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.

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.

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.

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.

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.

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.