The Classification of Potassium Basaltic Trachyandesites that Were Discharged by the 2012-2013 Parasitic Eruption on Ploskii Tolbachik Volcano, Kamchatka Using Geochemical Criteria

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.