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Institute of Geophysics of the CAS, v. v. i.
Analogue modelling is an important tool in geology that enables investigation of possible mechanisms that contribute to the generation of finally observed structures (Ramberg, 1981). In the words of Cloos (1955): “Many interpretations would never have been published, if the author had only once tried his suggested mechanism of folding or faulting in an experiment”.
In order to understand the evolution of internal fabrics of viscous materials we have developed a new approach that simulates fabric development using AMS (anisotropy of magnetic susceptibility) (Kratinová et al., 2006). The AMS fabrics in our models are correlated with the complex flow pattern indicated by flow induced structures in coloured plaster. We recently focus on the evaluation of the internal fabrics within models for magmatic plutons and viscous hot prowedge orogens colliding with stiff retrowedge indenters. Another study is focused on the three-dimensional basalt dyke swarm geometries and associated patterns of effusive vents distribution.
Experimental modeling machines in our laboratory:
1) Injection sandbox: This apparatus consists of two box shaped containers with opened frontal sides that are attached to each other with a rubber sheet simulating homogeneous deformation between two crustal blocks. The device performs simple extension/compression or oblique deformation (transtension or transpression) by adjusting the reel system of steel ropes attached to the containers. The ropes are pulled by a computer controlled step motor system. Simultaneous injection of experimental magma (also driven by step motor) in the middle of the deformation zone is provided by a cylinder and piston setup with plumbing that enters the overburden through the central hole in the rubber sheet. The system enables injection during static conditions or during continuous deformation of the overlying material in the sanbox. However, the direction of extension (compression) can not be adjusted during the experiment. The present projects undertaken on this apparatus target: 1) the shape development and internal fabrics in simple and compositionally zoned plutons emplaced during various tectonic settings, 2) shape evolution of basaltic dyke swarms in active rift systems and associated effusive vent patterning on the surface.
2) Seismic Table: fluidization and liquifaction in sedimentary deltas.
3) Orogenic indentation: This apparatus simulates the folding and extrusion of orogenic (pro-wedge) lower crust due to collision with a rigid (retro-wedge) indentor. Since the mobile plate is pulled by a dead-weight during the experiment, the analogue material between the glass walls on the mobile steel plate is pushed against the solid indentor. The base of the steel plate represents the base of the upper mantle which is decoupled from the lower crust and is being subducted below the adjacent continent. The tilt and height of the indentor is adjustable. This indentor represents the stiff mafic lower crust of the retro-continent. Both, the movable steel plate and the indentor are equipped by a heating unit with thermostat to heat the analogue material (wax) in the apparatus. The goal of the presently starting project is to study the topology and internal strain pattern of deformed lower crust during continental collision for various thicknesses of the upper/middle/lower crust, collision velocities and thermal gradients.
4) Hydraulic squeezer: The hydraulic squeezer apparatus allows injection of analogue magma into a sandbox. The apparatus was employed for investigation of internal fabrics in lava domes and intrusions into diatremes. During the experiment, the plaster of Paris suspension is squeezed out from a container at the bottom of the apparatus by a hydraulic squeezer force transmitted over a steel frame and a loading board throught a steel cylindrical conduit. The apparatus allows injection of relatively stiff (crystal rich) magma analogues and injection into variable stratified crustal environments.
* Závada, P., Dedecek, P., Mach, K., Lexa, O. & Potuzak, M. (2011). Emplacement dynamics of phonolite magma into maar-diatreme structures - correlation of field, thermal modeling and ams analogue modeling data, Journal Of Volcanology And Geothermal Research 201(1-4), 210–226. DOI:10.1016/j.jvolgeores.2010.07.012.
* Kratinova Z., Machek M., Kusbach V., (2010). Fabric transpositions in granite plutons - an insight from non-scaled analogue modelling, Journal of the Geological Society of India,75, 267-277, DOI: 10.1007/s12594-010-0014-z.
* Závada, P., Roxerová, Z., Kusbach, V., and Schulmann, K., (2009), vInternal fabric development in complex lava domes. Tectonophysics, 466(1-2), 101-113. DOI:10.1016/j.tecto.2008.07.005.
* Kratinová, Z., Závada, P., Hrouda, F., Schulmann, K., (2006), Non-scaled analogue modelling of AMS development during viscous flow: a simulation on diapir-like structures. Tectonophysics, 418, 1-2, 51-61, DOI: 10.1016/j.tecto.2005.12.013.
* Cloos, E., (1955). Experimental analysis of fracture patterns, Geol. Soc. Am. Bull., 66, 241-256.
* Ramberg, H., (1981). Gravity, deformation and the Earth’s crust. Academic press, New York. 2ed edition. 452 pp.
* Roxerová, Z., Závada, P., Hrouda, F., Schulmann, K., (2006). Non-scaled analogue modelling of AMS development during viscous flow: a simulation on diapir-like structures. Tectonophysics, 418, 1-2, 51-61.