Ändra sökning
Avgränsa sökresultatet
1234567 101 - 150 av 542
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 101. Cas, R.A.F.
    et al.
    Allen, Rodney
    Yamagishi, H.
    Ishikawa, Y.
    Ohguchi, T.
    Eruptive style, products and setting of Kuroko Volcanics, Miocene Green Tuff Belt, Japan1990Ingår i: Gondwana; terranes and resources: Tenth Australian geological convention; abstracts, 1990, s. 34-34Konferensbidrag (Övrigt vetenskapligt)
  • 102. Chmielowski, Reia
    et al.
    Berry, Ron
    University of Tasmania.
    The Cambrian metamorphic history of Tasmania: The Metapelites2012Ingår i: Australian Journal of Earth Sciences, ISSN 0812-0099, E-ISSN 1440-0952, Vol. 59, nr 7, s. 1007-1019Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The metamorphic complexes of Tasmania formed during the Cambrian (ca 510 Ma) as a result of rapid compression in a subduction zone setting followed by rapid exhumation, which brought various fault-bounded metamorphic complexes back to the surface in less than 5 Ma. The two highest grade complexes, the Franklin Metamorphic Complex, and the Port Davey Metamorphic Complex, experienced initial growth of metamorphic garnets at *5608C, *0.56 GPa. However, their subsequent metamorphic histories diverge, with the FMC displaying a marked increase in pressure (to 1.4 GPa at peak P/T), while the PDMC shows only a slight increase in pressure (to *0.7 GPa). Both complexes show only a minor increase in temperature (*1008C) between initial garnet growth and peak metamorphic conditions. Rapid exhumation of these complexes can be accounted for by a slab-breakoff model. However, the difference in peak pressure between these complexes requires either continued subduction of the FMC while the PDMC had already begun its return towards the surface or that the subduction zone geometry resulted in significantly different pressures occurring contemporaneously within portions of the channel, which are not far removed from one another.

  • 103.
    Chmielowski, Riia
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    A comparison of the P/T Conditions Between Two Metamorphic Complexes in Tasmania, Australia2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thermodynamic modelling of the pressure/temperature conditions for the Franklin Metamorphic Complex, located in central Tasmania, and the Port Davey Metamorphic Complex, located on the south west coast of Tasmania, reveals marked contrast in the metamorphic histories of the two complexes.Garnet-core isopleth thermobarometery for both the Franklin and Port Davey Metamorphic Complexes yielded very similar results (~ 600o C, 6,000 bars) for the formation of the garnet cores in the pelitic schists from these two regions. However, their metamorphic history subsequent to their early stage of garnet growth is very different. Garnet rims and matrix minerals from samples from the Port Davey Metamorphic Complex record a temperature (~ 650o C at 6,000 bars) for their formation which is only slightly higher temperature than was obtained for the formation of the garnet cores. The Franklin Metamorphic Complex, on the other hand, appears to have maintained nearly isothermal conditions whilst undergoing a rapid increase in pressure; garnet rims and matrix minerals. the metapelites in this complex record conditions of ~700o C, 14,000 bars. These pelitic schists record a near isothermal compression event with no evidence of the retrograde path retained in the samples, indicating exhumation at plate tectonic rates.

  • 104.
    Chmielowski, Riia
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Jansson, Nils
    Boliden Mines.
    Alteration patterns of the Kristineberg area as revealed by 3D geochemical modelling2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Palaeoproterozoic Skellefte mining district in northern Sweden is one of the most important mining regions in Europe and, as a result of decades of exploration in this area, there is an extensive collection of geochemical analyses from drill holes in this area. This research compiles data from over 3,000 samples from the Kristineberg area of this district to create an overview of the alteration patterns in 3D, and, for the first time ever, this data is being compared with the regional structural 3D model, which has also been developed for this area, to determine to what extent the current structure dominates the alteration pattern. Structurally-constrained 3D interpolations of calculated alteration indexes of drill core and outcrop samples from the hydrothermally altered zones in this area reveals an excellent correlation (from surface to c. 1,000 m depth) between the zones of most intense alteration and the localization of massive sulphide deposits. The results furthermore suggest that most of the alteration zones at surface are continuous with alteration zones at depth (possibly even deeper than 1,000 m). Comparison of the geometries and spatial distribution of these 3D interpolation volumes with 3D-modelled regional faults and lithological contacts in the Kristineberg area suggest that the regional distribution of alteration zones is controlled to a significant extent by the regional structure of the area, in particular by major S-dipping faults. Consequently, the structurally- constrained 3D geochemical model presents a new and exciting tool for the identification of prospective 3D volumes in the Kristineberg area for deep exploration. In addition, the 3D approach will allow quantifications of the total budget of mass gain and loss during hydrothermal alteration in the Kristineberg area, which will allow fundamental questions regarding the nature of the hydrothermal systems and the source of elements to be answered.

  • 105.
    Chmielowski, Riia
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Jansson, Nils
    Boliden Mines, Exploration Department.
    Persson, Mac Fjellerad
    Boliden Mines.
    Fagerström, Pia
    Boliden Mines.
    3D modelling of hydrothermal alteration associated with VHMS deposits in the Kristineberg area, Skellefte district, northern Sweden2016Ingår i: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 51, s. 113-130Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This contribution presents a 3D assessment of metamorphosed and deformed, hydrothermally altered volcanic rocks, hosting the massive sulphide deposits of the Kristineberg area in the 1.9 Ga Skellefte mining district in northern Sweden, using six calculated alteration parameters: the Ishikawa alteration index, the chlorite–carbonate–pyrite index and calculated net mass changes in MgO, SiO2, Na2O and Ba. The results, which are also available as film clips in the Supplementary data, confirm inferences from geological mapping; namely that the sericite- and chlorite-rich alteration zones have complex and cross-cutting geometries and that most of these zones are semi-regional in extent and range continuously from surface to over a kilometre deep. The major known massive sulphide deposits occur proximal to zones characterised by coincidence of high values for the alteration index and chlorite–carbonate–pyrite index and large MgO gains, which corresponds to zones rich in magnesian silicates. These zones are interpreted as the original chlorite-rich, proximal parts the alteration systems, and form anomalies extending up to 400 m away from the sulphide lenses. In addition, the stratigraphically highest VHMS are hosted by rocks rich in tremolite, talc, chlorite and dolomite with lesser clinozoisite, which have high chlorite–carbonate–pyrite index and low–medium alteration index values, reflecting a greater importance of some chlorite-carbonate alteration at this stratigraphic level. Vectoring towards massive sulphide deposits in this area can be improved by combining the AI and CCPI indexes with calculated mass changes for key mobile elements. Of the ones modelled in this study, MgO and SiO2 appear to be the most useful.

  • 106.
    Chmielowski, Riia
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Jansson, Nils
    Persson, Mac Fjellerad
    Boliden Mines.
    Fagerström, Pia
    Boliden Mines.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    3D geochemical modelling of hydrothermal alteration related to 1.89 Ga VHMS-type deposits, Kristineberg area, Skellefte District2013Ingår i: Mineral deposit research for a high-tech world: Proceedings of the 12th Biennial SGA Meeting, 12-15 August 2013, Uppsala, Sweden, Uppsala: Sveriges Geologiska Undersökning , 2013, s. 66-69Konferensbidrag (Refereegranskat)
    Abstract [en]

    A 3D geochemical model of the Kristineberg area of the Skellefte District, Sweden, is currently under construction, utilizing data from more than 1600 regionally distributed whole-rock lithogeochemical samples. The model will improve our understanding of the formation the VHMS deposits in this area. The model is built by mapping geochemical variations in 3D, and using this as a basis for modelling hydrothermal alteration in the unsampled portions of the rock column. A better understanding of the geometry, intensity, vectors of transport, and zonation of the hydrothermal zones in 3D will aid deep exploration for massive sulphide deposits in the Kristineberg area, and may potentially lead to new discoveries.

  • 107.
    Dahlin, Peter
    et al.
    Department of Earth Sciences, Uppsala University.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Sjöström, Håkan
    Department of Earth Sciences, Uppsala University.
    Palaeoproterozoic metavolcanic and metasedimentary succession hosting the Dannemora iron ore deposits, Bergslagen region, Sweden2012Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 134, nr 2, s. 71-85Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Dannemora supracrustal inlier is located in the north-eastern part of the Bergslagen region in south-central Sweden and hosts the second largest iron ore deposit in the region. The metasupracrustal succession of the inlier consists of c. 1.9 Ga Palaeoproterozoic rocks that are mainly sub-alkaline, rhyolitic to dacitic, pyroclastic deposits, reworked pyroclastic deposits and metalimestone. It is c. 700-800-m thick and termed the Dannemora Formation. The formation is divided into lower and upper members and the former is in turn subdivided into subunits 1 and 2. The great thickness of individual pyroclastic deposits indicates deposition within a caldera. The rocks show characteristics of a pyroclastic origin by containing abundant pumice, cuspate and Y-shaped former glass shards, and fragmented crystals of quartz and subordinate feldspars. Scattered spherulites and lack of welding-compacted fiamme suggest that the lower member was slightly welded, where as the upper member contains sericite-replaced glass shards with preserved primary shapes indicating no welding. Undisturbed layers of ash-siltstone with normal grading and fluid-escape structures are attributed to subaqueous deposition below storm wave base in the eastern part of the inlier, where as erosion channels and cross-bedding in some of the volcaniclastic deposits imply deposition and reworking above wave base in the central part of the inlier. Epidote spots, previously interpreted as altered limestone fragments and an indicator for subaquatic deposition, are here reinterpreted as the result of selective alteration related to the intrusion of mafic dykes and to Ca release during dolomitisation of limestone.

