This Master thesis is written in connection with the Stockholm Bypass project which is Trafikverkets and Sweden’s largest infrastructure project to date. It will consist of 21 km of motorway running west of Stockholm city linking the southern and the northern parts. Out of the total 21 km of motorway, 17 km will run through rock tunnels and cross beneath the Lake Mälaren at 3 places. One of these places is the water passage Fiskarfjärden, situated between Sätra and the island of Kunghatt which has been carefully studied with geological (drill core mapping, BIPS, Water-loss measurements and outcrop mapping) and geophysical (reflection and refraction seismic) methods. This has been used to produce an engineering geological prognosis over the area which indicates that the rock mass in the water passage is heavily fractured and of poor quality. Due to this, additional investigations of the structural framework and the large-scaled structures in the area have been undertaken. The objectives of this thesis are therefore to analyze and classify available geological data, identify and model the major fracture zones situated in the water passage, investigate the kinematics of the fractures focusing on the relative movement between the blocks, if possible, determine the stress orientation and, predict how these major fracture zones will affect the Stockholm Bypass rock tunnel. The available data provided a good opportunity to examine the area. The drill core mappings showed that the dominating fracture orientation in the water passage is WSW-ENE with deformation structures supporting faulting along these fractures. The additional outcrop mapping and drill core mapping which focused on finding kinematic indicators revealed that fractures in the area have been reactivated both as strike-slip and dip-slip faulting and that dextral strike-slip faulting is dominating in a WSW-ENE orientation and sinistral strike-slip faulting in a NW-SE orientation.The orientation of these two fault surfaces matches the main faults on the geological map and indicates that the area is composed of a conjugate fracture set with conjugate shearing whereas the combination of the dominating fracture orientations in the drill cores with the kinematic observations and fractures found in the field correlates with Riedel shear fractures in a dextral shearing configuration. The majority of the zones of crushed rock that cut the tunnel show a dominating WSW-ENE orientation. At this angle to the NW-SE oriented horizontal stress field, these fractures are more likely to experience closure since they are oriented approximately normal to the stress field. The zones of crushed rock that are either oriented E-W or NNE-SSW are more likely to reactivate as strike-slip faults. The very few fracture zones that are oriented NW-SE and correlate to fractures with sinistral shearing are likely to reactivate as dip-slip faults as they are oriented parallel to the present day extensional forces or as strike-slip faults if they are located at depth. / Denna Masteruppsats är skriven i samband med Förbifart Stockholm vilket är Trafikverkets och Sveriges största infrastruktur projekt. Projektet innefattar 21 km motorväg som går väst om Stockholm stad och länkar de södra och norra delarna av staden. 17 km av de totalt 21 km av motorväg kommer gå genom bergtunnlar och korsar under Mälaren vid 3 platser. Ett av dessa ställen är vattenpassagen Fiskarfjärden, belägen mellan Sätra och Kungshatt vilket har undersökts både med geologiska och geofysiska metoder. Underlaget från dessa metoder har sedan används för att ta fram en ingenjörs-geologisk prognos vilket syftar till att beskriva bergmassan i området, både var gäller strukturer och kvalitét. Baserat på denna prognos förväntas bergmassan främst i vattenpassagen vara kraftigt upp-sprucken och av generellt väldigt dålig kvalitét vilket är varför ytterligare undersökningar med fokus på det strukturgeologiska förhållandet och de storskaliga strukturerna i området har genomförts i detta arbete. Målen med detta arbete är därför att analysera och klassificera de tillgängliga geologiska data från tidigare undersökningar, identifiera och modellera the stora sprickzonerna som befinner sig under vattenpassagen, utföra kinematisk analys på sprickorna och fokusera på den relativa rörelsen mellan blocken, om möjligt fastställa orienteringen av bergspänningsfältet och utvärdera hur de stora sprick-zonerna kommer påverka Förbifart Stockholm tunneln. Från borrkärnekarteringen kunde det fastställas att den dominerande sprickorienteringen i vattenpassagen är VSV-ONO och att dessa utgörs av förkast-ningar. Från de kompletterande fältundersökningarna med focus på kinematiska indikatorer kunde det konstateras att sprickorna i området har reaktiverats både som strike-slip- och dip-slip-förkastningar där dextral skjuvning är dominerande i VSV-ONO orienterade sprickor och sinistral skjuvning, vilket är dominerande, i NV-SO orienterade sprickor. Orienteringen av dessa två förkastningsytor sammanfaller med huvudförkastningarna vilka visas på den geologiska kartan och indikerar att området består av konjugerande spricksystem där skjuvning skett. Dock sammanfaller de dominerande sprick-orienteringarna i borrkärnorna tillsammans med storskaliga sprickor från hällkarteringarna också med Riedel sprickor i en konfiguration med dextral skjuvning. Majoriteten av zonerna med krossat berg som korsar tunneln har en dominerande VSV-ONO-lig riktning. Med denna orientering i relation till den NV-SO-liga riktningen på det horisontala maximala bergspänningsfältet, är det inte troligt att dessa sprickor kommer reaktiveras. Zonerna som är orienterade E-W eller NNO-SSV är mer benägna att reaktiveras som strike-slip-förkastningar. De få zoner som är orienterade NV-SO och sammanfaller med sprickor med sinistral skjuvning kommer troligtvis reaktiveras som dip-slip-förkastningar eller som strike-slip-förkastningar om de är belägna på större djup.

