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  • 251.
    Tavakoli, Saman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Bauer, Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Rasmussen, Thorkild Maack
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Weihed, Pär
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Deep massive sulphide exploration using 2D and 3D geoelectrical and induced polarization data in Skellefte mining district, northern Sweden2016In: Geophysical Prospecting, ISSN 0016-8025, E-ISSN 1365-2478, Vol. 64, no 6, p. 1602-1619Article in journal (Refereed)
    Abstract [en]

    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.

  • 252.
    Tavakoli, Saman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Bauer, Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Skyttä, Pietari
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Thunehed, Hans
    Geovista AB.
    Weihed, Pär
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Skellefte mining district in 3D: results from integrated interpretation of potential field, resistivity/IP and reflection-seismic data2012Conference paper (Refereed)
    Abstract [en]

    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.

  • 253.
    Tavakoli, Saman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Dehghannejad, Mahdieh
    Department of Earth Sciences, Division of Geophysics, Uppsala University .
    de los Ángeles García Juanatey, María
    Department of Earth Sciences, Division of Geophysics, Uppsala University .
    Bauer, Tobias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Weihed, Pär
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Elming, Sten-Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Potential Field, Geoelectrical and Reflection Seismic Investigations for Massive Sulphide Exploration in the Skellefte Mining District, Northern Sweden2016In: Acta Geophysica, ISSN 1895-6572, E-ISSN 1895-7455, Vol. 64, no 6, p. 2171-2199Article in journal (Refereed)
    Abstract [en]

    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.

  • 254.
    Tavakoli, Saman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Thunehed, Hans
    Geovista AB.
    3D inversion of the resistivity \ IP data acquired in Skellefte District, Northern Sweden, constrained with the resistivity measurement of the samples in the lab2011Conference paper (Refereed)
  • 255.
    Tavakoli, Saman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Thunehed, Hans
    Geovista AB.
    Geophysical modelling of the central Skellefte district, Northern Sweden: an integrated model based on the electrical, potential field and petrophysical data2012In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 82, p. 84-100Article in journal (Refereed)
    Abstract [en]

    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.

  • 256.
    Tavakoli, Saman
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Langeland, Tor
    Christian Michelsen Research AS (CMR).
    VIRCOLA: A tool for visualization and cross-discipline collaboration related to CO2 storage2014In: Fourth EAGE CO2 Geological Storage Workshop: Demonstrating storage integrity and building confidence in CCS, European Association of Geoscientists and Engineers, EAGE , 2014, p. 270-274, article id 107367Conference paper (Refereed)
    Abstract [en]

    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.

  • 257.
    Tavakoli, Saman
    et al.
    Christian Michelsen Research AS (CMR).
    Midttømme, Kirsti
    Christian Michelsen Research AS, Bergen.
    Hellevang, Helge
    Oslo University.
    Braathen, Alvar
    Oslo University.
    Synergy Between CO2 Storage and Utilization of Geothermal Energy: A case study from Longyearbyen, Svalbard2013Conference paper (Refereed)
  • 258.
    Thunehed, Hans
    Luleå tekniska universitet.
    Interpretqtion of deep electrical soundings and gravity data from some granites in northern Swedena1993In: Abstracts of lectures and posters: 21:a Nordiska geologiska vintermötet 10-13 Januari 1994 Luleå ; / [ed] Jan-Anders Perdahl, Luleå: Högskolan i Luleå , 1993, p. 214-Conference paper (Other academic)
  • 259.
    Thunehed, Hans
    Luleå tekniska universitet.
    Mapping and characterisation of Swedish bedrock by DC resistivity and transient-field electromagnetic measurement2000Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    DC electrical and electromagnetic methods have been used for a long time to detect and characterise fracture zones in site investigations and other engineering projects. However, the methods have not been used very much in basic geological mapping of crystalline rock on a regional to semi-regional scale. One reason for this is that measurements with traditional instrument set-ups used, for example, in ore and water prospecting are quite time- consuming. Three alternative methods for DC resistivity measurements are presented in this thesis. Vertical soundings can be performed efficiently with a modification of the traditional Schlumberger-array and large areas can be covered quickly with gradient array measurements. Resistivity anisotropy can be estimated with the new so called x-configuration. Nine electrodes, arranged in such a way that they form the letter x, are connected to an instrument in the centre. The apparent resistivity and apparent anisotropy can be found by least-squares fitting using different combinations of current and potential electrodes. Resistivity measurements using the new procedures have been performed in a number of areas. Systematic differences in resistivity were observed between different rock types indicating different intensities of fracturing. Marine volcanics for example have lower resistivity than terrestrial volcanics in the Arvidsjaur area. This means that it is possible to use resistivity measurements to characterise rock types and to detect boundaries between rocks of different character. The anisotropy was found to coincide with the foliation or bedding direction of the rock. Deep electrical soundings were performed in four areas in northern Sweden. The depth of investigation was several kilometres. The electric resistivity of the near-surface rocks was determined and their depth extent was estimated in three of the areas. A large lateral anomaly probably caused by marine volcanics was found in the fourth area. Transient-field electromagnetic (TEM) sounding is a method that has been used in mapping of sedimentary basins, geothermal exploration etc. The fundamental theory of TEM soundings and the processing of TEM sounding data are described in the thesis followed by examples of TEM soundings on crystalline bedrock. It is necessary to use large transmitter moments when measurements are made on highly resistive rock due to the weak secondary field. Bulk resistivity estimates made with DC measurements and TEM soundings were consistent in the Revsund granite area. TEM soundings offer a possibility to make bulk resistivity determinations to large depths in crystalline bedrock without the need for large transmitter-receiver separations. Fracture density and pore-water salinity are two important factors in the choice of a suitable location for a repository for highly active nuclear waste. A case history is presented where DC resistivity measurements were used in combination with TEM soundings in order to gain knowledge about the above mentioned factors. Two different types of granite were investigated and the resistivity of the younger Götemar granite was found to be around five times higher than the resistivity of the Småland granite, indicating a considerably lower fracture density in the former. The depth to saline groundwater was determined primarily with the TEM soundings and good agreement was found with data from deep drillholes.

