Produção Nacional
DETECTABILIDADE MAGNÉTICA DE DIQUES DO ARCO DE PONTA GROSSA: UM ESTUDO INTEGRADO DE MAGNETOMETRIA TERRESTRE/AÉREA E MAGNETISMO DE ROCHA
1991; Sociedade Brasileira de Geologia; Volume: 21; Issue: 4 Linguagem: Inglês
10.25249/0375-7536.1991317327
ISSN2177-4382
AutoresNAOMI USSAMI, ALEXANDRE KOLISNYK, María Irene Bartolomeu Raposo, Francisco José Fonseca Ferreira, EDER C. MOLINA, Márcia Ernesto,
Tópico(s)Inertial Sensor and Navigation
ResumoMAGNETISM STUDY.Mesozoic Ponta Grossa Arch Dyke Swarms occur between the eastern border of the Paraná basin and the southeastern Brazilian continental margin.It comprises of a few to a hundred meters-thick tholeiitic dykes which intrude the Precambrian basement and Paleozoic sediments preferably along the NW direction.Preliminary analysis of aeromagnetic data suggested that these dykes may extend northwesterly towards the center of the Paraná basin, under basaltic flows and post-volcanic sediments.In order to investigate the detectability of these non-exposed dykes by conventional airborne magnetometry, a combined study of ground/airborne magnetometry and dyke magnetism was carried out in the northern part of the Ponta Grossa Arch (Fartura city, SP) where dykes are exposed.A total component ground magnetic profile of 16 km in length was set up with an average spacing of 12.5 to 25 m between readings.There is clear correspondence between exposed dykes and short-wavelength magnetic anomalies.The ground magnetic data were transformed into aeromagnetic data by the upward continuation technique at different heights until it coincided with the altitude of one flight-line of the aeromagnetic survey flown at 450 meters above ground level (a.g.l.).This process reveals that most of dyke-generated magnetic anomalies are highly attenuated at altitude as low as 100 m a.g.L At 450 m, only anomalies associated with a group of closed spaced dykes or high-amplitude (above 4,000 nT on üíe ground) magnetic anomaly of a single dyke remain.These results were integrated with data of magnetization of dyke samples in order to establish a quantitative criteria of dykes detectability by conventional airborne magnetometry.For this particular region, it is found that most of the dykes can only be detected by ground magnetic survey due to low magnetization and small thickness of the dykes.Two additional ground magnetic profiles were set up in the interior of the Paraná basin, where dykes are not exposed and the results analysed.They indicate that the Ponta Grossa Arch dykes may extend northwesterly towards the center of the basin, cutting the thick pile of lava flows.This finding reinforces the geochemical and paleomagnetic evidence that the Ponta Grossa dyke swarms are associated with a late stage or a subsequent tectonomagmatic event following the main Serra Geral flood basalt volcanism in the southern and central Paraná basin.
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