Geocheminar spring-2013

description: Simple granitic quenched products from hydrothermal piston-cylinder experiments were analyzed by petrographic microscopy and scanning electron microscopy. By textural analysis, the eutectic phase diagram was determined for the simplest model system, albite-water, between 10.0-16.0 kbar and 650-1060o C. The critical end point was found at 16.5±0.8 kbar, 667±37o C and 50.0 weight percent (wt%) water. The same technique has been applied to a relatively more complex model granite (albite, quartz, k-spar). At deep crustal conditions of 10.0 kbar and T=800-900o C where granitic melts are believed to be produced, the water content was found to be underestimated by as much as 30%. The case for dehydration melting becomes increasingly difficult given these new results.