Potential field signature of a late-Variscan extended realm. Implications for western Iberia Sn-W mineralization
- 1Geology Department, Universidad de Salamanca, Spain (puy@usal.es)
- 2Facultad de Físicas, Universidad Complutense de Madrid, Spain
- 3Instituto Geológico y Minero de España (CN IGME-CSIC), Zaragoza, Spain
The internal part of the Central Iberian Arc (CIA) features a number of long-wavelength, high amplitude aeromagnetic anomalies that overlap gneiss domes developed during late Variscan extension. Some of the largest anomalies are located at the core of the CIA and coincide with the western Iberia Sn-W belt, e.g., the Porto-Veira-Guarda Magnetic Anomaly (PVGMA) and the Central System Magnetic Anomaly (CSMA). Despite both of them lying on top of the products of crustal extension and melting (granites and migmatites), outcropping rocks do not feature high magnetic susceptibilities, raising the question about the origin of the anomalies.
In the last two years, ground high-resolution magnetic and gravity surveying has been carried out in the northern part of the CSMA, in the boundary between igneous rocks and their metamorphic host rocks. The latter are part of thermal domes developed in the latest stages of Variscan extension. Results show that magnetic highs coincide with gravity highs, thus indicating that the source of the anomalies is probably basic rocks. Indeed, scarce outcropping gabbros have magnetite, and feature a moderate magnetic susceptibility, but a very high magnetic remanence (Qn<400) of reverse polarity and directions that match those of the Kiaman superchrone, compatible with the age of gabbros (305-294 Ma). Furthermore, the characteristics of the magnetic anomalies, featuring long wavelengths, indicate that magnetic rocks (gabbros) abound at depth.
The sole existence of gabbros, albeit scarce, in the study area indicates that the mantle was involved in late Variscan extension in this part of the CIA. Crustal thickening associated to the development of the CIA must have produced lithospheric instabilities that eased the entrance of mantle melts, including metals like Sn and W, nowadays highly demanded.
Acknowledgements: Projects SA084P20, TED2021-130440B-100 and PID 2020-117332GB, MS (UCM, CT18/22)
How to cite: Ayarza, P., Rivero Montero, M., Gómez Barreiro, J., Martínez Catalán, J. R., Calvín, P., Sánchez Sánches, Y., and Palomeras, I.: Potential field signature of a late-Variscan extended realm. Implications for western Iberia Sn-W mineralization, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7682, https://doi.org/10.5194/egusphere-egu24-7682, 2024.
