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The Aitik Cu-Au-Ag deposit in the Gallivare area in northern Sweden is Sweden's largest sulphide mine with an annual production of 35 Mt of ore, and the biggest open pit operation in northern Europe. It is proposed in the present study that the Aitik deposit represents a Palaeoproterozoic, strongly metamorphosed porphyry copper deposit that was affected ca. 100 Ma later by a regional IOCG-type hydrothermal event. Consequently, the Aitik deposit might represent a mixed ore system where an early copper mineralisation of porphyry type has been overprinted by later regional IOCG mineralisation. Several attempts have previously been made to genetically classify the Aitik Cu-Au-Ag deposit as a distinct ore type. New geochemical, petrographic, structural, and fluid inclusion results combined with published data have provided the opportunity to present new ideas on the genesis and evolution of the Aitik Cu-Au-Ag deposit. The emplacement of a ca. 1.9 Ga quartz monzodiorite that host the ore at Aitik was related to subduction processes and volcanic arc formation, and synchronous with quartz vein stockwork formation and porphyry copper mineralisation. Highly saline aqueous (38 wt.% NaCl) fluid inclusions in the stockwork veins suggest entrapment at 300 degrees C and a pressure of nearly 3 kbar, a high pressure for a typical porphyry copper ore, but consistent with conditions at associated deep root zones of intrusion-related magmatic-hydrothermal systems. The highly saline fluid formed disseminated and vein-type ore of mainly chalcopyrite and pyrite within comagmatic volcaniclastic rocks, and caused potassic alteration (biotite, microcline) of the host rocks. The early porphyry copper mineralising event was followed, and largely overprinted, by CO2 and aqueous medium- to high-salinity (16-57 wt.% salts) fluids related to a ca. 1.8 Ga tectonic and metamorphic event (peak conditions 500-600 degrees C and 4-5 kbar). Extensive deformation of rocks and redistribution of metals occu, AuthorCount:4

Deposits that may have an affinity with iron oxide-copper-gold (IOCG) deposits in the Archaean and Palaeoproterozoic shield, which includes a large part of Finland, NW Russia, Norway and Sweden, include apatite-iron ore, skarn-related Fe/banded-iron formation (BIF), and epigenetic (or syngenetic) Au/Cu-Au. Apatite-iron ore deposits include the huge Kiirunavaara and Malmberget magmatic deposits, both subjected to deformation and hydrothermal overprinting, while at Tjarrojakka separate examples of both iron oxide-apatite and IOCG may be genetically related, formed epigenetically at around 1.77 Ga. Svecofennian skarn-related Fe- rich deposits, dating from 1.9-1.8 Ga and hosted by c.2.1 Ga greenstones along the border between Sweden and Finland, are accompanied by Au and Cu concentration in Finland but are basically only Fe in the Swedish occurrences. Typically epigenetic Cu and Cu-Au may be grouped into orogenic gold, orogenic gold with atypical metal association, and more obvious IOCG types. Early genetic processes are assumed to have involved concentration of Fe and Cu, with some Au, in 2.3-2.0 Ga supracrustal rocks and deposition of evaporites, before Svecofennian deformation and metamorphism mobilised saline and metal-rich fluids that precipitated varying combinations of ore minerals. A tentative E-W zoning is suggested from the Kuusamo region's possibly syngenetic Au-Co-Cu+/-U through the Central Lapland greenstone belt's orogenic Au and Pajala-Kolari region's skarn-related occurrences to the IOCG and apatite-iron oxide deposits of the Kiruna-Gallivare region of Sweden., Deposits that may have an affinity with iron oxide-copper-gold (IOCG) deposits in the Archaean and Palaeoproterozoic shield, which includes a large part of Finland, NW Russia, Norway and Sweden, include apatite-iron ore, skarn-related Fe/banded-iron formation (BIF), and epigenetic (or syngenetic) Au/Cu-Au. Apatite-iron ore deposits include the huge Kiirunavaara and Malmberget magmatic deposits, both subjected to deformation and hydrothermal overprinting, while at Tjarrojakka separate examples of both iron oxide-apatite and IOCG may be genetically related, formed epigenetically at around 1.77 Ga. Svecofennian skarn-related Fe- rich deposits, dating from 1.9-1.8 Ga and hosted by c.2.1 Ga greenstones along the border between Sweden and Finland, are accompanied by Au and Cu concentration in Finland but are basically only Fe in the Swedish occurrences. Typically epigenetic Cu and Cu-Au may be grouped into orogenic gold, orogenic gold with atypical metal association, and more obvious IOCG types. Early genetic processes are assumed to have involved concentration of Fe and Cu, with some Au, in 2.3-2.0 Ga supracrustal rocks and deposition of evaporites, before Svecofennian deformation and metamorphism mobilised saline and metal-rich fluids that precipitated varying combinations of ore minerals. A tentative E-W zoning is suggested from the Kuusamo region's possibly syngenetic Au-Co-Cu+/-U through the Central Lapland greenstone belt's orogenic Au and Pajala-Kolari region's skarn-related occurrences to the IOCG and apatite-iron oxide deposits of the Kiruna-Gallivare region of Sweden.

