The effect of F on the density of haplogranite melt
b'The densities and thermal expansivities of F-bearing haplogranitic glasses and liquids\\nhave been investigated using a combination of scanning calorimetry and dilatometry.\\nF2O-1 reduces the density of haplogranitic liquids (at 750 \\xb0C) from 2.295 + 0.006 g/cm3\\nto 2.261 + 0.005 g/cm3 with the addition of 4.55 wt% F (0.33% per wt% of F added). The\\nexpansivities of the liquids increase with the addition of F2O-1 from 29.9 +- 3.0 x l0 -6/\\xb0C to 53.1 +- 1.4 x l0 -6/\\xb0C (at 750\\xb0C).\\nDensities have been converted into molar volumes based on the haplogranite and F2O-1\\ncomponents. The partial molar volume of F2O-1 has been calculated at 750\\xb0C to be 14.2\\n+- 1.3 cm3/mol in these melts. This value is close to the molar volume per O for several\\ncomponents of silicate melts. F and O have similar ionic and covalent radii, and thus the\\nsubstitution of two F for one O yields approximately the volume change expected, assuming\\nno secondaryc onsequencesfo r the averagec oordination number of cations. This is\\ndespite evidence from quenched melts that [6]Al exists in these compositions.\\nF is significantly more effective (per wt% added) than B2O3 in reducing the density of\\nhaplogranitic melt. The effect of F on density reported here should complement the viscosity-\\nreducing effect of F2O-1 on granitic melts in significantly acceleratingg ravity-driven\\nprocesses of crystal-melt fractionation in F-rich igneous systems.'