Partition coefficients have been determined for several transition metals amongst a rhyolitic silicate melt, pyrrhotite, and an immiscible Fe-S-O melt. Two sets of experiments were performed in sealed silica tubes at 1035°C-1045°C, FMQ-NNO fO₂, and logfS ₂ ∼1 bar, and analyzed by EMPA and LA-ICP-MS. One set of experiments with Au, Ag, and Cu added yielded ([special characters omitted]) [special characters omitted]=300±100,[special characters omitted] =120±20, [special characters omitted]>200, and [special characters omitted]=120±50, [special characters omitted]=58±8, [special characters omitted]>200. The other set of experiments with Mo and W added yielded [special characters omitted]=90±10, [special characters omitted]9±3 and [special characters omitted]=35±3, [special characters omitted]=1.2±0.6x10^-3. Some preliminary data are also presented on the partitioning of Si, Ti, V, Co, Zn, Re, Th and U. Modeling predicts the loss to a daughter melt of up to 50% of the initial Au, >37% Cu, 24% Ag, 19% Mo, and 2% W when Fe-S-O melts are removed with other cumulate phases during fractionation. This would reduce the metal available to potential intrusion-related hydrothermal ore deposits.