Early diagenetic processes affecting nutrients in the pore waters of Central Indian Ocean cores

Abstract

Pore-water nutrients, nitrite, nitrate, phosphate, silicate, pH and solid-phase organic carbon were analysed for one core from the Arabian Sea and three cores from the manganese nodule area in the Central Indian Ocean Basin. Possible denitrification and unoxidized organic carbon are observed in the Arabian Sea core, while nitrification with intermediate low nitrate and high organic carbon are found in the mottled zones of the pelagic cores. Mobilization of iron-host oxyhydroxides and peaked profiles of organic carbon are related to a gradual increase in the phosphate profiles. The asymptotic silica values are less than the 100% saturation levels of amorphous silica and they fall outside the stability field of sepiolite