Aspects of rock deformation rates : numerical modeling and field examples from the Gleinalm, Austria and the Redbank Thrust, Central Australia / Christian Biermeier

• VerfasserIn: Biermeier, Christian
• Place / Publishing House: 2002
• Year of Publication: 2002
• Language: English
• Physical Description: 106 S.; Ill., graph. Darst., Kt.; Zsfassung

eng: Rocks deform as a consequence of applied stresses. The response of a rock to these stresses generally involves a change of position and shape, defined as displacement and strain. This thesis is concerned with aspects of the determination of rates of deformation from microstructures and of rates of displacement on a regional scale. The investigations are based on the study of rocks from a high grade metamorphic and high strained region, the Gleinalm Complex in the Eastern Alps and the Redbank Thrust Zone in Central Australia, and can be summarized as following: 1.) Strain rates of a garnetiferous mica schist of the Gleinalm have been investigated using the approach of finite element and thermobarometric modelling. Therefore, a) the relationship between rotation rate and shear strain rate in general and b) the growth rates for these garnets have been modelled. From the angular geometry of a spiral inclusion trail in a single garnet it is possible to define strain rates, which are consistent with independent estimates for strain rates during the evolution of this part of the Alpine orogen. 2.) The history of displacement across the Redbank Thrust in Central Australia is constrained by thermobarometric and field data and is supported by 40Ar/39Ar hornblende, biotite ages and K-feldspars as well as Th-U-Pb monazite ages. Results indicate that peak PT-conditions around 850°C and 10 kbar in the hanging wall of the thrust were reached around 1780 Ma and that major cooling below 500°C of the entire region occurred around 1140 Ma. Initial 40Ar/39Ar ages of biotites within and north of the thrust zone define the initiation of (re)activation along the Redbank Thrust around 420 Ma. These data are interpreted to indicate exhumation of the thrust system from 20 km to the surface between 420 and 320 Ma.