De sulfidgruvor belägna i Långbantrakten som studien behandlar ligger i den västra delen av Bergslagen utanför Filipstad i Värmlands län. Opaka mineral (malm) från två mindre mineraliseringar, Näset och Getberget, har studerats med malmmikroskop och mikrosond för att beskriva mineralogin i området. Båda områdena domineras av olika (Cu-Fe-Pb-Zn)-sulfider, i Näset av kopparkis (CuFeS2), blyglans (PbS) och zinkblände ((Zn,Fe)S) och i Getberget av blyglans, zinkblände, kubanit (CuFe2S3) och magnetkis (Fe1-xS). I Näset finns en del mindre frekventa mineral, två olika faser av Co-pentlandit (en nickelrik och en utan nickel), gedigen Sb och Bi, (Ni-Co)-sulfid, breithauptit (NiSb) och magnetkis. Kubanit är även ett viktigt mineral som speglar mineraliseringens bildning. I Getberget finns liknande mindre frekventa mineral, kopparkis, nickelrik Co-pentlandit, gedigen Bi och Sb, silverglans (Ag2S), breithauptit och magnetit (Fe3O4). En sen utfällning av kubanit har skett i båda områdena och visar att mineraliseringarna har genomgått en liknande bildning och det stämmer även in på mineralogin, som även den är likartad. / The small sulphide mines, Näset and Getberget that have been investigated are located just outside the main mineralization of Långban, near the city of Filipstad in Värmland County. Opaque minerals have been studied in reflected light microscopy and with an electron microprobe analysis to describe the mineralogy. Both areas are dominated by various (Cu-Fe-Pb-Zn)-sulphides, Näset with chalcopyrite (CuFeS2), galena (PbS) and sphalerite ((Zn,Fe)S) and Getberget with, galena, sphalerite, cubanite (CuFe2S3) and pyrrhotite (Fe1-xS). The sulphides are also accompanied by various accessory minerals, in Näset by two different phases of Co-pentlandite (on rich in nickel and one without), native Sb and Bi, a (Ni-Co)-sulphide, breithauptite (NiSb) and pyrrhotite. Cubanite is also a very important mineral that reflects the formation of the mineralization. In Getberget there are similar accessory minerals, chalcopyrite, nickel rich Co-pentlandite, native Bi and Sb, acanthite (Ag2S), breithauptite and magnetite (Fe3O4). A late precipitation of cubanite has occurred in both areas, suggesting that the mineralizations has been formed in similar conditions. This also holds true when comparing the mineralogy, which also is similar.

This work focuses on crustal interaction in magmatic systems, drawing on experimental petrology and elemental and isotope geochemistry. Various magma-chamber processes such as magma-mixing, fractional crystallisation and magma-crust interaction are explored throughout the papers comprising the thesis. Emphasis is placed on gaining insights into the extent of crustal contamination in ocean island magmas from the Canary Islands and the processes of magma-crust interaction observed both in nature and in experiments. This research underscores that the compositions of ocean island magmas, even primitive types which are classically used as probes of the mantle, are susceptible to modification by crustal contamination. The principal mechanisms of contamination identified from work on both Tenerife and Gran Canaria (Canary Islands) are assimilation and partial melting of the pre-existing island edifice and intercalated sediments by newly arriving magma (i.e. “island recycling”). The information that we can gain from studying solidified magma and entrained crustal xenoliths concerning the rates and mechanisms of crustal assimilation is, however, limited. To address this shortcoming, a series of time-variable crustal carbonate assimilation experiments were carried out at magmatic pressure and temperature using natural materials from Merapi volcano, Indonesia. A temporally constrained reaction series of carbonate assimilation in magma has hence been constructed. The experiments were analysed using in-situ techniques to observe the progressive textural, elemental, and isotopic evolution of magma-carbonate interaction. Crucially, carbonate assimilation was found to liberate voluminous crustally-derived CO2 on a timescale of only seconds to minutes in the experiments. This points to the role of rapid crustal degassing in volcanic volatile budgets, and, pertinently, in magnifying hazardous volcanic behaviour. This thesis, therefore, delivers detailed insights into the processes of magma-crust interaction from experiments and geochemistry. The outcomes confirm that crustal processes are significant factors in both, i) ocean island magma genesis, and ii) magma differentiation towards compositions with greater explosive potential which can, in turn, manifest as hazardous volcanism. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 707