  • 260.
    Thunehed, Hans
    Luleå tekniska universitet.
    Model interpretation of transient EM-data from the Lainijaur nickel-deposit1985In: Vol. 23, no 3, p. 417-418Article in journal (Other academic)
  • 261.
    Thunehed, Hans
    Luleå tekniska universitet.
    Two topics related to interpretation of transient electromagnetic measurements1997Licentiate thesis, monograph (Other academic)
  • 262.
    Thunehed, Hans
    et al.
    Luleå University of Technology.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pesonen, Lauri J
    The Lycksele Structure in northern Sweden: result of an impact?2000In: Large meteorite impacts and planetary evolution II, Boulder, Colo: Geological Society of America, 2000, p. 125-30Chapter in book (Other academic)
    Abstract [en]

    The Lycksele structure in northern Sweden is a large circular structure with a diameter of approximately 130 km. The structure has been defined from a combined analysis of topography, gravity, and magnetic data and is characterized by a circular system of faults, arc-shaped contacts between rocks, a quasi-circular system of downfaulted lowdensity granitic rocks, and an uplift of high-density rocks in the center. On the basis of ages of granite intrusions and a thrust zone that is cut by faults of the ring, together with paleomagnetic data, the age of the structure is between 1.80 and 1.26 Ga. The Bouguer gravity anomaly is similar to that associated with other known large impact structures on Earth. The rim of the structure, defined from the gravity gradients, magnetic data, and topography, is not restricted to specific rock types but cuts regional geologic structures as well as smaller intrusions, which may be expected for an impact structure in Precambrian deformed target rocks. Therefore, an impact origin seems most plausible for this structure, but to confirm this idea we need identifications of shock metamorphic features in the rocks.

  • 263.
    Tohver, E.
    et al.
    Universidade de Sao Paulo, Instituto de Geociencias.
    Filho, M. d'Agrella
    Universidade de Sao Paulo, Instituto de Geociencias.
    Santos, J. Orestes
    Geological Survey of Brazil (CPRM).
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Trindade, R.I.
    Universidade de Sao Paulo, Instituto de Geociencias.
    Teixeira, W.
    Universidade de Sao Paulo, Instituto de Geociencias.
    Paleomagnetic evidence for a transpressional Grenville Orogen: sinistral offsets between Amazonia and Laurentia point to an evolving Rodinia2005In: EOS: Transactions, ISSN 0096-3941, E-ISSN 2324-9250, Vol. 86, no 52 Suppl, article id GP33A-0091Article in journal (Other academic)
    Abstract [en]

