Magmatic stoping is a term that has been controversial almost since it was first mentioned over a century ago. Scientists have been arguing whether it plays an important part as an emplacement process of magma chambers, or whether it takes place at all. With growing evidence for both pro- and counterar guments the debate becomes tenser and the question raised is whether it is possible to find a unanimous answer. Magmatic stoping is often associated with the presence of xenoliths, “foreign” rocks that have been enclosed by magma. As parts of the roof or walls in the magma chamber detach, the pieces become trapped in it if they don’t have time to dissolve before the magma cools. The new cavities make room for a growing chamber and the possibility for magmatic stoping to be a volumetrically significant process is as well in discussion. The problematic starts early, beginning with the definitions of words like stoping, xenoliths, and rafts which are not unified. Natural findings of xenoliths in plutons are rare and speak against stoping but are often explained by xenoliths that possibly sunk down to the floor of magma chambers and become inaccessible for researchers. Nowadays there are several explanations to these statements that will be both presented and discussed in this thesis. A case study is also made from the Åva ring complex in Finland, and it has been shown to provide a fairly clear idea of the evidence for magmatic stoping. With remote sensing xenoliths have been mapped and measured and the results show that magmatic stoping is an abundant process and not something to be dismissed.

Indium is extensively used in LCD screens and solar cells. It is mainly produced as a byproduct during ore processing. With ever increasing demand for indium and most of the production being restricted to a few countries new sources for indium are needed. In Sweden, the westernmost Bergslagen is the only area, which is known to exhibit minerals with essential indium. The indium mineralisations at Långban, the Linbom prospect, which are studied in this bachelor’s thesis show several trends. The most notable is the copper indium trend seen in sphalerite. A likely substitution based on similar ionic radii and charges is Cu1++ In3+ ↔ 2Zn2+.Usually when cassiterite is associated with similar polymetalic indium bearing mineralisations as at Långban there is also high concentrations in cassiterite. This has previously not observed in Sweden, however during this project concentrations were indeed found in cassiterite.

In nature there are about 4,500 minerals identified. These can roughly be divided into two groups, opaque phases and non-opaque phases, with the exception that some opaque phases also may act as a non-opaque phase in different circumstances. The division is made on the basis of the optical properties. Opaque phases are nontransparent, which means that a different type of microscope must be used. A conventional microscope uses transmitted light while the microscope for opaque phases or the ore microscope uses reflected light. The reason is that ore minerals often behave in an opaque manner. An ore mineral is actually a regular mineral but with the difference that it is economically advantageous to mine. Many sulphide and oxide minerals are classified as ore minerals. Sulfide and oxide ores are often associated with a particular type of formation environment and are found in a few areas in Sweden. Bergslagen, Skelleftefältet and Norrbotten belong to these areas. The purpose of this studie is to identify the mineralization from Skyttgruvan and Näverbergsgruvan in Falun by using a microscope. / I naturen finns cirka 4,500 mineral identifierade. Dessa kan grovt sett delas upp i två grupper nämligen opaka faser och icke-opaka faser, då bortses dock från undantaget att vissa opaka faser också kan beteé sig som icke-opaka faser under olika omständigheter. Uppdelningen är gjord utifrån mineralens optiska egenskaper. Opaka faser är icke genomskinliga vilket innebär att en annan typ av mikroskop än de konventionella måste användas. Ett konventionellt mikroskop använder sig av genomfallande ljus samtidigt som mikroskop för opaka faser använder sig av påfallande ljus, ett så kallat malmmikroskop. Anledningen till att de kallas just så är för att malmineral ofta är opaka. Ett malmmineral är egentligen ett vanligt mineral men som är ekonomiskt fördelaktigt att bryta. Idag är många sulfid- och oxidmineral klassade som malmmineral. Sulfid och oxidmineral är ofta associerade med en viss typ av bildningsmiljö. Denna typ av bildningsmiljö går att finna spår av på några platser i Sverige. Bergslagen, Skelleftefältet och Norrbotten hör till dessa områden. Syftet med denna studie är att identifiera de opaka faserna som påträffats i stuffer som samlats in från Skyttgruvan och Näverbergsgruvan.

