Preliminary results of the Iberian Pyrite Belt 3D resistivity model through Magnetotelluric data.

The Iberian Pyrite Belt (IPB), which is located in the South Portuguese Zone (SPZ) of the Iberian Massif, is one of the most prominent sections of the Variscan orogenic belt in Western Europe. It extends over about 250 km in length and a width of 60 km forming an arc-shaped belt comprising several series of asymmetric basins that are tectonically controlled. These basins reflect the process of heterogeneous continental thinning triggered by left-lateral transpressive convergence with the Iberian Terrane.

Economically, it is an important European mining region with over 90 massive sulphides deposits shared between Portugal and Spain. It is home to world-famous and huge deposits such as Neves-Corvo, Aljustrel, Rio Tinto, Tharsis, Aznalcollar-Los Frailes, Las Cruces, among others. These mining activities show the economic dimension of the province based on the resources of Cu, Zn, Pb, Ag, Au, and Sn. The deposition of massive sulphides was related to the felsic volcanism and the black shales of the IPB volcano-sedimentary complex (VSC), which overlies the siliclastic sediments of the phyllite-quartzite group.

Nevertheless, many aspects are still poorly understood, especially those related to the deep lithospheric structure and the extent of the IPB to the southwest. The growing interest in the search for mineral deposits has led to many geophysical surveys being carried out over the years. However, most of them are limited to the first hundred meters in local areas or have a low spatial resolution, so a complete and global picture of the IPB extent isn't possible.

We present the preliminary results of a 3D resistivity model focusing on the lithospheric structure of the IPB down to a depth of 40 km. The model was calculated using data from 60 broadband Magnetotelluric (BBMT) stations, combining previous and newly acquired data, arranged in a 10x10 km grid along the IPB in Portuguese Terrain. The BBMT method provides a comprehensive resistivity image of the lithosphere, which is essential to decipher the geometry of the tectonic structures at depth. These structures play a key role in controlling the spatial distribution of many massive sulphide ore systems and offer potential insights into identifying new areas with deposits suitable for exploitation.

 

Acknowledgment

This work is supported by the Portuguese Fundação para a Ciência e Tecnologia, FCT, I.P./MCTES through national funds (PIDDAC): UID/50019/2025 and LA/P/0068/2020 https://doi.org/10.54499/LA/P/0068/2020).

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