  • 108.
    Dehghannejad, A.
    et al.
    Uppsala University.
    Juhlin, C.
    Uppsala University.
    Malehmir, A.
    Uppsala University.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    High-resolution reflection seismic imaging in the Kristineberg mining area, Northern Sweden2010Ingår i: 72nd European Association of Geoscientists and Engineers conference and exhibition 2010: Barcelona, 14 - 17 June 2010, Curran Associates, Inc., 2010, s. 5368-5371Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Kristineberg mining area is located in the western part of the Skellefte Ore District, one of the most important mining districts in Europe. As a part of a 4D geologic modeling project, two new reflection seismic profiles were acquired. Although the structural geology is complex, the processed seismic data reveal a series of steeply dipping to sub-horizontal reflections, some of which reach the surface and allow correlation with surface geology. Reflection modeling was carried out to obtain the 3D orientation of the main reflections and to provide insight into the possible contribution of out-of-the-plane reflections. The new reflection seismic profiles have improved our understanding of shallow geological structures in the area and in conjunction with recently acquired potential field data, magnetotelluric data and geological observations will help to refine previous 3D geologic modeling interpretations that were aimed at larger scale structures.

  • 109.
    Dehghannejad, M.
    et al.
    Uppsala universitet.
    Juhlin, C.
    Uppsala universitet.
    Malehmir, A.
    Uppsala universitet.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    High-resolution reflection seismic imaging in the Skellefte ore district: a contribution to 4D geologic modeling2009Ingår i: Geophysical Research Abstracts: Vol. 11, EGU2009-4894, 2009, 2009Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The Kristineberg VHMS (volcanic-hosted massive sulfide) mining area is located in the western part of the Skellefte Ore District, the most important metallogenic zone in northern Sweden. The area has been the subject of several geological and geophysical studies with the aim of understanding the contact relationships between the ore bearing volcanic and volcanosedimentary formations and the surrounding rocks. To establish the structural geologic framework at depth, two new reflection seismic profiles, a N-S directed high resolution one with a length of about 6.3 km and an E-W directed one perpendicular to the high-resolution profile with a length of about 13 km were acquired in 2008. Although the structural geology is complex, a preliminary stacked section of the high-resolution profile reveals a series of steeply dipping to sub-horizontal reflections in the southern and northern parts of the profile, many of which can be traced to the surface for correlation with surface geology. Several reflections appear to be consistent with reflections observed in two previously acquired profiles in the study area. The new reflection seismic results will be integrated with the previous reflection seismic results, potential field modeling, magnetotelluric data and geological observations to improve earlier geological interpretations that led to a pilot 3D geologic model of the study area.

  • 110.
    Dehghannejad, Mahdieh
    et al.
    Department of Earth Sciences, Uppsala University.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Malehmir, Alireza
    Department of Earth Sciences, Uppsala University.
    Juhlin, Christopher
    Department of Earth Sciences, Uppsala University.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Crustal geometry of the central Skellefte district, northern Sweden: constraints from reflection seismic investigations2012Ingår i: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 524-525, s. 87-99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Palaeoproterozoic Skellefte mining district in Sweden is one of the most important mining districts in Europe. As a part of a 4D geologic modeling project, three new sub-parallel reflection seismic profiles, with a total length of about 95 km, were acquired in the central part of the district. Processed seismic data reveal a series of gentle- to steeply- dipping reflections and a series of diffraction packages. The majority of reflections that extend to the surface can be correlated with geological features either observed in the field or interpreted from the aeromagnetic map. A set of south-dipping reflections represent inferred syn-extensional listric extensional faults that were inverted during subsequent crustal-shortening. Cross-cutting north-dipping reflections are correlated to late-compressional break-back faults. Flat-lying reflections in the central parts of the study area could represent lithological contacts within the Skellefte Group, or the contact between Skellefte Group rocks and their unknown basement. Flat-lying reflections occurring further north are inferred to originate from the top of the Jörn intrusive complex or an intrusive contact within it. So far unknown south- and north-dipping faults have been identified in the vicinity of the Maurliden deposit. Based on the seismic results, a preliminary 3D-model has been created in order to visualize the fault pattern and to provide a base for future 3D/4D modeling in the Skellefte district.

  • 111.
    Dehghannejad,, Mahdieh
    et al.
    Department of Earth Sciences, Uppsala University.
    Juhlin,, Christopher
    Department of Earth Sciences, Uppsala University.
    Malehmir, Alireza
    Department of Earth Sciences, Uppsala University.
    Juanatey, Maria A. Garcia
    Department of Earth Sciences, Uppsala University.
    Skyttä, Pietari
    Department of Geosciences and Geography, University of Helsinki, FI-00014 Helsinki.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bauer, Tobias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Reflection seismic imaging in the Skellefte ore district, northern Sweden2013Ingår i: Mineral depostits for a high-tech world: Proceedings of the 12th SGA Biennial Meeting 2013, 12-15 August 2013, Uppsala, Sweden, Uppsala: Sveriges Geologiska Undersökning , 2013, Vol. 1, s. 126-129Konferensbidrag (Refereegranskat)
  • 112.
    Dehghannejad, Mahdieh
    et al.
    Uppsala universitet.
    Juhlin, Christopher
    Uppsala universitet.
    Malehmir, Alireza
    Uppsala universitet.
    Skyttä, Pietari
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Reflection seismic imaging of the upper crust in the Kristineberg mining area, northern Sweden2010Ingår i: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 71, nr 4, s. 125-136Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Kristineberg mining area is located in the western part of the Palaeoproterozoic Skellefte Ore District, one of the most important mining districts in Europe. As a part of a 3D geologic modeling project, two new reflection seismic profiles were acquired with a total length of about 20 km. One profile (HR), parallel to previous seismic profiles, was acquired using a 10 m receiver and source interval and crosses the steeply dipping structures of the Kristineberg mine. The other profile (Profile 2) runs perpendicular to all existing profiles in the area. Although the structural geology is complex, the processed seismic data reveal a series of steeply dipping to sub-horizontal reflections, some of which reach the surface and allow correlation with surface geology. Our general interpretation of the seismic images is that the Kristineberg mine and associated mineral horizon are located in the northern part of a series of steeply south dipping structures. Overall, main structures plunge to the west at about 30° - 40°. Cross-dip analysis and reflection modeling were carried out to obtain the 3D orientation of the main reflections and to provide insight into the possible contribution of out-of-the-plane reflections. This helped, for example, to obtain the 3D geometry of a deep reflection that was previously interpreted as structural basement to volcanic rocks. The new reflection seismic profiles have improved our understanding of shallow geological structures in the area and in conjunction with recently acquired potential field data, magnetotelluric data and geological observations will help to refine previous 3D geologic modeling interpretations that were aimed at larger scale structures.

  • 113.
    Dehghannejad, Mahdieh
    et al.
    Uppsala universitet.
    Malehmir, Alireza
    Uppsala universitet.
    Juhlin, Christopher
    Uppsala universitet.
    Skyttä, Pietari
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    3D constraints and finite-difference modeling of massive sulfide deposits: the Kristineberg seismic lines revisited, northern Sweden2012Ingår i: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 77, nr 5, s. WC69-WC79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Kristineberg mining area in the western part of the Skellefte ore district is the largest base metal producer in northern Sweden and currently the subject of extensive geophysical and geologic studies aimed at constructing 3D geologic models. Seismic reflection data form the backbone of the geologic modeling in the study area. A geologic cross section close to the Kristineberg mine was used to generate synthetic seismic data using acoustic and elastic finite-difference algorithms to provide further insight about the nature of reflections and processing challenges when attempting to image the steeply dipping structures within the study area. Synthetic data suggest processing artifacts manifested themselves in the final 2D images as steeply dipping events that could be confused with reflections. Fewer artifacts are observed when the data are processed using prestack time migration. Prestack time migration also was performed on high-resolution seismic data recently collected near the Kristineberg mine and helped to image a high-amplitude, gently dipping reflection occurring stratigraphically above the extension of the deepest Kristineberg deposit. Swath 3D processing was applied to two crossing seismic lines, west of the Kristineberg mine, to provide information on the 3D geometry of an apparently flat-lying reflection observed in both of the profiles. The processing indicated that the reflection dips about 30° to the southwest and is generated at the contact between metasedimentary and metavolcanic rocks, the upper part of the latter unit being the most typical stratigraphic level for the massive sulfide deposits in the Skellefte district.

