Composition and geodynamic setting of Late Paleozoic magmatism of Chukotka

Resumo

The paper reports the results of petrogeochemical and isotope (Sr-Nd-Pb-Hf) study of the Late Paleozoic granitoids of the Anyui–Chukotka fold system by the example of the Kibera and Kuekvun massifs. The age of the granitoids from these massifs and granite pebble from conglomerates at the base of the overlying Lower Carboniferous rocks is within 351–363 Ma (U-Pb, TIMS, SIMS, LA-MC-ICP-MS, zircon) (Katkov et al., 2013; Luchitskaya et al., 2015; Lane et al., 2015) and corresponds to the time of tectonic events of the Ellesmere orogeny in the Arctic region. It is shown that the granitoids of both the massifs and granite pebble are ascribed to the I-type granite, including their highly differentiated varieties. Sr-Nd-Pb-Hf isotope compositions of the granitoids indicate a contribution of both mantle and crustal sources in the formation of their parental melts. The granitic rocks of the Kibera and Kuekvun massifs were likely formed in an Andean-type continental margin setting, which is consistent with the inferred presence of the Late Devonian–Early Carboniferous marginal-continental magmatic arc on the southern Arctida margin (Natal’in et al., 1999). Isotope data on these rocks also support the idea that the granitoid magmatism was formed in a continental margin setting, when melts derived by a suprasubduction wedge melting interacted with continental crust.