Overview of ophiolites and related units in the Late Palaeozoic–Early Cenozoic magmatic and tectonic development of Tethys in the northern part of the Balkan region

Abstract

The northern Balkan Peninsula, including Serbia, Montenegro, Bosnia, Croatia and the Former Yugoslavian Republic of Macedonia, represents an excellent region for the study of tectonic processes related to Mesozoic Tethyan ophiolite genesis and emplacement. We first summarise the main tectonic units of the northern Balkan Peninsula and then use this information to discuss tectonic processes, including rifting, sea-floor spreading, ophiolite genesis and emplacement, melange accretion, ocean-basin closure and collision. We then discuss alternative models of ophiolite genesis and emplacement for the region and suggest that multi-ocean-basin interpretations fit the data better than single-ocean-basin interpretations. Rifting of Adria (Gondwana) during the Triassic created a rift in the south (Budva zone) and opened a Triassic oceanic basin further north (Dinaride ocean). Occurrences of inferred sub-continental mantle lithosphere in the Dinaride ophiolite belt (e.g. Zlatibor) may record extensional exhumation within an ocean–continent transition zone bordering the Adria/Dinaride continent. This was followed by emplacement together with ophiolites and melange during Upper Jurassic–Early Cretaceous time. Upper Triassic radiolarites and mid-ocean ridge-type basalts formed at a spreading ridge after continental break-up. The oceanic lithosphere of the Dinaride ophiolite belt was partly generated above a subduction zone. The metamorphic soles of the Dinaride ophiolites formed during Mid–Late Jurassic mainly based on K/Ar dating. Widespread melange that is associated with the ophiolites represents a subduction complex, controlled by tectonic accretion and sedimentary reworking in trench and fore-arc basin settings. A possible cause of Jurassic Dinaride ophiolite emplacement was collision of a subduction trench with a continental margin. Further north, Mesozoic oceanic lithosphere subducted northeastwards (present coordinates) opening a Late Jurassic marginal basin in the Main Vardar zone. The Dinaride ocean in the south closed during Late Jurassic–Early Cretaceous time (Tithonian–Berriasian). Deformed oceanic crust, melange and magmatic arc rocks further north (Main Vardar zone) were transgressed by mainly clastic sediments during the Early Cretaceous. However, part of the Vardar ocean (Vardar zone western belt, or Sava zone) remained partially open until latest Cretaceous time. Generally northward subduction within this remnant ocean triggered further supra–subduction zone ophiolite genesis during the Late Cretaceous. The ocean closed by the Maastrichtian, followed by Early Cenozoic regional-scale southward thrusting that locally intercalated older and younger Mesozoic ophiolites and melanges. Future progress particularly depends on determining the crystallisation ages of the ophiolites, obtaining better structural data on the direction of initial ophiolite emplacement and unravelling the Palaeozoic tectonic development of the Eurasian continental margin.