A genetic link between Sb mineralization and magmatism has previously been proposed, yet little is known about the mobility of Sb during magma degassing. We have carried out a series of experiments to understand the effects of fluid composition, oxygen fugacity (fO(2)), pressure and temperature on the partitioning of Sb between magmatic fluids and a rhyolitic melt at crustal conditions (T = 850 degrees C, P = 200 MPa). The experiments were carried out in Molybdenum-Hafnium Carbide (MHC) pressure vessel assemblies at T = 850 to 1000 degrees C, P = 100 to 200 MPa and logfO(2) from 1.64 log units below to 1.78 log units above the Ni-NiO buffer. Antimony partitions into aqueous chloride-bearing fluids weakly, with the fluid/silicate melt partition coefficient of Sb (D-Sb(fluid/melt)) increasing from 0.48 +/- 0.11 (1 sigma) to only 0.85 +/- 0.17 (1 sigma) as the total chlorine concentration in the fluid increases from 0.99 to 16.24 m, indicating the lack of significant Sb-chloride species in the fluid. In contrast, D-Sb(fluid/melt) increased from 0.89 +/- 0.19 to 1.49 +/- 0.19 as the aluminum saturation index (ASI) of the melt increased from 1.02 to 1.24. The moderate increase in D-Sb(fluid/melt) with increasing ASI of the melt (and HCl/metal chloride in the fluid) most likely relates to decreasing Sb solubility in the melt and further demonstrates the lack of significant chloride complexing of Sb. We also found that D-Sb(fluid/melt) is only slightly influenced by fO(2) suggesting that Sb does not change oxidation state (Sb3+) at redox conditions typical of arc magmatism. Furthermore, the presence of reduced S species in the fluid phase caused only a minor increase in DSbfluid/melt indicating that Sb-sulfide complexes are not particularly stable in magmatic fluids. Our data also show that pressure and temperature, within the range of 100 to 200 MPa and 850 to 1000 degrees C, do not significantly influence D-Sb(fluid/melt). Thus it is apparent that at most possible conditions at which rhyolitic melts degas in the upper crust, Sb will only weakly partition into the fluid phase and it is likely that the Sb budget of large epithermal Sb deposits is not directly derived from primary magmatic fluids. (C) 2020 Elsevier Ltd. All rights reserved.