An investigation is presented of geochemical processes taking place in abandoned Cu-W skarn tailings from the Smaltjarnen impoundment at Yxsjoberg mine site, Ljusnarsberg, Vastmanland, Sweden using 87Sr/86Sr isotope ratios, strontium concentrations and chemical composition of the tailings, ore minerals and water-soluble tailings leachates, and mineralogy of the tailings. Sampling was carried out in 2016 and involved collecting drill cores using percussion drilling and geoprobe at four locations. The results show that, in the tailings, the 87Sr/86Sr ratio ranges from 0.84787-1.26640, 0.92660-1.06788 and 0.76452-1.05169 in the oxidised, transition and unoxidised zones, respectively, and, in the leachates, the corresponding ranges are 2.4479-5.87552, 1.37404-1.68844 and 1.03697-2.16340. In the water-soluble phase of the oxidised zone, the radiogenic 87Sr/86Sr ratios are indicative of weathering of biotite, K-feldspar and muscovite; in the transition zone, which lies below the oxidised zone, the 87Sr/86Sr ratios in the water-soluble phase are indicative of dissolution of helvine; in the water-soluble phase of the upper part of the unoxidised zone, which lies beneath the transition zone, the 87Sr/86Sr ratios are indicative of dissolution of gypsum; and, in the lower part of the unoxidised zone, the 87Sr/86Sr ratios and tungsten concentrations are indicative of scheelite weathering and possible biotite weathering and groundwater., An investigation is presented of geochemical processes taking place in abandoned Cu-W skarn tailings from the Smaltjarnen impoundment at Yxsjoberg mine site, Ljusnarsberg, Vastmanland, Sweden using 87Sr/86Sr isotope ratios, strontium concentrations and chemical composition of the tailings, ore minerals and water-soluble tailings leachates, and mineralogy of the tailings. Sampling was carried out in 2016 and involved collecting drill cores using percussion drilling and geoprobe at four locations. The results show that, in the tailings, the 87Sr/86Sr ratio ranges from 0.84787-1.26640, 0.92660-1.06788 and 0.76452-1.05169 in the oxidised, transition and unoxidised zones, respectively, and, in the leachates, the corresponding ranges are 2.4479-5.87552, 1.37404-1.68844 and 1.03697-2.16340. In the water-soluble phase of the oxidised zone, the radiogenic 87Sr/86Sr ratios are indicative of weathering of biotite, K-feldspar and muscovite; in the transition zone, which lies below the oxidised zone, the 87Sr/86Sr ratios in the water-soluble phase are indicative of dissolution of helvine; in the water-soluble phase of the upper part of the unoxidised zone, which lies beneath the transition zone, the 87Sr/86Sr ratios are indicative of dissolution of gypsum; and, in the lower part of the unoxidised zone, the 87Sr/86Sr ratios and tungsten concentrations are indicative of scheelite weathering and possible biotite weathering and groundwater.

