Microstructural characterisation of ultracataclastic zones in quartzites by electron microscopy

(超)细颗粒石英与假玄武岩(古地震构造)的时空组合在自然界中频繁出现，似乎是地震过程的一个重要特征。在DFG项目WA1010/11-1的第一阶段，对意大利南蒂罗尔Schneberger Zug含假玄武岩的石英岩进行了详细的微结构特征描述。在同震前或同震期间，围岩中的晶体塑性变形产生了超细颗粒(&lt；2μm)石英微剪切带。由于两个变量(应变速率和温度)主要控制组织的发展，组织本身不能用来约束环境条件。因此，至少确定同震期间的形变温度是至关重要的。为此，我们打算应用钛in-石英(TianiQ)地质温度计。最近，该方法被测试将石英糜棱岩的变形温度限制在300-500°C的温度范围内。进一步的信息可以通过Schneberg拟玄武岩的Ar-Ar测年来限制，以便估计摩擦熔融的深度。初步分析表明，含假玄武岩的埃达梅洛英云闪长岩(意大利南阿尔卑斯山)中石英的变形显微结构与含Schneberger拟玄武岩的石英岩非常相似。因此，这一地区的现有样品计划用作微结构控制的钛iQ分析的对比研究。

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.