    We report three new paleomagnetic poles from the Amazon craton for the Meso/Neoproterozoic Grenvillian interval, a period notable for the eponymous continental collision that affected the eastern margin of Laurentia. The poles were derived from study of ca.1230 Ma mafic sills (Figueira Branca -V 40Ar/39Ar biotite), the 1149 , b7 Ma sediments of the Aguapeí Gp. (U-Pb SHRIMP analysis of authigenic xenotime) and the ca.980 Ma basaltic dykes and flat-lying flows (40Ar/39Ar biotite) that intrude and overlie the Aguapeí Gp. sediments. These new data define a skeletal apparent polar wander path marked by a counterclockwise loop, similar to that observed for North America and Baltica. A pole-by-pole comparison of the Amazon and North American data demonstrates the evolving paleogeographic affinity of these two continents, marked by the large-scale strike-slip movement of Amazonia relative to Laurentia. The 3000 km of sinistral offset between these two continents is substantiated by a 200 Ma record of sinistral transpression recorded in the 1.2-1.15 Ga deformation of basement rocks of the Amazon craton, the 1.1 Ga Nova Brasil\^{a}ndia belt, and the 1.05-1.0 Ga Sunsas belt of eastern Bolivia. Our observations suggest that transpressional collision of the Amazon craton and Laurentia was responsible for the bulk of Grenvillian deformation, as opposed to the multiple continents required by other Rodinia models.

  • 264.
    Torikka, Niklas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    3D Modelling of TEM Data: from Rajapalot Gold-Cobalt prospect, northern Finland2019Independent thesis Advanced level (professional degree), 300 HE creditsStudent thesis
    Abstract [en]

    The Rajapalot gold-cobalt project in northern Finland is an exciting, relatively new discovery, still being explored with hopes to start mining in the future. The area was found by a IP/Resistivity survey in 2013. Extensive geophysical follow-up surveys have delineated several electromagnetic targets, one of which, named Raja, is the target anomaly this master thesis is built upon. A TEM survey was carried out during late August to early September 2018. The data collected was analyzed, processed and later modelled in Maxwell using Leroi, a CSIRO module. Three separate models are produced with one, two, and three plates respectively. The result is compared to existing VTEM and resistivity models.

  • 265.
    Ubieta, Karla
    Luleå tekniska universitet.
    Geological structures at the Southern edge of the Chortis Crustal Block, Nicaragua: a geophysical analysis1995Licentiate thesis, monograph (Other academic)
  • 266.
    Vallejos, Luis E. Santamaria
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Three-dimensional analysis of aeromagnetic and gravimetric data of sedimentary basins from Panama, Central America2008Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The knowledge of the geology of the sedimentary basins from the Gulf of Panama is still quite limited. There is a lack of data from the basin geometry, the thickness, the continuity and connection between the basins, and from the characteristics of the crystalline basement rocks beneath the sedimentary basins. Geological maps have been published without evidence from geophysical studies; i.e. marine faults patters are showed only as the continuation of fault pattern on land and in some cases faults are showed only to adjust geodynamics models. In the marines areas the geophysical surveys so far carried out, like seismic reflection and well logging, have not given information about the nature of and depth to the crystalline basement rock and interpretations of aeromagnetic and gravity data are still missing. Many of the geophysical surveys like aeromagnetic and marine gravity data have been published as contour maps. However, different data processing techniques and various references levels have been used, which do not permit an integral regional analysis. Here we present composite regional aeromagnetic and gravity maps and integral interpretations with reference to source parameters such as; depths to the top of basement rock, faults patters, locations of magnetic boundaries, susceptibility contrasts, geometry and connection between the basins. The interpretations are based on regional aeromagnetic maps and on marine and land gravity data compiled from several sources and integrated with reference to a fixed level. Various techniques have been applied for the interpretation e.g. enhancement of the aeromagnetic anomalies maps by sun shading technique, applying band pass filtering and upward analytic continuation. Maps have also been transformed into images called 3D analytic signal amplitude and local wave number maps. The depth estimates resulting from the analyses of these maps are compared and the location of interpreted contacts are combined into a map showing the dip direction for contacts. The Bouguer gravity data from the Gulf of Panama are transformed into a residual anomaly map using a filtering technique. This residual anomaly map have been analyzed in order to estimate depths to the top of the basement rocks.

