Late- to post-Variscan tectonics and the kinematic relationship with W-Sn vein-type mineralization: evidence from Late Carboniferous intramontane basins (Porto-Satao syncline, Variscan Iberian belt)

Many studies have constrained that late-Variscan buckling produced the arcuate geometry of the Ibero-Armorican belt. Nonetheless, debate remains on the associated geodynamic framework. Poorly studied Late Carboniferous intramontane basins offer an excellent framework to decipher the timing and kinematics of the late- to post-Variscan tectonics. Understanding the latter also helps constrain the structural emplacement mode of contemporaneous W-Sn-Nb-Ta-Li mineralization. In Iberia, the Porto-Satao syncline is an example of such a Late Carboniferous intramontane basin. We present a structural analysis of the syncline, its basement and the associated W-Sn deposits. The regional structure is dictated by the Alcudian angular unconformity, caused by Cadomian tectonics (575-555 Ma) and separating tilted Ediacaran and subhorizontal Lower Paleozoic formations. Superimposed Variscan deformation led to F-1-F-3 folds with steep and gentle plunges, respectively. The late-orogenic D-3 fabric is locally affected by post-orogenic F-4 kink folds and an S-4 crenulation cleavage. W-Sn-bearing vein systems occur along granite-hosted cone sheets, or exploit cross-fold joints associated with the F-3 and F-4 fold generations, revealing a close kinematic relationship between granite-related mineralization and the late- to post-Variscan deformation style. This structural history is interpreted as a plate-scale geodynamic change from Late Carboniferous north-south (D-3) to Early Permian WNW-ESE (D-4) convergence.

Automated summary

Many studies suggest that late-Variscan buckling contributed to the arcuate geometry of the Ibero-Armorican belt, with poorly studied Late Carboniferous intramontane basins providing valuable insight into the late- to post-Variscan tectonics. Understanding this helps constrain the emplacement mode of contemporaneous mineralization, such as W-Sn-Nb-Ta-Li deposits.