  • 114. Denisova, Nikola
    et al.
    Allan, Åsa
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Sulfide distribution and its relation to different types of skarn alteration at the Tapuli deposit, northern Sweden2013Ingår i: Mineral deposit research for a high-tech world: proceedings / [ed] Erik Jonsson, Uppsala: Sveriges Geologiska Undersökning , 2013, s. 1539-1542Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Tapuli deposit is a skarn iron ore located in the Pajala municipality in Northern Sweden. It is situated at the margin of the Karelian craton, at the stratigraphic contact between Karelian and Svecofennian rocks. The ore forms stratabound lenses concordant with the metasedinnentary sequences and dips 45 - 60 degrees towards NW. Footwall rocks are dolomitic marbles, phyllites and graphitic phyllites; the hanging wall comprises phyllites and quartzites. Mafic dykes and sills crosscut the stratigraphic succession. Magnetite is the only ore mineral. The skarn minerals are serpentine, diopside, tremolite and actinolite. The skarn altered rocks show a zonation with serpentine skarn closest to or as part of the ore, thereafter, tremolite-diopside skarn and, finally, actinolite skarn closest to the phyllites and quartzites in the hanging wall. Sulfides occur in minor amounts, but their content generally increases with proximity to the footwall rocks. The dolomitic marble was the precursor of the serpentine and tremolite-diopside skarn. Immobile element data suggests that mafic dykes and sills were the precursors of the actinolite skarn. Possible controls of the sulfide distribution are the presence of sulfide-bearing source rocks (dolomitic marble, graphitic phyllite) and rennobilization of sulfides during the intrusion of mafic dykes.

  • 115.
    Drielsma, Johannes A
    et al.
    European Association of Mining Industries, Metal Ores and Industrial Minerals, Avenue de Broqueville/Broquevillelaan 12, 1150 Brussels.
    Russell-Vaccari, Andrea J.
    Align Consulting, 1134 Cross Creek Ct., Sheridan, WY.
    Drnek, Thomas
    RHI AG, Magnesitstrasse 30, 8614 Breitenau.
    Brady, Tom
    Newmont Mining, 6363 South Fiddler’s Green Circle Suite 800, Greenwich Village, CO 80111.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mistry, Mark
    The Nickel Institute, Avenue des Arts/Kunstlaan, 13, 1210 Brussels.
    Simbor, Laia Perez
    European Copper Institute, Avenue de Tervueren/Tervurenlaan 168 b-10, 1150 Brussels.
    Erratum to: Mineral resources in life cycle impact assessment: defining the path forward2016Ingår i: The International Journal of Life Cycle Assessment, ISSN 0948-3349, E-ISSN 1614-7502, Vol. 21, nr 1, s. 133-Artikel i tidskrift (Refereegranskat)
  • 116.
    Drielsma, Johannes A
    et al.
    European Association of Mining Industries, Metal Ores and Industrial Minerals, Avenue de Broqueville/Broquevillelaan 12, 1150 Brussels.
    Russell-Vaccari, Andrea J.
    Align Consulting, 1134 Cross Creek Ct., Sheridan, WY.
    Drnek, Thomas
    RHI AG, Magnesitstrasse 30, 8614 Breitenau.
    Brady, Tom
    Newmont Mining, 6363 South Fiddler’s Green Circle Suite 800, Greenwich Village, CO 80111.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mistry, Mark
    The Nickel Institute, Avenue des Arts/Kunstlaan, 13, 1210 Brussels.
    Simbor, Laia Perez
    European Copper Institute, Avenue de Tervueren/Tervurenlaan 168 b-10, 1150 Brussels.
    Mineral resources in life cycle impact assessment: defining the path forward2016Ingår i: The International Journal of Life Cycle Assessment, ISSN 0948-3349, E-ISSN 1614-7502, Vol. 21, nr 1, s. 85-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose: Despite 20 years of research, there remains no robust, globally agreed upon method—or even problem statement—for assessing mineral resource inputs in life cycle impact assessment (LCIA). As a result, inclusion of commonly used methods such as abiotic depletion potential (ADP) in life cycle assessment (LCA)-related evaluation schemes could lead to incorrect decisions being made in many applications. In this paper, we explore in detail how to improve the way that life cycle thinking is applied to the acquisition of mineral resources and their metal counterparts. Methods: This paper evaluates the current body of work in LCIA with regard to “depletion potential” of mineral resources. Viewpoints from which models are developed are described and analyzed. The assumptions, data sources, and calculations that underlie currently used methods are examined. A generic metal-containing product is analyzed to demonstrate the vulnerability of results to the denominator utilized in calculating ADP. The adherence to the concept of the area of protection (AOP) is evaluated for current models. The use of ore grades, prices, and economic availability in LCIA is reviewed. Results and discussion: Results demonstrate that any work on resource depletion in a life cycle context needs to have a very clear objective or LCIA will not accurately characterize mineral resource use from any perspective and decision-making will continue to suffer. New, harmonized terminology is proposed so that LCA practitioners can build better mutual understanding with the mineral industry and recommendations regarding more promising tools for use in life cycle sustainability assessment (LCSA) are given. Conclusions: The economic issue of resource availability should be evaluated in parallel with traditional LCA, not within. LCIA developers should look to economists, the market, and society in general, for broader assessments that consider shorter-time horizons than the traditional LCIA methods. To do so, the concept of the AOP in LCA needs to be redefined for LCSA to ensure that models estimate what is intended. Finally, recommendations regarding mineral resource assessment are provided to ensure that future research has a sound basis and practitioners can incorporate the appropriate tools in their work

  • 117.
    Edblom, Nils
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Styles of mineralization in the Nautanen IOCG deposit2020Självständigt arbete på avancerad nivå (yrkesexamen), 300 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Nautanen is an IOCG (Iron Oxide Copper Gold) deposit located in northern Sweden, 10 km north-east of the town Gällivare in the county of Norrbotten. It was mined for copper for seven years in the early 1900´s and is presently explored by Boliden Mineral AB. The deposit sits within a package of shoshonitic andesites of the Porphyrite group. The rocks have been suggested to be formed in a continental back arc setting and are now hosting the major shear zone NDZ (Nautanen Deformation Zone).

    The deposit is characterized by an early peripheral magnetite – amphibole alteration and a main mineralization event of pyrite – chalcopyrite – potassium alteration. The majority of the copper- and iron- sulphides occur as veins and stockwork-network textures in strongly potassium-garnet altered schist. The gold occurs as Ag-Au or Ag-Au-Hg mineral grains of 1-30 µm. They are mostly found in fissures within pyrite and magnetite which indicates a later redistribution. The element association and tectonic setting fits well with the general IOCG model, while the mineralogy is not typical for IOCG deposits.

