Quantitative structural analyses and numerical modelling of ...

68 J. FRANĚK ET AL.Fig. 12. Interpretative geochronological sketch of Variscan evolution in the Bohemian Massif, as it is related to the traverse.but the speculation that the observed seismic structuremay represent the remnant of a suture zone betweenan unknown plate and the overlying Moldanubiandomain is very poorly constrained. The discontinuousand weakly defined Moho reflections (M1–M4) belowthe Moldanubian crust document systematic deepeningof the Moho from 35 km in the NW to 42 kmin the SE. This deepening is in agreement with theMoho geometry defined by the refraction study ofHrubcova´ et al. (2005) and by the passive seismologyexperiments of Plomerova´ et al. (2005).GRAVITY MODELLING AND VERTICAL EXTENTOF THE FELSIC GRANULITESTo decipher the vertical extent of the granulite massifs,an interpolated grid of Bouguer anomalies coveringmost of the traverse (provided by J. Sˇvancara,unpublished data; Fig. 11d) has been examined. Thearea is dominated by large gravity lows related togranitoids of the Moldanubian Pluton in the SE or tounknown sources in the centre and NW parts. Positiveanomalies are all smaller scale and appear in thesouthern part of the area.Forward gravity modelling in three-dimensions hasbeen undertaken using the IGMAS software (Schmidt& Go¨ tze, 1999), where geological bodies are representedby polyhedrons triangulated between manuallydrawn sections. The only suitable body for such anapproach is the Prachatice granulite massif, the surfaceextent of which correlates with a pronounced circularnegative anomaly. Its lithological homogeneity and thesmoothness of the gravity anomaly suggest that nosignificantly denser bodies (e.g. ultrabasites) areinvolved in this massif. The Krˇisˇťanov granulite massifinduces only a weak negative anomaly possiblyaffected by neighbouring intrusion of denser K–Mgsyenites. The Blansky´ les granulite massif partiallycorrelates with a positive anomaly, despite the densityof the felsic granulites being lower than the surroundingmetasedimentary rocks (Appendix S2),probably as a result of abundance of ultrabasic bodiesÓ 2010 Blackwell Publishing Ltd220