The Swedish Palaeoproterozoic is intensely mineralised. In the north, 2.5-2.0 Ga greenstone belts and 1.89 Ga terrestrial volcanic and sedimentary rocks host syngenetic Cu-(Zn) deposits, epigenetic Cu-Au deposits and apatite iron ores. The greenstones were formed in rifts within the Archaean crust, while the 1.89 Ga terrestrial volcanic rocks were probably emplaced in a continental volcanic arc setting in response to subduction in the south where the juvenile Skellefte volcanic arc was forming. This volcanic arc hosts numerous massive sulphide, epithermal and porphyry Cu-Au deposits which are related to the early stages of the arc's evolution. After accretion towards the Archaean continent and crustal thickening, several mesothermal gold lode type deposits were formed, possibly at around 1.80 Ga, in structurally favourable settings., The Swedish Palaeoproterozoic is intensely mineralised. In the north, 2.5-2.0 Ga greenstone belts and 1.89 Ga terrestrial volcanic and sedimentary rocks host syngenetic Cu-(Zn) deposits, epigenetic Cu-Au deposits and apatite iron ores. The greenstones were formed in rifts within the Archaean crust, while the 1.89 Ga terrestrial volcanic rocks were probably emplaced in a continental volcanic arc setting in response to subduction in the south where the juvenile Skellefte volcanic arc was forming. This volcanic arc hosts numerous massive sulphide, epithermal and porphyry Cu-Au deposits which are related to the early stages of the arc's evolution. After accretion towards the Archaean continent and crustal thickening, several mesothermal gold lode type deposits were formed, possibly at around 1.80 Ga, in structurally favourable settings.

The host rocks of the Aitik Cu-Au deposit consist of plutonic and volcanic rocks, the latter strongly altered and deformed. To deduce the tectonic origin of the host rocks, a comparison is presented with the widespread volcanic and plutonic rocks generated during the Svecofennian orogeny in the continental domain north of the Skellefte district. The Porphyrite Group of volcanic rocks, and the Haparanda Suite of granitoids, which were both previously interpreted as subduction-related, are chemically similar to the Aitik rocks, showing a calc-alkaline, intermediate composition. The Aitik rocks were probably formed in a compressional environment in a volcanic arc setting, corresponding to the period of subduction (at around 1.9 Ga) in the Skellefte district., The host rocks of the Aitik Cu-Au deposit consist of plutonic and volcanic rocks, the latter strongly altered and deformed. To deduce the tectonic origin of the host rocks, a comparison is presented with the widespread volcanic and plutonic rocks generated during the Svecofennian orogeny in the continental domain north of the Skellefte district. The Porphyrite Group of volcanic rocks, and the Haparanda Suite of granitoids, which were both previously interpreted as subduction-related, are chemically similar to the Aitik rocks, showing a calc-alkaline, intermediate composition. The Aitik rocks were probably formed in a compressional environment in a volcanic arc setting, corresponding to the period of subduction (at around 1.9 Ga) in the Skellefte district.

Aitak is a disseminated copper-gold deposit with 18 000 000 tonnes/a production of ore containing 0.38% copper and 0.22 ppm gold, in metamorphosed volcanic and sedimentary rocks formed in a volcanic arc environment. The mineralised areas trend NE-SW and N-S and plunge NE (Au) and NNW (Cu). The ore body shows both vertical and horizontal metal zoning, with massive chalcopyrite veins near the footwall and rich dissemination in the centre. This may be the result of both primary mineralisation and secondary mobilisation of metals, but possibly also derives from repeated introduction of metals., Aitak is a disseminated copper-gold deposit with 18 000 000 tonnes/a production of ore containing 0.38% copper and 0.22 ppm gold, in metamorphosed volcanic and sedimentary rocks formed in a volcanic arc environment. The mineralised areas trend NE-SW and N-S and plunge NE (Au) and NNW (Cu). The ore body shows both vertical and horizontal metal zoning, with massive chalcopyrite veins near the footwall and rich dissemination in the centre. This may be the result of both primary mineralisation and secondary mobilisation of metals, but possibly also derives from repeated introduction of metals.

