Kurt Boström

CHEMISTRY OF SUSPENDED PARTICLES IN THE SOUTHERN BALTIC SEA

Dissolved and suspended concentrations of Al, Ba, Fe, Mn, and Si and suspended P and Ti have been studied in the Baltic proper, the Belt Sea-Kattegat and the Aland Sea. Approximately 20% of total A ...

Genesis of Ferromanganese Deposits-Diagnostic Criteria for Recent and Old Deposits

Marine iron manganese deposits show a greater chemical variability than was realized only 10 years ago. As a consequence correct conclusions regarding the genesis of a given deposit frequently require knowledge about several geochemical parameters and preferably about accumulation rates and spatial relations vis-a-vis e.g. spreading centers.

10Be records from sediments of the Arctic Ocean covering the past 350 ka

Records of Be-10, Be-9, mineralogy and grain size were obtained from two cores collected by the Polarstern Expedition 1991 in the southern Nansen Basin (Core 2213-6) and the Yermak Plateau (Core 22 ...

Hydrothermal quartz vug from the Mid-Atlantic Ridge

A site dredged on the east wall of the rift valley of the Mid-Atlantic Ridge at lat 24°21′N is characterized by a low in residual magnetic intensity similar to that observed at the TAG Hydrothermal Field in a structurally equivalent position 250 km to the north. Tholeiitic basalts that have undergone hydrothermal alteration, forming chlorites, analcime, calcite, and quartz-rich rocks, were recovered. The quartz is a late remobilization product, occurring in cracks and vugs as massive fillings and euhedral crystals. Oxygen-isotope thermometry indicates that the quartz was deposited from hydrothermal solutions comprising either sea water at 200 °C or primary water at 330 °C, consistent with a history of intense hydrothermal activity and the use of the magnetic low as a signature to identify such activity.

Origin of iron-manganese-rich suspended matter in the Landsort Deep, NW Baltic Sea

Abstract Water sampling was undertaken in 1982 in the Landsort Deep, NW Baltic Sea, at eight depth levels. In the 0–150 m interval oxidizing conditions prevailed, with suspended phases being particularly rich in Fe (with a maximum at 150 m), Mn and Ba (with maxima at 100 m). The anoxic zone below 150 m showed high concentrations of dissolved Fe and particularly dissolved Mn which were much higher than in the Black Sea, for instance. This is probably due to the migratory behavior of the redoxcline in the Landsort Deep. The metal-rich suspended matter probably arises when dissolved Fe and Mn from the anoxic zone precipitate as hydroxyoxides at the redoxcline; lateral transport of such suspended matter may explain the large-scale selective loss of Mn and Ba from the Baltic basin.

Mineralogical control on transition metal distributions in marine manganese nodules

Abstract Electron microprobe and X-ray diffraction data for north Pacific manganese nodules reveal that the transition metal distributions are controlled by the mineralogy. Microlayers rich in 10A-manganates generally have high Mn Fe ratios and positive correlations between Ni, Cu and Mn, and between Co and Fe. Microlayers rich in vernadite, on the other hand, show low Mn Fe ratios, and Co, Ni and Cu all show positive correlations with Mn. The 10A-manganates form mainly in porewaters with high Mn Fe ratios. The Ni2+ and Cu2+ ions are post-depositionally incorporated into the interlayers of the manganates, whereas Co3+ is substituted for Fe3+ in ferric oxyhydroxides. In seawater with a low Mn Fe ratio, on the other hand, the adsorption of positively charged ferric oxyhydroxides on negatively charged [MnO6] octahedral layers suppresses the growth of 10A-manganates, enhancing the formation of vernadite. Positively charged hydroxides of Co3+, Ni2+ and Cu2+ are also adsorbed on the [MnO6] layers. These mechanisms of mineral formation and metal uptake are corroborated by data for other oceanic non-hydrothermal manganese nodules and crusts.

