Application of magnetic method on the Argentine continental shelf between 35ºS and 48ºS

• Arecco, María A. ^[2] ; Larocca, Patricia A. ^[2] ; Ruiz, Francisco ^[3] ; Canero, Armando T. ^[1] ; Ramos, Víctor A. ^[4]
  1. [1] Universidad de Buenos Aires

     Universidad de Buenos Aires

     Argentina

     
  2. [2] Instituto de Geodesia y Geofísica Aplicadas, Argentina
  3. [3] Instituto Geofísico Sismológico Volponi, Argentina
  4. [4] Instituto de Estudios Andinos, Argentina

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• Localización: Geofísica internacional, ISSN 0016-7169, ISSN-e 2954-436X, Vol. 57, Nº. 3, 2018, págs. 175-195
• Idioma: inglés
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• Resumen
  • español

    Se analizaron las anomalías del Campo Magnético Total a partir de datos de una red global, con el propósito de contribuir al conocimiento y caracterización de la plataforma continental argentina (35ºS hasta 48ºS). Para ello se utilizaron técnicas de realce, como la señal analítica, el ángulo tilt, y la segunda derivada vertical. Se calcularon las profundidades de las fuentes magnéticas a partir del método de deconvolución de Euler y el modelado de inversión gravimétrica 2D. A partir de los resultados filtrados del TMA se identificaron grandes zonas de fractura de transferencia.

    La segunda derivada vertical mostró patrones de alta frecuencia en las anomalías G y Tona, así como también en la serie de anomalías M y alineamientos de fondo oceánico, mostrando el carácter volcánico y episódico de los mismos.

    El método de deconvolución de Euler permitió localizar fuentes magnéticas discontinuas a lo largo del antiguo cinturón Dom Feliciano- Lavalleja, cuyas profundidades van desde 5000 a 8000 m. Se obtuvieron pocas soluciones tipo diques, escalones de falla en las zonas de fallas de transferencia y el borde entre corteza continental y oceánica. Se localizaron fuentes en la serie-M a profundidades entre 8000 y 12000 m. También, este método permitió calcular las profundidades de la conspicua anomalía Tona entre 8000 y 20000 m. Además, a partir de un modelo de inversión gravimétrico 2-D aplicado sobre un perfil con dirección NE, se identificó un cuerpo máfico-ultramáfico a lo largo de la sutura Patagonia-Gondwana hasta casi la superficie.

    Este cuerpo podría ser una imbricación de la sutura emplazada en rocas del basamento.

  • English

    The total magnetic anomaly (TMA) from a global grid was analysed in order to characterize the magnetic features of the Argentine continental shelf (35ºS to 48ºS) and to expand the current knowledge of such area. TMA amplitudes within the study area were mathematically filtered and enhanced using various techniques including the analytic signal method, the tilt angle method and the second vertical derivative method. In order to estimate the depths of the magnetic sources on the Tona anomaly and the continental edge, the Euler deconvolution method and a 2-D gravimetric inversion model were applied. The TMA filtering results were used to observe and identify large transform zones such as the Río de la Plata system, the Salado, Ventana, Colorado and Malvinas zones, and other minor systems such as the Rawson transform zones. The San José and El Cortijo crustal sutures were also outlined using the applied methods, and it was possible to map and identify a change in orientation of the Ventania-Cape Fold Belt. The tilt angle method revealed high-frequency patterns in the oceanic crust as a result of its volcanic nature. The second vertical derivative method exhibited high-frequency patterns in the G and Tona anomalies, the M-series magnetic anomalies and oceanic bottom alignments, revealing their volcanic and episodic character through a large and complex distribution of blocks at the continental-oceanic boundary. Discontinuous linear magnetic sources were observed along the ancient Dom Feliciano-Lavalleja shear belt, most of which were calculated by Euler deconvolution to be located at depths of approximately 5000–8000 m. On transform zones, inner alignments and continental- oceanic boundaries, few dipoles associated with fault steps and dykes were identified.

    The sources of the M-series anomalies were located at depths of 8000–12000 m, whereas abundant deeper sources were identified for the Deseado and Somuncurá massifs and the Mar Argentino rise. The Euler deconvolution method was used to calculate a source depth range for the conspicuous Tona anomaly of 8000–20000 m. In addition, a 2-D gravimetric inversion model based on a NE-trending profile was used to identify a mafic body along the Patagonia-Gondwana suture bounded by a sub-surface. This body may be an imbrication of the suture located in basement rocks.