| 1. |
- Frietsch, Rudyard, et al.
(författare)
-
Early Proterozoic Cu-(Au) and Fe ore deposits associated with regional Na-Cl metasomatism in northern Fennoscandia
- 1997
-
Ingår i: Ore Geology Reviews. - 0169-1368 .- 1872-7360. ; 12:1, s. 1-34
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
|
|
| 2. |
- Frietsch, Rudyard, et al.
(författare)
-
Rare earth elements in apatite and magnetite in Kiruna-type iron ores and some other iron ore types
- 1995
-
Ingår i: Ore Geology Reviews. - 0169-1368 .- 1872-7360. ; 9:6, s. 489-510
-
Tidskriftsartikel (refereegranskat)abstract
- 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
|
|
| 3. |
- Aiglsperger, Thomas, et al.
(författare)
-
Critical metals (REE, Sc, PGE) in Ni laterites from Cuba and the Dominican Republic
- 2016
-
Ingår i: Ore Geology Reviews. - : Elsevier. - 0169-1368 .- 1872-7360. ; 73, s. 127-147
-
Tidskriftsartikel (refereegranskat)abstract
- Ni laterites are considered worthy targets for critical metals (CM) exploration as Rare Earth Elements (REE), Sc and platinum group elements (PGE) can be concentrated during weathering as a result of residual and secondary enrichment. In this contribution geochemical and mineralogical data of CM from two different nickel laterite types (i) from the Moa Bay mining area in Cuba (oxide type) and (ii) from the Falcondo mining area in the Dominican Republic (hydrous Mg silicate type) are presented. Emphasis is given on examining their potential to accumulate CM and on processes involved. Results show that CM are concentrated towards the surface in specific zones: (i) REE in clay minerals rich horizons and within zones composed of secondary Mn oxide(s), (ii) Sc within zones rich in secondary Fe and Mn bearing oxide(s) and (iii) PGE in zones with high concentrations of residual chromian spinel and secondary Fe and Mn bearing oxide(s) at upper levels of the Ni laterite profiles. Concentration factors involve (i) residual enrichment by intense weathering, (ii) mobilization of CM during changing Eh and pH conditions with subsequent reprecipitation at favourable geochemical barriers and (iii) interactions between biosphere and limonitic soils at highest levels of the profile (critical zone) with involved neoformation processes. Total contents of CM in both Ni laterite types are low when compared with conventional CM ore deposits but are of economic significance as CM have to be seen as cost inexpensive by-products during the Ni (+ Co) production. Innovative extraction methods currently under development are believed to boost the significance of Ni laterites as future unconventional CM ore deposits.
|
|
| 4. |
- Andersson, Stefan S., et al.
(författare)
-
Mineral paragenesis and sulphide trace element distribution in the metamorphosed Lovisa Zn-Pb deposit, Bergslagen (Sweden), as revealed by 3D X-ray tomography, ore petrography and LA-ICP-MS analysis
- 2022
-
Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368 .- 1872-7360. ; 140
-
Tidskriftsartikel (refereegranskat)abstract
- This study encompasses the ore mineralogy, textures and sulphide trace element chemistry of the Palaeoproterozoic Lovisa stratiform Zn-Pb deposit and the stratigraphically underlying Lovisa Fe Formation in the Bergslagen ore province (Sweden). We investigate the relative timing of formation and subsequent modifications of its ores in relation to the c. 1.87-1.80 Ga Svecokarelian orogeny. The Lovisa Zn-Pb deposit consists of several different ore types. The massive sphalerite-galena ore is distinctly deformed, exhibiting a multiple-scale "ball ore" texture with rounded silicate clasts within a deformed, fine-grained sulphide matrix. Underlying the massive ore is a locally folded, sphalerite-rich laminated ore, interpreted to represent a metamorphosed relict primary lamination. Several generations of sphalerite-galena fracture fillings and veins occur adjacent to the main ore zones and they cross-cut early ductile structures and metamorphic features. The trace element signatures of the sphalerite-galena infillings generally mimic those of the two main ore zones, thus supporting an origin by localised remobilisation of the primary sulphide ore and demonstrating limited trace element redistribution during this process. In contrast, discrete sulphosalt-rich fracture fillings cross-cutting earlier galena-chalcopyriterich fracture fillings and veinlets in the Lovisa Fe Formation suggest a significant but still relatively localised redistribution of metals. Trace element mapping of sulphides from the Lovisa Zn-Pb deposit reveals that inclusion-free overgrowths on pyrite crystals are locally Co-enriched compared to the cores, which resulted from the redistribution of Co during late metamorphic processes. Combined textural and geochemical evidence suggest that the originally syngenetic exhalative sulphide ore at Lovisa was locally strongly affected by polyphase deformation and remobilisation. This was initiated during the first stage of amphibolite facies grade regional metamorphism and deformation (D1, c. 1.87-1.85 Ga) but is mostly evident from the later stages (D2) and the evolution to retrograde and brittle conditions (c. 1.83-1.80 Ga and later).
