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-bearing magmatic associations through the nature of protoliths and petrogenetic processes. F and Rb are used to discriminate crustal and mantle derived melts. With the exception of calcalkaline association in which mantle contribution may be significant, the other quartz-bearing associations are essentially derived from crustal melting by biotite and/or amphibole vapor-absent 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 (fH2O/fHF) evolution during cooling are determined for the different magmatic associations. It appears that the liquidus temperature and (fH2O/fHF) decreases in the order high-silica alkaline, high-K calcalkaline and calcalkaline associations while the solidus temperature follows an inverse order. The (fH2O/fHF) values for the peraluminous associations vary over a wide range and overlap the (fH2O/fHF) values of the high-K calcalkaline and calcalkaline associations.