Geological Survey of Sweden

About: Geological Survey of Sweden is a government organization based out in Uppsala, Sweden. It is known for research contribution in the topics: Metamorphism & Zircon. The organization has 316 authors who have published 671 publications receiving 18333 citations. The organization is also known as: Sveriges Geologiska Undersökning.

The Paragenesis of Swedish Glacial Clays

Abstract: The feldspars in Swedish glacial clays include K-feldspar, low albite and intermediate plagioclases, but not peristerites. The hydrolysis of K-feldspar leads to the formation of illite under glacial conditions of P, T and μmobile components; chlorite is the stable ferromagnesian mineral in the unweathered clays. Illite + albite + quartz represents a lower energy assemblage than K-feldspar + Na-montmorillonite + quartz.

Microfossils in the Quaternary Layers at Tofthög, Southern Scania

Abstract: The biostratigraphic study of Tofthog core is the first preliminary part of a more extensive litho- and biostratigraphic survey of the Quaternary layers in the Alnarp Valley. The material was analyzed for its content of pollen, spores, diatoms, silicoflagellates and other microfossils occurring in the pollen and diatom slides. The Tofthog core contains no organic sediments. All the microfossils noted are either reworked or allochthonous. The frequencies of pre-Quaternary (extinct) and Quaternary (extant) pollen show a distinct variation in different strata. According to Andersen (1965), the till with high content of Quaternary pollen is transported from the south or southeast and the tills with dominance of pre-Quaternary material from the north. The various pollen contents in the different till beds at Tofthog show that the lowest till has been transported from N and the middle till from S—SE. The upper till bed can be divided biostratigraphically into a lower part, transported from N and an upp...

40Ar–39Ar biotite age of a lamprophyre dyke and constraints on the timing of ductile deformation inside the Idefjorden terrane and along the Mylonite Zone, Sveconorwegian orogen, south-west Sweden

Abstract: A sharply cross-cutting lamprophyre dyke inside the Idefjorden terrane and along the Mylonite Zone in the Sveconorwegian orogen, Sweden, yields a plateau 40Ar–39Ar biotite age of 914.6 ± 1.2 Ma. This result confirms a published K–Ar age and is interpreted to record magmatic intrusion of the dykes. The lamprophyres are coeval to the similarly oriented but less potassic 916 ± 11 Ma noritic to anorthositic Hakefjorden Complex exposed west of the Gota Alv Shear Zone in the Idefjorden terrane. The lamprophyres are characterized by high magnetic susceptibility, chilled margins, biotite phenocrysts and deuteric alteration of the groundmass. They classify as kersantite and minette, and are interpreted to represent rare, minor explosive mantle-derived magmas, intruded along deep-reaching, east-west trending, extensional structures related to the waning stages of the Sveconorwegian orogeny. Since the host bedrock, at the current level of erosion, was responding to brittle deformation prior to the intrusion of the l...

Polyphase vein mineralization in the Fennoscandian Shield at Åkerlandet, Järvsand, and Laisvall along the erosional front of the Caledonian orogen, Sweden

Abstract: The Akerlandet, Jarvsand, and Laisvall deposits in Sweden are calcite-fluorite-sulfide vein deposits and occurrences located close to the current erosional front of the Caledonian orogen and hosted by crystalline basement rocks in the Fennoscandian Shield. At Laisvall, basement-hosted veinlets occur beneath Ediacaran to Cambrian sandstones that host a strata-bound Pb-Zn deposit. The mineralized fractures at Akerlandet and Jarvsand occur along fault systems oriented N–S to NNW–SSE. Veins or veinlets strike NNW–SSE and NW–SE at Akerlandet, NNE–SSW at Jarvsand, and NNW–SSE and NNE–SSW to NE–SW at Laisvall. At Akerlandet and Jarvsand, fractures acted as conduits for hydrothermal fluids of variable composition and formed during separate tectonic events. At Akerlandet, the fault zone with NNW–SSE strike shows kinematic indicators consistent with ~NE–SW bulk horizontal extension. At Jarvsand, the calcite-fluorite-galena veins formed along R-Riedel shears related to the host N–S to NNW–SSE fault system. The kinematic indicators are consistent with ~NW–SE bulk horizontal extension, similar to the extensional deformation during the later part of the Caledonian orogeny (Silurian to Devonian). At Akerlandet, adularia-quartz deposition was followed by sphalerite ± galena and finally by precipitation of fluorite and calcite. 40Ar-39Ar thermochronology of a single adularia sample did not yield a well-defined plateau age but the gas released at higher temperatures suggests an early Tonian (980 to 950 Ma) crystallization age, i.e., during the later part of the Sveconorwegian orogeny, although the data do not exclude other less likely interpretations. Previous fluid inclusion microthermometry and geochronological studies and new petrographic and geochemical results suggest that sphalerite ± galena mineralization formed from saline, relatively oxidizing, moderate-temperature, and slightly acidic hydrothermal fluids, either during the Ediacaran or the Middle Ordovician. Metals and H2S were derived from local basement rocks. Based on petrographic evidence, rare earth element composition, and S, C, and O isotope data, fluorite and calcite precipitated under near neutral and relatively reducing conditions. Occurrence of solid bitumen in veins at Akerlandet and C and O isotope data of calcite at Akerlandet and in the Laisvall basement veinlets suggest that the precipitation of calcite and fluorite was triggered by interaction of hot and evolved hydrothermal fluids (87Sr/86Sr = 0.718–0.732) with organic matter. Structural, petrographic, and geochemical data at Laisvall suggest that the basement structures hosting calcite-fluorite ± pyrite veinlets were utilized in the Middle Ordovician as the plumbing system for the oxidizing, slightly acidic, metal-bearing brines that caused the economic Pb-Zn mineralization in the overlying sandstones.