Nova Terra 52

Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres Contrasting isotopic sources (Sm-Nd) of Late Ediacaran series in the Iberian Massif: Implications for the Central Iberian-Ossa Morena boundary Esther Rojo-Pérez a, ⁎ , Ricardo Arenas a , José M. Fuenlabrada b , Sonia Sánchez Martínez a , Luis Miguel Martín Parra c , Jerónimo Matas c , Agustín P. Pieren d , Rubén Díez Fernández d a Departamento de Mineralogía y Petrología e Instituto de Geociencias (UCM, CSIC), Universidad Complutense, 28040 Madrid, Spain b Unidad de Geocronología, Universidad Complutense, 28040 Madrid, Spain c Instituto Geológico y Minero de España, 28760 Tres Cantos, Madrid, Spain d Departamento de Geodinámica, Estratigrafía y Paleontología, Universidad Complutense, 28040 Madrid, Spain A R T I C L E I N F O Keywords: Ediacaran siliciclastic rocks Sm-Nd isotopic sources Central Iberia-Ossa Morena boundary Iberian Massif Variscan Orogen A B S T R A C T In the Iberian Massif, westernmost sector of the Variscan Orogen, the nature of the boundary between the Central Iberian Zone and the Ossa Morena Complex has been largely discussed. Peri-Gondwanan Ediacaran series similar in age ( c. 565 Ma) but different in composition occur at both sides of that boundary. The Lower Alcudian Series (Central Iberian Zone) is located to the north, while the Serie Negra (Ossa-Morena Complex) can be found to the south of the boundary. Major and trace element compositions and Sm-Nd isotopic systematics of siliciclastic rocks from both series suggest a common active margin setting for their deposition, the Serie Negra likely occupying a more external (fore-arc) position within the arc-system relative to the Lower Alcudian Series, which would have been deposited within a large back-arc domain. TDM ages for these two series are notably different, yielding values of 1421–2040 Ma and 1256–1334 Ma for the Serie Negra and Lower Alcudian, re- spectively. These values suggest higher input from old cratonic sources in the Ossa Morena Complex, with probable participation of the West African Craton, which would be less prominent in the Central Iberia Zone. The whole data set indicate deposition of the Ediacaran series in separated basins, probably far away from each other along/across the margin of Gondwana. Current juxtaposition of these basins is explained by Variscan and probably also pre-Variscan tectonics. Similar conclusions could be also be extended to other similar boundaries in the Variscan Orogen. 1. Introduction The Variscan Orogen resulted from the collision between Gondwana and Laurussia, during the main stages of the Pangea assembly in Devonian-Carboniferous times (Matte, 2001; Martínez Catalán, 2011; Arenas et al., 2014; Díez Fernández et al., 2016). The Iberian Massif represents the southwestern European branch of this orogen and con- tains the suture of the collision and an excellent record of the strati- graphic series deposited during the Ediacaran and Paleozoic in the continental margin of Gondwana (Fig. 1). These series are distributed through diverse geotectonic zones (Fig. 1), each of which characterized by a stratigraphic and tectonic record indicative of basins developed at different paleogeographic positions along the continental paleomargin. The juxtaposition of formerly distant paleogeographic domains of Gondwana is, in part, a consequence of the Variscan convergence, and it is being actively investigated by means of provenance analysis of sedimentary series in order to reconstruct the original position of pa- leobasins in the Gondwana margin (Díez Fernández et al., 2010; Fernández-Suárez et al., 2014; Albert et al., 2015a). In the SW of the Iberian Massif, the nature of the boundary between the autochthonous (Central Iberian Zone) and the allochthonous do- mains (Ossa-Morena Complex) (Figs. 1 and 2) is subject to discussion. From a paleogeographic point of view, sections of the margin of Gondwana that show equivalent sedimentary record to the Central Iberian Zone or to the Ossa-Morena Complex are distributed along the Variscan orogen (Fig. 1). Therefore, advances in the understanding of https://doi.org/10.1016/j.precamres.2019.01.021 Received 30 July 2018; Received in revised form 3 January 2019; Accepted 29 January 2019 ⁎ Corresponding author at: Departamento de Mineralogía y Petrología e Instituto de Geociencias (UCM, CSIC), Facultad de Geología, Universidad Complutense de Madrid, C/José Antonio Novais, no 2, 28040 Madrid, Spain. E-mail addresses: e.rojo@ucm.es (E. Rojo-Pérez), rarenas@ucm.es (R. Arenas), jmfuenla@ucm.es (J.M. Fuenlabrada), s.sanchez@geo.ucm.es (S. Sánchez Martínez), lm.martin@igme.es (L.M. Martín Parra), j.matas@telefonica.net (J. Matas), apieren@ucm.es (A.P. Pieren), rudiez@ucm.es (R. Díez Fernández). 3UHFDPEULDQ 5HVHDUFK ² $YDLODEOH RQOLQH )HEUXDU\ ‹ (OVHYLHU % 9 $OO ULJKWV UHVHUYHG