Svalbard represents the uplifted and exhumed northwest corner of the Barents Sea Shelf. Pre-Carboniferous rocks of Svalbard are divided into the Eastern, Northwestern and Southwestern Terranes, were amalgamated during the Caledonian Orogen and are separated by north-south-trending strike-slip faults. Even though our knowledge of Svalbard’s pre-Carboniferous history has increased dramatically during the last two decades, a major issue remains: Where did the different tectonostratigraphic terranes of Svalbard originate? The answer to this question has profound significance for the entire eastern Laurentian margin, which spans two supercontinent cycles, from the amalgamation and breakup of Rodinia to the amalgamation of Pangea. This thesis constrains the tectonothermal evolution of Svalbard’s Northwestern Terrane (NWT) using ion microprobe and LA-ICP-MS U-Pb zircon geochronology and electron microprobe thermobarometry on metasediments, clastic rocks and granitoids. Detrital zircon age populations of metasediments from the NWT suggests that they (e.g. the Krossfjorden Group) were deposited at c. 1000 Ma in a remnant ocean basin setting outboard the Eastern Grenville Province and were subsequently deformed and intruded by Late Grenvillian granitoids during the final suturing of Rodinia. Thus, a northern branch of the Grenvillian/Sveconorwegian orogeny is not present. This older history of the NWT is extensively overprinted by Late Caledonian deformation and metamorphism, with peak metamorphic conditions of 850 °C at >6 kbars, and subsequent migmatization of the Krossfjorden Group at c. 420 Ma. Based on these data, together with the detrital zircon age population from overlying Late Silurian-Early Devonian clastic rocks, a unifying model is proposed involving fragments from the Grampian orogen and Avalonian crust originally accreted to the Laurentian margin, subsequently transported northwards along sinistral strike-slip faults during Scandian deformation. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: In press.

Den här rapporten beskriver malmbildande processer och Bergslagens malmgeologi. En beskrivning av malmmikroskopet ges tillsammans med identifikationskriterier för de mineral som påträffats i en mikroskopisk studie som gjorts på fyra stuffer från Dammen nära Dannemora, inkluderande vanliga och påträffade malmtexturer. Två av proverna analyserades med mikrosond. / This report gives a description of ore-forming processes and an introduction to Bergslagen ore-geology. The polarization microscope is described together with a number of identification-criteria of specifik minerals found during a study of four geological specimens from Dammen close to Dannemora, including a description of common ore textures. Two of the samples were also analyzed with an electon probe microanalyzer

The origin of apatite iron oxide ores, like the deposit at Grängesberg in the Bergslagen mining district, has been a subject of much discussion through the years. Some support a formation by hydrothermal fluids while others suggest that the ore is orthomagmatic, i.e. formed directly from a magma as suggested for the iron ore deposits of El Laco in Chile or the deposits in Kiruna, although also these two are still subjected to controversies. In 2009 sampling was done on drillcores through the Grängesberg ore. On these samples an oxygen isotope study on magnetite, quartz and whole rock samples from both the ore and its host rocks was conducted in order to obtain new knowledge about the ore forming processes. The data allowed modeling to simulate a possible origin by different magmas or hydrothermal fluids as well as a possible temperature of formation. In addition, the data set was compared to published oxygen isotope analyses of the possible magmatic iron ores of Kiruna and El Laco. The results of the Grängesberg analysis revealed that the ore in the area seems to have an origin from both magmatic and hydrothermal sources.

Improving our understanding of magma plumbing and storage remains one of the majorchallenges for petrologists and volcanologists today. This is especially true for explosivevolcanoes, where constraints on magma plumbing are essential for predicting dynamicchanges in future activity and thus for hazard mitigation. This study aims to investigate themagma plumbing system at Anak Krakatau; the post-collapse cone situated on the rim of the1883 Krakatau caldera. Since 1927, Anak Krakatau has been highly active, growing at a rateof ~8 cm/week. The methods employed are a.) clinopyroxene-melt thermo-barometry (Putirkaet al., 2003; Putirka, 2008), b.) plagioclase-melt thermo-barometry (Putirka, 2005), c.)clinopyroxene composition barometry (Nimis & and Ulmer, 1998; Nimis, 1999; Putirka,2008) and d.) olivine-melt thermometry (Putirka et al., 2007). Previously, both seismic(Harjono et al., 1989) and petrological studies (Camus et al., 1987; Mandeville et al., 1996a;Gardner et al., in review, J. Petrol.) have addressed the magma plumbing beneath AnakKrakatau. Interestingly, petrological studies indicate shallow magma storage in the region of2-8 km, while the seismic evidence points towards a mid-crustal and a deep storage, at 9 and22 km respectively.This study shows that clinopyroxene presently crystallizes in a mid-crustal storage region(8-12 km), a previously identified depth level for magma storage, using seismic methods(Harjono et al., 1989). Plagioclases, in turn, form at shallower depths (4-6 km), in concertwith previous petrological studies (Camus et al., 1987; Mandeville et al., 1996a; Gardner etal., in review, J. Petrol.). Pre-1981 clinopyroxenes record deeper levels of storage (8-22 km),indicating that there may have been an overall shallowing of the plumbing system over thelast ~40 years. The magma storage regions detected coincide with major lithologicalboundaries in the crust, implying that magma ascent and storage at Anak Krakatau is probablycontrolled by crustal discontinuities and/or density contrasts. Therefore, this study shows thatpetrology has the sensitivity to detect magma bodies in the crust where seismic surveys faildue to limited resolution. Combined geophysical and petrological surveys offer an increasedpotential for the thorough characterization of magma plumbing at active volcanic complexes.

