Characterization of altered mica from Sokli, northern Finland

Vermiculite is a mineral with many potential uses in various industrial areas, such as in insulation, horticulture, and environmental applications. The regolith of the Sokli carbonatite intrusion in northern Finland consists of weathered micas which reportedly contain vermiculite. The aim of the present study was to characterize the weathered mica in order to determine if the weathered regolith contains vermiculite. If so, the value of the apatite-rich Sokli intrusion may increase, because the vermiculite could be classified as an ore in Sokli. For the characterization, mica fractions were investigated using electron probe microanalysis (EPMA), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The EPMA results show that the potassium (K2O) content of the mica investigated varies between 6.20 and 0.31 wt.%. The XRD results provided evidence thatthe interlayer distances in the mica vary between 10.1 and 14.7 Å. The TGA shows that the dehydration of the samples varies between 6 and 12 wt.% for temperatures up to 170°C. Dehydroxylation takes place in three steps, as is characteristic for vermiculite. The results from this study revealed that mica in the weathered parts of the Sokli carbonatite is mostly vermiculite, and that the vermiculite was formed by the weathering of phlogopite. These results can be used to determine whether vermiculite is a possible future commodity at the Sokli carbonatite complex.</p

1.8 Ga magmatism in southern Finland: Strongly enriched mantle and juvenile crustal sources in a post-collisional setting

Whole-rock and isotope geochemistry of six 1.8 Ga post-kinematic intrusions, emplaced along the 1.9 Ga Southern Svecofennian Arc Complex (SSAC) and in the SW part of the Karelian Domain in Finland, was studied. The intrusive age [U-Pb secondary ion mass spectrometer (SIMS)] of one of these, the Petravaara Pluton, was determined as 1811 ± 6 Ma. Basic-intermediate rocks are alkali-rich (KO + NaO 4 wt.%) and typically shoshonitic, strongly enriched in large ion lithophile elements and light rare earth elements, but relatively depleted in high field strength elements and heavy rare earth elements. The enrichment is much higher than can be accounted for by crustal contamination and requires previously melt-depleted mantle sources, subjected to variable metasomatism by carbonate-rich fluids and sediment-derived melts. These sources are inferred to consist of phlogopite amphibole-bearing peridotites from depths below the spinel-garnet transition, as shown by the high Ce/Yb ratios. Sr/Sr(1.8 Ga) ratios in the range 0.7027-0.7031 and 'mildly depleted' ε(1.8 Ga) values (+0.1 to +1.4), with T values < 2.1 Ga, suggest that mantle enrichment was associated with the previous Svecofennian subduction-accretion process, when enriched sub-Svecofennian mantle sections developed, dominantly characterized by Sm/Nd ratios of 0.14-0.17. The associated granitoids are diversified. One group is marginally peraluminous, transitional between I (volcanic-arc) and S (syn-collisional) types, and was derived from mixed igneous and sedimentary, but juvenile Svecofennian source rocks, as supported by near-chondritic Nd(1.8 Ga) and somewhat elevated Sr/Sr(1.8 Ga). The other group is transitional between I and A (within-plate) types in character and had dominantly igneous protoliths. The whole-rock geochemistry and isotopes suggest that the compositional variation between 50 and 70 wt.% SiO2 may be explained by hybridization between strongly enriched mantle-derived magmas and anatectic granitic magmas from the juvenile Svecofennian crust. One intrusion in the east contains a significant portion of Archaean, mostly igneous protolithic material (ε(1.8 Ga) = -2.8 and ε(t) for zircons between +2.8 and -11.9, with an average of -4.9). The ∼1.8 Ga post-kinematic intrusions were emplaced within the SSAC subsequent to the continental collision with the Volgo-Sarmatia craton from the SE, during a shift from contraction to extension, that is, in a post-collisional setting. © 2010 Taylor & Francis.</p

Fast iron sulfide oxidation in a region of land uplift and artificial drainage

Godkänd; 2011; 20110916 (andbra

Impact of acid sulfate soil catchments on water quality in a lake in western Finland; trends and total metal load

Acid sulfate soils occur worldwide and can cause serious ecological damage by releasing acidity and toxic metals into watercourses. This study focused on short- and long-term changes to the water quality of a lake in western Finland. Here, a decline in water quality took place in the late 1960s. Since then, events concerning poor water quality have frequently occurred. The annual load of some potentially toxic metals varied from hundreds of kilograms to thousands of tons, depending on the metal. The proportion of low-order streams draining the nearest field to the lake is only 7% of the catchment area, while the share of the total metal load was estimated to be over 30%. This points to the importance of monitoring small coastal catchments. High runoff conditions were proven to be more important in terms of water quality than occasional summer droughts. During the past decade, acidic conditions have become more prolonged in the autumn, which is in line with a predicted scenario relating to climate change

An analytical procedure for determination of sulphur species and isotopes in boreal acid sulphate soils and sediments

An analytical scheme suitable for boreal acid sulphate (AS) soils and sediments was developed on the basis of existing methods. The presented procedure can be used to quantify and discriminate among acid volatile sulphide, cold chromium reducible sulphur, hot chromium reducible sulphur, elemental sulphur, sulphate sulphur, organic sulphur, total reducible sulphur and total sulphur. The sulphur fractions are recovered as either Ag2S or BaSO4 precipitates and can further be used for isotope analysis. Overlaps between sulphur species are common during speciation, and must be minimized. Some of these overlaps are caused by poor sampling and storage, inappropriate conditions during the distillation, or natural variations in the sample (e.g. Fe3+ interference and grain size). The procedural impact was determined by conducting tests on both artificial and natural samples containing one or several sulphur species. The method is applied on reduced sediment from an AS soil locality (Överpurmo) and a brackish lake (Larsmo Lake) in western Finland and the results, including S-isotopes, are discussed.

Alterations of insulin signalling in type 2 diabetes: A review of the current evidence from humans

International audienc

LITHOSPHERE 2022: TWELFTH SYMPOSIUM ON THE STRUCTURE, COMPOSITION AND EVOLUTION OF THE LITHOSPHERE: PROGRAMME AND EXTENDED ABSTRACTS

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Svecofennian intra-orogenic gabbroic magmatism: A case study from Turku, southwestern Finland

Using single-grain zircon U-Pb dating by LA-MC-ICPMS and whole-rock geochemistry, we have studied the Palaeoproterozoic gabbroic rocks from Moisio in southwest Finland. Three ages were obtained. The interpreted intrusion age is ~1.86 Ga, which places it in the 1.87–1.84 Ga intra-orogenic period of southern Svecofennia. The other ages, ~1.89 Ga and ~1.83 Ga, are inferred to be inherited and metamorphic ages, respectively. The K, LREE, LILE, Fe-, P-, Ti- and F-concentrations reveal two compositionally distinct groups: (i) an enriched monzogabbro group and (ii) a less enriched gabbro group. The composition of the monzogabbro group resembles the other intra-orogenic intrusions from southern Svecofennia, whereas the unrelated gabbro group is more comparable to the synorogenic rocks in the region. The magma source the monzogabbro experienced a subduction related carbonate metasomatism, induced by sediment subduction and subduction erosion. Evidently, the Moisio monzogabbro represent enriched, mantle derived magmatism in southern Svecofennia as a part of the intra-orogenic igneous activity. The intra-orogenic magmatism is considered to have conveyed considerable amounts of heat from the mantle into the crust contributing to subsequent lateorogenic high-grade metamorphism