Magmatic history and geophysical signature of a post-collisional intrusive center emplaced near a crustal-scale shear zone: the Plechý granite pluton (Moldanubian batholith, Bohemian Massif)

Abstract

The Plechý pluton, southwestern Bohemian Massif, represents a late-Variscan, complexly zoned intrusive center emplaced near the crustal-scale Pfahl shear zone; the pluton thus provides an opportunity to examine the interplay among successive emplacement of large magma batches, magmatic fabric acquisition, and the late-Variscan stress field associated with strike-slip shearing. The magmatic history of the pluton started with the emplacement of the porphyritic Plechý and Haidmühler granites. Based on gravity and structural data, we interpret that the Plechý and Haidmühler granites were emplaced as a deeply rooted, *NE-SW elongated body; its gross shape and internal fabric (steep *NE-SW magmatic foliation) may have been controlled by the late-Variscan stress field. The steep magmatic foliation changes into flat-lying foliation (particularly recorded by AMS) presumably as a result of divergent flow. Magnetic lineations correspond to a sub-horizontal *NE-SW finite stretch associated with the divergent flow. Subsequently, the Třístoličník granite, characterized by steep margin-parallel magmatic foliation, was emplaced as a crescent-shaped body in the central part of the pluton. The otherwise inward-younging intrusive sequence was completed by the emplacement of the outermost and the most evolved garnet-bearing granite (the Marginal granite) along the southeastern margin of the pluton.

Geochemical variability of granite dykes and small intrusions at the margin of the Granulite Complex in southern Bohemia

“…Our two major granite types show important differences in abundances of several trace elements compared to granites of the Plechý Plu- ;Pertoldová ed. 2006;Verner et al 2009;Breiter et al 2007) (Tab. 14).…”

“…The Plechý Pluton at the western margin of the area of interest was studied recently by Pertoldová ed. (2006), Breiter et al (2007), Siebel et al (2006Siebel et al ( , 2008 and Verner et al (2009). Syn-to post-tectonic emplacement and crystallization of the Plechý Pluton granitoids was dated to 327.1 ± 1.9 and 324.8 ± 3.4 Ma by Pb-Pb zircon evaporation method (Siebel et al 2008).…”

Geophysical and structural pattern of the Knížecí Stolec pluton and its host rocks in the south-western part of the Moldanubian Zone, Bohemian Massif

“…The regional framework of the Moldanubian Zone resulted from several Variscan geodynamic events (e.g. Vrána 1979;Žák et al 2005;Büttner 2007;Schulmann et al 2008Schulmann et al , 2009Verner et al 2008Verner et al , 2009Franěk et al 2011a, b). Crustal thickening (~350-341 Ma) was followed by rapid and polyphase exhumation of lower to mid-crustal rocks associated with large-scale migmatization and regional HT-LP metamorphic overprint at ~341-329 Ma (Kalt et al 1999(Kalt et al , 2000Schulmann et al 2005Schulmann et al , 2008Verner et al 2008;Žák et al 2011).…”

“…Crustal thickening (~350-341 Ma) was followed by rapid and polyphase exhumation of lower to mid-crustal rocks associated with large-scale migmatization and regional HT-LP metamorphic overprint at ~341-329 Ma (Kalt et al 1999(Kalt et al , 2000Schulmann et al 2005Schulmann et al , 2008Verner et al 2008;Žák et al 2011). The youngest geodynamic event was connected with dextral WNW-ESE and NNE-SSW shearing (so-called 'Bavarian phase ', Brandmayr et al 1995;Finger et al 2007;Verner et al 2009). The complex tectonometamorphic history of the Moldanubian Zone and its marginal units was also accompanied by several phases of extensive magmatic activity (see Holub et al 1995 andFinger et al 1997): (i) emplacement of metaluminous, calc-alkaline and high-K calc-alkaline, I-type plutons (e. g. the Central Bohemian Plutonic Complex; ~370-345 Ma; Holub et al 1997;Žák et al 2005;Finger et al 2010;Janoušek et al 2010); (ii) intrusion of the ultrapotassic, magnesium-rich magmas (e. g. the Knížecí Stolec pluton; ~343-335 Ma;Holub 1997;Janoušek and Holub 2007;Verner et al 2008); and finally, (iii) polyphase emplacement of large volumes of peraluminous, S to S/I type granitoids of the Moldanubian Batholith (~332-326 Ma; see Žák et al 2011 …”

“…The collision-related magmatic activity may lead to voluminous mass transfer in these deep-seated domains. Quantitative estimates of the vertical extent of the currently exposed plutons provides a constraint for the extent of this mass transfer, while identification of emplacement mechanisms and regional deformation explains how the transfer took place (e. g. Améglio and Vigneresse 1999;Cruden et al 1999;Verner et al 2009). …”