|
|
| 5. |
- Andersson, Stefan S., et al.
(författare)
-
Origin of the high-temperature Olserum-Djupedal REE-phosphate mineralisation, SE Sweden : A unique contact metamorphic-hydrothermal system
- 2018
-
Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368 .- 1872-7360. ; 101, s. 740-764
-
Tidskriftsartikel (refereegranskat)abstract
- The Swedish part of the Fennoscandian Shield hosts a variety of rare earth element (REE) deposits, including magmatic to magmatic-hydrothermal types. This paper focuses on the origin of the Olserum-Djupedal REEphosphate mineralisation located in the sparsely studied Vastervik region, SE Sweden. Here, mineralisation occurs in three main areas, Olserum, Djupedal and Bersummen. Primary hydrothermal REE mineralisation formed at high temperatures (about 600 degrees C), leading to precipitation of monazite-(Ce), xenotime-(Y), fluor apatite and minor (Y,REE,U,Fe)-(Nb,Ta)-oxides in veins and vein zones dominated by biotite, amphibole, magnetite and quartz. The veins are hosted primarily by metasedimentary rocks present close to, or within, the contact aureole of a local 1.8 Ga ferroan alkali feldspar granite pluton, but also occur within in the chemically most primitive granite in the outermost part of that pluton. In the Djupedal area, REE-mineralised metasedimentary bodies are extensively migmatised, with migmatisation post-dating the main stage of mineralisation. In the Olserum and Bersummen areas, the REE-bearing veins are cross-cut by abundant pegmatitic to granitic dykes. The field-relationships demonstrate a-protracted magmatic evolution of the granitic,pluton and a clear spatial and temporal relationship of the REE mineralisation to the granite. The major and trace element chemistry of ore-associated biotite and magnetite support genetic links between all mineralised areas. Biotite mineral chemistry data further demonstrate a distinct chemical trend from meta sediment-hosted ore-associated biotite distal to the major contact of the granite to the biotite in the granite hosted veins. This trend is characterised by a systematic decrease in Mg and Na and a coupled increase in Fe and Ti with proximity to the granite-hosted veins. The halogen compositions of ore-associated biotite indicate elevated contents of HCl and HF in the primary REE mineralising fluid. Calculated log(f(HF)/f(HCL)) values in the Olserum area suggest a constant ratio of about -1 at temperatures of 650-550 degrees C during the evolution of the primary hydrothermal system. In the Djupedal and Bersummen areas, the fluid locally equilibrated at lower log (f(HF)/f(HCl)) values down to -2. High Na contents in ore-associated biotite and amphibole, and the abundance of primary ore-associated biotite indicate a K- and Na-rich character of the primary REE mineralising fluid and suggest initial high-temperature K-Na metasomatism. With subsequent cooling of the system, the fluid evolved locally to more Ca-rich compositions as indicated by the presence of the Ca-rich minerals allanite-(Ce) and uvitic tourmaline and by the significant calcic alteration of monazite-(Ce). The later Ca-rich stages