Article

K-Ar geochronology of different tectonic units at the northeastern margin of the Bohemian Massif

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Abstract

The polymetamorphic Moldanubian (MO) of the northeasthern margin of the Bohemian Massif has been thrust to the north onto the mainly Paleozoic sedimentary Saxothuringian of the Fichtelgebirge (FG). These two units have undergone polyphase deformation and the last regional event to affect both units was a low-pressure metamorphism in which temperatures decreased towards the north.In contrast, the nappe units of the Erbendorf-Vohenstrauss Zone (ZEV) and the Erbendorf Greenschist Zone (EGZ), which partly cover the border of the Moldanubian and the Saxothuringian, and the Münchberg nappe pile (MM), which lies on the Saxothuringian, were in parts subjected to a late medium-pressure metamorphic event.The ZEV, the EGZ, the MO and the FG are intruded by Late Carboniferous granites.Conventional K-Ar analyses, mainly of hornblendes and muscovites from the autochthonous FG and MO, the units beneath the nappes, have yielded exclusively Carboniferous dates. The oldest dates point to a regional cooling of the rocks which outcrop at the present-day surface at about 330-320 Ma, i.e., at the Early-Late Carboniferous boundary. The Late Carboniferous cooling history was largely governed by the thermal influence of the post-kinematic granites (320-295 Ma), especially in the FG and the northern MO.The high-grade metamorphic rocks in the western part of the ZEV and in the upper three nappes of the MM mostly yield dates around 380 Ma i.e., Early Devonian. The results show a relatively wide scatter. Moreover, biotites frequently appear to be older than the coexisting muscovites. Both observations indicate that the rocks underwent a later thermal influence. Whether some groups of older dates (e.g., 400 Ma) are due to excess argon or to inherited argon is still open to discussion.Slightly scattered muscovite dates around 366 Ma were obtained for the prasinite-phyllite series, one of the lower nappes of the MM. A single hornblende from the EGZ gave the same age. These two nappes have, therefore, probably been affected by a Late Devonian thermal and/or tectonic event.The muscovite dates obtained from the Paleozoic Bavarian lithofacies, the lowermost nappe of the MM∗, and the hornblende dates from the eastern part of the ZEV are indistinguishable from those of the autochthonous units FG and MO.

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... The MMC in northeastern Bavaria is located in the northwestern portion of the Bohemian Massif ( Fig. 1) and forms an oval-shaped complex (~25 9 15 km 2 ), extending from the village of Bad Berneck in the south to the town of Hof in the north. As part of the Saxo-Thuringian Zone (STZ), the metamorphism of the MMC took place during the Variscan orogeny (Gebauer & Gr€ unenfelder, 1979;Kreuzer et al., 1989Kreuzer et al., , 1993Stosch & Lugmair, 1990;Hammerschmidt & Franz, 1992). This orogeny resulted from the movement of Gondwana to the northwest and its collision with Laurussia (Lauren-tia+Baltica) to form Pangaea (Franke, 1989;Linnemann et al., 2003;Massonne & O'Brien, 2003;Massonne, 2005;Linnemann & Romer, 2010;Arenas et al., 2014). ...
... This nappe pile is subdivided from the bottom to the top into the following units: Prasinit-Phyllit, Rand-Amphibolit, Liegendserie, and Hangendserie (e.g. Stettner, 1960a;Kreuzer et al., 1989;Okrusch et al., 1989). The Prasinit-Phyllit unit mainly consists of greenschist facies metavolcanic and metasedimentary rocks. ...
... Kreuzer et al. (1993) obtained an age of 379 AE 1 Ma (Ar-Ar plateau and K-Ar isochron), studying muscovite and hornblende from eclogite. Kreuzer et al. (1989) got different ages (410-345 Ma) for the metamorphism in all four units of the MMC, applying the K-Ar method to biotite, hornblende and muscovite. The above ages clearly point to major Middle to Late Devonian metamorphic events during the early Variscan orogenesis in the MMC (Massonne & O'Brien, 2003). ...
Article
Small oval-shaped, unshielded monazite grains found in a Variscan garnet-muscovite-bearing mylonitic paragneiss from the Liegendserie unit of the Münchberg Metamorphic Complex (MMC) in the northwestern Bohemian Massif, central Europe, yield only pre-Variscan ages. These ages, determined with the electron microprobe, have maxima at about 545, 520 and 495 Ma and two side-maxima at 455 and 575 Ma, and are comparable with previously determined ages of detrital zircon reported from paragneisses elsewhere in the NW Bohemian Massif. The pressure (P) - temperature (T) history of this mylonitic paragneiss, determined from contoured P-T pseudosections, involved an initial stage at 6 kbar/600 °C, reaching peak P-T conditions of 12.5 kbar/670 °C with partial melting, followed by mylonitization and retrogression to 9 kbar/610 °C. The monazite, representing detrital grains derived from igneous rocks of a Cadomian provenance between 575–455 Ma, has survived these Variscan metamorphic/deformational events unchanged because this mineral has probably never been outside its P-T stability field during metamorphism. This article is protected by copyright. All rights reserved.
... We have focused on an area between the dominantly medium-grade metamorphic rocks of the Münchberg metamorphic complex (MC) and the Erzgebirge crystalline complex (EC) of the SZ. For this area, the northern portion of the Fichtelgebirge crystalline complex (FC, Kreuzer et al., 1989), P-T-t paths were not reconstructed so far probably because the dominant rocks are of low metamorphic grade. These lowgrade rocks are pelitic and psammitic rift-related metasediments with intercalated acidic metavolcanics (called "epigneisses") resembling nearby Cambro-Ordovician rocks of the Thuringian lithofacies (Emmert et al., 1981;Mingram and Rötzler, 1999;Stettner, 1975Stettner, , 1980. ...
... However, geological mapping campaigns have also revealed a (Stettner, 1981). CB, Cheb basin; MLC, Mariánské Lázně Complex; MO, Moldanubian zone; ST, Saxothuringian zone; ZEV, Zone of Erbendorf-Vohenstauß; ZTM, Zone of Tirschenreuth-Mähring (see Kreuzer et al., 1989). km-wide strip of garnet-bearing medium grade metamorphic rocks (Stettner, 1958) between the low-grade metasediments and the main bodies of late Variscan granites in the FC. ...
... (iii) The Micaschist-Eclogite Unit is composed of chloritoid-and garnet-bearing micaschists (Konopásek et al., 2001;Rötzler et al., 1998) with intercalations of quartzite, marble (Gross et al., 2008) and eclogite (Massonne and Kopp, 2005). The Arzberg Series of the FC could be correlated with this unit (Hecht et al., 1999;Kreuzer et al., 1989). (iv) The (Garnet)-Phyllite Unit forms a mantle around the gneiss dome of the EC. ...
Article
The studied micaschist from the northeastern Fichtelgebirge crystalline complex (FC) contains mm-sized garnet with a foam structure. Staurolite formed at the margin of garnet. Relics of staurolite are enclosed in mm-sized andalusite porphyroblasts. Garnet exhibits prograde concentric zonation with the pyrope component increasing from 1 to 6 mol%. Cores of potassic white-mica grains locally contain Si contents up to 3.15 per formula unit (pfu). The majority of this mica is characterized by Si contents close to 3.00 pfu. Pressure-temperature (P-T) pseudosections, calculated for the micaschist, indicate conditions of 10 kbar and 505 °C for an early metamorphic stage which was followed by a pressure decrease to 5 kbar and 535 °C. Late metamorphic P-T conditions recorded by garnet are around 4.5 kbar and 565 °C, compatible with the presence of staurolite. Andalusite might have metastably formed at this stage or somewhat lower pressures. The U-Th-Pb dating of monazite with the electron microprobe yielded subordinate ages younger than 315 Ma which were assigned to the nearby emplacement of granites in the FC. Some ages older than 395 Ma were related to detrital monazite in the sedimentary protolith of the micaschist. An age cluster at 384.5 ± 1.8 (2σ) Ma is preferentially assigned to the early high-pressure (HP) metamorphism resulting from the collision of Laurussia with a Peri-Gondwanan terrane. Exhumation to 15–20 km depths might have ended at 362.3 ± 1.0 Ma, but possibly the HP metamorphism occurred at this age and the 384.5 Ma age must be then referred to the provenance area of detrital monazite. The age cluster at 325.0 ± 0.7 Ma is related to a second collisional event that caused the overriding of the crystalline nappes of the FC onto the Laurussian crust.
... interpreted as transition units between the Saxothuringian and úoldanubian terranes (Kreuzer et al' 1989, Vejnar 1991. They are charactenzed by a strong late Variscan LP-HT imprint dated at 33o -32o Ma (Kreuzer et al. 1989) in thá German part. ...
... interpreted as transition units between the Saxothuringian and úoldanubian terranes (Kreuzer et al' 1989, Vejnar 1991. They are charactenzed by a strong late Variscan LP-HT imprint dated at 33o -32o Ma (Kreuzer et al. 1989) in thá German part. ...
... Here the metabasalts of the Kladslcí unit are imbricated with the MP garnet amphibolites of the MLC and with gneisses of the Teplá crystalline unit. These units with contrasting P-t histories and different protoliths were brought together during the complicated process of Variscan crustal shortening, which started in the l,ower Devonian and continued up to the Lower Carboniferous (Gebauer & Gninenfelder 1979, Sóllner et al. 1981a,b Můller et al.1987, Stosch & Lugmair 1987, Teufel 1988, Franke 1989, Kreuzer et al. 1989). This mode of occuÍTence of the metabasalts of the Kladská unit implies that these may be present below the MLC and possibly below a part of the Teplá crystďline unit further to the east. ...
... The difference in thermal state between the TBU and the adjacent units is obvious from the U-Pb zircon and monazite data and from the K-Ar and 39 Ar/ 40 Ar cooling ages of the hornblendes, white micas and biotites. These data suggest that from 340 to 330 Ma the Moldanubian Zone (Teufel 1988;Kreuzer et al. 1989;Kalt et al. 2000b;Propach et al. 2000) and high pressure units of the Saxothuringian Zone (Kröner & Willner 1998;Werner & Lippolt 2000) were situated at deep crustal levels where T . c. 5008C, whereas the entire TBU, including the Cadomian basement of the DCC and TCC, was situated at a supracrustal level with T , c. 3508C (see references above). ...
... For example, westward thrusting of an allochthonous eclogite-bearing HP unit has been reported from the central part of the Erzgebirge (Konopasek et al. 2001). The evolution of this huge nappe complex and, thus, the metamorphic layering must be diachronous, as also indicated by the geochronological and stratigraphic constraints for different tectonometamorphic units (Kreuzer et al. 1989;Kröner & Willner 1998;Werner & Lippolt 2000). ...
... The difference in thermal state between the TBU and the adjacent units is obvious from the U-Pb zircon and monazite data and from the K-Ar and 39 Ar/ 40 Ar cooling ages of the hornblendes, white micas and biotites. These data suggest that from 340 to 330 Ma the Moldanubian Zone (Teufel 1988;Kreuzer et al. 1989;Kalt et al. 2000b;Propach et al. 2000) and high pressure units of the Saxothuringian Zone (Kröner & Willner 1998;Werner & Lippolt 2000) were situated at deep crustal levels where T . c. 5008C, whereas the entire TBU, including the Cadomian basement of the DCC and TCC, was situated at a supracrustal level with T , c. 3508C (see references above). ...
... For example, westward thrusting of an allochthonous eclogite-bearing HP unit has been reported from the central part of the Erzgebirge (Konopasek et al. 2001). The evolution of this huge nappe complex and, thus, the metamorphic layering must be diachronous, as also indicated by the geochronological and stratigraphic constraints for different tectonometamorphic units (Kreuzer et al. 1989;Kröner & Willner 1998;Werner & Lippolt 2000). ...
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... A few older but still Palaeozoic ages were related to the formation of protoliths. Cooling ages (Rb-Sr, K-Ar, Ar-Ar), for instance, for eclogites of the Münchberg Massif fall mainly in the range 380 to 365 Ma (Söllner et al., 1981;Kreuzer et al., 1989;Stosch & Lugmair, 1990;Hammerschmidt & Franz, 1992). The relatively short time interval between the eclogite facies stage and a stage after considerable exhumation (or at least cooling) is also confirmed by chemical zonation patterns of garnet to which the method of cation diffusion modelling was applied (O'Brien, 1997). ...
