Análise preliminar dos dados magnéticos do Saco de Mamanguá e da Enseada de Paraty-Mirim, Rio de Janeiro

Melo, Janaina dos Santos; Marangoni, Yára Regina; Jovane, Luigi

doi:10.22564/16cisbgf2019.048

Cited by 2 publications

(3 citation statements)

References 4 publications

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“…The BASEMAG was a GSM-19 Overhauser magnetometer with a resolution of 0.01 nT and ± 0.1 nT of accuracy (Melo 2019), with sampling data every 3 min. On the Ubatuba survey (Survey 3 in Fig.…”

Section: Magnetometric Data and Survey Areasmentioning

confidence: 99%

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Diurnal variation effect in marine magnetometric surveys: clues from surveys in southeast Brazil

et al. 2021

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The diurnal variation of the magnetic field cannot be predicted or modeled and for that reason, it is monitored during the magnetic surveys, usually by a stationary magnetometer. However, marine surveys have a practical issue with diurnal monitoring, owing to the distance between the survey, stationary magnetometers, and magnetic observatories. This work aims to verify the use of nearby magnetic observatories to estimate the diurnal variation correction in different marine surveys and evaluate its effectiveness. In this study, we selected surveys at the continental shelf near Santos city (Survey 1), continental slope next to the first survey location (Survey 2), continental shelf near Ubatuba city (Survey 3), and Mamanguá ria in the Paraty city (Survey 4), all southeast to the Brazilian coast. The crossing points were implemented to compare the magnetic field values at different times and days at the same measurement point, before and after the correction. Afterwards, we measure the Pearson’s Correlation of the raw data and the diurnal corrected data in all crossing points of each survey which showed an improvement after correction by the value approximating to 1, which indicates a very well correlation. The Ubatuba and Mamanguá surveys allowed comparing the observatory correction results with the base magnetometer results that were rather similar. Our analyses indicate a satisfactory diurnal correction using the observatory data and the crossing points approach, which can be used for every marine magnetometric survey worldwide placed near the coast (< 280 km) that do not have a stationary magnetometer available.

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Section: Magnetometric Data and Survey Areasmentioning

confidence: 99%

“…It is too expensive for the ship to redo the magnetometric acquired line. Leaving a base magnetometer in the middle of the ocean is also not practical and the base station is only used when the survey area is close to the coast and it is possible to leave the base in a safe location avoiding noise and disturbances (Melo et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Diurnal variation effect in marine magnetometric surveys: clues from surveys in southeast Brazil

et al. 2021

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“…This study uses marine and aeromagnetic data (Melo et al, 2019). Marine magnetic data were collected by the boat of the Oceanographic Institute, University of São Paulo, on October 6th and 7th, 2017.…”

Section: Databasementioning

confidence: 99%

Magnetic Signature of the Saco do Mamanguá and Paraty-Mirim Cove, Rio de Janeiro, Brazil

Melo¹,

Marangoni²

2021

Braz J Geophys

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ABSTRACT. In this work, we investigate the N40°-50°E-oriented magnetic lineaments observed in the marine and aeromagnetic data from the Paraty-Mirim and Saco do Mamanguá (RJ) coves. The main characteristic of these lineaments is the presence of normal and reverse magnetic polarity, indicating that the bodies responsible for the anomalies may be of different ages or have suffered remagnetization effects by metamorphism or have distinct lithologies. The interpretative model of the anomalies was obtained by the 3D Magnetization Vector Inversion (MVI) and by the study of the geology and tectonics of the area. Our results suggest, as a more likely hypothesis, that the magnetic lineaments can be correlated with two tholeiitic dykes swarms, Resende-Ilha Grande and Serra do Mar, which have intruded the region at different times. The age formation of those swarms can be placed at time intervals where the Earth's magnetic field has normal and reverse polarities. The contrasts of magnetic susceptibility obtained from the models are consistent with contrasts of the lithology of basic dykes intruded in the gneissic-granitic basement of the region. Keywords: magnetization vector inversion, magnetic properties, magnetic lineaments, remanent magnetization, tholeiitic dykes swarms Assinatura Magnética do Saco do Mamanguá e da Enseada de Paraty-Mirim, Rio de Janeiro, BrasilRESUMO. Neste trabalho, investigamos os lineamentos magnéticos orientados a N40°-50°E observados nos dados marinhos e aeromagnéticos das enseadas de Paraty-Mirim e do Saco do Mamanguá (RJ). A principal característica destes lineamentos é a presença de polaridade magnética normal e reversa, indicando que os corpos responsáveis pelas anomalias podem ter idades diferentes ou terem sofrido efeitos de remagnetização por metamorfismo ou apresentarem litologias distintas. O modelo interpretativo das anomalias foi obtido pela Inversão do Vetor de Magnetização (IVM) 3D e pelo estudo da geologia e tectônica da área. Nossos resultados sugerem, como hipótese mais provável, que os lineamentos magnéticos podem ser correlacionados com dois enxames de diques toleíticos, Resende-Ilha Grande e Serra do Mar, que têm idades diferentes de intrusão. As idades de formação desses enxames podem ser colocadas em intervalos de tempo em que o campo magnético da Terra apresentou polaridades normal e reversa. Os contrastes de susceptibilidade magnética obtidos no modelo são coerentes com os contrastes de litologia de diques básicos intrudidos no embasamento granítico-gnáissico da região.Palavras-chave: inversão do vetor de magnetização, propriedades magnéticas, lineamentos magnéticos, magnetização remanente, enxames de diques toleíticos

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Análise preliminar dos dados magnéticos do Saco de Mamanguá e da Enseada de Paraty-Mirim, Rio de Janeiro

Cited by 2 publications

References 4 publications

Diurnal variation effect in marine magnetometric surveys: clues from surveys in southeast Brazil

Diurnal variation effect in marine magnetometric surveys: clues from surveys in southeast Brazil

Magnetic Signature of the Saco do Mamanguá and Paraty-Mirim Cove, Rio de Janeiro, Brazil

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