The Rävliden mine is located in the Skellefte district in northern Sweden. In close proximity lays the Kristineberg deposit containing zinc, copper and lead ore which has been mined since the 1940’s. The district is rich in massive sulphide deposits and the mining history can be dated back to the 1920’s. New deposits are still being discovered and understanding the origin of the ores and their formation processes are more and more important when looking for new orebodies. The area itself is ca 1.8 Ga and most rocks have undergone hydrothermal alteration and been metamorphosed. The main purpose of this study was to determine the host rock protolith and the method chosen was developed by MacLean and Barrett (2005) in which immobile element ratios are used for determining the chemostratigraphy.     Two main alteration types are recognized and two minor ones. The dominant ones being sericite and chlorite alteration. The boreholes also display some silicification and carbonate alteration. While the TAS-diagram shows that most samples are either dacitic or rhyolitic with a small group of andesitic rocks. Further usage of both the Alteration box plot and various immobile element plots show that the amount of dacitic samples are low. Instead rhyolite is the predominant rock type with four subgroups, there is also one dacite group and one probable andesitic intrusion. The mineralisation is low so it was not possible to correlate alteration type to ore occurrence, nor was it possible to see any correlation between protolith and mineralisation. The study did determine the protolith for the boreholes and the data and therefore the method can be used for exploration in other areas. / Rävlidengruvan ligger i Skelleftedistriktet i norra Sverige och i dess närhet ligger även  Kritinebergsgruvan där zink, koppar och bly har brutits ur malmkroppen sedan 1940-talet. Distriktet är rikt på massiva sulfid avlagringar och gruvdrift i området kan dateras tillbaka till 1920-talet. Nya fyndigheter upptäcks fortfarande och förståelse för deras uppkomst och malmernas bildningsprocesser blir är allt viktigare när man ska söka nya malmkroppar. Skelleftedistriktet är ca 1,8 Ga och de flesta bergarter har antingen genomgått metamorfos eller hydrotermal omvandling. Huvudsyftet med denna studie var att fastställa ursprungsbergarten för området, innan hydrotermal omvandling skedde, med hjälp av en metod som har utvecklats av MacLean och Barrett. Metoden grundar sig i att man jämför relationerna mellan immobila grundämnen för att på så sätt fastställa kemostratigrafin.     Fyra omvandlingstyper återfinns i borrhålen där två är mer prominenta, serecit och klorit omvandling. De mindre vanliga omvandlingstyperna är silicifiering eller kvartsomvandlig samt karbonatomvandling. De flesta prover är antingen daciter eller ryoliter med en liten grupp andesiter så visar de olika diagrammen med immobila elementet på att mängden daciter är få. Istället finns det fyra typer av ryoliter, en grupp daciter och en trolig andesitisk intrusion. Mängden mineralisering var låg så det var inte möjligt att korrelera omvandlingstyp till malm bildning, inte heller var det möjligt att se något samband mellan protoliten och mineralisering. Studien besvarade hypotesen om ursprungsbergarten för borrhålen och metoden kan användas för andra prospekteringsområden.

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The Rävliden North deposit (Rävliden N) is a volcanogenic massive sulphide (VMS) deposit in the western part of the Skellefte district, northern Sweden. The district is one of Sweden’s major metallogenic provinces with a significant amount of VMS deposits. The Rävliden N deposit, discovered in 2011, contains copper, zinc, lead, silver and subordinate gold and occurs close to the largest VMS deposit in the district, the Kristineberg deposit, which has been mined for more than 70 years. The purpose of this master thesis is to study the composition, mineralogy and paragenetic relationships in different types of sulphide mineralization from the Rävliden N deposit. Emphasis is placed on characterizing the distribution and paragenetic relationships of silver-bearing minerals. The methods include core logging, sampling and mineralogical studies through light optical microscopy (LOM), scanning electron microscopy (SEM) and quantitative evaluation of mineralogy by scanning electron microscopy (QEMSCAN). Lastly, electron microprobe analysis (EMPA) was used to determine the chemical composition of silver-bearing minerals and sulphides. Mineralization types studied include 1: the main massive to semi-massive sulphide mineralization, 2: stratigraphically underlying stringer mineralization and 3: local, vein- and/or fault-hosted silver-rich mineralization in the stratigraphic hanging wall. The massive to semi-massive sulphide mineralization is dominated by sphalerite with lesser galena and pyrrhotite. In contrast, the stringer mineralization is dominated by chalcopyrite and pyrrhotite. The major minerals show evidence of a coeval formation and textural as well as structural evidence suggest that ductile deformation has affected the mineralization types. Notable evidence includes ball-ore textures, accumulation of minerals in pressure shadows and brittle fracturing of competent arsenopyrite and pyrite porphyroblasts and infilling by more incompetent sulphide minerals. The silver-bearing minerals identified are commonly spatially associated with galena and the major species is freibergite ((Ag,Cu,Fe)12(Sb,As)4S13), which also occur as inclusions in chalcopyrite mainly in the stringer mineralization. The stringer mineralization also contains notable amounts of hessite (Ag2Te). Notably, galena, pyrrhotite, freibergite and other sulphosalt minerals are commonly accumulated in pressure shadows near host rock fragments in the massive to semi-massive sulphide mineralization. The only gold-bearing mineral identified in this study is electrum (Au, Ag) in the stringer mineralization. The hanging wall mineralization locally comprises faulted and/or sheared massive sulphide mineralization which is compositionally similar to the main massive to semi-massive sulphide mineralization, besides a significantly higher content of freibergite. However, parts of the hanging wall mineralization are entirely dominated by sulphides and sulphosalts of silver, such as pyrargyrite (Ag3SbS3), pyrostilpnite (Ag3SbS3), argentopyrite (AgFe2S4), sternbergite (AgFe2S3) and stephanite (Ag5SbS4). These occur in structurally late settings, which along with consideration of their temperature stabilities suggest a late origin. Since the silver-bearing minerals in the massive to semi-massive sulphide mineralization and the two varieties of hanging wall mineralization contains the same metals, the mineralization in the hanging wall may have formed by late-stage remobilization of ore components from the underlying Rävliden N deposit. This negates the need for multiple mineralization events to explain the local silver-enriched zones in the hanging wall. The paragenetically late mineralization types contains high content of Ag-bearing minerals in relation to base metal sulphides. This suggests that remobilisation processes were important for locally upgrading the Ag-content.