  • 267.
    Villain, Lucile
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Sundström, Nils
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Perttu, Nils
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Evaluation of the effectiveness of backfilling and sealing at an open-pit mine using ground penetrating radar and geoelectrical surveys, Kimheden, northern Sweden2014In: Environmental Earth Sciences, ISSN 1866-6280, E-ISSN 1866-6299, Vol. 73, no 8, p. 4495-4509Article in journal (Refereed)
    Abstract [en]

    At Kimheden, a small copper mine in northern Sweden, reclamation of the two open pits was investigated using ground penetrating radar and geoelectrical multiple-gradient array measurements. The pits had been backfilled with waste rock, with a dry cover being applied on top in 1996 in order to reduce the influx of oxygen to the sulphidic mine waste and the subsequent production of acid mine drainage. The dry cover consists of a sealing layer of clayey till and a protective layer of unsorted till. As geochemical sampling in the drainage from the pits had previously revealed the continued release of contaminating oxidation products, the purpose of the geophysical survey undertaken in 2010 was to identify deficiencies in the cover or other pathways for oxygen to reach the waste rock. The radar images did not reveal any damage in the sealing layer but risks of deterioration of the cover in the long term were identified with both the radar and geoelectrical data. The radar localised regions of thinner protective layer where the sealing layer could be exposed to frost action. The geoelectrical measurements indicated the existence of seepage through the dry cover that presented a risk of erosion of the sealing layer. 2-D inversion of geoelectrical data also imaged some pathways of groundwater around the main pit. The results from the geophysical investigations were used together with other site data in order to show that both deficiencies in the cover and superficial fractures in the pit walls may explain an ongoing influx of oxygen to the mine waste.

  • 268.
    Villain, Lucile
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    sundström, Nils
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Perttu, Nils
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Öhlander, Björn
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Geophysical investigations to identify groundwater pathways at a small open-pit copper mine reclaimed by backfilling and sealing2011In: Mine Water – Managing the Challenges: Proceedings of the International Mine Water Association (IMWA) Congress 2011, RWTH Aachen, Germany, 4 — 11 September 2011 / [ed] Thomas R. Rüde; Antje Freund; Christian Wolkersdorfer, Aachen, Germany: RWTH Aachen University, Institute of Hydrogeology , 2011, p. 71-76Conference paper (Refereed)
  • 269. Wang, Yanmin
    et al.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Pugh, Robert
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Magnetic aggregation in dispersions of mineral ultrafines1995In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 16, no 2, p. 137-154Article in journal (Refereed)
    Abstract [en]

    Particle aggregation can be enhanced in two ways; (a) field-induced magnetic moment and (b) magnetic moment due to the remanent magnetisation. Investigation of the magnetic field-induced aggregation of hematite and chromite in aqueous suspension with the use of a laboratory scale electromagnetic solenoid related the aggregation process to particle size and external magnetic field in the natural pH value of the dispersions. This study have shown that hematite ultrafines in a well-dispersed slurry are selectively aggregated with sized magnetite in the absence of aggregating reagents, high shear rates or an external magnetic field.

  • 270.
    Watermann, Jürgen F.
    et al.
    Le Studium and LPC2E/CNRS.
    Gleisner, Hans
    Danish Meteorological Institute.
    Rasmussen, Thorkild Maack
    Geological Survey of Denmark and Greenland.
    A geomagnetic activity forecast for improving the efficiency of aeromagnetic surveys in Greenland2011In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 47, no 12, p. 2172-2181Article in journal (Refereed)
    Abstract [en]

    In recent years several aeromagnetic surveys were carried out in Greenland and more will be carried out in the future. We describe some of the characteristics pertinent to surveys in Greenland and the problems faced and experiences made by the survey teams working there, with special emphasis on the west coast where most surveys were conducted. Both unfavorable terrestrial weather and space weather appear to complicate survey planning. We discuss possible options available to the survey teams for mitigating the adverse effect of part of the problems, namely survey data contamination by intense geomagnetic activity. The implementation of a prototype geomagnetic activity forecast service as an aid to planning survey flights is discussed in more detail. The forecast service was tested by an independent observer, and the performance of the scheme is evaluated by a subsequent comparison between forecast and actual measurements. The comparison rendered largely acceptable results, but their validity is limited by the fact that the two-month test interval was characterized by a mostly relatively quiet magnetic field