  • 118.
    Edfelt, Åsa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Geology, alterations and mineral chemistry of the Tjårrojåkka Fe-oxide Cu-Au occurrences, northern Sweden2003Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The Tjårrojåkka area is located about 50 km WSW of Kiruna, northern Sweden, and hosts one of the best examples of spatially related Fe-oxide Cu-Au occurrences (the Tjårrojåkka-Fe and Tjårrojåkka-Cu). The bedrock, depositional environment and tectonic evolution of the area were studied through petrological, geochemical and geophysical-petrophysical investigations. The bedrock is dominated by intermediate and basic extrusive and intrusive rocks. The intermediate andesites and basaltic andesites are cut by diabases which acted as feeder dykes for the overlying basalts. The intrusive rocks range from gabbro to quartz-monzodiorite in composition. The area is metamorphosed to epidote-amphibolite facies and has been affected by scapolite, K-feldspar, epidote and albite alteration that is more intense in the vicinity of deformation zones and mineralisations. Based on geochemistry the andesites and basaltic andesites are similar to the Svecofennian Porphyrite Group intermediate volcanic rocks, but have also features common with the intermediate volcaniclastic unit in the underlying Kiruna Greenstone Group. Chemically the basalts and diabases have the same signature, but cannot directly be correlated with any known basaltic unit. Some of the samples have characteristics comparable to the basalts of the Kiruna Greenstone Group. Whether the volcanic sequence at Tjårrojåkka represents the Porphyrite Group or is part of the greenstones could not be unequivocally determined without geochronological data. Three events of deformation have been distinguished in the Tjårrojåkka area; the first one involving NW-SE compression creating NE-SW-striking steep foliation corresponding with the strike of the Tjårrojåkka-Fe and Cu bodies, followed by the creation of an E-W deformation zone. Finally a second compressional event resulted in folding and the formation of a NNW-SSE striking and gently dipping structure possible related to thrusting from SW. The Tjårrojåkka apatite-magnetite ore (52.6 Mt of iron ore @ 51.5% Fe) is a blind ore consisting of a massive magnetite core surrounded by an ore- breccia containing low-grade Cu-mineralisation. Apatite, amphiboles and carbonate occur disseminated and as veins within the massive ore and in the wall rock. The Tjårrojåkka-Cu mineralisation is located 750 m from the Tjårrojåkka-Fe and contains 3.23 Mt ore @ 0.87% Cu. The main ore minerals are chalcopyrite and bornite occurring both disseminated and in veinlets. Minor pyrite, molybdenite and gold have also been observed. The host rock has been affected by strong albite, scapolite, amphibole and K-feldspar alteration. The alteration assemblages at Tjårrojåkka are highly variable with several of the alteration minerals occurring in several generations and settings, and with multiple reactivations of already existing veins and overlapping alteration stages indicating a complex, long history of fluid activity in the area. Similarity in alteration minerals and paragenesis in the iron and copper mineralisation is described in terms of whole rock geochemistry, mineral chemistry and paragenesis. This may partly be explained by the common host rock to the mineralisations, but indicates also similarities in fluid composition. Within the massive magnetite ore apatite, tremolite and carbonate veinlets fill fractures probably formed during cooling of the magnetite body. The wall rock has been affected by extensive pervasive albite and plagioclase alteration. Scapolite occurs locally as porphyroblasts and later veins. The albitised and scapolitised rocks are overprinted by pervasive K-feldspar alteration and veins of K-feldspar + Mg-hornblende ± titanite ± quartz ± magnetite ± sulphides along the foliation. Epidote is common in veins together with K-feldspar. Allanite occurs as an accessory mineral associated with epidote, otherwise REE-minerals are rare. Carbonate and zoelites were the last phases to form in vacancies. The area between the apatite-iron and copper bodies is strongly albite + magnetite altered. The footwall of the copper body is characterised by pervasive albite alteration spatially associated with magnetite and apatite veins cut by later carbonate veinlets. Scapolite (porphyroblasts and veins) is formed in an early stage in the hanging wall overprinted by pervasive K-feldspar alteration. Amphiboles (tschermakites, Mg-hornblende and actinolite) occur in several generations as porphyroblasts, in veins on its own, or together with K-feldspar ± titanite ± quartz ± carbonate ± chalcopyrite ± bornite. Epidote, REE- carbonate, zeolites and fluorite are the latest alteration phases in the copper mineralisation. Ba, Cl, S and F are enriched in the alteration minerals in the Tjårrojåkka occurrences. Barium-rich varieties of K-feldspar (max. 3.5% BaO) occur in the Cu-mineralised breccia surrounding the apatite-magneitie body indicating high concentrations of Ba in the hydrothermal fluids. Absence of sulphate in the fluids probably caused the formation of Ba-feldspars instead of barite. Scapolite shows a trend with more Cl-rich varieties around the magnetite body gradually getting more SO3 and CO2-rich in the Cu-mineralisation. The presence of accessory barite in the copper mineralisation also indicates that the SO3 content in the fluids were higher than in the iron ore. The biotites are rich in Ti while Cl and F contents are more moderate and do not show great variation in different parts of the systems. All amphiboles are Ca-rich ranging from tschermakites, Mg-hornblende to actinolite and tremolite. The apatites are F-dominate with higher Cl content in the apatite- iron ore than in the copper occurrence. Overall the alteration minerals related to the apaite-iron ore are more rich in Cl and Ba than the ones in the Cu-mineralisation that show higher contents of F, SO3 and CO2.

  • 119.
    Edfelt, Åsa
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The Tjårrojåkka apatite-iron and Cu (-Au) deposits, northern Sweden: products of one ore forming event2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The Tjårrojåkka area is located about 50 km WSW of Kiruna, northern Sweden, and hosts one of the best examples of spatially related apatite-iron (Kiruna type) and Cu (-Au) deposits in Sweden. The results from this project show that the two deposits are genetically related and indicate the presence of a younger, previously unknown, 1780 Ma generation of apatite- iron ores in northern Sweden. The bedrock in the Tjårrojåkka area is dominated by intermediate and basic extrusive and intrusive rocks. The 1880 Ma intermediate volcanic rocks, belonging to the Porphyrite Group, formed in association with subduction- related magmatism in a volcanic arc environment close to the Archaean continental margin. The overlying basalts and related feeder dykes formed through extrusion of mantle derived magma during a local extensional event in a subaquatic back arc setting. The area was metamorphosed at epidote- amphibolite facies and deformed during at least three stages, creating NE- SW, E-W, and NNW-SSE striking structures. The Tjårrojåkka deposits can be considered as belonging to the Fe-oxide-Cu- Au (IOCG) group of deposits representing two "end-members" of the class. Several generations and overlapping hydrothermal alteration stages indicate a long, complex history of fluid activity between 1780 and 1700 Ma related to the formation and post ore modification of the deposits. The strongly altered host rock shows enrichment of alkalis related to mineralisation due to the formation of albite, scapolite, and K-feldspar. It is not obvious whether the massive part of the apatite-iron ore formed from an iron rich melt or through hydrothermal replacement, but a hydrothermal system was active at least at a late stage during the deposition of the iron ore, producing the apatite-magnetite-actinolite breccia, the copper mineralisation, as well as the extensive hydrothermal alterations. The ore forming fluids were CO2-bearing, moderately to highly saline CaCl2- NaCl-rich fluids of most likely magmatic origin. The magnetite ore deposited at around 500 to 650°C followed by the copper mineralisation between 150 and 450°C. Cooling along with decrease in salinity were important factors for metal precipitation at Tjårrojåkka. A NE trending shear zone acted as a major fluid channel and a structurally favourable location for the deposition of the copper (-gold) mineralisation. From apatite chemistry, it is evident that there is a fundamental difference between typical Kiruna type apatite-iron ores and copper mineralised apatite-iron deposits of IOCG character and could potentially be used as a tool for distinguishing copper mineralising apatite-iron systems from barren.

  • 120. Edfelt, Åsa
    et al.
    Armstrong, Robin N.
    Natural History Museum, London.
    Smith, Martin
    University of Brighton.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Alteration paragenesis and mineral chemistry of the Tjårrojåkka apatite-iron and Cu (-Au) occurrences, Kiruna area, northern Sweden2005Ingår i: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 40, nr 4, s. 409-434Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The northern Norrbotten area in northern Sweden, is an important mining district and hosts several deposits of Fe-oxide Cu-Au-type. One of the best examples of spatially, and possibly genetically, related apatite-iron and copper-gold deposits in the region is at Tjårrojåkka, 50 km WSW of Kiruna. The deposits are hosted by strongly sheared and metamorphosed intermediate volcanic rocks and dolerites and show a structural control. The Tjårrojåkka iron deposit is a typical apatite-iron ore of Kiruna-type and the Tjårrojåkka copper occurrence shows the same characteristics as most other epigenetic deposits in Norrbotten. The host rock has been affected by strong albite and K-feldspar alteration related to mineralisation, resulting in an enrichment of Na, K, and Ba. Fe and V were depleted in the altered zones and added in mineralised samples. REE were enriched in the system, with the greatest addition related to mineralisation. Y was also mobile associated with albite alteration and copper mineralisation. The Tjårrojåkka iron and copper deposits show comparable hydrothermal alteration minerals and paragenesis, which might be a product of common host rock and similarities in ore fluid composition, or overprinting by successive alteration stages. Mineralogy and mineral chemistry of the alteration minerals (apatite, scapolite, feldspars, amphiboles, and biotite) indicate a higher salinity and Ba/K ratio in the fluid related to the alterations in the apatite-iron occurrence than in the copper deposit, where the minerals are enriched in F and S. The presence of hematite, barite, and in SO4 in scapolite suggests more oxidising-rich conditions during the emplacement of the Tjårrojåkka-Cu deposit. From existing data it might be suggested that one evolving system created the two occurrences, with the copper mineralisation representing a slightly later product.

