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78 J. FRANĚK ET AL.Weber, K., 1984. Variation in tectonic style with time (Variscanand Proterozoic systems, Europe). In: Patterns of Change inEarth Evolution. Report of the Dahlem workshop (eds Holland,H.D. & Trendall, A.F.), pp. 371–386. Springer-Verlag, Berlin.Weber, K. & Behr, H.J., 1983. Geodynamic interpretation of theVariscides. In: Intracontinental Fold Belts (eds Martin, H. &Eder, F.W.), pp. 427–469. Springer-Verlag, Berlin.Wendt, J.I., Kro¨ ner, A., Fiala, J. & Todt, W., 1993. Evidencefrom zircon dating for existence of approximately 2.1 Ga oldcrystalline basement in southern Bohemia, Czech Republic.Geologische Rundschau, 82, 42–50.Wendt, J.I., Kro¨ ner, A., Fiala, J. & Todt, W., 1994. U-Pb zirconand Sm-Nd dating of Moldanubian HP ⁄ HT granulites fromsouth Bohemia, Czech Republic. Journal of the GeologicalSociety, London, 151, 83–90.Zˇák, J., Holub, F.V. & Verner, K., 2005a. Tectonic evolution ofa continental magmatic arc from transpression in the uppercrust to exhumation of mid-crustal orogenic root recorded byepisodically emplaced plutons: the Central Bohemian PlutonicComplex (Bohemian Massif). International Journal of EarthSciences, 94, 385–400.Zˇák, J., Schulmann, K. & Hrouda, F., 2005b. Multiple magmaticfabrics in the Sa´zava pluton (Bohemian Massif, CzechRepublic): a result of superposition of wrench-dominatedregional transpression on final emplacement. Journal ofStructural Geology, 27, 805–822.Zulauf, G., Do¨ rr, W., Fiala, J. & Vejnar, Z., 1997. Late Cadomiancrustal tilting and Cambrian transtension in the Tepla-Barrandian unit (Bohemian Massif, Central European Variscides).Geologische Rundschau, 86, 571–584.Zulauf, G., Bues, C., Do¨ rr, W. & Vejnar, Z., 2002. 10 km minimumthrow along the West Bohemian shear zone: evidencefor dramatic crustal thickening and high topography inBohemian Massif (European Variscides). International Journalof Earth Sciences, 91, 850–864.SUPPORTING INFORMATIONAdditional Supporting Information may be found inthe online version of this article:Appendix S1. Radiometric ages used for histogramcalculations in Fig. 2.Appendix S2. Mineralogical densities used as startingvalues in three-dimensional gravity modelling.Please note: Wiley-Blackwell are not responsible forthe content or functionality of any supporting materialssupplied by the authors. Any queries (other thanmissing material) should be directed to the correspondingauthor for the article.Received 26 February 2010; revision accepted 16 August 2010.Ó 2010 Blackwell Publishing Ltd230
J. metamorphic Geol., 2005, 23, 649–666 doi:10.1111/j.1525-1314.2005.00601.xContrasting textural record of two distinct metamorphic events ofsimilar P–T conditions and different durationsO. LEXA, 1,2 P. ŠTÍPSKÁ, 1,2 K. SCHULMANN, 1,2 L. BARATOUX 1 AND A. KRÖNER 31 Institute of Petrology and Structural Geology, Charles University, Albertov 6, 128 43 Prague, Czech Republic(lexa@natur.cuni.cz)2 Université Louis Pasteur, CGS/EOST, UMR 7517, 1 rue Blessig, Strasbourg 67084, France3 Institut für Geowissenschaften, Universität Mainz, 55099 Mainz, GermanyABSTRACTA structural, metamorphic and geochronological study of the Stare´ Meˇsto belt implies the existence oftwo distinct metamorphic events of similar peak P–T conditions (700–800 °C, 8–10 kbar) during theCambro-Ordovician and the Carboniferous tectonometamorphic events. The hypothesis of two distinctperiods of metamorphism was suggested on the basis of structural discordance between an undoubtedlyCarboniferous granodiorite sill intrusion and earlier Cambro-Ordovician fabrics of a bandedamphibolite complex. The analysis of crystal size distribution (CSD) shows high nucleation density(N 0 ) and low average growth rate (Gt) for Carboniferous mylonitic metagabbros and myloniticgranodiorites. The parameter N 0 decreases whereas the quantity Gt increases towards highertemperatures progressively approaching the values obtained from the Cambro-Ordovician bandedamphibolite complex. The spatial distribution of amphibole and plagioclase shows intense mechanicalmixing for lower-temperature mylonitic metagabbros. In high-temperature mylonites a strong aggregatedistribution is developed. Cambro-Ordovician amphibolites unaffected by Carboniferous deformationshow a regular to anticlustered spatial distribution resulting from heterogeneous nucleation of individualphases. This pattern, together with CSD, was subsequently modified by the grain growth and