  • 271.
    Wattanasen, Kamhaeng
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    A geophysical study of an arsenic contaminated area in the Ron Phibun District, Southern Thailand2001Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Geophysical surveys has been carried out in an arsenic contaminated area, the Ron Phibun District, southern Thailand, where tin and associated minerals, like arsenopyrite and pyrite, have been extracted from granites. The geophysical methods used are resistivity measurements, seismic refraction, GPR, self-potential, and magnetic susceptibility. Mining activities were started in this area for almost 10 decades ago and this together with natural processes led to contamination of arsenic in the environment. The geophysical studies have been conducted in this project with the aims to (1) create an image of underground structures and subsurface water flow, (2) to determine the distribution of arsenic contamination from the geophysical data, if a relationship between the arsenic content and the physical properties can be demonstrated. The Pole-Pole array used for resistivity pseudosection gives very good information of the subsurface geological structures. It provides information of moist and dry areas. Resistivity mapping techniques indicate a low resistivity thin layer of ca 6m to 20m depth in the western part of the study area. In the eastern part, a similar low resistivity but thicker layer is found at ca 8m to 30m depths. A high resistivity layer, interpreted as basement rocks, is found at shallow depth (10m) in the western part, while it is detected at a depth deeper than 20m in the eastern part. The basement rocks is estimated to strike in NE-SW at about 39°E, which is the boundary between the low resistivity part in the east and the high resistivity part in the west. It is interpreted as a possible fault or ridge. The eastern part is probably the main mining area that has been mined by dredging. The thick-low resistivity layer can be a track of a dredger, while the western part may have been mined at a shallower depth. When comparing the distribution of apparent resistivity and arsenic content in soil elution at 0.3 and 1m depths, there is no correlation between them. A fairly good correlation between high arsenic contents in auger water (0.5 - 5.0 mg/l) and low resistivity (25 - 100 ohm. m) is found at the depth 3.5m and 5m, which is below the groundwater table. Such a correlation is supported by the fact that the conductivity of water in which arsenic is dissolved is higher than that of pure water. However, the resistivity may only roughly reflect the distribution of arsenic content in the auger water (

  • 272.
    Wattanasen, Kamhaeng
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Environmental and hydrogeological geophysics with applications in Thailand, Laos, and Sweden2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents applications of geophysical methods in the fields of environment and hydrogeology. In relation to environmental problems, two different geophysical surveys have been carried out; one to study an arsenic contaminated area in the southern Thailand (paper I) and a second to locate shallow faults in Quaternary sediments in an area around the Ongkharak Nuclear Research Centre, central Thailand (paper II). For hydro-geological problems, surveys were conducted in southern Sweden (paper III) and in the Vientiane basin, Laos (paper IV). In the arsenic contaminated area, tin and associated minerals, i.e. arsenopyrite and pyrite, have been extracted from granites and natural processes and the mining activities led to arsenic contamination in the environment. Electrical resistivity and self potential (SP) have been used to define the distribution of arsenic contamination in the groundwater. Resistivities of 25 - 100 ohm-m and a positive SP anomaly of 66.0 mV were observed in an area where the arsenic content in auger water at 3.5 to 5.0 m depths was high, 0.5 - 5.0 mg/l. Integrated interpretation of resistivity, seismic refraction, GPR, and gravity data gave a clear image of subsurface structures at a depth to 30 m. There was a good correlation between the resistivity and the gravity data. A subsurface rise was found, which possibly acts as a naturally buried dam, separating a high contaminated area from a low contaminated area. This study has demonstrated that the combination of geophysical methods is successful in delineating contaminated areas and contributes to the understanding of a possible mechanism for the distribution of arsenic. In the Ongkharak Nuclear Research Centre area combined GPR and resistivity pseudosections (dipole-dipole and pole-pole arrays) have given a good image of shallow faults in Quaternary sediments, faults that were originally indicated from regional remote sensing interpretations. Horizontal discontinuities of reflected signals obtained by GPR and images of lateral resistivity variation have been correlated to faults or subsurface movement identified by geological mapping in trenches. This signature of the faults is caused by contrasts in dielectric permittivity and/or in resistivity, which originates from vertical displacement at sedimentary layers and from sediments filling the faults. The positions of sub-faults as identified by GPR and their strike directions obtained from the trenching data (N60°W - N70°W, N65°W - N70°W, and N30°W) agree with the general NW-SE trend of the major faults, the Mae Ping Fault Zone, the Nakhon Nayok-Prachinburi and the Ongkharak faults in central Thailand. Thermoluminescence (TL) dating showed that sub-faults in the area have been active at about 7,500-2,400, 4,800- 1,750, and 9,700-2,300 years ago. Thus, these sub-faults have been classified to be of the same generation and they are defined as "capable faults" with reference to the criteria of U.S. Nuclear Regulatory Commission. Magnetic Resonance Sounding (MRS) has been successfully tested for detecting groundwater and in combination with Vertical Electrical Sounding to characterizing aquifer in southern Sweden and in the Vientiane basin, Laos. The combination of MRS and VES in the southern areas of Sweden shows that low resistivity layers interpreted as clay are sometimes identified close to the surface. The results here have shown that the MRS signals penetrate through the clay and that deeper aquifer can still be detected. The MRS data suggest aquifers that are not only hosted in soft sediment materials (moraine, sand, and mixed materials), but also hosted in basement rocks. Based on the MRS and borehole pumping test data, the hydraulic conductivity of aquifers has been estimated and the results agree with yield, average water content and subsurface geological data. The results from the measurement in the Vientiane basin have shown that there is usually two - three water bearing layers, and the "best aquifer" is found at depths between 15 and 25 m, with regard to high water content, permeability and resistivities indicating fresh water. MRS has also shown to be an important tool in constraining layer thickness and distinguishing low resistive layers of impermeable rock from what could have been interpreted as water in the VES interpretation. MRS data also suggest a clay layer at depths between 30 and 50 m, which is overlying halite deposits. This clay layer may act as a naturally sealing layer to protect the fresh water in above aquifer from salt contamination. On the basis of this drilling for fresh water is recommended not to penetrate deeper than 20 to 40 m, depending of the local depth to the clay layer.

