Formation of Clay Minerals During Low Temperature Experimental Alteration of Obsidian

摘要: Experimental alteration of obsidian in distilled-deionized water at 150°, 175°, 200°, and 225°C was studied. The products were examined by X-ray powder diffraction, scanning electron microscopy, transmission microscopy (TEM), energy dispersive analysis (EDX) to evaluate the formation process clay minerals. surface composition before after photoelectron spectroscopy (XPS), concentrations released elements solution measured elucidate dissolution processes. TEM clearly showed that allophane appeared as first reaction product each experiment. With increasing length, noncrystalline straight fibrous material formed aggregates particles a metastable transitional phase, tended form curled or wavy bundles fibers with longer reaction. non-crystalline transformed into highly smectite exhibiting small circular forms less than 1.0 µm diameter progressed. EDX confirmed consisted mainly Si, Al, amounts Ca, K, Fe. XPS revealed dealkalized leached layer on during concentration suggested nonstoichiometric proceeded