Book

GEOCHEMICAL ATLAS OF SWEDEN

Authors:

Abstract

The bedrock of Sweden has a long geological history and the oldest rocks formed 3,2 billion years ago. The Quaternary deposits covering the bedrock mostly consist of till and are younger, mainly formed c. 10 000 years ago during the latest glaciation. About 75% of Sweden’s land surface is covered by glacial till, the material on which this atlas is based. Through chemical analyses of the till we now have a better understanding of how the elements vary in the till in different parts of the country. These variations affect e.g. water quality and the health of humans and animals. Knowledge of the natural distribution of elements is of great value in mineral exploration but also in infrastructure planning and health and environmental work. We hope that this atlas will have a wide range of applications.
... There are 42 metallogenic sub-provinces in Sweden, defined on the basis of known mineral deposits, covering around 22% of the country (Hallberg et al., 2012;Andersson et al., 2014). Most sub-provinces have more than one of these deposit types and are grouped into four main mining districts: the Northern Norrbotten and Skellefte districts in Northern Sweden, the Caledonides along the border with Norway, and the Bergslagen area in south-Central Sweden ( Figs. 1 and 2). ...
... The recent glaciation episodes in the Northern Hemisphere have generated a complex array of proglacial and periglacial deposits including various till types, glacial outwash deposits and glaciolacustrine and glaciofluvial deposits with the dominant direction of glacial movement towards the SE (Andersson et al., 2014). Consequent dispersion and redeposition of geochemical and mineralogically anomalous materials in the 'down-ice' or glacial transportation direction . ...
... The geochemical dataset was derived from 2578 regional till samples sieved to <63 μm and analysed for a range of elements by inductively coupled plasma mass spectrometry following aqua regia digestion (Fig. 2.; Andersson et al., 2014). ...
Article
Parent lithology exerts a major influence on the associated regolith geochemistry and affects the setting of population or domain boundaries. In regional geochemical mapping and anomaly detection, a lack of samples pertaining to one or more key lithologies may results in interpolation errors. Such errors can be addressed via category-based fractal modelling to characterise different background and anomalous populations by taking both error propagation and geochemical data values into account. Such geochemical anomaly classification models have been developed using Monte Carlo simulation (MCSIM) within a given lithological domain to provide estimates of population breaks. Two types of category-based fractal models used are (i) related lithological groups representative samples where there is an adequate number of samples derived from a given lithological or geological domain, and (ii) related lithological groups whole samples and a group of Gaussian simulated samples regenerated based on the mean and standard deviation of the available samples per lithological group. Both models were applied to VMS-related element concentrations in the low-density till geochemical mapping of Sweden following centred log-ratio (clr) transformation. Compared with the concentration-area fractal model the category-based fractal models provided more reliable estimates for population thresholds and identification of anomalous classes.
... Most of Sweden is covered by regolith derived from recent glacial activity, and till is one of the more common sampling media used in regional geochemical exploration. The low-density, semi-regular spaced, multi-element national till geochemical dataset (Andersson et al., 2014;Fig. 1) used in this work has been previously used to examine the capacity of the more conventional fractal methods to help detect mineralized areas (Sadeghi, 2020;Sadeghi and Cohen, 2021). ...
... Sweden has 42 metallogenic sub-provinces and known mineral deposits (Hallberg et al., 2012; Andersson et al., 2014), including 16 containing significant base-metal mineral deposits (Cu, Pb, Zn, Ni and Co), 13 with ferrous metal deposits (Fe, Mn, Ti, V and Cr), and four associated with precious metals (Au, Ag and PGE). These sub-provinces may contain multiple deposit types. ...
Article
Various fractal models have been implemented to separate populations and characterize spatial distributions in geochemical data derived from regional mapping programs. This study compares the conventional number-size with a proposed concentration-distance from centroids (C-DC) fractal model to detect geochemically anomalous populations. These models have been applied to centered log-ratio transformed data of VMS-style mineralization related element concentrations in till from a low-density national survey conducted across Sweden. The C-DC model has been applied to the distance between till samples and centroids of geological sub-provinces containing a number of VMS-style deposits, and is derived from the concentration-distance (C-D) approach originally developed using a radial-density (R-D) model. The efficiencies of the models in detecting a multivariate geochemical response to known mineralization are compared using a variant of the overall accuracy matrix. The C-DC model provides accuracy of classification similar to the N-S model. Therefore, Monte Carlo simulation was applied to quantify uncertainties in setting of population thresholds using the two fractal models. It demonstrated greater efficiency of the C-DC model.