  • 273. Wattanasen, Kamhaeng
    et al.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Direct and indirect methods for groundwater investigations: a case of MRS and VES in the southern part of Sweden2008In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 66, no 3-4, p. 104-117Article in journal (Refereed)
    Abstract [en]

    Magnetic Resonance Sounding (MRS) has been successfully tested for detecting groundwater in two areas in southern Sweden. Measurements of Schlumberger VES have been conducted in the same place as the MRS and the results are generally consistent. Low resistivity layers interpreted as clay are sometimes identified close to the surface. The MRS result in site 2 is a good example of signals penetrating through the clay and deeper aquifer still being detected. The MRS data suggest aquifers that are not only hosted in soft sediment materials (moraine, sand, and mixed materials), but hosted in basement rocks. Based on the MRS and borehole pumping test data, the results agree with yield, average water content and subsurface geological data.

  • 274. Wattanasen, Kamhaeng
    et al.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Lohawijarn, W.
    Prince of Songkla University, HatYai.
    Bhongsuwan, T.
    Prince of Songkla University, HatYai.
    An integrated geophysical study of arsenic contaminated area in the peninsular Thailand2006In: Environmental Geology, ISSN 0943-0105, E-ISSN 1432-0495, Vol. 51, no 4, p. 595-608Article in journal (Refereed)
    Abstract [en]

    Geophysical surveys were carried out in an arsenic contaminated area, in the Ron Phibun District in southern Thailand. Here, tin and associated minerals, i.e. arsenopyrite and pyrite, have been extracted from granites and natural processes and the mining activities led to arsenic contamination in the environment. Electrical resistivity and self-potential (SP) were used to define the distribution of arsenic contamination in the groundwater. Resistivities of 25-100 Ωm and a positive SP anomaly of 66.0 mV were observed in an area where the arsenic content in auger water at 3.5-5.0 m depths was high, 0.5-5.0 mg/l. Integrated interpretation of resistivity, seismic refraction, GPR and gravity data gave a clear image of subsurface shallow structures (< 30 m depths). There was a good correlation between the resistivity and the gravity data. A subsurface rise was found, which possibly acts as a naturally buried dam, separating a high-contaminated area from a low contaminated area.

  • 275.
    Wattanasen, Kamhaeng
    et al.
    Geophysics Research Center, Department of Physics, Faculty of Science, Prince of Songkla University, Hatyai.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Lohawijarn, W.
    Geophysics Research Center, Department of Physics, Faculty of Science, Prince of Songkla University, Hatyai.
    Bhongsuwan, T.
    Geophysics Research Center, Department of Physics, Faculty of Science, Prince of Songkla University, Hatyai.
    Delineation of Arsenic contaminated area with geophysical methods in Peninsular Thailand2005In: The challenge of discovery Madrid 2005: 67th EAGE conference & exhibition incorporating SPE EUROPEC 2005, 13-16 June 2005, IFEMA, Feria de Madrid, EAGE , 2005, p. 2873-2876Conference paper (Refereed)
    Abstract [en]

