formation, as well as the paleoenvironmental interpretative ability of the formation, through the possibility of recognition of humid aeolian depositional systems (paleoenvironments of interdune / sand sheet), that had not yet been hypothesized in the literature of the basin Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação 2013-03-20T00:00:00Z