ABSTRACT

Transition elements Mn, Fe, Cu, Ni, Co, Zn, V and Cr in the marine surface sediments of the southwestern margin of Japan Sea exhibit clear geographical distribution patterns. Their total contents generally increase with increasing water depth, showing maximum values in the brownish mud which is extensively developed at the depths deeper than about 1000 m. Manganese shows the highest enrichment in the brownish mud, and its distribution pattern in this region is apparently controlled by the redox potential of the sediments. Manganese in the brownish mud is almost entirely extractable with an acid-reducing agent and exists in the form of oxides and/or oxyhydroxides. The extractable Mn is essentially of “suboxic” diagenesis origin, being supplied mainly from the underlying sediments through interstitial water. In contrast, the extractable Fe, Ni, Zn and V in the brownish mud seem to be mainly of hydrogenous origin. In the underlying sediments, these metals are suggested to be incorporated into iron sulfides and hence to make no significant contribution to the upward-migrating components through the interstitial water. Similarly extractable transistion elements in the olive or gray mud from the depths shallower than 1000 m are of hydrogenous orgin.