The polymetallic Hornkullen deposit is situated in the western part of the Bergslagen ore province, Sweden. It is hosted by an inlier of approximately 1.90-1.88 Ga Svecofennian volcanic and sedimentary metasupracrustal rocks enclosed in a significantly younger, c. 1.8 Ga TIB granitoid (Filipstad granite). Although being mined intermittently for silver during the last 100s of years in addition to been the subject for more recent exploration work, the genesis of this deposit and others in a similar geological position is poorly understood. The hypothesis is that the Hornkullen deposit represents a metamorphically overprinted, syn-volcanic Svecofennian mineralisation. The main ore assemblage comprises magnetite, pyrrhotite, galena, chalcopyrite and arsenopyrite with subordinate pyrite, sphalerite, ilmenite and löllingite. Pb-Fe-Ag-Sb sulphosalts include boulangerite, meneghinite, jamesonite, freibergite-tetrahedrite, pyrargyrite, and stephanite, which mainly occur in trace amounts. Gudmundite and molybdenite are rare accessories. Generally, galena, chalcopyrite and pyrrhotite have accommodated strain in a ductile manner. Locally, this can also be seen in boulangerite, meneghinite and sphalerite. Magnetite, arsenopyrite and pyrite frequently have been deformed in a brittle way. The contrast in competence resulted in the remobilisation of the more ductile minerals into fractures in the more competent minerals. In massive parts, this contrast also resulted in more fragmented clasts of competent minerals within a less competent matrix, similar to “ball ore” texture. Recrystallisation is particularly evident in magnetite and pyrrhotite but also seen in coarser aggregates of ilmenite. Additionally, these minerals and also pyrite and arsenopyrite frequently exhibit euhedral morphology when occurring within less ductile minerals. Inclusions of ore minerals in porphyroblastic garnet are abundant. Geothermobarometry of arsenopyrite and sphalerite suggests temperatures and pressures of 525°C (between 440°C and c. 590°C) and c. 300-400 MPa, consistent with regional Svecokarelian amphibolite facies metamorphism, albeit with some caveats. Fluid inclusion entrapment conditions were determined to c. 440°C (between 400°C and 600°C) and c. 280 MPa. The observed textures are a result of deformation and remobilisation of diverse ore minerals during the Svecokarelian orogeny. Remobilisation was possibly initiated during prograde metamorphism, followed by additional and more extensive modification during retrograde conditions, at least to temperatures below 200°C. Sulphosalt formation is considered to reflect an evolution from prograde through retrograde metamorphism, although most of them formed during the retrograde stage, including the Ag-minerals. No evidence for any additional introduction of elements from later TIB magmatism is present. The combined observations can most easily be reconciled with a metamorphically overprinted syn-volcanic Svecofennian mineralisation. / Den polymetalliska mineraliseringen vid Hornkullen är belägen i västra Bergslagen i Mellansverige. Den uppträder i ca. 1,90-1,88 miljarder år gamla Svekofenniska metavulkaniska- och sedimentära ytbergarter inneslutna i en yngre, ca. 1,8 miljarder år gammal intrusiv bergart, så kallad Filipstadsgranit. Trots att mineraliseringen ganska nyligen varit ett mål för prospektering samt tidigare brutits på silver, saknas fortfarande information om dess malmmineralogi och hur den bildats. Hypotesen är att Hornkullen utgörs av en metamorft överpräglad synvulkanisk Svekofennisk mineralisering. Den domineras av magnetit, magnetkis, blyglans, kopparkis och arsenikkis och i mindre mängd pyrit, zinkblände, ilmenit och löllingit. Pb-Fe-Ag-Sb-sulfosalter finns lokalt och inkluderar boulangerit, meneghinit, jamesonit, freibergit-tetrahedrit, pyrargyrit, och stephanit. Gudmundit och molybdenglans är andra sällsynta accessoriska malmmineral. Blyglans, kopparkis och magnetkis har deformerats plastiskt men lokalt också boulangerit, meneghinit och zinkblände. Magnetit, arsenikkis och pyrit