European Variscan orogenic evolution as an analogue of Tibetan‐Himalayan orogen: Insights from petrology and numerical modeling

Maierová, Petra; Schulmann, Karel; Lexa, Ondrej; Guillot, Stéphane; Štípská, Pavla; Janoušek, Vojtěch; Čadek, O.

doi:10.1002/2015tc004098

Cited by 36 publications

(21 citation statements)

References 97 publications

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“…It resembles scenarios proposed to explain collisional dynamics of the Variscan belt in the Bohemian Massif (Behr et al, ; Massonne, ) or formation of the Tibetan Plateau (Chemenda et al, ; Hacker et al, ). The common characteristics for both these orogens are the presence of HP felsic granulites and Mg‐K magmas (Maierová et al, ). In the European Variscan belt the felsic HP granulites crosscut the upper plate in the form of domal structures (Schulmann et al, , ), while in central Tibet they occur predominantly as xenoliths trapped by Mg‐K volcanites (e.g., Hacker et al, , ).…”

Section: Discussionmentioning

confidence: 99%

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Relamination Styles in Collisional Orogens

2018

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During continental collision, a part of the lower‐plate material can be subducted, emplaced at the base of the upper plate, and eventually incorporated into its crust. This mechanism of continental‐crust transformation is called relamination, and it has been invoked to explain occurrences of high‐pressure felsic rocks in different structural positions of several orogenic systems. In the present study we reproduced relamination during continental collision in a thermomechanical numerical model. We performed a parametric study and distinguished three main types of evolution regarding the fate of the subducted continental crust: (i) return along the plate interface in a subduction channel or wedge, (ii) flow at the bottom of the upper‐plate lithosphere and subsequent translithospheric exhumation near the arc or in the back‐arc region (“sublithospheric relamination”), and (iii) nearly horizontal flow directly into the upper‐plate crust (“intracrustal relamination”). Sublithospheric relamination is preferred for relatively quick convergence of thin continental plates. An important factor for the development of sublithospheric relamination is melting of the subducted material, which weakens the lithosphere and opens a path for the exhumation of the relaminant. In contrast, a thick and strong overriding plate typically leads to exhumation near the plate interface. If the overriding plate is too thin or weak, intracrustal relamination occurs. We show that each of these evolution types has its counterpart in nature: (i) the Alps and the Caledonides, (ii) the Himalayan‐Tibetan system and the European Variscides, and (iii) pre‐Cambrian ultrahot orogens.

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Section: Discussionmentioning

confidence: 99%

“…Previous tectonic and numerical models for the exhumation of HP rocks in the Bohemian Massif and Tibet focused on crustal deformation (e.g., Beaumont et al, ; Maierová et al, ; Schulmann et al, ). The relaminant, if present, was assumed to flow just underneath the crust from where it vertically exhumed to the middle crust.…”

Section: Discussionmentioning

confidence: 99%

Relamination Styles in Collisional Orogens

2018

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“…Continued underthrusting may then force complete exhumation of a lower crustal dome. Support for this model would include the presence of relaminated low-density felsic lower crust beneath the South Pamir that locally breached midcrustal levels in diapirs ("gravity overturns" of Maierová et al [2016]). Low-density material could have been plated beneath the South Pamir in the form of subduction-accretion wedges (see above).…”

Section: 1002/2017tc004488mentioning

confidence: 99%

Building the Pamir‐Tibet Plateau—Crustal stacking, extensional collapse, and lateral extrusion in the Pamir: 3. Thermobarometry and petrochronology of deep Asian crust

et al. 2017

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Large domes of crystalline, middle to deep crustal rocks of Asian provenance make the Pamir a unique part of the India‐Asia collision. Combined major‐element and trace element thermobarometry, pseudosections, garnet‐zoning deconstruction, and geochronology are used to assess the burial and exhumation history of five of these domes. All domes were buried and heated sufficiently to initiate garnet growth at depths of 15–20 km at 37–27 Ma. The Central Pamir was then heated at ~10–20°C/Myr and buried at 1–2 km/Myr to 600–675°C at depths of 25–35 km by 22–19 Ma. The Shakhdara Dome in the South Pamir was heated at ~20°C/Myr and buried at 2–8 km/Myr to reach 750–800°C at depths of ≥50 km by ~20 Ma. All domes were exhumed at >3 km/Myr to 5–10 km depths and ~300°C by 17–15 Ma. The pressures, temperatures, burial rates, and heating rates are typical of continental collision. Decompression during exhumation outpaced cooling, compatible with tectonic unroofing along mapped large‐scale, normal‐sense shear zones, and with advection of near‐solidus or suprasolidus temperatures into the upper crust, triggering exhumation‐related magmatism. The Shakhdara Dome was exhumed from greater depth than the Central Pamir domes perhaps due to its position farther in the hinterland of the Paleogene retrowedge and to higher heat input following Indian slab breakoff. The large‐scale thickening and coincident ~20 Ma switch to extension throughout a huge area encompassing the Pamir and Karakorum strengthens the idea that the evolution of orogenic plateaux is governed by catastrophic plate‐scale events.

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“…In contrast, based on a different numerical modeling study, Butler et al (2015) argued that melting in subducted crust has only minor, if any effect on exhumation, at least for large UHP terranes, for example the Western Gneiss Region in Norway. However, numerical model results might be biased by the approach chosen to introduce the melt-enhanced weakening (Jamieson and Beaumont, 2011;Labrousse et al, 2015;Butler et al, 2015;Maierová et al, 2016). Furthermore, low resolution of these models (~1 km grid spacing) does not allow simulation of mesoscale to microscale deformation mechanisms coupled with porous melt flow and melt segregation (see Wallner and Schmeling, 2016).…”

Section: Introductionmentioning

confidence: 99%

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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European Variscan orogenic evolution as an analogue of Tibetan‐Himalayan orogen: Insights from petrology and numerical modeling

Abstract: International audienc

Cited by 36 publications

References 97 publications

Relamination Styles in Collisional Orogens

Relamination Styles in Collisional Orogens

Building the Pamir‐Tibet Plateau—Crustal stacking, extensional collapse, and lateral extrusion in the Pamir: 3. Thermobarometry and petrochronology of deep Asian crust

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

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