The Sr–Nd–Pb–Hf Isotopic Composition of Late Paleozoic Granitoids in Central Chukotka

Resumo

The results of Sr–Nd–Pb–Hf isotope analysis of Late Paleozoic granitoids of Central Chukotka, which are exemplified by the Kibera and Kuekvun plutons, are presented. The ages of these granitic plutons and of granite pebbles from conglomerates at the base of the overlying Lower Carboniferous strata are 351–363 Ma (U–Pb zircon, TIMS, SIMS, LA–ICP–MS). Thus, granitic magmatism is contemporaneous to tectonic events of the Ellesmerian orogeny in the Arctic region. The Sr–Nd–Pb–Hf isotopic compositions of the granitoids indicate the contribution of mantle and crustal components to the granite melt source. The formation of granitoids probably occurred in the geodynamic settings of an Andean type continental margin with interaction between mantle melts, forming in a mantle wedge under suprasubduction conditions, and the continental crust.