LAUSR

Abstract— The mean concentrations of volatiles, major, and trace elements are estimated in the magmatic melts of Kamchatka based on an our database that includes analyses of melt inclusions and quenched glasses of rocks for 75 elements (the database comprised 1 900 000 analyses as of late 2018). The determined concentrations are compared with analogous characteristics of melts from island arcs and active continental margins. The distribution of SiO 2 concentrations (more than 105 000 analyses) in natural magmatic melts from all geodynamic environments is obviously bimodal, with maxima at SiO 2 = 50–52 and 72–76 wt %. The paper presents binary diagrams that show the concentrations of major, volatile, trace elements, and REE and diagrams of the normalized patterns average concentrations of elements in the magmatic melts. The diagrams show distinguishing features of the melts of Kamchatka, for example, the elevated Ba/Nb ratios of Kamchatka mafic melts compared to those of melts in other zones, which may reflect a high content of subduction-related material during the derivation of the Kamchatka melts, with their Th deficit controlled by specifics of the fluid regime.