  • 121. Edfelt, Åsa
    et al.
    Broman, C.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    A preliminary fluid inclusion study of the Tjårrojåkka IOCG-occurrence, Kiruna Area, northern Sweden2004Ingår i: The 26th Nordic Geological Winter Meeting: abstract volume / [ed] Joakim Mansfeld, Uppsala: Geological Society of Sweden , 2004, s. 148-Konferensbidrag (Refereegranskat)
  • 122. Edfelt, Åsa
    et al.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Fennoscandian Shield: iron oxide-copper-gold deposits. Tjårrojåkka, northern Sweden: Lat 67° 40′ N, Long. 19° 10′ E2005Ingår i: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 27, nr 1-4, s. 328-329Artikel i tidskrift (Refereegranskat)
  • 123. Edfelt, Åsa
    et al.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The Tjårrojåkka Fe-oxide and Cu-Au occurrences northern Sweden: products of one ore forming event?2004Konferensbidrag (Övrigt vetenskapligt)
  • 124. Edfelt, Åsa
    et al.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The Tjårrojåkka Fe-oxide Cu(-Au) occurrence, Kiruna area, northern Sweden2003Ingår i: Mineral Exploration and Sustainable Development: proceedings of the Seventh Biennial SGA Meeting, Athens, Greece, 24-28 August 2003 / [ed] D.G. Eliopoulos, Rotterdam: Millpress , 2003, s. 1069-1071Konferensbidrag (Refereegranskat)
  • 125. Edfelt, Åsa
    et al.
    Sandrin, Alessandro
    Luleå tekniska universitet.
    Evins, Paul
    EGRU, School of Earth Sciences, James Cook University.
    Jeffries, Teresa
    Natural History Museum, London.
    Storey, Craig
    Open University, Walton Hall, Milton Keynes.
    Elming, Sten-åke
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Stratigraphy and tectonic setting of the host rocks to the Tjårrojåkka Fe-oxide Cu-Au deposits, Kiruna area, northern Sweden2006Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 128, nr 3, s. 221-232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Tjårrojåkka area is located about 50 km WSW of Kiruna, northern Sweden, and hosts one of the best examples of spatially and possibly genetically related Fe-oxide and Cu-Au occurrences in the area. The bedrock is dominated by intermediate and basic extrusive and intrusive rocks. An andesite constrains the ages of these rocks with a U-Pb LA-ICPMS age of 1878±7 Ma. They are cut by dolerites, which acted as feeder dykes for the overlying basalts. Based on geochemistry and the obtained age the andesites and basaltic andesites can be correlated with the 1.9 Ga intermediate volcanic rocks of the Svecofennian Porphyrite Group in northern Sweden. They formed during subduction-related magmatism in a volcanic arc environment on the Archaean continental margin above the Kiruna Greenstone Group. Chemically the basalts and associated dolerites have the same signature, but cannot directly be related to any known basaltic unit in northern Sweden. The basalts show only minor contamination of continental crust and may represent a local extensional event in a subaquatic back arc setting with extrusion of mantle derived magma. The intrusive rocks range from gabbro to quartz-monzodiorite in composition. The area is metamorphosed at epidote-amphibolite facies and has been affected by scapolite, K-feldspar, epidote, and albite alteration that is more intense in the vicinity of deformation zones and mineral deposits. Three events of deformation have been distinguished in the area. D1 brittle-ductile deformation created NE-SW-striking steep foliation corresponding with the strike of the Tjårrojåkka-Fe and Cu deposits and was followed by the development of an E-W deformation zone (D2). A compressional event (D3), possible involving thrusting from the SW, produced folds in the central part of the area and a NNW-SSE striking deformation zone in NE.

  • 126. Edfelt, Åsa
    et al.
    Smith, M.
    University of Brighton.
    Armstrong, R.N.
    Natural History Museum, London.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Apatite chemistry - a potential tool for IOCG exploration2006Ingår i: The 27th Nordic Geological Winter Meeting, January 9-12, 2006, Oulu, Finland: abstract volume / [ed] Petri Peltonen ; Antti Pasanen, Helsinki: Geological Society of Finland , 2006, s. 29-Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Northern Norrbotten is an important mining region of Sweden and is regarded as an iron-oxide copper-gold (IOCG) district hosting several apatite-iron oxide and copper-gold sulphide ores (e.g. Hitzman et. al., 1992). The IOCG group of deposits is diverse with respect to age, host rock, ore and alteration mineralogy as well as ore-forming processes and there is still an ongoing debate regarding a possible genetic link between "classical" Kiruna type ores and copper dominated end-members within this class of deposits. Apatites from Kiruna-type apatite-iron deposits (Kiirunavaara, Rektorn, Nukutus, Ekströmsberg, Tjårrojåkka-Fe), IOCG copper occurrences (Tjårrojåkka-Cu and Nautanen), a 1.89 Ga andesite and a Perthite-monzonite group intrusion were collected and analysed for their mineral chemistry and rare earth elements using electron microprobe and LA-ICPMS analysis. The apatite chemistry can subsequently be used as an indicator of the composition of fluids involved in the formation of the deposits (Korzhinskiy, 1982). Different trends with regard to F-Cl content as well as REE pattern in the apatites were observed for apatite-iron ores with no spatial relation to copper mineralisation compared to the apatite-iron ore spatially related to a copper occurrence. The apatites from the former were almost pure F-apatites with steep REE patterns, while the apatites from the latter and the copper mineralisations themselves contained a large Cl-component and showed depletion in LREE.It can be concluded that apatite chemistry could be a potential tool for distinguishing copper mineralising apatite-iron systems from barren ones. However, so far only one apatite-iron deposit spatially related to a copper occurrence has been studied and more studies are needed to confirm the results.

  • 127. Egagha, E.
    et al.
    Weihed, Pär
    Gravimetric surveys of the bedrock in the Unden region, province of Skaraborg, Sweden1993Rapport (Övrigt vetenskapligt)
  • 128. Eilu, P.
    et al.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ojala, V.J.
    Niiranen, T.
    Lahtinen, R.
    Tectonic setting of Neoarchaean and Palaeoproterozoic gold mineralisation in Fennoscandian shield2005Ingår i: STOMP 2005 : structure, tectonics and ore mineralisation processes: abstract volume / [ed] Haidi Hancock, Townsville, Qld: James Cook University of North Queensland , 2005, s. 45-Konferensbidrag (Övrigt vetenskapligt)
  • 129.
    Eilu, Pasi
    et al.
    Geological Survey of Finland.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Epigenetic au and cu-au deposits2007Ingår i: Metallogeny and tectonic evolution of the Northern Fennoscandian Shield: field trip guidebook, Espoo: Geological Survey of Finland , 2007, s. 22-25Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 130.
    Eilu, Pasi
    et al.
    Geological Survey of Finland.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Fennoscandian Shield: Orogenic gold deposits2005Ingår i: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 27, nr 1-4, s. 326-327Artikel i tidskrift (Refereegranskat)
  • 131.
    Eilu, Pasi
    et al.
    Geological Survey of Finland.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Iljina, Markku
    Geological Survey of Finland.
    Ojala, Juhani
    Geological Survey of Finland.
    Ore deposits2007Ingår i: Metallogeny and tectonic evolution of the Northern Fennoscandian Shield: field trip guidebook, Espoo: Geological Survey of Finland , 2007, s. 15-16Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 132.
    Elming, Sten-åke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Enmark, Thomas
    Widenfalk, Lennart
    A combined geological petrophysical and geophysical investigation of the Notträsk gabbro, northern Sweden1983Ingår i: Vol. 105, nr 4, s. 386-387Artikel i tidskrift (Refereegranskat)
  • 133.
    Elming, Sten-åke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Moakhar, Mohsen Oveisy
    Razi University, Kermanshah.
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    A palaeomagnetic and geochemical study of basic intrusions in northern Sweden2004Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 126, nr 2, s. 243-252Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A palaeomagnetic and geochemical study has been performed on basic dykes in northern Sweden. The dykes and a gabbro formation were sampled in 28 sites and characteristic magnetizations could be defined in 23 of them. The dykes form a part of a swarm that trends in NE-SW to E-W. From differences in palaeomagnetic signatures and composition it is concluded that this swarm is composed of two generations of dykes, group A and B, trending in similar directions. The dykes of group A have compositions that are similar to rapakivi related dykes, while those of group B are different from most rapakivi dykes in Fennoscandia. The calculated pole positions may suggest that the group B dykes are older than those of group A and both groups intruded within the time span 1.77 Ga to 1.50 Ga. The trend of the dykes is more or less parallell to a palaeo-compressional stress field that may be expected from the collisional tectonics related to the Gothian orogeny. The intrusion of the rapakivi formations in Fennoscandia has been suggested to be related with the Gothian orogeny and the intrusion of the dykes may thus be guided by the stress field generated by the collisional tectonics.

