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This paper generalizes the recently proposed approaches for calculating the derivative couplings between adiabatic states in density-functional theory (DFT) based on a Slater transition-state density to transitions such as singlet-singlet excitations, where a single-determinant ansatz is insufficient. The proposed approach is based on restricted open-shell Frank et al. [J. Chem. Phys. 108, 4060 (1998)] theory used to describe a spin-adapted Slater transition state. To treat the dependence of electron-electron interactions on the nuclear positions, variational linear-response density-functional perturbation theory is generalized to reference states with an orbital-dependent Kohn-Sham Hamiltonian and nontrivial occupation patterns. The methods proposed in this paper are not limited to the calculation of derivative coupling vectors, but can also be used for the calculation of other transition matrix elements. Moreover, they can be used to calculate the linear response of open-shell systems to arbitrary external perturbations in DFT. [ABSTRACT FROM AUTHOR]

Hydrothermally active and altered fault/shear zones in crystalline rocks are of practical importance because of their potential similarities with petrothermal reservoirs and exploitable natural hydrothermal systems. The petrophysical and hydraulic characterization of such structures is therefore of significant interest. Here, we report the results of corresponding investigations on a prominent shear zone of this type located in the crystalline Aar massif of the central Swiss Alps. A shallow borehole was drilled, which acutely intersects the core of the shear zone and is entirely situated in its surrounding damage zone. The focus of this study is a detailed characterization of this damage zone based on geophysical borehole measurements. For this purpose, a comprehensive suite of borehole logs, comprising passive and active nuclear, full-waveform sonic, resistivity, self-potential, optical televiewer, and borehole radar data, was collected. The migrated images of the borehole radar reflection data together with the optical televiewer data reveal a complicated network of intersecting fractures in the damage zone. Consequently, the associated petrophysical properties, notably the sonic velocities and porosities, are distinctly different from intact granitic formations. Cluster analyses of the borehole logs in combination with the structural interpretations of the optical televiewer data illustrate that the variations in the petrophysical properties are predominantly governed by the intense brittle deformation. The imaged fracture network and the high-porosity zones associated with brittle deformation represent the main flow pathways. This interpretation is consistent with the available geophysical measurements as well as the analyses of the retrieved core material. Furthermore, the interpretation of the self-potential and fluid resistivity log data suggests a compartmentalized hydraulic behavior, as evidenced by inflows of water into the borehole from different sources, which is likely to be governed by the steeply dipping structures. [ABSTRACT FROM AUTHOR]

Structural inheritance of preexisting crustal discontinuities is widely accepted to have played a crucial role during the Cenozoic tectonic evolution of the northern Alpine foreland. It is recognised as a process that can strongly influence local fault kinematics and strain patterns. The case study presented herein is dedicated to the tectonic analysis of the Freiburg-Bonndorf-Bodensee Fault Zone (FBBFZ) located at the external margin of the northern Alpine Molasse Basin and extending into the crystalline Black Forest Massif. The structure and kinematics of this crustal-scale fault zone are investigated by means of a regional analysis of locally mapped faults, kinematic analysis of outcrop-scale fractures and slip vector modelling. The exceptional possibility of analysing the fault zone exposed from basement to cover allowed for an evaluation of interaction between precursory structures and subsequent deformation features. The results of this study show that the crystalline basement structures exposed along the FBBFZ had a strong imprint on the map-scale fault pattern observable in the Mesozoic and Tertiary sequences. Kinematic analysis of outcrop-scale fracture systems in the latter units yields evidence for local multi-directional extension and strike-slip faulting during Miocene to recent times. While these observations may evoke the interpretation of a multistage palaeostress history along the FBBFZ, slip vector modelling of a very well exposed FBBFZ segment suggests that the various strain records can alternatively be explained by one single regional stress tensor and be related to superordinate deep-seated strike-slip deformation. [ABSTRACT FROM AUTHOR]

Spatial control for in situ dating of mineral phases in fine-grained rocks is a significant challenge in geochronology, and the precision of microsampling is a crucial factor in obtaining accurate results. In this study, a new microsampling approach to Rb-Sr geochronology has been applied to greenschist facies mylonitic shear zones in the Mont Blanc-Aiguille Rouges region of the western European Alps. Using a laser-ablation system for microsampling by laser cutting followed by conventional TIMS Rb-Sr isotopic analysis of μg-sized samples provides an improved workflow for texturally controlled, quasi in situ dating of mineral phases. The automated cutting process minimizes material loss and the risk of handling errors, while facilitating sampling of complex shapes of almost any size, a significant improvement over earlier microscope-mounted microdrills. The new Rb-Sr white mica-calcite ages of between 27 and 30 Ma indicate Oligocene deformation in Alpine shear zones from two specific areas in the Mont Blanc-Aiguilles Rouges region. [ABSTRACT FROM AUTHOR]