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479 International Journal of Earth Sciences (2021) 110:467–485 13 0.1104 and 0.1191, being very close to the value defined for the UCC (0.12), while the metagreywackes from Tentudía Formation display larger variability in 147 Sm/ 144 Nd ratios, ranging from 0.1049 to 0.1296. Both groups of ratios remain within the typical range established by Zhao et al (1992) for clastic sediments (0.1–0.13), and far from the upper limit suitable for Nd model ages calculation (0.165; Stern 2002). f Sm/Nd values represent the deviation of the 147 Sm/ 144 Nd ratios from the present CHUR values (Table 3) . This fac- tor calculated for the samples of the Montemolín Forma- tion yields a very restricted value range (−0.39 to−0.44), reflecting a considerable isotopic homogenization. On the other hand, the metagreywackes from Tentudía Formation display a slightly wider range of values, varying from −0.34 to −0.47, which may suggest a lower influence of recycling processes. All of the metagreywacke samples from both formations display very negative ɛNd (0) values, ranging between −13.6 and − 17.1 for the Montemolín Formation; and between − 11.7 and − 18.1 for the Tentudía Formation. The ε Nd ( t ) follows a similar trend in both formations: metagreywackes from Montemolín Formation show an ε Nd (600) values rang- ing between −7.6 and −10.5, while in the metagreywackes from Tentudía Formation the ε Nd (565) ranges from −6.9 to − 11.5. For the entire Serie Negra Group, these negative values together with the low ranges of the f Sm/Nd values are consistent with a provenance from old and recycled sources mixed with juvenile components (McLennan and Hem- ming 1992). The fact that both formations have such similar ε Nd ( t ) values suggests that their sources probably remained constant throughout the sedimentation period that encom- passes both formations. The calculated T DM model ages for both formations of the Serie Negra Group plot within a restricted range of Paleoproterozoic ages (Fig. 6). The age vs. ε Nd diagram shows a clear overlap for both formations, with T DM values varying from 1747 to 1892 Ma for the Montemolín Forma- tion, and from 1686 to 1918 Ma in the Tentudía Formation. This figure also contains a synthesis of Nd model ages from the Serie Negra Group exposed in the Obejo-Valsequillo Domain (Rojo-Pérez et al. 2019), and from the Lower Alcu- dian section of the Central Iberian Zone (CIZ; Fuenlabrada et al. 2016), together with other Nd model ages from Central Europe (Linnemann and Romer 2002), are represented in Fig. for discussing paleogeographic affinities: old isotopic signatures from the West African Craton and the Amazonian Craton, conjoined with more juvenile ones such as those from West Avalonia in Atlantic Canada and Carolina. Comparison with Central European correlatives: Saxo-Thuringian Zone series. The affinity between Variscan sectors, which according to geotectonic and paleontological criteria share a com- mon pre-Paleozoic evolution, has been studied and debated before (Murphy et al. 2002; von Raumer and Stampfli 2008; von Raumer et al. 2015; Ballèvre et al. 2014; Mar- tínez Catalán et al. 2020). Nevertheless, geochemistry and especially isotopic approaches have not been extensively considered to correlate now distant, but potentially equiva- lent, metasedimentary sequences that made the Cadomian basement involved in the Variscan Orogen (Liew and Hof- mann 1988; Pereira et al. 2006). This kind of compari- son can help to understand Cadomian regions with low quality or lack of exposures and/or subjected to intense deformation and metamorphism. The new geochemical Sm–Nd isotopic data obtained herein for the Cadomian basement of the Ossa–Morena Complex, can be compared with equivalent coeval stratigraphic series described in the Cadomian basement of the Saxo-Thuringian Zone. Dif- ferent Nd isotopic data from the Ediacaran series of the Bohemian Massif have been published (Linnemann and Romer 2002; Linnemann et al. 2004). From these data, only samples that can be considered lithologically compa- rable to those from SW Iberia have been used to perform a Nd isotopic comparison. These samples are mainly Late Ediacaran metagreywackes and metapelites and consist of a group composed by 23 samples. These siliciclastic rocks belong to four different units of the Bohemian Cado- mian basement, which include the following successions: Frohnberg, Leipzig, Clanzschwitz and Rothstein forma- tions; Lausitz and Weesenstein groups. Lithological details Fig. 7 ε Nd ( T ) vs. CaO diagram for Late Ediacaran series of the Ossa- Morena Complex (SW Iberian Massif) and the Saxo-Thuringian Zone (Bohemian Massif), showing the influence of young mafic or felsic contribution, or less evolved components (after Linnemann and Romer 2002). The blue band shows the range where the majority of samples plot Iberian–Bohemian correlations