Nanoscale phase equilibrium in a triggered lightning-strike experiment

We describe the nanometer-sized phases in millimeter-sized spheres produced in a triggered lightning-strike experiment characterized by ultra-high hea ting of similar to 10(8) degrees s(-1) followed by similarly rapid quenchin g. The compositions of the aluminosilica glass spheres define a metastable Al2O3-SiO2 eutectic at similar to 40 wt. % Al2O3 The other phases are defin ed by the liquidus in the SiO2-Al2O3-Fe3O4 (wt %) phase diagram whereby her cynite formed at similar to 1750 degrees C and domains of Fe3+-rich cordier ite glass that represent a ternary minimum melt at similar to 1400 degrees C with cotectic glasses linking this glass and spinel. Metastable eutectics are potentially important to understand the phase relationships due to fla sh heating events.