(Table 2, Page 287) Chemical composition of manganese nodules from GH76-1 cruise

Chemical analyses of manganese nodules from the Central Pacific Basin show that their chemical composition varies regionally, although that of the associated sediments is markedly uniform throughout the basin. Mn content varies from 16 to 32% in average. Its higher value is generally found in nodules from siliceous clay and a few from deep-sea clay. Fe content tends to enrich in nodules from deep-sea clay area. Most manganese nodules, except those from deep-sea clay, are remarkably depleted in Fe compared with ones from the other Pacific regions. Mostly, Cu and Ni contents exceed 1% in nodules from siliceous clay, and decrease towards the northwest of the basin where deep-sea clay is distributed. The inter-element relationship between manganese nodules and associated sediments suggests that the mechanism of incorporation of major and minor elements in nodules is apparently different from that of the associated sediments. This finding seems to provide a new interpretation on the problem why manganese nodules having low accumulation rate are not buried by the associated sediments with greater sedimentation rate and then occur on sediment-seawater interface.

Chemical composition and rate of accumulation of manganese nodules in the western North Pacific

The major and some of the minor constituents and the rate of accumulation of manganese nodules in the western North Pacific were determined. Manganese concentration in the nodules ranged from 20 to 30 per cent in the acid soluble fraction. As to the rare earth concentration, enrichment of cerium was observed in the manganese nodule as compared with that in shales or sea water. Thorium to uranium ratio in the nodule ranged from 9.4 to 14.3, which was very much higher than that in sea water. From the distribution of excess ionium, excess protactinium and Io/Th ratio, a rate of accumulation of 7 mm per million years was obtained with the surface layer of several mm in thickness of the JEDS-4-E4 nodule.

(Table 2, Page 106-107) Composition of the HCl-soluble fraction in Barents Sea iron-manganese deposits

Ferromanganese concretions from ten stations in the Barents Sea have been analysed for 24 elements. The deposits occur as discoidal and flat concretions and as coatings, in the latter case on lithified or detrital material or as extensive pavements on the Svalbard shelf. The concretions are compositionally similar to Baltic concretions but differ considerably from deep-ocean nodules, particularly in Cu, Ni and Co contents. Statistical analyses reveal distinct correlations between Mn, Na, Ba, Ni and Cu; the Mn-rich coatings showed enrichment of Mo, Zn and possibly Co in a Mn-phase. The iron phase holds high concretions of P and As. Two iron-rich concretions with high contents of P, Ca, Sr, Y, Yb and La were found east and northeast of Spitsbergen Banken, probably indicating upwelling of nutrient-rich, cold polar water along the Svalbard shelf.

(Table 1, page 171) Thorium and cobalt content of the total aggregate of manganese nodules from various locations

A criterion is suggested for discrimination between ferromanganese oxide minerals, deposited after the introduction of manganese and associated elements in sea water solution at submarine vulcanism, and minerals which are slowly formed from dilute solution, largely of continental origin. The simlultaneous injection of thorium into the ocean by submarine vulcanism is indicated, and its differentiation from continental thorium introduced into the ocean by runoff is discussed.

(Table 1, page 641) Hf isotope time series for the uppermost part of a ferromanganese crust from the San Pablo ferro-manganese pavement

The Hf isotope composition of seawater does not match that expected from dissolution of bulk continental crust. This mismatch is generally considered to be due to retention of unradiogenic Hf in resistant zircons during incomplete weathering of continental crust. During periods of intense glacial weathering, zircons should break down more efficiently, resulting in the release of highly unradiogenic Hf to the oceans. We test this hypothesis by comparing Nd and Hf isotope time series obtained from NW Atlantic ferromanganese crusts. Both isotope systems show a decrease associated with the onset of northern hemisphere glaciation. The observed changes display distinct trajectories in epsilon Nd- epsilon Hf space, which differ from previously reported arrays of bulk terrestrial material and seawater. Such patterns are consistent with the release of highly unradiogenic Hf from very old zircons, facilitated by enhanced mechanical weathering.

(Table 1, page 41), Chemical and radiocativity analysis of manganese crusts from the Lika river, Vermland, Sweden and ferromanganese ore from lake Tisjoen, Dalecarlia, Sweden

The trace element content of different bog ores has been measured and it appeared that most of these elements are enriched in the manganiferous bog ores as compared with the ferriferous ones. The manganiferous bog ores have also proved to have a higher radioactivity than the ferriferous ones.