  • 134.
    Elming, Sten-åke
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Widenfalk, LennartRodriguez, DionisioCentro de Investigaciones Geoscientificas, Universidad Nacional Autonoma de Nicaragua.
    Geoscientific research in Nicaragua: a Swedish-Nicaraguan joint project during the period 1981-19911998Samlingsverk (redaktörskap) (Övrigt vetenskapligt)
  • 135.
    Ericsson, Magnus
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Samhällsvetenskap.
    Drielsma, Johannes
    European Association of Mining Industries, Metal Ores and Industrial Minerals, Brussels, Belgium.
    Humphreys, David
    CEPMLP, Dundee University, Dundee, UK.
    Storm, Per
    EIT Raw Materials North AB, Luleå, Sweden.
    Weihed, Pär
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Why current assessments of ‘future efforts’ are no basis for establishing policies on material use: a response to research on ore grades2019Ingår i: Mineral Economics, ISSN 2191-2203, E-ISSN 2191-2211, Vol. 32, nr 1, s. 111-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The concept of declining availability due to declining primary resource quality has been investigated for various resource categories to try to determine the effort needed in future to either extract the resource or to treat it for intended use. The concept of ‘future efforts’ due to declining primary resource quality is explored by Vieira et al. (2016, 2017). They suggest that a specific burden associated with the production of each primary material should be taken into account and that this can be done by studying the costs of production or ore requirements of the material and by projecting forward likely costs into the future. For the purpose of the analysis, they employ mine cost data for 2000–2013 and reserve data published by the US Geological Survey. We will argue below that this approach is not correct and, with this comment, we wish to make it clear that—contrary to what is suggested in much of the Life Cycle Assessment literature—the future efforts concept is not an established rule of natural resource extraction. For mineral resources, it is quite impossible to proceed with extraction in the ordered way that this approach suggests because nobody has a comprehensive view of the entire natural resource. Secondly, there is no evidence available to support the idea that extracting a mineral resource today causes a decrease in availability of that mineral tomorrow. On the contrary, the weight of evidence suggests that where declines in ore grades have been observed, they are overwhelmingly due to technology development in response to high demand and have been accompanied by increased mining efficiency and increased availability of the resource to successive generations. Grade is a rather arbitrary measure since the grade of mined ore ultimately has to do with the relationship of costs and revenues. It is not only the technology employed which matters but also how smartly this technology is applied. Thirdly, the future efforts approach entirely overlooks the potential availability of mineral materials from secondary (scrap) sources, sources which are expected to become increasingly important to mineral supply in the future. Our conclusion from the discussion is that we as humans have been able to economically access ever-increasing amounts of material from often lower and lower-grade sources. What is impossible to conclude from this is that the environment no longer contains any of the higher-grade sources. In fact, all the available evidence suggests that higher-grade deposits are still out there. We remain critical optimists.

  • 136.
    Estholm, Madelen
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Mineralogical and Geochemical characterization of the Fe-Cu-Occurrence and associated Hanging wall and Footwall Alteration halo of the Viscaria D-Zone, Kiruna District, Northern Sweden2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Northern Norrbotten County is one of the three major ore producing districts in Sweden. Based on the predominance of epigenetic Cu-Au and Fe-oxide mineralization this region is regarded as a typical IOCG province. The massive to layered Viscaria Cu-deposit is proposed to be a VMS deposit of Besshi-type and is unique in deposit type of the region. The volcaniclastic rocks of the Viscaria Formation hosting the Viscaria deposit belong to the rift related Kiruna Greenstone Group. The Viscaria deposit consists of three stratiform-stratabound mineralized zones: A-, B- and D-zone. Sulphide mineralization of the D-zone differs in structural features, host rock, mineralization style and Fe-oxide dominance over Cu-sulphides compared to the main Cu-ore in the A-zone. These differences between A- and D-zone mineralization styles raise the subject that the D-zone could be of a different origin.  

    The Kiruna area is mainly covered by glacial-till, which contributes to limited bedrock exposure. This becomes a challenge when exploring for new deposits and highlights the importance of good geological knowledge obtained from existing deposits to carry through successful exploration programs. The objective of this study is to characterize the Fe-Cu-occurrence and the associated alteration halo of the Viscaria D-zone. Alteration halos can reach several kilometres away from the main ore zone and provides mineralogical and chemical signatures that extend the target area significantly in exploration for new deposits.

    Detailed core logging, optical microscopic studies, lithogeochemistry and electron microprobe analyses was utilized to contribute to a better genetic understanding of the D-zone and the associated hanging wall and footwall alteration features. The study shows that the main ore minerals of the D-zone consist of magnetite and chalcopyrite, and minor pyrite and hematite. The major alteration minerals associated with mineralization are calcite, actinolite/tremolite, epidote, chlorite and also biotite and scapolite in the hanging wall. The most prominent potential ore vector is calcite veins and biotite, as the abundance increase towards the D-zone. D-zone are further characterised by low REE concentrations, similarly to the calcic-dolomite host.

    The study also shows that the alteration halo of the D-zone is different in the hanging wall compared to the footwall, which is confirmed by the lithogeochemistry and mineral chemistry. The footwall is characterized by spilitization and chlorite alteration. The lithogeochemistry of the D-zone and the hanging wall reveals element mobility of Mg, Ba, Fe, Na, K, Cu and Zn. Mineral chemistry of epidote, amphibole and chlorite shows chemical changes in Fe/Al- and Mg/Fe-ratios. According to the result of this thesis and earlier studies, the D-zone mineralization is suggested to be part of the VMS system forming the stratigraphically above laying A-zone of the Viscaria Cu-deposit.

  • 137.
    Fahlvik, Anton
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Hydrothermal alteration and lithogeochemical marker units at the Svärdsjö Zn-Pb-Cu deposit, Bergslagen, Sweden, and their implications for exploration2018Självständigt arbete på avancerad nivå (masterexamen), 80 poäng / 120 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In exploration, a lithogeochemical approach can be used to aid the characterisation of rocks surrounding metamorphosed and hydrothermally altered deposits. Accurate description of the geological setting of deposits is crucial for understanding the ore forming processes and identifying targets for exploration. The Svärdsjö Zn-Pb-Cu deposit is located in the heavily mineralised and metamorphosed Bergslagen ore province of south-central Sweden. The deposit and surrounding minor occurrences were actively mined for over 500 years, producing more than 1 Mt of Zn-Pb-Cu-Ag massive sulphide ore. The combination of strongly metamorphosed and hydrothermally altered rocks in Svärdsjö makes geological interpretation challenging. Therefore, an approach combining lithogeochemical and petrographic methods is used in this study. The characterisation of the rocks and hydrothermal alteration surrounding the deposit allowed for an interpretation of ore formation and its implications for further exploration in the Svärdsjö area. The results verified that the Svärdsjö mineralisations are hosted by 2–15 m thick dolomitic marble units, commonly altered to skarn. Surrounding the deposit are subvolcanic intrusions and volcanoclastic rocks of mainly dacitic composition. The combined approach also helped identifying a strong to intense hydrothermal chlorite-sericite alteration enveloping the mineralised marble units and resulted in large mass gains of Fe and Mg whereas Na was depleted. Multiple episodes of alteration and metamorphism are evident from cross-cutting relationships with less altered dykes and overprint by metamorphic minerals such as cordierite and anthophyllite. An ore formation model involving sub-seafloor volcanic-associated replacement is suggested for the Svärdsjö deposit based on (i) the presence of a zoned hydrothermal alteration system within a volcanoclastic rock sequence and (ii) the irregular stratabound sulphide lenses hosted by thin marble units in the centre of the alteration system. Additionally, it is inferred that the stratabound nature of the deposit is caused by the neutralisation of a hot acidic fluid, resulting in precipitation of the sulphides within the marble. Finally, two geochemically distinct lithological units have been identified adjacent to the mineralised zones, providing new, larger exploration targets in the area. Mass change calculations reveal that Fe and Mg enrichment and Na depletion are useful vectors towards mineralisation, with detectable changes extending for up to 100 m from the mineralised lenses. These findings showcase the usefulness of the incorporation and careful interpretation of lithogeochemical data when exploring for metamorphosed hydrothermal ore deposits in mineralised provinces of the Fennoscandian Shield or elsewhere in the world.

  • 138.
    Fettweis, Reginald
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Bark, Glenn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    The new Vindelgransele gold ore domain, northern Sweden: preliminary results from the Fabodtjarn lode gold deposit2017Ingår i: Mineral Resources to Discover / [ed] Mercier Langevin, P; Dube, B; Bardoux, M; Ross, PS; Dion, C, Society for Geology Applied to Mineral Deposits , 2017, s. 139-142Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Fabodtjarn lode gold deposit is located in the Vindelgransele area, in the Skellefte District, in northern Sweden. The mineralization consists of a quartz vein system hosted in a sequence of turbiditic greywackes and pelitic sedimentary rocks, situated 20-30 meters above the contact with a granodiorite sill. The aim of the study is to better understand the genesis and controls on ore at Fabodtjarn and improve exploration guides for the area. Gold deposits have been known in the Skellefte District for over a century. However, there is an ongoing debate whether some of these deposits are intrusion-related or orogenic gold. Several gold deposits in the Vindelgransele area are spatially associated with intrusive rocks. There might thus be a genetic link between the Fabodtjarn deposit and the intrusion, or the intrusive rocks have simply acted as structural traps during compressional stress conditions.

