Geological Survey of Finland
Recent publications
Mineral composition is a fundamental feature that affects the properties and functions of soil through physical, chemical and biological interactions. However, comprehensive knowledge on the mineralogy of agricultural topsoils of Finland has been lacking. In this study, the mineral composition of 120 soil samples included in the national monitoring of agricultural soils of Finland was determined using state-of-the-art quantitative x-ray diffraction analysis by a prior measured full pattern fitting methodology. Quartz, plagioclase and K-feldspar were found to be the dominant soil mineral components. Amphiboles and micas were also common, and several other mineral phases were detected in small quantities. The relative proportions of quartz and plagioclases increased and those of mica, goethite, disordered clay minerals, kaolin and amorphous inorganic components decreased as the soil particle size increased. Compositional statistical analysis discerned a positive association between the prevalence of 12 elements and organic matter and surface-active minerals (goethite, chlorite, disordered clays, kaolin and inorganic amorphous materials), whereas micas contributed to the prevalence of K. The present data agreed with general conceptions of Finnish soil mineralogy but revealed novel details in the mineral composition. The relationship observed between soil textural and mineral compositions supports the current texture-based soil classification system and recommendations.
The increasing concentrations of metallic Al or Al2O3 in secondary copper resources like electronic wastes motivate research into the slag chemistry of high-Al2O3 iron silicate slags for optimizing the industrial smelting process. In this study, the effect of Al2O3 in slag on the phase equilibria of the FeOx-SiO2-Al2O3 slag system was experimentally investigated at 1200 °C and pO2 of 10−8.6 atm. The high-temperature experiments were undertaken in silica and spinel crucibles in a controlled CO–CO2 gas atmosphere, followed by rapid quenching and Electron Probe Microanalysis. The equilibrium compositions of liquid slags in the tridymite primary phase field, spinel primary phase field, and the three-phase invariant point were determined. The 1200 °C isothermal section was constructed for the FeOx-SiO2-Al2O3 system, and the results showed that Al2O3 can dissolve in the liquid slags to a maximum concentration of 17 wt%. The present experimental results were compared with the predictions by MTDATA and FactSage. It was found that the present experimentally determined liquid domain agreed well with the calculations by FactSage except the invariant point. However, the present isotherm in the spinel primary phase field of spinel displayed lower Al2O3 concentrations. The present results help regulating fluxing strategies of FeOx-SiO2-Al2O3 slags and optimizing smelting operations of recycling high-alumina concentration copper resources.
The Keurusselkä structure is one of Finland's 12 meteorite impact structures—one of the world's oldest (1150 ± 10 Ma) and the largest of its kind in Finland. Findings of numerous well‐formed shatter cones in a wide area have helped define and prove Keurusselkä's impact origin. Keurusselkä is deeply eroded, making estimating its size challenging. Thus, various size ranges are based on the distribution of shatter cones. This study provides an overview of the earlier published studies in light of the unpublished data resulting from 2003 to 2019 field surveys. Two shatter cone outcrops 15 km from each other were sampled during a field survey in 2019. Thin section samples from these sites were studied with a polarizing microscope, and shock metamorphic features were identified and measured with the universal stage. We also compared topographic and bathymetric Lidar (light detection and ranging) data with the existing geophysical data and shatter cone occurrences. In situ outcrops—Metsomäki 9.6 km toward the W and Martinniemi 5.7 km toward SE from the crater's center—delimit the maximum radius of shatter cones found so far. Studies resulted in planar fractures parallel to (0001) in Metsomäki shatter cones. We determine the size of 37.5 km as the apparent diameter of the Keurusselkä impact structure, whereas the 25 km in diameter semicircular feature represents faulted rim structures.
Europe is mainly relying on imports of critical raw materials (CRM) 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 (here: 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 regards to CRM production. Based on current knowledge and datasets, we assess the Nordic geological potential for the CRMs which are specifically relevant for green technologies, namely: cobalt, graphite, hafnium, lithium, niobium, platinum-group metals, rare earth elements, 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 has the only major cobalt production, while Norway has very significant graphite and titanium resources and production. Furthermore, Sweden, Finland and Greenland have very large vanadium resources. Additionally, we conclude that the Nordic research and exploration potential for most CRMs is large.
