Anatomy of a diffuse cryptic suture zone: An example from the Bohemian Massif, European Variscides

Schulmann, Karel; Lexa, Ondrej; Janoušek, Vojtěch; Lardeaux, J. M.; Edel, Jean–Bernard

doi:10.1130/g35290.1

Cited by 143 publications

(103 citation statements)

References 18 publications

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“…The studied sequence of anatectic rocks is interpreted to result from continental subduction of felsic crust of the Saxothuringian lower plate beneath the Teplá-Barrandian upper plate (Konopásek and Schulmann, 2005;Schulmann et al, 2014). These reconstructions are compatible with the P-T conditions estimated for the banded orthogneiss (700°-750° at 9-13 kbar), granofels (780° at 15 kbar), and felsic granulite (750-800 °C at 14-16 kbar; Závada et al, 2007;Konopásek et al, 2014;Kotková et al, 1996) that were subducted into mantle depths and rapidly exhumed.…”

Section: Porous Melt Flow and Strain Partitioning During Continental supporting

confidence: 71%

“…The Variscan orogen exposed in the Bohemian massif was recently interpreted in Schulmann et al (2009Schulmann et al ( , 2014 as a deeply eroded Andean-type subduction-collisional orogenic system. This model invokes subduction of the Saxothuringian plate beneath the upper plate represented by the Teplá-Barrandian and Moldanubian crust (Fig.…”

Section: Geological Settingmentioning

confidence: 99%

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Role of strain localization and melt flow on exhumation of deeply subducted continental crust

et al. 2018

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A section of anatectic felsic rocks from a high-pressure (>13 kbar) continental crust (Variscan Bohemian Massif) preserves unique evidence for coupled melt flow and heterogeneous deformation during continental subduction. The section reveals layers of migmatitic granofels interlayered with anatectic banded orthogneiss and other rock types within a single deformation fabric related to the prograde metamorphism. Granofels layers represent high strain zones and have traces of localized porous melt flow that infiltrated the host banded orthogneiss and crystallized granitic melt in the grain interstices. This process is inferred from: (1) gradational contacts between orthogneiss and granofels layers; (2) grain size decrease and crystallographic preferred orientation of major phases, compatible with oriented growth of crystals from interstitial melt during granular flow, accommodated by melt-assisted grain boundary diffusion creep mechanisms; and (3) pressuretemperature equilibria modeling showing that the melts were not generated in situ. We further argue that this porous melt flow, focused along the deformation layering, significantly decreases the strength of the crustal section of the subducting continental lithosphere. As a result, detachment folds develop that decouple the shallower parts of the layered anatectic sequence from the underlying and continuously subducting continental plate, which triggers exhumation of this anatectic sequence.

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Section: Porous Melt Flow and Strain Partitioning During Continental supporting

confidence: 71%

Section: Geological Settingmentioning

confidence: 99%

Role of strain localization and melt flow on exhumation of deeply subducted continental crust

et al. 2018

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“…Models invoked to explain the origin of this magmatic event in the Variscan Belt include: (1) persistent subduction under the Gondwanan margin until ca. 340 Ma (Janoušek and Holub, 2007); (2) slab break-off of the southward-directed subduction of the Rheic oceanic crust (e.g., Kubínová et al, 2017); (3) mantle wedge metasomatism (Finger et al, 2007); (4) late collisional slab sinking and subduction inversion (von Raumer et al, 2014); (5) relamination, rheological weakening, and radiogenic heat (Schulmann et al, 2014); and (6) strike-slip wrenching (Edel, 2001;Rossi et al, 2009). …”

Section: Discussionmentioning

confidence: 99%

Exhuming a cold case: The early granodiorites of the northwest Iberian Variscan belt—A Visean magmatic flare-up?

et al. 2018

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In this study we report laser ablation-inductively coupled plasma-mass spectrometer U-Pb ages of granitoids from the so-called early granodiorites of the northwest Iberian Variscan belt. The U-Pb results attest to significant magmatic activity in Visean time (ca. 347-337 Ma) that generated a hitherto poorly constrained granitoid suite in the northwest Iberian tract of the western European Variscan belt realm. This early Carboniferous suite (ECS) is mainly composed of peraluminous cold and hot crustal granodiorites and monzogranites with minor associated mafic rocks that attest to minor involvement of mantle melting. Based on the geochronological and geochemical data, we compare the Visean granitoids with younger Variscan granitoids in northwest Iberia and, in view of the tectonothermal scenarios of the Variscan collision in northwest Iberia, propose a model for the genesis of the ECS in northwest Iberia that involves rapid melting upon fast exhumation of the thickened Gondwanan crust in the course of the protracted Variscan collision.

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“…This led to extrusion of the lower crust and to the activation of the Bohemian Shear Zone between 337 and 343 Ma. Schulmann et al (2014) suggest that the convergence of two constraining domains of lithosphere led to the subduction of a felsic crust together with (ultra) K plutonic rocks and coeval lamprophyres forced by gravitational instabilities. Subsequently, a so-called cryptic suture zone, a wide zone of mixed materials from the lower and upper domains form a hybrid continental crust.…”

Section: Geological Settingmentioning

confidence: 97%

Variscan potassic dyke magmatism of durbachitic affinity at the southern end of the Bohemian Massif (Lower Austria)

Zeitlhofer

Grasemann

Petrakakis

2015

Int J Earth Sci (Geol Rundsch)

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an Rb-Sr age of c. 318 Ma, interpreted as a deformation age during extensional tectonics. We propose a large-scale extensional regime at c. 320 Ma in the Strudengau area, accompanied by plutonism of fractionated magmas of syncollisional mantle-derived sources, mixed with crustal components. This geodynamic setting is comparable to other areas in the Variscan belt documenting an orogenic wide extension by the end of the Carboniferous.

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Anatomy of a diffuse cryptic suture zone: An example from the Bohemian Massif, European Variscides

Cited by 143 publications

References 18 publications

Role of strain localization and melt flow on exhumation of deeply subducted continental crust

Role of strain localization and melt flow on exhumation of deeply subducted continental crust

Exhuming a cold case: The early granodiorites of the northwest Iberian Variscan belt—A Visean magmatic flare-up?

Variscan potassic dyke magmatism of durbachitic affinity at the southern end of the Bohemian Massif (Lower Austria)

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