RT Journal Article
T1 Magnetization related to late-Variscan extensional collapse in the Lugo Dome (NW Iberian Massif): a metamorphic petrology approach
A1 Durán Oreja, Manuela
A1 Pitra, Pavel
A1 López Carmona, Alicia
A1 Martínez Catalán, José Ramón
A1 Ayarza Arribas, Puy
AB The Eastern Galicia Magnetic Anomaly (EGMA) is one of the most distinctive and best studied magnetic anomalies in Iberia. It is located in NW Spain and overlaps the Variscan gneissic domes of Lugo and Sanabria. The Lugo Dome, in the north of the EGMA, deforms a large thrust sheet, the Mondoñedo Nappe, allowing the outcropping of its relative autochthon in the Xistral Tectonic Window, where extensional detachments resulting from late-Variscan tectonics crop out. A younger major detachment, the Viveiro Fault, developed on the western limb of the dome. Detailed ground-based magnetic mapping and geological charts show a clear spatial relationship between magnetic maxima and the extensional structures. Magnetic and paleomagnetic studies carried out on samples from this region indicate that rocks in the detachments commonly bear magnetite and hematite carrying induced but also remanent magnetizations and a very well-defined anisotropy of the magnetic susceptibility with directions matching those of the late-Variscan extensional fabrics.Three pairs of metasedimentary samples in equivalent structural positions display variously developed medium-pressure Barrovian parageneses attributed to the early compressional phases of the Variscan orogeny, and low-pressure Buchan-type parageneses associated with the late Variscan extension. Our phase diagram-based petrological study suggests that the non-magnetic samples preserve the Barrovian conditions of 560–640 °C, 5–8.7 kbar. The lithologically and structurally equivalent samples, originally non-magnetic, developed magnetite/hematite-bearing mineral assemblages during decompression and cooling to 500–620 °C, 1.5–6 kbar. This recrystallization was probably assisted by metasomatic oxidizing fluids. The induced component of magnetization is essentially carried by magnetite, while hematite seems the main carrier of remanence. These results support the existing cartographic, geophysical and paleomagnetic findings indicating that the magnetization in the Lugo Dome is related to late-Variscan extension.
PB Elsevier
SN 0024-4937
YR 2024
FD 2024-11-01
LK https://hdl.handle.net/20.500.14352/107922
UL https://hdl.handle.net/20.500.14352/107922
LA eng
NO Durán Oreja, Manuela, et al. «Magnetization Related to Late-Variscan Extensional Collapse in the Lugo Dome (NW Iberian Massif): A Metamorphic Petrology Approach». Lithos, vol. 484-485, noviembre de 2024, p. 107745, https://doi.org/10.1016/j.lithos.2024.107745
NO Ministerio de Economía y Competitividad
NO Ministerio de Ciencia e Innovación
NO Gobierno de Castilla y León
NO Agencia Estatal de Investigación
DS Docta Complutense
RD 6 abr 2025