Variations of Source Composition and Melting Degrees of Olivine-Phyric Rocks from Kamchatsky Mys: Results of Geochemical Modeling of Trace Element Contents in Melts

Abstract

Abstract: We conducted the geochemical modeling of trace element contents for primary melts of olivine-phyric rocks from Kamchatsky Mys. This modeling reveals substantial chemical heterogeneity of their source while the average source composition is close to the enriched DMM (E-DMM). The average estimation of the melting degree is in the range from 9.1 ± 3.8% for the model of modal batch melting to 15.4 ± 5.2% for the model of accumulated fractional melting, which is slightly higher than the estimation for primitive mid-ocean ridge basalt (MORB) glasses (7.4 ± 2.2% and 12.5 ± 3.8% respectively). It is in a good agreement with high melting degrees estimated earlier for other rocks of the Kamchatsky Mys ophiolites. Low pressure of mantle melting caused by the elevated speed of decompression relative to the average MORB could explain elevated melting degrees estimated for Kamhcatsky Mys ophiolites as well as their characteristic Sr-anomalies and sulfide saturation on the earliest stages of magmatic evolution.