The Palaeoproterozoic Skellefte Mining District is host to abundant ore deposits. Geological 3Dmodelling was performed using the gOcad software platform. Geological methods such as field mapping, structural analysis and facies analysis combined with geophysical techniques such as reflection seismic investigations, resistivity, magnetic, electromagnetic and gravimetric studies and analysis of potential field data provide a framework for the reconstruction of the crustal geometry and geological history of the district as a tool for modern ore exploration. Results will be furthermore utilized for kinematic 4-dimensional modelling

Four-dimensional geological modelling has been conducted in the Palaeoproterozoic Skellefte mining district. 3D-modelling of volcanic-hosted massive sulphide deposits and associated host-rocks has been carried out in multiple scales from deposit to regional scale and is based on a combination of geological and geophysical investigations. A conceptual model founded on unravelling the structural control on sedimentation, volcanism and mineralization and the subsequent deformation patterns, acts as a base for geological modelling. The final 3D-model provides a structural framework in which the mineralizations can be studied by improved understanding of the structural evolution in the mine areas, and by comparing the regional structural patterns versus the form and attitude of ore deposits. Additionally, uncertainty and prospectivity models were constructed showing the distribution of data and the potential of discovering new ore deposits. Subsequent 4D-modelling adds the time aspect to the 3D-models and aims at visualizing and understanding the geological history in the district and as a support for ore targeting. Moreover, adding geological time to the modelling helps gaining confidence about both the conceptual models and the 3D-models. The final 3D- and 4D-models provide a regional three-dimensional context for both industrial and academic activities in the Skellefte district, and aid the understanding of large-scale tectonic processes.

Geochemical investigations were carried out in the Gallivare area as a part of a larger project aiming to understand the crustal architecture of the region in 3D. Major igneous suites such as the Dundret and Vassaravaara intrusions with additional smaller mafic intrusions have been identified as key localities and investigated. Results indicate two distinct rock units. The first suite is assigned to ultramafic-mafic layered intrusions with a calc-alkaline to a more tholeiitic composition belonging to the Dundret and Vassaravaara intrusions. The second suite is mainly of mafic to intermediate composition with a clear ophitic texture. This paper investigate the source and origin of the key rock suites, playing a major role on the evolution of the Gallivare region, a region which is characterized by porphyry Cu, IOCG, and Al0 deposits including some of Europe's top producing Fe and Cu-Au-Ag (-Mo) mines.

The complex structural evolution within the VMS-hosting Skellefte district, Sweden, has been investigated to provide a solid structural framework for the known mineral deposits in the area. The area occurs in a transition zone between dominantly N-S to NNE-WSW striking structures in the north and approximately WNW-ESE oriented structural trends in the south. The presence of high-strain zones with both the above orientations in the Skellefte district allows constraining their mutual relationship, as well as their significance for the build-up of the Svecokarelian orogen at around 1.89 Ga and for the following tectonic overprint between 1.87-1.80 Ga. The methods used in this study include structural analysis complemented by potential field modelling and SIMS U-Pb geochronology on zircon. Based on the results of this study, the earliest deformation (D1) is constrained at 1.89–1.88 (1.87) Ga and tentatively attributed to crustal extension occurring synchronously with volcanism. Deposition of the Skellefte Group metavolcanic rocks is inferred to have occurred in a pull-apart basin developed due to dextral strike-slip shearing along approximately N-S striking regional-scale shear zones. Variations in the development of deformation fabric across the district indicate that the crust was divided into an upper, un-metamorphosed domain and a lower, strongly metamorphosed domain during D1. We further infer that the transition from the upper to lower crust was locally coupled with development of low-angle crustal-scale detachment zones during D1. The heterogenous crust was subsequently overprinted by transpressional deformation which may be explained by two alternative models. According to the first model, one single SSE-NNW transpressional event with distinct strain partitioning between the coaxially deformed upper crust and the non-coaxially deformed lower crust is largely responsible for the present-day structural geometry. A post-folding rhyolite dyke, here dated at 1871 ± 4 Ma, constrains the minimum age of this event (D2). The alternative model includes two separate transpressional events: a SW-NE one at (1.88-) 1.87 Ga, followed by SSE-NNW transpression at 1.86 Ga. Recognition of the early-orogenic detachment zones allow us to suggest that many of the major crustal-scale shear zones in the central Fennoscandian Shield have originated as 1.89-1.87 Ga crustal detachment zones, i.e. earlier than typically considered.

