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112 J. FRANĚK ET AL.Table 1. Representative microchemical analyses of principal minerals constituting the sample H296-S1 used for calculation of the P–Tpseudosection in Fig. 8.Mineral Grt Grt Bt Kfs Kfs Pl Pl PlSample H296-S1A H296-S1A H296-S1A H296-S1A H296-S1A H296-S1A H296-S1A H296-S1AAnalysis 1 g-c 1 g-r 43 44 45 46 5 47Position core matrix rim matrix matrix core rim core rim very rimSiO 2 38.67 38.79 39.40 65.54 64.95 63.46 63.02 67.40TiO2 na na 4.37 0.00 0.00 0.00 0.00 0.00Al 2 O 3 21.51 21.48 16.88 18.66 18.34 22.66 23.06 20.41FeO 24.93 29.93 12.37 0.00 0.00 0.35 0.00 0.00MnO 0.40 0.44 )0.13 0.00 0.00 0.00 0.00 0.00MgO 5.96 7.99 12.95 0.00 0.00 0.00 0.00 0.00CaO 8.49 1.41 0.00 0.00 0.00 3.76 4.47 2.09Na 2 O na na 0.34 2.48 0.32 9.41 9.17 10.31K 2 O na na 9.73 12.87 15.80 0.16 0.32 0.22Total 99.95 100.05 95.91 99.55 99.42 99.79 100.04 100.43Si 3.00 3.01 3.00 3.01 3.03 2.81 2.79 2.96Ti 0.00 0.00 0.25 0.00 0.00 0.00 0.00 0.00Al 1.97 1.97 1.51 1.01 1.01 1.18 1.20 1.06Fe 3+ 0.04 0.00 0.00 0.00 0.00 0.01 0.00 0.00Fe 2+ 1.58 1.94 0.79 0.00 0.00 0.00 0.00 0.00Mn 0.03 0.03 )0.01 0.00 0.00 0.00 0.00 0.00Mg 0.69 0.93 1.47 0.00 0.00 0.00 0.00 0.00Ca 0.70 0.12 0.00 0.00 0.00 0.18 0.21 0.10Na 0.00 0.00 0.05 0.22 0.03 0.81 0.79 0.88K 0.00 0.00 0.94 0.75 0.94 0.01 0.02 0.01Total 8.00 8.00 8.00 5.00 5.00 5.00 5.01 5.00Prp ⁄ An 0.23 0.31 0.00 0.00 0.18 0.21 0.10Alm ⁄ Ab 0.53 0.64 0.23 0.03 0.81 0.77 0.89Grs ⁄ Or 0.23 0.04 0.77 0.97 0.01 0.02 0.01Sps 0.01 0.01XFe (Fe 2+ ) 0.70 0.68 0.35Na 2 O = 2.76, K 2 O = 4.01, P 2 O 5 = 0.15, H 2 O ) =0.22, H 2 O + = 0.56, CO 2 = 0.03) was modified formodelling by adding 1 mol.% of kyanite to enablea small amount of aluminosilicate to be stable atthe estimated peak metamorphic conditions, as it isobserved in the thin section. The amount of H 2 O=0.33 mol.% was chosen after the construction ofT–M H2O sections, as it allows the garnet X Fe = 0.70 tobe stable in the pseudosection (not shown; see Hasalova´et al., 2008a for approach). The major features of thepseudosection involve melt being stable above 810 °C,biotite stable up to 1.6 GPa and 860 °C, ilmenite stablebelow 1.26 GPa, cordierite stable below 0.7 GPa, anda muscovite-out line heading from 750 °C to 810 °Cat 1.35 GPa and then continuing to 880 °C and2.0 GPa (Fig. 8).The textural features indicate that perthite andminerals included in perthite (kyanite, garnet, biotite,rutile and quartz) belong to the early assemblage,whereas recrystallized plagioclase and K-feldspar,matrix biotite, rutile, ilmenite and quartz belong to alater assemblage. Because of intense D2 recrystallization,the original plagioclase composition is notknown, but the recrystallized monomineralic plagioclasebands and lenses indicate the stability of plagioclasewith alkali feldspar within the S1 structure.Chloritized biotite and probably ilmenite in perthiteporphyroclasts are considered as resulting fromre-equilibration. The flat profile of garnet X Fe isinterpreted as having equilibrated during the laterstage of metamorphism, even for the garnet included inperthite porphyroclasts, whereas strong grossularzoning is consistent with the core composition havingbeen preserved from the early metamorphic stage, andthe rim having equilibrated during the later stage.In the pseudosection, the grossular compositionalisopleth of garnet z(g) = 23 occurs outside the biotitestability field (Fig. 8), whereas biotite also belongs tothe observed peak assemblage. However, the biotitepresentfield is only 0.15 GPa and 30 °C apart from thecompositional isopleth z(g) = 23, and the peak istherefore estimated as the area between these lines,to 1.6)1.8 GPa and 850)880 °C (area 1 in Fig. 8).The X Fe of the garnet (=70) and the grossular contentat the garnet rim (grs = 4) indicate conditions of0.9)1.0 GPa and 825 °C for the second stage (area2 in Fig. 8). An attempt was made to correlate thebiotite composition with the two metamorphic stages,but even if the compositions fit approximately thecalculated values in the pseudosection, it is likelythat the measured range (X Fe = 0.29)0.36, and Ti =0.19)0.26 pfu) reflects partial re-equilibration ondecompression, as does the X Fe of garnet, and thereforecannot be used for more precise estimation ofP)T conditions. The feldspar from the pseudosectioncalculations is not used for thermobarometricÓ 2010 Blackwell Publishing Ltd350
PRECURSOR AND RHEOLOGY OF VARISCAN GRANULITES 113Fig. 8. P–T pseudosection calculated in THERMOCALC software for a felsic granulite sample H296-S1. The indicated P–T path reflectscoarse-grained alkali feldspar growth at peak conditions followed by decompression during S2 fabric development.estimations, because recent models use significantextrapolations from relatively low pressure and temperaturewith respect to the conditions of formation ofthe ternary feldspar of interest (see discussion inSˇtípska´ & Powell, 2005). The lack of a clear differencebetween the chemistry of biotite inclusions and matrixbiotite in the other studied thin sections is interpretedas being due to partial chemical re-equilibration ondecompression, even within perthite porphyroclasts.A decrease in X Fe to 0.68 at some garnet rims in theother studied thin sections (Fig. 7b) may be explainedby further decompression in liquid-absent conditionswhere x(g) decreases, or by heating. Plagioclase coronasaround kyanite reflect decompression (Tajcˇmanova´et al., 2007; Sˇtípska´ et al., 2010).In summary, the peak P–T conditions 1.6)1.8 GPaand 850)880 °C are inferred for the stage when alkalifeldspar porphyroclasts were stable with garnet, kyanite,biotite, rutile, plagioclase and quartz, presumablywithin the S1 layering. The S2 fabric started to developÓ 2010 Blackwell Publishing Ltd351
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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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Table 1Statistical values of the qu
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Table 2Summary of parameters derive
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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 295B
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EXHUMATION IN LARGE HOT OROGEN 297R
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