Partition of Trace Elements between Minerals and Melt: Parameterization of Experimental Data on Olivine, Pyroxene, and Feldspars

Abstract

The partition of trace elements between minerals (olivine, orthopyroxene, clinopyroxene, and feldspars) and silicate melts is analyzed based on experimental data within broad P–T ranges (from 1 atm to 10 GPa and ∼1000–2000°C) and the compositions of melts (from ultramafic to ultrasilicic) and minerals. The dependences of the logarithmic partition coefficients (lnD_i) on P–T parameters and compositions are approximated by linear functions of 1/T, P/T (where P is pressure and T is temperature in K) and compositional parameters of the minerals and melts. The D_i/D_j ratios of a large number of pairs of elements are found out to be independent of experimental parameters and vary within narrow ranges. The parameters of the dependences of D_i on P–T and compositions are estimated by minimizing the squared deviations of model D_i and D_i/D_j values from experimental ones. The dependences thus derived make it possible to calculate D_i for numerous elements accurate to a factor of 1.2–2.0. As an illustrative example, a model is discussed for the derivation of mafic basaltic melts in mid-oceanic ridges at the melting of a peridotite source and crystallization of primary magmas under crustal parameters.