    Resistivity, SP and Gravity measurement was conducted in order to delineate an arsenic contaminated area in peninsular Thailand. Low resistivity of 25 to 100 Ohm.m and positive SP anomaly of 60 mV were observed in area where arsenic contents in auger water at 3.5 to 5.0 m depths was high, 0.5 to 5.0 mg/l. In addition subsurface rise explained by high resistivity and positive gravity anomaly probably acted as a buried dam separating high contaminated area in the west from the low contaminated in the east of the study area. JICA, 1999. Draft final report on the environmental management planning survey for arsenic contaminated area of the Nakhon Si Thummarat Province in the Kingdom of Thailand

  • 276. Widenfalk, Lennart
    et al.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Enmark, Thomas
    A multidisciplinary investigation of the Notträsk Gabbro, northern Sweden1985In: Geologiska föreningens i Stockholm förhandlingar, ISSN 0016-786X, Vol. 107, no 2, p. 109-126Article in journal (Refereed)
    Abstract [en]

    The differentiated, sulfide-bearing gabbro near the city of Boden in northern Sweden has been investigated in order to get a plausible model for its formation, shape and age. The gabbro is associated with a major fault system along which several intrusive bodies occur. The largest of these has been traversed by a gravimetric, magnetometric and geological profile. The investigated intrusion is undeformed and oval-shaped and covers some 20 km2. The outer parts of the body consist of a norite in contact with older meatasediments and granites of varying age. Inside the norite occurs a magnetite-rich gabbro, which forms a ring around the centre of the massif, which in turn consists of leucogabbro-olivine gabbro. Fe, Ti and K are low in the centre where Mg and Cr have their highest contents. Impregnations of sulfides and a massive pyrrhotite vein with some 1 % Ni are located in the norite. A number of intrusion models have been tested by computer modelling combining gravimetric and magnetic field data. The most probable model seems to be a funnel-shaped body pointing downwards. The different gabbro types dip steeply inwards indicating vertical zones rather than horizontal. Palaeomagnetic measurements show that the intrusion has a similar orientation of magnetization as other gabbros of the Haparanda series in northern Sweden (1800-1900 Ga, Rb-Sr). Furthermore, the pole distributions show that the rock cooled slowly, which may indicate that the present outcrop is a deep part of an eroded intrusion. The massif is supposed to have been formed by a diapiric re-emplacement of primary horizontal cumulates formed in the sequence olivine gabbro-leucogabbro-magnetite-bearing gabbro-norite.

  • 277.
    Wyller, J.
    et al.
    Luleå tekniska universitet.
    Wellander, N.
    Luleå tekniska universitet.
    Larsson, F.
    Parasnis, Dattatray
    Burger's equation as a model for the IP phenomenon1992In: Geophysical Prospecting, ISSN 0016-8025, E-ISSN 1365-2478, Vol. 40, no 3, p. 325-341Article in journal (Refereed)
    Abstract [en]

    The dynamic response characterizing the induced-polarization (IP) phenomenon is modelled by a nonlinear diffusion equation (Burger's equation) supplemented by relevant initial and boundary values. The analysis of the model yields a voltage step response and an impedance curve in the frequency domain which agree qualitatively with experimental measurements. Curve fits based on the model have been made in the case of electrochemical cell measurements. The diffusion coefficients estimated by means of these curves are of the same order of magnitude as those calculated using experimental measurements. The normalized transient with these diffusion coefficients agrees with observations, but probably has a shorter discharge time. We have also carried out a comparison with predictions obtained from a linear, finite diffusion layer model, thus showing that for most practical situations the nonlinear term modelling the migration effect can be neglected

  • 278.
    Zaher, Mohamed Abdel
    et al.
    National Research Institute of Astronomy and Geophysics (NRIAG), University of Oulu.
    Pirttijärvi, Markku
    Department of Physics, University of Oulu.
    Korja, Toivo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Oulu Mining School, University of Oulu.
    Geophysical Studies of the Raahe-Ladoga Shear Complex in the Iisalmi Area of Finland2017In: Geophysica, ISSN 0367-4231, E-ISSN 2324-0741, Vol. 52, no 2, p. 43-67Article in journal (Refereed)
    Abstract [en]

