Abstract

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. DRb, DZr, and DNb each can be calculated given whole-rock SiO2 and agpaitic index [A.I. = mol (Na + K) /Al]; alternatively, DRb can be calculated given feldspar Or content and agpaitic index. DEu can be calculated given whole-rock SiO2. agpaitic index, and whole-rock Na2O/K2O. Other DREE 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. DSr 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.

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