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granitic rocks plot in the middle between the old isotopic sources calculated for the metabasites of the Montemolín Fm, and the juve- nile isotopic sources represented by the Calzadilla Ophiolite (Lu-Hf isotope; Arenas et al., 2018) (Fig. 12a), likely as a result of mixing of both. The correlation shown by the high contents of e Nd (t) versus low values of 87 Sr/ 86 Sr (t) of the samples belonging to the Don Álvaro and Valle Real sets is traditionally related with a dominance of the magmatic processes in the chemical evolution of rocks (White, 2015). While the more heterogeneous values of 87 Sr/ 86 Sr (t) (non-radiogenic to radiogenic) together with a trend towards more negative values of e Nd (t) in the rocks belonging to the San Andrés and Valverde complexes, do not represent so clearly this anti- correlation, appearing even close to reservoirs of a crustal nature (eg DePaolo and Wasserburg, 1976; White, 2015). The metaig- neous complexes in the studied arc section follow an isotopic pat- tern quite similar to that of Andean batholiths studied by Castro et al., 2011, 2021 (Fig. 12b). The isotopic tracks show in this figure are also correlated with the isotopic sources involved in the Serie Negra Group generation. In the diagram 87Sr/ 86 Sr vs. 143 Nd/ 144 Nd (Supplementary Fig. S3b) all the metaigneous complexes are depicted in the field of trench sediment compositions studied by Plank (2014). Whereas the Montemolin metamafic rocks seem to be more affected by Sr mobility and are plotted slightly apart from this field. Comparing the variation of Ce/Yb ratios (Supplementary Table 2) of each group of samples separately, with their e Nd (t) val- ues (Supplementary Table 4), we observe two different trends. Lowest Ce/Yb values occur in the metabasites of the Montemolín Formation, which are correlated with the narrow range in the e Nd (t) , following a trend shown by the magmatism in relatively primitive systems (Hawkesworth et al., 1994). A normal distribu- tion pattern is also followed by the samples belonging to the Don Álvaro and Valle Real metaigneous complexes from high e Nd (t) (2.8) and low Ce/Yb ratio (11.73) toward low e Nd (t) (0.5) and high Ce/Yb (22.59) (Supplementary Tables S2 and S4). While San Andrés and Valverde exhibit a trend towards an inverse correlation leads by high Ce/Yb values against the e Nd (t) values (Supplementary Tables S2 and S4), related traditionally with contribution of LREE enriched material (Hawkesworth et al., 1994). 6. Discussion 6.1. Age constraints The analyzed samples show a wide range of U-Pb ages virtually uninterrupted from ca. 620 Ma to ca. 535 Ma. Inherited ages older than 700 Ma were not found in four out of the five analyzed sam- ples. The oldest inherited ages are represented by one analysis of 727 Ma and another of Paleoproterozoic age (1632 Ma), highlight- ing the lack of Mesoproterozoic ages typical of a West-African provenance. Statistical analysis of the zircon populations reveals the recurrent appearance of certain age groups recorded in the five samples analyzed. The concordia ages obtained for these data sets can be related to magmatic events that occurred within the pre- served section of the peri -Gondwana active margin in SW Iberia during the Neoproterozoic - Early Cambrian arc cycle. This evolu- tion suggests at least three periods of greater magmatic activity from the beginning of the most representative clusters at c. 600 Ma and up to ca. 550–540 Ma. The shortage of older inherited ages, attributable to the presence of older continental crust, as well as the morphology and the internal features of the zircons ana- lyzed, may suggest a recycling and reworking of the older igneous rocks in this section of the magmatic arc. The sedimentation age for the (lower and oldest) Montemolín Formation had been classi- cally established at c. 590 Ma, based essentially on ages obtained from the mafic rocks that occur within it (Ordóñez-Casado, 1998, Sánchez-Lorda et al., 2016). However, the geochronological data obtained in this work for the intrusive metaigneous complexes in this series may provide new insights with regards to the onset of sedimentation in this arc section. The oldest concordant analysis corresponds to a sub-rounded zircon grain (SAMIC felsic gneiss in Fig. 7), dated at 1632 Ma. This age is compatible with a possible participation, at least in part, of metasedimentary rocks from WAC as indicated by previous works (e.g. Linnemann et al., 2004, 2014; Pereira et al., 2011). It is well established that this margin was active from c. 750 Ma (Albert et al., 2015; Andonaegui et al., 2016; Abati et al., 2010), however the studied rock assemblages have a single analysis of 727 Ma ascribable to that age. The oldest population clusters analysed here reveal signs of magmatic activity at least between 645 and 625 Ma in the North African margin close to the WAC. These older inher- ited ages appear only in the San Andrés metaigneous complex (SAMIC felsic gneiss), whose crystallization age has been estab- lished at c.602 ± 3 Ma. This new age places a new constraint on the (pre-) Cadomian granitic magmatism preserved in the southern branch of the European Variscan Orogen. These new radiometric dating constraints the minimum deposition age to the bottom of Serie Negra Group at pre- 602 Ma. These data also imply that the beginning of the mafic magmatism preserved in this section (metabasites of the Montemolín Formation) must have been previ- ous or at least synchronous with the intrusion of the first meta- granitoid complex at c. 602 Ma. All samples show a more or less volumetric population of zircon ages between c. 580–570 Ma. Although this age has been suggested by several authors (e.g. Bandrés et al., 2004; Talavera et al., 2008) to represent the main magmatic event, in the studied arc section there is no direct evi- dence that indicates granitic intrusion at this age. Between c. 560–550 Ma, all the samples record another pulse of activity in the arc. This age is well known in SW Iberian and is considered to represent an age of metamorphism and compressive deforma- tion in the pre-Paleozoic rocks of the region (Arenas et al., 2018; Díez Fernández et al., 2021; and references therein). In the studied arc section, a well-constrained magmatic pulse has the same age and is recorded by the intrusion of Valverde Metaigneous Complex at 551 ± 4 Ma (VALMIC metagranite) and 554 ± 2 Ma (VALMIC1 metagranite). Following the magmatic evolution of this arc section, between 550 and 540 Ma some samples seem to register a new pulse of magmatic activity that gives rise to the generation of tonalitic-granodioritic magmas, such as the one represented by the metaigneous complexes of Don Álvaro (DAMIC metatonalite) and Valle Real (VRMIC metagranodiorite), whose crystallization age has been established at 541 ± 3 and 541 ± 5 Ma, respectively. The ages obtained from the youngest analysis are not easily attri- butable to a specific event because they are isolated analyses (c. 520 and 500 Ma). However, previous studies carried out at the OMC have related the final stages of this arc evolution to a volcanic episode established around c. 525–515 Ma (Ordóñez-Casado, 1998). 6.2. Magma generation The genesis of the investigated subduction-related melts was likely complex, mainly conditioned by the long-lasting nature of the recycling processes evidenced by geochronological data along with their geochemical and isotopic features. The thickness of known preserved metasedimentary host sequence (Serie Negra Group) currently does not exceed 3000–4000 m, but this value was surely higher. This opens the door for unexposed/unpreserved sequences in Iberia to occupy a lower structural position within the arc edifice and the possibility that those sequences with conti- nental crust affinity were located over fore-arc domains during E. Rojo-Pérez, U. Linnemann, M. Hofmann et al. Gondwana Research 109 (2022) 89–112 The Ediacaran arc section