  • 139.
    Frank, Katherine S
    et al.
    Department of Geological and Atmospheric Sciences, Iowa State University.
    Spry, Paul
    Department of Geological and Atmospheric Sciences, Iowa State University.
    Raat, Hein
    Boliden Mines.
    Allen, Rodney
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Jansson, Nils
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    O'Brien, Joshua J
    Department of Geological and Atmospheric Sciences, Iowa State University.
    Whole Rock-Rare Earth Element and Magnetite Chemistry as Guides to Exploration for Metamorphosed Base Metal Sulfide Deposits in the Stollberg Ore Field, Bergslagen, Sweden2014Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    The Stollberg ore field (~12 Mt), 50 km W of the giant Garpenberg Zn-Pb-Ag-(Cu-Au) district (>100 Mt) occurs in the regional Stollberg F2 syncline within 1.9 Ga bimodal felsic and mafic rocks metamorphosed to the amphibolite facies. Sulfide mineralization is hosted by volcanic rocks and skarn and consists of massive to semi-massive sphalerite-galena and pyrrhotite (with subordinate pyrite, chalcopyrite, arsenopyrite, and magnetite). The trace element composition of magnetite, which locally forms ore-grade masses and occurs as a common accessory in most rocks types at Stollberg, has previously proven to be a pathfinder in the exploration for ore deposits elsewhere and is evaluated here along with the rare earth element (REE) chemistry of altered rocks. At Stollberg, the dominant country rocks are metamorphosed rhyolitic pumice breccia and rhyolitic ash-silt-sandstone with minor amphibolite sills. On the eastern side of the Stollberg syncline, mineralization at Stollberg and Dammberget occurs as stratabound replacement of limestone/skarn that grades into iron formation spatially related to garnet-biotite and gedrite-albite alteration. At Gränsgruvan on the western side of the syncline, sulfides occur in a silicified zone along with garnet-biotite and quartz-garnet-pyroxene alteration. Although the Tvistbo and Norrgruvan deposits along the north end of the syncline are small, they show geological characteristics that are transitional to deposits found on the western and eastern side of the syncline in that the ore is hosted by skarn rock and associated with quartz-garnet-pyroxene alteration. The Gränsgruvan deposit more closely resembles deposits found at Garpenberg than those located on the eastern limb of the Stollberg syncline. Whole-rock analyses of altered and unaltered host rocks suggest that most components were derived from a felsic volcaniclastic component and that elements were immobile during alteration. These rocks (including altered rocks in the stratigraphic footwall) are light REE enriched, heavy REE depleted, and show negative Eu anomalies, whereas mineralized rocks (Fe- and base metal-rich) and altered rocks in the ore zone show the same REE pattern but with positive Eu anomalies. Trace element compositions (using LA-ICP-MS techniques) of magnetite in high-grade ore, limestone/skarn, massive magnetite, and garnet-biotite, gedrite-albite, garnet-pyroxene alteration show a range of compositions. Such ranges in composition are inconsistent with previous studies in other ore fields that suggest the composition of magnetite can be used to define compositional fields characteristic of ore deposit type (e.g., Al+Mn vs. Ti+V wt. %) or approximate temperature of the ore-forming fluid. Magnetite in garnet-biotite and gedrite-albite alteration spatially associated with Dammberget typically contains > 200 ppm Ga, > 10 ppm Sn, and Ti/V ratios of >10 whereas magnetite in garnet-biotite alteration associated the smaller Cederkreutz deposit contains < 25 ppm Ga, < 2 ppm Sn, and Ti/V ratios < 0.1. Magnetite in garnet-biotite alteration associated with the Gränsgruvan deposit contains > 10 ppm Sn, 20 to 180 ppm Ga, and Ti/V ratios of 0.1 to 2. These and other trace element compositions of magnetite as well as REE patterns of altered host rocks show potential as exploration guides to ore in the Stollberg district.

  • 140.
    Frank, Katherine
    et al.
    Department of Geological and Atmospheric Sciences, Iowa State University.
    Spry, Paul
    Department of Geological and Atmospheric Sciences, Iowa State University.
    Raat, Hein
    Raat Geoservices.
    Allen, Rodney
    Volcanic Resources AB.
    Jansson, Nils
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ripa, Magnus
    Geological Survey of Sweden.
    Variability in the Geological, Mineralogical, and Geochemical Characteristics of Base Metal Sulfide Deposits in the Stollberg Ore Field, Bergslagen District, Sweden2019Ingår i: Economic geology and the bulletin of the Society of Economic Geologists, ISSN 0361-0128, E-ISSN 1554-0774, Vol. 114, nr 3, s. 473-512Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Stollberg ore field occurs in the Bergslagen region of south-central Sweden, a polydeformed ca. 1.9 Ga igneous province dominated by bimodal felsic and mafic rocks. Sulfide mineralization is hosted by metavolcanic rocks, marble, and skarn and consists of massive to semimassive polymetallic sulfides and iron oxide in a semiregional F2 syncline termed the Stollberg syncline. The dominant country rocks are rhyolitic pumice breccia and rhyolitic ash-siltstone with minor mafic sills metamorphosed to the amphibolite facies. On the eastern limb of the Stollberg syncline, sulfide mineralization occurs as stratabound premetamorphic replacement of volcaniclastic rocks and limestone that grades into iron formation. The development of skarn assemblages is the result of low-temperature replacement of limestone and volcaniclastic rocks rather than formation by high-temperature metasomatism or synmetamorphic or late hydrothermal replacement of marble. Metamorphosed, hydrothermally altered rocks on the eastern limb are dominated by the assemblages garnet-biotite and gedrite-albite. Silica-altered rocks are generally subordinate in the Stollberg ore field; however, sulfides at Gränsgruvan, on the western limb of the syncline, are located in a silicified zone along with metamorphosed, altered rocks dominated by sericite and the assemblage quartz-garnet-pyroxene. Although the Tvistbo and Norrgruvan prospects along the northern end of the syncline are small, they show geologic characteristics that are transitional to deposits found on the western and eastern limbs of the syncline. Ore at Tvistbo is hosted by skarn and is spatially associated with quartz-garnet-pyroxene rocks, whereas sulfides at Norrgruvan are hosted by quartz-fluorite rocks that are similar to those hosting the Brusgruvan deposit on the eastern limb of the syncline.

    Whole-rock analyses of variably altered host rocks in the Stollberg ore field suggest that most components were sourced from felsic volcaniclastic rocks and that Zr, Ti, Al, Hf, Nb, Sc, Th, Ga, U, and rare-earth elements (REEs) were immobile during alteration. These rocks are enriched in light REEs, depleted in heavy REEs, and have negative Eu anomalies, whereas sulfide-bearing rocks (Fe- and base metal-rich) and altered rocks in the ore zone show the same REE pattern but with positive Eu anomalies. Indicators of proximity to sulfides in altered rocks in the Stollberg ore field include positive Eu anomalies, an increase in the concentration of Pb, Sb, As, Tl, Ba, Ba/Sr, and K2O, as well as an increase in a modified version of the Ishikawa alteration index, which accounts for the presence of primary Ca in an original limestone component. Garnet and pyroxene enriched in either Ca or Mn are also considered to be pathfinders to ore. Cooling of an acidic, reduced hydrothermal fluid that carried sulfur and metals, which became neutralized as it reacted with limestone, is likely responsible for the formation of sulfides in the Stollberg ore field. The nature of the host rock types, the style of the alteration spatially associated with sulfide mineralization, and the spatial association with iron formation bear some resemblance to volcanogenic massive sulfide and Broken Hill-type deposits. However, the stratabound replacement of limestone by sulfides distinguishes it from these deposit types and is a so-called SVALS-type ore system, which is a class of stratabound, volcanic-hosted, limestone-skarn deposits restricted to the Bergslagen district.

  • 141.
    Friborg, Johan
    Luleå tekniska universitet.
    A computerized album of Slingram scale-model curves for rapid interpretation on a PC by a matching technique1994Ingår i: First Break, ISSN 0263-5046, E-ISSN 1365-2397, Vol. 12, nr 6, s. 317-319Artikel i tidskrift (Refereegranskat)
  • 142.
    Friedrichs, Heiko
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    The host rock succession of the Hornträskmassive sulfide deposit in the Rävliden orehorizon, Skellefte District, Sweden2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 143.
    Frietsch, Rudyard
    Luleå tekniska universitet.
    Formation of Mg-bearing magnetite and serpentine in skarn iron ores in northern Sweden1984Ingår i: Geologiska föreningens i Stockholm förhandlingar, ISSN 0016-786X, Vol. 106, nr 3, s. 219-230Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper deals with the formation of magnetite in connection with sulphurization and serpentinization of skarn iron ores in Early Proterozoic (1.9 Ga) metasediments and mafic metavolcanics in northern Sweden. The ores contain Ca-Mg and Mg silicates which are characterized by a high Mg/(Mg + Fe) ratio, being mainly higher than 0.8. This feature is possibly due to an original high content of sulphur in the chemically precipitated ore material. During regional metamorphism involving heat transfer and recrystallization there occurred internal reactions. Sulphur reacting with primary, more Fe-rich silicates, gave rise to more Mg-rich silicates and a simultaneous formation of iron sulphides and magnetite. Calculations made on the Stora Sahavaara ore show, however, that the sulphide-silicate reactions could only have attributed to relatively restricted amounts of magnetite. The magnetite of the ores often contains small amounts of magnesium, at maximum 6 weight% Mg. The magnesium-bearing magnetite is mostly associated with serpentine which is an alteration product of olivine, tremolite and diopside. The occurrence of the magnesium-bearing magnetite is attributed to serpentinization which released iron from the silicates, and their high magnesium/iron ratio could in part be related to this process. However, the formation of magnetite in connection with serpentinization is only known in some deposits, and it is therefore plausible that serpentinization, in similarity with the sulphide-silicate reactions, has given rise to restricted amounts of magnetite in comparison to the amount of magnetite (or its precursor) which was deposited as a primary chemical precipitate.

