Microstructures imply cataclasis and authigenic mineral formation control geomechanical properties of New Zealand's Alpine Fault

Fault zone architecture of a large plate-bounding strike-slip fault: a case study from the Alpine Fault, New Zealand

“…The fault zone architecture of New Zealand's Alpine Fault, a large, transpressional plate-bounding fault and a significant geohazard, has attracted increasing attention in the last ten years (e.g. Barth et al, 2012;Sutherland et al, 2012;Barth et al, 2013;Toy et al, 2015;Williams et al, 2016;Townend et al, 2017;Lukács et al, 2018;Schuck et al, 2018;Williams et al, 2018). Here, by combining results of these previous studies on the Alpine Fault's structure with new field observations, microstructural, mineralogical and geochemical analyses we show that the Alpine Fault has a complex fault geometry at and above seismogenic depths.…”

“…By considering the different fault kinematics (low-angle detachment vs. thrust fault), the Alpine Fault with its layered gouges described in this and previous work (e.g. Boulton et al, 2012;Schuck et al, 2018) is structurally identical to the faults analyzed in the Death Valley ( Fig. 10; for details see Biegel and Sammis, 2004).…”

“…There, mutually cross-cutting calcite veins (~15 µm thick) display small (< 20 µm) dextral offsets. Furthermore, there are < 100 µm large calcite-cemented breccias composed of angular fragments of clastic particles and matrix clasts (see figure 3c in Schuck et al, 2018). At DFDP-1A, calcite is encountered in lenses and veins, which frequently cross-cut clasts but rarely the matrix and generally increase in abundance towards the PSZ.…”

“…At Waikukupa Thrust, veins display mutual cross-cutting relationships with dextral offsets. For a detailed description of these calcite veins, the reader is referred to the preceding work of Schuck et al (2018). At Gaunt Creek, the 350-800 µm wide vein network (Figs.…”

“…Schleicher et al, 2015), microstructural (e.g. Toy et al, 2015) and geochemical (Schuck et al, 2018) properties of the PSZ. To the SW of the study area, the fault core might be more complex, because of its different lithological composition and fault orientation (Barth et al, 2013).…”