... In general, the quartzofeldspathic country rocks, hosting the various eclogitic and ultramafic bodies, show the same metamorphic ages (and cooling ages) as the basic and ultrabasic HP and UHP rocks (Münchberg Massif and zone of Erbendorf-Vohenstrauß: Kreuzer et al., 1989;Góry Sowie: van Breemen et al., 1988;O'Brien et al., 1997b;Bröcker et al., 1998;Granulitgebirge: von Quadt, 1993;; Erzgebirge and adjacent areas (Ohře Crystalline Complex): Kotková et al., 1995;Kröner & Willner, 1998;Śnieżnik: Borkowska et al., 1990; Gföhl unit: see summary in Petrakakis, 1997;Kröner et al., 2000). In addition, peak temperatures of the country rocks are at least similar to those of the eclogite bodies. ...
... A few older but still Palaeozoic ages were related to the formation of protoliths. Cooling ages (Rb-Sr, K-Ar, Ar-Ar), for instance, for eclogites of the Münchberg Massif fall mainly in the range 380 to 365 Ma (Söllner et al., 1981;Kreuzer et al., 1989;Stosch & Lugmair, 1990;Hammerschmidt & Franz, 1992). The relatively short time interval between the eclogite facies stage and a stage after considerable exhumation (or at least cooling) is also confirmed by chemical zonation patterns of garnet to which the method of cation diffusion modelling was applied (O'Brien, 1997). ...
... In general, the quartzofeldspathic country rocks, hosting the various eclogitic and ultramafic bodies, show the same metamorphic ages (and cooling ages) as the basic and ultrabasic HP and UHP rocks (Münchberg Massif and zone of Erbendorf-Vohenstrauß: Kreuzer et al., 1989;Góry Sowie: van Breemen et al., 1988;O'Brien et al., 1997b;Bröcker et al., 1998;Granulitgebirge: von Quadt, 1993;; Erzgebirge and adjacent areas (Ohře Crystalline Complex): Kotková et al., 1995;Kröner & Willner, 1998;Śnieżnik: Borkowska et al., 1990; Gföhl unit: see summary in Petrakakis, 1997;Kröner et al., 2000). In addition, peak temperatures of the country rocks are at least similar to those of the eclogite bodies. ...
... The ZEV is comprised of various metasediments and metabasites, some of which contain relicts of a HP, eclogite-facies, metamorphism (O'Brien and Carswell, 1993). Previous geochronology, using the U-Pb zircon and Sm-Nd Grt-WR methods suggest the eclogite-facies event occurred at around 398 Ma (Von Quadt, 1990) and subsequent amphibolite-facies metamorphism has been constrained to 400-370 Ma based on K-Ar hornblende, biotite, and muscovite methods (Ahrendt et al., 1997;Kreuzer et al., 1989;Teufel, 1988). However, the limited exposures and poor preservation of eclogite-facies assemblages have precluded more detailed study of the ZEV HP rocks. ...
... Lu-Hf garnet-omphacite geochronology has previously been applied to the MM and yielded ages of 405 ± 7 Ma, 398 ± 6 Ma, 397 ± 7, and 384 ± 6 Ma (Scherer et al., 2002). In addition, Stosch and Lugmair (1990) previously calculated a Sm-Nd isochron for the MM, which yielded an age of 395-380 Ma and K-Ar hornblende and muscovite dating yielded 390-376 Ma (Kreuzer et al., 1989). The similarity in the age data from the MM and MLC supports the notion that they were part of the same subduction/exhumation system. ...
Article
Lu-Hf and Sm-Nd garnet-whole rock geochronology combined with petrographic observations, minero-chemical variations, thermodynamic modelling and structural data was used to constrain the P–T–t–d evolution of eclogites from the Mariánské Lázně Complex (Bohemian Massif). Boudins of mostly isotropic eclogite with relict steep eclogite-facies fabric are affected by steep migmatitic foliation, which is followed on a regional scale by the development of almost pervasive, predominantly SE-dipping, extensional foliation. The structural succession shows continuous transition from eclogite to garnetiferous migmatitic amphibolite and to amphibolite migmatite. A least retrogressed sample of eclogite shows clusters of fine-grained inclusion-poor garnet, omphacite relicts surrounded by a fine-grained clinopyroxene-plagioclase symplectite with minor amphibole, biotite-plagioclase intergrowths after white mica, kyanite with plagioclase-spinel coronas and accessory rutile. Rare potassic white mica occurs as inclusions in omphacite. A more retrogressed eclogite, with no omphacite or kyanite relicts, contains inclusion-poor garnet surrounded by amphibole-plagioclase corona in a matrix dominated by plagioclase-amphibole symplectite with minor clinopyroxene. In places, the symplectite is overgrown by coarse-grained amphibole. Peak P–T conditions, inferred from combined conventional thermobarometry and phase-equilibria modelling and based on inclusions of white mica (up to 3.33 Si p.f.u.), matrix omphacite (Jd33–36) and garnet core (Alm33–38Prp38–42Grs22–25Sps1) compositions are ~25 kbar at 650–750 °C. A HT overprint occurred at ~14–18 kbar and >800 °C based on coexisting clinopyroxene (Jd18–24), plagioclase (An18–35), and amphibole (Na(B) <0.20; Al(C) = 0.60–1.15) in symplectite after original omphacite and phase-equilibria modelling of garnet mantle compositions. Lu-Hf and Sm-Nd garnet geochronology has been applied to both samples, an older age (c. 390 Ma) obtained by the Lu-Hf method is interpreted as the timing of HP metamorphism, while c. 15 Ma younger ages were obtained by the Sm-Nd method. As temperatures for the HT overprint exceed the empirically and experimentally determined closure temperature of the Sm-Nd system the Sm-Nd ages are interpreted to date cooling following the HT overprint. Combined together, contrasting eclogite and amphibolite-facies migmatite fabrics, the mineral textures, calculated P–T conditions, and distinct Lu-Hf and Sm-Nd ages, provide a complete P–T–t–D path characterised by rapid (~15 Ma) transition from HP subduction, crustal thickening to extensional HT shearing. This unconventional exhumation path does not fit to models of monocyclic exhumation in a subduction channel proposed for the Münchberg and ZEV Devonian HP units to the west. In contrast, the post-peak extensional low angle shearing shortly after subduction and collision resembles more the geodynamic model typical for the Iberian subduction system both in time scales and sequence of tectonic events.
... The difference in thermal state between the TBU and the adjacent units is obvious from the U-Pb zircon and monazite data and from the K-Ar and 39 Ar/ 40 Ar cooling ages of the hornblendes, white micas and biotites. These data suggest that from 340 to 330 Ma the Moldanubian Zone (Teufel 1988;Kreuzer et al. 1989;Kalt et al. 2000b;Propach et al. 2000) and high pressure units of the Saxothuringian Zone (Kröner & Willner 1998;Werner & Lippolt 2000) were situated at deep crustal levels where T . c. 5008C, whereas the entire TBU, including the Cadomian basement of the DCC and TCC, was situated at a supracrustal level with T , c. 3508C (see references above). ...
... For example, westward thrusting of an allochthonous eclogite-bearing HP unit has been reported from the central part of the Erzgebirge (Konopasek et al. 2001). The evolution of this huge nappe complex and, thus, the metamorphic layering must be diachronous, as also indicated by the geochronological and stratigraphic constraints for different tectonometamorphic units (Kreuzer et al. 1989;Kröner & Willner 1998;Werner & Lippolt 2000). ...
... Here, the tectonometamorphic record indicates initial collision between Laurussia and Peri-Gondwana in Lower Devonian rocks at 400 Ma (e.g. Kreuzer et al. 1989;Schaltegger et al. 1996;Lardeaux et al. 2001;Nutman et al. 2001;Ordóñez Casado et al. 2001;Lucks et al. 2002;Kryza & Fanning, 2007;Bröcker et al. 2009;Berger et al. 2010), whereas continental crust of the East African-Arabian Zircon Province is not affected by collisional tectonics before the Carboniferous period, i.e. c. 50 Ma later (Dallmeyer et al. 1997;Giacomini, Bomparola & Ghezzo, 2005;Rubatto et al. 2010;Langone et al. 2011;Martínez Catalán et al. 2014). Hence, the West African Zircon Province can be regarded as the leading edge of Peri-Gondwana, i.e. the Armorican Spur (Kroner & Romer, 2013), during the collision of Gondwana and Laurussia. ...
Article
We present a statistical approach to data mining and quantitatively evaluating detrital age spectra for sedimentary provenance analyses and palaeogeographic reconstructions. Multidimensional scaling coupled with density-based clustering allows the objective identification of provenance end-member populations and sedimentary mixing processes for a composite crust. We compiled 58 601 detrital zircon U–Pb ages from 770 Precambrian to Lower Palaeozoic shelf sedimentary rocks from 160 publications and applied statistical provenance analysis for the Peri-Gondwanan crust north of Africa and the adjacent areas. We have filtered the dataset to reduce the age spectra to the provenance signal, and compared the signal with age patterns of potential source regions. In terms of provenance, our results reveal three distinct areas, namely the Avalonian, West African and East African–Arabian zircon provinces. Except for the Rheic Ocean separating the Avalonian Zircon Province from Gondwana, the statistical analysis provides no evidence for the existence of additional oceanic lithosphere. This implies a vast and contiguous Peri-Gondwanan shelf south of the Rheic Ocean that is supplied by two contrasting super-fan systems, reflected in the zircon provinces of West Africa and East Africa–Arabia.
... Dieser devonische Flysch ist ganz offenbar der suprakmstale Ausdruck der druckbetonten Metamorphose und anschließenden Heraushebung, die in der Münchberger Gneismasse, in der ZEV und in der Zone von Tepl-Taus ( Z n ) zu etwa der gleichen Zeit nachgewiesen ist. Die sehr enge zeitliche Nachbarschaft von Zirkon (U-Pb)-, Hornblende (K-Ar, Ar-Ar)-und Glimmer (Rb-Sr, K-Ar, &-&)-Alternfast innerhalb der Fehlergrenzendeutet auf eine rasche Heraushebung hin (siehe Zusammenstellungen und Diskussionen in FRANKE et al. in prep., HANSEN et al. 1989, KREUZER et al. 1989 Ergebnisse laufender Untersuchungen von detritischen Zirkonen aus den Erbendorfer Grauwacken sind mit der Vermutung vereinbar, daß altvariscisches Kristallin bereits i m Devon angehoben und abgetragen worden ist: Die Grauwacke enthält Zirkone mit einer ähnlichen U-Pb-Systematik wie die von TEUFEL (1988) beschriebenen aus Paragneisen der Zone von Erbendorf/Vohenstrauß (ZEV) (W.DÖRR, unveröff.). ...
... Like other crystalline bodies in the European Variscides, the Bohemian Massif was assembled during the Late Devonian-Permian (so-called Variscan) orogeny. The Variscan orogenic evolution of the Bohemian Massif is well constrained by high-temperature geochronometers and thermochronometers (i.e., U/Pb, Pb/Pb, Sm/Nd, Rb/Sr, Ar/Ar, sphene and zircon fission track) [e.g., Jarmołowicz-Szulc, 1984;Kreuzer et al., 1989;Košler et al., 1995Košler et al., , 2001Kotková et al., 1996;Kröner and Willner, 1998;Kröner and Hegner, 1998;Propach et al., 2000;Thomson and Zeh, 2000;Janoušek et al., 2010;Schulmann et al., 2005;Schneider et al., 2006;Siebel et al., 2008;Awdankiewicz et al., 2010]; however, its low-temperature (i.e., <240°C), postorogenic evolution is a matter of debate, particularly due to the sparsely preserved post-Permian geologic record [e.g., Wagner et al., 1997;Glasmacher et al., 2002;Ventura and Lisker, 2003;Filip and Suchý, 2004;Aramowicz et al., 2006;Ventura et al., 2009;Danišík et al., 2010;Siebel et al., 2010]. 1 [4] Previous low-temperature studies based primarily on bedrock apatite fission track data ($120-60°C sensitivity) [Wagner and Van den Haute, 1992] identified several cooling events throughout the Mesozoic-Cenozoic [Jarmołowicz-Szulc, 1984;Wagner et al., 1989Wagner et al., , 1997Hejl et al., 1997;Coyle et al., 1997;Thomson and Zeh, 2000;Glasmacher et al., 2002;Ventura and Lisker, 2003;Aramowicz et al., 2006;Filip et al., 2007;Ventura et al., 2009;Danišík et al., 2010]. These studies suggest that the Bohemian Massif experienced a complex thermal postorogenic evolution that may have been influenced by various processes. ...