As a part of a 4D modeling project, two studies with different scopes were conducted in the central Skellefte district (CSD), northern Sweden. The aim of the studies is to create a basis for a better understanding of the spatial relationship between geological structures and mineralization and to construct a 3D and 4D geology model of the area.In the first study, we used geo-electrical data to define the geological structures at depth down to 430 m. The inversion of the resistivity and Induced Polarization (IP) data indicated a number of lithological contacts, which required further constraints prior to constructing the final 3D model.Hence we measured petrophysical properties including density, magnetic susceptibility, resistivity and IP of 154 samples, selected from drill-holes in vicinity of the resistivity/ IP profiles, to constrain the model. Forward resistivity models were then acquired using the resistivities measured on drillcores, to test the response of different geological scenarios in 3D after inversion. The gravity and magnetic response of the resistivity/ IP models was then calculated to constrain the models down to 1.5 km depth. The models were then modified, until reaching a consistency between geo-electrical and potential field data. The result indicated the possibility of three sulphide mineralization zones within the highly conductive parts at depth ≤ 500 m. The result also helped to determine the geometry of the contact between sedimentary rocks of the Vargfors basin and volcanic rocks of the Skellefte Group.In the second study, we tested geological models based on interpretation of reflection- seismic data using potential field data (down to 5 km depth) as well as electrical data (down to 430 m depth). The gravity and magnetic data especially benefitted the interpretation where no reflector is indicated, or poor-quality reflectors could not contribute to the understanding of major lithological contacts along the main faults and shear zones in the CSD. Moreover, the gravity and magnetic data, add significant information to reveal the spatial relationship between the Skellefte volcanics, metasedimentary rocks of the Vargfors Group and two intrusive structures of TIB gabbro-diorite and granitic rocks, which were poorly indicated on the reflection-seismic profiles. The results further indicate that joint interpretation of the integrated geophysical techniques can provide remarkable information regarding geometry of structures, which is a base for constructing 3D and 4D geological models.

The Skellefte mining district, northern Sweden, is regarded as one of the country’s richest mineral districts. Most of the outcropping deposits in this district or those deposits which are located at shallow depths (≤ 300 m) are likely to have already been discovered, which motivated the Swedish mining companies to expand their explorations at greater depths (e.g. ~5 km depth). Whereas previous explorations conducted in the central Skellefte district (CSD) contributed extensively to unveil VMS deposits, a comprehensive 3 and 4-dimensional geological model for ore exploration was lacking. The main aim of this study is thus to constrain and delineate geological structures at depth, using geophysical data for exploration of VMS deposits and create a well-constrained 3D geological model of the Skellefte district, northern Sweden. This is done in the framework of the project titled “4D-modeling of the mineral belts”. The deposits are volcanogenic massive sulphide (VMS) and the major deposits in the CSD contain commodities: Zn-Cu-Au-Ag and Pb. The deposits are generally characterized by higher magnetic susceptibility, density, chargeability and conductivity than many other rocks. This study thus includes magnetic, gravity and resistivity methods as main geophysical methods used. The results of seismic reflection data are integrated for joint geophysical interpretations and physical properties of the rocks, including density, magnetic susceptibility, resistivity and chargeability, have been measured.The thesis includes four studies: (i) local-scale study of the CSD using potential field, resistivity and induced polarization (IP) data, (ii) regional-scale potential field modeling to test seismic interpretations and improve the modeling of geological structures, (iii) understanding the geometry of the three early-orogenic intrusive bodies in the Holmträsk domain using potential field data, (iv) targeting VMS deposits using 2D and 3D resistivity/IP data in the CSD.Potential field modeling along three profiles where seismic data were previously acquired validated the interpretation of several key geological contacts indicated by seismic reflectors, and helped to delineate the geometry of the lithological units within the study area. The shallow and deep resistivity/IP investigation (down to ~2.2 km depth) proposed new possibilities for locating VMS deposits, and revealed a deeper image of the Vargfors basin. A good knowledge of the geometry of the Vargfors basin is crucial for exploration of the sulphide ores, which are believed to have formed along the bottom parts of the basin and upper parts of the underlying Skellefte Group rocks. The Maurliden deposits could be characterized by 3D resistivity/IP data and based on their geophysical signature several new targets for potential VMS deposits were identified.The results of joint geophysical and geological inter¬pretation presented in this study may be applied as a guide for future explorations in the CSD, e.g. when planning for, or expanding geo-physical surveys, creating detailed 3D geological models for exploration, and determining potential drilling locations. This reduces the exploration cost and increases the possibility for successful explorations.

