Contrasting chemical and isotopic signatures from Neoproterozoic metasedimentary rocks in the Central Iberian Zone (Spain) of pre-Variscan Europe: Implications for terrane analysis and Early Ordovician magmatic belts

Abstract

Neoproterozoic metasedimentary units from central Spain and the northern Central Iberian Zone (CIZ) show distinctive geochemical signatures with respect to the Schist-Greywacke Complex, which is dominant in the southwestern part of the CIZ. Significant differences occur in major and trace element composition and initial Nd isotope ratios, which cannot be explained in terms of metamorphic grade and/or anatexis in some layers of these metasedimentary sequences. ɛNd540 values from metapelites of central Spain range from −5.6 to −10.4 whereas those from the Schist-Greywacke Complex span a narrower and higher range of −0.8 to −3.1. This difference suggests different source regions. The presence of two contrasting Early Ordovician magmatic belts in both subzones reinforces the idea of different Precambrian basement terranes in the CIZ. These data are crucial for pre-Variscan paleogeographic reconstructions of the westernmost European terranes and for checking the validity of current subdivisions of the Iberian Massif.