... In Lapland, anomalies 676 occur within the so called Gold Line and they follow Sn, Mo, Cu, Fe, U and precious metal 677 ore deposits with Au and Ag. The Bergslagen mining district comprises the most important W 678 (scheelite) ore deposits in Sweden, which are located mainly in skarn-limestone, commonly in 679 contact with Svecokarelian granitic rocks ( Andersson et al., 2014). 680 ...
Article
The demand for ‘high-tech’ element resources (e.g., rare earth elements, lithium, platinum group elements) has increased with their continued consumption in developed countries and the emergence of developing economies. To provide a sound knowledge base for future generations, it is necessary to identify the spatial distribution of critical elements at a broad-scale, and to delineate areas for follow-up surveys. Subsequently, this knowledge can be used to study possible environmental consequences of the increased use of these resources. In this paper, three critical industrial elements (Sb, W, Li) from low-sampling density geochemical mapping at the continental-scale are presented. The geochemical distribution and spatial patterns have been obtained from agricultural soil samples (Ap-horizon, 0–20 cm; N = 2108 samples) collected at a density of 1 site per 2500 km² and analysed by ICP-MS after a hot aqua regia digestion as part of the GEMAS (GEochemical Mapping of Agricultural and grazing land Soil) soil-mapping project in 33 European countries. Most of the geochemical maps show exclusively natural background element concentrations with minor, or without, anthropogenic influence. The maximum extent of the last glaciation is marked as a discrete element concentration break, and a distinct difference occurs in element concentration levels between the soil of northern and southern Europe, most likely an effect of soil genesis, age and weathering. The Sb, W and Li concentrations in soil provide a general overview of element spatial distribution in relation to complexity of the underlying bedrock and element mobility in the surface environment at the continental-scale. The chemical composition of agricultural soil represents largely the primary mineralogy of the source bedrock, the effects of pre- and post-depositional chemical weathering, formation of secondary products, such as clays, and element mobility, either by leaching or mineral sorting. Observed geochemical patterns of Li, W and Sb can be often linked with known mineralisation as recorded in the ProMine Mineral Database, where elements in question occur either as main or secondary resources. Anthropogenic impact has only been identified locally, predominantly in the vicinity of large urban agglomerations. Unexplained high element concentrations may potentially indicate new sources for high-tech elements and should be investigated at a more detailed scale.
Article
Full-text available
The inland area of southwestern Sweden is well known for its well-preserved archaeological animal and human remains dating back to the Mesolithic and Neolithic (10000–4000 and 4000–1700 BC). They allow application of multiple bioarchaeological methods, giving insights into various and complementary aspects of prehistoric human life, as well as economic and social structures. One important aspect concerns human mobility and its relation to social networks and to circulation of objects. Here, strontium isotope analysis plays a crucial role. The present study aims to construct a strontium isotope baseline of southwestern Sweden with considerably greater coverage and higher resolution than previously published data. As the region has been affected by glacial events, the relation between bedrock geology and isotope signals of the bioavailable strontium in such areas is given special attention. We determined strontium isotope ratios for 61 water and five archaeological animal samples, and combined the data with previous measurements of two water and 21 non-domestic faunal samples. The results reveal a complex pattern. Several areas with distinct baseline ranges can be distinguished, although with overlaps between some of them. Overall, the bioavailable strontium isotope signals mirror the basement geology of the region. The highest ratios occur in the geologically oldest eastern parts of the Precambrian terrain, while lower ratios are found in the western part, and the lowest ratios occur in the youngest Paleozoic areas. At the same time, there are minor deviations compared to the underlying bedrock, due to glacial transport, overlying sediments, and local intrusions of younger rocks. The background data set now available allows for more nuanced and detailed interpretations of human and animal mobility in the region, in particular by identification of subregions with differing strontium isotope ratios within the Precambrian province. Also, we can now identify long distance mobility with greater confidence.
Article
Full-text available
This comment highlights a whole series of datasets on thallium concentrations in the environment that were overlooked in the recent review by Karbowska, Environmental Monitoring and Assessment, 188, 640, 2016 in this journal. Geochemical surveys carried out over the last few decades all over the world at various scales and using different sampling media have reported the concentration of thallium (and dozens more elements) in tens of thousands of samples. These datasets provide a ‘real-world’ foundation upon which source apportionment investigations can be based, monitoring programs devised and modelling studies designed. Furthermore, this comment also draws attention to two global geochemical mapping initiatives that should be of interest to environmental scientists.