This study combines structural mapping, petrographic analysis, and U-Pb zircon geochronology of low-grade metamorphic rocks from the Iberian Pyrite Belt (IPB), located in the westernmost domains of the South Portuguese Zone (SPZ). At Ilha do Pessegueiro beach, the Cercal volcanic-sedimentary complex (VSC) rocks, assigned to the Late Devonian in previous studies, exhibit a dominant S 1 slaty cleavage overprinted by S 2 crenulation cleavage. This ductile deformation has been attributed to contractional tectonics. However, new structural data indicate that older ductile structures formed in relation to a low-grade extensional shear zone (D 1 -E) and were tectonically transported to the east-southeast. The new age of the Cercal VSC felsic metatuffs (ca. 364-363 Ma) is consistent with VSC ages from other areas of the IPB, enabling us to bracket the D 1 -E deformation event between the Tournaisian and the Bashkirian. After the D 1 syn-convergent extension, a subsequent contractional deformation event (D 2 -C), resulting from the latest events of the Gondwana-Laurussia oblique convergence, caused inversion of the Carboniferous synorogenic basins and the formation of a thrust-and-fold belt. Recent data for the late Devonian-early Carboniferous geology of the IPB appear to support a correlation between the SPZ and the Meguma terrane.
Pereira et al. (Mon,) studied this question.
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