3 research outputs found
O lineamento transbrasiliano na Bacia do Paraná : compartimentação crustal do embasamento e reativações fanerozóicas
Tese (doutorado)—Universidade de BrasÃlia, Instituto de Geociências, 2015.A Plataforma Sul Americana inclui dois importantes componentes geológicos de escala continental e com raÃzes estruturais em comum: o Lineamento Transbrasiliano (LTB) e a Bacia do Paraná. Importante relação entre os dois ocorre na região entre o Arco Magmático de Goiás e a Faixa Paraguai, que impõem particularidades estruturais obscurecidas pela cobertura sedimentar da Bacia do Paraná. A área, alvo desse estudo, é recoberta por dados aerogeofÃsicos, magnéticos e gravimétricos, adquiridos com diferentes resoluções. Sua integração permitiu gerar mapas de anomalias magnéticas e anomalias Bouguer, este incluindo dados terrestres.Técnicas de processamento e modelagem geofÃsica foram utilizadas com objetivo de esclarecer a disposição de compartimentos crustais e estruturas do embasamento da bacia em diferentes nÃveis de profundidade. Três grandes descontinuidades magnéticas do LTB limitam compartimentos crustais na área, de leste para oeste: lineamentos Serra Negra, Baliza e General Carneiro, com direções gerais N30°E, N60°E e N70°E, respectivamente, que separam mudanças significativas no background gravimétrico, ainda subdividido por lineamento adicional N50°W, São Vicente. Análise de lineamentos de 1ª, 2ª e 3ª ordens aponta a predominância de orientações NE, interpretadas como originalmente brasilianas e reativadas no Jurássico-Cretáceo, e direções NW, bem marcadas nas unidades sedimentares da bacia e com caráter distensivo, atribuÃdo a reativação mesozóica. Análise do matched-filter aplicada a dados magnéticos e gravimétricos, com suporte da deconvolução de Euler e tilt-depth, aponta estimativas de profundidades importantes: (i) 2,5 km, relacionado ao topo do embasamento da Bacia do Paraná; (ii) 6 km, atribuÃdo ao topo do embasamento da bacia neoproterozóica (Grupo Cuiabá); (iii) 20 km, possivelmente associado à interface crosta superior/inferior; e (iv) 33-39 e 43 km, relativos à s espessuras crustais a oeste e sudeste do lineamento Serra Negra, respectivamente. A crosta a leste é formada pelo o Arco Magmático de Arenópolis e o limite noroeste do Bloco Paranapanema e a oeste é constituÃda por zona de transição crustal e o paleocontinente Amazônico. A modelagem geofÃsica conjunta 2D com dados gravimétricos e magnéticos esclarece a geometria assimétrica do embasamento da bacia, configurando pelo menos três meiográbens formados ao longo de estruturas reativadas do LTB. A região entre os lineamentos Serra Negra e General Carneiro caracteriza-se por menor espessura e maior fraqueza crustal, onde importantes estruturas se desenvolveram no Mesozóico: desde reativações com direção NW, vinculadas a soerguimento crustal e à implantação de pequenas bacias cretáceas alinhadas a NE. Dois depocentros importantes ocorrem: a norte do lineamento General Carneiro, com direção N70°E, e a leste da falha Serra Negra, com direção N30°E – NS.The South American Platform includes two major geological components of continental scale with common structural roots: the Transbrasiliano Lineament (LTB) and the Paraná Basin. An important relationship between the two is observed in the region between the Goiás Magmatic Arc and the Paraguay Belt, which impose structural features concealed by the sedimentary cover of the Paraná Basin. This region comprises our study area, and is covered by airborne magnetic and gravity surveys, acquired with different resolutions. These data were integrated to generate maps of magnetic and Bouguer anomalies, the latter included ground data. Data processing and geophysical modeling techniques were used in order to reveal the disposition of crustal compartments and the basin basement structures at different depths. Three large magnetic discontinuities limit crustal compartments in the area, from east to west: Serra Negra, Baliza and General Carneiro lineaments, with N30°E, N60°E and N70°E trending alignments, respectively, which separate significant changes in the gravity background, still subdivided by the additional Sao Vicente lineament, N50°W. Analyses of 1st, 2nd and 3rd order lineaments indicate predominance of NE trending directions, which were