Solution of naturally-occurring glasses in the geological environment

Abstract

As part of a study to investigate the feasibility of encapsulating nuclear wastes in glass ingots and burying them on land or dumping them in the ocean, we have made a study of the amount of solution experienced by naturally-occurring glasses from two land sites and thirty-four deep-sea sites. The glasses used in this study are microtektites from strewn (Australasian, Ivory Coast, and North American) and from the Zhamanshin impact structure in southern Siberia. The microtektites range in age from 0.7 to 35 m.y. and they have a wide range in composition. The weight per centy SiO2, for example, ranges from 44.8 to 81.7. Although several criteria for determining the amount of solution were considered, most of the conclusions are based on two criteia: (1) width of cracks, and (2) elevation of silica-rich inclusions above the adjacent microtektite surface. All the measurements were made on scanning electron microscope photomicrographs of the microtektites. The amount of solution was determined for about 140 microtektites; and measured amounts of solution range from 0.2 to at least 28 μm, but most are less than 5 μm. There appears to be no systematic relationship between age and amount of solution. Solution amounts are higher for microtektites in terrestrial settings than for microtektites in deep-sea environments, but in both environments the amount of solution increases with decreasing SiO2 content.