serie NOVA TERRA nº 49

110 and Cambrian sequences. Some studies considered a more stable and recycled deposition environment (passive margin model), with a signif- icant homogeneity as one of the most important features shared among the complete sequence ( Ugidos et al., 1997a, 1997b, 2003a; Valladares et al., 1998, 2000 ), suggesting that the West Africa Craton was the most likely source for the Late Precambrian rocks ( Ugidos et al., 2003b ). Geochemical and Sm – Nd data, along with U – Pb detrital zircon populations have allowed other authors to interpret the juvenile contri- bution to be linked to the waning activity of a long-lived peri- Gondwanan magmatic arc (Cadomian cycle) for the Ediacaran metasedimentary rocks of the CIZ and related peri-Gondwanan do- mains ( Pastor-Galán et al., 2013; Fernández-Suárez et al., 2000, 2014; Gutiérrez-Alonso et al., 2003; Nägler et al., 1995; Orejana et al., 2015; Rodríguez Alonso et al., 2004b; Talavera et al., 2012; Villaseca et al., 2014 ), proposing a wide range of potential locations for these series along the northern margin of Gondwana during the Late Ediacaran and Early Paleozoic, and therefore different sources for the mantle- derived contributions. In recent years, attempts have been made to ex- plain the evolution of the late stages of the Cadomian orogeny and the accumulation of thick siliciclastic sedimentary successions during the Precambrian – Cambrian transition ( Rodríguez Alonso et al., 2004a ). Some models propose a passive margin for its deposition ( Valladares et al., 2000, 2002 ), whereas others favor the existence of asymmetric ba- sins formed in a tectonically active setting ( Rodríguez Alonso et al., 2004b; Villaseca et al., 2014 ). The latter models frame such tectonic ac- tivity within the evolution from a compressive (Cadomian orogeny) to an extensional regime along the northern margin of Gondwana ( Nance et al., 2010 ). In the present work, geochemical and Sm – Nd isotopic studies of rep- resentative fi ne-grained sedimentary rocks from the southern Central Iberian Zone have been carried out to discover the sedimentation environment of Late Neoproterozoic and Early Cambrian metasedimentary sequences. Slight differences in the compositions of relatively immobile trace elements as well as signi fi cant changes in Nd model ages suggest important differences in the contribution of juvenile or cratonic sources during Late Ediacaran – Early Cambrian times. These differences are used to explore the tectonic setting during this transition and further the knowledge of the geochemistry and sources of the sed- imentary series of the peri-Gondwanan realm. 2. Geological setting Stratigraphic, structural, magmatic and metamorphic criteria were used to de fi ne the geotectonic zones within the Iberian Massif section of the Variscan Belt ( Arenas et al., 1988; Farias et al., 1987; Julivert et al., 1974; Lotze, 1945; Quesada, 1991 ) ( Fig. 1 ). One of them is the Central Iberian Zone, an autochthonous section of the Iberian Massif that is bounded to the east and northeast by more external domains of the orogen, the West Asturian – Leonese Zone and the Cantabrian Zone ( Fig. 1 ). The CIZ is thrust by the most internal domain of the orogen, which is represented by allochthonous complexes with high-P metamorphic belts and ophiolites featuring a Variscan suture ( Fig. 1 ; Martínez Catalán et al., 2009 ). The domain located to the south of the CIZ, the Ossa – Morena Zone, has been recently identi fi ed as another allochthonous complex of the Iberian Massif, and is correlated with equivalent complexes of NW Iberia ( Díez Fernández and Arenas, 2015 ). The CIZ can be divided in two domains: the Ollo de Sapo Domain and the Schist – Greywacke Complex Domain. The Ollo de Sapo Domain, to the North, shows as an essential feature the presence of thickmassifs of augen gneisses, abundant Variscan granitoids, and a high-grade regional meta- morphism affecting thick Paleozoic series and minor Ediacaran rocks ( Díez Montes et al., 2004 ). The domain to the South, received the name Fig. 1. Terranes and oroclines of the Variscan belt ( Martínez Catalán, 2011 ). Arcs: BA, Bohemian; CIA, Central Iberian; IAA, Ibero-Armorican; MCA, Massif Central. Zones of the Iberian Massif: CIZ, Central Iberian; CZ, Cantabrian; GTMZ, Galicia – Trás-os-Montes; OMZ, Ossa – Morena; SPZ, South Portuguese; WALZ, West Asturian – Leonese. Shear zones and faults: BCSZ, Badajoz – Córdoba; JPSZ, Juzbado – Penalva; LPSZ, Los Pedroches; NPF, North Pyrenean; PTSZ, Porto – Tomar; SISZ, Southern Iberian. Location of the geological map and section presented in Fig. 2 is shown. 16 J.M. Fuenlabrada et al. / Tectonophysics 681 (2016) 15 – 30