Under en berggrundsgeologisk fältkurs år 2007 påträffandes spodumenförande granitpegmatitblock i området kring Bergby-Hamrånge, denna händelse markerade starten på det prospekteringsarbete efter Litium-Cesium-Tantal-pegmatiter som sedan skedde i området. Allteftersom prospekteringsarbetet fortlöpt i området har det framkommit allt fler indikationer på att den rådande berggrundskartans (SGU:s karta Ai 28) geologiska gränsdragningar kan uppdateras och justeras. Den borrdata som samlats in i samband med prospekteringsarbetet har sammanställts och sedan använts i Seequents programvara Leapfrog Geo för att skapa 3D-modeller över områdets LCT- och granitpegmatiter samt berggrund.Modelleringen av berggrunden med tillhörande geologiska enheters gränser och påverkan av lokala deformationszoner har varit begränsad till de områden där prospektering genomförts och har lett fram till slutsatsen att den nuvarande kartan till viss del kan uppdateras. LCT-pegmatiternas geografiska utbredning har tillfogats till den geologiska modellen och kan adderas till berggrundskartans omtolkningar då denna tidigare saknade granitpegmatiter. Avslutningsvis har uppsatsen bidragit med att ge en ökad förståelse av den lokala geologin inom Bergby-Hamrånge. / During a bedrock geology field course in 2007, spodumene-bearing granite pegmatite blocks were encountered in the area around Bergby-Hamrånge, this event marked the start of the exploration work for Lithium-Cesium-Tantalum pegmatites that then took place in the area. As exploration work has continued in the area, more and more indications have emerged that the geological boundaries of the current bedrock map (SGU's map Ai 28) can be updated and adjusted. The drill data collected in connection with the exploration work has been compiled and then used in Seequent's Leapfrog Geo software to create 3D models of the area's LCT and granite pegmatites and bedrock. The modeling of the bedrock with associated geological unit boundaries and the influence of local deformation zones has been limited to the areas where exploration has been carried out and has led to the conclusion that the current map can be updated to some extent. The geographical distribution of the LCT pegmatites has been added to the geological model and can be added to the reinterpretations of the bedrock map as it previously lacked granite pegmatites. In conclusion, the essay has contributed to an increased understanding of the local geology within Bergby-Hamrånge.

The work presented in this thesis utilizes several geological methods to investigate the origin and evolution of the supracrustal rocks in the Palaeoproterozoic Hamrånge Group (HG) in the south-central Swedish Svecofennian. The first paper is based on whole-rock geochemistry to show the plate tectonic setting of volcanic rocks within the HG. This indicates that the environment was probably an oceanic volcanic arc. Geochronology, used in paper two, shows that the volcanism was active at 1888±6 Ma and that the sediments forming the stratigraphically overlying quartzite were deposited after 1855±10 Ma, with provenance ages overlapping both the volcanic rocks and the 1.86-1.84 Ga continental margin Ljusdal granitoids. In the third paper, thermobarometry was applied to samples from the HG, the migmatitic Ockelbo sub-domain to the south, and the 1.81 Ga Hagsta Gneiss Zone (HGZ) that separate these two units. The results show distinct differences in the metamorphic conditions that have affected the HG and the Ockelbo sub-domain, supporting previous interpretations that the HGZ is an important crustal structure, possibly a terrane or domain boundary. Paper four deals with the structural geology of the Hamrånge area. The study shows that the volcanic rocks and the underlying mica schist have been subjected to three deformation episodes (D1-D3), while the uppermost quartzite was most likely only affected by D2 and D3. While structures related to D1 are rarely seen, D2 resulted in a penetrative foliation, strong lineations and NW-vergent folding and thrusting. D3 is a result of a N-S compression that formed regional E-W folds and steep, ca. NW-SE shear zones, e.g. the HGZ. The results presented in this thesis, integrated with previously published data, outline a model for the geological evolution of the Hamrånge area: At 1.89 Ga a volcanic arc formed that subsequently collided with a continental margin resulting in the first deformation episode, D1, and probably a metamorphic event. This was possibly followed by an extensional period, after 1855±10 Ma, forming a basin that accumulated sediments later to form the quartzite stratigraphically on top of the volcanic rocks. The second deformation episode, D2, formed a fold-thrust belt when the supracrustal HG was thrusted to the NW, on top of the 1.86-1-84 Ga Ljusdal Domain. Flattening and a second metamorphic period followed this thickening of the crust. The last ductile deformation, D3, caused by regional tectonic forces, resulted in F3-folds that matured into ca. 1.8 Ga large-scale, steep shear zones transecting the Fennoscandian Shield.

Spårelementkoncentrationen i polerprov av kvarts från Bergby-Hamrångeområdet har analyserats genom LA-ICP-MS. Spårelementkoncentrationen i kvarts från enkla pegmatiter och LCT-pegmatiter har analyserats och registrerat koncentrationer för 23 olika isotoper. Koncentrationerna för Al27, Ti49, Li7, Rb85 och B11 hos 84 provpunkter har plottats i tvåaxliga-diagram. Tertiära diagram av Al/10-Li-Ti och Ti-Al/10-Rb*50 har sammanställts och i dessa har fält för LCT-pegmatiter markerats ut baserat på data från Müller m.fl. (2021). I rapporten beskrivs LA-ICP-MS översiktligt för läsare utan tidigare erfarenhet. Syftet med undersökningen var att besvara, 1) Om kvarts i polerproverna från BergbyHamrånge kan klassas som ultraren och 2) Att diskutera spårelementkoncentrationerna och undersöka alternativa användningsområden för kvarts som inte är ultraren. / The trace element concentration in pole samples of quartz from the Bergby-Hamrånge area has been analyzed by LA-ICP-MS. The trace element concentration in quartz from simple pegmatites and LCT-pegmatites has been analyzed and recorded concentrations for 23 different isotopes. Concentrations of Al27, Ti49, Li7, Rb85 and B11 at 84 sample points have been plotted in biaxial graphs. Tertiary diagrams of Al/10-Li-Ti and Ti-Al/10-Rb*50 have been compiled and in these, fields for LCT-pegmatites have been highlighted based on data from Müller et al. (2021). The report demands no previous knowledge of LA-ICP-MS to be understood. The purpose of the investigation was to answer, 1) If quartz samples from Bergby-Hamrånge can be classified as ultrapure quartz and 2) To discuss the trace element concentrations and investigate alternative uses for quartz that is not ultrapure.