were probably coeval with low to medium-high temperature (200-500 degrees C) Na-Ca metasomatism variably affecting the granite and the wall rocks, producing distinct white quartz-plagioclase rocks. All observations and data lead us to discard the prevailing model that the REE mineralisation in the Olserum-Djupedal district represents assimilated and remobilised former heavy mineral-rich beds. Instead, we propose that the primary REE mineralisation formed by granite-derived fluids enriched in REE and P that were expelled early during the evolution of a local granitic pluton. The REE mineralisation developed primarily in the contact aureole of this granite and represents the product of a high temperature contact metamorphic-hydrothermal mineralising system. The REE mineralisation probably formed synchronously with K-Na and subsequent Na-Ca metasomatism affecting the granite and the wall rocks. The later Na-Ca metasomatic stage is probably related to a regional Na +/- Ca metasomatic and associated U +/- REE mineralising system operating concurrently with granitic magmatism at c. 1.8 Ga in the Vastervik region. This highlights the potential for discovering hitherto unknown REE deposits and for the reappraisal of already known deposits in this part of the Fennoscandian Shield.
|
|
| 6. |
|
|
| 7. |
- Bark, Glenn, et al.
(författare)
-
Geodynamic settings for Paleoproterozoic gold mineralization in the Svecofennian domain : a tectonic model for the Fäboliden orogenic gold deposit, northern Sweden
- 2012
-
Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368 .- 1872-7360. ; 48, s. 403-412
-
Tidskriftsartikel (refereegranskat)abstract
- Northern Sweden is currently experiencing active exploration within a new gold ore province, the so called Gold Line, situated southwest of the well-known Skellefte VMS District. The largest known deposit in the Gold Line is the hypozonal Fäboliden orogenic gold deposit. Mineralization at Fäboliden is hosted by arsenopyrite-rich quartz veins, in a reverse, mainly dip-slip, high-angle shear zone, in amphibolite facies supracrustal host rocks. The timing of mineralization is estimated, from field relationships, at ca. 1.8 Ga.The gold mineralization is hosted by two sets of mineralized quartz veins, one steep fault-fill vein set and one relatively flat-lying extensional vein set. Ore shoots occur at the intersections between the two vein sets, and both sets could have been generated from the same stress field, during the late stages of the Svecofennian orogen.The tectonic evolution during the 1.9–1.8 Ga Svecofennian orogen is complex, as features typical of both internal and external orogens are indicated. The similarity in geodynamic setting between the contemporary Svecofennian and Trans-Hudson orogens indicate a potential for world-class orogenic gold provinces also in the Svecofennian domain.The Swedish deposits discussed in this paper are all structurally associated with roughly N-S striking shear zones that were active at around 1.8 Ga, when gold-bearing fluids infiltrated structures related to conditions of E-W shortening.
|
|
| 8. |
- Bark, Glenn, et al.
