Nova Terra 52

471 International Journal of Earth Sciences (2021) 110:467–485 13 limb of the antiform (Fig. 2). Each sample was extracted from an individual layer of metagreywacke (dm-scale in thickness). The remaining twelve samples belong to the Ten- tudía Formation (TE-1 to TE-12). They are predominantly fine-grained metagreywackes collected from individual layers and in equivalent proportions in both limbs of the Olivenza–Monesterio antiform (Fig. 2). All rocks sampled are fresh, without evidence of significant alteration. The out- crops visited during sampling indicate that the metasedimen- tary rocks sampled in the Montemolín Formation seem to accumulate more deformation (strain) than those collected in the Tentudía Formation, although collectively, all of the samples show low-grade metamorphism and slight to mod- erate strain. Yet, sampling was targeted to the sections with lowest strain. In thin section, Montemolín samples show abundant micaceous minerals, including muscovite, biotite and chlo- rite, along with low deformed quartz-feldspathic levels. The samples exhibit heterogeneity in quartz and feldspar grain size, indicative of textural immaturity. This formation presents primary or tectonometamorphic compositional layering. On the other hand, in the Tentudía samples phyl- losilicates are even more abundant, as well as opaque min- erals and rock fragments. In general, these samples present a smaller grain size than Montemolín Formation and show higher plagioclase content in relation to K-feldspar. Whole-rock major and trace elements analysis Crushing and powdering of the rock samples were per- formed at the facilities of the Complutense University of Madrid. The analysis of major and trace elements were car- ried out in the Activation Laboratories (ActLabs), Ontario (Canada). Lithium metaborate/tetraborate was used for fusion of the samples, and the elements were measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The general precision was calculated at ~ 0.01%, and for MnO and Ti 2 O at ~ 0.001%. The elemental composition of the Ediacaran metagreywackes was analysed to constrain their provenance and isotopic sources. The results of the Fig. 3 Geological sketch of the Saxo-Thuringian Zone in the Bohe- mian Massif, including a schematic stratigraphic columns of the Edi- acaran–Lower Cambrian series. Stars represent the location of the metasedimentary series. Based on Linnemann and Schauer (1999), Linnemann and Romer (2002) and Linnemann (2007) Iberian–Bohemian correlations