Tin-bearing aluminosilicate systems in high-temperature processes under variable redox conditions

Experimental results on the state and migration properties of tin in aluminosilicate glasses as a function of temperature and redox conditions are presented. The composition of the glasses approximate those of the main igneous rock compositions. The valence of the Sn and Sn2+/Sn4+ ratio in aluminosilicate phases synthesized at the liquidus temperature and within the fO(2) range typical of natural magmatic systems were determined with Mossbauer spectroscopy; the same determinations were carried out in samples of rocks of respective composition heated to 500 degrees C under oxidizing conditions. The Sn2+/Sn4+ ratio in the initial acid rock samples is higher than in the basaltic rocks. A substantial increase in Sn4+ content in phases heated to 500 degrees C in air was was detected simultaneously with an insignificant change in the Fe oxidation state. ESCA data on the surface layer mineral grains in the initial and heated samples Sn contents in acid solutions that reacted with them testify to the lack of noticeable tin redistribution or increase in its mobilization properties with the change of redox potential.