Article
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Reconstructing erosional and faulting history in the old crystalline basement terrains, with lacking or sparse post-tectonic geological records, is a challenging task where even radiometric data on the basement rocks need not to provide ultimate answers. NE part of the Bohemian Massif (known as the Sudetes) represents a classic example where numerous attempts to constrain denudation, faulting and relief formation on the Variscan basement, often based on incomplete lines of evidence, led to formulation of controversial models. In this study we aim to reconstruct the post-orogenic exhumation history of the Rychlebské hory Mts. in the eastern Sudetes and constrain paleo-activity along the Sudetic Marginal Fault (SMF) - one of the morphologically most prominent, but poorly understood features of Central Europe, forming a >140 km long escarpment separating the Sudetic Mountains from the foreland in the northeast. We do so by applying zircon (U-Th)/He (ZHe), apatite fission track (AFT) and apatite (U-Th)/He (AHe) dating methods to the basement samples from different fault-bounded blocks and sparsely preserved post-orogenic sedimentary samples. New thermochronological data reveals that in the Late Cretaceous at ~95-80 Ma, the Carboniferous-Permian basement blocks SW and NE of the SMF were buried to ~4-7 km and >6.5 km depths, respectively, by sediments of the Bohemian Cretaceous Basin System. This finding contradicts the traditional paleogeographic reconstructions suggesting exposure of large portions of the Sudetes for most of the Mesozoic-Cenozoic. During the burial, the SMF acted as a normal fault as documented by offset in ZHe ages across the fault. At 85-70 Ma, the basin was inverted, Cretaceous strata eroded and basement blocks were exhumed to the near-surface at exhumation rate of ~300 m/Ma as evidenced by Late Cretaceous-Paleocene AFT ages and thermal modelling results. There is no appreciable difference in AFT and AHe ages across the fault suggesting that the SMF acted as a reverse fault during the exhumation. In the Late Eocene-Oligocene, the basement was locally heated to <~70°C in a response to thermal activity related to opening of the Eger rift system and associated magmatism. No signal of Neogene or Quaternary thermal activity in the thermochronological data confirms that Late Cenozoic uplift and erosion of the basement blocks resulting in the present-day topography did not exceed ~1.5 kilometres in the study area. This study highlights the importance of mutli-system thermochronological applications and the critical role of post-tectonic sediments in reconstructing histories of old crystalline basement terrain. More details can be found in Danišík et al. (2012).
... Like other crystalline bodies in the European Variscides, the Bohemian Massif was assembled during the Late Devonian-Permian (so-called Variscan) orogeny. The Variscan orogenic evolution of the Bohemian Massif is well constrained by high-temperature geochronometers and thermochronometers (i.e., U/Pb, Pb/Pb, Sm/Nd, Rb/Sr, Ar/Ar, sphene and zircon fission track) [e.g., Jarmołowicz-Szulc, 1984;Kreuzer et al., 1989;Košler et al., 1995Košler et al., , 2001Kotková et al., 1996;Kröner and Willner, 1998;Kröner and Hegner, 1998;Propach et al., 2000;Thomson and Zeh, 2000;Janoušek et al., 2010;Schulmann et al., 2005;Schneider et al., 2006;Siebel et al., 2008;Awdankiewicz et al., 2010]; however, its low-temperature (i.e., <240°C), postorogenic evolution is a matter of debate, particularly due to the sparsely preserved post-Permian geologic record [e.g., Wagner et al., 1997;Glasmacher et al., 2002;Ventura and Lisker, 2003;Filip and Suchý, 2004;Aramowicz et al., 2006;Ventura et al., 2009;Danišík et al., 2010;Siebel et al., 2010]. 1 [4] Previous low-temperature studies based primarily on bedrock apatite fission track data ($120-60°C sensitivity) [Wagner and Van den Haute, 1992] identified several cooling events throughout the Mesozoic-Cenozoic [Jarmołowicz-Szulc, 1984;Wagner et al., 1989Wagner et al., , 1997Hejl et al., 1997;Coyle et al., 1997;Thomson and Zeh, 2000;Glasmacher et al., 2002;Ventura and Lisker, 2003;Aramowicz et al., 2006;Filip et al., 2007;Ventura et al., 2009;Danišík et al., 2010]. These studies suggest that the Bohemian Massif experienced a complex thermal postorogenic evolution that may have been influenced by various processes. ...
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The Rychlebské hory Mountain region in the Sudetes (NE Bohemian Massif) provides a natural laboratory for studies of postorogenic landscape evolution. This work reveals both the exhumation history of the region and the paleoactivity along the Sudetic Marginal Fault (SMF) using zircon (U-Th)/He (ZHe), apatite fission track (AFT), and apatite (U-Th)/He (AHe) dating of crystalline basement and postorogenic sedimentary samples. Most significantly, and in direct contradiction of traditional paleogeographic reconstructions, this work has found evidence of a large Cretaceous sea and regional burial (to >6.5 km) of the Carboniferous-Permian basement in the Late Cretaceous (˜95-80 Ma). During the burial by sediments of the Bohemian Cretaceous Basin System, the SMF acted as a normal fault as documented by offset ZHe ages across the fault. At 85-70 Ma, the basin was inverted, Cretaceous strata eroded, and basement blocks were exhumed to the near surface at a rate of ˜300 m/Ma as evidenced by Late Cretaceous-Paleocene AFT ages and thermal modeling results. There is no appreciable difference in AFT and AHe ages across the fault, suggesting that the SMF acted as a reverse fault during exhumation. In the late Eocene-Oligocene, the basement was locally heated to <70°C by magmatic activity related to opening of the Eger rift system. Neogene or younger thermal activity was not recorded in the thermochronological data, confirming that late Cenozoic uplift and erosion of the basement blocks was limited to less than ˜1.5 km in the study area.
... In the northern Bohemian Massif Silurian -Early/ Middle Devonian ages, confined to high-grade metamorphic rocks in the Góry Sowie Block (GSB) (402 Ma;Brueckner et al., 1996;O'Brien et al., 1997) and the Münchberg klippe (395 -390 Ma; Kreuzer et al., 1989;Stosch and Lugmair, 1990), may record local tectonothermal and, hence, collisional activity between migrating platelets of the ATA. These dates are historically and collectively termed Eo-Variscan elsewhere in Hercynian Europe (e.g. ...
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Multidisciplinary studies of geotransects across the North European Plain and Southern North Sea, and geological reexamination of the Variscides of the North Bohemian Massif, permit a new 3-D reassessment of the relationships between the principal crustal blocks abutting Baltica along the Trans-European Suture Zone (TESZ). Accretion was in three stages: Cambrian accretion of the Bruno–Silesian, Lysogory and Malopolska terranes; end-Ordovician/early Silurian accretion of Avalonia; and early Carboniferous accretion of the Armorican Terrane Assemblage (ATA). Palaeozoic plume-influenced metabasite geochemistry in the Bohemian Massif explains the progressive rifting away of peri-Gondwanan crustal blocks before their accretion to Baltica. Geophysical data, faunal and provenance information from boreholes, and dated small inliers and cores confirm that Avalonian crust extends beyond the Anglo-Brabant Deformation Belt eastwards to northwest Poland. The location and dip of reflectors along the TESZ and beneath the North European Plain suggest that Avalonian crust overrode the Baltica passive margin, marked by a high-velocity lower crustal layer, on shallowly southwest-dipping thrust planes forming the Heligoland–Pomerania Deformation Belt. The ‘‘Variscan orocline’’ of southwest Poland masks two junctions between the Armorican Terrane Assemblage (ATA) and previously accreted crustal blocks. To the east is a dextrally transpressive contact Palaeozoic amalgamation of Central Europe: new results from recent geological and geophysical investigations.
... The voluminous gneiss complexes of the Erzgebirge constitute the core of an allochthonous stack, the Fichtelgebirge -Mü nchberg -Erzgebirge Zone (Fig. 1). High pressure (HP) units in upper, middle, and lower allochthonous levels reveal Variscan subduction-exhumation tectonics lasting from $400-365 Ma (Kreuzer et al., 1989;Stosch and Lugmair, 1990), 360-350 Ma (Faryad and Kachlík, 2013) and 340-330 Ma (e.g. Krö ner and Willner, 1998;Tichomirowa et al., 2005; this study, Fig. 2) respectively. ...
Article
Felsic rocks of the Erzgebirge in the Central European Variscides experienced ultra-high pressure metamorphism at ∼340 Ma, followed by nearly isothermal decompression during channel like rapid exhumation within ∼10 Ma. Despite the general time frame of exhumation and emplacement within mid-crustal levels is known, available geochronological data do not provide a detailed timescale of individual stages of the entire process. Addressing this problem we combined white mica ⁴⁰Ar/³⁹Ar ages obtained from multi-grain step heating and multiple single grain total fusion experiments with mineral chemical, structural and tectono-metamorphic constraints. Gneisses of the channel center are characterized by E-W elongated white mica exclusively aligned in the continuous foliation. The rocks of the channel contact zone and in the hanging and footwall contain NW-SE stretched white mica parallel to the foliation, but also components of ductile to brittle-ductile shear bands truncating the main foliation. Well defined weighted plateau ages of all samples range between 340.0 ± 1.1 Ma and 327.9 ± 1.3 Ma, confirming previously published data, but represent presumably mixed ages due to multi-phase deformation. Single grain age distributions, in contrast, exhibit two statistically significant age peaks at 338.6 ± 0.2 Ma and at 332.8 ± 0.3 Ma. Rocks without shear bands exclusively contain white mica belonging to the older age fraction, whereas rocks with shear bands show a broad age scatter including both age fractions. We interpret these age distributions as being independent of closure temperature, but reflecting different dynamic recrystallization events. The older age fraction reflects the formation of the main foliation during west-directed emplacement of the ultra-high pressure rocks in mid-crustal levels at ∼339 Ma, whereas the shear band related neo- or recrystallization is responsible for the younger age fraction dating the final transport in the upper crust at ∼333 Ma.
... The structural uppermost Allochthonous Unit of the Münchberg complex was affected by HP-LT metamorphism at 390 Ma and was thrusted over the Saxo-Thuringian unit at 340 Ma (Kreuzer et al., 1989;Klemd, 2010;Koglin et al., 2018; Table 1). The uppermost allochthonous unit represents an inverted metamorphic gradient of four contrasting nappes or series (from top to bottom): (i) the structurally uppermost "Hangend-Serie" comprises hornblende-bearing gneiss, amphibolite, leucocratic gneiss, and eclogite lenses that represent ca. ...
Article
Global tectonic and climatic models for the Permian-Triassic boundary (PTB) are highly debated. One of the most disputed topics is the temperature increase associated with CO2 emissions generated by the Siberian Trap volcanism and its potential influence on chemical weathering and associated variations in sediment fluxes. By integrating crustal architecture, plate modelling, structural kinematics, and two climatic models, we reconstruct the drainage evolution of Variscan tectonostratigraphic units from the SE portion of the Germanic Basin, from which we also extract the parameters necessary to calculate sediment flux across a time-scale of 28 Ma (Guadalupian-Lower Triassic). We reconstruct the sedimentary response to climatic and tectonic perturbations using Quantitative Provenance Analysis (QPA) and integrate compositional data into a sedimentological framework, paleodrainage and paleoclimatic models. Raman heavy mineral analysis, as well as geochronology and geochemistry of detrital apatite, zircon, and rutile, document variation in drainage lithologies and sediment flux which are controlled by regional extensional tectonics and increasingly humid conditions at the PTB. The sedimentary successions of the SE Germanic Basin record climatic perturbations on a 104 years timescale, while the effects of tectonics are visible on a 106 years timescale. The interplay of climate, tectonics and lithology, and their effects on sediment production and drainage evolution resulted in changes in sediment flux from 2.3 Mt./yr during the Guadalupian (Capitanian), to 3.80 Mt./yr in the Lopingian (Changhsingian) to 7.44 Mt./yr at the end of the Lower Triassic (Olenekian). The multifaceted workflow provided in this study represents the first step towards more precise reconstructions of sediment routing systems in deep-time and provides the first ground-truthed quantification of sediment flux across the Permian-Triassic Boundary.
... GPa at 670°C were estimated for eclogites and calc-silicate rocks (Okrusch et al., 1991;Massonne & O¢ Brien, 2003). The Variscan age of c. 400-380 Ma for eclogite facies metamorphism is constrained by Sm-Nd, Rb-Sr and U-Pb methods (Stosch & Lugmair, 1990) and a 370-360 Ma cooling age according to K-Ar dating of amphibole (Kreuzer et al., 1989). ...
