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

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.