PETROGRAPHIC AND GEOCHEMICAL STUDY OF MAFIC DYKES IN APUSENI, POIANA RUSCĂ, AND BANAT (ROMANIA); ARE ALL ASSOCIATED TO THE UPPER CRETACEOUS BANATITIC MAGMATISM IN ROMANIA?

"Apuseni-Banat-Timok-Srednogorie Belt (ABTS) is a complex calc-alkaline magmatic system that formed during the Late Cretaceous period. This belt runs across southeastern Europe, with a north-south orientation in Romania and Serbia and an east-west orientation in Bulgaria, reaching the Black Sea. A large volume of these dominantly calc-alkaline rock association crops out in Romania and is represented by volcanic, subvolcanic and plutonic intrusions and in a late stage by mafic dykes. This research is focused on the mafic dykes of assumed Upper Cretaceous/Paleogene age occurring sporadically and intruding Banatitic subvolcanic/plutonic bodies, metamorphic or sedimentary rocks in the Banat and Apuseni areas. They have been termed before as lamprophyres, however, never properly documented. This is the first dedicated geochemical study on the mafic dykes associated with Banatitic magmatism. The study reveals the presence of two types: calc-alkaline, plotting in basaltic and basaltic andesite fields and alkaline rocks showing two different compositions: alkali basalt and basanite. With the exception of the alkali basaltic dykes that suggest being older (Lower Mesozoic), all the other are following the Banatitic magmatic activity in the studied areas. The calc-alkaline mafic dykes were generated after ~0.5-1 Myr and the basanite dykes during Paleogene times. The calc-alkaline mafic dykes resulted probably by melting of residual metasomatized subcontinental lithospheric mantle (SCLM) with minor contributions with melts of asthenospheric geochemical affinities. The alkaline mafic dykes require an asthenospheric source and generation through an extension condition."