Quantitative structural analyses and numerical modelling of ...

EXTRUSIONOFLOWERCRUSTINVARISCANOROGEN 61(a)(b)(c)(d) (e) (f)Fig. 6. Field photographs of structures. (a) Development of S2 axial fabric during F2 passive folding in granulites. (b) Transpositionof S2–S3 via mesoscopic similar folds in granulites. (c) Initial S4 in discrete shear zones affecting S3 in the Prachatice granulite massif.(d) Steep S3 only weakly affected by D4, lower grade Kaplice paragneiss in the SE of the transect. (e) S4 crenulation cleavage in amigmatized paragneiss, Varied Group in the NW of the transect. (f) S3 transposed into S4 via crenulations and shear bands, whichare commonly filled with granitic leucosome. Orthogneiss in NW part of the transect.The biotite or sillimanite L3 mineral lineationplunges north to northwest, parallel to the hinges ofthese large folds in the Blansky´ les granulite massifexcept for the northern part of this body, where theyvary from south to east. The well-developed L3 lineationin the Prachatice granulite massif plunges shallowlysubparallel to the strike of the S3. In contrast,the L3 lineation in the Krˇisˇťanov granulite massif ispoorly developed except in the NW corner, where theplunge is generally to the SW (Fig. 8).In the metasedimentary rocks separating the granulitemassifs, the S3 fabrics are well preserved only inthe south, whereas towards the north and west onlyrare outcrop-scale relicts of S3 occur. Ubiquitous syndeformationalpartial melting of paragneisses resultedin stromatitic migmatitic layering parallel to the S3schistosity. The S3 in these metasedimentary rocksstrikes parallel to the S3 in neighbouring granulites; inthe Lhenice Zone the S3 forms a tight vertical N–Selongated fan-like pattern (Figs 4e & 5a) whereas inthe Libín Zone it dips steeply to the southwestunderneath the Krˇisˇťanov granulite massif (Figs 4d &5a). Rocks of the Lhenice Zone have an intense shallowlyN–S-plunging lineation defined by biotite alignment,whereas in the Libı´n Zone a L3 lineation is notdeveloped.Subhorizontal amphibolite facies fabric S4The most prominent fabric in rocks of the traverseis the S4 foliation that generally strikes NE–SWsubparallel to the Moldanubian–Tepla´-Barrandianboundary, in general dipping gently to the NW. Onlyalong the southern edge of the Central BohemianPlutonic Complex and 10 km northwest of thePrachatice granulite massif does the S4 fabric dip tothe SE, forming large-scale open fold-like flexures inthe Monotonous and Varied Groups; a N–S to NE–SW stretching lineation on the S4 fabric is subparallelto the hinges of these flexures. Similar to the S3 fabric,in the vicinity of the granulite massifs, the S4 fabricexhibits significant perturbation as a result of deformationpartitioning and locally attains a steep attitudesubparallel to the S3 fabric (e.g. at the eastern marginof the Blansky´ les granulite massif).Partial melting associated with the S4 fabric in theMonotonous and Varied metasedimentary rocks(Fig. 6e,f) is of lower volume than that associated withÓ 2010 Blackwell Publishing Ltd213