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Structural evolution, magnetic fabric and mechanism of exhumation of the Podolsko complex
Burjak, Miroslav ; Žák, Jiří (advisor) ; Franěk, Jan (referee)
This thesis concentrates on a detailed field and structural analysis of the Podolsko complex, Moldanubian unit, Bohemian Massif, complemented by a microstructural study and analysis of magnetic susceptibility (AMS). The Podolsko complex occupies the footwall of a major Variscan normal shear zone and is juxtaposed against the southern to southeastern margin of the Central Bohemian Plutonic complex. During the field work, more than 160 outcrops were examined, the AMS samples were taken at 25 stations, and samples for microstructural studies were taken from 12 localities. On the micro-scale, leucocratic migmatites contain abundant garnet grains which may represent relics of an earlier (ultra-)high preassure metamorphic phase. Retrogression is obvious in other samples of biotite migmatites of the Moldanubian Variegated unit. The retrogression is marked by the presence of sillimanite and chlorite. The main tectonometamorphic event in the Podolsko complex is extensive migmatization coeval with formation of pervasive flat-laying fabric. This is corroborated by the AMS study which indicates concordant steep to flat-laying magnetic and mesoscopic foliations striking NNW-SSE. The AMS also shows that the subhorizontal N-S to NNW-SSE trending magnetic lineations in the Podolsko complex correspond to those in the...
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Magnetic fabric, magma flow and tectonic deformation in volcano-plutonic systems
Tomek, Filip ; Žák, Jiří (advisor) ; Lexa, Jaroslav (referee) ; Petronis, Michael (referee)
Magnetic fabric, magma flow and tectonic deformation in volcano-plutonic systems ABSTRACT This Ph.D. thesis aims to investigate dynamics of emplacement and tectonic history of selected volcano-plutonic complexes in a continental magmatic arc and back arc setting. The thesis presents new data sets from five field areas, presented in separate chapters, which could be viewed as representing a vertical sections through upper part of an intermediate to felsic magmatic system. From top to bottom in this ‛imaginary' vertical system, the examined units are: (1) andesitic lava domes and (2) sub-volcanic magma chambers (<3 km deep) of the Miocene Štiavnica volcano- plutonic complex, Western Carpathians (Slovakia), (3) Shellenbarger pluton (<3 km depth) within the mid-Cretaceous Minarets caldera, Sierra Nevada batholith in California (USA), and ~7-10 km deep granitoids of (4) Lower-Cretaceous Wallowa batholith, Blue Mountains province in Oregon (USA) and (5) Late Devonian Staré Sedlo complex, central Bohemian Massif (Czech Republic). The research incorporates extensive field and structural data, supported by analysis of igneous textures and anisotropy of magnetic susceptibility (AMS). The latter is further accompanied by detailed examination of magnetic mineralogy using thermomagnetic measurements and optical and back...
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Magnetic fabric, magma flow and tectonic deformation in volcano-plutonic systems
Tomek, Filip ; Žák, Jiří (advisor) ; Lexa, Jaroslav (referee) ; Petronis, Michael (referee)
Magnetic fabric, magma flow and tectonic deformation in volcano-plutonic systems ABSTRACT This Ph.D. thesis aims to investigate dynamics of emplacement and tectonic history of selected volcano-plutonic complexes in a continental magmatic arc and back arc setting. The thesis presents new data sets from five field areas, presented in separate chapters, which could be viewed as representing a vertical sections through upper part of an intermediate to felsic magmatic system. From top to bottom in this ‛imaginary' vertical system, the examined units are: (1) andesitic lava domes and (2) sub-volcanic magma chambers (<3 km deep) of the Miocene Štiavnica volcano- plutonic complex, Western Carpathians (Slovakia), (3) Shellenbarger pluton (<3 km depth) within the mid-Cretaceous Minarets caldera, Sierra Nevada batholith in California (USA), and ~7-10 km deep granitoids of (4) Lower-Cretaceous Wallowa batholith, Blue Mountains province in Oregon (USA) and (5) Late Devonian Staré Sedlo complex, central Bohemian Massif (Czech Republic). The research incorporates extensive field and structural data, supported by analysis of igneous textures and anisotropy of magnetic susceptibility (AMS). The latter is further accompanied by detailed examination of magnetic mineralogy using thermomagnetic measurements and optical and back...
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Structural evolution, magnetic fabric and mechanism of exhumation of the Podolsko complex
Burjak, Miroslav ; Žák, Jiří (advisor) ; Franěk, Jan (referee)
This thesis concentrates on a detailed field and structural analysis of the Podolsko complex, Moldanubian unit, Bohemian Massif, complemented by a microstructural study and analysis of magnetic susceptibility (AMS). The Podolsko complex occupies the footwall of a major Variscan normal shear zone and is juxtaposed against the southern to southeastern margin of the Central Bohemian Plutonic complex. During the field work, more than 160 outcrops were examined, the AMS samples were taken at 25 stations, and samples for microstructural studies were taken from 12 localities. On the micro-scale, leucocratic migmatites contain abundant garnet grains which may represent relics of an earlier (ultra-)high preassure metamorphic phase. Retrogression is obvious in other samples of biotite migmatites of the Moldanubian Variegated unit. The retrogression is marked by the presence of sillimanite and chlorite. The main tectonometamorphic event in the Podolsko complex is extensive migmatization coeval with formation of pervasive flat-laying fabric. This is corroborated by the AMS study which indicates concordant steep to flat-laying magnetic and mesoscopic foliations striking NNW-SSE. The AMS also shows that the subhorizontal N-S to NNW-SSE trending magnetic lineations in the Podolsko complex correspond to those in the...
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Emplacement and magnetic fabrics in dikes of syenite porphyries (Western Moldanubian Zone)
Orságová, Lucie ; Verner, Kryštof (advisor) ; Žák, Jiří (referee)
ENGLISH ABSTRACT We present new results of structural and magnetic (AMS) analyses of selected dikes of melasyenite, quartz melasyenite to melagranite porphyries accompanied by lamprophyres (minettes). The studied dike from the locality Nihošovice were dated by U-Pb method on zircons at 338 Ma. The asymmetric structural pattern of the studied dikes gives an excellent evidence for their emplacement and orientation of magmatic flow. The studied dikes were emplaced into: (i) Prevailing parts of the Central Bohemian Plutonic Complex (locality Malčice) and (ii) host high-grade metamorphic rocks of western part of the Moldanubian Zone (locality Nihošovice). Despite of the extensive area of occurrence, compositional variations and age of emplacement of these dikes are relatively narrow. Their geochemical and petrological compositions broadly correspond to ultrapotassic plutonic rocks (durbachites). The dikes are steeply dipping in trend ~NNW-SSE to ~W-E, with range in width between ~20 and ~25 meters. In general, our results show: (i) A relatively low degree of magnetic anisotropy (P= 1.012 - 1.152); (ii) Mostly oblate (planar) fabric, especially in marginal parts of the intrusive bodies (T= -0.091 - 0.941); (iii) Evidence for subhorizontal magmatic flow trajectory defined for a newtonian magma with typical...
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