Nature and role of natural alteration gels formed on the surface of ancient volcanic glasses (Natural analogs of waste containment glasses)

Alteration effects of volcanic ash in seawater: Anomalous Y/Ho ratios in coastal waters of the Central Mediterranean sea

“…After 15 days, the measured pH reached values of $7, in good agreement with evidence reported by Crovisier et al (2003). During suspension experiments of basalts in pure water, they observed an increase of initial pH values from 5.5 to 7.5 after 14 days at temperatures ranging from 3 to 60°C.…”

“…10) reflects the effects of rapid glass dissolution and slow precipitation of newly-formed cryptocrystalline montmorillonite-type products, as suggested by Crovisier et al (1987Crovisier et al ( , 2003. The alteration of ash particles by rapid hydration of a pristine glassy fraction may lead to the formation of poorly crystallised (palagonitic) products, whose further ''hydration'' may be responsible for the observed pH increase during the experiment.…”

“…1) emphasises a rapid alteration of the glassy fraction present in the volcanic ash (even in the first metre of the water column). However, the results of Crovisier et al (2003) suggest that such a rapid alteration induces an increase of specific surface area of suspended ash. These are well-reflected in the studied samples by the increase of YREE contents along the water columns.…”

Ancient Glass: A Literature Search and its Role in Waste Management

“…The glass alters to palagonite in young (< 1 My) basalts and zeolites in old (> 1 My) basalts. They also measured the activation energy for natural and synthetic basalt glass and SON68 (aka R7T7) and found it to be the same within experimental error for all three, suggesting that the dissolution mechanism was the same for all three (Crovisier, Advocat, and Dussossoy 2003). This can be construed as implying that a nuclear waste glass like SON68 would be appropriate for the disposal of nuclear waste as it would control the release of radionuclides to very low levels.…”

“…Basalt glasses found in the seas and subsurface are altered first by ion exchange then the formation of palagonite, an amorphous gellike alteration product that contains Fe and Al oxyhydroxides (Kruber, Thorseth, and Pedersen 2008;Crovisier, Advocat, and Dussossoy 2003). Crovisier, Advocat, and Dussossoy (2003) make two points with respect to basalt glass. The glass alters to palagonite in young (< 1 My) basalts and zeolites in old (> 1 My) basalts.…”