## 3 Results
### Melt Compositions  
The quenched melts were analysed in the residual lamproite melt and in the melt traps (Table 5); only in one high-temperature experiment was interstitial melt found in the peridotite section. However, the analysis of the melts in the residual lamproite was  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline Expt & G132 & & G128 & & G138 & & G131 & & G137 & \\ P (GPa) & 2 & 2 & 2 & 2 & 3 &  
complicated by the occurrence of abundant quench crystals, mainly phlogopite. The discrepancy in the total from 100% is principally due to H\({}_{2}\)O, but minor CO\({}_{2}\) may have been generated from the graphite capsule; the concentration of water was not determined independently.  
Melt compositions in the extraction traps were not of uniform composition, but displayed a compositional range, varying with each melt pool analysed, possibly reflecting different extents of melt mixing along paths with different degrees of interaction rather than inhomo  
geneity of analyses. Glass in the melt trap is quench-free, eliminating the possibility that the variation is due to quenching modification of the melt composition. The individual analyses span a wide range of SiO\({}_{2}\) and the behaviour of Al\({}_{2}\)O\({}_{3}\) and K\({}_{2}\)O as a function of the SiO\({}_{2}\) content for experiment G128 (2 GPa, 1125 \({}^{\circ}\)C) is shown in Figure 5; this behaviour is representative for all other experiments. The major elements seem to be largely unaffected by the different time scales of the experiments, except for Ti, Na, K and Ba. All these elements are more enriched in the extraction trap of the longer duration experiment, indicating either slower diffusion processes for them, or they reacted more during migration through the peridotite. This is especially the case for Ba, for which the concentration is nearly twice as high in the longer duration experiment than in the shorter experiment.  
In most experiments the melts in the extraction traps have a significantly higher Mg# than the residual lamprorite melt (averages 74.6 vs. 66.4), lower K\({}_{2}\)O/Na\({}_{2}\)O (averages 2.7 vs. 6.3) and also lower BaO, K\({}_{2}\)O/Na\({}_{2}\)O and K/Al ratios (averages 0.50 vs. 0.80). This reflects the uptake of K\({}_{2}\)O and Ba in phlogopites that grew in the peridotite and the buffering of the Mg# by the peridotite minerals because the volume of the peridotite greatly exceeds that of the reacting melt. The compositions of melts in the residue of the lamprorite section are much less variable than melts in the carbon traps, particularly in terms of Mg# (Figure 6b). Examples of compositional parameters are shown in Figure 6.  
Figure 5: Melt compositions in the melt traps from Experiment G128 (2 GPa, 1125 \({}^{\circ}\)C). SiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\) and K\({}_{2}\)O contents show variation, probably due to different path lengths through the peridotite.  
Figure 6: Comparison of melt compositions in melt traps (squares) with melts in the residual lamproretic section (diamonds): each symbol is the average for one experiment and colours indicate same experiments (see key). Changes across the peridotite reaction column show similar trends to phlogopites due to buffering of the melt Mg# by the peridotite (middle) and the uptake of TiO\({}_{2}\) but release of Cr\({}_{2}\)O\({}_{3}\) in the metasomatic reaction (**a**). The growth of phlogopite in the peridotite also results in lower BaO and near-constant Mg# (**b**), and in lower K\({}_{2}\)O, hence lower K/Al and K\({}_{2}\)O/Na\({}_{2}\)O (**c**).