engleski

LP-HT signature from the Adria-Europe plate boundary realm: The role of mantle/crust interaction in granite generation

The final geodynamic position of the Moslavačka Gora (MG) on the SW margin of the Pannonian Basin (PB) is related to Mesozoic and Cenozoic evolution of the Dinaric segment of the Alpine-Himalayan orogenic belt formed along the Adria-Europe active continental margin. Overall lithology of the MG crystalline can be broadly divided into three main groups: S-type granites which make the core of the MG complex and high- to medium-grade metamorphic rocks (migmatites, gneisses, amphibolites, metapelites) which are present in form of foreign enclaves i.e. xenoliths inside the MG granite pluton. Dm- to m-sized xenoliths bear signature of the polyphase metamorphic evolution of the MG complex with at least two phases being identifiable through specific mineral assemblages. First phase (recorded in amphibolites), which preceded granite intrusion, reached maximum conditions of amphibolite facies metamorphism. The second, Late Cretaceous LP-HT phase, can be separated into two closely related metamorphic events (recorded in the metapelite xenoliths) that took place under low-P amphibolite facies conditions. Pseudosection modelling gave temperature range 585-600 °C and pressure range 390-460 MPa for assemblage Bt + Cd + Pl + Grt + Sil + Qtz while younger assemblage Bt + Chl + Pl + And + Qtz gave temperature 540°C and pressure <250 MPa). Major and trace element chemical data (including REE) favor anatexis of a crustal (meta)pelitic source as a dominant process in the genesis of two dominant types of the Late Cretaceous MG peraluminous granites: two-mica granite (Tmg), and leucogranites (Lg). Occurrence of different types of cognate enclaves, e.g. tourmaline nodules, together with presence of miaroles and magmatic andalusite in the assemblage points to upper crust emplacement level of the intrusion (avg. 5-6 km). Rare MME field occurrences imply genetic link of the MG granite intrusion with Late Cretacoeus LP-HT event and the upper mantle/lower crust mafic intrusion that might be the same that was responsible for Cretaceous gabbro occurences of the MG crystalline complex.

low pressure; high temperature; plate boundary; granite; Moslavačka Gora

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