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Blueschist facies rocks, exposed within consolidated continental blocks, provide some of the best evidence for the existence of previous suture(s). They usually occur as lenses or layers embedded within greenschist or amphibolite facies rocks and indicate reequilibration at medium- to low-pressure conditions. In the Bohemian Massif, a few occurrences of blueschists have been reported, and here, new evidence of high-pressure (HP) metamorphism in various lithologies is presented that suggests a larger extent of blueschist facies rocks along the northern border of this Massif. An earlier blueschist facies metamorphism is documented by inclusions of glaucophane in garnet, epidote and titanite from metabasites along with zoned white mica having a phengitic core and a muscovite rim in metapelites and orthogneisses. The estimated P–T conditions, obtained using pseudosections and mineral isopleths, correspond to blueschist and low-temperature eclogite facies conditions (1.1–2.0 GPa at 350–550 °C). Together with medium-temperature eclogites from different units in the Bohemian Massif they indicate a geothermal gradient of 8–10 °C km−1, which is typical for cool subduction. Radiometric dating on phengite from metapelites confirms an early Palaeozoic cooling age of c. 360 Ma for this HP metamorphic event. The presence of blueschist facies rocks, their P–T relations and age constraint together with those from eclogite facies rocks allows us to locate the Variscan suture, which straddles the SE margin of Saxothuringian Zone from Erzgebirge to Sudetes, and its possible continuation to the Moldanubian Zone, where eclogite facies and UHPM rocks are abundant.
... Kreuzer et al. (1989); (4)Romer and Hahne (2010a); (5)Klemd (2010); (6)Rötzler et al. (1999); (7)Kryza et al. (1996); (8)Romer and Rötzler (2001); (9)Rötzler et al. (2004); (10)Rötzler and Romer (2010); (11)Willner et al. (1997); (12)Rötzler et al. (1998); (13)Rötzler and Plessen (2010); (14)Rötzler and Romer (2001);(15)Timmermann (2004); (16) Timmermann et al. (2006); (17) O'Brien (2006); (18) Bröcker et al. (2009); (19) Carswell (1991); (20) Faryad et al. (2010); (21) Kotková (2007); (22) O'Brien (2008); (23) Marschall et al. (2003); (24) Schaltegger et al. (1996); (25) Will and Schmädicke (2001); (26) Konopasek et al. (2002); (27) Berger et al. (2010); (28) Lardeaux et al. (2001); (29) Demange (1985); (30) Mattauer (2004); (31) Schulz (2007); (32) Bosse et al. (2005); (33) Ballèvre et al. (2002); (34) Bosse et al. (2000); (35) Lucks et al. (2002); (36) Kotková et al. (2011); (37) Ballèvre et al. (2009); (38) Ibarguchi and Gironés (1985); (39) Santos Zalduegui et al. (1996); (40) Rodríguez et al. (2003); (41) Ordóñez Casado et al. (2001); (42) Barbero and Villaseca (2000); (44) Rubatto et al. (2010); (44) Medaris Jr. et al. (2003); (45) Langone et al. (2011); (46) Giacomini et al. (2005); (47) Kryza et al. (2011); (48) Schmädicke (1991); (49) Schmädicke (1994); (50) Nasdala and Massonne(2000). f The Erzgebirge is tectonostratigraphically above the Saxon Granulite Massif. ...
Article
Abstract The Variscides of Europe and N-Africa are the result of the convergence of the plates of Gondwana and Laurussia in the Paleozoic. This orogen is characterized by the juxtaposition of blocks of continental crust that are little affected by the Variscan orogeny. These low strain domains principally consist of Neoproterozoic/Cambrian Cadomian basement overlain by volcano-sedimentary successions of an extended peri-Gondwana shelf. These Cadomian blocks are separated by high strain zones containing the record of subduction-related processes. Traditionally the high strain zones are interpreted as sutures between one or more postulated lithospheric microplates sandwiched between the two major plates. Paleobio-geographic constraints in combination with geochemical and isotopic fingerprints of the protoliths, however, imply that the Variscides are the result of the exclusive interaction of the two plates of Gondwana and Laurussia. Here we explain the Variscan orogen in a two plate scenario, reasoning that the complexity of the Variscan orogen (multitude of high-grade metamorphic belts, compositional diversity of coeval magmatism, and arrangement of foreland basins) is the result of the distribution of crustal domains of contrasting rheological properties. Post-Cadomian rifting along the Cadomian–Avalonian belt, which culminated in the opening of the Rheic Ocean, resulted in vast coeval intracontinental extension and the formation of extended peri-Gondwana shelf areas, namely the Avalonian shelf and the Armorican Spur to the north and south of the evolving Rheic Ocean, respectively. Both shelf areas affected by heterogeneous extension consist of stable continental blocks separated by zones of thinner continental crust. During Variscan collisional tectonics the continental blocks behave as unsubductable crust, whereas the thinner continental crust was subductable and came to constitute the high strain domains of the orogen. The variable interplay between both crustal types in space and time is seen as the principal cause for the observed sequence of orogenic processes. The first collisional contact along the convergent Gondwana–Laurussia plate boundary occurred between Brittany and the Midland microcraton causing the early Devonian deformation along the Anglo-Brabant Fold Belt. This process is coeval with the initiation of continental subduction along the Armorican Spur of the Gondwana plate and the formation of back arc and transtensional basins to both sides of the Armorican Spur (e.g., Lizard, Rheno-Hercynian, Careón, Sleza) on the Laurussia plate. As further subduction along this collision zone is blocked, the plate boundary zone between the Gondwana and Laurentia plates is reorganized, leading to a flip of the subduction polarity and a subduction zone jump outboard of the already accreted blocks. The following Devonian–Early Carboniferous subduction accretion process is responsible for the juxtaposition of additional Cadomian blocks against Laurussia and a second suite of high-pressure rocks. The final collision between Gondwana and Laurussia is marked by an intracontinental subduction event affecting the entire internal zone of the orogen. Subduction stopped at 340 Ma and the following isothermal exhumation of the deeply subducted continental crust is primarily responsible for Late Variscan high-temperature metamorphism and cogenetic voluminous granitic magmatism. During this final transpressional stage the irregular shape of the Variscan orogen was established by the highly oblique motion of the decoupled lithospheric blocks (e.g. Iberia and Saxo-Thuringia). Rapid overfilling of synorogenic marine basins in the foreland and subsequent folding of these deposits along vast external fold and thrust belts finally shaped the Variscides, feigning a relatively simple architecture. In terms of plate tectonics, the model places the opening of the Paleotethys in the Devonian with a rotational axis of the spreading center just east of the Variscan orogen. The movement of Gondwana relative to Laurussia follows small circle paths about this axis from 370 to 300 Ma. As a consequence of the incomplete closure of the Rheic Ocean after the termination of the Variscan orogeny, Gondwana decoupled from the European Variscides along the dextral Gibraltar Fault Zone. The relative motion between Gondwana and Laurussia after 300 Ma is associated with a shift of the rotational axis to a position close to the Oslo Rift, and is related to the opening of the Neotethys and the evolution of the Central European Extensional Province. The Permian convergence of Gondwana and Laurussia led to the final Permian collisional tectonics along the Mauritanides/Alleghanides. The assembly of the “Wegenerian” Pangea is complete by the end of the Paleozoic.
... The major thermal event reflecting an isotopic homogenization during the Variscan orogeny is the LP/HT regional metamorphism at 319 + 36/−29 Ma in the temperature range between 680°C and 600°C (Wemmer and Ahrendt, 1993). The age supports the K/Ar cooling age of 312.5 ± 2.5 Ma when muscovite passed the 350°C temperature isograde (Kreuzer et al., 1989). It also corresponds to the Rb/Sr whole rock age of the older granites 319 ± 3 Ma, which intruded immediately north of the Wunsiedel Marble and whose magma had a minimum temperature of 660°C (Richter and Stettner, 1979). ...
Article
Metacarbonate rocks (marble, calcsilicate rock, skarn) hosting strata- and structurebound Fe-, As-Sb, Bi-, Ni-Co, Cu-Pb-Zn, U-, W- ore minerals as well as talc, clay minerals, barite and fluorite are widespread in the country rocks south of the collisional calc-alkaline felsic to intermediate intrusive rocks of the Fichtelgebirge Pluton, Germany. At its western rim, thrustbound and vein-type mineral assemblages with Au-As-Sb and F-Ba minerals associated with carbonate gangue minerals developed. Only recently, a calcite-hosted Sb mineralization was encountered in a deep-seated lineamentary fault zone cutting through metaultrabasic rocks along the northern edge of the granites. The same structure zone forms the loci of calcite-bearing U episyenite situated within this pluton. A composite geological, mineralogical and chemical (major and trace elements, REE, C- and O isotopes) study has been conducted to distinguish the heat and element source in subcrustal or deep-seated crustal areas and in the largely exposed granite complex. Only Sn-W skarn deposits are genetically related to the highly fractionated granitic members of the Variscan pluton. Pegmatite skarn has a strong subcrustal component as to the heat source and the provenance of rare elements and a moderate crustal one as far as the silicates are concerned. Deep-seated fault zones were active over a rather long period of time and acted as conduits venting magmas and hydrothermal fluids from the waning stages of the Variscan deformation through the Neogene. Calcsilicate and carbonate mineral assemblages are an efficacious tool to constrain the physico-chemical regime in this mineral province, covering the temperature range from 745 °C down to 53 °C in a medium to low pressure regime at strongly varying redox conditions. The major and trace elements, the REE variation, the Ce and Eu anomalies as well as carbon and oxygen isotopes of the various mineral assemblages enable us to identify the fluid sources and depict the element concentration processes, e.g., mixing of fluids, connate fluid and meteoric fluid interaction. From the economic point of view, the mineralizing system is most prospective for rare element deposits, talc, kaolinite-group minerals, iron, and uranium. Accumulations of fluorite and barite are subeconomic in mineral assemblages inside as well as outside the granites, while base metals and precious metals are only of mineralogical interest.
... The structural uppermost Allochthonous Unit of the Münchberg complex was affected by HP-LT metamorphism at 390 Ma and was thrusted over the Saxo-Thuringian unit at 340 Ma (Kreuzer et al., 1989;Klemd, 2010;Koglin et al., 2018; Table 1). The uppermost allochthonous unit represents an inverted metamorphic gradient of four contrasting nappes or series (from top to bottom): (i) the structurally uppermost "Hangend-Serie" comprises hornblende-bearing gneiss, amphibolite, leucocratic gneiss, and eclogite lenses that represent ca. ...
... The mid-to late-Devonian zircon ages in metagabbro of the MSU are consistent with metamorphic ages of oceanic rocks in the internal Variscan belt (Kreuzer et al., 1989;Stosch & Lugmair, 1990;Timmermann et al., 2004), but are not a good fit with the history of oceanic rocks in the external Variscan belt, such as the Lizard or Ślęża ophiolites. However, if we were to consider the early Cambrian zircon in T A B L E 3 Zircon saturation temperatures (T Zrn ) and saturation concentrations of Zr in melt at 1,000°C (C Zr ) for zircon-bearing MORB-type rocks from various parts of the Variscan belt calculated using the zircon solubility models of Watson and Harrison (1983) the MSU as inherited from the magma source, then the zircon dated at 384 ± 7 Ma could record gabbro formation synchronous with gabbro and dolerite intrusions into the exhuming Lizard peridotites (Cook et al., 2000), though such intrusions are unknown in the MSU serpentinites. ...
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Controversy over the plate tectonic affinity and evolution of the Saxon granulites in a two‐ or multi‐plate setting during inter‐ or intracontinental collision makes the Saxon Granulite Massif a key area for the understanding of the Paleozoic Variscan orogeny. The massif is a large dome structure in which tectonic slivers of metapelite and metaophiolite units occur along a shear zone separating a diapir‐like body of high‐pressure granulite below from low‐pressure metasedimentary rocks above. Each of the upper structural units records a different metamorphic evolution until its assembly with the exhuming granulite body. New age and petrologic data suggest that the metaophiolites developed from early Cambrian protoliths during high‐pressure amphibolite facies metamorphism in the mid to late Devonian and thermal overprinting by the exhuming hot granulite body in the early Carboniferous. A correlation of new Ar‐Ar biotite ages with published P‐T‐t data for the granulites implies that exhumation and cooling of the granulite body occurred at average rates of ~8 mm/year and ~80 °C/Ma, with a drop in exhumation rate from ~20 to ~2.5 mm/year and a slight rise in cooling rate between early and late stages of exhumation. A time lag of c. 2 Ma between cooling through the closure temperatures for argon diffusion in hornblende and biotite indicates a cooling rate of 90 °C/Ma when all units had assembled into the massif. A two‐plate model of the Variscan orogeny in which the above evolution is related to a short‐lived intra‐Gondwana subduction zone conflicts with the oceanic affinity of the metaophiolites and the timescale of c. 50 Ma for the metamorphism. Alternative models focusing on the internal Variscan belt assume distinctly different material paths through the lower or upper crust for strikingly similar granulite massifs. An earlier proposed model of bilateral subduction below the internal Variscan belt may solve this problem.
