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Previous issue date: 2015-09-25 / Ag?ncia Nacional do Petr?leo - ANP / O objetivo deste estudo foi caracterizar a express?o estrutural-geof?sica do Lineamento Transbrasiliano na por??o centro-leste da Bacia do Parna?ba. O Lineamento Transbrasiliano (LTB) corresponde a uma megazona de cisalhamento de idade neoproterozoica (Ciclo Brasiliano), com dire??o NE-SW e cinem?tica transcorrente dextral, ocorrendo subjacente (e exposta lateralmente nas bordas NE e SW) ? se??o sedimentar da Bacia do Parna?ba. No presente trabalho, a interpreta??o dos mapas de anomalias gravim?trica e magn?tica ? analisada face a essa cinem?tica do LTB, sendo que a assinatura das anomalias geof?sicas corresponde ?s etapas de evolu??o brasiliana a tardi-brasiliana, de temperatura alta e declinante. Verifica-se que o padr?o das anomalias gravim?tricas residuais ? compat?vel com um par S-C dextral, moldando os corpos geol?gicos do embasamento heterog?neo. As bandas C, com dire??o NE, devem ser constitu?das por fatias de gnaisses e granulitos (anomalias positivas), rochas gran?ticas ou metassedimentares de baixo grau e grabens pr?-silurianos em estilo pull-apart (anomalias negativas). J? as anomalias de tra?os curvil?neos no mapa gravim?trico identificam trends contracionais (de superf?cies S), incompat?veis com a sua interpreta??o como um graben pr?-siluriano, restando as demais alternativas citadas. No tocante ? interpreta??o dos trends no mapa de anomalias magn?ticas (reduzidas ao polo), a maior parte destes ? tentativamente associada a falhas ou zonas de cisalhamento de baixa temperatura (planos C), delimitando blocos distintos em termos de propriedades magn?ticas, e/ou preenchidas por corpos b?sicos. ? tamb?m poss?vel que algumas anomalias magn?ticas isoladas/pontuais correspondam a corpos ?gneos de idade tardi-brasiliana ou mesozoicos. A configura??o desses lineamentos no embasamento pode ser interpretada em analogia ao modelo de fraturas de Riedel, assumindo planos de mergulho acentuado e com se??o de movimento sub-horizontal. Nesta disserta??o, s?o tamb?m exploradas interpreta??es relativas a modelagens gravim?tricas 2D combinadas com a interpreta??o de uma linha s?smica dip ao Lineamento Transbrasiliano. A se??o de rochas equivalente ao Grupo Jaibaras mostrou anomalias gravim?tricas discretas da bacia, conferindo assim uma maior influ?ncia ?s estruturas do embasamento nas respostas gravim?tricas. A delimita??o dos grabens sotopostos ? se??o paleozoica da bacia sofre restri??es causadas pelas heterogeneidades e anisotropia do embasamento. / The objective of this study was to characterize the structural-geophysical expression of the Transbrasiliano Lineament (TBL) in the east-central portion of the Parna?ba Basin. The TBL corresponds to a major Neoproterozoic NE-trending shear zone related to the Brasiliano orogenic cycle, with dextral strike-slip kinematics, underlying (but also laterally exposed in the NE and SW basin edges) the sedimentary section of the Parna?ba Basin. In this study, the interpretation of gravity and magnetic anomaly maps is consistent with the TBL kinematics, the signature of the geophysical anomalies corresponding to the high (plastic behaviour) and subsequent declining temperature (ductile to brittle behaviour) stages during Brasiliano and late Brasiliano times. The pattern of residual gravity anomalies is compatible with an S-C dextral pair shaping the geological bodies of an heterogeneous basement, such as slices of gneisses and granulites (positive anomalies), granitic and low-medium grade metasedimentary rocks (negative anomalies). Such anomalies curvilinear trends, ranging from NNE (interpreted as S surfaces) to NE (C surfaces), correspond to flattening surfaces (S), while the NE rectilinear trend must represent a C band. The narrower magnetic anomalies also display NNE to NE (S surfaces) trends and should correspond to similar (although narrower and more discontinuous) sources in the equivalent anomaly patterns. Pre-Silurian pull-apart style grabens may contribute to the NE negative gravimetric anomalies, although this interpretation demands control by seismic data analysis. On the other hand, the curvilinear anomalies associated to contractional trends are incompatible with their interpretation as pre-Silurian graben, in both maps. In the (reduced to the pole) magnetic anomalies map, most of these are again associated to low-temperature shear zones (C planes) and faults, juxtaposing distinct blocks in terms of magnetic properties, or eventually filled with basic bodies. It is also possible that some isolated magnetic anomalies correspond to igneous bodies of late-Brasiliano or Mesozoic age. The basement late discontinuities pattern can be interpreted in analogy to the Riedel fractures model, with steep dipping surfaces and a sub-horizontal movement section. This study also explored 2D gravity modeling controlled by the interpretation of a dip seismic line as regards to the Transbrasiliano Lineament. The rock section equivalent to the Jaibaras Group occupying a graben structure (as identified in the seismic line) corresponds to a discrete negative anomaly superimposed to a gravimetric high, once again indicating a stronger influence of older crystalline basement rocks as gravimetric sources, mainly reflecting the heterogeneities and anisotropies generated at high temperature conditions and their subsequent cooling along the TBL, during the Brasiliano cycle.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/21066 |
| Date | 25 September 2015 |
| Creators | Lima, Thuany Patr?cia Costa de |
| Contributors | 06892922449, http://lattes.cnpq.br/4094827215552998, Silva, Carlos Cesar Nascimento da, 81352921472, http://lattes.cnpq.br/5136096872133075, Xavier Neto, Pedro, 16361121372, http://lattes.cnpq.br/0420885770350995, Jardim, Emanuel Ferraz |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM GEODIN?MICA E GEOF?SICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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