Early cenozoic magmatism in the continental margin of Kamchatka

The paper presents isotopic-geochemical features of magmatic rocks that were produced at the continental margin of Kamchatka during its various evolutionary stages. Continental-margin magmatism in Kamchatka is demonstrated to have evolved from the Paleocene until the present time. The Paleocene and Middle-Late Eocene magmatic complexes show features of suprasubduction magmatism. The magmatic melts were derived from isotopically heterogeneous (depleted and variably enriched, perhaps, as a consequence of mixing with within-plate melts) mantle sources and were likely contaminated with quartz-feldspathic sialic sediments. The Miocene preaccretion stage differs from the Paleogene-Eocene one in having a different geochemical and isotopic composition of the mantle magma sources: the magmatic sources of the Miocene suprasubduction magmas contained no compositions depleted in radiogenic Nd isotopes, whereas the sources of the within-plate magmas were enriched in HFSE. The Late Pliocene-Quaternary postaccretion magmas of the Eastern Kamchatka Belt are noted for the absence of a within-plate OIB-like component.