The ongoing rapid increase in the integration of variable and uncertain renewable energy sources calls for enhancing the ways of providing flexibility to power grids. To this end, we propose an optimal approach for utilizing electric vehicle parking lots to provide flexibility at the distribution level. Accordingly, we present a day-ahead scheduling model for distribution system operators, where they can offer discounts on the network tariff to electric vehicle parking lot operators. This way, they will be encouraged to exploit the potential flexibility of electric vehicle batteries to assist in alleviating the steep ramps of system net-load. To determine the optimal discounts, the distribution system operator minimizes the network operating costs considering the network operational constraints, while the electric vehicle parking lot operators try to maximize their profits. Due to the contradictory objectives and decision hierarchy, the problem is an instance of Stackelberg games and can be formulated as a bi-level program, which is linearized and converted to a single-level mixed-integer linear program using strong-duality theorem and Karush–Kuhn–Tucker conditions. To validate the proposed model, comprehensive simulation studies are performed on a test distribution network. The simulation results show that implementing the model can reduce the peak-off-peak difference and peak-to-average ratio of the network net-load by up to 15% and 24%, respectively.
Sedimentary molybdenum (Mo) and uranium (U) enrichments are widely used to reconstruct changes in bottom water oxygen conditions in aquatic environments. Until now, most studies using Mo and U have focused on restricted suboxic-euxinic basins and continental margin oxygen minimum zones (OMZs), leaving mildly reducing and oxic (but eutrophic) coastal depositional environments vastly understudied. Currently, it is unknown: (1) to what extent Mo and U enrichment factors (Mo- and U-EFs) can accurately reconstruct oxygen conditions in coastal sites experiencing mild deoxygenation, and (2) to what degree secondary (depositional environmental) factors impact Mo- and U-EFs. Here we investigate 18 coastal sites with varying bottom water redox conditions, which we define by means of five “redox bins”, ranging from persistently oxic to persistently euxinic, from a variety of depositional environments. Our results demonstrate that Mo- and U-EF-based redox proxies and sedimentary Mo and U contents can be used to differentiate bottom water oxygen concentration among a range of modern coastal depositional environments. This is underpinned by the contrasting EFs of Mo and U along the redox gradient, which shows a substantial difference of Mo-EFs between redox bins 3–5 (ir/regularly suboxic – ir/regularly dysoxic – persistently oxic) and of U-EFs between redox bins 1–2 (persistently euxinic – ir/regularly euxinic). Surprisingly, we observe comparatively low redox proxy potential for U in environments of mild deoxygenation (redox bins 3–5). Further, we found that secondary factors can bias Mo-and U-EFs to such an extent that EFs do not reliably reflect bottom water redox conditions. We investigate the impact of limited Mo sedimentary sequestration in sulfidic depositional environments (i.e., the “basin reservoir effect”, equilibrium with FeMoS4), Fe/Mn-(oxy)(hydr)oxide “shuttling”, oxidative dissolution, the sulfate methane transition zone in the sediment, sedimentation rate, and the local Al background on Mo- and U-EFs.
Black shales host critical raw materials such as graphite and cobalt and occur in the vicinity of many types of sulphide deposits. We report the procedure for country-wide mapping of graphite- and sulphide-rich rocks and the chemical and petrophysical data of 319 samples we selected from sulphide occurrences and mines in Finland. Even though black shales are rarely outcropped in glaciated and deeply weathered terrains, they can be traced with geophysical surveys. In the Precambrian of Finland, where the metamorphic grade varies from greenschist to granulite facies, systematic airborne geophysical surveys revealed stratigraphy-related, coupled magnetic and electrically conductive patterns. Electrical conductivity was related to the graphite and sulphide contents, producing continuous and bending electromagnetic anomaly patterns. The magnetic anomalies, if present, resulted from ferrimagnetic monoclinic pyrrhotite. The petrophysical properties of black shales varied in our sample set. The densities were mainly between 2700 and 3000 kg/m³, with the mean density ~ 2800 kg/m³, where the amount of graphite had a reducing effect on density whereas sulphides increased it. The average magnetic susceptibilities were about 6000·10⁻⁶ (SI), but they showed wide variation, depending on the abundance of ferrimagnetic monoclinic pyrrhotite. The electrical conductivity of black shales appeared to be positively related to the abundance of monoclinic pyrrhotite. Conductivity variation, 1–10⁵ 1/Ωm was based on laboratory determinations of apparent resistivities. We correlated an airborne magnetic and electromagnetic survey with petrophysical and chemical data from altogether 319 drill core samples containing >1 % graphitic C and >1 % S. The samples were selected during 2009–2011 from 102 drill cores all over Finland except for the Talvivaara–Outokumpu region, which was studied during previous projects. The black-shale-hosted Talvivaara Ni–Zn–Co–Cu deposit is currently being mined. The maximum graphite concentration in the country-wide sample set was 34.3 %, and the median value was 5.7 %, a lower value than reported from the Talvivaara black-shale-hosted sulphide deposit (7.6 %). S, Co, Cu, Fe and Ni concentrations were also lower in our sample set on average than in the Talvivaara ore. However, the maximum concentration in our sample set was 397 mg/kg for Co, 0.36 % for Cu, 40.8 % for Fe and 0.28 % for Ni. The developed black shale mapping procedure can be directly applied in other parts of the world in terrains with greenschist to granulite facies regional metamorphism. Information on basic petrophysical properties, i.e., density, magnetic and electric properties, are needed to explain geophysical anomalies. If the metamorphic grade is lower than greenschist facies and there is no graphite, sulphides will increase the electromagnetic properties. If ferrimagnetic pyrrhotite exists, susceptibility increases, as well as remanence. The black shale database covering the whole of Finland is used not only in exploration and bedrock mapping, but also in regional planning and for environmental risk analyses, because sulphide-rich black shales may cause acid rock drainage when exposed to weathering and the quality of surface water and groundwater may suffer from black shale bedrock and glacial till. The scale limitations given by airborne geophysics may request detailed studies in selected sites.
