PARTIAL MELTING OF MANTLE PERIDOTITE USING RE FOIL TRAP
I worked with Marc Hirschmann in the experimental petrology lab. The majority of my work dealt with trying to develop a method for trapping low degree melts, especially under 10%. There is a lack of compositional data in these melts constrained experimentally due to several problems. Quenching to a glass is a difficult because such small melt pools often either recrystallize or are often too small to analyze with a micro-beam. The method proposed in the project used a small fold of Rhenium foil to wick the initial melt the experiment. The charge consisted of KLB-1, a spinel lherzolite powder, whose composition is thought to be similar to the parental mantle. The geometry of the foil is created to allow the trapped melt to stay in contact with the rest of charge to allow equilibration and also have glass large enough to analyze.
Establishing the composition for these melts applies to processes of basalt formation, specifically to mid ocean ridges for my experiments at 2GPa at temperatures around the peridotite solidus (1320-1420°C). This method was also used at 3GPa for graduate student Fred Davis's work, applicable to ocean island basalt formation.
Glasses were found in the foil in several experiments. When analyzed, there were some trends in increasing incompatible elements with decreasing melt percent. In the time series conducted at 1400°C, for 6, 12, 24, and 48 hours, analysis showed some indications, but not for certain, that the melt was changing with time showing the melt reaching equilibrium.
Many more experiments need to be run and analyzed in order to establish this as a viable method for trapping melts below 10% and hopefully melts even below 1-5%.