COPPER MIGRATION IN ALUMINOSILICATE GLASSES UPON HEATING AS A POSSIBLE SOURCES OF COPPER MINERALIZATION

Abstract

The behavior of copper in magmatic and postmagmatic processes, like that of other ore elements of variable valence, is controlled in many respects by its form, which, in turn, depends to a considerable extent on the redox conditions. The form of copper in magmatic melts must essentially control its behavior during their differentiation and, to a considerable extent, its subsequent migration in the postmagmatic stage, particularly if volcanic glasses are then heated under oxidizing conditions. The latter problem was the aim of the work described in this article. Comparative study of copper distribution in the synthesized glasses and in glass grains heated at 500°C in air indicates that upon heating, copper migrates outward from the core of grains. Thus, the behavior of copper, established experimentally by heating aluminosilicate glasses that had been synthesized under the real redox conditions of natural systems with monovalent copper predominant - namely, the migration of copper outward from grain cores and the formation of CuO at the surface, could cause what Govett identified as the depleted mode of copper distribution in cores of lava pillows which are located near ore bodies and appear to have been strongly heated. The subsequent flow of hydrothermal solutions through heated pillow-lava sectors would have led to their marked enrichment in copper, because they would have dissolved CuO from pillow surfaces and removed copper from the hydrothermally altered rocks.