Climate change is projected to cause brownification of some coastal seas due to increased runoff of terrestrially derived organic matter. We carried out a mesocosm experiment over 15 days to test the effect of this on the planktonic ecosystem. The experiment was set up in 2.2 m³ plastic bags moored outside the Tvärminne Zoological Station at the SW coast of Finland. We used four treatments, each with three replicates: control (Contr) without any manipulation; addition of a commercially available organic carbon additive called HuminFeed (Hum; 2 mg L⁻¹); addition of inorganic nutrients (Nutr; 5.7 µM NH4 and 0.65µM PO4); and a final treatment of combined Nutr and Hum (Nutr+Hum) additions. Water samples were taken daily, and measured variables included water transparency, organic and inorganic nutrient pools, chlorophyll a (Chla), primary and bacterial production and particle counts by flow cytometry.
Laser powder bed fusion (LPBF) has become an established method for manufacturing end-use metal components. Exploiting the geometric freedom of additive manufacturing (AM) offers broad possibilities for part optimization and enables performance enhancements across industry sectors. However, part shape and feature size have been found to locally affect residual stresses, melt pool cooling rates, microstructure, and thus the mechanical properties of components. Even though the mesoscale structure can locally induce microstructural changes, there are no prior studies on how it influences corrosion. Using AM-produced, optimized parts in critical applications necessitates a better understanding of their long-term performance. In this study, lattice structures were used to probe the influence of feature size and shape on corrosion susceptibility and its spatial localization. The susceptibility of submillimeter LPBF-fabricated 316 L stainless steel lattice structures to corrosion was investigated by conducting a 21-day immersion corrosion test in an aqueous 3.5 wt% NaCl solution. Schoen gyroid and Schwarz diamond triply periodic minimal surface lattices were manufactured with three unit cell sizes and wall thicknesses (0.867, 0.515, and 0.323 mm). The nominal surface and cross-sectional areas were the same for the two geometries. X-ray microcomputed tomography (microCT) scans before and after the corrosion test were compared for volumetric losses. In addition, the mechanical properties and microstructure of the samples were evaluated. As part of the study, a workflow to register, index, and analyze volumetric changes of consecutive microCT image stacks was developed. The method is fully reported and applicable to time-lapse studies with microCT. Three out of five of the 0.323 mm wall thickness lattices displayed visually aggressive pitting. Based on the microcomputed tomography data, the mass losses were localized either in the entrapped powder particles or partially melted surface globules. Corrosion did not occur in the dense base material. The total mass losses ranged from 8 to 19 mg. Despite visual indications to support a higher corrosion susceptibility for the smallest lattice sizes, the mass loss values did not confirm this conclusion. The tensile test results did not provide any clear indications of latent corrosion effects on mechanical properties.