texturalequilibration controlled by diffusive mass transfer during Carboniferous metamorphism. The differencesbetween the observed textures of the amphibolites are interpreted to be a consequence of the differentdurations of the Carboniferous and Cambro-Ordovician thermal events.Key words: Cambro-Ordovician and Carboniferous metamorphism; quantitative textural analysis;crystal size distributions; grain contact frequencies.INTRODUCTIONIdentifying distinct metamorphic episodes in domainswith a polymetamorphic history is possible providingthe P–T conditions of a younger metamorphic eventare markedly different from those of a preceding one.The problem becomes more complex when the morerecent metamorphic event affects units which previouslysuffered a metamorphic event of a similar grade.In this particular case it is only the geological contextand geochronological data that can indicate the existenceof distinct tectonometamorphic episodes.Polymetamorphic domains are commonly studiedusing analysis of polyphase deformations and individualtectonic events are attributed to distinctdeformational phases (Turner & Weiss, 1963). Infavourable situations tectonic regimes responsible forthe formation of two distinct deformational phases canbe distinguished. However, polyphase structures commonlyresult from the continuous activation of localmechanical instabilities during a single deformationevent (Burg, 1999).The tools of metamorphic petrology are able toprovide P–T estimates of peak metamorphic conditions,and important fragments of P–T paths can bereconstructed when thermodynamic modelling isapplied (Powell & Holland, 1988). However, metamorphicand phase petrology do not reveal informationabout the duration of metamorphic events.The time span between individual metamorphicdeformationevents and the duration of metamorphicreworking can be determined in principle bygeochronology.When metamorphic rocks are reworked by a followingtectonometamorphic event after a significantperiod of time but under similar P–T conditions, it isunlikely that the duration of events, strain rates andkinematics of deformation are also the same. However,the texture of metamorphic tectonites results fromnucleation, grain growth and various recrystallizationmechanisms that are strongly controlled by temperature,time and strain rate/stress ratio (Hickey & Bell,1996). Therefore, the analysis of metamorphic texturesis a method that is capable of distinguishing betweentwo metamorphic events under similar P–T conditionsof different durations.Here, we consider an example of Cambro-Ordovicianmetamorphism associated with crustal thinningÓ 2005 Blackwell Publishing Ltd 649231
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Contentsviii4.7 Schulmann, Konopás
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Dedicated to my wife Markéta, daug
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Foreword 2First topic “Quantitati
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1. Quantitative analysis of deforma
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Chapter 2Mechanisms of lower crusta
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Chapter 3Quantitative analyses ofme
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Bibliography 42Culshaw, N., Beaumon
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Bibliography 44sources and trigger
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Bibliography 46Skrzypek, E., Štíp
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EXHUMATION IN LARGE HOT OROGEN 275m
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Probabi l irequencyProbabi l ireque
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EXHUMATION IN LARGE HOT OROGEN 279y
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EXHUMATION IN LARGE HOT OROGEN 281N
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EXHUMATION IN LARGE HOT OROGEN 283w
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EXHUMATION IN LARGE HOT OROGEN 285a
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EXHUMATION IN LARGE HOT OROGEN 287w
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EXHUMATION IN LARGE HOT OROGEN 291O
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EXHUMATION IN LARGE HOT OROGEN 293r
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EXHUMATION IN LARGE HOT OROGEN 295B
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EXHUMATION IN LARGE HOT OROGEN 297R
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