har deformerats sprött. Denna tydliga skillnad i kompetens har resulterat i att inkompetenta mineral ommobiliserats och kommit att fylla sprickor i de mer kompetenta mineralen. I massiva delar av mineraliseringen har denna skillnad även resulterat i en textur av kulmalmstyp. Granoblastisk omkristallisering är särskilt tydligt i magnetit och magnetkis, men även i grovkorniga aggregat av ilmenit. Vidare så förekommer dessa mineral liksom pyrit och arsenikkis ofta som euhedrala kristaller i mindre kompetent matrix. Inneslutningar av malmmineral i porfyroblastisk granat är vanligt förekommande. Geotermobarometri på arsenikkis och zinkblände gav temperatur och tryck på 525°C (mellan 440°C och ca. 590°C) och ca. 300-400 MPa, vilket överensstämmer med regional Svekokarelsk amfibolitfaciesmetamorfos. Förhållandena vid infångandet av synmetamorfa vätskeinneslutningar har uppskattats till en temperatur på ca. 440°C (mellan 400 och 600°C) och tryck på ca. 280 MPa. Merparten av de observerade texturerna är resultat av deformation och ommobilisering relaterad till de förhållanden som rådde under den Svekokarelska orogenesen. Ommobiliseringen av vissa mineral startades förmodligen redan under prograd metamorfos, vilket sedan följdes av mer omfattande modifikation under retrograda förhållanden, åtminstone till temperaturer under 200°C. Bildningen av sulfosalter reflekterar en utveckling från prograd till retrograd metamorfos där de flesta bildats under den senare, retrograda fasen, däribland de olika silvermineralen. Alla observationer resulterar sammantaget i tolkningen att Hornkullen är en regional-metamorft överpräglad och deformerad synvulkanisk Svekofennisk mineralisering.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Em trabalho de prospecção geoquímica regional por concentrado de bateia (PEREIRA e SANTOS, 1983) foi evidenciado na região de Cacaria, município de Piraí, ocorrências de scheelita. Com o objetivo de investigar a possível fonte litológica desta ocorrência, foram realizadas amostragens de sedimentos de corrente e concentrado de bateia além de investigações de campo para sua fonte. Elaborouse ainda um mapa geológico em escala de detalhe 1:25.000. As unidades estratigráficas base utilizadas no mapa foram definidas em trabalhos da empresa RIOFINEX (1977) durante pesquisas para mineralizações de Pb-Zn na região de Rio Claro. Ensaios laboratoriais envolvendo descrição de lâminas petrográficas, difratometria de raios X, fluorescência de raios X, espectrometria Raman, microscopia eletrônica de varredura e o auxílio do mineralight de ondas curtas. As mineralizações scheelitíferas encontradas foram classificadas segundo um modelo do tipo sedimentar exalativo, localmente com possíveis contribuições de atividades metassomáticas tardias, concentrando a mineralização, assim como proposto para algumas ocorrências já descritas no nordeste brasileiro. / In a mineral exploration panning concentrate programme PEREIRA AND SANTOS (1985) identified in the Cacaria region, near the Piraí City, occurences of scheelite. With the objective to investigate the lithological origin of this mineral a nonsystematic sampling by stream sediments and panning concentrate, was carried out to identify the tungsten mineralization source. A geological map was also executed at detailed scale of 1:25.000. The stratigraphic division applied to this map was defined in projects of RIOFINEX (1977) company during investigation of Pb-Zn mineralization in Rio Claro. Laboratorial trials involving description of petrography, Xray diffraction, X-ray fluorescence, Raman spectroscopy, electronic microscopy scanning and short wave mineralight. The scheelite-bearing mineralization was classified according to a exhalative sedimentary model with possible contributions of a late metasomatic activities concentrating the mineralization as proposed for some occurrences observed in northeast part of Brazil.