Evolution of the Western European continental crust: implications from Nd and Pb isotopes in Iberian sediments

摘要: Abstract This paper presents Smz.sbnd;Nd and geochemical data on fine-grained sediments of the Iberian Massif, Spain, together with new published Uz.sbnd;Pb results selected sedimentary rocks. Profiles from two major zones (Cantabrian Central Zone) have been investigated. Both profiles exhibit almost complete stratigraphic successions uppermost Precambrian to Lower Carboniferous. Paleozoic shallow-depth platform are essentially unmetamorphosed; syn-orogenic succession underwent a metamorphic overprint up biotite zone. 147 Sm 144 Nd ratios range 0.0988 0.1457 contents 6 112 ppm. ϵ [today]-values vary −16.5 −7.6, Pb 1.7 97 Samples high Nt [ T ] ( > −3) found be low in μ 2 [330Ma] DM ) 1.92 Ga 1.96 (Central Zone). As juvenile Cadomian crust is present oldest components significantly older than Ga. Within European Variscides comparably old were so far only described Armorican France. An active margin Gondwana continent most probable provenance strata as indicated by their age, facies components. well samples Precambrian-Cambrian boundary gave ]-values −4.8, higher average Contributions must order 30–50% fit data. There no evidence for any addition mafic material according or trace elements, ratios. Cambrian already below −7.3 ]. Thus, compared total pre-existing crust, contribution was very small. all ranging age 515 410 Ma strikingly negative −12.9 −10.1) thus indicate absence newly differentiated continental (s). Only Tremadocian southern Zone −4.0 + 1.0). Again there strata. peaks separated lowermost -7, may added related pre-Ordovician unconformity (Sardic phase). During Middle (410–330 Ma), increase — − 12 ∼ 7, indicating continuous ∼20%. terranes Massif not amalgamated until Late Paleozoic, it can assumed that respective formed within regime one several small subduction zones. isotope this study Brittany, France, suggest Medio-North ArmoricanCentro-Iberian domain persisted Variscan.