This thesis focuses on the geochemistry of secondary minerals, mainly calcite but also others such as fluorite and Ca/Al silicates, precipitated throughout the last 1.5 billion years in fractures of crystalline rock, SE Sweden. The work was based on previous reconnaissance studies and has been possible thanks to access to high-quality drill cores and associated mapping data provided by the Swedish Nuclear Fuel and Waste Management Co (SKB). Concentrations of rare earth elements (REEs) and occasionally other metals were determined in a variety of secondary minerals from fractures (mainly open systems) and veins (mainly sealed systems) and in primary minerals from the bedrock. Stable-isotope composition was measured in the secondary minerals. The overall aim was to define the sources, uptake and fractionation of REEs in calcite, and a few other co-genetic minerals, precipitated throughout the geological history under conditions ranging from hydrothermal to low temperatures. Collectively, the findings of the individual studies show that there is no easy and straightforward control of REE abundance and fractionation in calcite and other minerals in fractures and veins in crystalline bedrock settings. For example, the REE features in calcite vary extensively within sub-generations of single vein-precipitating events, on micro scale in transects across individual veins, and unsystematically over the geological history characterised by successively decreasing temperatures of mineral formation. Although the REE content in, and release from, the crystalline bedrock can have an influence on REE distribution in calcite and other minerals, it is of overall minor importance within a given bedrock domain. The main advantage of determining REEs in secondary minerals in fractures and veins in crystalline rock is therefore, as revealed in this work, to assess the character and evolution of the conditions (including features of the paleofluids) during confined mineral-precipitating events.

The aim of this thesis is to determine the sources, controls and risk aspects of fluoride in surface water and groundwater in a region of southeastern Sweden where the fluorine-rich 1.45 Ga circular Götemar granite (5 km in diameter) crops out in the surrounding 1.8 Ga granites and quartz monzodiorites (TIB rocks). The materials of this thesis include both primary data, collected for the purpose of this thesis, and a large set of secondary data, retrieved from the Swedish Nuclear Fuel and Waste Management Co., the Swedish Geological Survey and the Kalmar County Council. A characteristic feature of the area is high fluoride concentrations in all kinds of natural waters, including surface waters (such as streams) and groundwater in both the Quaternary deposits (regolith groundwater) and bedrock fractures (fracture groundwater). A number of potential sources and controls of the high fluoride concentrations were investigated, including a variety of geological, mineralogical, mineral-chemical and hydrological features and processes. For the stream waters and regolith groundwater, high fluoride concentrations were correlated with the location of the Götemar granite. This finding is explained by the discharge of fluoride-rich groundwater from fractures in the bedrock and/or the release of fluoride due to the weathering of fluorine-bearing minerals in the Quaternary deposits; however, the Quaternary deposits had considerably lower fluoride concentrations than the underlying bedrock. The high fluoride concentrations in the fresh fracture groundwater (up to 7.4 mg/L) in the TIB-rocks are proposed to be the result of long residence times and the alteration/dissolution of fluorine-bearing primary and secondary minerals along the fracture walls. In terms of risk aspects, this thesis shows that fluoride can add to the transport and inorganic complexation of aluminium in humic-rich, acidic streams. Additionally, 24 % of the children in households with private wells in Kalmar County were assessed to be at risk of excess fluoride intake based on the WHO drinking water guideline value (1.5 mg/L). However, the risk increased significantly when instead the US EPA reference dose (0.06 mg/kg-day) was used, both when all relevant exposure pathways were taken into account as well as water consumption alone. Hence, it is shown that the risk of an excess intake of fluoride is strongly dependent on the basis for evaluation.

FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / A demanda das populaÃÃes por mais Ãgua tem forÃado o desenvolvimento de tÃcnicas para melhorar o aproveitamento de todas as formas de recursos hÃdricos. Em algumas partes dos Estados Unidos da AmÃrica, o fraturamento hidrÃulico tem sido utilizado para estimular poÃos perfurados no embasamento cristalino a aumentarem suas vazÃes. Na regiÃo Nordeste do Brasil, os poÃos perfurados neste tipo de formaÃÃo geolÃgica frequentemente exibem baixas vazÃes, o que os leva à posterior desativaÃÃo ou ao simples abandono. O objetivo principal desta pesquisa à estudar, analisar e quantificar os efeitos que o fraturamento hidrÃulico imprime sobre a transmissividade, a conectividade e as vazÃes de um aqÃÃfero fissural. Para tanto se desenvolveu um modelo de propagaÃÃo de fraturas em formaÃÃes rasas e de matriz impermeÃvel. AlÃm disso, fez-se uso de modelos de hidrÃulica de poÃos para a determinaÃÃo dos parÃmetros hidrodinÃmicos do aqÃÃfero. Para testar a metodologia, dados coletados em dois poÃos de bombeamento perfurados na Fazenda de Horticultura da University of New Hampshire, Durham, NH, foram utilizados. Estes dados incluem testes de bombeamento prÃ-fraturamento e pÃs-fraturamento, ensaio geofÃsicos, alÃm dos registros da operaÃÃo de fraturamento. Uma anÃlise conjunta dos resultados dos testes de bombeamento e do modelo de propagaÃÃo de fratura permitiu concluir que, o fraturamento hidrÃulico aumentou a transmissividade das fraturas em 46 vezes em um poÃo e 285 vezes em outro. A conectividade do sistema de fraturas experimentou acrÃscimos entre 11 e 20 vezes. O dado prÃtico foi que um poÃo passou a fornecer vazÃes 10 vezes maiores e no outro este aumento foi de 18 vezes. Estes melhoramentos foram possÃveis porque o fraturamento hidrÃulico alargou a abertura das fraturas e fez seu raio propagar por dezenas de metros. A distÃncia que a fratura propagou a partir do poÃo juntamente com o aumento na interconexÃo das fraturas conectou o poÃo a regiÃes mais favorÃveis à recarga.