... The mid-to late-Devonian zircon ages in metagabbro of the MSU are consistent with metamorphic ages of oceanic rocks in the internal Variscan belt (Kreuzer et al., 1989;Stosch & Lugmair, 1990;Timmermann et al., 2004), but are not a good fit with the history of oceanic rocks in the external Variscan belt, such as the Lizard or Ślęża ophiolites. However, if we were to consider the early Cambrian zircon in T A B L E 3 Zircon saturation temperatures (T Zrn ) and saturation concentrations of Zr in melt at 1,000°C (C Zr ) for zircon-bearing MORB-type rocks from various parts of the Variscan belt calculated using the zircon solubility models of Watson and Harrison (1983) the MSU as inherited from the magma source, then the zircon dated at 384 ± 7 Ma could record gabbro formation synchronous with gabbro and dolerite intrusions into the exhuming Lizard peridotites (Cook et al., 2000), though such intrusions are unknown in the MSU serpentinites. ...
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Controversy over the plate tectonic affinity and evolution of the Saxon granulites in a two- or multi-plate setting during inter- or intracontinental collision makes the Saxon Granulite Massif a key area for the understanding of the Palaeozoic Variscan orogeny. The massif is a large dome structure in which tectonic slivers of metapelite and metaophiolite units occur along a shear zone separating a diapir-like body of high-Pgranulite below from low-Pmetasedimentary rocks above. Each of the upper structural units records a different metamorphic evolution until its assembly with the exhuming granulite body. New age and petrologic data suggest that the metaophiolites developed from early Cambrian protoliths during high-Pamphibolite facies metamorphism in the mid- to late-Devonian and thermal overprinting by the exhuming hot granulite body in the early Carboniferous. A correlation of new Ar-Ar biotite ages with publishedP-T-tdata for the granulites implies that exhumation and cooling of the granulite body occurred at average rates of similar to 8 mm/year and similar to 80 degrees C/Ma, with a drop in exhumation rate from similar to 20 to similar to 2.5 mm/year and a slight rise in cooling rate between early and late stages of exhumation. A time lag ofc. 2 Ma between cooling through the closure temperatures for argon diffusion in hornblende and biotite indicates a cooling rate of 90 degrees C/Ma when all units had assembled into the massif. A two-plate model of the Variscan orogeny in which the above evolution is related to a short-lived intra-Gondwana subduction zone conflicts with the oceanic affinity of the metaophiolites and the timescale ofc. 50 Ma for the metamorphism. Alternative models focusing on the internal Variscan belt assume distinctly different material paths through the lower or upper crust for strikingly similar granulite massifs. An earlier proposed model of bilateral subduction below the internal Variscan belt may solve this problem.
... This geometry is deduced from structural vergence and direction of migration of syntectonic sedimentation [Franke, 1992;Schafer et al., 1997]. Vari scan plate convergence between Moldanubian and Saxothuringian continental blocks is shown by the widespread 380 Ma age metamorphism found within the Bohemian Massif nappes, both within the Saxothu ringian and Moldanubian zones [Kreuzer et al., 1989]. Subduction of oceanic crust in all basins was probably accomplished during the Devonian, so that the tectonic development, at least from the Early Carboniferous onwards, can be taken to represent the collisional stage [Franke, 1992]. ...
... Dieser devonische Flysch ist ganz offenbar der suprakmstale Ausdruck der druckbetonten Metamorphose und anschließenden Heraushebung, die in der Münchberger Gneismasse, in der ZEV und in der Zone von Tepl-Taus ( Z n ) zu etwa der gleichen Zeit nachgewiesen ist. Die sehr enge zeitliche Nachbarschaft von Zirkon (U-Pb)-, Hornblende (K-Ar, Ar-Ar)-und Glimmer (Rb-Sr, K-Ar, &-&)-Alternfast innerhalb der Fehlergrenzendeutet auf eine rasche Heraushebung hin (siehe Zusammenstellungen und Diskussionen in FRANKE et al. in prep., HANSEN et al. 1989, KREUZER et al. 1989 Ergebnisse laufender Untersuchungen von detritischen Zirkonen aus den Erbendorfer Grauwacken sind mit der Vermutung vereinbar, daß altvariscisches Kristallin bereits i m Devon angehoben und abgetragen worden ist: Die Grauwacke enthält Zirkone mit einer ähnlichen U-Pb-Systematik wie die von TEUFEL (1988) beschriebenen aus Paragneisen der Zone von Erbendorf/Vohenstrauß (ZEV) (W.DÖRR, unveröff.). ...
... In summary, early Devonian metamorphism and magmatism (sometimes called 'Caledonian', but historically and collectively termed Eo-Variscan elsewhere in Hercynian Europe; e.g. Faure et al. 1997;Shelley & Bossière 2000) was confined in the northern Bohemian Massif to isolated high-grade metamorphic rocks in the Góry Sowie Block (GSB; Brueckner et al. 1996;O'Brien et al. 1997) and the Münchberg klippe (395-390 Ma; Kreuzer et al. 1989;Stosch & Lugmair 1990). It may record local tectonothermal and hence collisional activity between migrating platelets of the ATA, with subsequent exhumation. ...
... This Devonian thermal event is widespread in crystalline basement of the Saxothuringian Zone. In the Münchberger nappe, Ar-Ar and K-Ar ages on muscovite and hornblende of 372-390 Ma ( Kreuzer et al. 1989;Söllner et al. 1981) are common. In paragneiss of the Münchberger nappe, Koglin et al. (2018) recently discovered metamorphic zircons with an age at 390 ± 3 Ma. ...
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Detrital zircon age spectra of Ediacaran paragneiss from the Rheic suture between the Rhenohercynian Zone and Saxothuringian Zone suggest that they originated from different parts of peri-Gondwana. The paragneiss from the Northern Phyllite Belt displays an age spectrum of detrital zircons with a high amount of Neoproterozoic (82%) and Mesoproterozoic zircons (11%) typical for Amazonian provenance, whereas the spectrum from the metagreywacke of the Odenwald (Mid-German Crystalline Zone) shows a Mesoproterozoic age gap which is correlated with the West African Craton. The metagreywacke of the Odenwald contains 20% Paleoproterozoic and 32% Archean zircons, whereas the paragneiss of the Northern Phyllite Belt (Wartenstein Crystalline) contains only 6% Paleoproterozoic and no Archean zircons. The paleoposition of the basement of Northern Phyllite Belt was proximal to the Avalonian magmatic arc of the London–Brabant high. The Armorican metagreywacke of the Odenwald occupied a distal position to a Neoproterozoic magmatic arc, probably in a back-arc basin related to the West African Craton. Such a U–Pb age spectrum of detrital zircons together with a Mesoproterozoic age gap is typical for sediments of Armorica in Europe during the Ediacaran to Carboniferous. Neoproterozoic igneous rocks extruded at 566 ± 2 Ma forming a volcano-clastic sequence of the Cadomian magmatic arc which is the wall rock of the Silurian to Carboniferous plutons of the entire West Odenwald. This is the first occurrence of an extensive Cadomian crystalline basement in the Mid-German Crystalline Zone. Metagranite dykes crosscut the foliation of the Cadomian para- and orthogneiss at 542 ± 3 Ma. The deformation and migmatization of the Cadomian basement are bracketed between 566 and 542 Ma. A similar late Cadomian event is known from the Bohemian Massif and the Armorican Massif. Large Cadomian plutons with an age around 540 Ma, like that of the northern Odenwald, are common for Armorica. Silurian to Devonian granitoids (434 ± 4 Ma, 411 ± 5 Ma) are witness to an active margin along the northern boundary of Armorica. The Cadomian basement of the Odenwald together with the Palaeozoic granitoids is overprinted by a high-grade metamorphism at 384 ± 4 Ma (U–Pb on zircon) and cooled down below ca. 500 °C at 370 Ma (K–Ar ages of amphibole; U–Pb on titanite). Such a combination of late Cadomian and early Variscan ages could be correlated with the Münchberger Nappe, the Tepla–Barrandian Unit, Central Armorican Domain and the Massif Central.
... Below, the Rand Amphibolite and Phyllite-Prasinite units, formed around 400 Ma (Koglin et al. 2018), and metamorphosed at c. 365 Ma (Kreuzer et al. 1989), are probable equivalents of the Early Devonian ophiolites of the Middle Allochthon, as their features fit those of the Purrido and Moeche units, respectively. The structural succession of the Frankenberg klippe consists of a low-grade volcanosedimentary complex and the gneiss, amphibolite and prasinite units (Rötzler et al. 1999;Klemd 2010). ...
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The NW Iberian Allochthon and the Teplá-Barrandian and Moldanubian zones represent the internal parts of the Variscan belt in their respective domains. A correlation based on the lithological association, protolith ages, metamorphic evolution, detrital zircon age spectra and tectonic setting is attempted between the NW Iberian Massif and SE Bohemian Massif in order to check whether they could have formed part of the same allochthonous stack. The Galicia-Trás-os-Montes Zone of the Iberian Massif and the internal zones of the Bohemian Massif include from bottom to top a Parautochthon and Lower Allochthon representing the outer edge of the northern Gondwana margin, an oceanic Middle Allochthon with Cambro-Ordovician and Early Devonian ophiolites and an Upper Allochthon interpreted as a peri-Gondwanan terrane. Early Variscan, subduction-related high-pressure metamorphism characterizes many of the allochthonous units, with ages younging from the structurally upper to the lower units from 400–385 Ma to 370–360 Ma, respectively. High- and ultrahigh-pressure metamorphism occurred also in the Saxothuringian Autochthon at 360–340 Ma, but not in the NW Iberian Autochthon. The different behavior of the Autochthon in the Iberian and Bohemian massifs accounts for their distinct evolutions from 360 Ma onward. We conclude that the Upper Allochthon was a unique peri-Gondwanan terrane, whereas the Middle Allochthon represents units of the same peri-Gondwanan ocean, opened at the Cambro-Ordovician boundary, and having recorded localized renewed activity in the Silurian–Early Devonian. No other oceans separated the Lower Allochthon, Parautochthon and Autochthon.
... Here, the tectonometamorphic record indicates initial collision between Laurussia and Peri-Gondwana in Lower Devonian rocks at 400 Ma (e.g. Kreuzer et al. 1989;Schaltegger et al. 1996;Lardeaux et al. 2001;Nutman et al. 2001;Ordóñez Casado et al. 2001;Lucks et al. 2002;Kryza & Fanning, 2007;Bröcker et al. 2009;Berger et al. 2010), whereas continental crust of the East African-Arabian Zircon Province is not affected by collisional tectonics before the Carboniferous period, i.e. c. 50 Ma later (Dallmeyer et al. 1997;Giacomini, Bomparola & Ghezzo, 2005;Rubatto et al. 2010;Langone et al. 2011;Martínez Catalán et al. 2014). Hence, the West African Zircon Province can be regarded as the leading edge of Peri-Gondwana, i.e. the Armorican Spur (Kroner & Romer, 2013), during the collision of Gondwana and Laurussia. ...
... On the other hand, rocks from the Fichtelgebirge crystalline complex underwent low-pressure regional metamorphism in the time interval 330-320 Ma (Okrusch et al., 1990). Kreuzer et al. (1989) reported K-Ar ages of 316±3 Ma obtained on muscovite in gneiss and schist, which were sampled ~2.5 km northeast of the town of Selb (Fig. 1c). In addition, these authors applied K-Ar dating of amphibole from schistose amphibolites of the Fichtelgebirge crystalline complex and revealed ages of 332 and 299 Ma. ...
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We propose a mechanical model of deformation of the entire lithosphere of the Bohemian Massif (BM), whose core is formed by an asymmetric block of the Teplá-Barrandian (TB) unit in between the Saxothuringian (ST) and Moldanubian (MD) units. For the modelling, we have re-processed P-wave travel times recorded during the last two decades at dense networks of seismic stations installed in the BM during several passive seismic experiments. We also use previous results of anisotropic studies based on splitting of teleseismic shear waves. This allows us to refine estimates of the lithosphere thickness and delimit deep margins of the individual mantle lithosphere domains. The domains are rigid enough to preserve pre-orogenic olivine fabrics differently oriented in each of the units. Shapes and dips of the mantle boundaries, representing major zones of weakness inherited from the Variscan amalgamation of independent microplates, indicate that north-westward subductions beneath the TB unit dominated tectonic development of the core of the BM. Two mantle lithosphere domains with different fabric orientations, separated by a WSW-ENE striking shear zone, underlie the TB crust. The NW domain is the TB mantle lithosphere, while the SE domain is the MD mantle lithosphere thrust under the TB crust. Lithosphere of the north-western TB domain, compressed between early Variscan subductions of the ST continental lithosphere from the northwest and the MD continental lithosphere from the southeast, was pushed south-westward by about 50 km. Though the crust of the south-westerly TB promontory is commonly attributed to the MD unit, apparently it preserves the TB mantle lithosphere. The shifted TB lithosphere provides compelling evidence in support of older views suggesting that the Zone Erbendorf-Vohenstrauss (ZEV) originally belonged to the tilted western rim of the TB unit. During the final phase of the assemblage of the BM, the rigid TB lithosphere was disrupted by the southward pushing ST lithosphere along the newly formed NW-SE striking Jáchymov Fault Zone (JFZ). This lithosphere-scale process most likely changed the tectonic regime, released subduction-related forces and started the gravity-dominated tectonics.