The Skellefte district in northern Sweden is one of the most important mining districts in Europe hosting approximately 80 volcanic massive sulfide (VMS) deposits. Due to its economical importance, geological and geophysical studies were carried out in order to create an image of the geometry of the upper crustal structure and integral geological elements and to evaluate their relationship to mineral deposits. Consequently, seismic reflection data along three sub-parallel profiles were acquired during 2009–2010 to map the spatial relationships between the geological structures down to a depth of ~4.5 km. Although these seismic studies helped researchers understand the regional relationship between geologic units in the central Skellefte district (CSD), the seismic reflection data did not succeed entirely in mapping the lithological contacts in the area. In this study, themodel derived fromthe seismic reflection datawas examined by using 2.5D modeling of potential field data (down to a 5 km depth) constrained by physical properties of the rocks and surface geology.Moreover, we modeled gravity and magnetic data along the non-reflective or poorly reflective parts of the seismic profiles to identify major lithological contacts and shear zones in the CSD, which could not be modeled on the basis of the seismic reflection data. Gravity and magnetic data helped reveal the spatial relationship between the Skellefte volcanic rocks, Vargfors groupmeta-sedimentary rocks and two metaintrusive complexes.Results suggest amaximum depth extent of 2.1 kmfor the tectonic contact at the southern border of the Jörn granitoid. Furthermore, this north-dipping Skellefte–Jörn contact coincides closely with magnetic lows and gravity highs, which implies that the Jörn intrusive rocks have a greater thickness than the underlying basalt. Further to the NW, gravity and magnetic data suggest a depth extent of 2 km for the Gallejaur complex, which coincides with a set of gently dipping reflectors. In addition, this study supports previous concepts of fault geometries and fault patterns as a result of upper-crustal extension and subsequent inversion during crustal shortening. In the final model interpretations of the IP data were included, thus relating indications of mineralization to the geological structures.

Geoelectrical and induced polarization data from measurements along three profiles and from one 3D survey are acquired and processed in the central Skellefte District, northern Sweden. The data were collected during two field campaigns in 2009 and 2010 in order to delineate the structures related to volcanogenic massive sulphide deposits and to model lithological contacts down to a maximum depth of 1.5 km. The 2009 data were inverted previously, and their joint interpretation with potential field data indicated several anomalous zones. The 2010 data not only provide additional information from greater depths compared with the 2009 data but also cover a larger surface area. Several high-chargeability low-resistivity zones, interpreted as possible massive sulphide mineralization and associated hydrothermal alteration, are revealed. The 3D survey data provide a detailed high-resolution image of the top ∼450 m of the upper crust around the Maurliden East, North, and Central deposits. Several anomalies are interpreted as new potential prospects in the Maurliden area, which are mainly concentrated in the central conductive zone. In addition, the contact relationship between the major geological units, e.g., the contact between the Skellefte Group and the Jörn Intrusive Complex, is better understood with the help of 2010 deep-resistivity/chargeability data. The bottommost part of the Vargfors basin is imaged using the 2010 geoelectrical and induced polarization data down to ∼1-km depth.

