| Na, K, Al, Rb, Sr, Cu, La, Ce, W, Mo, and Ge distribution between a haplogranitic melt and a pure H$sb2$O or an aqueous fluid containing HCl, NaCl, NaCl + KCl, NaF, $rm Nasb2COsb3$, or $rm Nasb2COsb3$ + $rm Ksb2COsb3$ was investigated at 750-800$spcirc$C and 1-4 kbar. The distribution coefficient of Na, K, Rb, Sr, and Cu increases with (Na,K)Cl content in the fluid, whereas the partitioning of W, Mo, La, Ce, and Ge is not obviously affected by (Na,K)Cl concentration in the initial solution. The presence of (Na,K)$sb2$CO$sb3$ in the fluid has virtually no effect on the partitioning of Al, Sr, La, Ce, W, and Ge, and a slight positive effect on the partitioning of Na, K, Rb, Cu, and Mo. The presence of NaF in the fluid has no effect on the partitioning of Na, K, Rb, Sr, Cu, Ge, La, and Ce, a slight positive effect on Al. The presence of small amounts of NaF significantly increases the distribution coefficient of Mo and W. However, the distribution coefficient of both elements decreases with increasing NaF content in the fluid. The distribution coefficient of all the elements studied increases significantly in the increasingly peraluminous melts ( ((Na+K)/Al) $sb{rm melt} < 0.3$ (molar)), resulting from an increasing concentration of HCl in the initial solution. Since the composition of (Na,K)Cl-bearing fluids is not significantly different from that of HCl-bearing fluids at experimental conditions, it is concluded that the high degree of polymerization in the silicate melt is the main reason for the high distribution coefficients of the elements for HCl-bearing fluids. The results of this study are important for the understanding of hydrothermal ore mineralization.;In this study, the chemical diffusivity of Cl in granitic and haplogranitic melts was determined as a function of temperature (650-1400$spcirc$C), pressure (1 bar-4.6 kbar), H$sb2$O content, and NaCl concentration. Cl diffusion follows the Arrhenius equation. The pressure effect at 850$spcirc$C is moderate. D$sb{rm Cl}$ decreases with the concentration of NaCl in the initial solutions. D$sb{rm Cl}$ in runs with a 10 wt.% HCl solution is several times higher than with a 10 wt.% NaCl solution at the same PT conditions. It was found that D$sb{rm Cl}$ increases very sharply with the addition of H$sb2$O to the glass to 2-3 wt.%, further addition of H$sb2$O has a significantly smaller effect. This difference is interpreted as a result of the change in the melt structure. The relationship of D$sb{rm Cl}$ and viscosity does not follow the Eyring equation. The results of this study, combined with other investigations suggest that diffusion rates of volatiles decrease as: $rm COsb2 > Hsb2O > Cl > F.$ This indicates that during magma evolution differentiation of the volatile constituents may occur. In addition, the chemical diffusivity of K in a hydrated granitic melt was determined at temperatures of 750$spcirc$-900$spcirc$C and pressures between 1 and 5.6 kbar. K diffusion follows the Arrhenius equation; its activation energy is about 20 kcal/mole and activation volume is about 20 cm$sp3$/mole under the conditions investigated. The diffusivity of K was found to be very sensitive to pressure. |
