Variscan granitoids related to shear zones and faults: examples from the Central Sudetes (Bohemian Massif) and the Middle Odra Fault Zone

Abstract

and are accompanied by an increase in the local thermal gradient, as documented by the crystallization of cordierite, andalusite and sillimanite; (5) the increase in the thermal gradient precedes the emplacement of granitoids and their concomitant thermal influence on the country rocks. The granitoids related to the final stages of tectonothermal activity of the shear zones are good-time markers of their evolutionary path. Keywords Granitoid intrusions · Shear zones · Variscan magmatism · The Sudetes IntroductionMagma emplacement along faults and shear zones, and spatial relationships between these structures and granite plutons have been widely discussed (e.g. Paterson and Schmidt 1999;Schmidt and Paterson 2000;Richards 2001;Weinberg et al. 2004Weinberg et al. , 2006Paterson 2006; Archanjo et al. 2008). The discussion has focused on the question whether, and to what extent, magma migration is controlled by faults and shear zones, and on the problem of statistical evaluations of spatial and geometric relationships between populations of igneous bodies and structures in various crustal settings (Paterson and Schmidt 1999). Relatively less attention has been paid to the petrology and internal structural features of the fault-related and shear zone-related granitoids. These problems have recently been investigated in the Central Sudetes (CS) granitoid intrusions (NE part of the Bohemian Massif) and in the Middle Odra Fault Zone (MOFZ; the Wrocław granitoids), which are both spatially and temporally related to large-scale faults and shear zones (including postulated terrane boundaries; Fig. 1). AbstractThe granitoid intrusions of the Central Sudetes (CS) and of the Middle Odra Fault Zone (MOFZ), NE part of the Bohemian Massif, are both spatially and temporally related to large-scale shear zones and faults (including possible terrane boundaries) that provided effective channels for melt migration. Summarizing common features of the CS and MOFZ granitoids, we have delineated a set of characteristics of the fault-related and shear zone-related granitoids: (1) they are mainly generated by partial melting of crustal sources, with variable contribution (or no contribution) of mantle materials; (2) the sheet-like, steeply inclined, narrow and rather small granitoid intrusions are emplaced within shear zones at mid-crustal level (c. 20 km depth), whereas the larger, flat-lying plutons intrude into the upper crust, outside or above these shear zones; (3) the magmatic foliation and lineation in granitoids of the deeper, sheet-like intrusions are concordant with those in the surrounding metamorphic rocks, suggesting that the solidification of granitoids was coeval with the deformation in the shear zones; instead, the magmatic foliation in the shallower and larger dome-like plutons reflects magma flow; (4) ductile, transcurrent movements along the shear zones postdate medium-pressure regional metamorphism This study provides a synthesis of the published data on the petrology, geochemistry and age of the Central Sudetes and Wro...

Monazite stability and the maintenance of Th-U-total Pb ages during post-magmatic processes in granitoids and host metasedimentary rocks: A case study from the Sudetes (SW Poland)

“…The compositionally vari able K³odzko-Z³oty Stok granitoid Pluton con tains mafic en claves and lam pro phyre dykes (e.g., Wierzcho³owski, 1976;Lorenc, 1994;Awdankiewicz, 2007;Bachliñski and Bagiñski, 2007). U-Pb zir con dat ing re vealed an age re cord of 349 to 330 Ma in this com pos ite pluton (Mikulski et al, 2013;Oberc-Dziedzic et al, 2015) and its apophyses (Mikulski and Wil liams, 2014).…”

“…The re cent U-Pb dat ing of zir con from the K³odzko-Z³oty Stok granitoids pro vided an av er age con cordia age of ca. 344 Ma, with two youn ger dates of 329 ± 3 and 326 ± 3 Ma that could be re lated to post-ig ne ous ra dio genic Pb loss (Oberc-Dziedzic et al, 2015). The pre vi ous zir con geo chron ol ogy of the K³odzko-Z³oty Stok granitoids con strained the tim ing of the hypa bys sal magmatism to 341-331 Ma (Mikulski et al, 2013;Mikulski and Wil liams, 2014).…”

Multiphase magmatic activity in the Variscan Kłodzko–Złoty Stok intrusion, Polish Sudetes: evidence from SHRIMP U–Pb zircon ages

“…The projection of the mentioned units into the Sudetes is not universally agreed (Aleksandrowski and Mazur 2002;Winchester et al 2002;Kryza et al 2004;Klomínský et al 2010;Chopin et al 2012;Oberc-Dziedzic et al 2015). We favor Franke's (2012Franke's ( , 2014 unit projection where the Sudetes are attached to the Saxothuringian, Teplá-Barrandian and Moldanubian units, corresponding to the west, central and east Sudetes (Mazur et al 2006;ObercDziedzic et al 2015).…”

“…Previously published zircon U-Pb ages tried to deal with the issue Oberc-Dziedzic et al 2015;Budzyń and Jastrzębski 2016); however, most of the results were for intermediate (granodiorite) and mixed rocks. To answer the question more fully, we aimed for SHRIMP dating of end-member or singletype magmas representing rocks which none of the previous studies had addressed.…”

“…We favor Franke's (2012Franke's ( , 2014 unit projection where the Sudetes are attached to the Saxothuringian, Teplá-Barrandian and Moldanubian units, corresponding to the west, central and east Sudetes (Mazur et al 2006;ObercDziedzic et al 2015). The KZSI is emplaced between the east and central Sudetes (Oberc-Dziedzic et al 2015).…”