Isotope-Geochemical Heterogeneity of Igneous Rocks of Island-Arc Terranes of Eastern Kamchatka

The differences in the material composition of rocks that make up individual volcanic fields within the island-arc terranes of Kamchatka are shown. It has been established that Cretaceous rocks of the northern segments of the Kronotsky terrane are characterized by volcanic rocks of the low-potassium tholeiitic series, while the southern segments are characterized by calc-alkaline rocks. Eocene volcanism is represented by relatively homogeneous volcanics of the tholeiitic series. The composition of the volcanic rocks of the Ozernovsko–Valaginsky terrane (paleoarc) is more diverse and is distinguished by the development of high-potassium series rocks. Isotope-geochemical analysis of basalts from the Kronotsky and Ozernovsko–Valaginsky terranes allows us to speak, in general, about the depleted nature of deep magma sources, and that the formation of magmas involved components of different compositions in different proportions: supraslab, OIB, and N-MORB. The behavior of fluid–mobile elements among basalts shows that their concentrations exceed those in N-MORB, indicating the involvement of fluids and melts to varying degrees in magma generation.