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The post-Carboniferous crustal evolution of the German Continental Deep Drilling Program (KTB) area, as summarized in this paper, could not be predicted from surface observations: deep drilling was essential for its revelation. The most conspicuous and unexpected feature discovered in the drill hole is the absence of marked gradients with respect to the pre-Carboniferous record. There are no depth-related differences in K-Ar cooling ages of hornblende and white mica, in petrology or in lithology. All metamorphic rocks encountered, both at the surface as well as in the drill hole down to 9100 m depth, were below 300øC from the Carboniferous onward. The late to post-Carboniferous deformation is essentially confined to several fault zones. A major fault zone encountered in the drill hole at 7000 m depth is linked by a prominent seismic reflector to the Franconian Lineament, the surface boundary between Variscan basement and Mesozoic cover. This fault zone probably formed in the late Paleozoic and reactivated as a reverse fault in the Mesozoic. Two important episodes of NE-SW directed shortening by movements along reverse faults took place in the early Triassic and in the late Cretaceous, as indicated by the distribution of apatite and titanite fission-track ages, the sericite K-Ar ages of fault rocks, and the sedimentary record in the adjacent basins. Upper crustal slices were detached at a specific level, corresponding to the approximate position of the brittle-ductile transition in post-Variscan times, and form an antiformal stack that was penetrated by the KTB throughout its entire depth range.
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As laid out in Chapters V.B.1 and V.B.2, the parautochthonous Thuringian fades of the Saxothuringian Belt has been overthrust from the SE by nappes, which have survived in the core of the Vogtland Synform. These are the tectonic klippen of Münchberg, Wildenfels, and Frankenberg (in order from W to E; see Fig. 1). The klippen represent, in fact, erosional remnants of one or several nappe piles, which were originally more extensive, and possibly laterally continuous with each other. The tectonic sequence in each of these klippen is characterized by inversion of the stratigraphy and of the metamorphic grades. The lower nappes comprise (in order from bottom to top): proximal Early Carboniferous flysch, Silurian/Devonian bedded chert, and a volcanosedimentary sequence of largely Ordovician age. These very-low-grade, fossiliferous sequences are overlain by a number of metamorphic thrust sheets. This chapter describes the lithology, tectonic sequence, and internal structure of the metamorphic nappes in the klippen, and of their probable equivalents at the northwestern margin of the Moldanubian Region, from which they are derived. We set out from the Münchberg klippe, which is the largest, most differentiated and best studied example of its kind, and then briefly discuss the closely related units. Details on the metamorphic evolution are available in the contribution by Blümel (Chap. V.C.2)
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The non-cylindrical character of the Variscan Belt is established via a description of its most salient geological characteristics and correlations among the main and relatively minor massifs from Bohemia to Morocco on the basis of a bibliographical synthesis. Using the firmly established tectonostratigraphic domains, the continuity of Variscan zones is discussed, as well as the western termination of the one that occupies most of the central part of the belt. This zone is characterized by its allochthony, and breaks the continuity of the zonation, that is, the cylindrism of the belt. A proposal is made to call this zone the Mid-Variscan Allochthon and its wedge shape in map view is explained performing a step by step restoration of late Variscan deformation. Once the geometry of the belt is interpreted by a succession of regionally significant deformation events, a kinematic reconstruction is proposed. It is based on recent developments on the knowledge of Paleozoic plate tectonics and intended to show that the deformation model is compatible with current paleogeographical developments.
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Recent investigations and geological mapping in the W surroundings of the Marianske Lazne metaophiolite Complex (MLC) led to a redefinition of the boundary between the Tepla-Domazlice (ZTT) area and Saxothuringicum. The metabasites cropping out W of the Vlci hrbet ridge serpentinite body till now considered to be a part of the MLC, do not belong to this MP unit with relics of HP eclogites. The metabasites are newly interpreted as being part of the Kladska unit. The term Kladska unit is redefined here. The Kladska unit represents a suite of low- to high-grade metasediments with intercalations of cherts and weakly metamorphosed calc-alkaline to alkaline basalts, trachybasalt and trachyandesites with preserved relics of primary magmatic textures. During the LP-HT late orogenic phase (~330-320Ma) MP rocks of the MLC, containing HP relics, were thrust over the paraautochthonous rocks of the Kladska unit on a minimal distance of 6km. The thrust plane separating the MLC and the Kladska unit is thought to represent a major terrane boundary between the Saxothuringicum and MLC. -from Author
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Detrital zircons separated from paragneisses of the northern Böllstein Odenwald (Mid-German Crystalline Zone, Variscides) yielded Cambrian to Upper Devonian U–Pb ages. The age of the youngest detrital zircon population (371 ± 3 Ma) and the Lower Carboniferous metamorphic overprint indicate an Upper Devonian depositional age of the paragneiss protolith. The age spectra of detrital zircons suggest the latter to be derived from (1) Ordovician igneous rocks of the Saxothuringian Zone, (2) a late Cadomian magmatic arc (Teplá-Barrandian Unit) and (3) a Silurian-Devonian magmatic arc. Cadomian igneous activity is also documented by Cambrian zircon cores in Lower to Middle Devonian detrital zircons. Meso- and Paleoproterozoic detrital zircons, which are typical for the Old Red Continent and the Rhenohercynian Zone, are entirely lacking. The restricted Palaeozoic detrital zircon age spectrum is attributed to a Silurian-Devonian intra arc or trench setting. Both the lack of Mesoproterozoic detrital zircons and the striking similarity of the U–Pb ages of the detrital zircon obtained from the Böllstein Odenwald with U–Pb ages from crystalline rocks of the Saxothuringian basement, rules out that the Böllstein Odenwald is forming a tectonic window (Rhenohercynian lower plate) inside the Mid-German Crystalline Zone (Saxothuringian upper plate).
Chapter
The most detailed data referring to metamorphism in the Bohemicum comes from the Teplá-Barrandian (TB) region to the W and from the Orlické hory Mts. (Nové Město unit) to the NE. Knowledge of other outcroppings along its E and SE border, the Železné hory Hills, the Policka, Letovice, and Zábřeh regions, is unsystematic. Only boreholes and isolated outcrops in small uplifted blocks provide information on most of the Bohemicum covered by Permo-Carboniferous and Cretaceous sediments.
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A Rb - Sr white mica - whole-rock age of 327 ± 6 Ma for a muscovite - paragonite, chlorite schist in the eastern Fichtelgebirge, near Kraslice, is recorded and interpreted as the time of the D2 - S2 event at the peak of Barrovian-type dynamothermal metamorphism. A corresponding age of 327 ± 5 Ma, obtained using the same isotopic system in another mica schist from the same district, is also recorded for a muscovite porphyroblast - whole-rock. The age is interpreted as the time of cooling through the closure temperature of muscovite following the overgrowth of randomly-disposed porphyroblasts and of paragonite-out reactions resulting from a low-pressure metamorphic overprint that had reset the Rb - Sr isotopic systems relatively late in the deformational sequence. With the formation of three sets of thrusts that were major contributors to the tectonic stacking of the disparate crystalline units in the western part of the Bohemian Massif and of a number of sets of folds being between the two ca. 330-325 Ma metamorphic events in the deformational sequence, the timing of the Hercynian orogenic episode in the southern Fichtelgebirge tectonic domain is deduced to have straddled the Viséan -Namurian boundary. The new data together with the ca. 320 Ma age of emplacement of the earliest of the granites in the Fichtelgebirge indicate a relatively short time span for this late Early Carboniferous episode during which (1) compressional tectonism, expressed by the development of intrafolial folds and schistosity during medium-pressure dynamothermal metamorphism, and then by sets of thrusts and upright folds, was followed by (2) a low-pressure metamorphic overprint and then by (3) further weak compressional (± transpressional) tectonism with the formation of upright folds and then a set of thrusts.
Chapter
By the time the transition zone between the Saxothuringian and the Moldanubian units in northeastern Bavaria was selected as a possible location for the German continental deep-drilling project (KTB), great differences with respect to the interpretation of the geological evolution of the area were obvious, differences which had important consequences for the geochronological evolution of this area. Stettner (1975,1979) assumed that the high-grade Moldanubian gneisses were metamorphosed during Cadomian time, whereas the Saxothuringian sediments of Early Paleozoic age were supposed to have been subjected to an Early Hercynian reworking. In contrast, Schreyer (1966) proposed that the Saxothuringian and the Moldanubian units had suffered the same low-pressure metamorphism, which would mean that at least the last metamorphic overprinting of both units should be of Hercynian age. This was confirmed by structural studies, which showed a continuous structural development from the Moldanubian into the Saxothuringian (Stein 1987). The structural model of the transition zone between Moldanubian and Saxothuringian is also in agreement with the petrological studies of Wagener-Lohse and Blümel (1984) and Blümel (this Vol.).
Chapter
During the Variscan orogenesis, most of the complexes forming constituents of the MGCR, were subjected to regional metamorphism under conditions generally ranging from the lower to the upper amphibolite facies. Except for the Ruhla crystalline complex, no consistent isograd pattern can be mapped in these metamorphic complexes, indicating that the present erosion surfaces are virtually parallel to the metamorphic isograd surfaces. The constituents of the MGCR form individual blocks which experienced different peak metamorphic conditions (Fig. 1), underwent different P-T paths (Fig. 2) and were uplifted to different levels of erosion at different times (e. g., Ahrendt 1990; Okrusch 1990; Nasir et al. 1991; Willner et al. 1991; Krohe 1991; Flöttmann and Oncken 1992).
Chapter
The Moldanubian Zone (MZ) was considered for many decades as an old nucleus (median mass) of the Bohemian Massif consolidated during the Cadomian or older orogenies, and surrounded by mobile Variscan belts (Stille 1951; Máška and Zoubek 1961; Zoubek et al. 1988; Chaloupský 1989). However, numrous investigations carried out in different parts of the MZ in Czechoslovakia, Austria, and Germany over the past 20 years have confirmed the early suggestions by Suess (1912, 1926), Kossmat (1927), and Kober (1938), who first interpreted the structural evolution of the MZ in terms of Variscan horizontal tectonics. There is a growing body of evidence indicating that the Moldanubian segment of the Bohemian Massif represents a mosaic of tectonic units with a distinct tectonometamorphic history which were finally assembled in the course of the Upper Paleozoic collision of Laurasia and Gondwana.
Chapter
Within or at the periphery of the Saxothuringian Basin several isolated basement areas of medium or even high grades are found. These are the Münchberg Mass, the “Zwischengebirge” of Wildenfels and of Frankenberg, the Zone von Erbendorf Vohenstrauß and the Sächsische Granulitgebirge including its Schiefermantel (Fig. 1). The Erzgebirge Zone is incorporated into this chapter here since it may also be allochtonous. The last main metamorphism of most of the allochthonous units is of the MP type except for the Sächsische Granulitgebirge and its Schiefermantel, and some peripheral schists of the Erzgebirge Zone, which show an anomalously high geotherm.
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Coronitic metagabbros occur as small isolated bodies along the contact between the Mariánské Lázně and the Teplá Crystalline complexes in the northwestern part of the Teplá-Barrandian Unit in the Bohemian Massif. Metagabbros show variable metamorphic and textural characteristics with respect to their magmatic mineral assemblage and degree of metamorphism. The aim of this study has been to characterize the mineralogical, chemical, and microstructural changes related to metamorphism in selected samples. Magmatic mineral assemblages in the metagabbros represented by plagioclase, orthopyroxene, clinopyroxene, amphibole, biotite, ilmenite and occasionally involving olivine, spinel or quartz are generally well preserved. Metamorphism is mainly reflected by the formation of single or multiple coronas at the contact of plagioclase with the other primary minerals. The coronas typically consist of amphibole, garnet and orthopyroxene. The progressive breakdown of magmatic plagioclase is reflected by the formation of a mixture of An40 and An90 plagioclase associated with spinel, corundum and locally also kyanite. The calculated P-T conditions show an increase in metamorphic grade towards the structural footwall, i.e. from the east-southeast (~600 ± 50 °C; 10 ± 1.5 kbar) to the west-northwest (~700 ± 50 °C; 13.5 ± 1.5 kbar), which corresponds to the previously reported Variscan metamorphic field gradient in this area. Since there is no gap in P-T conditions between metagabbros included in MLC and TCC and showing similar age and geochemical signature, it is concluded that both complexes were brought together before the gabbro intrusion at ~500 Ma. In addition, the maximum pressure of ~14 kbar estimated for the metamorphism of the gabbro occurring in the eclogite-bearing Mariánské Lázně Complex suggests that the eclogite-facies metamorphism might have been pre-Variscan. The chemistry of the studied metagabbros corresponds to subalkaline basalts with traceelement signatures characteristic of E-MORB, which is consistent with an interpretation that the intrusion of these rocks was related to an intracontinental rifting of the Teplá-Barrandian Unit during Late Cambrian and was not connected to any subduction processes.
Chapter
Pegmatitic rocks are not randomly distributed across the Variscan/Hercynian basement in Central Europe. The evolution of pegmatites s.l. in the course of a complex orogeny of Meso-Europe took rather long, from the Devonian (419 Ma) through the Permian (252 Ma). In terms of structural geology and geodynamics, pegmatitic deposits primarily occur in ensialic Variscan-type orogens (calc-alkaline) with a thickened crust and a preponderance of thrusting and nappe stacking. In Rift-type settings (alkaline) a strong subcrustal impact is evident and as reactivated/reworked pseudopegmatites in Alpine-type orogens (calc-alkaline) these deposits developed during the initial stages when the crustal section was still rather thick. Both types pertain to the marginal ensimatic settings. They left their hallmarks to some extent also within the Central European Variscides and at its southern edge in the Alpine-Carpathian Orogen. The geodynamic units subjected to very-low-grade- to low-grade stage metamorphism at the margin of the Central European Variscides are barren with regard to pegmatites and aplites. Pegmatoids with minor B-(Li)-P-REE-U-Be mineralization occur along a suture zone extending across the present-day continents. It resulted from the late Variscan closure of the Rheic Ocean between Gondwana and Laurussia with remnants of an arc-related plutonism. Within allochthonous metamorphic complexes and nappes barren feldspar-quartz pegmatoids plus metapegmatites developed. Further south another part of this former coherent nappe also contains a small Be-Nb-P mineralization. Within the Subfluence zone, marked by continent-continent collision and thickening of the crust pegmatite, granite- pegmatite (miarolitic), pegmatite-aplite and pegmatoid abundant in B, Be, F, Li, Sn, U, P and As are encountered. Heading further to the core zone of the Variscan orogen, strong diapthoresis and shearing in the contact zone between the Saxothuringian and Moldanubian zones sensu lato favored the emplacement of pegmatite and aplite enriched in B, P, Be, Nb, As, Zr and F. High grade metamorphic rocks in an autochthonous position with a protolith mainly of Proterozoic age exist in the core zone. At the margin they are overthrusted onto adjacent geodynamic units and penetrated by multiple intrusions. The Hagendorf-Pleystein Pegmatite Province is located near the root zone for the nappe complexes thrusted onto the north-western geodynamic realms. Pegmatites and aplites with minor pegmatoids of the Hagendorf-Pleystein Pegmatite Province show the most varied concentration of rare elements in pegmatitic and aplitic rocks in this crustal section (B-P-REE-Nb/Ta-Li-Sc-Zn-Be). In some parts in core zone pegmatites can also be observed associated with skarns. Variscan lithologies were incorporated into the Alpine orogen and reactivated during the Alpine orogeny at the southern edge of the Meso-Europe. They contain granitic pegmatites, meta-pegmatites, pegmatoids and pseudo-pegmatites (B-Be-P-Nb-U-F-As-Li-Sn-REE-U). By quality this element assemblage is not very much different from that of the neighboring Variscan parent rocks. The suite of pegmatitic and aplitic mineral deposits is associated with mineral deposits of non-pegmatitic origin. They include thrustbound deposits (Au-As-Sb-(Hg)-Fe-Cu-Pb-Zn), plutonic/granite-related deposits (Sn-W-Mo-Pb-Ag-Zn-(In)-Cu-U), and unconformity-related (U-Pb-Zn-F-Ba). While the deposits can at least in parts structurally and compositionally related to the various types of pegmatites and aplites, stratabound deposits are mainly marker deposits for geodynamic units prone to aplitic or pegmatitic rocks in an ensialic orogen (SMS > > VM FeS-Cu-Zn, SEDEX Fe deposits, black-shale –hosted U-Cu-Mo-Sb-Zn-REE (low-grade-large-tonnage) and graphite). As an exception from this rule, the two last-mentioned mineralization with organic compounds can be considered (see geophysical surveys).
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The results of 26 Rb/Sr whole-rock analyses on two types of granite and on dioritic dykes in the Regensburger Wald, NE Bavaria, are tabulated. Intrusion ages, calculated from isochrons, are 349 + or - 11 m.y. for Kristallgranite I, 335 + or - 12 m.y. for the diorites and 319 + or - 7 m.y. for Kristallgranite II, showing that all these intrusives were emplaced at the beginning of the Variscan orogeny. The age difference of 30 + or - 18 m.y. between the two granites is statistically significant and in accordance with field observations. Sr-isotope ratios are 0.7076 + or - 0.0005 for Kristallgranite I, 0.7076 + or - 0.0003 for the diorites and 0.7116 + or - 0.0005 for Kristallgranite II; all three rock types are considered to have been derived from a single reservoir in the Moldanubicum lower crust. -R.A.H.
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To the east of the small town of Tirschenreuth there is an exposure of Upper Proterozoic metasediments with calc-silicates, carbonates, and acid volcanic rocks (leptynitic gneisses). They are characterized by marked enrichment of U, REE, Sn, W, Zr, Cu and Fe. Lithostratigraphic, petrological and geochemical investigations show that these element concentrations are in part stratiform. Typical members of the metamorphic assemblage, however, include granitic lenses and layers of monzonite, granodiorite and syenogranite composition and contain significant amounts of allanite, monazite and zircon. Hydrothermal processes, perhaps associated with Hercynian plutonic activity, produced severe alteration of the metamorphic rocks, giving chloritization, sericitization and silicification and leading to concentration of U and to a lesser extent W, Sn, Li, Be, F, Cs, Fe, Cu and As.-R.A.H.
Article
This NE Bavarian massif adjoins the larger Falkenberg massif to the NW. It consists of microcline granites and is assigned to the older post-Sudetic granite group (approx 300-330 m.y.). The pluton is made up of eccentric shells with the Friedenfels granite (GSF) in the deepest part, overlain by the Steinwald granite (GS) and its roof facies (GSD). The final member is an aplite dyke-like granite (GSA) intruded into the central part of the massif. There is a transition zone in the SE between the Friedenfels granite and the Falkenberg porphyry granite. The various Steinwald granites are monzogranites and can be subdivided on texture, mineral content and geochemical differentiation. There are two mineralization trends: 1) associated with the granite crystallization; and 2) associated with earlier post-granitic faulting and alteration. It is possible to assign the rocks to 'tin-' or 'tungsten-bearing' granites. This differentiation reached a more advanced stage than that of the younger granite group of the Fichtel Mts. The highest Li, F, Rb, Nb, Sn and Cs contents of the granites from E Bavaria were found in the GSD. The post-granitic hydrothermal mineralization along faults is characterized by elevated As and Au contents, while isolated As (and Sb) mineralization is found in the serpentinite-hornfels to the S. Galena, sphalerite, pyrite and chalcopyrite form a transition to the Erbendorf veins and there is evidence for the mobilization of tungsten in analogous post-granitic structures.-R.E.S.
Article
Rb/Sr measurements on 10 anatectic paragneisses from two localities in the Regensburger Wald yield two parallel regression lines corresponding with a Caledonian age (436 + or - 15, 438 + or - 17 m.y.; initial 87Sr/86Sr ratio 0.7110). Five regions of approx 100 m to several km in diameter in the Moldanubicum of eastern Bavaria in each case yield Variscan mineral and Caledonian whole-rock ages; they give an isochron with an age of 563 + or - 29 m.y. with an 87Sr/86Sr intercept of 0.7048 + or - 0.0014, which perhaps reflects the age of sedimentation or of a pre-anatectic metamorphic event. -R.A.H.
Article
Some K/Ar ages are presented for a suite of minerals for which Rb/Sr ages had already been determined. About 50% of the biotites contain excess Ar and show specific gas-release patterns in stepwise-heating experiments. Undisturbed ages document a cooling of the Munchberg gneiss, NE Bavaria, from 50 to 300oC in the interval 400-350 m.y. ago. The Rb-Sr isochron for two whole-rocks and their respective clinopyroxenes gives a formation age of 449 + or - 37 m.y. for the WeiSS enstein and Martinsreuth eclogites; the 87Sr/86Sr initial ratio is 0.7039 + or - 0.0001. Sm-Nd analyses give epsilon0 Nd values of +11.2 + or - 0.6 (WeiSS enstein) and +5.0 + or - 0.6 (Martinsreuth), indicating a typical MORB precursor for the WeiSS enstein eclogite, whereas that of Martinsreuth is more probably derived from island arc or oceanic basalts. A medium-P metamorphism affected the lower sequence of gneisses at approx 435 m.y. As the system cooled down, a medium-T deformation took place approx 370 m.y. ago.-R.A.H.
Article
Zusammenfassung K/Ar-Datierungen an Glimmern des Fichtelgebirges und der nördlichen Oberpfalz überdecken das Intervall von 330 Ma bis weniger als 300 Ma. Zusammen mit Rb/Sr-Gesamtgesteinsdatierungen an post-deformativen Graniten lassen sich vier variskische Ereignisse herausarbeiten:1) Regionalmetamorphose vor rund 330 Ma, 2) Die Intrusion der älteren post-deformativen Granite vor 320 Ma, 3) die Intrusion der jüngeren Granite vor rund 300 Ma, 4) lokale Einflüsse auf Hellglimmer noch nach 290 Ma, auf Klüften sogar bis < 150 Ma. Die verschiedenen Uran-Schwarzerztypen liefern stark diskordänte U/Pb Daten. Nach der Diskordia-Methode hat die ältere Pechblendegeneration ein oberes Schnittpunktalter von 336±17 Ma, die jüngere Generation eines von 298±4 Ma. Brannerit konnte mit 288±78 Ma nur unscharf datiert werden.Die unteren Schnittpunktalter der Pechblenden sind 0–7 Ma. Dieses junge Ereignis wurde mit Torbernitproben genauer untersucht. In Kombination mit-spektrometrischen Untersuchungen ergab sich ein sehr junges Alter von (131,5±4,5)×103 a. Pyrit und Kupferkies konnten nicht datiert werden, da ihre207Pb/206Pb-Verhältnisse z. T. erheblich unter dem Rezentwert von 0,046 liegen.
Article
Zusammenfassung Ausgehend von den Ergebnissen der geologischen Kartierung werden die Mineralparagenesen der verschiedenen metamorphen Gesteine des Gebietes in AKF-Diagrammen dargestellt und auf ihre gegenseitigen Reaktionsbeziehungen hin untersucht. Es folgt, daß im Osten ein kontinuierlicher metamorpher Übergang vorliegt, angefangen von den altpaläozoischen Glimmerschiefern des Saxothurmgikums, charakterisiert durch Biotit-Muscovit-Andalusit, über eine Serie von Biotit-Sillimanit-Gneisen mit Granat oder Kalifeldspat hinweg bis in die hochmetamorphen Gneise und Migmatite des Moldanubikums mit Cordierit-Sillimanit-Kalifeldspat. Hieraus ergibt sich ein wahrscheinlich frühvaristisches Alter für die gemeinsame Metamorphose. Besonders das Moldanubikum ist im Westen über weite Bereiche von einer späteren Diaphthorese betroffen worden, welche Mineralparagenesen wie Chlorit-Biotit-Muscovit und Chlorit-phengitischer Hellglimmer erzeugt, also eine noch niedriger temperierte Mineralfazies als die der benachbarten saxothuringischen Glimmerschiefer. Auch diese Diaphthorese ist noch varistisch, denn erst nach ihr kommt es zur Intrusion der wohl sudetischen Magmatite.