  • 144.
    Frietsch, Rudyard
    Luleå tekniska universitet.
    On the magmatic origin of iron ores of the Kiruna type: reply1984Ingår i: Economic geology and the bulletin of the Society of Economic Geologists, ISSN 0361-0128, E-ISSN 1554-0774, Vol. 79, nr 8, s. 1949-1951Artikel i tidskrift (Övrigt vetenskapligt)
  • 145.
    Frietsch, Rudyard
    Luleå tekniska universitet.
    Preface: Ore geology related to prospecting : a national Swedish research programme1994Ingår i: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 29, nr 2, s. 110-Artikel i tidskrift (Övrigt vetenskapligt)
  • 146.
    Frietsch, Rudyard
    Luleå tekniska universitet.
    The Kiruna iron ores1989Ingår i: Abstracts with programs (Geological Society of America), ISSN 0016-7592, Vol. 21, nr 6, s. A33-Artikel i tidskrift (Övrigt vetenskapligt)
  • 147.
    Frietsch, Rudyard
    Luleå tekniska universitet.
    The Lannavaara iron ores, northern Sweden1985Rapport (Övrigt vetenskapligt)
  • 148.
    Frietsch, Rudyard
    et al.
    Luleå tekniska universitet.
    Billström, K.
    Laboratory for Isotope Geology. Swedish Museum of Natural History, Stockholm.
    Perdahl, Jan-Anders
    Luleå tekniska universitet.
    Sulphur isotopes in Lower Proterozoic iron and sulphide ores in northern Sweden1995Ingår i: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 30, nr 3-4, s. 275-284Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present investigation deals with sulphur isotope distribution in Lower Proterozoic iron and sulphide mineralizations in northern Sweden. The contrasting sulphur isotope patterns are indicative of different genesis. Some 267 sulphur isotope analyses of pyrite, pyrrhotite, chalcopyrite, sphalerite, galena and bornite from 23 occurrences have been performed. Some deposits exhibit uniform compositions, although the mean δ34S values are clearly different, while other mineralizations have widely fluctuating values. The δ34S values in syngenetic, exhalative sedimentary skarn iron ores, quartz-banded iron ores and sulphide mineralizations of the 2.0-2.5 Ga old (Lapponian) Greenstone group show a large spread, supporting the existence of bacteriogenic sulphate reduction processes. The spread of the sulphur isotope values (δ34S = -8 to +25‰), and the non-equilibrium conditions, point to a biogenic rather than to an inorganic reduction of seawater sulphate. The isotopic composition of the sulphides in the epigenetic Lannavaara iron ores which were formed by a hydrothermal scapolite-tourmalme-related process, indicates a sulphur source similar to that of the Greenstone group. The δ34S values of Cu-(Au) sulphide mineralizations in the Malmberget region (e.g. Aitik), which were formed by a similar process and hosted by the volcanics-volcanoclastics of the 1.9 Ga old Porphyry group, are slightly below zero ‰, indicating a magmatic origin. The existence of different sulphur compositions for these mineralization types formed by a similar hydrothermal process, probably reflects the influence of the host rock, the solutions leaching pre-existing sulphides. In southern Norrbotten, epigenetic, Cu-Zn-Pb veintype mineralizations in metavolcanics and metasediments have δ34S values close to zero ‰ indicating a magmatic origin. The sulphur isotope data of the volcanogenic, massive sulphide ores of the Skellefte district, in particular the ores of the Adak dome, are close to zero ‰. The lead and sulphur isotopic features of the sulphides in northern Sweden show that the ore-forming processes were of a different nature on both sides of the Archean-Proterozoic border, implying differences in the crustal development. Lead isotopes show that lead was mobilized from specific sources on each side of the border. The sulphur of the sulphides in the Greenstone group in NE Sweden and Finland was introduced by sedimentary processes, whereas the sulphur of the sulphide occurrences towards the SW, mainly in the Porphyry group, is dominated by a magmatic sulphur component

  • 149.
    Frietsch, Rudyard
    et al.
    Luleå tekniska universitet.
    Perdahl, Jan-Anders
    Luleå tekniska universitet.
    Rare earth elements in apatite and magnetite in Kiruna-type iron ores and some other iron ore types1995Ingår i: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 9, nr 6, s. 489-510Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An investigation has been conducted to determine the content and distribution of REE in apatite and magnetite in the iron ores of Kiruna type and some other iron ores. The purpose of this article is to discuss the results obtained from the investigation. In particular, it will be shown that REE in apatite and magnetite in different ore types exhibit characteristic patterns related to different modes of formation of the ores

  • 150.
    Frietsch, Rudyard
    et al.
    Luleå tekniska universitet.
    Tuisku, Pekka
    Martinsson, Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Perdahl, Jan-Anders
    Luleå tekniska universitet.
    Early Proterozoic Cu-(Au) and Fe ore deposits associated with regional Na-Cl metasomatism in northern Fennoscandia1997Ingår i: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 12, nr 1, s. 1-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Scapolite is widely distributed in 1.9-2.5 Ga volcano-sedimentary rocks and 1.77-2.2 Ga igneous rocks over several hundred square kilometres in northern Fennoscandia, comprising northern Sweden, northern Finland and adjacent parts of Norway and Russia. This region is one of the largest scapolite-bearing Precambrian terranes in the world. Albitization, and to a lesser extent carbonatization, phyllic and tourmaline alteration, are spatially associated with scapolite. A number of epigenetic Cu-(Au) sulphide and Fe oxide deposits in northern Fennoscandia show a spatial and genetic relationship to this type of alteration, mainly scapolitization and albitization. The main metal occurrences are in 2.0-2.5 Ga mafic volcanics and sediments of the Lapponian Greenstone group and in 1.9 Ga intermediate-composition volcanic and volcaniclastic rocks of the Svecofennian Porphyry group. The scapolite is mainly a dipyre-mizzonite with Cl and CO3 and small amounts of SO4 and F, indicating high Na and Cl activity at the time of crystallization. Fluid inclusion data of the Lapponian Pahtohavare and similar Cu-Au deposits indicate formation temperatures of about 300°C and ore deposition from highly saline aqueous solutions. The deposition of copper and gold was in places regulated by a redox barrier; graphite in associated schists controlled the reduction reactions of the ore fluids and metals were precipitated. The Lapponian and Svecofennian sulphide deposits contain tourmaline of the schorl-dravite series. Aitik-Nautanen Cu-(Au) style deposits and in particular some deposits with vein-style iron ore, contain dravite-schorl deficient in Al and enriched in Fe3+, which is due to Fe-Al substitution in an oxidizing, relatively iron-rich environment. Scapolite and, probably also tourmaline, formed by a complex, multistage process. The source of the components in scapolite may have been evaporitic sequences or high salinity brines in Lapponian rift basins that contain 2.0-2.5 Ga mafic volcanics. During low to medium-grade (low P) regional metamorphism, the components that formed scapolite and tourmaline were mobilized and transported to their present positions in several metasomatic phases. Fault zones with fractures and breccias channeled the fluids, resulting in locally developed intense alteration. Gold and copper was transported by saline, high fO2, high temperature solutions as metal-chloride complexes. The ultimate source of fluids and heat sources is uncertain, but deep-seated crustal magmatic processes seem prerequisite. The alteration occurred mainly around 1.9 Ga at the peak of the main regional metamorphism and the intrusion of granitoids through to around 1.8 Ga. Cu-(Au) sulphide and Fe oxide ore deposits associated with large-scale scapolite-forming metasomatic processes are found elsewhere in the world (e.g., Australia, Kazakhstan, Russia) and show similarities with the Cu-(Au) deposits in northern Fennoscandia. However, the close genetic connection between scapolite-albite and ore formation of Fennoscandian deposits is not a common feature in other belts

1234567 101 - 150 av 542
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf