Microstructural characterization of natural fractures and faults in the Opalinus Clay: insights from a deep drilling campaign across central northern Switzerland

Abstract The Middle-Jurassic Opalinus Clay is the foreseen host rock for radioactive waste disposal in central northern Switzerland. An extensive drilling campaign aiming to characterize the argillaceous formation resulted in a comprehensive drill core data set. The rheologically weak Opalinus Clay is only mildly deformed compared to the over- and underlying rock units but shows a variety of natural fractures. While these structures are hydraulically indistinguishable from macroscopically non-deformed Opalinus Clay today, their analysis allows for a better understanding of the deformation behaviour in the geological past. Here, we present an overview of the different fracture and fault types recorded in the Opalinus Clay and a detailed microstructural characterization of veins—natural dilational fractures healed by secondary calcite and celestite mineralizations. Macroscopic drill core analysis revealed five different natural fracture types that encompass tension gashes of various orientations with respect to bedding and small-scale faults with displacements typically not exceeding the drill core diameter. The occurrence of different fault types generally fits well with the local tectonic setting of the different drilling sites and with respect to the neighbouring regional fault zones. The microstructural investigations of the various vein types revealed their often polyphase character. Fibrous bedding-parallel veins of presumable early age were found to be overprinted by secondary slickenfibres. The polyphase nature of fibrous bedding parallel veins and slickenfibres is supported by differing elemental compositions, pointing towards repeated fracturing and mineralization events. Direct dating of vein calcites with U–Pb was unsuccessful. Nevertheless, age constraints can be inferred from structural orientations and fault slip kinematics. Accordingly, some of the veins already formed during sediment compaction in Mesozoic times, others possibly relate to Early Cenozoic foreland uplift. The youngest veins are most likely related to Late Cenozoic regional tectonic events, such as the Jura fold-and-thrust belt to the south and the Hegau-Lake Constance Graben to the northeast of the study area. During these latest tectonic events, previously formed veins acted as rheologically stiff discontinuities in the otherwise comparably weak Opalinus Clay along which deformation of the rock formation was re-localized

Technological knowledge transfer in least developed countries with a view to intercultural awareness

Zsfassung in dt. SpracheIn the last few years ICT projects in developing countries1 have gained tremendously in importance. Nevertheless there has been a lack of case studies dealing with teaching computing in LDCs. So far there has been no case study performed by a scientist with practical experiences in computer related interventions.This case study describes a computer project that was undertaken at a primary school in South-Western Uganda, in the year 2002. During the intervention I encountered - in parallel to technical problems - several misunderstandings related to culture. It became apparent that the participating people from that region approach new technology differently than we do (in the mind of members of different cultural backgrounds, namely teachers from Austria) and therefore integrate knowledge in a different way. This lead to a cultural perspective and a qualitative research was conducted. The collected empirical data enabled a systematic hermeneutical analysis with regard to Witzel's programme of problem centred analysis.This research outlines the social function of computers among the regions' population and discusses the socially reflected interrelationship between involved social actors and the reigning hierarchic positions. It shows that too high expectations (according to computers) are set by participants and that computers are seen as an empowering status symbol. This study shows that the cultural expectation towards gaining control over technology, such as computers, were seen as to be represented in a non explorative way of teaching, wheras the external instructors were causing a cultural break by applying explorative student-centred teaching methods. The strong hierarchic position of teachers and parents hinder the pupils eagerness to explore new technology on their own, as they have to expect different forms of sanctions, when mistakes are made. A solution might be that a computer teacher become a "cultural broker" [Aikenhead, 2002] who is aware of the student's underlying world views, "regionally used teaching methods/habits", "ways of sanctions", use and status of "local language", the social role of "involved institutions", and draws upon knowledge on regional historical and cultural pecularities. This is also related with the readiness to take into account a loss of power which a successful technological knowledge transfer implies.Im Zeitalter der Neuen Technologien liegt im Einsatz von Informations- und Kommunikationstechnologien (IKT) viel Hoffnung zur Reduktion der Armut. Gedanken über die Schwierigkeiten, die beim Einsatz des ("westlichen") Computers in anderen Kulturen auftreten, bleiben unbemerkt oder werden totgeschwiegen. Veröffentlichte Anwenderberichte und Projektstudien sind Mangelware und es gab - bis dato - keine Untersuchung die von einem Computerlehrer mit Praxiserfahrung durchgeführt wurde.Diese Fallstudie untersucht ein Computerprojekt an einer Grundschule in Südwest - Uganda. Während des Projektes im Jahr 2002 nahm ich mehrere kulturell bedingte Missverständnisse wahr, auf die unter der Anwendung von qualitativen Methoden im Jahr 2003 untersucht wurden. Durch den Einsatz einer neuartigen Methodenkombination des "problemzentrierten Interviews" [Witzel, 1985] und der "objektiven Hermeneutik" [Oevermann, 2002] wurde die Integration des Computers in den Alltag im Jahr 2003 beleuchtet. Diese Untersuchung präsentiert die soziale Funktion des Computers innerhalb der regionalen Bevölkerung und diskutiert die sozialen Beziehungen der involvierten Akteure wie Lehrer, Schüler, Computerlehrer, Evaluator und Geldgeber.Dabei werden die (zu) hoch gestellten Erwartungshaltungen (gegenüber Computer) aufgezeigt und der latente und erwartete Zugewinn an Macht präsentiert. Darüber hinaus zeigt diese Studie auch die kulturelle Erwartungshaltung der Technologiekontrolle auf. Diese steht im Kontrast zu der von den externen Computerlehrern durchgeführte und geförderte explorierende Aneignung mit hilfe schülerzentrierter Methoden. Es kann dabei angenommen werden, dass die stark hierarchische Lehrer-Schüler-Beziehung den Drang zur selbstständigen Technologieauseinandersetzung einschränkt, da finanzielle und körperliche Strafen bei Fehlern zu erwarten sind. Diese Studie präsentiert als Lösung das Konzept des "Cultural Brokers" [Aikenhead, 2002]. Ein "Cultural Broker" erkennt unterschiedlicheWeltanschauungen zur Wissensaneignung an, thematisiert diese im Prozess des Technologietransfers, um zu verhindern, dass der Computer kulturimperialisitisch transferiert wird.Der Lehrer nimmt so die Rolle eines "Cultural Brokers" ein, dessen Aufgabe in der Wahrnehmung und Vermittlung kultureller Differenzen liegt. Ziel ist eine relativ "wertungsarme" Kommunikation bzw. der Aufbau eines gemeinsamen "Kommunikationsraums".Er/Sie verhandelt gemeinsam mit den Studenten geeignete Vorgangsweisen aus und ermöglicht so einen erfolgreichen technologischen Wissenstransfer. Aus dieser Fallstudie geht hervor, dass ein "Cultural Broker" idealerweise über lokales kulturelles, historisches Wissen, den Gebrauch der lokalen Sprache, Bewusstsein über die soziale Rollen involvierter sozialer Akteure sowie Sanktionierungsmaßnahmen verfügt.Die Annahme dieses neuen Selbstverständnisses bedingt jedoch die Bereitschaft der Computerlehrer einen Machtverlust in Kauf zu nehmen, welcher jedoch für einen erfolgreichen Technologietransfer unerlässlich zu sein scheint.27