The work includes the main thesis (19pp., 128 refs.) and three papers to be submitted to Precambrian Research, Economic Geology and Mineralium Deposita: Palaeoproterozoic greenstones at Kiruna in northern Sweden - a product of continental rifting and associated mafic-ultramafic volcanism, 49pp., 191 refs.; Viscaria - a syngenetic exhalative Cu-deposit in the Palaeoproterozoic Kiruna greenstones, 57pp., 145 refs.; and Pahtohavare - an epigenetic Cu-Au deposit in the Palaeoproterozoic Kiruna greenstones, 37pp., 71 refs. The strata of the Kiruna Greenstone Group change from clastic sediments, evaporites and flood basalts to volcaniclastic rocks and then voluminous mid-ocean ridge basalt pillow lavas. Both types of sulphide deposit formed from highly saline hydrothermal fluids, possibly originating in the underlying evaporites. The layered Viscaria strucure suggests repeated exhalative activity and deposition in rift-controlled brine pools, while Pahtohavare ores were controlled by black shales in zones of active ductile to brittle shearing., The work includes the main thesis (19pp., 128 refs.) and three papers to be submitted to Precambrian Research, Economic Geology and Mineralium Deposita: Palaeoproterozoic greenstones at Kiruna in northern Sweden - a product of continental rifting and associated mafic-ultramafic volcanism, 49pp., 191 refs.; Viscaria - a syngenetic exhalative Cu-deposit in the Palaeoproterozoic Kiruna greenstones, 57pp., 145 refs.; and Pahtohavare - an epigenetic Cu-Au deposit in the Palaeoproterozoic Kiruna greenstones, 37pp., 71 refs. The strata of the Kiruna Greenstone Group change from clastic sediments, evaporites and flood basalts to volcaniclastic rocks and then voluminous mid-ocean ridge basalt pillow lavas. Both types of sulphide deposit formed from highly saline hydrothermal fluids, possibly originating in the underlying evaporites. The layered Viscaria strucure suggests repeated exhalative activity and deposition in rift-controlled brine pools, while Pahtohavare ores were controlled by black shales in zones of active ductile to brittle shearing.

Four main and three minor rare-earth-element (REE)-bearing minerals were identified and quantified in the Kiirunavaara apatite iron ore tailings using optical microscopy, an electron probe microanalyser (EPMA) and a mineral liberation analyser, and their chemical compositions were analysed by the EPMA and laser ablation inductively coupled plasma-mass spectrometry. REEs are shown to be contained in the minerals apatite, monazite, allanite, titanite, zircon, thorite and synchysite. In zircon, thorite and synchysite, they occurred in only trace amounts and contributed limited amounts to the total REE budget, and these are consequently of minor importance. Monazite occurred as inclusions in apatite and as free particles, 90% liberated. Allanite occurred to some degree in mixed grains with magnetite but also as free particles. Monazite mainly reported to the apatite concentrate, while allanite and titanite largely went to the tailings, the latter preferably to those fractions smaller than 38 micron. The amount of titanite in the finest tailings fraction was 2.3 wt%, containing close to 1% REEs, with heavy rare earth elements (HREEs) making up 28% of the total REEs. However, a texturally distinct group of titanite grains showed an HREE/REE ratio of up to 67%. Furthermore, titanium dioxide analysis indicates that titanite is preferentially released into the tailings from the secondary magnetic separation step in the concentrator. It is therefore suggested that titanite, occasionally enriched in HREEs, can be extracted from the processing stream and might thus be considered a new source for REEs at Kiirunavaara and similar deposits. (Authors.), Four main and three minor rare-earth-element (REE)-bearing minerals were identified and quantified in the Kiirunavaara apatite iron ore tailings using optical microscopy, an electron probe microanalyser (EPMA) and a mineral liberation analyser, and their chemical compositions were analysed by the EPMA and laser ablation inductively coupled plasma-mass spectrometry. REEs are shown to be contained in the minerals apatite, monazite, allanite, titanite, zircon, thorite and synchysite. In zircon, thorite and synchysite, they occurred in only trace amounts and contributed limited amounts to the total REE budget, and these are consequently of minor importance. Monazite occurred as inclusions in apatite and as free particles, 90% liberated. Allanite occurred to some degree in mixed grains with magnetite but also as free particles. Monazite mainly reported to the apatite concentrate, while allanite and titanite largely went to the tailings, the latter preferably to those fractions smaller than 38 micron. The amount of titanite in the finest tailings fraction was 2.3 wt%, containing close to 1% REEs, with heavy rare earth elements (HREEs) making up 28% of the total REEs. However, a texturally distinct group of titanite grains showed an HREE/REE ratio of up to 67%. Furthermore, titanium dioxide analysis indicates that titanite is preferentially released into the tailings from the secondary magnetic separation step in the concentrator. It is therefore suggested that titanite, occasionally enriched in HREEs, can be extracted from the processing stream and might thus be considered a new source for REEs at Kiirunavaara and similar deposits. (Authors.)

