Symposium über Fragen der Cyanophytentaxonomie in Kastanienbaum, 3.–16. August 1972

Ohne Zusammenfassung Internationale Arbeitsgemeinschaft für Cyanophytenforschung IAC     

Kulturversuche mitGloeotrichia echinulata (J. E. Smith) P. Richter

Ohne Zusammenfassung Publikation NRC Nr. 7225.     

Structural-permeability favorability in crystalline rocks and implications for groundwater flow paths: a case study from the Aar Massif (central Switzerland)

Groundwater flow in granitic bedrock is of major interest for underground projects such as radioactive waste disposal. It is generally accepted that granitic rocks of the upper crust are characterized as faulted low-porosity rocks showing fault-related permeability. In this study, the influence of existing faults on the present-day water flow in the Grimsel Test Site (Switzerland), an underground rock laboratory situated in granitoid rocks, was investigated by mapping water discharges. As a result, the link between water flow and faults considering slip-tendency analysis and fault intersections is evaluated. Water-conducting features were combined in a structural-permeability favorability map. Faults and dykes occur as three orientation groups, NE–SW, E–W, and NW–SE trending, all steeply dipping southwards with fault intersections also steeply plunging southwards. In total, 100 water discharges were mapped in summer 2014 and 85 in winter 2016, which are located along faults or fault intersections. A comparison of water discharges with structures showed that high-slip-tendency metabasic dykes and fault or dyke intersections represent the dominant flow paths. Further, it could be demonstrated that higher slip-tendency tends to lead to enhanced average hydraulic conductivity and therefore more constant water flow. Based on water fluxes, fault intersections are inferred to represent first-order locations of water percolation followed by high-slip-tendency metabasic dykes. The combination of all water-conducting features into a structural-permeability map results in covering all water discharges. Therefore, the structural-permeability favorability map can serve as suitable representation for constraining water inflow in fractured granitoid host rocks.     

Über die Möglichkeit,die Temperaturverteilung in Sonnenflecken durch einen anisotropen Wärmetransport zu erklären

Numerical solutions of a heat conduction problem in an anisotropic medium are used for a discussion of the possibility to explain the temperature distribution in sunspots and their environment. The anisotropy is assumed being due to the strong magnetic field in sunspots and the region below. This magnetic field forces the convection to take an anisotropic structure (two-dimensional turbulence) and thus the region gets anisotropic conduction properties, on the average. The discussion shows that the observed temperature profiles can be explained in case the depth of the region of anisotropy is about as large as the diameter of the spot or larger.     

The effect of deformation on the TitaniQ geothermobarometer: an experimental study

We performed high strain (up to 47 %) axial compression experiments on natural quartz single crystals with added rutile powder (TiO₂) and ~0.2 wt% H₂O to investigate the effects of deformation on the titanium-in-quartz (TitaniQ) geothermobarometer. One of the objectives was to study the relationships between different deformation mechanisms and incorporation of Ti into recrystallized quartz grains. Experiments were performed in a Griggs-type solid-medium deformation apparatus at confining pressures of 1.0–1.5 GPa and temperatures of 800–1,000 °C, at constant strain rates of 1 × 10^?6 or 1 × 10^?7 s^?1. Mobility of Ti in the fluid phase and saturation of rutile at grain boundaries during the deformation experiments are indicated by precipitation of secondary rutile in cracks and along the grain boundaries of newly recrystallized quartz grains. Microstructural analysis by light and scanning electron microscopy (the latter including electron backscatter diffraction mapping of grain misorientations) shows that the strongly deformed quartz single crystals contain a wide variety of deformation microstructures and shows evidence for subgrain rotation (SGR) and grain boundary migration recrystallization (GBMR). In addition, substantial grain growth occurred in annealing experiments after deformation. The GBMR and grain growth are evidence of moving grain boundaries, a microstructure favored by high temperatures. Electron microprobe analysis shows no significant increase in Ti content in recrystallized quartz grains formed by SGR or by GBMR, nor in grains grown by annealing. This result indicates that neither SGR nor moving grain boundaries during GBMR and grain growth are adequate processes to facilitate re-equilibration of the Ti content in experimentally deformed quartz crystals at the investigated conditions. More generally, our results suggest that exchange of Ti in quartz at low H₂O contents (which may be realistic for natural deformation conditions) is still not fully understood. Thus, the application of the TitaniQ geothermobarometer to deformed metamorphic rocks at low fluid contents may not be as straightforward as previously thought and requires further research.     

Development of Iron Speciation Reference Materials for Palaeoredox Analysis

The development and application of geochemical techniques to identify redox conditions in modern and ancient aquatic environments has intensified over recent years. Iron (Fe) speciation has emerged as one of the most widely used procedures to distinguish different redox regimes in both the water column and sediments, and is the main technique used to identify oxic, ferruginous (anoxic, Fe(II) containing) and euxinic (anoxic, sulfidic) water column conditions. However, an international sediment reference material has never been developed. This has led to concern over the consistency of results published by the many laboratories that now utilise the technique. Here, we report an interlaboratory comparison of four Fe speciation reference materials for palaeoredox analysis, which span a range of compositions and reflect deposition under different redox conditions. We provide an update of extraction techniques used in Fe speciation and assess the effects of both test portion mass, and the use of different analytical procedures, on the quantification of different Fe fractions in sedimentary rocks. While atomic absorption spectroscopy and inductively coupled plasma‐optical emission spectrometry produced comparable Fe measurements for all extraction stages, the use of ferrozine consistently underestimated Fe in the extraction step targeting mixed ferrous–ferric minerals such as magnetite. We therefore suggest that the use of ferrozine is discontinued for this Fe pool. Finally, we report the combined data of four independent Fe speciation laboratories to characterise the Fe speciation composition of the reference materials. These reference materials are available to the community to provide an essential validation of in‐house Fe speciation measurements.