    We have studied geophysical properties of the Raahe-Ladoga Shear Complex, a major NW-SE trending strike-slip shear zone in Central Finland. Aeromagnetic and airborne electromagnetic data from the Raahe-Ladoga Shear Complex, provided by the Geological Survey of Finland, were processed and interpreted in combination with the regional gravity data of the Finnish Geodetic Institute and the Geological Survey of Finland. Filtering techniques such as the first vertical derivative, horizontal and tilt gradients, and pseudo-gravity were applied for the visual interpretation and analyses of the shear complex in the Iisalmi area. The gravity data emphasized a NW-SE trend along a transition zone between the Archaean Karelian Province and the Palaeoproterozoic Svecofennian Province. This is consistent with the anomalies in the magnetic field intensity. Geophysical properties were also studied with gravity, magnetic and magnetotelluric ground surveys that were conducted across a narrow dominant segment of the entire shear complex near Iisalmi. The data indicated that weak negative gravity anomalies and strong magnetic anomalies are associated with the shear zone. Gravity modelling suggests that anomalies of small wavelength are related to shear zones and fractures, but the depth extent and dip cannot be resolved. Magnetic interpretation revealed that the shear zone can be modelled with near-vertical (82º eastward dip) sheet-like bodies with a depth extent over 2 km. The 2-D inversion of magnetotelluric data shows that the upper crust in the Iisalmi area is very resistive. High resistivity of the strongly sheared crust suggests the old shear complexes are not necessarily conductive opposite to many active shear complexes worldwide.

  • 279.
    Zhang, Ping
    et al.
    Department of Geophysics, Uppsala University.
    Rasmussen, Thorkild Maack
    Department of Geophysics, Uppsala University.
    Pedersen, Laust Börsting
    Department of Geophysics, Uppsala University.
    Electric resistivity structure of the Siljan impact region ( Sweden)1988In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 93, no B6, p. 6485-6501Article in journal (Refereed)
    Abstract [en]

    Based on 65 magnetotelluric (MT) measuring stations, a cross section of the electric conductivity structure in the Siljan impact area, located in the central part of Sweden, is presented. Static shift effects due to local near-surface inhomogeneities are present in nearly all of the MT soundings.In an attempt to correct for near-surface distortions, average impedance data and distortion parameters were interpreted. Derived 2-D models show some coincidence with seismic reflection results and support an impact origin of the Siljan area. Fluid migration through the fractures generated by the impact is one possible explanation for the anomalously high conductivity within the upper crust

  • 280.
    Öhlander, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Skiöld, T.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Delineation and character of the Archaean-Proterozoic boundary in northern Sweden1993In: Vol. 5, no Suppl. 1, p. 320-321Article in journal (Other academic)
  • 281.
    Öhlander, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Skiöld, T.
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Claesson, S.
    Nisca, D.H.
    Luleå tekniska universitet.
    Delineation and character of the Archaean-Proterozoic boundary in northern Sweden1993In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 64, no 1-4, p. 67-84Article in journal (Refereed)
    Abstract [en]

    Before the deposition of a Proterozoic cover and the repeated Proterozoic reworking of the older rocks, the presently exposed Archaean areas in northern Sweden formed part of a coherent craton. In the present study, we have used Sm---Nd isotopic analyses of Proterozoic granitoids and metavolcanics to delineate the Archaean palaeoboundary. In a regional context, the transition from strongly negative εNd(t) values in the northeast to positive values in the southwest is distinct, and approximately defines the border of the old craton. The Archaean palaeoboundary extends in a WNW direction, and is subparallel to the longitudinal axis of the Skellefte sulphide ore district but it is situated ≈ 100 km farther to the north. The ≈ 1.9 Ga old granitoids on the two sides of the palaeoboundary were all formed in compressional environments, but those situated to the north have higher contents of LILE and LREE at similar contents of Si. This indicates that they were generated in an area with thicker crust and supports the location of the Archaean-Proterozoic palaeoboundary. There is no simple correlation between the Archaean palaeoboundary, as defined by the isotopic results, and any of the major fracture systems as interpreted from regional geophysical measurements. Reflection seismic work indicates that juvenile volcanic-arc terrains to the south have been thrust onto the Archaean craton. Possible thrust faults have been identified from aeromagnetic measurements. Rifting of the Archaean craton created a passive margin ≈ 2.0 Ga ago. Spreading shifted to convergence with subduction beneath the Archaean continent ≈ 1.9 Ga ago. Subsequently, the resulting juvenile volcanic arc collided with the old continent, and the Archaean palaeoboundary as existing today was formed by a collision characterized by overthrusting. The boundary then was disturbed by later deformation predominantly along NNE-trending fracture systems.

  • 282.
    Öhlander, Björn
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Skiöld, Torbjörn
    Elming, Sten-åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    The Archaean-Proterozoic boundary in northern Sweden1992In: Abstracts Volume, IGCP 275 meeting Deep Geology of the Baltic Shield: Petrozavodsk September 15-17, 1992, 1992, p. 66-67Conference paper (Other academic)
3456 251 - 282 of 282
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