Alteration of volcanic glasses in marine sediments : laboratory experiments and field studies
Large volumes of mainly felsic volcanic ashes have been repeatedly released during explosive volcanic eruptions along the Central American Volcanic Arc. These ashes are found as up to several centimetres thick ash layers in marine sediments offshore Nicaragua and Costa Rica. Since volcanic ashes constitute such a major fraction of slope sediments and subducted deep sea sediments off Nicaragua and Costa Rica its alteration is significantly affecting the chemical signatures of sediments and pore waters. New results of mafic and felsic glass alteration were derived from extensive field investigations of marine tephra. deposits and diagenetic processes in related pore waters as well as laboratory dissolution experiments.