Late Cretaceous–Early Paleogene Volcanic Rocks of Eastern Kamchatka (Compostional Features and Isotopic-Geochemical Heterogeneity)

New and previously published data on the isotope-geochemical characteristics of the Upper Cretaceous and Early Paleogene complexes of the Ozernoy–Valaginsky segment of the Achaivayam–Valaginsky paleoarc are presented. It has been established that the material composition of the rocks of the Achaivayam–Valaginsky paleoarc (terrane), which form individual volcanic fields within the terrane, differs. Thus, on Karaginsky Island, volcanics of the moderate-potassium calc-alkaline and shoshonite series are widespread. On the Ozernoy Peninsula, low-potassium basalts of the tholeiitic series have predominantly developed. Among the rocks of the Kumroch Ridge, the following stand out: low-potassium basalt–andesite–basalt, medium-potassium calc-alkaline and high-potassium shoshonite series. Volcanic rocks of the Tumrok ridge are represented by low-potassium picrites and high-potassium trachybasalt–trachyandesites. On the Valaginsky Ridge, low-potassium tholeiitic, moderate-potassium calc-alkaline and shoshonite-latite series are distinguished, as well as picrites and lamproitoids. The isotopic (Sr, Nd and Pb) and geochemical composition of the rocks indicates their formation from a depleted mantle source within an ensimatic volcanic arc. It has been demonstrated that, in the absence of significant differences in the material composition of rocks, regional differences are evident. The enrichment of volcanics with large-ion lithophile elements is explained by the role of fluids introduced into the melts during melting of the suprasubduction mantle wedge. The issues of the region’s geodynamics are considered.