On the Tectonic Significance of Arc Volcanism in Northern Kamchatka

Abstract

The Vyvenka volcanic field records a period of Neogene, subduction-related volcanism in northern Kamchatka. Most models describing the tectonic evolution of the northwest Pacific do not account for this type of Neogene volcanism because the main locus of Pacific/Kula-North American convergence switched to the Aleutian Ridge during Eocene time. The Vyvenka volcanism, as well as oceanic spreading and crust formation within the Komandorsky Basin, demonstrate that this region remained tectonically and volcanically active in Neogene times. We report petrologic, geochemical, and K-Ar age data for the ~15 Ma Golovin and 6-8 Ma Valovayam volcanic rocks, two andesite suites within the Vyvenka volcanic field. The Golovin suite consists of medium- to high-K andesites with strong arc-like trace-element signatures, while the Valovayam suite consists of medium-K andesites with weaker arc-like trace-element signatures. The Valovayam andesites also contain some trace-element ratios indicative of melting of the subducted ...