EXPERIMENTAL STRATEGIES FOR THE INVESTIGATION OF LOW-TEMPERATURE PROPERTIES IN GRANITIC AND PEGMATITIC MELTS

The physical behavior of silicate melts during the Final stages of int rusion in the earth's Crust arc poorly understood. In particular, the low temperature limit of igneous petrogenesis is poorly constrained. T he extreme differentiates of granitic magmatism that lead to pegmatite genesis span a very large range of composition not normally considere d to be within the domain of igneous melt compositions. This combinati on of very low petrogenetic temperatures and extreme chemistries requi res a concentrated effort for the determination of melt properties und er conditions of pressure, temperature and composition appropriate to these systems. An experimental strategy for the determination of melt properties under appropriate conditions is presented. The determinatio n of individual melt properties at very low temperatures is described with the aid of three examples, heat capacity, volume and viscosity. I n this way the physical behavior of an important component of the eart h's crust will become accessible.