Masterclass Microtectonics

Part I: Delivered by Prof. Virginia Toy and Dr. Friedrich Hawemann, which is entitled “Fault Rocks and Fault Mechanisms Revisited” will focus on how fault zone processes can be inferred from their textural record. The class will examine the set of thin sections and samples of fault rocks (mylonites, cataclasites, pseudotachylytes) from the Outer Hebrides Fault Zone (Scotland) that inspired Sibson (1977) to develop his widely-cited classification of fault rocks, and from New Zealand’s Alpine Fault Zone where he next applied this classification. Additionally, a set of exercises will examine microstructural datasets from both Outer Hebrides and Alpine Fault Zone samples acquired using advanced analytical tools, including SEM (EBSD, BSE-imaging), TEM, and synchrotron-CT. These exercises will demonstrate how to quantify the 2D and 3D arrangement and shapes of fault rock grains and particles, their textures, their crystallographic orientations, and the nature of porosity. The implications for fault rheology will be explored.

Part II: Delivered by Prof. Cees Passchier, teaches how deformation mechanisms can be inferred from the microstructures visible in thin sections. It is based on the book “Microtectonics“ by Passchier and Trouw (2005), and the superb Microtectonics Collection of 300 selected thin sections that are the source of figures in that book will be examined during the course. The main topics, which are treated through an alternation of lectures and microscopy practicals, are: Principles of microtectonic analysis, overprinting relations, deformation phases and tectonic phases, flow and deformation, intracrystalline deformation, foliations and lineations, shear zones, veins and fringes, porphyroblasts, metamorphic reaction rims.