interpreted as Brasiliano structures, reactivated in the Jurassic-Cretaceous. NW directions, well-marked in the sedimentary units of the basin and with extensional character, were attributed to Mesozoic reactivation. Matched-filter analysis applied to magnetic and gravity data, supported by the Euler deconvolution and tiltdepth, yielded important depths estimates: (i) 2.5 km to the top of the Paraná Basin basement; (ii) 6 km to the top of the Neoproterozoic Basin basement (Cuiabá Group); (iii) 20 km, possibly associated with the upper/lower crust interface; and (iv) 33-39 and 43 km related to crustal thicknesses west and southeast of the Serra Negra lineament, respectively. To the east, the crust is formed by the Arenópolis Magmatic Arc and the northwest boundary of Paranapanema Block, while to the west it consists of a crustal transition zone and the Amazon paleocontinent. The 2D geophysical modeling based on gravity and magnetic data sheds light on the asymmetric geometry of the basement of the basin, with at least three half-grabens formed by LTB reactivated structures. The region between the Serra Negra and General Carneiro lineaments is characterized by thinner crust and higher crustal weakness, where important structures have developed in the Mesozoic, including NW trending reactivations, linked to crustal uplift and deployment of small NE-aligned Cretaceous basins. Important depocenters occur: the first, to the north of General Carneiro lineament, and the second, to the east of the Serra Negra fault, with N70ºE and N30°E – NS trending directions, respectively
The Geomagnetic Field Transformants and Their Complexing with Data of Gravitational, Thermal and Radioactive Fields: During the Exploration of Hydrocarbon Fields at the Southern Part of the Ustyurt Region
The chapter discusses the results of the interpretation of aeromagnetic survey data in the southern part of the Ustyurt region in order to identify zones that are heterogeneous in magnetic properties, with their subsequent tie-up with areas promising for the detection of hydrocarbon accumulations. Three tectonic elements are distinguished—the Central Ustyurt system of disturbances, the Shakhpakhty step and the Assakeaudan depression according to the sign, orientation and quantitative values of the transformants of the geomagnetic field, and, consequently, according to the depth and extent of distribution of magnetized rocks, based on the degree of deformation of lithological-stratigraphic complexes and levels by deep faults. Within these tectonic elements, the transformants of the geomagnetic field were comprehensively interpreted with the data of gravitational, thermal and radiochemical fields to increase the reliability of the results of geological interpretation. This made it possible to study the behavior and characteristics of faults, to draw conclusions about the depth of gravitational and magnetically disturbing masses, about the degree of geological heterogeneity of large geostructures, as well as to trace the nature of the manifestation of local structures in geophysical fields. The Central Ustyurt system of dislocation, the Shakhpakhty step and the Assakeaudan depression differ in varying degrees of active tectonics and differentiation by the degree of dislocation of oil and gas prospective objects, fragmentation by faults, by the extent of distribution of reservoir rocks and oil and gas source suite, conditions of conservation of hydrocarbon accumulations, directions and channels of probable hydrocarbon migration, and assumptions are made about the relationship of oil and gas prospective structures and explored hydrocarbon field with large deep faults. The author’s studies of transformants of magnetic and gravitational fields, geothermal and aerogamma spectrometry data clearly indicate in favor of the prospects of oil and gas potential of local structures of the Shakhpakhty step: Utezhan, Kozhantai, Northern Kozhantai, Otynshy. In general, the results obtained will serve as a reliable basis for clarifying and detailing the geological and structural-formation models of the Southern Ustyurt, which can be used as the basis for the design of geological exploration for the exploration of new hydrocarbon field using expensive and time-consuming seismic exploration of CDP-3D and deep drilling