Fluorine as a tool in the petrogenesis of quartz-bearing magmatic associations: applications of an improved F-OH biotite-apatite thermometer grid

Fluorine contents of whole rock and biotites allow to discriminate quartz-b earing magmatic associations through the nature of protoliths and petrogene tic processes. F and Rb are used to discriminate crustal and mantle derived melts. With the exception of calcalkaline association in which mantle cont ribution may be significant, the other quartz-bearing associations are esse ntially derived from crustal melting by biotite and/or amphibole vapor-abse nt reactions. Based on experimental data and on an improved biotite-apatite thermometer grid, closure temperatures from near-liquidus to near-solidus conditions as well as (f(H2O)/f(HF)) evolution during cooling are determine d for the different magmatic associations. It appears that the Liquidus tem perature and (f(H2O)/f(HF)) decreases in the order high-silica alkaline, hi gh-g calcalkaline and calcalkaline associations while the solidus temperatu re follows an inverse order. The (f(H2O)/f(HF)) values for the peraluminous associations vary over a wide range and overlap the (f(H2O)/f(HF)) values of the high-K calcalkaline and calcalkaline associations. (C) 2000 Elsevier Science B.V. All rights reserved.