The influence of volcanic ash alteration on the REE composition of marine pore waters

Abstract

Two volcanic ash layer dominated marine gravity cores were recovered during research cruise RV Sonne 173/3 along the Pacific margin offshore Nicaragua. Thick ash layers dominate the recovered sediments. Pore water samples of these – one incoming plate and one slope site – sediment cores have been analysed for light rare earth elements, alkalinity, sulphate, phosphate, ammonia, calcium, and manganese contents. The data provide a systematic look at changes in REE during diagenesis proceeding from open ocean sediments to highly reducing near-shore sediments. The pore water patterns of all the dissolved species mentioned above suggest that volcanic glass alteration constitutes a major source for REE release in marine sediments when low rates of anaerobic degradation of organic matter, like typical for incoming plate/open ocean sediments, prevail. Under these conditions the release of REE results in fluxes of at least 0.04 nmol La cm − 2 yr − 1 and 0.09 nmol Ce cm − 2 yr − 1 .