High spatial resolution zircon U-Pb geochronological data obtained directly on the Kiirunavaara iron oxide-apatite deposit, related orebodies, and host rocks provide new constraints on the timing of mineralisation in these deposits. These data raise new arguments in the debate of a magmatic versus hydrothermal/metasomatic genesis of these major (2 500 Mt, 30-70 wt% Fe) Palaeoproterozoic deposits. The main orebody at Kiirunavaara contains Ti-poor magnetite and minor (0.05-5 wt% P) apatite, located between a trachyandesite footwall and a rhyodacite hanging wall, which also hosts smaller orebodies (Nukutus, Rektorn, and Tuolluvaara). The pervasive Na and K metasomatism in the host rock is documented by whole-rock geochemical data and cathodoluminescence microscopy. Zircon U-Pb data for the metavolcanic rocks in the footwall and hanging wall cluster between 1 884 ± 4 and 1 880 ± 3 Ma. In the footwall, a syenite-aplite system yields ages of 1 880 ± 7 and 1 881 ± 4 Ma; a granite pluton exposed underground has an age of 1 874 ± 4 Ma. Zircons in two ore samples, never directly dated before this study, yield ages of 1 877 ± 4 and 1 874 ± 7 Ma. Brecciation at the contacts between the ore and host rocks, the tight age at ca. 1 880 Ma for most volcanic and plutonic rocks in the footwall and hanging wall, and the marginally younger age for ore at ca. 1 877 to 74 Ma, matching the age of the spatially related granite pluton, suggest a magmatic-hydrothermal emplacement model for the Kiruna ores. (Authors.), High spatial resolution zircon U-Pb geochronological data obtained directly on the Kiirunavaara iron oxide-apatite deposit, related orebodies, and host rocks provide new constraints on the timing of mineralisation in these deposits. These data raise new arguments in the debate of a magmatic versus hydrothermal/metasomatic genesis of these major (2 500 Mt, 30-70 wt% Fe) Palaeoproterozoic deposits. The main orebody at Kiirunavaara contains Ti-poor magnetite and minor (0.05-5 wt% P) apatite, located between a trachyandesite footwall and a rhyodacite hanging wall, which also hosts smaller orebodies (Nukutus, Rektorn, and Tuolluvaara). The pervasive Na and K metasomatism in the host rock is documented by whole-rock geochemical data and cathodoluminescence microscopy. Zircon U-Pb data for the metavolcanic rocks in the footwall and hanging wall cluster between 1 884 ± 4 and 1 880 ± 3 Ma. In the footwall, a syenite-aplite system yields ages of 1 880 ± 7 and 1 881 ± 4 Ma; a granite pluton exposed underground has an age of 1 874 ± 4 Ma. Zircons in two ore samples, never directly dated before this study, yield ages of 1 877 ± 4 and 1 874 ± 7 Ma. Brecciation at the contacts between the ore and host rocks, the tight age at ca. 1 880 Ma for most volcanic and plutonic rocks in the footwall and hanging wall, and the marginally younger age for ore at ca. 1 877 to 74 Ma, matching the age of the spatially related granite pluton, suggest a magmatic-hydrothermal emplacement model for the Kiruna ores. (Authors.)

Northern Fennoscandia (northern Sweden, northern Finland and adjacent parts of Norway and Russia) is one of the largest scapolite-bearing Precambrian terranes in the world. Albitisation, carbonatisation, phyllic and tourmaline alteration are spatially associated with the scapolite, which is mainly a dipyre-mizzonite with Cl and CO3 and small amounts of SO4 and F. Fluid inclusion data indicate formation temperatures of about 300 degrees C and ore deposition from highly saline aqueous solutions. The deposition of Cu and Au was regulated by a redox barrier in places; graphite-associated schists controlled the reduction reactions of the ore fluids and metals were precipitated. The source of the components in scapolite may have been evaporitic sequences or high salinity brines in rift basins. During low- to medium-grade regional metamorphism, the components were mobilised and transported, with the fluids being channelled by fault zones with fractures and breccias., Northern Fennoscandia (northern Sweden, northern Finland and adjacent parts of Norway and Russia) is one of the largest scapolite-bearing Precambrian terranes in the world. Albitisation, carbonatisation, phyllic and tourmaline alteration are spatially associated with the scapolite, which is mainly a dipyre-mizzonite with Cl and CO3 and small amounts of SO4 and F. Fluid inclusion data indicate formation temperatures of about 300 degrees C and ore deposition from highly saline aqueous solutions. The deposition of Cu and Au was regulated by a redox barrier in places; graphite-associated schists controlled the reduction reactions of the ore fluids and metals were precipitated. The source of the components in scapolite may have been evaporitic sequences or high salinity brines in rift basins. During low- to medium-grade regional metamorphism, the components were mobilised and transported, with the fluids being channelled by fault zones with fractures and breccias.