Hydrochemical and isotopic (d2H, d18O, 3H) characterization of fracture water in crystalline rock (Grimsel, Switzerland)

Knowledge on water circulation through crystalline rock is of key interest for radioactive waste disposal, geothermal projects or groundwater supply. This study presents first results of long-term monitoring of fracture groundwater chemical and isotope compositions combined with structural data on fracture networks developed in the crystalline rocks at the Grimsel Test Site (GTS), Switzerland. Groundwater circulation in the two major lithologies, the Central Aar Granite (CaGr) and the Grimsel Granodiorite (GrGr) is mainly associated to NE-SW trending brittle deformation structures. Within the different lithologies groundwater chemical and water isotope (delta18O, delta 2H) compositions remain constant over the 2 years monitoring period. This suggests the absence of seasonal variations at the sampling depth of 420–520 m below surface. Differences in chemical and isotope composition occur, however, between groundwater collected from the CaGr and GrGr and can be related to differences in infiltration area, flow paths, residence time and water-rock interaction in the two rock units. The delta 2H and delta 18O signatures indicate a meteoric origin from the same moisture sources under present-day climatic conditions and the absence of measurable 3H suggests residence times > 65 yrs for groundwater from both units

Constraints on Evolution and Residence Time of Geothermal Water in Granitic Rocks at Grimsel (Switzerland)

Thermal spring water (17–28°C) occurring in crystalline rocks at the Grimsel area, Switzerland, represents a mixture of an old geothermal component with a surface-derived, young cold water component. Comparison of chemical and isotope data of cold and thermal spring water collected in 1991/92 and 2014/15 allows deciphering the residence time and evolution of the geothermal component. Accounting for changes in atmospheric input for δ18O, δ2H, 3H and 14C, a meteoric origin from similar moisture source(s) for the cold and geothermal component is proposed, a 3H-PF model age of about 7 years for the cold component and infiltration of the geothermal component before 30 ka during an interglacial cycle. Deep circulation of the geothermal component is inferred from water temperatures of 110–120 °C and the uptake of geogenic CO2 and/or CH4

Microstructural characterization of natural fractures and faults in the Opalinus Clay: insights from a deep drilling campaign across central northern Switzerland

The Middle-Jurassic Opalinus Clay is the foreseen host rock for radioactive waste disposal in central northern Switzerland. An extensive drilling campaign aiming to characterize the argillaceous formation resulted in a comprehensive drill core data set. The rheologically weak Opalinus Clay is only mildly deformed compared to the over- and underlying rock units but shows a variety of natural fractures. While these structures are hydraulically indistinguishable from macroscopically non-deformed Opalinus Clay today, their analysis allows for a better understanding of the deformation behaviour in the geological past. Here, we present an overview of the different fracture and fault types recorded in the Opalinus Clay and a detailed microstructural characterization of veins—natural dilational fractures healed by secondary calcite and celestite mineralizations. Macroscopic drill core analysis revealed five different natural fracture types that encompass tension gashes of various orientations with respect to bedding and small-scale faults with displacements typically not exceeding the drill core diameter. The occurrence of different fault types generally fits well with the local tectonic setting of the different drilling sites and with respect to the neighbouring regional fault zones. The microstructural investigations of the various vein types revealed their often polyphase character. Fibrous bedding-parallel veins of presumable early age were found to be overprinted by secondary slickenfibres. The polyphase nature of fibrous bedding parallel veins and slickenfibres is supported by differing elemental compositions, pointing towards repeated fracturing and mineralization events. Direct dating of vein calcites with U–Pb was unsuccessful. Nevertheless, age constraints can be inferred from structural orientations and fault slip kinematics. Accordingly, some of the veins already formed during sediment compaction in Mesozoic times, others possibly relate to Early Cenozoic foreland uplift. The youngest veins are most likely related to Late Cenozoic regional tectonic events, such as the Jura fold-and-thrust belt to the south and the Hegau-Lake Constance Graben to the northeast of the study area. During these latest tectonic events, previously formed veins acted as rheologically stiff discontinuities in the otherwise comparably weak Opalinus Clay along which deformation of the rock formation was re-localized.ISSN:1661-8734ISSN:1661-872