Rare-earth elements in historic basaltic lavas are characterized for the first time (1932—1985), for Klyuchevskoi volcano. Analysis of petrochemical data and phenomenological observations show that traces of differentiation are absent in alumina lavas. Alumina and magnesian basaltz originate from one source (chamber).

Long-continues field, and air- and space-borne studies of Kamchatkan volcanoes carried out within the framework of the International Russian-American project "Earth Sciences". In conjunction with the use of deep seismic sounding observations, yielded materials of remote sounding which have been mostly processed for the Klyuchevskoy volcanic cluster, this being the most active and productive in Kamchatka. For the first time ever,
a digital map of volcanoes of the Klyuchevskoy cluster to scale 1 : 100000 has been made. All cinder cones were superposed on the map in a system of coordinates with special indication of the cinder cones in the regional zone of areal volcanism and the eruptive centers of bocca eruptions on Klyuchevskoy volcano along with their petrochemical characteristics and ages. This paper also provides information on the "single primary" magma
of Klyuchevskoy Volcano.

Изучены петрографические, минералогические и геохимические особенности К-трахиандезибазальтов побочного извержения 2012–2013 гг. вулкана Плоский Толбачик. К-трахиандезибазальты имеют явные признаки надсубдукционного происхождения. Это глубоко дифференцированные породы, характеризующиеся значительным фракционированием плагиоклаза. Изучение радиогенных изотопных отношений Sr, Nd и Pb в К-трахиандезибазальтах свидетельствует об их мантийном происхождении и отсутствии влияния земной коры на их составы. Проведен сравнительный анализ отношений содержаний некогерентых элементов в К-трахиандезибазальтов,внутриплитных,рифтогенных и островодужных умереннокалиевых базальтах и андезибазальтах к содержанию этих элементов в примитивной мантии. Геохимические особенности К-трахиандезибазальтов позволяют
отнести их к надсубдукционной субщелочной формации калиевого ряда.

Abstract—This study is concerned with the petrographic, mineralogic, and geochemical features in the K-high basaltic trachyandesites that were discharged by the 2012–2013 parasitic eruption on Ploskii Tolbachik Volcano. These K-high basaltic trachyandesites exhibit some obvious characteristics that testify to their suprasubduction origin. They are deeply differentiated rocks with strongly fractionated plagioclase.A study of the Sr, Nd, and Pb radiogenic isotope ratios in the K-high basaltic trachyandesites provided evidence of their mantle origin and of the fact that the crust has exerted no influence on their compositions. We performed a comparative analysis of the ratios of the concentrations for some incoherent elements in the K-high basaltic trachyandesites, as well as in intraplate, riftogenic, and island-arc moderate potassium basalts and basaltic andesites in relation to the concentrations of these elements in the primitive mantle. The geochemical features of these K-high basaltic trachyandesites classify them as belonging to the suprasubduction subalkaline formation of the potassium series.