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Em trabalho de prospecção geoquímica regional por concentrado de bateia (PEREIRA e SANTOS, 1983) foi evidenciado na região de Cacaria, município de Piraí, ocorrências de scheelita. Com o objetivo de investigar a possível fonte litológica desta ocorrência, foram realizadas amostragens de sedimentos de corrente e concentrado de bateia além de investigações de campo para sua fonte. Elaborouse ainda um mapa geológico em escala de detalhe 1:25.000. As unidades estratigráficas base utilizadas no mapa foram definidas em trabalhos da empresa RIOFINEX (1977) durante pesquisas para mineralizações de Pb-Zn na região de Rio Claro. Ensaios laboratoriais envolvendo descrição de lâminas petrográficas, difratometria de raios X, fluorescência de raios X, espectrometria Raman, microscopia eletrônica de varredura e o auxílio do mineralight de ondas curtas. As mineralizações scheelitíferas encontradas foram classificadas segundo um modelo do tipo sedimentar exalativo, localmente com possíveis contribuições de atividades metassomáticas tardias, concentrando a mineralização, assim como proposto para algumas ocorrências já descritas no nordeste brasileiro. / In a mineral exploration panning concentrate programme PEREIRA AND SANTOS (1985) identified in the Cacaria region, near the Piraí City, occurences of scheelite. With the objective to investigate the lithological origin of this mineral a nonsystematic sampling by stream sediments and panning concentrate, was carried out to identify the tungsten mineralization source. A geological map was also executed at detailed scale of 1:25.000. The stratigraphic division applied to this map was defined in projects of RIOFINEX (1977) company during investigation of Pb-Zn mineralization in Rio Claro. Laboratorial trials involving description of petrography, Xray diffraction, X-ray fluorescence, Raman spectroscopy, electronic microscopy scanning and short wave mineralight. The scheelite-bearing mineralization was classified according to a exhalative sedimentary model with possible contributions of a late metasomatic activities concentrating the mineralization as proposed for some occurrences observed in northeast part of Brazil.

<p> The East South C (E.S.C.) ore zone at the Dickenson Mine, Red Lake, is a major auriferous banded sulphide orebody which cross-cuts sulphide facies banded iron formation (S.F.B.I.F.) near its eastern termination. Pyrite was obtained from sulphide-rich portions of the ore zone as well as from sulphide-poor E.S.C. mineralization not spatially associated with S.F.B.I.F., S.F.BI.F., shear zone hosted mineralization such as the 1492 and F ore zones, and from quartz-carbonate vein mineralization in the South C ore zone. Forty-three pyrite separates from the zones were analyzed by Atomic Absorption Spectrophotometry for Co and Ni, in order to determine the origin of the E.S.C. ore zone. The average Ni and Co content of these pyrites are as follows: S.F.B.I.F.,7.9 and 13.6 ppm respectively; remobilized S.F.B.I.F. 10.3 and 13.6; carbonatized S.F.B.I.F. 10.9 and 22.6; South C 14.9 and 50.6; 1492 zone 34.1 and 28.4; F-zone 11.2-27.6; sulphide-poor E.S.C. 26.2 and 48.4 and sulphide-rich E.S.C., 17.91 and 16.63.</p> <p> High and variable Co values were found to be associated with carbonate-rich samples, irrespective of the type of mineralization and low and similar Co values were found in all carbonate-poor samples irrespective of their origin. Therefore, the Co content of pyrite cannot be used as a discriminant of genetically dissimilar pyrite. The Ni content in pyrite from S.F.B.I.F. is low and constant, while in shear zone and vein mineralization it is higher and more variable. The E.S.C. ore zone has similar values to that found in the epigenetic mineralization, however, a few sulphide-rich samples are similar to those found in S.F.B.I.F., suggesting a bimodal source of sulphide for the E.S.C.. It is proposed that the hydrothermal system which produced the E.S.C., 1492, F and South C ore zones, locally incorporated sulphides from the S.F.B.I.F. to produce the sulphide-rich mineralization found at the eastern extremity of the E.S.C. ore zone.</p> / Thesis / Bachelor of Science (BSc)