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Title: Aplicação dos métodos gravimétrico e magnetométrico para a definição do comportamento estrutural da faixa de dobramentos Araguaia
metadata.dc.creator: CARVALHO, João da Silva
metadata.dc.contributor.advisor1: SAUCK, William August
Keywords: Prospecção - Métodos geofísicos
Goiás - Estado
Pará - Estado
Maranhão - Estado
Issue Date: 25-Apr-1988
Publisher: Universidade Federal do Pará
Citation: CARVALHO, João da Silva. Aplicação dos métodos gravimétrico e magnetométrico para a definição do comportamento estrutural da faixa de dobramentos Araguaia. 1988. 127 f. Dissertação (Mestrado) - Universidade Federal do Pará, Centro de Geociências, Belém, 1988. Disponível em: Acesso em: .
Abstract: Interpretation of gravimetric and aeromagnetometric informations of the northern region on the Araguaia Orogenic Belt covering an area of aproximately 129.000km2 is presented in this thesis. The area lies between is 47º50’W and 50º30’W longitudes and between 4º50’S and 9º00’S latitudes, over southeast Pará State, north-northwest of Goiás State and west of Maranhão State. The gravimetric and altimetric measurements were carried out along highways and roads in the region. The gravity data, after corrections and reductions are presented in the form of Bouguer anomalies map on scale 1:500.000. The gravimetric pattern of Araguaia Orogenic Belt shows features principally of longitudinal extension, with approximately meridional direction. These features are correlated with the known lithological and structural units in the area. In the central-meridional portion of the map, appears an extended zone of intensive negative anomaly (less than -100mgal). This zone suffers two inflexios, one in the northwest (NW) which correlates to Carajás Lineament, and the other along latitude 5°30’S. The higher gravimetric values, notably in the northwest portion (cratonic domain), are related to the influence of the metavulcanics Grão Pará Group, and those in the northeast portion are attribuited to the denser mass intruded in the crust. Notable, also a gravimetric peak on the eastern flank of the brachyanticlines. This peak could be linked to a denser mass placed under this region tectonially, creating elevations in crust base-level and consequently of the basement. Generally, the eastern flank of orogenic belt show a gradient more intensive than the western, due to principally the geometric configuration of structures. In the similar way there is a notable ascendent regional gradient from south to north. Through the analysis of magnetic intensity maps, of the Projeto Geofísico Brasil-Canadá (PGBC), diferent individual domains were identified. These domains correlate lithologically and structuraly with the geotectonics units that constitute the regional framework and their subunits. Analytical gravity and magnetic modelling were carried out for semi-quantitative interpretation with the objective to establish the basement geometric pattern of the Araguaia Orogenic Belt, and the vinculated structures. On the basis of gravimetric informations, we could verify a geometric higher pattern in the form of imbricated slices over the substratum. The higher negative anomaly in the center-meridional portion of the orogenic belt could be related with the deficiency of deeper mass (a depression in the crust bottom), or due to the presence of a low density mass in the supercrustal layers, in that zone. The gravity depression in the southwest of the area, between Guarai and Tupirama, could be attribuited to a depression in the basement, and in the similar way the negative anomaly associated with Carajás Lineament is related to a sinformal structure.
Appears in Collections:Dissertações em Geofísica (Mestrado) - CPGF/IG

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