The volcanic Island of Fogo that is situated near the end of the southern island chain in the archipelago of Cape Verde is one of the most active oceanic volcanoes in the world. The purpose of this study was to investigate temporal variations in lavas from Fogo by using whole rock major and trace elements and describe trends in magmatic differentiation, melting systematics and mantle source compositions. Further, for the first time Fogo lavas have been investigated by using 18O isotopes, to test for crustal assimilation and source variations. The time span for this study includes one sample of unknown prehistoric age and then from 1799 and onward all eruptions including the most recent in 2014-2015 are covered. The Fogo lavas are mafic, alkali rich, porphyritic, basanite-tephrites dominated by clinopyroxene phenocrysts followed by olivine and opaque phases situated within glass and microcrystalline groundmass.  Fractional crystallization and phenocryst accumulation is important mechanisms for magmatic differentiation, and the best result from fractional crystallization modelling gave a crystallizing assemblage of 20.7 % clinopyroxene, 5.4 % olivine, 4.2 % Fe-Ti oxides and 0.8 % apatite. Temporal variations in MgO content reveal a trend that change from more evolved lavas in older historic eruptions, to more primitive compositions in lavas from the middle of the 19th century, back to more evolved compositions in recent eruptions. Oxygen isotopes of glass and microcrystalline groundmass vary within a normal upper mantle range (δ18O = 5.7±0.3 ‰) which rule out any significant crustal assimilation, and the variations observed for the oxygen isotopes are probably related to source variations as there are tendencies towards covariation with source lithology proxies. Trace element ratios together with high TiO2 contents indicate that pyroxenite is an important source lithology. The Fogo lavas are highly enriched in incompatible elements and utilizing a simple batch melting model suggests ~2-4 % degree of melt for most sampled eruptions. In addition, melting is occurring at high pressures in the presence of residual garnet as the REE are fractionated. Trace element ratios of Ce/Pb and Zr/Y in Fogo lavas are consistent with mixing of a HIMU-like and an EM 1-like mantle source. There are also indications of an increasing involvement of the EM 1-like source through time. Magma mixing is indicated by petrographic observations such as complex zonation patterns and the occurrence of rounded cores in euhedral clinopyroxenes, as well as inferred from a large scatter in certain trace element ratios. / Vulkanön Fogo som ligger nära änden av den sydvästra ökedjan i Kap Verdes skärgård är en av de mest aktiva vulkanerna i världen. Syften med denna studie var att undersöka den kemiska variationen i lava från Fogo över tid och koppla variationen till olika magmatiska processer i vulkanen. Lava från Fogo har dessutom i denna studie för första gången undersökts med hjälp av syreisotoper för att testa för inblandning av material från jordskorpan samt för variationer i manteln i jordens inre där lavan bildas. Denna studie omfattar en tid som sträcker sig från ett förhistoriskt icke tidsbestämt vulkanutbrott, samt från 1799 till och med det senaste utbrottet 2014-2015. Lava från Fogo i denna studie är basisk och relativt magnesiumrik samt rik på alkaliska ämnen och har en porfyrisk textur som innebär att större mineralkorn sitter inbäddade i en finkornig grundmassa. Detta är typiskt för ytliga vulkaniska bergarter som svalnat snabbt. Mineralsammansättningen i lavan domineras av silikatmineralen pyroxen följt av olivin tillsammans med vad som troligen är järn-titan oxider. Dessa mineraler sitter i en grundmassa som består av mikroskopiska mineralkristaller och av glas. Lavan från Fogo har spårämnen som tillsammans med en hög koncentration av titandioxid påvisar att pyroxenit smält i manteln där lavan producerats, till skillnad från peridotit som är vanligare förekommande. Lavan har producerats genom smältning i manteln under relativt högt tryck vilket är typiskt för den här typen av vulkanöar och är dessutom berikad i vissa spårämnen som beror på att bara en liten andel av manteln smält när lavan bildats. En enkel smältningsmodell beräknade att ca 2-4 % smältning av manteln kunde ge de observerade koncentrationerna av spårämnen. Öarna i Kap Verdes skärgård har en geografiskt varierande geokemisk karaktär som beror på att den underliggande manteln består av skilda mantelkomponenter med olika kemisk sammansättning. I lava från den södra ökedjan dit Fogo tillhör ingår en mantelkomponent som saknas i den övriga delen av skärgården. Spårämnen i lava från denna studie överensstämmer med en blandning av dessa mantelkomponenter, dessutom verkar det förekomma en tidsmässig variation av inblandning från respektive komponent. Det finns även bevis för att olika typer av magma blandats från t.ex. mikroskopistudier av mineraltexturer. Resultatet från de analyserade syreisotoperna visar på en variation inom vad som är normalt för övre delen av manteln (5,7 ± 0,3 ‰), vilket utesluter inblandning av större mängder material från jordskorpan. Den variation av syreisotoper som förekommer i lavan beror därför förmodligen på att manteln inte är enhetlig.