Article
Rb/Sr biotite ages of Moldanubian gneisses and granites fall in the range of 330–345 million years (m.y.). The biotite age of a pre-Moldanubian garnetkyanite gneiss was found to be 440 m.y., that of a metagranodiorite of the Münchberg Mass 385 m.y. Zircons from a Moldanubian gneiss yielded nearly concordant ages of approximately 450 m.y. These results indicate that both the Münchberg Mass and large parts of the Moldanubicum have undergone considerable heating during early Variscan (=early Hercynian) time, probably in the course of regional metamorphism. The relations of these strongly metamorphosed complexes with the neighboring less affected sediments of the Saxothuringicum (in the case of the Münchberg Mass) and the Barrandium (in the case of the Moldanubicum) are presumed to be caused by different depths of metamorphism in Variscan time. Higher ages seem to be related at least partly to Caledonian intrusions.
Article
The petrography, mineral chemistry and petrogenesis of a sample from the Weissenstein eclogite, Bavaria, Germany, has been investigated. The total mineral assemblage comprises garnet, clinopyroxeneI+II, quartz, amphiboleI+II, rutile, phengite, epidote/allanite, plagioclase, biotite, apatite, pumpellyite, titanite (sphene), zircon, alkali feldspar and calcite. Textural observations combined with geothermobarometry (Fe/Mg distribution between clinopyroxene/garnet and phengite/garnet; jadeite-content of omphacite, Si-content of phengite, and An-content of plagioclase) provide indications of two different stages in the metamorphic evolution of the rock. The main phengitequartz-eclogite mineral equilibration occurred at minimum P=13–17kbar, minimum T=62050 C; the retrograde symplectite stage (clinopyroxeneII, amphiboleII, biotite, plagioclase) occurred at P total between 12 and 8.5 kbar.Reactions of the symplectite stage are:(1) phengite (core) + Na2Oaq + CaOaq=phengite (rim) + biotite + plagioclase + K2Oaq + H2O (2) phengite (core) + clinopyroxeneI + Na2Oaq=phengite (rim + biotite + plagioclase + amphiboleII + SiO2 + K2Oaq + CaOaq + H2O (3) clinopyroxeneI + SiO2 + K2Oaq + H2O=clinopyroxeneII + plagioclase+amphiboleII + Na2Oaq + CaOaq The phengite decomposition produces H2O, whereas the clinopyroxene decomposition consumes H2O.The estimated P-T-conditions for the Weissenstein eclogite are in the same order of magnitude as those for other eclogite bodies from the Alps and Caledonides believed to be related to subduction processes.
Article
Bereits vor der Intrusion des Leuchtenberger Granits waren seine Rahmen-gesteine unter den Bedingungen der Amphibolit-Fazies regionalmetamorph eingeformt worden, wobei sich folgende Paragenesen bildeten: Muscovit + Biotit + Granat ± Sillimanit ± Staurolith (+ Quarz + Plagioklas) Muscovit + Biotit ± Kalifeldspat (+ Quarz + Plagioklas). Die Kontaktmetamorphose führt in den äußeren Bereichen der Aureole zur Paragenese Muscovit + Andalusit + Cordierit + Biotit (+ Quarz + Plagioklas), die der Hornblende-Hornfels-Fazies entspricht. In der inneren Kontaktzone werden die p-t-Bedingungen einer höhergradierten Hornfelsfazies erreicht, die sich in der Paragenese ± Kalifeldspat + Sillimanit + Cordierit ± Almandin + Biotit (+ Quarz + Plagioklas) dokumentiert. Die zonale Anordnung der Mineral-Paragenesen im Kontakthof läßt sich durch quantitative Verbreitungskarten anschaulich machen (150 Modalanalysen aus 59 Fundpunkten). Phasenbeziehungen und Mineralreaktionen werden anhand von AKF- und AFM-Diagrammen diskutiert, für deren Aufstellung 19 Mineralanalysen neu ausgeführt wurden. Durch den Vergleich mit derzeit verfügbaren experimentellen Unterlagen lassen sich die p-t-Bedingungen im Steinacher Kontakthof abschätzen. Danach ist ein Druckbereich von 1,5–3 kbar am wahrscheinlichsten. Mit der Bildung der höchst-gradierten Hornfelse waren 550° C sicher überschritten, während nach dem Jaeger-Modell 700° C als alleroberste Temperaturgrenze anzusehen ist. In der innersten Kontaktzone muß man mit geringen O2-Partialdrucken rechnen.
Article
Rb-Sr isotopic analyses of whole-rocks and biotite and U-Th-Pb analyses of zircon and monazite reveal regional metamorphic events for the Ordovician (Caledonian metamorphism) and the Carboniferous (Variscan=Hercynian orogeny), both accompanied by anatexis. The extent of the Caledonian and Variscan anatexis, however, cannot be evaluated, so far, because the field petrographic criteria are not sufficient to distinguish clearly between early and late Paleozoic anatexites. Evidence for a Precambrian metamorphism has not been found. Rb-Sr whole-rock isochrons obtained on leucosomes and melanosomes of partially molten paragneisses are interpreted as a minimum age of the second, early Variscan anatexis. The alternative explanation of the isochrons as a result of local Sr isotopic redistribution without a melt involved is considered less likely. Concordant and nearly concordant zircon ages (318–335 m.y.) of a coarse-grained granite and of diatexites are regarded as evidence for an intensive early Variscan granitization and palingenesis. Concordant zircon ages of diorite dykes, crosscutting the anatexites, establish a lower time limit of 309–312 m.y. for the Variscan anatexis. Rb-Sr ages of biotite (310-290 m.y.) indicate the end of the Variscan metamorphism. Estimates of the time of sedimentation or diagenesis based on Rb-Sr whole-rock analyses for some metasediment series in the north of the area yield maximum ages of 550 m.y., provided that Rb and Sr migration did not exceed substantially the extent of the outcrops (30–500 m) between the time of diagenesis and the Ordovician metamorphism. Otherwise, an upper limit of 2000–2300 m.y., which is the primary age of detrital zircon populations, can be established. Zircon populations of paragneisses and their anatectic derivatives were separated into size and shape fractions. From morphologic studies and U-Pb isotopic analyses, they were found to be composites of young concordant (318–325 m.y.) and old, highly discordant zircon components, with more than fifty per cent of young crystals in some anatexites. The apparent ages of the composites are 320–750 m.y. The U concentrations of the newly formed crystals can be higher, equal, or lower than those of the inherited zircon component. Some peculiarities in the concordia plot of the zircon data of paragneisses and migmatites (curved pattern; inversion of the generally observed systematics with respect to U concentration, grain size, degree of discordance) are interpreted as the result of polyepisodic disturbances of the inherited crystals in connection with new zircon growth. In the concordia diagram, the data points of the individual zircon grains containing inherited components appear to plot in band or wedgelike areas, and not on lines as the patterns of size fractions of the same zircon populations could pretend. Consequently, ages obtained by extrapolation of the regression curves to the concordia are not necessarily meaningful and require verification by other methods.
Article
Sanidine ages of various coal tonstein or tuff beds from six Central European Upper Carboniferous deposits have been determined using the 40Ar/39Ar stepwise heating method. All the sanidine samples show 40Ar/39Ar release spectra with well-defined plateaus. The measured ages are interpreted as the sedimentation ages of the coal tonsteins and tuffs. The results of these age determinations relate to the Carboniferous time scale and the authors thus suggest new age values for the Upper Carboniferous stage boundaries, which are ∼ 5–10 Ma higher than those proposed previously: base of Namurian: 326 Ma, base of Westphalian: 315 Ma, base of Stephanian: 306 Ma, base of Autunian: 300 Ma.RésuméDes âges sur sanidine de divers niveaux de tuffs ou de tonsteins charbonneux, échantillonnés dans des dépôts du Carbonifère supérieur d'Europe Centrale, ont été déterminés en utilisant la technique de chauffage par étape 40Ar/39Ar. Tous les échantillons de sanidine montrent des spectres de dégazage 40Ar/39Ar avec un plateau bien défini. Les âges calculés sont interprêtés comme des âges de sédimentation des tuffs et tonsteins. Les résultats de ces mesures sont en liaison avec l'échelle stratigraphique du Carbonifère et permettent de proposer de nouvelles valeurs pour les limites d'étages 5 à 10 Ma plus anciennes que celles préalablement admises: base du Namurien: 326 Ma, base du Westphalien: 315 Ma, base du Stéphanien: 306 Ma, base de l'Autunien: 300 Ma.
Article
Dass. Ausz. 6 S. 8 Würzburg, Naturwiss. F., Diss. v. 21. Juli 1954 (Nicht f. d. Aust.).
Article
Major-, trace- and rare-earth element chemistry studies of metabasite intercalations within different tectonic units of the East Bavarian crystalline basement leads to the following geochemical classification: The flaser amphibolites of the Erbendorf-Vohenstrauss Zone (ZEV) exhibit an enriched, E-MORB- or intraplate-like tholeiitic character, whereas the schistose and striped amphibolites of the ZEV and of the Tirschenreuth-Mahring Zone show N-MORB compositions. The metagabbros of the ZEV are transitional between these two types. The metabasites of the Erbendorf Greenschist Zone are similar to modern island-arc basalts (tholeiitic to calc-alkaline). The Fichtelgebirge crystalline complex contains amphibolites of enriched tholeiitic to alkaline i.e., intraplate character.In most of the investigated metabasites, a post-basaltic/post-gabbroic mobilization of the trace elements cannot be recognized. An exception is Ba which is generally enriched. This may be due to pre-metamorphic hydrothermal alteration processes and/or to a synmetamorphic chemical exchange with adjacent metasediments. The contact-metamorphic overprint of some flaser amphibolites from the ZEV by the intrusion of the Variscan Falkenberg granite led to enrichment in Li, Rb, K and W, a simultaneous depletion in Ca, Sr, Cr and Ni, and a decrease in the K/Rb ratio. Nb, Ce, P, Zr, Ti and V scatter in a much wider range than in the unaffected flaser amphibolites, although with no clear tendency for enrichment or depletion. A mobilization of P and the LREE's in some schistose and striped amphibolites of the ZEV and in the contact-metamorphosed flaser amphibolites is presumably a result of post-granitic hydrothermal alteration which is indicated by enrichment of As as a pathfinder element.
330-320 m.y. ago (Davis and Schreyer
  • Harre
330-320 m.y. ago (Davis and Schreyer, 1962; Harre et al., 1967 (also see this paper, Table 2);
Kbbler and Miiller-Sol-mitts
  • Fischer
Fischer et al., 1968; Gebauer and Grtinenfelder, 1973; Grauert et al., 1974; Kbbler and Miiller-Sol-mitts, 1976b; Schulz-Schmalschlager et al., 1984; Carl et al., 1985; Teufel et al., 1985; Teufel, 1988).
Hornblendealter aus dem ostbayerischen Grundgebirge
  • Fischer
Geologie and Pétrographie des Westteils der Kristallinzone von Erbendorf-Vohenstrauss/Oberpfalz
  • Frank
Gravimétrie Oberpfalz
  • Bücker
Vergleichende U/Pb-und Rb/Sr- Altersbestimmungen im bayerischen Teil des Moldanubikums
  • Gebauer
Zur Stratigraphie des nichtmetamorphen Paläozoikums am Südrand der Münchberger Gneismasse (Blatt 5936 Bad Berneck)
  • Gandl
K-Ar ages of granitic and ectinitic rocks of the Teplá anticlinorium
  • Gottstein
Petrographische Untersuchungen und thermobarometrische Analyse der metamorphen Überprägung in 2 tectonischen Bewegungszonen des nördlichen Oberpfälzer Waldes
  • Kleemann
K/Ar-Mineral- und Rb/Sr-Gesamtgesteinsdatierungen
  • Kreuzer
Zur Lithologie des “Kulms” bei Erbendorf/ Oberpfalz (Bayern)
  • Ludwig
Zum Übergang eines Tonschiefers in die Metamorphose: “Griffelschiefer” im Ordovizium von NE-Bayern
  • Ludwig
Die Eklogitvorkommen des kristallinen Grundgebirges in NE-Bayern. X. Bestehen genetische Beziehungen zwischen Eklogit und Meta-Gabbro innerhalb des Münchberger Gneisgebietes?
  • Matthes
Die Eklogit-vorkommen des kristallinen Grundgebirges in NE-Bayern. IX. Petrographie, Geochemie und Petrogenese der Eklogite des Münchberger Gneisgebietes
  • Matthes
Rb/Sr-Gesamtgesteins-Altersbestimmungen am Weissenstadt-Marktleuthener Porphyrgranit des Fichtelgebirges
  • Lenz
Die kontaktmetamorphe Überprägung basischer kristalliner Schiefer im Kontakthof des Stein-wald-Granits nördlich von Erbendorf in der bayerischen Oberpfalz
  • Matthes
Erläuterungen zur Geologischen Karte 1 : 25000, Blatt 5838/5839 Selb/Schönberg
  • Mielke