La EGMA (Eastern Galicia Magnetic Anomaly) y las anomalías magnéticas en contextos extensionalesnuevos hallazgos

  1. M. Durán Oreja 1
  2. María Puy Ayarza Arribas 1
  3. Juan José Villalaín Santamaría 2
  4. José Ramón Martínez Catalán 1
  5. Fernando Carlos Álvarez Lobato 1
  6. Pablo Calvín Ballester 2
  1. 1 Universidad de Salamanca
    info

    Universidad de Salamanca

    Salamanca, España

    ROR https://ror.org/02f40zc51

  2. 2 Universidad de Burgos
    info

    Universidad de Burgos

    Burgos, España

    ROR https://ror.org/049da5t36

Journal:
Geotemas (Madrid)

ISSN: 1576-5172

Year of publication: 2021

Issue: 18

Pages: 712

Type: Article

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Abstract

The Eastern Galicia Magnetic Anomaly (EGMA), one of the most distinctive and best-studied magnetic anomalies of the Central Iberian Arc (CIA), overlaps onto the gneissic domes of Lugo and Sanabria, in northwest Spain. The Xistral tectonic window is placed in the northernmost part of the Lugo Dome. This is the place where the oldest and structurally deepest rocks in the area crop out. Also, extensional detachments resulting from late-Variscan extensional tectonics can be mapped in detail. Such a special geological context has allowed us to identify the rocks that are the source of this anomaly, which are also exposed there. High resolution mapping of the anomaly and analysis of the magnetic rocks have shown that magnetiza- tion is related to the late-Variscan extensional tectonics, and not to specific lithologies (Martínez Catalán et al., 2018). The first studies of natural remanent magnetization and anisotropy of the magnetic susceptibility in the source rocks carried out on magnetite and hematite-bearing samples, confirmed that magnetization occurred during the Kiaman reverse superchron, in the Upper Carboniferous-Lower Permian. These findings allow us to understand this and other anomalies that delineate the CIA and to re-interpret other magnetic features worldwide, which are also located in extensional contexts.

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