The similarity of quarry stone with rapakivi stone of two buildings was assessed based on a 9-element fingerprint. The aim of the present case study was to assess the similarity between stones in buildings: the Kotka City Hall and the Orthodox Church of Kotka, and rocks in three Finnish quarries: Heponiemi, Jumalniemi and Metsola. Similarity assessment of building stones is necessary for effective and aesthetically-appropriate reconstruction. In the case of old buildings with stones of unknown origin, data on stone source quarries may have been lost over time. The present tool proposes a methodology to determine the most similar-to-the-origin stone and quarry for use in cultural heritage restoration. The tool in this study utilizes in-situ chemical analyses of the rock surface measured using a portable X-ray fluorescence (XRF) instrument together with modelling of the stone using multivariate statistical approaches (modified Soft Independent Modelling by Class Analogy, SIMCA) and machine learning (Naive Bayes Classification, NBC) to determine the fingerprint of the stone in the building and assess its similarity to quarry rock data. The proposed methodology for identification of stone origin was utilised in a case study of rapakivi from the Kotka area in Finland.
As the electrification sector expands rapidly, the demand for metals used in batteries is increasing significantly. New approaches for lithium-ion battery (LIB) recycling have to be investigated and new technologies developed in order to secure the future supply of battery metals (i.e., lithium, cobalt, nickel). In this work, the possibility of integrating LIB recycling with secondary copper smelting was further investigated. The time-dependent behavior of battery metals (Li, Co, Ni, Mn) in simulated secondary copper smelting conditions was investigated for the first time. In the study, copper alloy was used as a medium for collecting valuable metals and the distribution coefficients of these metals between copper alloy and slag were used for evaluating the recycling efficiencies. The determined distribution coefficients follow the order Ni >> Co >> Mn > Li throughout the time range investigated. In our study, the evolution of phases and their chemical composition were investigated in laboratory-scale experiments under reducing conditions of oxygen partial pressure p(O2) = 10^10 atm, at 1300 C. The results showed that already after 1 h holding time, the major elements were in equilibrium. However, based on the microstructural observations and trace elements distributions, the required full equilibration time for the system was determined to be 16 h.
Methane is a powerful greenhouse gas, of which most is produced by microorganisms in a process called methanogenesis. One environment where methanogenic microorganisms occur is the deep biosphere. The deep biosphere environment comprises a variety of ecosystem settings; marine habitats such as subseafloor sediments, rock pore volumes within subseafloor basalts, and terrestrial settings such as sedimentary rocks and crystalline bedrock fracture networks. Microbial methane formed in these environments influence the biological, chemical, and geological cycles of the upper crust, and may seep out of the deep into the atmosphere. This review focuses on the process of microbial methanogenesis and methane oxidation in the relatively underexplored deep crystalline-bedrock hosted subsurface, as several works in recent years have shown that microbial production and consumption occur in this energy-poor rock-fracture-hosted environment. These recent findings are summarized along with techniques to study the source and origins of methane in the terrestrial crust. Future prospects for exploration of these processes are proposed to combine geochemical and microbial techniques to determine whether microbial methanogenesis is a ubiquitous phenomenon in the crystalline crust across space and time. This will aid in determining whether microbial methane in the globally vast deep rock-hosted biosphere environment is a significant contributor to the global methane reservoir.
In this work, pyrometallurgical treatment of non-ferrous iron residue was studied. This approach aimed to recover the valuable metals and convert the residue into reusable benign slag using hydrogen as a non-fossil reducing agent. The pyrometallurgical treatment for this type of residue involves pretreatment prior to two stages, oxidation and reduction. Hydrogen was employed as a reducing agent in slag cleaning. The reduction tests were performed at temperatures of 1200 °C, 1250 °C, and 1300 °C using H 2 and N 2 gases to form the reducing gas atmosphere. The results show that H 2 is an effective reductant because reduction proceeded rapidly, forming speiss droplets within the slag already after 10 minutes. The laboratory-scale experiments suggest that slags or other residues obtained from metallurgical processes can be further cleaned in a fuming process using hydrogen and its mixtures to obtain environmentally friendly cleaner slag with respect of volatile metals. The results also show that one can tune the reduction and control the formation of metallic iron during the process. Thermodynamic modeling was also performed to simulate the fuming stage, i.e ., reduction of the slag. Metal alloy formation as well as elemental distributions between metal and slag were studied, and results from thermodynamic modeling agree well with experimental results.
This paper presents an original approach for the evaluation of reliability of active distribution networks with unknown topology. Built upon novel reformulations of conventional definitions for distribution reliability indices, the dependence of system-oriented reliability metrics on network topology is explicitly formulated using a set of mixed-integer linear expressions. Unlike previously reported works also modeling mathematically the relationship between reliability assessment and network topology, the proposed approach allows considering the impact of distributed generation (DG) while accounting for switching interruptions. Moreover, for the first time in the emerging closely related literature, the nonlinearity and nonconvexity of the customer average interruption duration index are precisely characterized. The proposed mixed-integer linear model is suitable for various distribution optimization problems in which the operational topology of the network is not specified a priori. Aiming to exemplify its potential applicability, the proposed formulation is incorporated into a distribution reconfiguration optimization problem. The effectiveness and practicality of the proposed approach are numerically illustrated using various test networks.
