(Table 11-I, page 338) Metal contents (%) of a representative sampling of manganese nodules from the North Pacific high-grade region

Two types of deep-sea dredges are currently under development for the mining of the manganese nodules, a deep-sea hydraulic dredge and a mechanical cable-bucket system. Both systems offer some advantages with the hydraulic system appearing to be advantageous in themining of a specific deposit for which it is designed while the cable-bucket system appears to be somewhat more flexible in working in a variety of deposits, topographic environments, and water depths. Environmental studies conducted in conjunction with deep-sea tests of the two types of mining systems currently indicate that substantially no environmental damage will be done in the mining of the deep-sea nodules. Because of the nature of the deposits and the way in which they can be mined, the manganese nodules appear to be a relatively pollution free and energy-saving source of a number of industrially important metals.

Composition of sedimentary material from the bottom and the area surrounding the Lake Untersee, East Antarctica

This paper presents data on geographic and geologic conditions of modern sedimentation in the Lake Untersee, the largest lake in the East Antarctica. Geochemical and sedimentation data indicate that the leading mechanism supplying aluminosilicate sedimentary material to the surface layer of bottom sediments is seasonal melting of the Anuchin glacier and the mountain glacier on the southeastern part of the valley hosting the lake. Strongly reduced conditions in the lowermost 25 m of the water column in the smaller of two depressions of the lake bottom were favorable for enrichment of the bottom sediments in bacteriogenic organic matter, Mo, Au, and Pd. H2S-contaminated water results to significant enrichment of the sediments only in redox-sensitive elements that are able to migrate in anionic complexes and precipitate (co-precipitate) as sulfides.

Permian manganese nodules near Dillon, Montana

Concentrically ringed manganese nodules, similar in form to many found on modern ocean and sea floors, occur in a very fine grained argillaceous sandstone bed of the Permian Park City Formation near Dillon, Montana. They are enriched in many rare elements and contain us much as 2.5 percent zinc, l.3 percent nickel, and 0.22 percent cobalt. The manganese minerals are chalcophanite and todorokite. The nodules probably formed in a shallow marine oxidizing environment on the western side of the Permian sedimentary basin. The occurrence of an appreciable amount of fluorite in the bed suggests that the water was saline.

Geochemistry on sediments in Lake Biwa

Thirty sediment cores (30-40 cm in length), 47 Ekman dredge sediments, and Mn concretions were collected from Lake Biwa. The concentrations of 36 elements in the samples were determined by instrumental neutron activation, X-ray fluorescence, atomic absorption, and colorimetric analyses. The elements determined included Mn, P, As, Sb, Fe, Ni, Co, Zn, Cu, Pb, Hg, Cr, Ti, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Sc, Hf, La, Ce, Sm, Eu, Yb, Lu, U, Th, Au, Ta, Nd, Br and N. Based on statistical considerations and calculation of the concentration factors of the elements, the features of the elemental distribution in Lake Biwa sediment were determined. The main results are summarized as follows : (1) Concentrations of Mn and As were very high in the uppermost oxidized layer of the offshore sediment and Mn concretions. This resulted from the dissolution-deposition cycles of these elements within the sedimentary column and the bottom water. The fixation of As at the sediment surface is mainly attributed to the adsorption of arsenate onto Mn (II) -rich hydrous Mn (IV) oxide. (2) There were high concentrations of Zn, Cu, Pb and Hg in the recent sediments. Although the source of these elements is attributed to human activities, the individual distributions of Zn and Cu in the sediment may result from the deposition of metal-rich planktonic debris and subsequent degradation of the debris. (3) The orders of increasing concentrations of alkali metals and lanthanides in the sediment from the central region compared with the nearshore pediment were identical to the orders of increasing atomic numbers from Na to Cs and from La to Lu, respectively.

Annotated record and chemical composition of iron-manganese nodules from the Baltic Sea

Iron-manganese concretions, closely related to lacustrine ores and deep sea manganese nodules, are presently forming in different parts of Gulfs of Bothnia and Finland. They can be divided according to physical form into three distinct groups: (1) round pea-shaped concretions, (2) ring-shaped concrections, and (3) flat sheets and crusts of concretionary material. A definite correlation was found to exist between the form i.e. type of concretions and their chemical composition (Mn/Fe ratio). Trace element concentrations were generally rather high, although not as high as in deep sea manganese nodules. X-ray and DTA was used to study the mineralogy and crystal structure of the concretions. Surface concentrations and geographical distribution of the concretions were estimated on the basis of samples, diving observations and echo-grams.

Description and chemical composition of ferromanganese encrustations and deposits in the Atlantic Ocean from R/V Atlantis II cruises 20, 42, 60, 85; R/V Chain cruise 35; R/V Knorr cruise 61 and RRS Shackleton cruise 75/1 stations

Chemical and mineralogical compositions of ferromanganese oxide coatings on rocks dredged from the New England Seamounts, the Sierra Leone Rise and the Mid-Atlantic Ridge near the Equator have been determined in an investigation of regional differences in Atlantic ferromanganese deposits. Most encrustations are clearly of hydrogenous origin, consisting mainly of todorokite and delta MnO2, but several recovered from the equatorial fracture zones may be hydrothermal accumulations. Differences in the chemistry of the water column and in growth rates of the ferromanganese coatings may be important in producing this regional contrast in composition. Fine-scale changes in element abundances within the encrustations indicate that the nature of the substrate has little influence on compositional variations.

(Table 2) Geochemical composition of suspended matter samples from the northern Dvina River

The results of the analysis of samples of the Northern Dvina River's suspended particulate matter obtained by the sedimentation method from large water volumes in the periods of the spring high water and summer low water are presented. By the method of sequential leaching using different reagents, four fractions have been separated: the F1 is the sorbed complex and carbonates, the F2 is the amorphous hydroxides of Fe and Mn, the F3 is the form connected with the organic matter, and the F4 is the residual or silicate-detrital (inert) form. The data have shown that all ten elements determined were grouped with respect to the ratio of the distinguished forms: F4 is the predominant form for Al and Fe (73-88% of all the forms; however, the summer sample contains only 38% of this form of iron, and F2 is the predominant form for this period with 46.6%). As to Mn, the F1, F2, and F4 are nearly equally distributed in the spring high water samples, and only the F3 form is less important (5.4%). In the summer sample, the manganese sorbed complex is predominant (53.5%); for Cu, Ni, Cr, and Co, the inert F4 form is predominant (60-70%) in the sample of the spring suspended matter. The summer low water suspended matter has a lower F4 contribution (25-45%); for Zn, Pb, and Cd, the equal distribution of the forms in the spring samples is typical, while the summer suspended matter differs by the F2 form's predominance (53-61% for Zn and Pb). The main conclusion from the acquired data is that the geochemical mobility of all the studied elements, except for cadmium, in the summer low water suspended matter is higher than in the spring suspended matter. The more intensive biogeochemical processes in August, the high level of organic matter, and the higher contribution of phytoplankton lead to the intensification of the metals' geochemical activity in the Northern Dvina suspended matter in the end of the summer compared to the spring high water period when the physical processes are predominant over the biogeochemical ones due to the high speeds of the freshened waters flow.