Cambro-Silurian magmatisms at the northern Gondwana margin (Penninic basement of the Ligurian Alps)

摘要: Abstract The Early Paleozoic evolution of the northern margin Gondwana is characterized by several episodes bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in Variscan blocks incorporated Ligurian Alps because they experienced low temperature Alpine metamorphism. During Paleozoic, these blocks, together with other basements, were placed between Corsica-Sardinia and Bohemian Massif along Gondwana. In this framework, host a variegated lithostratigraphy forming two main complexes (Complexs I II) that can be distinguished both protoliths their cross-cutting relationships, which indicate acidic mafic intrusives Complex II cut an already folded sequence made sediments, basalts granitoids I. Both involved orogenic phases as highlighted pervasive eclogite-amphibolite facies schistosity (foliation II). However, rare relicts metamorphic foliation at amphibolite conditions I) locally preserved only rocks It debatable if was produced during early folding event – occurred emplacement rather than stage cycle. New SHRIMP LA ICP-MS U–Pb zircon dating integrated literature data, provide ages volcanic intrusive bodies complexes. igneous activity dated 507 ± 15 Ma 494 ± 5 Ma, while 467 ± 12 Ma 445.5 ± 12 Ma. should therefore have 494 ± 5 Ma 467 ± 12 Ma. metamorphism instead constrained ∼420 Ma ∼300 Ma. geochemical signature allow constraining tectono-magmatic from middle–upper Cambrian rifting stage, through formation Ordovician arc Rheic Ocean subduction, until Late extension related to collapse subsequent PaleoThetys. Furthermore, ∼420–350 Ma rims testify thermal perturbations may associated Silurian rifting-related magmatism, followed subduction-collisional orogeny.