The Optically Stimulated Luminescence (OSL) age database of Finland was established, and it includes all of the published OSL age results from different sediment sequences in Finland. The OSL database includes ~180 published OSL ages ranging from 235,000 years to 300 years; that is, from the Middle Saalian interstadial to the present. Two statistical clustering methods, K-means and model-based clustering with the package mclust, were used to analyze the internal structure of the assembled OSL data. The results of these analyses were also compared to the established Northwest European (Fennoscandian) chronostratigraphical stages. When the data were analyzed by the K-means method, the “right” number of clusters (K) was seven. The model-based clustering method (K = five) created bigger clusters for the youngest and the oldest ages compared to the K-means clusters. Both methods show that the ages followed the increasing trend from the youngest to the oldest, and the standard error of ages was constantly increasing except in the age group 70–115 ka, where the standard errors were exceptionally high. Seven clusters obtained from the age data corresponded relatively well with the number of stratigraphically established interglacials and interstadials in the late Middle and Late Pleistocene in Fennoscandia. The exceptionally large standard error of ages in the Early Weichselian age group 70–115 ka might result from mixing of heterogeneous and poorly or partly bleached mineral material from both Eemian and Early Weichselian sediment layers. The OSL-dated Middle Saalian interstadial sediments in the data support a strong stadial and interstadial variation also before the Late Pleistocene.
This study investigated the behavior of 87Sr/86Sr, δ7Li and δ34S in the STE and three seafloor pockmarks with different degrees of groundwater influence, as constrained based on δ2H and δ18O, at the Hanko SGD site in Finland, in the northern Baltic Sea. These data were supplemented by groundwater and seawater measurements.
Mineral exploration is an industry of uncertainties. Only 0,1% of exploration projects become mines, as the volume, content, and quality of a deposit all must be economically justifiable to find funding in the global financial market. However, the business risk of mineral exploration is not limited to geotechnical and financial risks, as social aspects are now considered the biggest risk facing the industry. Here, we identify three social aspects of business risk that may challenge the industry: political, reputational, and local acceptability. Political risk arises when sectoral authorities and the related legislation come into conflict, such as mineral versus environmental legislation. Reputational risk lies in the relationship between a company’s past and current operations in combination with the legitimacy of the entire industry. Local acceptability risk parallels the social license to operate, with poor corporate conduct, competition with other livelihoods, intrusion into culturally sensitive areas, and local values critical of mining all potentially evoking resistance. Companies must be aware not only of the nuances of each social aspect but also of the interplay between them to understand the full scale and scope of the business risks associated with exploration.
Precambrian greenstone belts are prospective terrains for orogenic Au deposits worldwide, but the sources of Au, base metals, metalloids, and ligands enriched within the deposits are still debated. Metamorphic devolatilization is a key mechanism for generating Au-rich hydrothermal fluids, but the respective role of the metavolcanic and metasedimentary rocks present within these belts in releasing ore-forming elements is still not fully understood. The Central Lapland Greenstone Belt (CLGB), Finland, one of the largest Paleoproterozoic greenstone belts, hosts numerous orogenic Au deposits and is composed of variably metamorphosed volcanic and sedimentary rocks. Characterization of element behavior during prograde metamorphism highlights that (1) metavolcanic rocks release significant Au, As, Sn, Te, and possibly S; (2) metasedimentary rocks release significant S, C, Cu, As, Se, Mo, Sn, Sb, Te, and U, but limited Au; and (3) metakomatiite releases C and possibly Au. Throughout the CLGB metamorphic evolution, two main stages are identified for metal mobilization: (1) prograde metamorphism at ~ 1.92–1.86 Ga, promoting the formation of typical orogenic Au deposits and (2) late orogenic evolution between ~ 1.83 and 1.76 Ga, promoting the formation of both typical and atypical orogenic Au deposits. The complex lithologic diversity, tectonic evolution, and metamorphic history of the CLGB highlight that metal mobilization can occur at different stages of an orogenic cycle and from different sources, stressing the necessity to consider the complete dynamic and long-lasting evolution of orogenic belts when investigating the source of Au, ligands, metals, and metalloids in orogenic Au deposits.
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