Microstructural characterisation of ultracataclastic zones in quartzites by electron microscopy

超细晶石英与地震构造化石（pseudoachylytes）的时空关联在自然界中频繁出现，似乎是地震过程的一个重要特征。对DFG项目WA 1010/11-1一期的Schneeberger Zug（南蒂罗尔，意大利）含伪石英岩的这种关系进行了详细的微观结构表征。在同震前或同震中，寄主岩石的晶体塑性变形产生了超细晶（<2 μm）石英微剪切带。由于两个变量（应变速率和温度）主要控制微观组织的发展，因此微观组织本身不能用来约束环境条件。因此，至少确定同震事件期间的变形温度是至关重要的。为此，我们打算应用钛-石英（TitaniQ）地温计。最近测试了这种方法，以限制石英糜棱岩在300-500°C温度范围内的变形温度。为了估计摩擦融化的深度，进一步的信息可以通过对Schneeberg假achylyte的Ar-Ar测年来限制挖掘历史。初步分析表明，经充分分析的意大利南阿尔卑斯Adamello含伪长石英岩的石英变形显微结构与Schneeberger含伪长石英岩的石英变形显微结构非常相似。因此，计划将该地区现有样品作为对比研究，进行微结构控制的TitaniQ分析。

The temporal and spatial association of (ultra)fine-grained quartz with pseudotachylytes (fossil earthquake structures) frequently appear in nature and seems to be an important feature characteristic for seismic processes. A detailed microstructural characterisation of this relationship was worked out for pseudotachylyte-bearing quartzite of the Schneeberger Zug (Southern Tirol, Italy) during the first period of DFG project WA 1010/11-1. Crystal plastic deformation in host rock has produced ultrafine-grained (<2 μm) quartz microshear zones prior or during the co-seismic event. Since two variables (strain rate and temperature) mainly control the microstructural development the microstructures by its own can not be used to constrain the ambient conditions. Thus it is crucial to determine at least the deformation temperature during the co-seismic event. For this purpose we intend to apply the Ti-in-quartz (TitaniQ) geothermometer. This method was recently tested to constrain deformation temperatures of quartz mylonites in the temperature range of 300-500°C. Further information can be constrained by Ar-Ar dating of the Schneeberg pseudotachylyte with respect to the exhumation history in order to estimate the depth of frictional melting. Preliminary analysis reveals that the deformation microstructures of quartz in the well-analysed pseudotachylyte-bearing Adamello tonalite (Italian Southern Alps) are very similar to those of the Schneeberger pseudotachylyte-bearing quartzite. Thus existing samples of this area are planned to use as a comparison study for microstructural controlled TitaniQ analyses.