Raman analysis of synthetic fluid inclusions indicates that all experiments contained a single aqueous fluid phase, which - together with a lack of textural or mineralogical evidence for hydrous melting - indicates that the water-saturated solidus for our starting composition is above 900鈥壜癈 at 4.0 GPa. Element concentrations in the fluid for three experiments were determined in situ via laser ablation ICP-MS of individual fluid inclusions. In general, the fluids are enriched in trace elements compared to the bulk starting material, but particularly so for Li, B, LILE, LREE, and U. Chlorite dehydration fluids have high Li/B, LREE/HREE and Ce/Y due to retention of some B in olivine, and retention of Y and HREE in garnet. Our results indicate that fluids produced by serpentinite dehydration at sub-arc depths may carry some of the slab-derived trace elements required for arc magmatism, and may fractionate key trace element ratios in the dehydrated residues, which in turn may ultimately contribute to the geochemical heterogeneity of mantle-derived magmas.