Two-thirds of submarine volcanism in the Earth's ocean basins is manifested along mid-ocean ridges and the remaining one-third is revealed along intraoceanic arcs and seamounts. Hydrothermal systems and the circulation patterns associated with these volcanic settings remove heat from the solid Earth into the deep ocean. Hydrothermal circulation continues to remove and redistribute heat in the crust as it ages. The heat and mass fluxes added to the deep ocean influence mixing in the abyssal ocean thereby affecting global thermohaline circulation. In addition to removing heat, hydrothermal processes extract chemical components from the oceanic and carry it to the surface of the ocean floor, while also removing certain elements from seawater. The resulting geochemical cycling has ramifications on the localized mineral deposits and also the biota that utilize these chemical fluxes as nutrients. In this dissertation, I analyze observed conductive heat flow measurements in the Panama Basin and borehole thermal measurements in Brothers Volcano and use mathematical models to estimate advective heat and mass fluxes, and crustal permeability. In the first manuscript, I use a well-mixed aquifer model to explain the heat transport in a sediment pond in the inactive part of the Ecuador Fracture Zone. This model yields mass fluxes and permeabilities similar to estimates at young upper oceanic crust suggesting vigorous convection beneath the sediment layer. In the second manuscript, I analyze the conductive heat flow measurements made in oceanic between 1.5 and 5.7 Ma on the southern flank of the Costa Rica Rift. These data show a mean conductive heat deficit of 70%, and this deficit is explained by various hydrothermal advective transport mechanisms, including outcrop to outcrop circulation, transport through faults, and redistribution of heat by flow of hydrothermal fluids in the basement. In the third manuscript, I analyze the borehole temperature logs for two sites representative of recharge and discharge areas of hydrothermal systems in the Brothers Volcano. I develop upflow and downflow models for fluids in the borehole and formation resulting in estimated of flow rates and permeabilities. All three independent research works are connected by the common thread of utilizing relatively simple mathematical concepts to get new insights into hydrothermal processes in oceanic crust. / PHD / Two-thirds of underwater volcanic activity in the Earth’s ocean basins is exhibited in areas where new material for Earth’s outer shell is created and the remaining one-third is displayed along areas where the outer shell is destroyed. In these areas, hot springs that are under water and their water movement patterns remove heat from the solid outer shell and puts it into the deepest parts of the ocean. Hot water circulation continues to remove and redistribute heat and various chemical elements in the shell as it grows old. This heat and chemical elements, which get added to the deep ocean water, influences the way water mixes and forms layers in the world oceans. This also affects the movement of ocean currents. The chemical elements removed from the shell by hot water gets deposited as minerals on the ocean floor in places where hot springs arise. This variety of minerals provides nutrients for different marine organisms. In this work done during my PhD studies, I examine the heat and temperature that was measured in the Panama Basin and Brothers Volcano. I utilize these examinations to build simple math models to find out how much heat and chemical components are being added to the deep ocean water. I also find out the methods in which the hot water springs appear on the ocean floor and the patterns in which the hot water circulates in the Earth’s outer shell. All of these estimates will help the scientists who are studying the patterns and changes in ocean currents by giving them a number on how much heat is released from the inside of the Earth.