A geotraverse through the south and central sectors of the Ossa-Morena zone in Portugal (Iberian massif)

José Borrego, António Alexandre Araújo, and Paulo Fonseca

The Ossa Morena Zone (OMZ) corresponds to the southernmost tectonic and paleogeographic unit of the Autochthonous Iberian Terrane and is bounded towards the Southwest by the South Iberian Variscan Suture Zone. The structure of the South and Central sectors of this major unit is dominated by two earlier deformation evens, related with a synchronous process of obduction/subduction, during the closure of the Variscan Ocean. Detailed structural mapping along the Guadiana Valley (almost perpendicular to the variscan trending) shows clearly a polarity on the metamorphic grade and deformation, decreasing both from southwest to northeast. The main units crossed by this traverse includes an accrecionary prism and an ophiolitic sequence in the vicinity of the suture, a tectonic mélange above the southern part of OMZ (including tectonic slices of ophiolites and high pressure rocks) and autochthonous lower deformed palaeozoic sequences, towards the northeast. In this paper we discuss the meaning of the main metamorphic and structural features of all these units.