OCEANOLOGICA ACTA, vol.17, no.5, pp.535-546, 1994 (SCI-Expanded)
Enrichment of Mn in deep-water relative to shallow-water sediments in the Marmara Basin was investigated using earlier metal data and some geochemical information from other similar marine regions on a comparative basis. Deep-water (1152-1276 m) sediments from the three depressions located along the Marmara Trough of the seismically-active North Anatolian Fault Zone contained much higher Mn concentrations (< 6355 ppm; over 10 600 ppm in some core horizons; on a carbonate-free basis) than those from the surrounding shallow-water (54-855 m) sediments (307-2059 ppm Mn on a carbonate-free basis). Cu and Ni showed the same trend altough their concentrations were small. On the other hand, the sediments were not enriched in other metals (Fe, Co). The low variations of Ni, Cu and Co content in both shallow- and deep-water sediments would suggest that there is no significant hydrogenous contribution of Mn to the deep Marmara sediments. While diagenetic Mn enrichment was inferred from typical downcore colour changes, upward-increasing Mn content in the upper core sections and the correlation between Mn and CaCO3 contents in sediments from the lower core sections, the generally high Mn concentrations are believed to reflect, in part, the presence of possible hydrothermal activities along fault planes in the Marmara Basin and external Mn-input from the so-called ''manganese pump zone'' prevailing close to the oxic/anoxic interface (chemocline) in the near-surface waters of the Black Sea.