Plagioclase is the most abundant mineral in the lower crust and it is thus important to constrain the behaviour of plagioclase during deformation. Anorthosites, which are plagioclase-rich rocks, are common in Archaean cratons but their origin and rheological importance is still debated. The aims of this thesis are to 1) describe a newly discovered Archaean anorthosite complex (Naajat Kuuat, SW Greenland), investigate its origin and a possible genetic relationship between the anorthosite and associated mafic-ultramafic rocks and 2) to study the rheology and deformation mechanisms in plagioclase-rich rocks. The main focus of this thesis is on the deformation studies. (1) Geochemical whole-rock analyses from the Naajat Kuuat complex are indicative for an origin near a subduction zone setting. A genetic link by crystal fractionation between the anorthosite and associated mafic-ultramafic units is inferred. (2) Deformation behaviour of plagioclase is assessed from analyses of three anorthosite units deformed during different conditions. Samples were analysed using the electron backscatter diffraction technique (EBSD) in combination with optical and chemical analyses. All three case studies show significant strain localisation related to grain size reduction. A wet anorthosite deformed at dry conditions (T ~675-700°C) was dynamically recrystallised. Continuous bands of recrystallised grains developed a texture yet display microstructures and grain relationships indicative for grain size sensitive creep, suggesting that the rheology followed a Newtonian flow law. In the other two studies, samples with initially dry and wet composition, respectively, have experienced deformation during fluid present conditions at T ~550-620°C. These two samples show that fluids effectively caused reactions, replacements and aided strain localisation during deformation at mid crustal conditions. / At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 1: Manuscript; Paper 2 Manuscript; Paper 3 Manuscript.

Linking diagenesis to depositional facies and sequence stratigraphy enables better prediction of spatial and temporal distribution of diagenetic alterations, and thus of evolution of reservoir quality in sandstones. This thesis demonstrates that employing this approach is possible because depositional facies and sequence stratigraphy can provide useful information on parameters controlling the near-surface diagenesis, such as changes in: (i) pore-water chemistry, (ii) residence time of sediments under certain geochemical conditions, (iii) detrital composition and proportion of extra- and intra-basinal grains, and (iv) types and amounts of organic matter. Evidence from four case studies enabled the development of conceptual models for distribution of diagenetic alterations and of their impact on evolution of reservoir quality in sandstones deposited in paralic, shallow marine and fluvio-lacustrine environments. Diagenetic alterations that have been constrained within the context of depositional facies and sequence stratigraphy include: (i) carbonate cement (microcrystalline and equant calcite spars dolomite over poikilotopic calcite), pyrite and glaucony are most abundant in progradational braid-delta fan sequences, particularly along the topsets (i.e. maxiumum flooding surface, MFS) and along parasequences boundaries in the deltaic facies of the early highstand systems tract HST, (ii) cementation by coarse spar calcite, dolomite, and the formation of moldic porosity by the dissolution of framework carbonate grains are most abundant in the aggradational fan deltas sequences, (iii) eogenetic kaolinitization of framework silicates is largely restricted to the fluvial and paralic HST sandstones, whereas telogenetic kaolinite may occur in the transgressive systems tract TST sandstones too, (iv) formation of goethite ooids in the TST sediments, (v) formation of glaucony, siderite spherules, and extensive grain-coatings, grain-replacing and ooidal berthierine, more in the TST than in the HST sediments, particularly below the transgressive surface TS and MFS, (vi) cementation by calcite with (δ18OV-PDB = -11.5‰ to -5.4‰) and Fe-dolomite/ankerite (δ18OV-PDB = -10.8‰ to -9.6‰) occurs in both TST and HST sandstones, (vii) syntaxial quartz overgrowths are most extensive in the HST sandstones owing to the presence of incomplete grain-coating berthierine/chlorite, (viii) greater amounts of micro-porosity in the TST sandstones than in the HST sandstones are related to the greater amounts of berthierine/chlorite in the former sandstones, and (ix) chlorite rims around quartz grains retarded the precipitation of quartz overgrowths, and hence prevented a greater loss of primary intergranular porosity in fluvio-lacustrine sandstones. Therefore, constraining the distribution of diagenetic alterations in the contexts of depositional facies and sequence stratigraphic context is a powerful approach to be used in hydrocarbon exploration.