(Table 1, page 168) Iron, manganese, and phosphorus concentrations in Fe-Mn-concretions from the Gulf of Bothnia, northern Baltic Sea

Fe-Mn-concretions of a spheroidal type were found according to electron probe determinations to consist of alternating iron- and manganese-rich layers. This pattern was ascribed to seasonal variations in the physico-chemical conditions governing the precipitation of the hydrous oxides of iron and manganese. Calculations based on the rhythmic growth of the concretions investigated gave a mean accumulation rate of 0.15-0.20 mm/yr. The rather high phosphorus content (average 3.5 % P2O5) of the concretions was found to be concentrated in the iron-rich layers, probably as a result of the scavenging effect of ferric hydroxide.

(Table 19, page 199) Minor constituents of one of the San Clemente iron concretions and its metallic core

The chemical and mineralogical composition of pelagic sediments from the East Pacific Ocean has been determined with the aim of defining the ultimate sources and the mechanisms of formation of the solid phases. The distribution of elements between sea-water, the pore solution and the various solid components of the sediments permits interpretations of the variations in time and space of the gross chemical composition of pelagic clays. For example, manganese, present in sea-water in a divalent form, is apparently oxidized at the sediment-water interface to tetravalent species which subsequently become a part of the group of ferromanganese oxide minerals which are found in the marine environment. It is suggested the rate of manganese accumulation in sediments is some function of the length of time the sediment surface is in contact with sea-water. The contribution of chemical species from the different geospheres is considered. The quantitative importance of pelagic clays in the major sedimentary cycle is studied on the basis of the distribution of the weathered igneous rock products between continental and pelagic deposits and sea-water. These analyses of a wide variety of pelagic clays allow a reformulation of the geochemical balance and it is concluded that pelagic clays account for approximately 13 per cent of the total mass of sediments produced over geologic time.

Annotated record and chemical composition of ferromanganese concretions and crusts sampled from the lakes and streams of Norway

The main objective of the project was to develop a geochemical method for exploration of ores associated with granitic rocks. Fe and Mn oxidates were sampled in streambeds and lakes from 129 localities in Southeastern Norway. 65 of these localities are situated in the northern Oslo Graben. The samples were examined mineralogically and chemically by a variety of methods. Geochemical maps of the element content in oxidates show regional distribution patterns for several elements. Sampling and analysis of oxidates can be used in exploration for mineralizations such as the Skrukkelia Mo-deposit in the northern Oslo Graben. New anomalies (especially for Zn and W) have been detected. Appendix I contains a description of samples, chemical and mineralogical determinations performed on the samples, backscattered electron image-, X-ray image- and scanning electron image pictures of the oxidate preparates. Appendix II contains spectral plots, point analysis with the microprobe, X-ray diffractograms, analytical results, correlation coefficient matrix, scatterplots, frequency distributions and information on data storage. Appendix III containS maps of the element content in oxidates.

(Tables 4-5, page 160) REE contents in ferromanganese concretions from the Gulf of Bothnia and the Barents Sea

Ferromanganese concretions from the Svalbard shelf in the Barents Sea show slightly convex shale-normalized REE patterns with no Eu anomalies. Concretions from the Gulf of Bothnia, northern part of the Baltic Sea, exhibit an enrichment of light REE and negative Eu anomalies. This difference is interpreted as a consequence of different conveyor mechanisms of the REE to the sediment. It is suggested that dissolving biogenic debris contributes to the convex pattern obtained in the Barents Sea, whereas an inorganic suspended fraction with scavenged REE is the main carrier in the Gulf of Bothnia. During oxic diagenesis in the sediment, the scavenged REE are set free into the porewater and contribute to the distribution pattern in concretions found in the Gulf of Bothnia. Small Mn-rich spheroidal concretions are enriched two to five times in REE compared to average shale, whereas Mn-poor flat concretions are low in REE. Specific surface area of the concretion and the depth of burial in the oxidized surface sediment are two factors that strongly affect the enrichment of the REE. Weak Ce anomalies are present in the analysed concretions and a redox level dependence is seen.

Annotated record of the detailed examination of ferromanganese concretions from the Bothnia Gulf, the Baltic Sea and the Barents sea collected by Boström, K. and Ingri, J. (Technical University of Lulea)

The collection of ferromanganese nodules at Naturhistoriska Riksmuseet, Stockholm, Sweden has been donated by Pr. Boström, K. and Ingri, J. from the Technical University of Lulea. They have been collected in the Bothnia Gulf, the Baltic Sea anfd the Barents sea from 1976 until 1985. In 1997 it is was put to the care custody of the Laboratory for Isotope Geology (LIG) of NRM. As part of the Access Project at LIG, Curt Boman has gone through the collection and established a database with detailed information about the samples it contains. Ferromanganese nodules typically display a rounded shape and are formed by redox processes at the interface between the seabed sediment and water. In addition to iron and manganese they also contain other metal elements. Nodules chemical composition reflects the substances found in the sediment to which they are associated. Since the nodules grow continuously, they reflect changes in the sedimentary environment chemistry on a yearly basis, which makes them very interesting as environmental archives. The nodules can be found locally in large quantities and due to their metal content they are also economically interesting as a source of raw materials.

(Table 5, page 626), Tin and main metal elements composition of ferromanganese concretions (acid-soluble fractions)

Concentrations of tin in sea water decreased from estuarine and shelf (0.02-0.04 µg/kg) to surface Atlantic waters (0.009 µg/kg). Mean contents (ppm) in other materials included: ultramafic rocks, 0.8; basalts, 1.7; silicic rocks, 2.5; red clays, 3.4; amphibolites, 1.2. Oceanic ferromanganese deposits contained from 0.2 to 5.8 ppm; tin and cobalt contents were correlated.

Annotated record of the detailed examination of ferromanganese concretions from the Gulf of Bothnia in the Baltic Sea

Ferromanganese concretions cover large areas of the Gulf of Bothnia. They are flat to well-rounded, the rounded ones being richer in oxyhydroxides of iron and manganese. Rounded and ellipsoidal nodules, particularly those in the northern Gulf of Bothnia, are richest in Mn, Ni, Ba and Cu, which probably coexist in a Mn oxyhydroxide phase. Flat nodules are enriched in Fe, P, rare earths and As, probably associated with an Fe oxy-hydroxide component. Aluminum, V, Cr and Ti occur in still another phase. The sediments of the gulf generally consist of a 10-50 mm-thick layer of oxidized surface sediment, enriched in Mn, Ba, P and Ni lying on top of reduced sediments which are diagenetically depleted in these elements. The remobilized elements have redeposited in the nodules, but this process cannot explain the origin of all the nodular material. Some released Mn, Ba and Ni furthermore enter into suspended phases, which eventually leave the Baltic Sea. The economic value of the nodules in the Gulf of Bothnia is probably limited at present.

Annotated record of the detailed examination of ferromanganese concretions from the Svalbard shelf in the Barents Sea

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.

(Tables, page 17-18), Chemical composition of ferromanganese concretions of the lakes of Northern Savolax in Eastern Finland

This paper discusses the occurrence of manganese-rich concretions in the lakes of Northern Savolax in Eastern Finland. The samples were collected in the summer of 1905 and left to dry for 2 months at room temperature. The quantity of H2O mentionned in the analysis was obtained by dessication at 155°C. The amount of Mn is calulated as MnO2 although other valences might be present in the samples. The contents in CO2 and organic substances was not determined. J. Aschan determined that as a general rule, in Finland the manganese rich lake deposits are rather associated with soft bottom sediments while the iron rich deposits are more assocaited with hard or sandy bottoms.