Geochemical and isotopic (Nd) correlation between SW Iberian and N Bohemian Late Ediacaran siliciclastic series

18 Geochemical and isotopic (Nd) correlation between SW Iberian and N Bohemian Late Ediacaran siliciclastic series Esther RojoǦPérez1, J. M. Fuenlabrada2, U. Linnemann3, R. Arenas1, S. Sánchez Martínez1 R. Díez Fernández4, L. M. Martín Parra4, J. Matas4, P. Andonaegui1, J. FernándezǦSuárez1 1 Departamento de Mineralogía y Petrología e Instituto de Geociencias (UCM, CSIC). 28040 Madrid, Spain. Email: [email protected] 2 Unidad de Geocronología (CAI de Ciencias de la Tierra y Arqueometría, UCM). 28040 Madrid, Spain. 3 Museum Für Mineralogie Und Geologie, Senckenberg Naturhistorische Sammlungen. Dresden, Germany. 4 Instituto Geológico y Minero de España. 28760 Tres Cantos, Madrid, Spain The Cadomian basement in southern and central Europe consists of Late Ediacaran to Early Cambrian sequences that occur as dismembered along the Variscan Orogen. These ancient series hold within isotopic and geochemical clues related to their deposition in different basins located along the paleo margin of Gondwana and connected with the Cadomian magmatic arc (c. 750-500 Ma), built above this thinned continental margin. In the southwest part of the Iberian Massif, the Ossa–Morena Complex depicts the most external section of the Gondwanan margin and contains an excellent representation of Cadomian basement. The deposition of the oldest sedimentary succession of this region, the Serie Negra Group (c. 600–540 Ma), has been traditionally regarded as related to the opening of a peri-Gondwanan back-arc. However, recent interpretations also consider the possible deposition in a fore-arc or intra-arc context. The Ediacaran Serie Negra Group is composed from bottom to top by the Montemolín Formation, which is formed by metapelites, metagreywackes and abundant amphibolites in addition to black quartzites; and the Tentudía Formation, which is formed by metagreywackes, black quartzites and metapelites. The Serie Negra Group was also the host to a compositionally complex variety of intrusive igneous rocks, in which basic to intermediate, and felsic components variably deformed are recognized. The whole rock geochemistry and the Nd isotopic data obtained from the siliciclastic metasedimentary rocks of the Montemolín and Tentudía formations are compatible with both backand fore-arc tectonic settings. Their Nd isotopic composition exhibits highly negative εNd(0) values ranging between − 11.7 and − 18.1, resulting in old Paleoproterozoic Nd model ages between 1.9 and 1.7 Ga. The homogeneous distribution, with low variation in εNd, can be interpreted as evidence for a shared isotopic source area for both formations, which should have remained available for a long time in the (North African) margin of Gondwana. This uniformity and availability are also observed in the similarly aged Bohemian series whose εNd(0) values range between − 16.6 and − 12.8, and almost identical to their Nd model ages ranging between 2 and 1.6 Ga. The equivalent but limited isotopic variability suggests that the southwestern Iberian and North Bohemian successions likely shared common source area during Ediacaran times, which would have been located close to the periphery of the West African Craton. The Nd isotopic data support a common paleogeographic context and a probable correlation between the Cadomian basement of southwestern Iberia and North Bohemia along the (North African) margin of Gondwana. Ediacaran proto-North Bohemia and proto-SW Iberia were probably part of the same (or closely connected) sedimentary basin(s), where turbiditic siliciclastic series were deposited sharing source areas.