Abstract Europe relies mainly on imports of critical raw materials (CRMs) for its industry, not least the vital ones for emerging green energy technologies. Among the main metal and mineral producers in Europe today, the Nordic countries (specifically, Greenland, Norway, Sweden and Finland) share a diverse geology with various deposit types formed over a long geological time span. This has led to large near-future potential with regard to CRM production. Based on current knowledge and datasets, we assess the Nordic geological potential for CRMs that are specifically relevant for green technologies, namely cobalt, graphite, hafnium, lithium, niobium, platinum-group metals, rare earth elements (REEs), silicon, tantalum, titanium and vanadium, describing the most important deposits, their setting and characteristics. Several Nordic CRM resources stand out in a European and even global context, such as the giant REE(–Nb–Ta–Hf) deposits in Greenland, while the REE–Nb–(Hf) deposits at Fen (Norway) and Norra Kärr (Sweden) are very significant for Europe; Finland is the only major cobalt producer, while Norway has very significant graphite and titanium resources and production. Furthermore, Sweden, Finland and Greenland have very large vanadium resources. In addition, we conclude that the Nordic research and exploration potential for most CRMs is large.
Graphite formation in the deep crust during granulite facies metamorphism is documented in the Proterozoic gneisses of the Lofoten–Vesterålen Complex, northern Norway. Graphite schist is hosted in banded gneisses dominated by orthopyroxene-bearing quartzofeldspathic gneiss, including marble, calcsilicate rocks and amphibolite. The schist has major graphite (<modality 39%), quartz, plagioclase, pyroxenes, biotite (Mg# = 0.67–0.91; Ti < 0.66 a.p.f.u.) and K-feldspar/perthite. Pyroxene is orthopyroxene (En69–74) and/or clinopyroxene (En33–53Fs1–14Wo44–53); graphite occurs in assemblage with metamorphic orthopyroxene. Phase diagram modelling (plagioclase + orthopyroxene (Mg#-ratio = 0.74) + biotite + quartz + rutile + ilmenite + graphite-assemblage) constrains pressure-temperature conditions of 810–835 °C and 0.73–0.77 GPa; Zr-in-rutile thermometry 726–854 °C. COH fluids stabilise graphite and orthopyroxene; the high Mg#-ratio of biotite and pyroxenes, and apatite Cl < 2 a.p.f.u., indicate the importance of fluids during metamorphism. Stable isotopic δ13Cgraphite in the graphite schist is −38 to −17‰; δ13Ccalcite of marbles +3‰ to +10‰. Samples with both graphite and calcite present give lighter values for δ13Ccalcite = −8.7‰ to −9.5‰ and heavier values for δ13Cgraphite = −11.5‰ to −8.9‰. δ18Ocalcite for marble shows lighter values, ranging from −15.4‰ to −7.5‰. We interpret the graphite origin as organic carbon accumulated in sediments, while isotopic exchange between graphite and calcite reflects metamorphic and hydrothermal re-equilibration.
are complex. With decreasing relative age these are: granitic dykes and net-veins, composite dykes, por phyritic microdiorite dykes, dolerite dykes and granophyre dykes. The granophyres have been dated by the Rb/Sr whole-rock method and yielded a 9 point isochron of 428 :t lOMa with an initial ratio of 0.70480 :t 0. 0003 and MSWD = 2. 0. From the aspect ratios of the dykes a model is proposed which suggests that the dykes were forrned with a magmatic overpressure of less than 90 MPa. This indicates that the source of magma was at a maximum depth of 36 km for the basic dykes and up to 15 km for the granophyres. Theoretical results indicate that a 2 m wide dolerite dyke in the Smola area solidified within less than about 70 days and a 10m wide granophyre within around 5 years. Emplacement of the dyke swarms resulted in about 35% crustal extension.
Abstract Strike, dip, and thickness were measured for 504 sheets (inclined sheets and dykes) in the 4–6 Ma old Hafnarfjall central volcano in southwest Iceland. The average dip of sheets is 65°, 80% are less than 1.2 m thick, and the thickness tends to decrease with decreasing dip. In 0.5 km long traverses perpendicular to the average strike of sheets, the percentage of sheets ranges from about 6 to 11. Of 140 chemically analysed sheets most are quartz-tholeiites; a few are intermediate or acid. The sheets are chemically more evolved than the host rock and were generated by a shallow crustal magma chamber at a mature stage of the central volcano, whereas the host rock was generated earlier before the chamber was established. Trace element results suggest that the sheet magmas evolved by low-pressure fractional crystallization as well as by mixing of primitive magmas and crustal melts. A model is proposed where most of the sheets are generated by a growing shallow magma chamber. As the chamber grows its shape changes, and so does the local stress field associated with it. Because the sheets follow the stress trajectories of the local stress field, the potential pathways of the sheets change with the growth of the chamber, which may explain the common occurrence of cross-cutting sheets. From the evolved chemistry of the sheets, as well as from the pattern of the stress trajectories, it is concluded that the bulk of the sheets were injected from the upper part of the shallow magma chamber.
Graphite is considered to be one of Europe’s most critical minerals. It is necessary for the transition from hydrocarbon fuel to electricity due to its use in batteries that power electronic devices and electric transport. In the past, high-quality exposed graphite was found in Norway without today’s advanced geophysical and geological methods. Norway is a key destination in Europe for graphite production. With an increasing demand for graphite, there have been efforts to systematically survey the country using modern geophysical and geological methods to find hidden graphite deposits. Among the various geophysical survey methods, electrical and electromagnetic (EM) methods are the first choice for the exploration of graphite due to the material’s high electrical conductivity. Airborne surveys are often used to cover a large area for a regional reconnaissance survey to locate the sites with potential mineral deposits before performing ground geophysical and geological surveys. Therefore, frequency-domain helicopter EM (HEM) and airborne magnetic surveys were performed in Northern Norway to locate interesting anomalies which were followed by ground surveys such as electrical resistivity tomography (ERT), charged-potential (CP), self-potential (SP), ground EM, and geological surveys. Some locations were also investigated with drilling and petrophysical core-sample analysis. In this paper, we present helicopter EM and magnetic data, 3D inversion of HEM data, and a successful ground follow-up survey result from the Vesterålen district in Northern Norway. The HEM survey identified previously known and new graphite occurrences, both partially exposed or buried, which were confirmed using ground surveys, drilling, and laboratory analysis of the samples.
This paper reviews graphite exploration in the Jennestad area, Nordland. As a result of helicopter aeromagnetic surveying and subsequent ground geophysics, mapping and trenching, some 30, variously sized bodies of graphite schist were identified. The graphite-bearing schist occurs associated with dolomite marbles, amphibolites and pyroxene gneisses, all of which are intruded by charnockites and granites. The graphite is coarse, fully ordered, crystalline and flaky. Grades up to 40% carbon were found. Gangue minerals in the ore are quartz, plagioclase, Kfeldspar, biotite and orthopyroxene. Some of the largest ore bodies contain about 250,000 tonnes each with an average grade of 20% carbon. Bench-scale beneficiation tests shown that the ore can be upgraded to a maximum grade of 97% C, with a recovery of 89%. It is believed that the graphite schists were originally sediments rich in organic matter which wase converted to graphite during granulite-facies metamorphism.
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