Faulting processes in active faults - Microstructural, mineralogical and geochemical characterization of drill core samples from international drilling projects

• Applicant: Dr. Christoph Janssen
• Subject Area: Palaeontology ; Mineralogy, Petrology and Geochemistry
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 270673698

• Final Report Year: 2019

Final Report Abstract

Our research project was structured around a series of questions addressing some basic issues in fault dynamics. The focus of our study was the analysis of the mechanical behavior of the Alpine Fault. Beyond this primary goal, we deployed our integrated field and analytical approach to investigate slip zone samples from landslides. In response to these issues several deformation mechanisms, operating in the fault and landslide slip zones, were successfully analyzed using TEM, SEM, XRD/XRF and microprobe analyses. These combined microstructural, mineralogical and geochemical analyses, considered in context of other studies, show that the Alpine Fault zone architecture is more appropriately described by the broad and complex conceptual model of Faulkner et al. (2003) rather than the simple, single PSZ model of Caine et al. (1996). This suggests that investigated fault gouges are not part of the same fault plane but represent distinct slip planes within a complex network of anastomosing shear planes forming the core of the Alpine Fault, surrounded by a broader damage zone. The cyclic evolution of the fault’s strength is controlled by the extremely high geothermal gradient and associated presence of high-temperature fluids. Slip zones of landslides share many characteristic features with those of faults such as mineralogical composition and deformational behavior, manifested by the predominance of deformation processes involving fragmentation and/or rotation of particles. The observed microstructures in thin sections of slip zone material are very similar to microstructures in gouge samples from major faults.

Publications

• IODP / ICDP Kolloquium, Heidelberg, 14.03. – 16.03.2016: Strain localization at a Plate Boundary: investigation of the Principal Slip Zone of the Alpine Fault, NZ, in borehole and outcrop samples
  Schuck, B., Janssen, C., Toy, V.G., Dresen, G.
  
• Fall meeting, American Geophysical Union (AGU), New Orleans: 11.12. – 15.12.2017: Microstructures indicate large influence of temperature and fluid pressure on the reactivation of the Alpine Fault, New Zealand
  Schuck, B., Janssen, C., Schleicher, A.M., Toy, V.G., Dresen, G.
  
• IODP / ICDP Kolloquium, Braunschweig, 14.03. – 16.03.2017: Fault core deformation mechanisms deduced from microstructures, mineralogy and geochemistry of the Alpine Fault, New Zealand
  Schuck, B., Janssen, C., Schleicher, A.M., Toy, V.G., Dresen, G.
  
• (2018): Microstructures imply cataclasis and authigenic mineral formation control geomechanical properties of New Zealand’s Alpine Fault. Journal of Structural Geology 110, 172 – 186
  Schuck, B., Janssen, C., Schleicher, A.M., Toy, V.G. and Dresen, G.
  
• (2018): Microstructures in landslides in northwest China – Implications for creeping displacements? Journal of Structural Geology 106, 70-85
  Schäbitz, M., Janssen, C.,Wenk, H.R., Wirth, R., Schuck, B., Wetzel, H.U., Dresen G.
  
• IODP / ICDP Kolloquium, Bochum, 14.03. – 16.03.2018: Influence of mineraloy and microstructures on strain localization and fault zone architecture of the Alpine Fault, New Zealand
  Schuck, B., Janssen, C., Schleicher, A.M., Toy, V.G., Dresen, G.
  
• Fault zone architecture of a large plate-bounding strike-slip fault: a case study from the Alpine Fault, New Zealand. Solid Earth Discussions
  Schuck, B., Schleicher, A.M., Janssen, C., Toy, V.G. and Dresen, G.