Distribution of REE, LILE, and HFSE between biotite, feldspar, and the melt in the granulite facies migmatite, nimnyr block, Aldan shield

Abstract

The behavior of trace elements under conditions of partial melting of granitoid rocks has been studied. The element’s partition coefficients between minerals and the melt D ^min/melt _i depends, in the first place, on the composition of the primary melt. In biotite the HREE D _i are a little below 1, while those of LREE, especially D _i for Ce, are 1–3 orders of magnitude less. This leads to an efficient differentiation of REEs in anatexic melts especially when biotite is the main mineral phase of restite. On the contrary, there are feldspars, the D _i of which cannot provide such a magnitude of differentiation. Unlike garnets and pyroxenes, whose stability in restite permits enrichment of anatexic melts produced in migmatization zones with Nb, Ti, and Cr, the presence of biotite in restite causes depletion of melts with those elements as well as with Rb. Feldspars, under conditions of their fractional crystallization or during differentiation of an anatexic melt, deplete the latter with Sr, Ba, and Rb, but enrich it with Nb, Ti, Cr, Y, Zr, and V.