(författare)
-
Orogenic gold in the new Lycksele-Storuman ore province, northern Sweden : the Palaeoproterozoic Fäboliden deposit
- 2007
-
Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368 .- 1872-7360. ; 32:1-2, s. 431-451
-
Tidskriftsartikel (refereegranskat)abstract
- Southwest of the well-known Skellefte District, northern Sweden, a new gold ore province, the so called Gold Line, is presently being explored. During the past decade a number of gold occurrences have been discovered in this area. The largest known gold occurrence is the Fäboliden deposit. Late-to post-orogenic, ca. 1.81 to 1.77 Ga, Revsund granite constitutes the main rock type in the Fäboliden area and surrounds a narrow belt of mineralized metagreywackes and metavolcanic rocks. The supracrustal rocks are strongly deformed within a roughly N-S trending subvertical shear zone. The mineralization constitutes a 30 to 50 m wide, N-S striking, steeply dipping zone. The mineralization is commonly hosted by arsenopyrite-bearing quartz-veins within the supracrustal rocks. The quartz veins parallel the main foliation in the shear zone. Gold is closely associated with arsenopyrite-löllingite and stibnite and found in fractures and as intergrowths in the arsenopyrite-löllingite. Gold is also seen as free grains in the silicate matrix of the host rock. The proximal alteration zone displays positive correlation with Ca, S, As, Ag, Sb, Sn, W, Pb, Bi, Cd, Se, and Hg, whereas K and Na show a slightly negative correlation. The hydrothermal mineral assemblage in the proximal alteration zone is diopside, calcic amphibole, biotite, and minor andalusite and tourmaline. This type of assemblage is commonly recognized in hypozonal orogenic gold deposits worldwide. Garnet-biotite geothermometry indicates amphibolite facies in the Fäboliden area. The ductile fabric that hosts the mineralization is also found in the margin of the surrounding Revsund granitoid. It is therefore suggested that at least the final stages of the gold mineralization are syn- to late-kinematic, and the minimum age for the mineralization is thus constrained at ca. 1.80 Ga (Revsund age).
|
|
| 9. |
- Bauer, Tobias, Associate professor, 1982-, et al.
(författare)
-
Regional structural setting of late-orogenic IOCG mineralization along the northern Nautanen deformation zone, Norrbotten, Sweden
- 2023
-
Ingår i: Ore Geology Reviews. - : Elsevier. - 0169-1368 .- 1872-7360. ; 163
-
Tidskriftsartikel (refereegranskat)abstract
- The northern Norrbotten ore province in Sweden is one of the most mineralized areas in Europe. Iron, gold and/or copper deposits occur as iron oxide-apatite-style mineralization (IOA, Kiruna-type) as well as iron oxide-copper–gold (IOCG) style. Regardless of mineralization style, most deposits appear to be spatially controlled by a set of crustal-scale Palaeoproterozoic shear zones which share similar structural characteristics and deformation histories.Reappraisal of regional geological and geophysical data, coupled with structural mapping, suggests crustal-scale shear zones form continuous c. N-S-trending zones extending from the Skellefte district in the south into the northern Norrbotten ore province. One example from Norrbotten is a zone that extends SSW from Karesuando in the north towards Svappavaara. While this structure has traditionally been inferred to continue SW towards Arjeplog (i.e. the Karesuando – Arjeplog Deformation Zone; KADZ), we favour its deflection SSE into the Nautanen-Aitik trend, making it a continuous, IOCG-bearing, crustal-scale deformation zone. Similar shear zone geometries can be observed in analogous zones to the west. Most of these crustal scale structures record at least two time-separated deformation events of regional significance. IOA and IOCG deposits form in different tectonic environments, separated in time and overprinting each other.
|
|
| 10. |
- Bernet, Matthias, et al.
(författare)
-
Multidisciplinary petro-geo-thermochronological approach to ore deposit exploration
- 2019
-
Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368. ; 112:Sept.
-
Forskningsöversikt (refereegranskat)abstract
- The continuous search for mineral resources such as gold, copper and base metals etc. requires a refined understanding of the thermal evolution and exhumation history of potential exploration targets, as only ore deposits can be exploited that have been exhumed to the surface or near to the surface. In order to better understand the exhumation history of the ore deposits a multidisciplinary approach using single grain geo- and thermochronology double/triple dating in combination with other geochemical, fluid inclusion and petrological analyses, can significantly support prospecting for such resources, particularly in frontier areas, where little geological information exists. Geo-thermochronology provides information on the timing of initial host rock crystallization, ore deposit formation and subsequent exhumation as the thermal history can be modelled and exhumation rates can be determined. Here we present a methodological outline on which single-grain double/triple-dating techniques can be used, what sampling strategies may be applied, and how the data may be interpreted.
|
|
