Geochronology, geochemistry and tectonic setting of the Cadomian (Ediacaran-Cambrian) magmatism in the Istranca (Strandja) Massif: new insights into magmatism along the northern margin of Gondwana in NW Turkey

Abstract

Cadomian (Ediacaran-Cambrian) magmatic rocks have been reported in the eastern (e.g. the catalca and Ihsaniye plutons) and western (e.g. the Binkilic and Safaalan plutons) parts of the Istranca (Strandja) Massif. This paper aims to investigate the tectonic setting and the magma evolution history of the Cadomian magmatic rocks using both new and previously existing geochemical and geochronological data. The meta-granitoid rocks with intermediate to felsic composition are the main magmatic activity in the region. They intrude into metamorphic basement rocks composed of gneiss, schist, amphibolite, calc-schist, and quartzites (the Tekedere group). These plutons show strong foliation and traces of the polyphase metamorphism. All plutons are peraluminous and slightly metaluminous, mostly calc-alkaline and high-K calc-alkaline, and plot into the volcanic arc granites (VAG) field on the tectono-magmatic discrimination diagrams. The zircon U-Pb crystallization ages of the plutons are between 525.3 +/- 3.5 Ma and 548.7 +/- 2.3 Ma. Initial epsilon Nd values vary from -0.02 to 1.86. Nd-T-DM model ages range between 1.08 and 1.24 Ga and indicate that the primitive magmas were originated and/or assimilated by the remelting of Neoproterozoic juvenile crustal rocks. New geochemical and geochronological data suggest a magma generation within a subduction-related magmatic arc setting in response to the southward subduction of the Proto-Tethys Ocean during the Late Precambrian-Early Palaeozoic period in the Istranca Massif.