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Russian Geology and Geophysics

2002 year, number 6

GEODYNAMICS OF MESO-CENOZOIC VOLCANIC COMPLEXES OF VALAGA RIDGE, KAMCHATKA (evolution from spreading to within-plate and island-arc magmatism or accretion of exotic terranes?)

Yu. M. Puzankov
Keywords: Geochemistry, igneous rocks, Meso-Cenozoic, Eastern Kamchatka
Pages: 528-542

Abstract

The paper addresses a comparative geochemical study of volcanic complexes that evolved in the Asia/Pacific transition zone from the Late Cenonian to Present.
Chemical compositions were analyzed in 111 representative samples of Cenozoic rocks from the eastern side of the Valaga Ridge (Eastern Kamchatka) on continuation of the Emperor's Ridge axis, in the region of hotspot volcanism; the dataset also includes 39 additional precise analyses published earlier by Puzankov et al. Trace elements were determined by INAA, XRF, AAS, LL methods and gamma spectrometry developed in UIGGM, Novosibirsk.
The magmatic complexes of Eastern Kamchatka and the surrounding regions were interpreted on the basis of rock chemistry as formed in spreading, island-arc, and transitional geodynamic environments. Broad occurrence of transitional igneous complexes brings together the Meso-Cenozoic volcanic system including magmatic chambers at different depths. Accretion postdates the magmatic evolution. According to paleontological and K-Ar age constraints, the Eastern Kamchatka hotspot has not moved much for 40 Ma (from the Eocene to the Pleistocene), though the total extent of alkaline and subalkaline rocks attains 200-300 km.