Environmental monitoring with river suspended matter: case study in the River Dalälven, central Sweden

Abstract Heavy metal concentrations are presented for suspended sediment from the River Dalalven, central Sweden. The river is contaminated by acid mine drainage and data from the most polluted tributary, Garpenbergsan, are also presented. Element/Al ratios in the suspended phase showed that K, Mg and Ti were mainly hosted in detrital particles together with a large fraction of Si. Between 50 and 60% of the load of Fe, Ca and Na were in non-detrital form. Less than 10% of the total load of suspended Mn and P were in a detrital form. The sediment in the River Dalalven is polluted by As, Cr, Cu, Hg, Ni, Pb and Zn. These elements, except Pb, showed an even stronger enrichment in the suspended phase. This indicated that between one third and one half of the suspended load was recirculated to the water column during sedimentation. Arsenic, Cr, Cu, Hg, Ni, Pb and Zn showed linear correlations with non-detrital Fe, close to the inflow of the polluted stream Garpenbergsan. Deposition of non-detrital Fe, Na, Cr, Cu and Ni in the sedimentation basins close to the river mouth reduced the suspended discharge of these elements to the Baltic Sea. However, the basins acted as sources for non-detrital suspended As, Hg, Pb and Zn during the studied period. The calculated net export, in a non-detrital form, for these elements was 141, 3.7,1100 and 7000 kg, respectively, as measured between May and October.

The hydrogeochemistry of the Kärkevagge Valley, Lapland, Sweden

The Kärkejokk (jokk = Lappish for brook) is rich in sulfate and calcium, both elements having been considered enigmatic. To resolve these problems we collected waters at 13 sites during 27 June to 1 September 1996. Nine sites were in the Kärkevagge, and the others in the drainage towards lake Torne Träsk. Rain waters were collected the same period. Conductivity, pH, and temperature were measured in the field, whereas salt load and the elements Na, K, Ca, Mg, S, Si, Fe, Al, Mn, Zn, Sr, and Ba were determined in the laboratory. Mixing models based on rain water and leaching products of the major bedrocks do not explain observed element patterns except in the lower parts of the jokk. However, oxidation of pyrite has formed acid, sulfate–rich solutions that released Ca and Mg from limestones, and Fe, Mn, Al, and Si, from black shales (Malmsten 1998; Malmsten et al. 2000). Conservative mixing models, using rain water, leached bedrock and pyrite, match the jokk waters quite well, and sulfur isotope data corroborate these findings. The nearby Låktajokk, and Vassijokk also contain much S. Where these waters debouch they may deposit Si, Al, and Ca, but only little S on various rocks. Total rock analyses, thermodynamic and X–ray data suggest that gypsum, barite, or alunite are not formed in major quantities. These models show that the hydrogeochemistry of the Kärkejokk may be less enigmatic than often assumed.

Late hydrothermal events at LÅngban – how many and how alkaline?

The Långban mines in south-central Sweden contain numerous mineral associations, many of them formed late at low temperatures and pressures Sjögren. (1910) speculated that these veins originated at widely different times, whereas Magnusson (1930) considered the whole ore deposition and subsequent mineralisations as a continuous event, except possibly for a late sulfide injection. In a discussion of the similar Franklin deposit, Frondel and Baum (1974) considered this sulfide emplacement to be a syngenetic process, largely being an analogue of how the Red Sea hot brine deposits formed (Bischoff 1969). Only a few of these problems can be touched on here, namely how many late hydrothermal events we may recognize in Långban and what pH-conditions controlled them. By tradition some of these veins have been referred to as ”late, reduced veins”. This is not an altogether ideal nomenclature, as shown below, but for convenience this praxis will be kept here. Aminoff (1918) was probably the first to make a more systematic identification of late mineral parageneses at Långban. He described four major associations, namely the:

Iron-cemented sediment on lower continental slope off Cape Hatteras

The textural, mineralogical, compositional and paleontological characteristics of an iron-cemented allochthonous sediment slab recovered from a zone of slumping between water depths of 2,100 and 2,350 m on the lower continental slope off Cape Hatteras are summarized. Results support interpretation of the sediment slab as the oxidized equivalent of pyrite-cemented Pleistocene to Recent sediment, an uncommon form of lithification in deep sea sediments. We propose that exposure of such slumped sediment slabs to seawater has produced an alteration sequence from pyrite-cement to iron oxide-cement. These observations extend the range of pyrite-cemented sediment initially reported from water depths between 4,770 and 4,950 m on the lower continental rise off Cape Hatteras.