Multivariate linear regression (MLR) analysis has been used to develop equations for predicting alkali feldspar/melt trace-element partition coefficients (D-values) for certain large-ion lithophile elements (Rb and Eu), high field-strength elements (Zr and Nb), and rare-earth elements (Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Er, and Yb) in peralkalic felsic systems. A partitioning equation for Sr based solely on data from Pantelleria is also presented. D-Rb, D-Zr, and D-Nb each can be calculated given whole-rock SiO2 and agpaitic index [A.I. = mol (Na + K) / Al]; alternatively, D-Rb can be calculated given feldspar Or content and agpaitic index. DE, can be calculated given whole-rock SiO2, agpaitic index, and whole-rock Na2O/K2O. Other D-REE can be calculated given whole-rock SiO2, agpaitic index, and whole-rock CaO. These D-values all increase with increasing whole-rock SiO2 and decreasing agpaitic index. D-Sr for samples from Pantelleria increase with increasing feldspar Ab and can be calculated given feldspar Ab content. The equations formulated will help to constrain better the choice of D-values used in petrogenetic models of peralkalic systems.
