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| 2. |
- Ingri, Johan, et al.
(författare)
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Uptake of alkali and alkaline-earth elements on suspended iron and manganese in the Kalix River, northern Sweden
- 1994
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 58:24, s. 5433-5442
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Tidskriftsartikel (refereegranskat)abstract
- Scavenging of alkali and alkaline-earth elements by suspended Fe and Mn in the Kalix River, northern Sweden, has been studied for a period of seventeen months. More than 95% (by weight) of suspended nondetrital concentrations of Ca, Mg, and Sr are scavenged on suspended nondetrital Fe throughout all seasons. Barium is correlated to suspended Fe during winter, but during the summer a significant fraction of nondetrital Ba is associated with Mn-rich particles. Porewater profiles for Ca, Mg, and Sr are similar to the dissolved Fe profile, suggesting desorption from a Fe-rich carrier phase. Compared with the river water concentration, Ba is enriched twenty-five times in porewater and shows, together with Mn, a post-depositional subsurface maximum in the solid sediment. The alkali elements Na and K show a linear correlation to suspended nondetrital Fe during the winter. However, the summer concentrations cannot be explained by scavenging onto Fe alone, and sediment and porewater data show no clear association with Fe or Mn. The distribution coefficients for the alkaline-earth elements are two orders of magnitude larger than coefficients obtained for model Fe-oxyhydroxides. This suggests that surface complexation occurs via other functional groups and/or the alkaline-earths are more firmly bound to the natural Fe-rich phase.
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| 3. |
- Pontér, Christer, et al.
(författare)
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Geochemistry of manganese in the Kalix River, northern Sweden
- 1992
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 56:4, s. 1485-1494
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved and suspended Mn in the Kalix River, northern Sweden, were measured weekly over a period of eighteen months. During the same period four lakes in the Kalix catchment were sampled at their outlets and in vertical profiles within the lakes, together with a stream draining a series of mires with shallow lakes. Snow melting in mid-May increased the dissolved Mn concentration in the river tenfold, compared with a concentration of 5 μg L-1 during the winter discharge (January to April). We suggest that the increase was caused by Mn-rich mire water mixing with melting snow and being transported to the river. Large concentrations of dissolved Mn built up in the hypolimnion of the lakes studied during the icecovered period. Break-up of the ice and spring-overturn in June increased the dissolved Mn concentration tenfold in lake discharge and a concomitant peak in the dissolved Mn concentration was observed in the river. Lake-derived Mn was the dominant source for Mn in the river during this time. Suspended Mn in the river was hosted mainly in detrital particles during flood in May. In mid-June, non-detrital suspended Mn started to accumulate and reached a maximum in late July and early August. The Mn/Al ratio was 25 times higher during this period than during flood in May, suggesting the precipitation of an Mn-oxyhydroxide phase. The precipitation of the non-detrital Mn-rich phase was correlated in time with increased temperature, increased pH and increased concentration of suspended biogenic particles. The precipitation of dissolved Mn was biologically mediated. Sedimentation and mineralisation of the non-detrital Mn phase in river and lake sediments resulted in a steady increase of the dissolved Mn concentration in the river water during autumn.
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| 4. |
- Romer, Rolf L., et al.
(författare)
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Lead mobilization during tectonic reactivation of the western Baltic Shield
- 1993
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Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 57:11, s. 2555-2570
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Tidskriftsartikel (refereegranskat)abstract
- Lead isotope data from sulfide deposits of the western part of the Baltic Shield define mixing lines in the 206Pb 204Pb- 207Pb 204Pb diagram. Lead from two types of sulfide deposits have been investigated: 1. (1) Exhalative and volcanogenic deposits that are syngenetic with their host rocks 2. (2) vein deposits. The syngenetic deposits locally show a very wide range of lead isotopic compositions that reflect a variable addition of highly radiogenic lead, while the vein deposits, although they have radiogenic lead isotopic compositions, exhibit only limited isotopic variations. In different provinces of the shield, both types of deposits fall on the same lead mixing array. The slope of the lead mixing lines varies as a function of the age of basement rocks and the age of the tectonic event which produced the lead mobilization and therefore relates the source rock age with the age of lead mobilization. Calculated mixing ages fall into several short time periods that correspond either to orogenic events or to major phases of continental rifting. The orogenic events are the ca 360-430 Ma Caledonian, ca 900-1100 Ma Sveconorwegian, and the ca 1800-1900 Ma Svecofennian orogenic cycles. The rifting events correspond to the formation of the ca 280 Ma Oslo rift and the Ordovician (ca 450 Ma) graben system in the area of the present Gulf of Bothnia. Each mixing age indicates that lead was mobilized, probably as a consequence of mild thermal disturbances, and that the crust was permeable to lead migration. The data show that the geographic distribution of sulfide deposits with highly radiogenic lead isotopic compositions coincides with old graben systems, orogenic belts, and orogenic forelands on the Baltic Shield. The ages of vein deposits and their geographic distribution demonstrate multiple tectonic reactivation of the interior of the Baltic Shield in response to orogenic events at its margin.
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| 5. |
- Romer, Rolf L., et al.
(författare)
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U-Pb dating of columbites : a geochronologic tool to date magmatism and ore deposits
- 1992
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Ingår i: Geochimica et Cosmochimica Acta. - 0016-7037 .- 1872-9533. ; 56:5, s. 2137-2142
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Tidskriftsartikel (refereegranskat)abstract
- We have developed techniques for the U-Pb analysis of the mineral columbite [(Fe,Mn)(Ta,Nb)2O6], and report U-Pb ages obtained for three early Proterozoic columbites from the Baltic Shield of northern Sweden. The U-Pb ages of these columbites agree with other available geochronological data. U-Pb dating of columbite is therefore a potentially powerful tool in establishing reliable ages of pegmatites, alkaline and carbonatitic intrusions, and ore deposits of Sn, W, and REEs, all of which often contain columbite. Furthermore, columbite can be used to date peraluminous granites as it often occurs within Li-P-REE pegmatites associated with such granites.
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