The first evidence of Late Ordovician magmatism of the October Revolution Island (Severnaya Zemlya archipelago, Russian High Arctic): geochronology, geochemistry and geodynamic settings

We present a comprehensive study of Late Ordovician (Sandbian) granitic rocks from the southeastern part of October Revolution Island in the Severnaya Zemlya archipelago (Kara Terrane). U–Th–Pb zircon ion-microprobe data and Ar–Ar biotite dating from two samples allow us to determine a crystallisation age for the intrusions at c. 457 Ma. Based on their geochemical and isotopic composition, the granites can be defined as I–type, suggesting island-arc magmatism development within Kara Terrane in the Late Ordovician. This arc magmatism may be correlated with the Mid–Late Ordovician early stage of the Caledonian Orogeny. The obtained data support a tectonic model proposing that the Kara Terrane represented a marginal part of Baltica during the Early to Middle Palaeozoic.