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44 P. HASALOVÁ ET AL.(a)(b)Fig. 11. Characteristic c-axes preferred orientations of (a) old/relict quartz grains and (b) new quartz grains crystallized from areas ofinferred former melt for all rock types. The c-axis patterns of old/relict quartz grains in type I banded orthogneiss indicate prism Æcæslip system activity whereas in type II, III and IV migmatites basal Æaæ or rhomb Æa + cæ slip systems are dominant with minorprism Æaæ slip. New quartz grains inferred to have crystallized from melt in type I banded orthogneiss to type IV nebulitic migmatiteshow very weak LPO and nearly isotropic distribution of all quartz axes. Equal area projections, lower hemisphere, contoured atinterval of 0.5 times uniform distribution. Foliation is horizontal and lineation is in this plane in the E–W direction. N is the number ofmeasured grains. Maximum densities are marked on the bottom right of each pole figure. The dashed line represents the lowest contourlevel and the grey circle corresponds to the minimum density value.crystallized from melt are commonly weak with theexception of strong LPO of plagioclase in the type Iorthogneiss (Fig. 12f). Such slip-systems are supposedto be secondary and active if grains are in unsuitable(hard) orientation to the dominant slip-system[100](010) (Kruse et al., 2001).DISCUSSIONThis study presents a detailed microstructural andquantitative textural analysis of four types of migmatiticrocks identified in one of the largest (5000 km 2 )migmatitic complex of the eastern Variscan belt. Therock types are interpreted as representing a texturalsequence from banded orthogneiss via stromatic andschlieren migmatites to nebulitic migmatite. The possiblemechanisms that could account for the origin ofthis rock sequence involve: (i) genetically unrelatedmigmatites that have originated from distinct protoliths;(ii) variable degree of in situ partial melting of asingle protolith or different protoliths; and (iii) meltinfiltration from an external source through solid rockin which banded orthogneiss and nebulitic migmatiterepresent genetically linked end-members. Thesehypotheses are discussed further below.Spatial relationships of individual migmatite types withinthe shear zoneThe structural sequence described in this work indicatesan intimate relationship between types I to IIImigmatites and nebulitic type IV migmatite sheets thatcan be interpreted in terms of a shear zone, which wasexploited by rising magma (Brown et al., 1995; Collins& Sawyer, 1996; Brown & Solar, 1998b). We haveshown that the D 2 flat fabrics that cross-cut the steepfoliation S 1 developed at high-temperature solid-stateconditions (Fig. 1). Tajcˇmanova´ et al. (2006) andRacek et al. (2006) described a similar sequence ofsuperposed fabrics in lower crustal rocks several tensof kilometres to the north and south of the studied arearespectively. These authors proposed that the flat D 2deformation fabrics originated due to thrusting oforogenic lower crust over middle crustal units along alarge-scale retrograde shear zone. In agreement withthese authors, we suggest that the D 2 fabrics developedin a thrust related crustal-scale shear zone reportedalready by Urban (1992), Schulmann et al. (1994) andredefined later by Schulmann et al. (2005). The maindifference between other regions is in the degree of D 2reworking, which is so high in the studied area thatÓ 2007 Blackwell Publishing Ltd330
ORIGIN OF FELSIC MIGMATITES 45Fig. 12. Characteristic LPO patterns of K-feldspar (a–d) and plagioclase (e,f). Both feldspars commonly show weak LPO in all rocktypes regardless of the origin of the grains. An exception is the strong LPO of new plagioclase grains in the type I banded orthogneiss(f). K-feldspar usually shows activity of 1/2[110](001) (a,c; type I), but also of [100](010) (b; type IV) and [100](001) (d; type IV) slipsystems. Plagioclase reveals activity of secondary slip systems such as 1/2[1 10] on (001) and (11 1) or 1/2 [1 10] on (001) and (1 1 1)(e,f; type I). Equal area projections, lower hemisphere, contoured at intervals of 0.5 times uniform distribution. Foliation is horizontaland lineation is in this plane in the E–W direction. N is the number of measured grains. Maximum densities are marked on thebottom right of each pole figure. The dashed line represents the lowest contour level and the grey circle corresponds to the minimumdensity value. (f,g) BSE images depicting the microstructural appearance of examples of the measured phases (sample PH60/B).Original plagioclase (g) and K-feldspar (h) aggregates with newly crystallized quartz (white arrow), plagioclase (black arrows) andK-feldspar (grey arrows) are shown.Ó 2007 Blackwell Publishing Ltd331
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“It strikes me that all our knowl
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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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Foreword 4source and freely availab
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1. Quantitative analysis of deforma
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Chapter 2Mechanisms of lower crusta
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2. Mechanisms of lower crustal flow
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Chapter 3Quantitative analyses ofme
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3. Quantitative analyses of metamor
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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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Journal of Structural Geology 23 20
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J. KonopaÂsek et al. / Journal of
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JOURNAL OF GEOPHYSICAL RESEARCH, VO
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SCHULMANN ET AL.: STRAIN DISTRIBUTI
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5 - 2 LEXA ET AL.: COLLISION IN WES
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DTD 5ARTICLE IN PRESSJournal of Str
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DTD 5ARTICLE IN PRESSL. Baratoux et
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Table 1Statistical values of the qu
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Table 2Summary of parameters derive
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J. metamorphic Geol., 2008, 26, 273
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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 289T
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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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Author's personal copyK. Schulmann
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J. metamorphic Geol., 2011, 29, 79-
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HEAT SOURCES AND EXHUMATION MECHANI
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CONTRASTING TEXTURAL RECORD OF TWO
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Contrasting microstructures and def
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TEXTURES OF NATURALLY DEFORMED META
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1.0--0.9__Mg~(Mg2++Fe2+)9 Core of p
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' ~'-----2~--~----TEXTURES OF NATUR
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