Located in northern Sweden, the Skellefte mining district has been subject to several geological and geophysical investigations, as it is hosting abundant volcanic-hosted massive sulfide deposits. The importance of mineral exploration at greater depths in the Skellefte District has been increased since most of mineralization at shallow depths are already discovered and exploited. Therefore, geophysical methods become particularly important as they can improve our knowledge about spatial relationship between geological features at the depth. In the first part (local-scale) of this study, we used resistivity/IP data to map the subsurface geometry down to 430m. Furthermore, the results of the resistivity/IP studies were constrained with potential field data down to 1.5 km depth. In the second part (Regional-scale), potential field data were used to constrain the interpretation of the reflection-seismic data down to 5 km depth. The result from the first part indicated a good correlation between the initial resistivity model and the magnetic and gravity field calculated from that model. In Part II, the gravity and magnetic data were investigated to better understand the contact between the Skellefte Group,volcanic rocks and the Bothnian Basin sedimentary rocks. Furthermore the method was used to constrain the geometry of late-orogenic gabbro-diorite and granite intrusions which occur along inferred shear zones that are only poorly indicated, or not visible at all on the reflection-seismic profiles. As the main outcome, the proposed integrated 3D model of the central Skellefte District (CSD) revealed crucial information about the spatial relationship between key lithologies which will be further used to understand the evolution of CSD in the 4th dimension, time.

Multi-scale geophysical studies were conducted in the central Skellefte district (CSD) in order to delineate the geometry of the upper crust (down to maximum ∼ 4.5 km depth) for prospecting volcanic massive sulphide (VMS) mineralization. These geophysical investigations include potential field, resistivity/induced polarization (IP), reflection seismic and magnetotelluric (MT) data which were collected between 2009 and 2010. The interpretations were divided in two scales: (i) shallow (∼ 1.5 km) and (ii) deep (∼4.5 km). Physical properties of the rocks, including density, magnetic susceptibility, resistivity and chargeability, were also used to improve interpretations. The study result delineates the geometry of the upper crust in the CSD and new models were suggested based on new and joint geophysical interpretation which can benefit VMS prospecting in the area. The result also indicates that a strongly conductive zone detected by resistivity/IP data may have been missed using other geophysical data.

The central Skellefte district (CSD) is a part of a major ore-bearing district in northern Sweden. Studying the depth and patterns of the contact relationship between the two major stratigraphic units of the CSD, the Skellefte Group and the Vargfors Group, is a key issue to understand the geometry and structure of the area and to guide exploration of base metals. In this study, we interpret geoelectrical data collected along two profiles and magnetic and gravity data obtained from the database of the Swedish Geological Survey (SGU) and Boliden Mineral, to reveal contact relationship and depth extension of the major geological structures. Petrophysical analyses of the different lithologies were conducted on samples from the database of the SGU. Electric resistivity, induced polarization (IP), magnetic susceptibility and density were determined on 154 core samples representing the different lithologies of the area. The resistivity/IP data were acquired to define structural relations down to a maximum depth of ~ 430 m. The major contact between sediments of the Vargfors basin and volcanic rocks of the Skellefte Group were outlined from the inversion of the resistivity/IP sections, suggesting a synform boundary between the Vargfors Group and Skellefte Group. The contact relationship between the felsic and mafic volcanic rocks of the Skellefte Group is also understood with the help of the resistivity/IP data. The resistivity models were tested using the magnetic data and magnetic susceptibility inferred on the resistivity bodies. The result suggests a good correlation between the initial resistivity model and the magnetic and gravity field calculated from that model. The integration and interpretation of geological and geophysical data improved the basic understanding of the geometry of CSD. Based on previous geological investigations, the potential ore deposits are believed to be found along the volcano-sedimentary contact. The result from this study can thus be used for the base metal exploration, finding the locations of potential sulphide deposits and give a better understanding about spatial relationship between different geology structures in the CSD.

The VIRCOLA project addresses important challenges, which arise in cross-disciplinary research related to subsurface storage of CO2. The specific background for the VIRCOLA project is the research work performed in the SUCCESS centre (Subsurface CO2 storage - Critical Elements and Superior Strategy). One of the case studies in the SUCCESS centre is the Longyearbyen CO2 Lab in Svalbard. A key challenge in working with a large, multidisciplinary project such as SUCCESS is large amount of available data. It is also challenging to utilize and visualize the multi-scale and multimodal data types. Additionally, it is a challenge with regards to effective collaboration as researchers are located at different locations. Our approach involves three major components: the VIRCOLA data repository, a visualization platform for cross discipline research, and finally a remote collaboration platform to access to visualizations from anywhere. We demonstrated our approach for partner researchers. The result has been promising, as researchers were enthusiastic to apply our approach in their research within the center, and our test demonstrations were encouraging to our partners. It is our aim to adapt our approach on a national scale, i.e. in other large CO2 research projects on the Norwegian shelf.